Radiolytic gas production during long-term storage of nuclear wastes

Gases produced by in situ radiolysis of sealed solidified nuclear wastes during long-term storage could conceivably breach containment. Therefore, candidate waste forms (matrices containing simulated nuclear wastes) were irradiated with 60Co-γ and 244Cm-α radiation. These forms were: cement containing simulated fission product sludges, vermiculite containing organic liquids, and cellulosics contaminated with α-emitting transuranic isotopes. For cement waste forms exposed to γ-radiolysis, an equilibrium hydrogen pressure was reached that was dose rate dependent. For α-radiolysis, equilibrium was not reached. With organic wastes (n-octane on vermiculite), H2 and traces of CO2 and CH4 were produced, and O2 was consumed with both radiations. Only energy absorbed by the organic material was effective in producing H2. At low dose rates with both α- and γ-irradiations, G(H2) was 4.5 and G(-O2) was 5.0. Also, equilibrium was not obtained. For cellulosic material, H2, CO2, and CO were produced in the ratio of 1.0:0.7:0.3, and O2 was consumed. With α-radiolysis, G(gas) was dose dependent; measured values ranged from 2.2 to 0.6 as the dose increased. Implications of all these results on long-term storage of radioactive waste are discussed. Some data from an actual nuclear wasteform are also presented