GAS GENERATION PHENOMENA IN RADIOACTIVE WASTE TRANSPORTATION PACKAGING

The interaction of radiation from radioactive materials with the waste matrix can lead to the deterioration of the waste form resulting in the possible formation of gaseous species. Depending on the type and characteristics of the radiation source, the generation of hydrogen may predominate. Since the interaction of alpha particles with the waste form results in significant energy transfer, other gases such as carbon oxides, methane, nitrogen oxides, oxygen, water, and helium are possible. The type of gases produced from the waste forms is determined by the mechanisms involved in the waste degradation. For transuranic wastes, the identified degradation mechanisms are reported to be caused by radiolysis, thermal decomposition or dewatering, chemical corrosion, and bacterial action. While all these mechanisms may be responsible for the buildup of gases during the storage of wastes, radiolysis and thermal decomposition appear to be the main contributors during waste transport operations. In this paper, we provide a review of applicable gas generation data resulting from the degradation of various waste forms under conditions typical for transport. The effects of radiolytic and thermal degradation mechanisms will be discussed in the context of transportation safety.