Impact of actinide removal on waste disposal in a geologic repository.

The presence of actinides in spent fuel destined for a geologic repository such as the proposed Yucca Mountain Repository causes a substantial long term heat load, causes the radiotoxicity of the waste to remain high for tens of thousands of years, and contributes significantly to the long-term dose rate once waste packages begin to fail. Examples, mostly based on the current design of the proposed repository, are considered to illustrate the potential impact of actinide removal on each of these factors. The analyses show that removal of 90 to 99% of the actinides may significantly increase in the capacity of a repository. In addition, the radiotoxicity of the waste may be reduced to a value less than that of the uranium ore from which the fuel was manufactured within the 10,000-year regulatory period. For example, removal of 99.9% of the actinides reduces the radiotoxicity to a level less than that of the original ore in less than 400 years. Finally, removal of 99% of the actinides could reduce the peak long-term dose rate, estimated to occur after about 270,000 years, by as much as a factor of 60