Pulse irradiation tests of rock-like oxide fuel

Pulse irradiation tests of special oxide fuel designed for plutonium dispos al, called rock-like oxide (ROX), have been conducted in the Nuclear Safety Research Reactor (NSRR) to investigate the transient behavior of ROX fuel under reactivity initiated accident (RIA) conditions. An uranium free ROX, (Zr,)O-2-MgAl2O4-PuO2, is proposed for once-through use of Pu in light wate r reactors. However, because of smaller negative Doppler and void reactivit y coefficients in the ROX fuel, higher peak fuel enthalpies are expected un der RIAs than for UO2 fuel. Thus, the tests of simulated ROX, in which Pu w as replaced by U for easier realization, were conducted to a peak fuel enth alpy of 0.96 kJ g(-1) (230 cal g(-1)): which is above current Japanese safe ty limits for UO2. The transient behavior of the simulated ROX fuel was qui te different from that of UO2, because of its different thermo-physical pro perties. Fuel failure was associated with fuel melting at peak fuel enthalp ies of 1.63 kJ g(-1) (390 cal g(-1)) to 2.22 kJ g(-1) (530 cal g(-1)). Sign ificant mechanical energy generation, the reason for the limit, however, wa s not observed. (C) 1999 Elsevier Science B.V. All rights reserved.