Spent mixed oxide fuel rejuvenation in fusion breeders

A fusion breeder is presented for the rejuvenation of spent nuclear fuel. A (D, T) fusion reactor acts as an external high energetic (14.1 MeV) neutro n source. The fissile fuel zone, containing ten rows in radial direction, c overs the cylindrical fusion plasma chamber. The first three fuel rod rows contain Canadian deuterium uranium (CANDU) reactor spent nuclear fuel which was used down to a total enrichment grade of 0.418%. The following seven f uel rod rows contain light water reactor (LWR) spent nuclear fuel, which wa s used down to a total enrichment grade of 2.17%. This allows a certain deg ree of fission power flattening. Fissile zone is cooled with pressurised he lium gas with volume ration of V-coolant/V-fuel = 2 in the fissile zone. Sp ent fuel rejuvenation occurs through the neutron capture reaction in U-238. The new fissile material increases the nuclear quality of the spent fuel w hich can be described as the cumulative fissile fuel enrichment (CFFE) grad e of the nuclear fuel which is the sum of the isotopic ratios of all fissil e material (U-235 + (PU)-P-239 + (PU)-P-241) in the mixed oxide (MOX) fuel. Under a first-wall fusion neutron current load of 10(14) (14.1-MeV n/cm(2) s), corresponding to 2.25 MW/m(2) and by a plant factor of 100%, the CANDU spent fuel can achieve an enrichment degree of 1% after similar to 7 month s, suitable for reutilization in a CANDU reactor. LWR spent fuel requires > 15 months to reach an enrichment grade similar to 3.5%, suitable for reuti lization in a LWR. A longer rejuvenation period (up to 48 months) increases the fissile fuel enrichment levers of the spent fuel reactor to much highe r degrees (> 3% for CANDU spent fuel and over 5% for LWR spent fuel), openi ng possibilities an increased burn-up in critical reactors and a re-utiliza tion in multiple cycles. (C) 1999 Elsevier Science S.A. All rights reserved .