Reprocessing nuclear fuels of the future: a radiological assessment of advanced (Th,U) carbide fuel

The radiological dose associated with the use of (Th,U) carbide fuel in the core and thorium carbide in the blankets of a fast breeder reactor (FBR) was investigated. Analysis of the estimated dose due to reprocessing spent (Th,U) carbide fuel allows a direct comparison between the radiological consequences of the use of this fuel versus other candidates such as (U,Pu) oxide or carbide. Methodologies used were similar to those used in previous assessments of advanced FBR fuels. Results are calculated in terms of the potential dose commitment to a maximally exposed individual and to the general population living within 80 km of the operating plant. Tritium is found to be the principal contributor to dose commitment to total body for both the individual and the general population. Also contributing significantly to the dose are 14C, 137Cs, and 232U. Maximum individual dose is 3.1 mrem (total body), while dose to total body for the population is found to be 39 man-rem per 50 GW(e)-yr. A parametric analysis conducted to determine the effect on dose of varying the 232U content from 10 to 5000 ppM showed that at 5000 ppM 232U/U and with no additional modification in the effluent treatment system, dose to the total body of a maximally exposed individual is increased by a factor of 1.4, from 2.8 to 4.0 mrem. Another analysis was conducted to determine the effect of increasing the reprocessing plant confinement factor for 3H from 1 to 100. It was found that a confinement factor of 100 for 3H reduces the dose to total body (for individuals and populations) by a factor of approx. 3. It is concluded that reprocessing of (Th,U) carbide fuel for FBRs should meet applicable standards in terms of radiological impact during routine operations. In this context, little difference is seen to exist between the (Th,U) carbide fuels and earlier results for (U,Pu) oxide and carbide fuels