An overview of reactivity initiated accident behavior of rock-like fueled pressurized water reactors

Reactivity initiated accident (RIA) analyses of plutonium rock-like oxide ( ROX) fueled PWRs have been carried out with the point kinetics calculations . As a result, the analyses have shown a very severe transient behavior of the ROX fueled PWR, which is unacceptable without any improvement. It was a lso found that the RIA behavior of ROX fueled PWRs can be improved by incre asing the negative fuel temperature coefficient (alpha (f)). For this impro vement, the additives in the ROX fuel such as UO2 and ThO2 were considered, as well as a ROX assembly partial loading UO2 core. With UO2 additive, it was successful to have satisfying alpha (f) and RIA behavior of ROX fuel co re, while the partial loading core must be further improved. Besides the RO X-PWR RIA analytical study, the actual behavior of the ROX fuel pin under R IA condition has been experimentally investigated at the Nuclear Safety Res earch Reactor (NSRR) of JAERI. Though the ROX fuel pin failure mechanism wi th fuel melting seems quite different from that of UO2 pin with cladding me lting, the ROX pin failure threshold was found to be roughly the same as th at of UO2 in terms of accumulated energy per unit fuel volume. (C) 2001 Pub lished by Elsevier Science Ltd. All rights reserved.