 Since NRC requires decommissioning to be completed within 60 years, ENTOMB is not usually chosen since not all activity will have decayed to an unregulated background level in that time.Decommissioning options for a retired nuclear plant may be chosen based on availability of decommissioning funds, operation of other reactors at the same site, or availability of waste disposal facilities.In 2004, 11 reactors were planned for DECON and 9 for SAFSTOR.