The design-basis, defense-related, transuranic (TRU) waste to be emplaced in the Waste Isolation Pilot Plant (WIPP) could, if sufficient H2O and nutrients were present, produce as much as 1,500 moles of gas per drum of waste. Gas production could pressurize the repository to lithostatic pressure (150 atm) and perhaps higher.
Anoxic corrosion of Fe and Fe-base alloys and microbial degradation of cellulosics are the processes of greatest concern, but radiolysis of brine could also be important. The proposed backfill additives CaC03, CaO, CuSO4, KOH, and NaOH may remove or prevent the production of some of the expected gases. We describe these processes and present preliminary results of laboratory studies of anoxic corrosion and microbial activity.