The fact that the FISS tank wastes at Chalk River have not been solidified has led to speculation within the committee that these materials are seen as a hedge against a cutoff of HEU exports to Canada by the United States. HEU could be extracted from these liquid wastes and used to produce targets.27

At least two options exist for eliminating this waste. First, the wastes could be converted to LEU by adding natural or depleted uranium, a process known as “downblending.” Downblending would likely be a relatively simple step for the liquid wastes at Chalk River if there is enough space in the FISS tanks to accommodate additional material. Downblending solidified HEU wastes, which exist in calcined or grouted waste forms, would likely require mechanical treatment to introduce depleted or natural uranium so that the mixture could not be easily separated. These solid wastes might have to be dissolved before they could be downblended, which could be difficult. A substantial volume of radioactive waste would be generated from this process.

The second option would be to return the waste from processing U.S.-origin HEU to the United States for downblending and storage. The liquid wastes would have to be solidified before they could be shipped, but the existing solid wastes might be shippable in their current forms. Whether there is a current legal and policy framework to return these wastes to the United States is unclear to the committee.

Finally, in addition to the HEU wastes from Mo-99 production, Atomic Energy of Canada Limited (AECL) is also storing about 45 kg of HEU that was intended for use for Mo-99 production in the Maple reactors. This material has apparently become surplus in light of AECL’s decision to discontinue work on these reactors (see Chapter 10). At the time the present report was being completed, AECL had not announced whether it would return this HEU to the United States.


The third charge of the statement of task calls for an assessment of the progress that is being made by DOE and others to eliminate all use of HEU in reactor fuel, reactor targets, and medical isotope production facilities. The committee has developed the following findings and recommendations to address this task:

  1. The committee finds that DOE-NNSA, in collaboration with ANL/INL and with the assistance of IAEA through the RERTR program, has made substantial progress in converting reactors and targets. In particular,


A representative of IRE informed the committee that reprocessing of Mo-99 production wastes to recover HEU is an option for that organization as well if it cannot obtain fresh HEU.

The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement