The influences of Pu and Zr on the melting temperatures of the UO2–PuO2–ZrO2 pseudo-ternary system

Abstract

Specimens of (U, Pu, Zr)O2 were prepared as simulated corium debris that were assumed like debris generated in the severe accident of the Fukushima Daiichi Nuclear Power Plant and their melting temperatures were measured by the thermal arrest technique in order to evaluate the influence of plutonium and zirconium content on the melting temperature of the corium debris. From the evaluation, it was found that the influence of zirconium on the melting temperatures of both (U, Pu, Zr)O2 and (U, Zr)O2 was similar and that the melting temperature of (U, Pu, Zr)O2 had a local maximum value in the Pu-content between 0 and 20 mol%. The UO2–PuO2–ZrO2 pseudo-ternary phase diagram at 2900 and 3000 K was evaluated from the present experimental results and previously reported results.