The radiolytic and radiolytically induced gas generation in Hanford waste tanks

A task force operating in ANL/CHM has been developing a mechanistic understanding of the radiolytic processes that lead to the generation and retention of gases within tanks of radioactive waste at the Hanford site. This chemistry is one of the important factors that must be considered in devising remediation procedures to eliminate the great potential hazard of these tanks. A quantitative description of much of the chemistry involved in the production of H{sub 2} and, to a lesser extent, in the production of N{sub 2}O has been achieved. Direct radiolytic generation was experimentally quantified and this new information was utilized in computer modeling to provide predictive capabilities so that changes of chemical composition of various waste tanks under different remediation procedures could be assessed. Oxygen in the waste solutions is effectively consumed upon irradiation and thus is of no concern. The mechanism of the radiolytic degradation of the chelators was established. The end products are simple organic molecules, in particularly, formaldehyde and glyoxylate, that are very efficient in the thermal generation of H{sub 2}