In-pile irradiation of plutonium rock-like oxide fuels with yttria stabilized zirconia or thoria, spinel and corundum

In-pile irradiation and subsequent post-irradiation examinations have been performed for plutonium rock-like oxide (ROX) fuels with the ternary compon ent system of yttria stabilized zirconia (YSZ) or thoria (ThO2), spinel and corundum, to investigate the behavior of the ROX fuels under irradiation. Maximum neutron fluence was estimated to be similar to 8.2 x 10(24) m(-2) ( E < 0.6 eV) and burnup was measured to be 21-28% of the initial plutonium a toms by destructive chemical analysis. Phase equilibria, element distributi on over the phases and microstructure changes in the irradiated fuels were studied using X-ray diffraction, metallography, scanning electron microscop y and electron probe microanalysis. Relatively large swelling of the presen t fuels is discussed in connection with phase equilibria and microstructure changes. The measured isotopic compositions of Pu, Am and Cm in the irradi ated fuels are also given. (C) 1999 Elsevier Science B.V. All rights reserv ed.