Organic reactivity analysis in Hanford single-shell tanks: Experimental and modeling basis for an expanded safety criterion

De-spite demonstrated safe storage in terms of chemical stability of the Hanford high level waste for many decades, including decreasing waste temperatures and continuing aging of chemicals to less energetic states, concerns continue relative to assurance of long-term safe storage. Review of potential chemical safety hazards has been of particular recent interest in response to serious incidents within the Nuclear Weapons Complexes in the former Soviet Union (the 1957 Kyshtym and the 1993 Tomsk-7 incidents). Based upon an evaluation of the extensive new information and understanding that have developed over the last few years, it is concluded that the Hanford waste is stored safely and that concerns related to potential chemical safety hazards are not warranted. Spontaneous bulk runaway reactions of the Kyshtym incident type and other potential condensed-phase propagating reactions can be ruled out by assuring appropriate tank operating controls are in place and by limiting tank intrusive activities. This paper summarizes the technical basis for this position.