Core design study on rock-like oxide fuel light water reactor and improvements of core characteristics

A rock-like oxide (ROX) fuel - LWR burning system has been studied for effi cient plutonium transmutation. A zirconia based ROX (Zr-ROX) core has probl ems such as a small negative Doppler coefficient and a large power peaking factor, which causes severe transients in accidents and high fuel temperatu re even under nominal condition. For the improvement of these characteristi cs, two approaches were considered: the additives UO2, ThO2 and Er2O3, or a heterogeneous core with Zr-ROX and UO2 assemblies. As a result, the combin ation of the additives UO2 and Er2O3 is found to sufficiently improve the a ccident behavior, while a further power peaking reduction may be necessary for the Zr-ROX + UO2 heterogeneous core. The plutonium transmutation rate i s extremely high in Zr-ROX assemblies in the heterogeneous core, to be more than 85% and 70%, respectively for weapons- and reactor-grade plutonium. T he plutonium transmutation rate becomes smaller in the full-ROX core with t he UO2 or ThO2 additive, but the annual transmutation amount of plutonium i s large, in comparison with the full-MOX fuel core. (C) 1999 Elsevier Scien ce B.V. All rights reserved.