2014 Compliance Recertification Application (CRA-2014)
         Compliance Application Review Document (CARD Section 194.24)
                            Waste Characterization
24.0 Background (194.24(a))

	Section 194.24, waste characterization, generally requires DOE to identify, quantify and track the chemical, radiological, and physical components of the waste destined for disposal at WIPP that can influence disposal system performance.  Much of the waste information and waste estimates remain similar through time, but DOE may add waste and withdraw waste from the inventory.  It is a dynamic inventory and EPA expects changes through the years.  However, it is incumbent upon DOE to include the latest information on the inventory estimate in the performance assessment.  After the 2004 Compliance Recertification Application, DOE began to update the inventory on an annual basis.

      Section 194.24 (a) presents the waste inventory reporting requirements that DOE must meet to ensure that sufficient information is available for use in the WIPP performance assessment (PA).

24.1 Requirement (194.24(a))

	(a) "Any compliance application shall describe the chemical, radiological and physical composition of all existing waste proposed for disposal in the disposal system.  To the extent practicable, any compliance application shall also describe the chemical, radiological and physical composition of to-be-generated waste proposed for disposal in the disposal system.  These descriptions shall include a list of the waste components and their approximate quantities in the waste.  This list may be derived from process knowledge, current non-destructive examination/assay, or other information and methods."

24.1.1   1998 Certification Decision (194.24(a))

	To meet the requirements of Section 194.24(a), EPA expected DOE's Compliance Certification Application (CCA) to provide a description of the existing waste, list approximate quantities of waste components in each description, and provide similar descriptions for to-be-generated waste, to the extent practicable.

	DOE provided the required information on existing waste (35% of the total WIPP inventory) by combining similar waste streams into waste stream profiles.  The waste stream profiles contained information in the waste material parameters, or components that could affect repository performance.  For to-be-generated waste (65% of the total WIPP inventory), DOE extrapolated (or scaled) information from the existing waste streams to determine the future amount of waste.  DOE described the waste in Volume 1 and Appendix BIR of the CCA.

	EPA reviewed the information provided and determined that DOE's waste stream profiles contained the appropriate specific information on the components and their approximate quantities in the waste.  Therefore, EPA found DOE in compliance with Section 194.24(a) (CCA CARD 24).

	A complete description of EPA's 1998 Certification Decision for Section 194.24(a) can be obtained from Docket A-93-02, Items V-A-1 and V-B-2.

24.1.2 Changes in the 2004 Compliance Recertification Applications (194.24(a))

      To meet the requirements of Section 194.24(a), DOE described and categorized the entirety of TRU waste that is currently emplaced in WIPP and the waste that exists at various DOE facilities.   Since the first emplacement of waste in 1999, DOE has tracked the waste emplaced at WIPP using the WIPP Waste Information System (WWIS).  For the waste that is stored or to-be-generated at the waste generator sites, DOE developed a descriptive methodology for grouping waste information obtained from each generator site.  For the 2004 CRA, DOE initiated a complex-wide data call in which DOE's Carlsbad Field Office (CBFO) asked every TRU waste generator site to update the CCA waste profile forms describing the physical, chemical, and radiological constituents in each waste stream that generates or generated TRU waste at that site. This data call reflected the disposal intentions of the waste generator sites as of September 30, 2002.  DOE representatives examined the information, clarified questions and then validated the waste stream profile information.  This information was synthesized across the waste generator sites and then prepared for input into performance assessment by scaling the inventory and other data reduction actions (e.g., decaying to 2033).  This process is captured in the flowchart in Figure 24-1 (Docket A-98-49, Item II-B2-60).

	The details of the inventory are presented in 2004 CRA Chapter 4 Volume 1 and 2004 CRA Appendix TRU-WASTE.  Tables 2004 CRA Appendix TRU-WASTE 1-5, present the most relevant information on the important aspects of the inventory used for the 2004 CRA.

      During EPA's review of the PA submitted in the 2004 CRA, EPA questioned aspects of the waste inventory DOE was reporting for recertification.  EPA's requests for additional information and DOE's responses can be found in EPA's E-Docket (Federal Docket Management System [FDMS] Docket ID No. EPA-HQ-OAR-2004-0025).

       EPA directed DOE to conduct a new performance assessment for recertification to incorporate inventory changes as well as some other technical changes (EPA Letter, Docket A-98-49, Item II-B3-80). This new performance assessment is now called the 2004 Performance Assessment Baseline Calculations or 2004 PABC.  The new inventory component and radiological estimates for the PABC are summarized in TRU Waste Inventory for the 2004 Compliance Recertification Application Performance Assessment Baseline Calculation, Sandia National Laboratories, ERMS 541118, September, 2005, hereafter referred to as the "PABC Inventory Report" (Docket A-98-49, Item II-B2-60).

	The chemical, physical, and radiological inventory was grouped by DOE and developed in detail from the waste stream profiles from each of the TRU waste generator and/or storage sites.  Waste groupings (other than contact handled and remote handled designations) by DOE were based on the chemical and physical aspects of the waste, not the radiological content of the waste (CCA Appendix BIR).  However, the radiological constituents were identified and quantified (in Ci/m[3] for each waste stream) on each waste profile form, and information from the forms was used by DOE to develop the radiological inventory for the WIPP.  The CCA approach was also used for the PABC.  Table 14 of the PABC Inventory Report shows the radiological constituents used for the PABC, including the inventory at the estimated time of disposal (Curie amounts of each radionuclide decayed to the year 2033), and estimated EPA units (activities normalized according to the 40 CFR 191 release limits) for each radionuclide.
Figure 24-1 Process for Preparing the CRA-2004 TRU Waste Inventory (Source:  PABC Inventory Report, Docket A-98-49, Item II-B2-60, September 2005)

	Each WIPP Waste Profile contains information on the physical and chemical waste components (identified as Waste Material Parameters (WMP's) for DOE purposes), as well as radiological waste components, that DOE believes could affect the performance of the repository.  DOE's waste material parameters are presented as density values for use in performance assessment.  These density values are calculated by multiplying the average density of individual waste streams from a given waste form by the volume of the TWBIR waste stream and then the total volume of the final waste form.

      The approximate maximum, average, and minimum densities for twelve (12) of DOE's waste material parameters were calculated, including iron based metals/alloys, aluminum based metals/alloys, other metal/alloys, other inorganic materials, vitrified materials, cellulosics, rubber, plastics, solidified inorganic matrix, solidified organic matrix, solidified cement, and soils (PABC Inventory Report, Table 9).  WIPP Waste Profiles contain information on the WMPs, i.e., components that DOE determined to have the potential to impact repository performance.  DOE identified the quantity of physical waste components such as cellulosic material, plastic, rubber, etc., in the 2004 PABC Inventory Report.  Tables 9 and 10 of the 2004 PABC Inventory Report show the anticipated non-radioactive TRU waste inventory for the WIPP for the CCA the CRA and the PABC.

	Also, in accordance with 40 CFR 194.24(a), DOE's waste profiles contain specific information on the species and quantities of individual radioisotopes in the waste.

Inventory Description
	DOE indicated that to-be-generated waste will be included in those waste streams and final waste forms currently identified at DOE sites (2004 CRA Chapter 4, Section 4.1.3).  Therefore, the waste stream descriptors for existing waste also apply to to-be-generated waste.  Existing waste stream information was used by DOE in its description of to-be-generated waste.

	DOE described its contact-handled (CH) and remote-handled (RH) inventory as "stored," "emplaced," and "projected" or "anticipated."   The stored inventory is generally equivalent to existing waste at the sites, and projected waste is generally equivalent to to-be-generated waste (2004 CRA Appendix DATA, Attachment F).  Emplaced waste is waste that has been put underground at WIPP.  The anticipated inventory is the sum of the emplaced, stored and projected inventories (2004 PABC Inventory Report section 4.1.3).  Table 4 of the 2004 PABC Inventory Report lists the volumes of emplaced CH-TRU waste as of September 30, 2002 (the cutoff for inclusion in the 2004 CRA performance assessment) and August 1, 2005.  Table 5 of the same report lists the stored and projected CH-TRU waste estimates used for the CCA, 2004 CRA PA, and the 2004 PABC.  The projected inventory information was derived from each generator site from the waste stream profile forms, and reflects the site's best determination of the waste expected to be generated.

	DOE's estimates indicate that the total expected inventory volume for CH-TRU waste will not reach the maximum disposal capacity of the WIPP for CH-TRU (approximately 168,500 m[3] or 5,950,000 ft[3]) (2004 CRA Chapter 4.1.3; 2004 PABC Inventory Report, section 4.1.4, p.27).  DOE employed a scaling approach to project the impacts of a full repository.  The CRA-2004 estimate of waste for disposal at WIPP is 145,000 m[3].  DOE developed a scaling factor based upon the approximately 23,500 m[3] of projected CH-TRU inventory it expects to be generated, as DOE believed that any new waste generated to "fill" the outstanding WIPP space would probably be more similar to the projected rather than existing waste inventory.  This scaled CH-TRU inventory was described by DOE in TRU Waste Baseline Inventory Report (TWBIR), Revision 3 and was based on the projected TRU waste inventory (e.g., waste components, quantity, types of waste, species and quantity of radionuclides).

	As reported in the 2004 PABC Inventory Report, the scaling factor calculated by DOE for CH-TRU waste is 1.48 in the 2004 PABC.  This factor is used in the following formula to project the makeup of the disposal inventory volume (m[3]) according to the LWA design limitations:

Emplaced Inventory + Stored Inventory + (Projected Inventory x 1.48) = PABC Disposal Inventory

	Unlike in the CCA, the 2004 CRA used this scaling methodology on RH-TRU waste; however, the RH inventory was scaled down.  This was necessary because DOE has reported more RH-TRU inventory than there is capacity for as defined in the WIPP Land Withdrawal Act (LWA) (approximately 7,079 m3 or 250,000 ft[3]).  The scaling factor has changed considerably between the 2004 CRA and the 2004 PABC calculations due to changes in estimates in Hanford's RH-TRU inventory.  In the 2004 CRA the scaling factor was 0.172 and in the PABC it is 0.861, reflecting the lesser amount of RH-TRU expected from Hanford because of a double counting error.  The RH-TRU inventory is calculated using a similar equation for the CH-TRU disposal inventory calculation.

Number of Curies
	The total activity of radionuclides expected to be placed in WIPP has decreased from the CCA estimate of 3.44 million curies to 2.32 million curies in the 2004 PABC inventory estimate (2004 PABC Inventory Report Section 4.4, p. 36).  Table 14 of the 2004 PABC Inventory Report lists the activities by radionuclide for the CCA PA, the 2004 CRA PA, and the 2004 PABC.

New Inventory Items Since 1998:  INL Buried Waste
	In the 2004 CRA documentation, DOE designated pre-1970 buried waste at INL as non-WIPP TRU waste (Annex I of CRA-2004 Appendix Data Attachment F).  As a result of an April, 2003 Federal District Court judgment against DOE on the buried waste, DOE decided to include the INL pre-1970 buried waste in the 2004 PABC calculations (2004 PABC Inventory Report section 3.2, p. 21).  The 2004 PABC inventory report estimated 17,998 m[3] of TRU waste in five waste streams from the pre-1970 buried waste.

New Inventory Items Since 1998:  Super-compacted Waste
      In December 2002, DOE requested EPA's approval to dispose of compressed or super compacted waste from the Idaho National Laboratory's (INL) Advanced Mixed Waste Treatment Facility (AMWTF).  In DOE's waste inventory for the 2004 recertification, this super-compacted waste (waste stream IN-BN-510) accounts for approximately 20,000 m[3] of the inventory.  This waste is described as more rigid than typical waste and has a much higher content of cellulosics, plastics and rubber materials (CPR) than other waste in the CCA inventory.

	DOE conducted an extensive analysis of the waste at the direction of EPA (Docket A-98-49, Item II-B3-64) and concluded that the super-compacted waste would act similarly enough to un-compacted waste that it could be considered within the existing waste envelope and performance assessment.  In March 2004, EPA determined that super-compacted waste could be disposed of at WIPP and that the characteristics of the waste were adequately reflected in the existing performance assessment (Docket A-98-49, Item II-B3-68).  Prior to the shipment of super-compacted waste, EPA conducted a waste characterization inspection to ensure that DOE was able to adequately characterize and track the super-compacted waste (Docket A-98-49, Item II-A4-53).  EPA gave its approval to dispose of super-compacted waste in May 2005.  This waste is included in the 2004 PABC waste inventory estimate (Docket A-98-49, Item II-B3-68).

New Inventory Items Since 1998:  Hanford Tank Waste
	DOE's CRA-2004 inventory included to-be-generated waste from 12 of the 177 tanks at the Hanford site.  These 12 tanks include four waste streams.  These waste streams and their corresponding tanks and waste generating process are provided in Table 24-1 of this CARD.  DOE's documentation states that although these 12 tanks have been managed as high-level waste (HLW), these tanks actually contain waste from transuranic processes (Docket A-98-49, Item II-B2-47) and are therefore eligible for disposal at WIPP.  DOE's documentation provides a technical and regulatory basis for DOE's-Office of River Protection (ORP) determination that 9 of the tanks are TRU waste due to waste origin and confirmed by radionuclide content analysis.  This waste will be contact-handled, and has yet to be removed from the tanks.

	For the other tanks in the RH waste streams (see Table 24-1), DOE (Docket A-98-49, Item II-B2-47) discusses why they believe that this tank waste is also TRU waste and will be acceptable for disposal at WIPP after the waste is removed from the tanks and treated to meet the WIPP Waste Acceptance Criteria.  DOE states (Docket A-98-49, Item II-B2-47; Enclosure 1, p. 11) that "Two of the double-shell tanks (DSTs) identified in the CRA inventory update, tanks AW-103 and AW-105, received coating removal waste from dissolution of zirconium clad SNF [Spent Nuclear Fuel]" in the PUREX process.  DOE concludes (Ibid, p. 13) that, "the cladding removal process step did not create HLW because it only dissolved the zirconium cladding, leaving the SNF intact.  The cladding removal waste originated prior to the SNF being dissolved and reprocessed.  The NWPA defines HLW as `...the highly radioactive material resulting from the reprocessing of spent nuclear fuel...' Since SNF was intact during the cladding removal process, reprocessing had not occurred, and therefore, the cladding removal waste is excluded from the HLW definition."

	DOE states (Docket A-98-49, Item II-B2-50, p. 15) that "One of the underground storage tanks at the Hanford Site that received PFP waste was DST [double-shelled tank] SY-102.  DOE also states that the PFP [Plutonium Finishing Plant] sludge in tank SY-102 is not HLW because it is not the highly radioactive waste material from the reprocessing of spent nuclear fuel, including liquid waste produced directly in the reprocessing and any solid materials derived from such liquid waste that contains fission products in sufficient concentrations.  The PFP received plutonium materials product and converted it to forms that were used to fabricate nuclear weapons or for other purposes.  The PFP did not receive any SNF or HLW. Therefore, the waste from the PFP sludge is not HLW (Docket A-98-49, Item II-B2-50).  DOE concluded that in addition to this information, the treatment of the waste will make it suitable for disposal at WIPP.  This waste is included in the 2004 PABC waste inventory estimate.

New Inventory Items Since 1998:  Hanford Waste from K-Basin
	DOE recertification waste inventory also included two waste streams, RL-W445 and RL-W446, consisting of ~50 m[3] of sludge from the Hanford K-East and K-West Basins.  This waste was in pools of water used to store irradiated fuel prior to SNF processing (Docket A-98-49, Item II-B2-47; Enclosure 2, p. 1).  While intended to be temporary, the storage lasted for over 20 years. Furthermore, "over the lifetime of these K-West and K-East Basins, debris, silt, sand, and material from operations resulted in the formation of sludge that accumulated in the bottom of these basins.  In addition, the extended storage of the irradiated fuel resulted in corrosion of the fuel cladding and the storage canisters, especially in the K-East Basin, where the fuel was exposed directly to the storage water" (Ibid).

	DOE concludes "that this sludge does not meet the definition of high level waste (HLW) or SNF, and if properly processed, will meet the disposal requirements for transuranic waste, and thus be eligible for disposal at WIPP" (Ibid).  This waste is included in the 2004 PABC waste inventory estimate.

Container Types
	While the waste containers are not used directly in the performance assessment, knowing the type of container is important in order estimate the amounts of CPR and metals in WIPP (2004 PABC Inventory Report, section 4.2, p. 30).  Container types new to the 2004 PABC inventory include: ten-drum overpacks (TDOPs), 5x5x8 boxes and 100-gallon drums (Ibid).  In addition, DOE used pipe overpacks within drums to contain high radioactivity salts from Rocky Flats Environmental Technology Site (RFETS).  The TDOPs are used primarily at INL and SRS, the 100 gallon drums are used at INL for the super-compacted waste, and the 5x5x8 boxes are in the SRS inventory.  Container types are considered in the 2004 PABC inventory development process.

Organic Ligands
	A ligand is an ion or molecule that binds to a metal.  At WIPP the importance of ligands is that they could bind to the radionuclides, and potentially increase the solubility of those radionuclides. Organic ligands which attach to the cation at more than one location (by different atoms within the structure of the ligand) are called chelating groups and the complex thus formed is called a chelate.  Many synthetic compounds, such as EDTA (ethylenediaminetetraacetic acid) form chelates. Citrate is an example of a natural organic compound which forms chelates with metal ions using its three carboxylic acid groups.

	In the CCA, DOE's analysis used low ionic strength calculations to estimate the potential effect of organic ligands because the FMT (Fracture-Matrix Transport) code thermodynamic database was not complete at the time.  Extrapolating to high ionic strength conditions, DOE identified that the EDTA would preferentially bind to transition metals (CCA Appendix SOTERM Section 5).  EPA agreed with DOE that chelating agents (organic ligands) will bind to metals other than actinides.  In addition, EPA's sensitivity analysis done at the time of the CCA indicated that chelating agents were not important to performance and that the ligands did not appear to have a strong effect on the aqueous speciation of actinides because of competition with major ions that are present at much higher concentrations (CCA CARD 24, 24.C.5, p. 24-40 and 24-41).

	Between 1996 and the 2004 CRA, both stability constants and Pitzer parameters have been determined, allowing inclusion of the organic ligands in the FMT speciation and solubility calculations (Docket A-98-49, Item II-B2-39).  Four organic ligands were included in FMT calculations of actinide solubilities: acetate, citrate, ethylenediaminetetraacetic acid (EDTA), and oxalate.

	DOE (2004 Attachment SOTERM (Section 5.0, p. 42)) calculated the solubilities of the +III, +IV, and +V actinides for the CRA-2004 PA using FMT, an updated thermodynamic database, and concentrations of acetate, citrate, EDTA, and oxalate updated for the CRA (Docket A-98-49, Item II-B1-3, Technical Support Document for Section 194.24).  DOE believed that "the results of the FMT calculations for the CRA-2004 PA demonstrate that acetate, citrate, EDTA, and oxalate will not form complexes with the +III and +IV actinides to a significant extent under expected WIPP conditions, and thus will not affect the +III and +IV actinide solubilities significantly" (see Docket A-98-49, Item II-B1-3 for details).

	A complete description of EPA's 1998 Certification Decision for Section 194.24(a) can be obtained from EPA Air Docket, A-93-02, Items V-A-1 and V-B-2.

24.1.3 Evaluation of Compliance for 2004 Recertification (194.24(a))

	EPA reviewed the 2004 CRA and supplemental information to determine whether it provided a sufficiently complete description of the chemical, radiological and physical composition of the emplaced, existing and to-be-generated waste proposed for disposal in the WIPP.  EPA also reviewed DOE's description of the approximate quantities of waste components (for both existing and to-be-generated waste).  EPA considered whether DOE's waste descriptions were of sufficient detail to enable EPA to conclude that DOE did not overlook any component that is present in transuranic waste and has significant potential to influence releases of radionuclides.

Chemical, Physical, and Radiological Description of Existing Waste
	Descriptions of the chemical, radiological, and physical components of the waste were thoroughly documented in 2004 CRA and supporting documents.  This information was collected using similar methods as during the CCA and the process used was reasonable.  EPA also conducted several visits to the waste generator sites to better understand the waste estimation process (Docket A-98-49, Items II-B3-75, II-B3-86, and II-B3-87).

	EPA concluded on the basis of this information that the 2004 CRA and supplemental information adequately described the chemical, radiological, and physical characteristics of each waste stream proposed for disposal at the WIPP.  EPA further concluded that the information presented by DOE in the 2004 CRA provided adequate characterization of existing WIPP waste for use in PA.

	EPA noted the following changes in the waste:  DOE listed the to-be-generated (projected) waste in waste profile tables in 2004 CRA Appendix DATA, Attachment F.  The projected waste is categorized similarly to existing waste (e.g., heterogeneous debris, filter material, soil).  The amounts are ultimately expressed in density terms (kg/m[3]) for performance assessment purposes and the projected waste is a minority of the estimated inventory.  These factors would limit the potential effects of differences in the current estimates for projected waste and future actual amounts.

	EPA concluded that DOE's development of the disposal inventory was sufficient for PA purposes.  EPA agreed with DOE that the use of projected waste inventory for scaling the CH WIPP inventory to meet the total WIPP capacity was appropriate.  DOE's use of the inventory scaling process is similar to that used in the CCA and is adequate for projecting inventory estimates.

Waste Forms and Packaging:  Super-compacted Waste
	EPA approved the disposal of super-compacted waste from INL at WIPP (Docket A-98-49, Item II-B3-68).  DOE's 2004 CRA adequately characterized and considered super-compacted waste in the recertification inventory.

Waste Forms and Packaging:  Container Types
	 The important aspect of the waste containers, for inventory purposes, is the amount of metal that they contain. The amount of metal required in the repository is minimum limit.  DOE's assortment of containers was demonstrated to meet the minimum metal limit regardless of the container type, since all are metal containers. EPA did have a concern about the impact of pipe overpacks, but DOE included an analysis of the pipe overpack in the compressed waste analysis and found that the pipe overpack properties were also within that of the existing waste envelope (Docket A-98-49, Items II-B2-31, II-B2-32, and II-B3-68).  EPA found the inclusion of container types to be reasonable.

Waste Forms and Packaging:  Inclusion of Waste Packaging in Inventory
      During the initial review of the 2004 recertification application, EPA found that DOE did not include emplacement materials in the CRA-2004 PA calculations (Docket A-98-49, Item II-B3-73).  These materials, which consist primarily of plastics and to lesser extent cellulosics, could contribute to gas generation.  DOE stated (Docket A-98-49, Item II-B2-34) that this material accounts for only 12.7% increase in CPR if it is included in the PA and that there would be no effect on compliance if it were included in the PA.  However, DOE did include the additional emplacement material volume and mass in the 2004 PABC (2004 PABC Inventory Report section 1.3.3, p. 11), thus the emplacement materials were reflected in the release estimates.  For the 2004 PABC, the inclusion of waste packaging caused the CPR inventory to increase above DOE's stated limit.  This was discussed further in CARD 24, Section 24(c)(1) and 24(e)(1) (e)(2).  The 2004 PABC showed that WIPP still complied with the new CPR amounts, thus the use of increased CPR amounts is adequate, and the amount used in the 2004 PABC established a new limit.

Number of Curies, Waste Streams and Volume
	DOE estimated the number of curies in the inventory on a site by site, waste stream by waste stream level using a reasonable process.  EPA requires that DOE produce a "list of the waste components and their approximate quantities."  EPA reviewed the estimate in CRA-2004 Chapter 4, Appendix TRU-WASTE, and the TRU Waste Inventory Baseline (TWIB) database and found these materials contained sufficiently specific information on the species and quantities of individual radioisotopes in the waste. This was in addition to waste that had been characterized and emplaced in WIPP.  Thus, the inventory was based on more information than was available in the CCA, which EPA approved.

      In addition to the radioisotope inventory information, DOE also provided sufficient information on the waste components with descriptions in the following documents:  2004 CRA Volume 1, Chapter 4, 2004 CRA Appendix DATA Attachment D, 2004 CRA Appendix DATA Attachment E, 2004 CRA Appendix DATA Attachment F Annex A-K, 2004 CRA Attachment F: Transuranic Waste Inventory Update Report, 2003, to Appendix DATA, 2004 CRA Appendix DATA Attachment H, 2004 CRA Appendix TRU WASTE, and PABC Inventory Report.

      Through the scaling process, DOE projects future waste amounts based on existing waste amounts.  EPA acknowledged that may not be entirely realistic, however, it is a rational method for predicting future unknown waste, which at the time of the 2004 CRA was projected to account for ~15% of total waste by volume.

	DOE identified a problem with the estimate of the RH waste, in which the Hanford site "double-counted" certain waste.  The result of this mistake had little effect because the RH waste volume has a small inventory limit and DOE had more RH waste inventory than legal capacity even without the mistake.  DOE caught this error and incorporated an updated scaling factor in the 2004 PABC.  EPA found that DOE adequately updated the CRA 2004 inventory.

Organic Ligands
	The Agency reviewed the updated calculations related to the effect of organic ligands on actinide solubility and determined that organic ligands are potentially important (Docket A-98-49, Item II-B1-3).  EPA found that DOE needed to provide additional information on findings from the literature since the original certification and the effect of organic ligands on the actinide +V and +VI oxidation states (Docket A-98-49, Item II-B3-74).  DOE responded (Docket A-98-49, Item II-B2-39) that while organic ligands greatly affect the solubility of +V oxidation state actinides, neptunium is the only actinide expected to be in the +V oxidation state.  EPA agreed with DOE that this was of low significance because the neptunium inventory is too low to significantly contribute to radionuclide releases.  Organic ligands had a moderate effect on the +III and +IV actinide solubilities.  DOE did include the effects of solubility of organic ligands in the 2004 PABC, and with the 2004 CRA and supplemental information, therefore, EPA found that DOE appropriately included organic ligands in the 2004 PABC (see Docket A-98-49, Item II-B1-16).

Hanford Waste
	In the 2004 CRA, DOE identified that it included waste from 12 tanks from Hanford (see Table 24-1 for a summary of the tank waste).  This included 9 tanks of CH waste and 3 tanks of RH waste.  The volume of the CH waste was estimated to be ~3,932 m[3] (~2% of the total CH inventory and ~2% of the total inventory) and the RH waste volume was estimated to be ~4,469 m[3] (~63% of total RH waste, ~2.5% of the total inventory).  The issue for this waste was whether the process by which it was created could be considered to be the reprocessing of spent nuclear fuel.  DOE stated that although all the tanks were previously managed as high-level waste (HLW), some tanks could be considered TRU waste.  HLW by law cannot be disposed of at WIPP.  DOE included the waste from the 12 tanks in the 2004 CRA PA and the 2004 PABC. EPA noted that two tanks (SY-102 and AW-103) had "non-TRU waste supernatant solutions atop" the sludges in the tanks that DOE considered to be TRU waste.

Table 24-1 Hanford Tank Waste For Which Information was Requested in Docket A-98-49, Item II-B3-78 (Waste Stream Information From CRA Appendix DATA, Attachment F, Annex J Waste Profile Sheets and the September 2004 Hanford Meeting)
Waste Stream (Type)
Tank(s)
Volume (m[3])
Process (resulted in "solidified aqueous waste slurry")
RP-W013 (RH)
SY-102
  525
Plutonium Finishing Plant
RP-W016 (RH)
AW-103, AW-105
3944
PUREX TRU Cladding Removal
RP-W754 (CH)
B 201-204 and
T 201-204 series tanks
1484
224 Solidified Inorganic Waste
RP-W755 (CH)
T-111
2448
Bismuth Phosphate Process TRU Solids

(RH) = Remote Handled waste
(CH) = Contact Handled waste

	DOE provided additional information on the Hanford tank waste indicating that the waste would be treated and and would eventually meet the WIPP waste acceptance criteria (Air Docket A-98-49, Items II-B2-47 and II-B2-50).  DOE stated that tank waste that could eventually be disposed of at WIPP either was TRU waste or would be TRU waste after treatment.  DOE also stated that the tank waste had not been explicitly designated as HLW, but rather managed as HLW in accordance with their radioactive waste management procedures.

	DOE provided information stating that the waste in question would be processed to remove any high-level waste, to the extent practical, in its preparation to meet the WIPP waste acceptance criteria.  EPA allowed this waste to be included in the performance assessment inventory for recertification.  By so including it, DOE demonstrated that with or without the Hanford tank waste, WIPP would continue to comply with EPA's disposal regulations.  The Agency believes that this is a conservative approach to the performance assessment of the WIPP repository because a broad inventory of waste is being considered.  Inclusion of a waste stream in the performance assessment of the facility does not imply or otherwise provide for EPA's approval of that waste for disposal at WIPP.  Before any waste can be shipped to WIPP, DOE must demonstrate during characterization that the waste is, in fact, TRU waste that can legally go to WIPP.

	Public comments stated that the tank waste is high level waste, and therefore not eligible for disposal at WIPP.  Public comments requested that the tank waste be removed from the WIPP recertification inventory, or if the tanks were to remain in the inventory, that EPA conduct a rulemaking to consider the tank waste for disposal at WIPP.

	EPA does not make waste determinations.  DOE is responsible for making waste determinations, classifications, or reclassifications.  In recognition of the public's concern about the possible future designation of the Hanford tank waste as TRU waste, DOE has proposed a process for developing or changing determinations for waste such as the Hanford tank waste.  In a February 2006 letter to EPA, DOE proposed a process (Air Docket A-98-49, Item II-B2-57) for the evaluation of tank waste that includes multiple opportunities for public input prior to the request to EPA for disposal at WIPP.  The Agency considered it appropriate for DOE to conduct a public process that would determine the designation or classification of waste prior to requesting EPA's approval for disposal at WIPP.

	The Agency's process to ensure that waste disposed of at WIPP is TRU waste may be found in the requirements listed at 40 CFR Part 194.8, 194.22, and 194.24.  The first step in this process is DOE's official request to dispose of TRU waste at WIPP from one of the waste generator sites.  Once EPA receives all required information and documentation, the Agency then inspects waste characterization activities at a waste generator site to ensure that the site has the technical ability to adequately characterize and track TRU waste.  Confirmation of waste designation is then completed through the waste characterization process at the site.  EPA believes that it currently has an adequate process in place for evaluating any DOE requests for approval of waste for disposal at WIPP.  The Agency did not find that it was necessary to conduct a rulemaking for certain waste streams.

	Waste that is not designated as TRU waste will not be considered for disposal at WIPP by EPA.  The Agency agreed with commenters that the LWA does not provide for waste determinations to be made during recertification.  Prior to disposal at WIPP, EPA will ensure that all waste meets the legal and technical requirements for disposal.  Just because waste is included in the WIPP waste inventory, does not mean that DOE will necessarily seek to ship it to WIPP or that EPA will approve it for disposal at WIPP.  Before any waste is approved to be shipped or disposed of at WIPP, EPA ensures that the waste meets the waste acceptance criteria for WIPP and that DOE can characterize and track the waste.

K-Basin Waste
	The sludges from the K-Basin storage pools consist of debris, silt, sand, and material from operations of the pools at Hanford. The 50.4 m[3] of sludges are contaminated with radionuclides associated with spent nuclear fuel that was exposed to water in the pools.  DOE believes that the radioactive contamination in the sludges is primarily from corrosion and chemical processes that could not be considered reprocessing.  DOE identified six sludges from different sections of the K-Basin. For five of the six sludges, the information provided by DOE (Docket A-98-49, Item II-B2-47; Enclosure 2, Table 2) appeared to support the contention that this waste is different from spent nuclear fuel (SNF).  SNF is prohibited by law from disposal at WIPP.  When compared to the other sludges, the sixth sludge (Knock-Out Pot Sludge) exhibits different radiological characteristics -- estimated higher radioactivity that is more similar to SNF than the other sludges.  However, its physical properties are similar to other sludges, the volume is only 0.4 m3 (with a potential to expand to 7.5 m[3]), and DOE plans to remove particles greater than (1/4) inch, eliminating the greatest radioactivity.  At the time of the 2004 CRA, DOE had performed limited measurements of the Knock-Out Pot Sludge (Docket A-98-49, Item II-B2-50), so its actual characteristics were not known with certainty.  EPA allowed this waste in the PA inventory, due to its similarity to other WIPP-bound waste, low volume, and the fact DOE must first process and characterize before it goes to WIPP, in order to demonstrate that the waste meets the technical and legal requirements for disposal.

INL Waste
	Pre-1970 buried waste, included in the 2004 PABC, was found as waste stream IN-Z001 in Annex I of Appendix DATA 2004 Attachment F.  It was designated as non-WIPP TRU waste, but DOE decided to include it in the 2004 PABC because of a 2003 judgment against DOE related to its removal at INL.  This waste was not included in the 2004 CRA PA because the court judgment came after the September 30, 2002 cutoff date for inventory development (see the 2004 PABC Inventory Report and Inventory Data Change Addition Control Form, Docket A-98-49, Item B2-61).  This waste appeared to be similar to other WIPP waste streams, but EPA again indicated that it must still meet the WIPP waste acceptance criteria, and remained subject to EPA's inspection and approval process prior to disposal at WIPP.

Other Issues
	DOE identified and corrected one error between the 2004 CRA PA and the 2004 PABC, the LANL CH-waste stream LA-TA-55-48.  This waste stream was a low volume, high radioactive waste stream that skewed the results of the PA CCDFs upward.  Upon further review, DOE identified that this waste stream was mischaracterized; the plutonium fissile gram equivalent (FGE) was greater than shipping requirements allowed (Docket A-98-49, Item II-B2-62).  DOE re-evaluated the waste stream, and modified the waste stream radioactivity and volume for the 2004 PABC.  Since this was an estimate and the waste would be fully characterized before going to WIPP, EPA found that the waste stream correction was reasonable.

	Commenters (Docket A-98-49, Item II-B3-77) pointed out that the radionuclide values were wrong for K-Basin sludge waste streams (RL-445 and RL-446).  DOE reviewed the information and lowered the [90]Y and [137m]Ba concentrations by about 50% for the 2004 PABC (Docket A-98-49, Item II-B2-60).  Again EPA found that this was an appropriate change and would be verified during the characterization process.

24.1.4 2004 Recertification Decision (194.24(a))

	Based on a review and evaluation of the 2004 CRA and supplemental information provided by DOE (FDMS Docket ID No. EPA-HQ-OAR-2004-0025, Air Docket A-98-49), an assessment of the changes since the 1998 Certification Decision, in this CARD and in technical support documents for this section (Docket A-98-49, Items II-B1-3 and II-B1-9, II-B1-16), and the consideration of public comments, EPA determined that DOE continued to comply with the requirements of 194.24(a).

24.1.5 Changes in the 2009 Compliance Recertification Applications (194.24(a))

      To meet the requirements of Section 194.24(a), DOE continues to describe and categorize the entirety of TRU waste that is emplaced in WIPP and exists at various DOE facilities.  Since the first emplacement of waste in 1999, DOE has tracked the waste emplaced at WIPP using the WIPP Waste Information System (WWIS).  For the waste that is stored or to-be-generated at the waste generator sites, DOE developed a descriptive methodology for grouping waste information obtained from each generator site and continues to use this approach for the 2009 CRA.  Since the 2004 CRA EPA decision, DOE initiated a yearly complex-wide data call to update the inventory annually. DOE's Carlsbad Field Office (CBFO) asks every TRU waste generator site to update the waste profile forms that describe the physical, chemical, and radiological constituents in each waste stream that generated or generates TRU waste at that site. The 2008 data call reflected the disposal intentions of the waste generator sites as of December 31, 2007.  DOE representatives examined the information, clarified questions and then validated the waste stream profile information.  This information was synthesized across the waste generator sites and then prepared for input into the performance assessment by scaling the inventory and other data reduction actions (e.g., decaying the estimated inventory to 2033).  This process is captured in the flowchart in Figure 24-2 (ATWIR-2008 Figure 2-1).

	Initially DOE used the same inventory that was used in the 2004 PABC calculations for the 2009 CRA performance assessment calculations, as noted in CRA-2009 Section 24 Section 24.6.1.  EPA examined the recent inventory updates and changes, mainly the ATWIR 2007 and the ATWIR 2008, and determined that a new performance assessment, the 2009 PABC (2009 PABC), needed to be conducted in order to include the increase in chemical components, (see Table 24-2, produced from PAIR 2008 Table 5-7).  EPA directed DOE to perform the 2009 PABC using the updated inventory in its first completeness letter, dated May 21, 2009, items 1-G-3 and 1-23-1 (EPA 2009a).

Table 24-2 Chemical Component Comparisons (Source: PAIR-2008 Table 5-7)

                            Chemical Components
                                      CCA
                                    Mass (kg)
                                  CRA-2004 PABC
                                   Mass (kg)
                                  CRA-2009 PABC
                                   Mass (kg)
Nitrate
1.62E+06
2.67E+06
1.72E+06
Sulfate
6.33E+05
4.43E+05
5.91E+05
Phosphate
                                      --
1.05E+05
1.99E+05
Acetic Acid
1.42E+02
1.42E+02
1.32E+04
Sodium acetate
1.11E+02
8.51E+03
9.70E+03
Citric Acid
1.19E+03
1.19E+03
5.68E+03
Sodium Citrate
4.00E+02
4.00E+02
2.55E+03
Oxalic Acid
1.38E+04
1.38E+04
2.66E+04
Sodium Oxalate
                                      --
3.39E+04
6.46E+02
Sodium EDTA
2.30E+01
2.56E+01
3.54E+02

      The details of the 2009 PABC inventory are presented in the Annual Transuranic Waste Inventory Report-2008, DOE/TRU-2008-3425 (ATWIR-2008), the scaled PA inventory in the Performance Assessment Inventory Report-2008, INV-PA-09 (PAIR-2008) and the Radionuclide Inventory Screening Analysis Report for the PABC-2009, ERMS 551679 (Fox et al. 2009).

	The chemical, physical, and radiological inventories continue to be grouped by DOE and developed in detail from the waste stream profiles from each of the TRU waste generator and/or storage sites.  Waste groupings (other than contact handled and remote handled designations) by DOE were based on the chemical and physical aspects of the waste, not the radiological content of the waste (CCA Appendix BIR).  However, the radiological constituents were identified and quantified (in Ci/m[3] for each waste stream) on each waste profile form, and information from the forms was used by DOE to develop the radiological inventory for the WIPP.  The CCA approach continues to be used in the 2009 CRA inventories.  Table A-1 of the 2009 SNL screening analysis for the 2009 PABC (Fox et al. 2009) shows the radiological constituents used for the 2009 PABC, including the inventory at the estimated time of disposal (year 2033), and estimated EPA units for each radionuclide.

	Each WIPP Waste Profile continues to contain information on the physical and chemical waste components (identified as Waste Material Parameters (WMP's) for DOE purposes) and the radiological waste components that DOE believes could affect the performance of the repository.  DOE's waste material parameters are presented as density values for use in performance assessment.  These density values are calculated by multiplying the average density of individual waste streams from a given waste form by the volume of the CID waste stream and then the total volume of the final waste form.

      The approximate average densities for waste material parameters were calculated, including iron based metals/alloys, aluminum based metals/alloys, other metal/alloys, other inorganic materials, vitrified materials, cellulosics, rubber, plastics, solidified inorganic matrix, solidified organic matrix, solidified cement, and soils (PAIR-2008 Inventory Report in Table 4-2 for CH and Table 4-3 for RH wastes).  WIPP Waste Profiles contain information on the WMPs, i.e., components that DOE determined to have the potential to impact repository performance.  DOE identified the quantity of physical waste components such as cellulosic material, plastic, rubber, etc., in the PAIR-2008 Inventory Report.  Tables 5-4 and Table 5-5 of the PAIR-2008 Inventory Report show the anticipated non-radioactive TRU waste inventory densities for the WIPP 2009 PABC calculations.

	Also, in accordance with 40 CFR 194.24(a), DOE's waste profiles contain specific information on the species and quantities of individual radioisotopes in the waste.
Figure 24-2 Process for Preparing the 2009 CRA TRU Waste Inventory (Source:  ATWIR-2008 Figure 2-1)
Figure 24-2 Process for Preparing the 2009 CRA TRU Waste Inventory (Source:  ATWIR-2008 Figure 2-1)
 Inventory Description
	DOE previously indicated that to-be-generated waste will be included in those waste streams and final waste forms currently identified at DOE sites (2004 CRA Chapter 4, Section 4.1.3); this has not changed for the 2009 CRA.  Therefore, the waste stream descriptors for existing waste also apply to to-be-generated waste.  Existing waste stream information was used by DOE in its description of to-be-generated waste.

	DOE continues to describe its contact-handled (CH) and remote-handled (RH) inventory as "stored," "emplaced" and "projected" or "anticipated."   The stored inventory is generally equivalent to existing waste at the sites, and projected waste is generally equivalent to to-be-generated waste (ATWIR-2008 and PAIR-2008).  Emplaced waste is waste that has been put underground at WIPP and is recorded in the WWIS database.  The anticipated inventory is the sum of the stored and projected inventories (ATWIR-2008 Inventory Report Section 1.0).  Table ES-1 of the 2008 PAIR Inventory Report lists the volumes of emplaced CH-TRU waste and Table ES-2 of the same report lists the emplaced RH volumes as of December 31, 2007 (the cutoff for inclusion in the 2008 inventory annual update).

	DOE's estimates indicate that the total expected inventory volume for CH-TRU and RH-TRU waste will not reach the maximum disposal capacity of the WIPP for CH-TRU or RH-TRU (approximately 168,500 m[3] (5,950,000 ft[3]) for CH-TRU and 7,079 m[3] (250,000 ft[3]) for RH-TRU) (PAIR-2008 Section 3.2.1).  DOE continues to employ a scaling factor to project the impacts of a full repository.  The current volume estimate of waste for disposal at WIPP is 130,400 m[3] for CH-TRU and 1,828 m[3] for RH-TRU.  DOE developed a scaling factor based upon the approximate CH-TRU and RH-TRU projected inventories it expects to be generated, as DOE believed that any new waste generated to "fill" the outstanding WIPP space would probably be more similar to the projected rather than existing waste inventory.  Tables 5-1 and 5-2 of the same report compare the scaled CH-TRU and RH-TRU waste volumes scaling factors used for the CCA, 2004 PABC, and the 2009 PABC.  The projected inventory information was derived from each generator site's waste stream profile forms, and reflects the sites' best determination of the waste expected to be generated.

	As reported in the PAIR-2008 Inventory Report, the scaling factor calculated by DOE in the 2009 PABC for CH-TRU waste is 5.72, and for RH-TRU waste is 4.87.  This factor is used in the following formulas to project the makeup of the CH-TRU and RH-TRU disposal inventory volume (m[3]) according to the LWA design limitations:

For CH-TRU waste:
Emplaced Inventory + Stored Inventory + (Projected Inventory x 5.72) = 2009 PABC Disposal Inventory

For RH-TRU waste:
Emplaced Inventory + Stored Inventory + (Projected Inventory x 4.87) = 2009 PABC Disposal Inventory

Number of Curies
	The total amount of radionuclide activities expected to be placed in WIPP has decreased slightly from the 2004 PABC estimate of 3.53 million curies to 3.45 million curies in the 2009 PABC (PAIR-2008 Inventory Report Table 5-6 and EPA 2009 CARD 31 Table 31-3).  Table 5-6 of the 2009 PABC Inventory Report (PAIR-2008) lists the activities of the 29 most important radionuclides in the 2009 PABC inventory.

	DOE documents changes to the inventory in each annual inventory report.  DOE changed a number of waste streams to the potential category; therefore they are not presently in the anticipated WIPP inventory for the 2009 PABC.  The changes documented in the two annual inventories, ATWIR-2007 page 3 and ATWIR-2008 page 14, are briefly discussed below:

New Inventory Items Since the 2004 CRA:
-Paducah's Gaseous Diffusion Plant TRU waste was re-categorized to WIPP bound because a waste processing method has been found (ATWIR-2008 page 14).

Inventory Items Placed in the Potential Category (*Not in Planned Inventory, Not Included in PA) Since the 2004 CRA:
-At the time the 2009 CRA was submitted, General Electric-Vallecitos Nuclear Center (GE-VNC) waste remained in potential because the site did not provide radionuclide and waste material parameters.  During the completeness review of the CRA, waste characterization activities were completed and this waste shipped to WIPP.  It is adequately represented by the scaled inventory.

- Waste streams from Babcock and Wilcox (BL) and the Nuclear Radiation Development Site (NRD) were added to the potential inventory because their defense determination has not been completed.

- Hanford RL and the Material Fuel Complex (MFC) waste streams that exceed the curie limit allowed in the LWA of 23,000 Ci/m[3] were changed to the potential inventory.

-Classified wastes at all sites are categorized as potential until their documentation is properly prepared for non-classified use.

-Hanford Richland (RL) has re-categorized some of its 618-10 and 618-11 buried waste to potential waste.  Hanford RL K-Basin knock-out pot sludge has been re-categorized to potential waste.  These two changes significantly reduced the overall RH-TRU waste volume.

-Hanford Office of River Protection (RP) tank waste has been re-categorized to potential waste.

-Two INL sodium-bearing waste streams were re-categorized to potential waste.

Other Inventory Changes:
-The volume of the TRU waste stored on site at West Valley was reduced because much of the waste managed as TRU in the past has been characterized as low-level waste.

Container Types
	While the container types are not used directly in the performance assessment calculations, the type of container continues to be important in order to estimate the amount of CPR in WIPP (PAIR-2008 Section 3.2.5).  Container types for CH-TRU waste have not changed since the 2004 CRA.  They include: 7-packs of 55-gallon drums, 4-packs of 85-gallon drums, 3-packs of 100-gallon drums, standard waste boxes (SWBs), ten-drum overpacks (TDOPs), standard large boxes (5x5x8 boxes), and 100-gallon drums.  The only new container since the 2004 CRA has been the introduction of RH canisters.  EPA's approval of RH waste is discussed in Section 24.6.3.

Organic Ligands
	At the time of the CCA, DOE's analysis used low ionic strength calculations to estimate the potential effect of organic ligands because the FMT (Fracture-Matrix Transport) code thermodynamic database was not complete at the time, and EPA's sensitivity analysis indicated that chelating agents (organic ligands) did not have a strong effect on the aqueous speciation of actinides because of competition with major ions that are present at much higher concentrations (CCA CARD 24, 24.C.5, p. 24-40 and 24-41).  For the 2004 CRA, both stability constants and Pitzer parameters had been determined, allowing inclusion of the organic ligands in the FMT speciation and solubility calculations (Docket A-98-49, Item II-B2-39).  Four organic ligands were included in the 2004 CRA FMT calculations of actinide solubilities: acetate, citrate, ethylenediaminetetraacetate (EDTA), and oxalate.

      In the 2009 PABC, organic ligands' importance increased due to increases in their volume in the predicted inventory.  One of the most important changes was the increase in mass of EDTA from 25.6 kg in the 2004 PABC to 354 kg in the 2009 PABC updated inventory.

	EPA directed DOE to include new solubility calculations in the 2009 PABC in the first completeness letter, item 1-23-1, dated May 21, 2009 (EPA 2009a).  DOE updated the solubilities and solubility uncertainties for the 2009 PABC (see Brush et al. 2009 and Xiong etal, 2009).  DOE notes in Brush et al. 2009 that dissolved concentrations increased by factors of: 1.83 for acetate, 2.95 for citrate, 7.95 for EDTA, and 2.63 for oxalate in brine of GWB composition for the 2009 PABC calculations (Brush et al. 2009 page 17).  The ERDA-6 brine composition had similar differences.  Increased organic ligand concentrations in turn increased the actinide concentrations in the brine, and resulted in greater releases for the direct brine pathway (Clayton et al. 2009 page 45).
24.1.6 Evaluation of Compliance for 2009 Recertification (194.24(a))

	EPA reviewed the 2009 CRA and supplemental information to determine whether it provided a sufficiently complete description of the chemical, radiological and physical composition of the emplaced, existing and to-be-generated waste proposed for disposal in the WIPP.  EPA also reviewed DOE's description of the approximate quantities of waste components (for both existing and to-be-generated waste).  EPA considered whether DOE's waste descriptions were of sufficient detail to enable EPA to conclude that DOE did not overlook any component that is present in transuranic waste and has significant potential to influence releases of radionuclides.

Chemical, Physical, and Radiological Description of Existing Waste
	Descriptions of the chemical, radiological, and physical components of the waste were thoroughly documented in 2009 CRA and supporting documents.  This information was collected using similar methods as during the CCA and the 2004 CRA, described above, thus the process used is reasonable.  EPA also conducted several visits to the waste generator sites to better understand the waste estimation process, including SRS, LANL, Hanford, and INL in 2008, and LANL and SRS in 2009.

	EPA concludes on the basis of this information that the 2009 CRA and supplemental information adequately describes the chemical, radiological, and physical characteristics of each waste stream proposed for disposal at the WIPP.  EPA further concludes that the information presented by DOE in the 2009 CRA provides adequate characterization of existing WIPP waste for use in PA.

	EPA noted the following changes in the waste:  DOE listed the to-be-generated (projected) waste in waste profile tables in ATWIR 2008 Table 3-1 for CH-TRU and Table 3-2 for RH-TRU waste.  The projected waste is categorized similarly to existing waste (e.g., heterogeneous debris, filter material, soil).  The amounts are ultimately expressed in density terms (kg/m[3]) for performance assessment purposes and the projected waste is a minority of the estimated inventory.  These factors continue to limit the potential effects of differences in the current estimates for projected waste and future actual amounts for the 2009 PABC.

	EPA concluded that DOE's development of the disposal inventory is sufficient for PA purposes.  EPA continues to agree with DOE that the use of projected waste inventory for scaling the WIPP CH-TRU and RH-TRU inventories to meet the total WIPP capacity is appropriate.  DOE's use of the inventory scaling process is similar to that used in the CCA and 2004 CRA and is adequate for projecting inventory estimates.

Waste Forms and Packaging: RH-TRU Waste
	The only change for waste packaging since the 2004 CRA is that RH-TRU waste shipments were begun and the RH emplacement canister use was started for RH disposal operations.

Waste Forms and Packaging:  Container Types
      As stated earlier in this CARD, the most important aspect of the waste containers for inventory purposes is the amount of metal that they contain, and the amount of metal required in the repository is minimum limit.  RH-TRU emplacement containers were used for the first time since the 2004 CRA. With their introduction, the amount of metal in the repository is increased.  EPA found the inclusion of waste container types in the inventory and PA to be reasonable.

Waste Forms and Packaging:  Inclusion of Waste Packaging in Inventory
      When preparing for the 2009 CRA performance assessment calculations DOE discovered that, "the CPR contents in emplacement materials were erroneously omitted from the CRA-2004 PABC" (Clayton et al. 2009).  DOE corrected this error in the 2009 CRA PA, this correction was also used in the 2009 PABC calculations.  EPA review changes to the 2009 CRA and 2009 PABC and found this error correction to be adequate.

Number of Curies, Waste Streams and Volume
	For the 2009 CRA, DOE continued to estimate the number of curies in the inventory on a site by site, waste stream by waste stream level using a reasonable process.  EPA requires that DOE produce a "list of the waste components and their approximate quantities."  EPA reviewed the estimates in ATWIR 2008 and PAIR 2008 reports and found these materials to contain sufficiently specific information on the species and quantities of individual radioisotopes in the waste.  In addition to the radioisotope inventory information, DOE also provided sufficient information on the chemical and physical waste components with descriptions in the ATWIR 2008 and PAIR 2008.

Organic Ligands
	The Agency reviewed the updated calculations related to the effect of organic ligands on actinide solubility and determined that organic ligands are potentially important (Brush et al. 2009, Xiong et al. 2009).  DOE properly included the impact of the increased organic ligands waste inventory in the 2009 PABC calculations.  EPA found this approach and results to be adequate.

Hanford Waste and K-Basin Waste
	In the 2004 CRA, DOE identified that it included waste from 12 tanks from Hanford (9 tanks of CH waste and 3 tanks of RH waste - see Table 24-1 for a summary of the tank waste).  As noted in Section 24.1.5 above, these waste streams and waste streams of K-Basin sludges have been removed from the anticipated waste stream inventory in the 2009 CRA PA and the 2009 PABC performance assessment calculations.  These wastes are not presently destined for disposal at WIPP.  EPA verified that they have been removed and concluded that DOE did not include them in the performance assessment calculations for the 2009 CRA or 2009 PABC.

      Many of the public comments received from stakeholders throughout the Recertification process addressed inventory issues.  Multiple groups objected that the Comprehensive Inventory Database was not made public.  In response to these comments, DOE provided both an Excel spreadsheet and PDF file of the inventory used for the 2009 (reference DOE letter).  Other comments indicated that this was not satisfactory to all stakeholders.  EPA determined that the information provided to the public was adequate for the purposes of recertification, and commits to continue to work to provide stakeholders with the most complete information available. Other comments dealt with issues related to the accuracy of the inventory.  These were all addressed by EPA's completeness letters to DOE (reference).  During its technical review, EPA determined that all questions related to inventory information had been adequately resolved.

     A significant number of comments addressed the legality of waste for disposal at WIPP.  Commenters objected to the inclusion of potential wastes in the anticipated inventory which lacked legal determinations as either transuranic or defense waste.  These objections have been raised before, and Section 24.1.3 above describes EPA's process of verifying that no illegal waste is shipped to WIPP.  The Agency reiterates that it will not consider commercial waste, high-level waste, or spent nuclear fuel for disposal at WIPP, and that inclusion of waste in the potential inventory in no way implies approval of that waste.  The PA inventory, as described in Section 24.1.5, is scaled up in order to provide an estimate of WIPP's inventory at the time of closure.  For the same reason, EPA does not agree with commenters' demands that no waste stream be shipped to WIPP without explicit inclusion in a PA.  A compliant PA sets limits for the chemical and radiological constituents of the inventory, which are then tracked on a daily basis and may not be exceeded (see Section 24.8 below).  This ensures that the inventory remains within the bounds of the most recent PA.   Commenters' objections to the secretive nature of DOE's defense and TRU determinations fall outside the scope of recertification, however, EPA will continue to work with DOE to make waste inventory decisions as transparent as possible.

24.1.7 2009 Recertification Decision (194.24(a))

	Based on a review and evaluation of the 2009 CRA and supplemental information provided by DOE (FDMS Docket ID No. EPA-HQ-OAR-2009-0330, Air Docket A-98-49), an assessment of the changes since the 1998 Certification Decision, in this CARD and in technical support documents for this section (EPA 2010a, EPA 2010b, EPA 2010f, and EPA 2010g) and the consideration of public comments, EPA determines that DOE continues to comply with the requirements of 194.24(a).

24.1.8 Changes in the 2014 Compliance Recertification Applications (194.24(a))

      To meet the requirements of Section 194.24(a), DOE continues to describe and categorize the entirety of TRU waste that is emplaced in WIPP and exists at various DOE facilities.  Since the first emplacement of waste in 1999, DOE has tracked the waste emplaced at WIPP using the WIPP Waste Information System (WWIS).  For the waste that is stored or to-be-generated at the waste generator sites, DOE developed a descriptive methodology for grouping waste information obtained from each generator site and continues to use this approach for the 2014 CRA.  Since the 2004 CRA EPA decision, DOE initiated a yearly complex-wide data call to update the inventory annually. DOE's Carlsbad Field Office (CBFO) asks every TRU waste generator site to update the waste profile forms that describe the physical, chemical, and radiological constituents in each waste stream that generated or generates TRU waste at that site.

      DOE adopted the same approach for the 2014-CRA as was used in PABC-2009 and utilized the ATWIR 2012 inventory and 2012 PAIR reports. The details of the CRA 2012 inventory are presented in the Annual Transuranic Waste Inventory Report-2012 (ATWIR-2012), and the Performance Assessment Inventory Report (PAIR)  -  2012 (Van Soest 2012) was released on November 29, 2012. The PAIR  -  2012 contains updated estimates to the radionuclide content and waste material parameters, scaled to a full repository, based on inventory information collected through December 31, 2011.  The Inventory Technical Support Document (Docket No. EPA-HQ-OAR-2014-0609) discusses changes in the inventory since the PABC-2009, as documented in ATWIR 2012 and PAIR 2012. As appropriate, comparisons are made to the PABC-2009 inventory relative to the CRA-2014.

	The chemical, physical, and radiological inventories continue to be grouped by DOE and developed in detail from the waste stream profiles from each of the TRU waste generator and/or storage sites.  Waste groupings (other than contact handled and remote handled designations) by DOE were based on the chemical and physical aspects of the waste, not the radiological content of the waste (CCA Appendix BIR).  However, the radiological constituents were identified and quantified (in Ci/m[3] for each waste stream) on each waste profile form, and information from the forms was used by DOE to develop the radiological inventory for the WIPP.  The CCA approach continues to be used in the 2012 CRA inventories.  Tables 5-1 and 5-2 of the PAIR 2012 shows the scaled volumes of the radiological constituents for each waste stream used for the 2012 CRA, including the inventory at the estimated time of disposal (year 2033).

	Each WIPP Waste Profile continues to contain information on the physical and chemical waste components (identified as Waste Material Parameters (WMP's) for DOE purposes) and the radiological waste components that DOE believes could affect the performance of the repository.  DOE's waste material parameters are presented as density values for use in performance assessment.  These density values are calculated by multiplying the average density of individual waste streams from a given waste form by the volume of the CID waste stream and then the total volume of the final waste form.

      The approximate average densities for waste material parameters were calculated, including iron based metals/alloys, aluminum based metals/alloys, other metal/alloys, other inorganic materials, vitrified materials, cellulosics, rubber, plastics, solidified inorganic matrix, solidified organic matrix, solidified cement, and soils (PAIR-2012 Inventory Report in Table 6-3).  WIPP Waste Profiles contain information on the WMPs, i.e., components that DOE determined to have the potential to impact repository performance.

	Also, in accordance with 40 CFR 194.24(a), DOE's waste profiles contain specific information on the species and quantities of individual radioisotopes in the waste.
24.1.9 Evaluation of Compliance for 2014 Recertification (194.24(a))

	EPA reviewed the 2014 CRA and supplemental information to determine whether it provided a sufficiently complete description of the chemical, radiological and physical composition of the emplaced, existing and to-be-generated waste proposed for disposal in the WIPP.  EPA also reviewed DOE's description of the approximate quantities of waste components (for both existing and to-be-generated waste).  EPA considered whether DOE's waste descriptions were of sufficient detail to enable EPA to conclude that DOE did not overlook any component that is present in transuranic waste and has significant potential to influence releases of radionuclides.

24.1.10 2014 Recertification Decision (194.24(a))

	Based on a review and evaluation of the 2012 CRA and supplemental information provided by DOE ((Docket No. EPA-HQ-OAR-2014-0609), an assessment of the changes since the 1998 Certification Decision, in this CARD and in technical support documents for this section and the consideration of public comments, EPA determines that DOE continues to comply with the requirements of 194.24(a).

24.2 Requirement (194.24(b)(1))

	(b) "The Department shall submit in the compliance certification application the results of an analysis which substantiates:

	(1) That all waste characteristics influencing containment of waste in the disposal system have been identified and assessed for their impact on disposal system performance.  The characteristics to be analyzed shall include, but shall not be limited to:  solubility; formation of colloidal suspensions containing radionuclides; production of gas from the waste; shear strength; compactability; and other waste-related inputs into the computer models that are used in the performance assessment."

24.2.1 1998 Certification Decision (194.24(b)(1))

	EPA expected the CCA to provide a detailed description of a waste characterization analysis that identifies a list of waste characteristics retained as a result of the analysis and explains the rationale for excluding any other waste characteristics.

	In the CCA, DOE presented the results of its waste characteristic and components analyses pursuant to 194.24(b)(1) in a number of documents.  CCA Chapter 4 and CCA Appendices MASS, WCA, SOTERM, and SA are the primary sources.  DOE indicated that the characteristics listed below were expected to have a significant effect on disposal system performance and so were used in the performance assessment (i.e., parameters were developed which account for the effects of each).

 Solubility (including redox state and redox potential).

 Formation of colloidal suspensions containing radionuclides.

 Production of gas from the waste (hydrogen, and microbial substrate/ nutrients for methane gas generation).

 Shear strength, compactability (waste compressibility), and particle diameter.

 Radioactivity in curies of each isotope.

 TRU radioactivity at closure.

	EPA concluded in the CCA that DOE generally performed a thorough and well documented analysis, adequately identified all waste characteristics and, except for actinide solubility and shear strength, appropriately assessed them as PA input parameters.  In the case of actinide solubility, EPA believed that DOE assumed an incorrect solubility that controls the mineral phase.  However, this error led to the use of higher actinide solubilities than what EPA believed would be realistic.  EPA's review indicated that modified solubility values for actinides were required, and the Performance Assessment Verification Test (PAVT) was run using these values.  DOE subsequently performed experiments that identified hydromagnesite as a metastable mineral species.  For the shear strength (TAUFAIL) in the PAVT, EPA required the probability distribution of the shear strength parameter to be changed to a log-normal distribution with a different range and median (CCA CARDs 23 and 24).  See CCA CARD 24 for a more complete discussion.

24.2.2 Changes in the 2004 Compliance Recertification Application (194.24(b)(1))

	There were no major changes to the waste characteristics between the PAVT and the CRA-2004 PABC, but DOE did make changes to some of the parameters used in the PA.  These are summarized in Table 24-3 below.  Most of these are related to inventory changes described above in section 24 (a).  EPA was most concerned with changes affecting solubility and gas generation.
Table 24-3 Characteristics expected to have a significant effect on disposal system performance and changes from the CCA (PAVT) to the 2004 CRA PABC
                 Waste Component or Characteristic Used in PA
                                 Significance
                             Increase or Decrease
                           From CCA to 2004 CRA PABC
Radioactivity per cubic meter
Used in calculating releases
Decrease
Solubility
Higher solubility can lead to higher releases when brine is present
Increase and Decrease, depending on oxidation state
Organic ligands -- complexing agents
Increases solubility
Similar amounts, but is now acknowledged to potentially be important
Amount of Metals
Maintains reducing environment, but also contributes to gas generation
Decrease
Amount of Cellulosics, Plastics, Rubbers
May increase gas generation from microbial processes
Increase
Oxyanions:  nitrate, sulfate, and phosphate
Nutrients for microbes, so indirectly affects gas generation
Similar, but overall increase
Cement
Primarily a volume related component
Decrease
Shear Strength
Affects mechanical releases during Low waste shear strength
No change
Particle Diameter
Used to calculate spallings releases
The PABC used the particle diameter determination from expert panel findings during the original certification. The particle diameter used in the CCA was rejected by EPA and not used in the subsequent PAVT calculations so there is not a valid comparison between the CCA and PABC.
Formation of colloidal suspensions
Colloids can facilitate transport of radionuclides in ground water
No change in parameterization, but DOE changed the implementation for the CRA to only include PA vectors that included microbes.  This changed again for the PABC back to the original treatment because all vectors were assumed to potentially generate microbes, and thus colloidal suspensions

Assessment of Waste Characteristics and Waste Characteristic Input Parameters
	In the CCA, DOE identified several waste characteristics as potentially important to the performance assessment (CCA Appendix WCA, Section WCA.6, pp. WCA-42 to WCA-43) based on available information, including uncertainties and WIPP system characterization.  These analyses were summarized in CCA Appendices WCA, SOTERM, and MASS, and were augmented by DOE's responses to EPA comments (CCA CARD 24).  The 2004 CRA identified the same important characteristics, although DOE now states that organic ligands can be important to solubility.

Solubility
	DOE originally stated in the CCA that solubility of actinides is among the major characteristics of the radionuclides expected to affect disposal system performance (CCA Appendix WCA, Section WCA.4, pp. WCA-30 to WCA-34).  DOE assessed the solubility of thorium, uranium, neptunium, plutonium, and americium (see below).  DOE states in the 2004 CRA's updated SOTERM (2004 CRA Appendix PA, Attachment SOTERM, p. 1):
	 "From the standpoint of their potential effects on the long-term performance of the repository, the order of importance of these actinides is Pu ≈ Am >> U > Th. Other actinides, especially neptunium (Np), have been included in the laboratory and modeling studies used to develop the actinide source term because it was not known at the outset which actinides could significantly affect the long-term performance of the repository."
DOE assumed that cesium and strontium are inventory limited (meaning that 100% of these isotopes would be dissolved) due to their high solubilities; therefore, formal solubility values were not derived for these two radionuclides (CCA Appendix WCA p. 30).
	DOE used the Fracture Matrix Transport (FMT) geochemical modeling code and its associated database to calculate solubilities.  No changes were made to the FMT code or conceptual models for the 2004 CRA performance assessment or 2004 PABC.  However, revisions were made to the input FMT database since the PAVT.  These changes included the addition of new aqueous actinide species to the database and revisions to existing species data because of the availability of new experimental data.

	DOE used the GWB Salado brine chemistry formulation instead of the Brine A formulation used in the CCA PA and PAVT.  The most significant differences between the brine formulations are the lower magnesium concentration and higher sulfate concentration in GWB relative to Brine A.  Comparison of geochemical modeling results using the two brine formulations indicates that GWB brines had slightly lower predicted +III actinide solubilities and higher +V actinide solubilities compared to Brine A.

2004 Performance Assessment Parameters Related to Solubility
	Solubility of actinides in the III, IV, V and VI oxidation states for both the Castile and Salado brines were calculated by DOE with the assumption that pH and f(CO2) are controlled by Mg(OH)2  -  MgCO3 equilibrium.  The solubilities (moles/liter) in Table 24-4 list the CCA and 2004 CRA PA values.  Table 24-5 lists the 2004 CRA PA values and the 2004 PABC values.

	The uncertainty ranges for the actinides in the 2004 CRA PA were the same as those used in the CCA.  DOE defined uncertainty limits for actinide concentrations calculated from solubility relationships based on the differences between measured concentrations and those predicted for the solubilities of discrete actinide solids with the FMT or NONLIN computer codes (Bynum 1996b).  These solubility differences were measured in a number of experimental studies of different actinide solids in high ionic strength solutions.

	Uncertainty limits were determined by DOE to range from 1.4 log units above to 2.0 log units below the actinide concentrations calculated from solubility expressions contained in the FMT model in the CCA.  These uncertainty ranges were used for each actinide sampled in the PA, that is for Am(III), Pu(III), Pu(IV), in Castile and Salado brines, U(IV) in Salado brine, U(VI) in both Castile and Salado brine, and Th(IV) in Salado brine.  The uncertainties in the actinide solubilities were used to define the range for Latin Hypercube Sampling of the actinide concentrations in the PA, assuming a log cumulative distribution (CCA CARD 24).

Table 24-4.  CCA and 2004 CRA Solubilities of the Oxidation State Analogs, in moles/liter, with MgO Backfill
            Solubilities for PA Material Name and Oxidation State#

           PA Parameter       SOLMOD3	          SOLMOD4	SOLMOD5	SOLMOD6
Brine	         Name		     (III)		   (IV)		    (V)      	     (VI*)
Salado	CCA SOLSIM	5.82 x 10-7		4.4 x 10-6	2.3 x 10-6	8.7 x 10-6
Salado	CRA SOLSIM	3.07 x 10-7		1.19 x 10-6	1.02 x 10-6	8.7 x 10-6

Castile	CCA SOLCIM	6.52 x 10[-8]		6.0 x 10[-9]	2.2 x 10[-6]	8.8 x 10[-6]
Castile	CRA SOLCIM	1.69 x 10[-7]		2.47 x 10[-8]	5.08 x 10[-6]	8.8 x 10[-6]

     # Solubility values were changed for the 2004 PABC.  The solubilities were changed to changes in chemical conditions agreed to by DOE and EPA. See Table 24-5.

     * These solubilities were not calculated in the FMT model.  In addition, these solubilities were changed to 1 x 10[-3] for the 2004 PABC as required by EPA due to the failure to incorporate new data that indicated the U(VI) solubilities could be greater than those used in the CCA and CRA-2004 PA.  This is discussed more later in the Evaluation of Compliance for Recertification section.

Formation of Colloidal Suspensions Containing Radionuclides
	Colloid formation can enhance the quantity of actinides contained in brine, and was evaluated by DOE as an important group of waste characteristics.  In the CCA DOE determined that four types of colloids may be present in the WIPP repository: Intrinsic colloids, mineral fragment colloids, humic colloids, and microbe colloids (CCA Appendix WCA Section WCA.4.2, pp. WCA-34 to WCA-36).  These colloids are still modeled in the 2004 PABC and are unchanged from the CCA (see CCA CARD sections 24.B.5 and 24.B.6 for additional information).

	DOE did, however, implement the colloidal actinide source term differently in the CRA-2004 PA than in the CCA.  In the CCA, DOE assumed all vectors would have a microbial colloid contribution to the actinide source term.  For the 2004 CRA PA, DOE assumed there would be microbial colloid transport only in vectors without significant microbial degradation.

Production of Gas From the Waste (Including Microbial Substrate and Nutrients)
	Gas generation includes hydrogen gas generation, as well as carbon dioxide and methane generation by microbial degradation.  The characteristics of gas generation are linked to the waste components of waste steel, microbial substrates such as cellulosics, rubber, and plastics (CPR), as well as other microbial nutrients (nitrate, sulfate and phosphate) that could be present.

	The same conceptual model was used for microbial gas generation in the WIPP repository for both the CCA and 2004 CRA.  In the conceptual model, it is assumed that microbial consumption of CPR may occur in the repository and produce methane (CH4) and carbon dioxide (CO2).  The major pathways for microbial degradation of 2004 CPR are predicted to include the following reactions:

		C6H10O5 + 4.8 H+ + 4.8 NO3-  7.4 H2O + 6 CO2 + 2.4 N2		(1)

		C6H10O5 + 6 H+ + 3 SO42-  5 H2O + 6 CO2 + 3 H2S		(2)

		C6H10O5 + H2O  3 CH4 + 3 CO2					(3)

where C6H10O5 is the chemical formula for cellulose.  In reactions (1) and (2), one mole of carbon dioxide is produced for each mole of organic carbon consumed.  Reaction (3), however produces only 0.5 moles of carbon dioxide per mole of organic carbon consumed.  Reactions (1) to (3) are predicted to proceed sequentially according to the energy yield of the reactions (Wang and Brush 1996).  As the denitrification and sulfate-reduction reactions (reactions 1 and 2, respectively) proceed, they are predicted to consume the limited amounts of nitrate and sulfate in the WIPP waste inventory.  In both the CCA and the 2004 CRA, it was predicted that methanogenesis (reaction 3) would be the dominant reaction pathway and consequently, that approximately half of the organic carbon consumed would be converted to carbon dioxide (CCA Appendix SOTERM Section 8.2.2; 2004 CRA Appendix PA Attachment SOTERM Section 2.2.2).

	Microbial gas generation rates used in the average stoichiometry model were based on experimental data from microbial consumption of papers under inundated and humid conditions (Wang and Brush 1996).  A gas-generation rate is determined in BRAGFLO for the humid and inundated rates based on the effective liquid saturation (2004 CRA Section <IP_ADDRESS>).  These gas generation rates were calculated from the initial linear part of the experimental curve of carbon dioxide as a function of time (2004 CRA Appendix PA Attachment PAR; Wang and Brush 1996).

	For the 2004 PABC, DOE requested a change to the implementation of the gas generation, based on DOE's review of additional experimental data collected over the last several years.  The gas generation rate exhibits two rates:  an initial higher rate and a second lower rate.  DOE proposed to EPA that the long-term rate be the gas generation rate used in the PA calculations, with the initial higher rate incorporated as an initial higher pressure.

Performance Assessment Parameters Related to Gas Generation
	DOE used Latin Hypercube Sampling (LHS) in PA for the following gas-generation-related parameters:

 Inundated steel corrosion rate

 Probability of microbial degradation of plastics and rubbers (in the event of     microbial gas generation)

 Biodegration rate of cellulosics, inundated and humic

 Factor β for microbial reaction

Performance Assessment Parameters Related to Shear Strength, Compactability (Compressibility) and Particle Diameter
	There were no changes from the PAVT.

Radioactivity in Curies of Each Isotope
	In the CCA, DOE indicated (Sections 3.1 and 3.2 of CCA Appendix WCA) that the radioactivity of each isotope is important to the performance assessment because it directly affects the waste unit factor (number of million curies of TRU isotopes in the WIPP inventory), which is the normalization factor used to calculate allowable releases for each radionuclide (see Table WCA-1 in CCA Appendix WCA).   Since the same approach is used in the 2004 CRA, the CCA approach is summarized.

  The following radionuclides were determined important by DOE (CCA Figure WCA-4):

 Cuttings/cavings/spallings release:  [238]Pu, 239Pu, 240Pu, 241Pu, [241]Am, [233]U, 234U, [90]Sr, [137]Cs, [244]Cm.

 Direct Release in Brine:  [238]Pu, [239]Pu, [240]Pu, [241]Pu, [242]Pu, [241]Am, [243]Am, [233]U, [234]U, [235]U, [236]U, [238]U, [229]Th, 230Th, [232]Th, [237]Np, [243]Cm, [244]Cm, [245]Cm.

 Long-term groundwater release:  [239]Pu, [240]Pu, [242]Pu, [241]Am, [233]U, [234]U, [229]Th, [230Th].

	DOE indicated that U and Th isotopes are required in direct brine release assessments because, although they comprise negligible fractions of the total EPA unit, they do influence the total quantity of dissolved radionuclides (p. WCA-22).  In addition, DOE indicated that although EPA units for [90]Sr and [137]Cs at the time of the WIPP's closure are significant, they are not included in direct release of brine because they rapidly decay and result in "negligible impact on the PA from those two isotopes" (p. WCA-26).  If a direct brine release occurred early after closure, the total brine released would be minimal and the [90]Sr and [137]Cs would still, therefore, play a minor role in compliance (p.WCA-26).

	DOE justified the radionuclide list for the long-term groundwater pathway (releases to the Culebra) based upon the following (CCA Appendix WCA, Section WCA.3.2.3, pp. WCA-26 to WCA-27):

 [233]U can be combined with [234]U for transport because their half-lives are similar.

 [229]Th can also be combined with [230]Th because they are in a fixed ratio to each other.

 [232]Th can be dropped because it is a constant small fraction of normalized releases throughout the 10,000-year regulatory period.

 [240]Pu and [242]Pu can be combined with [239]Pu. Long half-lives also indicate a fixed ratio between them.

 [238]Pu will have decayed to about 0.5% of its initial inventory after 700 years, and its contribution to releases will be negligible because of the long (>700 year) travel time in the Culebra; it was therefore dropped from consideration.

Performance Assessment Parameters Related to Radioactivity in Curies of Each Isotope
	DOE used the information from the update of the CCA inventory to define the isotope inventory for the 2004 CRA PA, which was modified for the 2004 PABC.  Refer to Section 194.24(a) of this CARD for a discussion regarding the description of this inventory.  The 2004 PABC Inventory Report (Docket A-98-49, Item II-B2-60) provides the radioactivity in curies of each isotope used in the 2004 PABC (See Table 14, p. 37).

TRU Radioactivity at Closure
	Table 14 of the 2004 PABC Inventory Report lists the DOE inventory at closure, based upon the September 2002 cutoff and updates described in Section 194.24(a) above.  The 2004 PABC Inventory Report indicates that the inventory activity estimate for the year 2033 (the planned date for closure) is 2.32 x 106 Ci, resulting in a waste unit factor of 2.32.

Performance Assessment Parameters Related to TRU Radioactivity at Closure
	The 2.32 waste unit factor is the number of millions of curies of alpha-emitting TRU radionuclides with half-lives longer than 20 years used in the calculation of the EPA normalized unit.  DOE discusses this in 2004 CRA Chapter 4 and Appendix TRU Waste Section TRU Waste-2 and in the 2004 PABC Inventory Report page 36.

	A complete description of EPA's 1998 Certification Decision for Section 194.24 can be obtained from EPA Air Docket, A-93-02, Items V-A-1 and V-B-2.

24.2.3 Evaluation of Compliance for 2004 Recertification (194.24(b)(1))

	For the CCA, EPA reviewed information on waste characteristics and components in a number of technical documents.  This review encompassed references, experimental programs, logical arguments, and modeling.  EPA determined all relevant waste characteristics and components were identified and evaluated.  For the 2004 CRA, EPA focused on changes and new information that could affect DOE's analyses and findings.

	EPA concluded that, with the combination of the 2004 CRA, supplemental information, and the PABC, DOE performed an adequate update to the CCA.

Solubility
	EPA's review identified two areas in which DOE failed to adequately address solubility.  First, DOE did not update the uranium (+VI) solubility to incorporate new data that had become available since the certification decision.  The data indicated that the +VI solubility should be higher than that used by DOE in the CRA-2004 PA.  Second, DOE failed to update the solubility uncertainty ranges used for actinide solubility oxidation states based on new data.

	For the 2004 PABC, EPA stated that the solubility of U(+VI) needed to be changed to a fixed value of 1 x 10[-3] M because of experimental data that became available since the CCA.  In addition, EPA required that new solubility uncertainty ranges, based on the FMT database and currently available experimental solubility data, be incorporated into the 2004 PABC.  DOE made additional changes to the calculation of the +III, +IV, and +V actinide solubilities based on revised thermodynamic data for the +IV actinides, a different Salado brine formulation, and revised concentrations of organic ligands.  These changes were properly implemented as discussed in Section 7 of the Technical Support Document for Section 194.24:  Evaluation of the Compliance Recertification Actinide Source Term and Culebra Dolomite Distribution Coefficient Values (A-98-49, Item II-B1-3).  Table 24-5 lists the actinide solubility values for the 2004 PABC and the 2004 CRA PA.

	Other changes and improvements incorporated into the calculation of actinide solubilities for the 2004 PABC that have been implemented since the PAVT include:

 Incorporation of organic ligand complexation data into the FMT thermodynamic database so the effects of organic ligands on +III, +IV, and +V actinide solubilities can be calculated directly.  The organic ligand concentration changes were the result of corrections to the masses of organic ligands and the minimum estimated brine volume required for a release from the repository.

 Refinement of the thermodynamic database using new +III, +IV, and +V actinide data

 Use of GWB instead of Brine A as the Salado Brine formulation for actinide solubility calculations

 Correction of the minimum brine volume necessary for direct brine release

 Revision of the estimated uranium(VI) solubility to account for new data

 Recalculation of actinide solubility uncertainties based on a much larger number of solubility measurements, with separate distributions developed for the +III, +IV, and +V actinide solubilities instead of the single distribution used for the PAVT.  The new ranges are provided in Table 24-6.

Table 24-5 2004 CRA PA and 2004 PABC Solubilities of the Oxidation State Analogs, in moles/liter, with MgO Backfill

            Solubilities for PA Material Name and Oxidation States

       PA Parameter	        SOLMOD3	         SOLMOD4	SOLMOD5	SOLMOD6
Brine	    Name		             (III)		   (IV)		    (V)      	     (VI*)
Salado   PABC SOLSIM	3.87 x 10-7		5.64 x 10-8	3.55 x 10-7	1 x 10-3
Salado   CRA04 SOLSIM	3.07 x 10-7		1.19 x 10-6	1.02 x 10-6	8.7 x 10-6

Castile   PABC SOLCIM	2.88 x 10[-7]		6.79 x 10[-8]	8.24 x 10[-7]	1 x 10[-3]
Castile   CRA04 SOLCIM	1.69 x 10[-7]		2.47 x 10[-8]	5.08 x 10[-6]	8.8 x 10[-6]
Table 24-6 Cumulative Distribution Function (CDF) Ranges Established by the Revised Actinide Solubility Uncertainty Analysis for the 2004 PABC.  The CDF Ranges Vary by Oxidation State.  No Range Was Used for the +VI Oxidation State Since EPA Required DOE to Use an Upper Bound for the Uranium Solubility.
                           Actinide Oxidation State
                                   CDF Range
                                      III
                                 -3.00 to 2.85
                                      IV
                                 -1.80 to 2.40
                                       V
                                 -1.95 to 1.95

Colloids
	The PAVT included microbial colloid transport of actinides for all vectors.  The 2004 CRA PA included different assumptions about the colloidal source term concentrations for microbial and non-microbial vectors, with no microbial colloid transport of actinides assumed for non-microbial vectors.  However, for the 2004 PABC, it was assumed that all vectors included microbial activity.  Therefore, DOE included microbial colloid transport of actinides for all 2004 PABC vectors (Brush 2005).  This approach, therefore, was the same for the PAVT and 2004 PABC, and was consistent with the Agency's direction that all vectors include microbial activity.

Production of Gas from the Waste
	Microbial degradation of CPR may influence WIPP repository performance because of its effects on repository chemistry and gas generation.  The Agency reviewed the approach and assumptions used by DOE to model microbial degradation for the 2004 CRA PA.  The Agency's review comments to DOE focused on the probability of significant microbial degradation, the nature of the microbial degradation reactions likely to occur in the repository, and microbial gas generation rates.  As a result of the Agency's review and comments, DOE changed the modeling of microbial degradation processes for the 2004 PABC.

	During the review of the 2004 CRA PA, the Agency noted that additional information related to the probability of significant microbial degradation in the WIPP repository had become available since the time of the CCA PA and PAVT.  EPA reviewed the information presented by DOE and other available information and concluded that new data regarding the potential existence and survival of microbes had increased the probability of significant microbial degradation of cellulosics.  On the other hand, the Agency did not find significant information supporting an increase in the probability of microbial degradation of plastics and rubbers in the repository.  Therefore, the Agency instructed DOE to assume that microbial degradation of CPR would occur in all 2004 PABC vectors.
	Based on the inventories of nitrate and sulfate in the waste, DOE assumed in the 2004 CRA PA that these constituents would be quickly consumed during microbial degradation of CPR in the waste, and that methanogenesis would therefore be the dominant microbial degradation reaction.  However, adequate sulfate anions are likely to be available in the Salado anhydrite interbeds and will insure that methanogenesis does not occur regardless of the quantity of sulfate in the waste. Because DOE had not conclusively demonstrated that methanogenesis would be the dominant pathway for microbial degradation reactions, the model required revision.  This pathway was eliminated by DOE in the 2004 PABC and only denitrification and sulfate reduction reactions were included in the microbial gas generation model.  Based on the revised 2004 PABC inventory values, 4% of the microbial gas generation is from denitrification and 96% is from sulfate reduction.  These reactions will produce one mole of carbon dioxide for each mole of CPR carbon consumed by microbial degradation.  DOE has adequately revised the microbial gas generation reactions and evaluated the effects on PA.

	During the review of the 2004 CRA PA, DOE informed the Agency that the microbial gas generation experiments had continued and additional information related to microbial gas generation rates in the WIPP repository had become available since the time of the CCA PA and the PAVT.  In the letter directing DOE to perform the 2004 PABC, the Agency allowed DOE to propose a new gas generation rate scheme based on the new experimental data.

	Because of the shape of the curve formed by carbon dioxide generated as a function of time, the degradation rates were modeled by obtaining a least-squares fit of two linear functions to the reported mean values for the carbon dioxide gas generation data.  In this manner, both a short-term and a long-term rate were determined for each experimental data set.  A minimum of three data points were included in each short-term or long-term fit to the data.

	The revised microbial gas generation rates were based on long-term experimental data.  Therefore, gas generation during the early stages of the repository was accounted for in BRAGFLO by assuming a fixed amount of gas was present in the repository at the beginning of the calculations.  The amount of gas in the repository was assumed to be equal to the amount of gas generated per gram of cellulose at the point where the relatively rapid short-term rate changed to the slower long-term rate in the nutrient and nitrate-amended inundated experiments; these experiments were used to evaluate the maximum long-term rate.  This amount of gas initially present in the repository was converted to a pressure value of 26.714 kPa using the ideal gas equation and the volume and temperature of the repository.  This additional pressure was assumed to be generated immediately upon closure, resulting in an initial total repository pressure of 128,039 kPa.
	At the Agency's direction, DOE changed the probability of microbial degradation to account for new evidence regarding the presence and viability of microbes capable of degrading CPR in the WIPP repository.  The revised probability parameters resulted in microbial degradation in all vectors for the 2004 PABC.  However, DOE asserted that uncertainties remained regarding the viability of microbes in the repository because of different conditions in the repository compared to the conditions in the experiments.  DOE therefore introduced an additional sampled parameter, BIOGENFC.  This parameter, which had a uniform distribution from 0 to 1, was multiplied by the microbial gas generation rates to effectively reduce the humid and inundated microbial gas generation rates from the experimentally determined long-term rates.

	EPA did not receive any public comments on DOE's continued compliance with the requirements of Section 194.24(b)(1).
24.2.4 2004 Recertification Decision (194.24(b)(1))

	After a modification of the actinide solubility, solubility uncertainty ranges, methanogenesis assumption, and microbial gas generation rate and probability and based on a review and evaluation of the 2004 CRA and supplemental information provided by DOE (FDMS Docket ID No. EPA-HQ-OAR-2004-0025, Air Docket A-98-49), EPA determined that DOE continues to comply with the requirements for Section 194.24(b)(1).
24.2.5 Changes in the 2009 Compliance Recertification Application (194.24(b)(1))

	There were important changes made to the waste characteristics between the CRA-2004 PABC and the CRA-2009 PABC.  DOE also made changes to some of the parameters used in the PA, in particular increasing the quantity of certain chemical components.  These are summarized in Table 24-7, below.  Most of these are related to inventory changes described above in Section 24.1.5.  EPA continued to be most concerned with changes affecting actinide solubility and gas generation for the 2009 recertification.
Table 24-7 Characteristics expected to have a significant effect on disposal system performance and changes from the 2004 CRA PABC to the 2009 CRA PABC
                 Waste Component or Characteristic Used in PA
                                 Significance
                             Increase or Decrease
                           From CCA to 2009 CRA PABC
Radioactivity per cubic meter
Used in calculating releases
Slight decrease
Solubility
Higher solubility can lead to higher releases when brine is present
Increase
Organic ligands -- complexing agents
Increases solubility
Significant increase in acetic acid, sodium citrate, and EDTA.
Amount of Metals
Maintains reducing environment, but also contributes to gas generation
Decrease for CH-TRU, increase for RH-TRU
Amount of Cellulosics, Plastics, Rubbers
May increase gas generation from microbial processes
Slight increase
Oxyanions:  nitrate, sulfate, and phosphate
Nutrients for microbes, so indirectly affects gas generation
Similar, but overall slight increase
Cement
Primarily a volume related component
Increase
Shear Strength
Affects mechanical releases during Low waste shear strength
No change
Particle Diameter
Used to calculate spallings releases
No change
Formation of colloidal suspensions
Colloids can facilitate transport of radionuclides in ground water
No change

Assessment of 2009 CRA Waste Characteristics and Waste Characteristic Input Parameters
	In the original CCA, DOE identified several waste characteristics as potentially important to the performance assessment (CCA Appendix WCA, Section WCA.6, pp. WCA-42 to WCA-43) based on available information, including uncertainties and WIPP system characterization.  These analyses were summarized in CCA Appendices WCA, SOTERM, and MASS, and were augmented by DOE's responses to EPA comments (CCA CARD 24).  The 2004 CRA identified the same important characteristics and DOE added organic ligands as important waste components that may increase waste solubility.  The most significant change since the 2004 CRA is that the EDTA mass increased by more than 10 times (Table 24-2, PAIR-2008 Table 5-7).

2009 CRA Solubility Discussion
	DOE continued to use the Fracture Matrix Transport (FMT) geochemical modeling code and its associated database to calculate solubilities.  No changes were made to the FMT code, FMT database, or dissolved actinide solubility conceptual models for the 2009 PABC solubility calculations.  However, revisions were made to the input FMT database since the 2004 PABC (EPA 2010a Section 6.5).  The major differences in the input data are the increased organic ligand inventory and minimum brine volume used in the new 2009 PABC calculations.  The actinide solubility uncertainties used for the 2004 PABC calculations were also revised for the 2009 calculations.

2009 CRA Performance Assessment Parameters Related to Solubility
	Solubilities of actinides in the III, IV, V and VI oxidation states for both the Castile and Salado brines continue to be calculated by DOE with the assumption that pH and f(CO2) are controlled by Mg(OH)2  -  MgCO3 equilibrium.  The solubilities (moles/liter) in Table 24-8 list the CCA, 2004 CRA PA, 2004 PABC, and the new 2009 PABC solubility values (Clayton et al. 2009 Section 2.2).  The uncertainty ranges for the actinides in the 2009 CRA PABC were also changed for the 2009 PABC (Table 24-9).

Table 24-8 Solubilities of the Oxidation State Analogs, in moles/liter, with MgO Backfill
             Solubilities for PA Material Name and Oxidation State

           PA Parameter       SOLMOD3	          SOLMOD4	SOLMOD5	SOLMOD6
Brine	         Name		     (III)		   (IV)		    (V)      	     (VI*)
Salado	CCA SOLSIM	5.82 x 10-7		4.40 x 10-6	2.30 x 10-6	8.7 x 10-6
Salado     CRA04 SOLSIM	3.07 x 10-7		1.19 x 10-6	1.02 x 10-6	8.7 x 10-6
Salado    PABC04 SOLSIM   3.87 x 10-7             5.64 x 10-8       3.55 x 10-7         1.0 x 10-3
Salado    PABC09 SOLSIM   1.66 x 10-6             5.63 x 10-8       3.90 x 10-7         1.0 x 10-3
Castile	CCA SOLCIM	6.52 x 10[-8]		6.00 x 10[-9]	2.20 x 10[-6]	8.8 x 10[-6]
Castile     CRA04 SOLCIM	1.69 x 10[-7]		2.47 x 10[-8]	5.08 x 10[-6]	8.8 x 10[-6]
Castile   PABC04 SOLCIM   2.88 x 10[-7]             6.79 x 10[-8]       8.24 x 10[-7]         1.0 x 10[-3]
Castile   PABC09 SOLCIM   1.51 x 10[-6]             6.79 x 10[-8]       8.75 x 10[-7]         1.0 x 10[-3]
* See Section 24.2.3 of this CARD.

2009 CRA Formation of Colloidal Suspensions Containing Radionuclides
	Colloid formation can enhance the quantity of actinides contained in brine, and continues to be evaluated as an important group of waste characteristics.  In the CCA DOE determined that four types of colloids may be present in the WIPP repository: Intrinsic colloids, mineral fragment colloids, humic colloids, and microbe colloid.  These colloids are still modeled in the 2009 PABC and are unchanged from the CCA.

	DOE did not change the implementation of the colloidal actinide source term approach from the CRA-2004 PABC in the 2009 PABC.  In the 2004 CRA PA, DOE assumed there would be microbial colloid transport only in vectors without significant microbial degradation.  The 2004 PABC included microbial degradation in all vectors.  This assumption did not change in the 2009 CRA PAs.

2009 CRA Production of Gas From the Waste (Including Microbial Substrate and Nutrients)
	The same conceptual model was used for microbial gas generation in the WIPP repository for the CCA, the 2004 CRA and the 2009 CRA.  The model implementation was changed in the 2004 CRA (Section 24.2.2 of this CARD). The 2009 CRA used the same implementation (2009 CRA Section <IP_ADDRESS>).

2009 CRA Performance Assessment Parameters Related to Gas Generation
	DOE used Latin Hypercube Sampling (LHS) in PA for the following gas-generation-related parameters:

 Inundated steel corrosion rate

 Probability of microbial degradation of plastics and rubbers (in the event of     microbial gas generation)

 Biodegradation rate of cellulosics, inundated and humic

 Factor β for microbial reaction

	This continues to be DOE's approach in the 2009 CRA PAs.

2009 CRA Performance Assessment Parameters Related to Shear Strength, Compactability (Compressibility) and Particle Diameter
	There have been no changes to these parameters since the PAVT.

2009 CRA Radioactivity in Curies of Each Isotope
	In the CCA, DOE indicated (Sections 3.1 and 3.2 of CCA Appendix WCA) that the radioactivity of each isotope is important to the performance assessment because it directly affects the waste unit factor (number of million curies of TRU isotopes in the WIPP inventory), which is the normalization factor used to calculate allowable releases for each radionuclide (see Table WCA-1 in CCA Appendix WCA).   DOE used the same approach in the 2004 CRA and the 2009 PABC.  See Section 24.2.2 of this CARD for a more complete discussion.

2009 CRA Performance Assessment Parameters Related to Radioactivity in Curies of Each Isotope
	DOE used the information from the update of the PAIR-2008 inventory to define the isotope inventory for the 2009 PABC.  Refer to Section 24.1.5 of this CARD for a discussion regarding the description of this inventory.  The PAIR-2008 provides the radioactivity in curies of each isotope used in the 2009 PABC.

2009 CRA TRU Radioactivity at Closure
	PAIR-2008 Table A-1 lists the DOE inventory at closure, based upon the December 31, 2007 cutoff date and updates described in Section 24.1.5 of this CARD.  Fox, Clayton and Kirchner(2009), Table B-2 indicates that the inventory estimate for the year 2033, which is the planned date for closure, is 2.60 x 106 Ci.  Thus the waste unit factor (WUF) - the number of millions of curies of alpha-emitting TRU radionuclides with half-lives longer than 20 years used in the calculation of the EPA normalized unit - is 2.60 (Fox, Clayton and Kirchner 2009, page 6).   Out of the 145 radionuclides reported in the present inventory, 17 transuranic waste radionuclides contribute to the unit of waste used to calculate the WUF.

24.2.6 Evaluation of Compliance for 2009 Recertification (194.24(b)(1))

	For the 2009 CRA, EPA focused on changes and new information in DOE's analyses that could impact disposal system performance based on changes in waste characteristics, such as solubility and gas generation.  EPA concluded that, with the combination of the 2009 CRA, supplemental information, and the 2009 PABC, DOE performed an adequate update to the CCA and the 2004 recertification.

2009 CRA Solubility
	DOE used the 2004 CRA inventory in the 2009 CRA PA calculations.  Comparison of the most recent 2008 inventory data on organic ligands (Crawford et al. 2009) with the quantities used to calculate actinide solubilities for the CRA-2004 PABC shows that organic ligand quantities have increased dramatically for acetic acid, citric acid, sodium citrate, and sodium EDTA (Table 24.2).  Because of the potential effects of organic ligands on actinide solubilities, EPA instructed DOE to include the revised inventory of organic ligands in the CRA-2009 PABC actinide solubility calculations (Cotsworth 2009a, Comments 1-23-1 and 1-23-4).  In addition, EPA requested that DOE consider the updated inventory of organic ligands and the extent to which ligands are likely to affect actinide solubilities (Cotsworth 2009a, Comments 1-C-6 and 1-C-14).  Moody (2009a) responded that DOE would perform a new PA that includes an updated EDTA, acetate, citrate, and oxalate concentration, based on the information provided in Crawford et al. (2009) and provide documentation of this PA to EPA.
	Other changes and improvements incorporated into the calculation of actinide solubilities for the 2009 PABC include: changes to the MgO excess factor and MgO reactivity test procedure (EPA 2010i Section 4.0) and re-evaluation of the actinide distribution coefficients used in the 2009 PABC to account for the effects of higher organic ligand concentrations (EPA 2010a Section 10.0).
Table 24-9  Cumulative Distribution Function (CDF) Ranges Established by the Revised Actinide Solubility Uncertainty Analysis for the 2009 PABC.
                           Actinide Oxidation State
                                   CDF Range
                                      III
                                 -4.20 to 2.70
                                      IV
                                 -2.25 to 3.30
Source: Xiong et al. 2009, Table 7 and Table 11

2009 CRA Colloids
	DOE included microbial colloid transport of actinides for all 2004 PABC vectors (Brush 2005).  This approach was the same approach applied in the 2009 CRA PAs.  No changes have been made to the Colloidal Actinide Source Term conceptual model or its implementation since the CCA PAVT.  Data developed since the CCA PAVT, most notably the evidence from Wall and Mathews (2005), indicate that the current model is likely to conservatively overestimate colloidal associated actinides in the source term.

At the May 2010 public stakeholder meeting related to EPA's completeness decision, and later in written comments, Citizens for Alternatives to Radioactive Dumping (CARD) requested that the Agency verify that experimental results from Argonne National Laboratory related to the structure of plutonium nanocolloids which possess enhanced transport capabilities.  EPA issued a completeness letter asking whether DOE has incorporated these results into the 2009 PABC.  In its letter dated September, 2010, DOE indicated that it was aware of the results.  The ANL experiments were carried out in a low-pH environment, making the formation of these colloids unlikely in WIPP-relevant conditions.  However, the inclusion of intrinsic colloids in the PA conservatively takes into consideration the formation and transport of these colloids (DOE 2010g).  EPA concurs with DOE.

2009 CRA Production of Gas from the Waste
	As noted earlier, the gas generation conceptual model and model implementation were not changed in the 2009 CRA PAs (see Section 24.2.2 of this CARDS for details).  EPA verified that microbial degradation of CPR occurs in all 2009 PABC vectors, that both a short-term and long-term gas generation rates based on experimental results are used, and that methanogenesis does not occur regardless of the quantity of sulfate in the waste (2009 CRA Appendix PA-2009 Section PA 4.2.5).  EPA finds DOE's approach to be adequate.

	EPA did not receive any additional public comments on DOE's continued compliance with the requirements of Section 194.24(b)(1).

24.2.7 2009 Recertification Decision (194.24(b)(1))

	After a modification of the actinide solubility, solubility uncertainty ranges, methanogenesis assumption, and microbial gas generation rate and probability and based on a review and evaluation of the 2009 CRA and supplemental information provided by DOE (FDMS Docket ID No. EPA-HQ-OAR-2004-0025, Air Docket A-98-49), EPA determines that DOE continues to comply with the requirements for Section 194.24(b)(1).

24.2.8 Changes in the 2014 Compliance Recertification Application (194.24(b)(1))

	There were important changes made to the waste characteristics since the CRA-2009 PABC, for example, waste component information was updated and added waste inventory parameters were used in the WIPP PA.  DOE also updated some of the waste related parameters used in the PA.  Additional parameters include the mass of waste and packaging materials, the solubilities calculated using multiples of the minimum brine volume necessary for a DBR to occur, and those to describe the additional biodegradation reactions implemented within the repository chemistry model. These are summarized in Table 24-8, below (2014 CRA DOE Section 24.8.2).  Most of these are related to inventory changes described above in Section 24.1.5.

Table 24-8 Characteristics expected to have a significant effect on disposal system performance and changes from the 2009 CRA PABC to the 2014 CRA PA
                 Waste Component or Characteristic Used in PA
                                 Significance
                             Increase or Decrease
                        From 2009 PABC to 2014 CRA PA
Radioactivity per cubic meter
Used in calculating releases
Decrease
Solubility
Higher solubility can lead to higher releases when brine is present
Increase and decrease, depending on oxidation state
Organic ligands -- complexing agents
Increases solubility
Decrease
Amount of Metals
Maintains reducing environment, but also contributes to gas generation
Decrease
Amount of Cellulosics, Plastics, Rubbers
May increase gas generation from microbial processes
Decrease
Oxyanions: nitrate, sulfate, and phosphate
Nutrients for microbes, so indirectly affects gas generation
Increase and decrease
Cement
Primarily a volume related component
Decrease
Shear Strength
Affects mechanical releases during Low waste shear strength
Increase
Particle Diameter
Used to calculate spallings releases
No change
Formation of colloidal suspensions
Colloids can facilitate transport of radionuclides in ground water
Increase and decrease

Assessment of 2014 CRA Waste Characteristics and Waste Characteristic Input Parameters
	In the original CCA, DOE identified several waste characteristics as potentially important to the performance assessment (CCA Appendix WCA, Section WCA.6, pp. WCA-42 to WCA-43) based on available information, including uncertainties and WIPP system characterization.  These analyses were summarized in CCA Appendices WCA, SOTERM, and MASS, and were augmented by DOE's responses to EPA comments (CCA CARD 24). DOE noted that organic ligands were important waste components that may increase waste solubility, therefore organic ligands continue to be included in the solubility calculations (Brush and Domski 2013a).  These changes are refinements to the implementation of the PA conceptual models; no changes were made to these models for the 2014 CRA PA.

2014 CRA Solubility
      DOE notes that the CRA-2014 includes new solubility values for Th(IV), Np(V) and Am(III) (Brush and Domski 2013a), and new solubility uncertainty distributions (Brush and Domski 2013b). The DOE also implemented a new method for calculating the organic ligand concentrations for the minimum brine volumes necessary for a DBR by adding additional parameters (Camphouse 2013). The DOE replaced FMT with EQ3/6, Version 8.0, and the thermodynamic database DATA0.FMT.R2, also known as DATA0.FM1, for the analyses performed in support of the CRA-2014. The CRA-2014 continues to include the effects of organic ligands in the solubility calculations, as was first done in the CRA-2004.

2014 CRA Performance Assessment Parameters Related to Solubility
	Solubilities of actinides in the III, IV, V and VI oxidation states for both the Castile and Salado brines continue to be calculated by DOE with the assumption that pH and f(CO2) are controlled by Mg(OH)2  -  MgCO3 equilibrium.  The Agency had some questions and concerns related to DOE's updated uncertainty distribution used in the CRA 2014 PA. The Agency identified some inconsistencies DOE had adopted in selecting the references used in that distribution. As a result of these concerns, the Agency requested DOE revise the references to be used in developing the actinide solubility uncertainty distributions and resulted in a different actinide uncertainty distribution. The resulting actinide uncertainty distribution was used in the SEN4 sensitivity study. The revised criteria and references to be used in developing the actinide uncertainty in the SEN4 study are listed in (Table 24-10) discussed in Technical Support Document in Support of Section 194.24 Evaluation of the Compliance Recertification Actinide Source Term, Gas Generation, Backfill Efficacy, Water Balance, and Culebra Dolomite Distribution Coefficient Values. (Docket ID No. EPA-HQ-OAR-2014-0609).
Table 24-9 Solubilities of the Oxidation State Analogs, in moles/liter, with MgO Backfill
             Solubilities for PA Material Name and Oxidation State

           PA Parameter       SOLMOD3	          SOLMOD4	SOLMOD5	SOLMOD6
Brine	         Name		     (III)		   (IV)		    (V)      	     (VI*)
Salado	CCA SOLSIM	5.82 x 10-7		4.40 x 10-6	2.30 x 10-6	8.7 x 10-6
Salado     CRA04 SOLSIM	3.07 x 10-7		1.19 x 10-6	1.02 x 10-6	8.7 x 10-6
Salado    PABC04 SOLSIM   3.87 x 10-7             5.64 x 10-8       3.55 x 10-7         1.0 x 10-3
Salado    PABC09 SOLSIM   1.66 x 10-6             5.63 x 10-8       3.90 x 10-7         1.0 x 10-3
Salado     CRA14 SOLSOH   2.59 x 10[-6]             6.05 x 10[-8]       2.77 x 10[-7]         1.0 x 10[-3]

Castile	CCA SOLCIM	6.52 x 10[-8]		6.00 x 10[-9]	2.20 x 10[-6]	8.8 x 10[-6]
Castile     CRA04 SOLCIM	1.69 x 10[-7]		2.47 x 10[-8]	5.08 x 10[-6]	8.8 x 10[-6]
Castile   PABC04 SOLCIM   2.88 x 10[-7]             6.79 x 10[-8]       8.24 x 10[-7]         1.0 x 10[-3]
Castile   PABC09 SOLCIM   1.51 x 10[-6]             6.79 x 10[-8]       8.75 x 10[-7]         1.0 x 10[-3]
Castile    CRA14 SOLCOH   1.48 x 10[-6]              7.02 x 10[-8]      8.76 x 10[-7]          1.0 x 10[-3]

* See Section 24.2.3 of this CARD.

2014 CRA Formation of Colloidal Suspensions Containing Radionuclides
	Colloid formation can enhance the quantity of actinides contained in brine, and continues to be evaluated as an important group of waste characteristics.  In the CCA, DOE determined that four types of colloids may be present in the WIPP repository: Intrinsic, mineral fragment, humic colloids, and microbial.  These colloids are still modeled in the 2014 CRA.

      The colloid parameters were re-examined for the 2014 CRA (Appendix PA-2014, Section PA-1.1.11). Based on the recommendations of Reed et al. (Reed et al. 2013), the DOE updated the PA parameter properties CONCINT, PROPMIC and CAPMIC. More details are provided in 2014 CRA Appendix SOTERM-2014, Section SOTERM-4.6.

2014 CRA Waste Shear Strength Parameter Revised
      The parameter related to the waste shear strength was revised for the CRA-2014. DOE did experiments to directly measure waste shear strength. Herrick and Kirchner (Herrick and Kirchner 2013) recommended that the DOE included a modified distribution for the parameter BOREHOLE:TAUFAIL in the CRA-2014 PA calculations (Appendix PA-2014, Section PA-1.1.5). The DOE updated the parameter for the CRA-2014 from a log uniform distribution with a range of 0.05 - 77.0 Pa, to a uniform distribution with a range of 2.22 - 77.0 Pa.

2014 CRA Performance Assessment Parameters Related to Gas Generation
	Two changes related to the gas generation from the waste were implemented in the CRA-2014 PA: the refinement of the repository water balance (see 2014 CRA DOE Section <IP_ADDRESS>.1) and the update to the anoxic steel corrosion rate (see 2014 CRA DOE Section <IP_ADDRESS>.2).

	DOE continued to use used Latin Hypercube Sampling (LHS) in PA for the following gas-generation-related parameters:

 Inundated steel corrosion rate

 Probability of microbial degradation of plastics and rubbers (in the event of     microbial gas generation)

 Biodegradation rate of cellulosics, inundated and humid

2014 CRA Radioactivity in Curies of Each Isotope
	In the CCA, DOE indicated (Sections 3.1 and 3.2 of CCA Appendix WCA) that the radioactivity of each isotope is important to the performance assessment because it directly affects the waste unit factor (number of million curies of TRU isotopes in the WIPP inventory), which is the normalization factor used to calculate allowable releases for each radionuclide (see Table WCA-1 in CCA Appendix WCA).   DOE used the same approach in the 2014 PA as in previous CRAs (see 2014 CRA PAIR Tables 5-1 (CH) and 5-2 (RH).

2014 CRA TRU Radioactivity at Closure
	PAIR-2012 lists the DOE inventory at closure used in the 2014 CRA, based upon the December 31, 2011 cutoff date and waste inventory updates.  Kicker and Zeitler 2013, Table 1 indicates that the inventory estimate for the year 2033, which is the planned date for closure, is 2.06 x 106 Ci.  Thus, the waste unit factor (WUF) - the number of millions of curies of alpha-emitting TRU radionuclides with half-lives longer than 20 years used in the calculation of the EPA normalized unit  is 2.06 (Kicker and Zeitler 2013, page 8).   Out of the 179 radionuclides reported in the present inventory, 17 transuranic waste radionuclides contribute to the unit of waste used to calculate the WUF.

24.2.9 Evaluation of Compliance for 2014 Recertification (194.24(b)(1))

	For the 2014 CRA, EPA continued to focus on changes and new information in DOE's analyses that could impact disposal system performance based on changes in waste characteristics, such as solubility and gas generation.  Please refer to Technical Support Document in Support of Section 194.24 Evaluation of the Compliance Recertification Actinide Source Term, Gas Generation, Backfill Efficacy, Water Balance, and Culebra Dolomite Distribution Coefficient Values. (Docket ID No. EPA-HQ-OAR-2014-0609) for details on EPA's analyses of the topics below.

2014 CRA Solubility
	EPA finds the update to calculating solubility using variable brine volumes acceptable and addresses the issue of changes in organic ligand concentrations that occur with different volumes of brine. EPA also accepts the migration to the EQ3/6 code to calculate actinide solubility, which we believe is far more robust than the previous FMT code. Because the geochemical database used to calculate solubility had not been updated since 2002, EPA requested DOE use the latest data to update the database. However, The Agency has identified multiple flaws in the update DOE produced, including insufficient information regarding carbonate, borate, and organic complexation as well as hydromagnesite and Nd solubility. As such, EPA continues to accept the original database and urges DOE to continue its update of the geochemical database in consultation with the Agency.

	EPA has identified multiple problems with the uncertainty distribution DOE has provided, largely in DOE's inconsistent application of the criteria used to choose studies for this distribution. For example, the studies span a time frame with an arbitrary cutoff date, thereby decreasing the number of studies utilized in the analysis. Furthermore, DOE screened studies using only a limited range of pcH conditions, as well as borate and carbonate concentrations. Additionally, DOE included studies that overestimate +IV concentrations (e.g., Altmaeier et al 2004) and underestimated +III concentrations (e.g., Borkowski et al. 2009). After reviewing the uncertainty distribution for the 2014 CRA, EPA revised the uncertainty by providing a new set of criteria to search for solubility data used in the SEN4 sensitivity study, including considerations of both borate and carbonate as these have been found to be important in the WIPP. This resulted in a new uncertainty distribution that highlights DOE overpredicting +IV actinide solubility and underpredicting +III actinides. EPA will accept the revised uncertainty distribution because, even though releases increased with the Agency's modifications, releases still remained within compliance limits. This uncertainty is represented as a cumulative distribution function, with values shown in Table 24-10 below.

	The Agency has also identified deficiencies in DOE's assessment of solubility, particularly on the topic of plutonium oxidation state. We find this topic especially important as actinide oxidation state is a fundamental concept in plutonium solubility, with the +III state being more soluble than the +IV. DOE addresses uncertainty in which plutonium oxidation state will dominate the WIPP by including the +III oxidation state in 50% of PA realizations and +IV in the other 50%. Recent data compels EPA to believe that the +III state will dominate in repository conditions. In order to fully address this topic, we believe DOE should conduct an independent technical review prior to CRA-2019 and implement the recommendations provided by this review for the next PA.

Table 24-10.  Cumulative Distribution Function (CDF) Ranges Established by the Revised Actinide Solubility Uncertainty Analysis for the 2009 PABC.
                           Actinide Oxidation State
                              2009 PABC CDF Range
                               2014 PA CDF Range
                                      III
                                 -4.20 to 2.70
                                 -3.55 to 2.97
                                      IV
                                 -2.25 to 3.30
                                 -1.52 to 3.19
Source: Xiong et al. 2009, Table 7 and Table 11

2014 CRA Colloids
	DOE has performed multiple investigations on Nd(III), Pu(III), Am(III), Th(IV), and U(IV) intrinsic colloids and these results have been incorporated into the 2014 PA and the intrinsic colloid concentration parameter (CONCINT) (Reed et al. 2013). Many of the updates to the parameter, such as Th(IV) colloids, are based on an arithmetic mean to measured values in experiments over a narrow range of repository pcH values. EPA disagrees with this limited approach and believes that an upper-bounding value should be used from a wider range of pcH values in order to include more data and to represent the maximum intrinsic colloid concentrations.  Other colloid values, such as Pu(III), also appear to use an arithmetic mean when they should be utilizing an upper bound value.

      The Department has also conducted microbial colloid investigations on WIPP-indigenous microorganisms. From these investigations, DOE has redone how microbial colloids are calculated, which is a significant change to the previous model. In addition, updated sorption experiments were conducted for 2 hours in comparison to previous WIPP microbial adsorption tests over a period of 11 to 21 days. This time period may not adequately account for steady state and may underestimate colloids as it only accounts for biosorption without including bioaccumulation and biomineralization.

      EPA has identified major issues with the experiments performed to calculate intrinsic and microbial colloids and believes that these result in an underestimation on colloidal concentrations. While EPA continues to welcome updates to these parameters, in light of these major experimental and calculation issues, EPA rejects DOE's updates to the colloid model for the 2014 CRA and continues to accept the approach used in the 2009 CRA. For the 2019 CRA, DOE should continue to use the approach applied in the 2009 CRA until it provides an update EPA finds acceptable.

2014 CRA Production of Gas