It is estimated that nuclear reactions in the uranium in centimeter- to meter-sized veins consumed about five tons of U and elevated temperatures to a few hundred degrees Celsius. Most of the non-volatile fission products and actinides have only moved centimeters in the veins during the last 2 billion years. Studies have suggested this as a useful natural analogue for nuclear waste disposal. The overall mass defect from the fission of five tons of U is about 4.6 kilograms (10 lb). Over its lifetime the reactor produced roughly 100 megatonnes of TNT (420 PJ) in thermal energy, including neutrinos. If one ignores fission of plutonium (which makes up roughly a third of fission events over the course of normal burnup in modern human-made light water reactors), then fission product yields amount to roughly 129 kilograms (284 lb) of technetium-99 (since decayed to ruthenium-99), 108 kilograms (238 lb) of zirconium-93 (since decayed to niobium -93), 198 kilograms (437 lb) of caesium-135 (since decayed to barium-135, but the real value is probably lower as its parent nuclide, xenon-135, is a strong neutron poison and will have absorbed neutrons before decaying to Cs in some cases), 28 kilograms (62 lb) of palladium-107 (since decayed to silver), 86 kilograms (190 lb) of strontium-90 (long since decayed to zirconium), and 185 kilograms (408 lb) of caesium-137 (long since decayed to barium).