Comparison of the burnup characteristics and radiotoxicity hazards of rock-like oxide fuel with different types of additives

Burnup characteristics of rock-like oxide (PuO2-ZrO2: ROX) fueled LWR have been studied with an additive ThO2, UO2 or Er2O3. A ROX fueled LWR core has reactivity coefficients and burnup reactivity swing problems, which can be mitigated by these additives. From the burnup calculations of the ROX fuel ed LWR. it was found that the additive ThO2 causes a few percent decrease i n Pu transmutation in ROX fuel, while the additive UO2 or Er2O3 decreases i t largely The production of Am-241, which is a parent of long-lived Np-237, is smaller in ThO2 added fuel than that in UO2 or Er2O3 added fuel. Howeve r, the productions of Am-243 and Cm-244 are more in ThO2 added fuel than th ose in UO2 or (ErO3)-O-2 added fuel. The long-lived fission products (LLFPs ) production in ThO2 added fuel is nearly the same as that in UO2 added fue l, and smaller than that in Er2O3 added fuel. As a result of these Pu trans mutation and minor actinides (MAs) and LLFPs productions, ingestion radioto xicity hazard index of ThO2 added ROX spent fuel is lower than that of UO2 or Er2O3 added ROX spent fuel, except at the 10(5) years cooling. From thes e calculations, ThO2 is recommended to be used as the additive in ROX fuel.