Pressurized water reactor coolant pump locked rotor analysis methodology using RETRAN-02 and FREY

摘要

The reactor coolant pump locked rotor analysis methodology developed by Taiwan Power Company for application to pressurized water reactors (PWRs) is presented. The proposed locked rotor analysis methodology utilizes two computer codes developed or sponsored by Electric Power Research Institute (EPRI): system transient analysis code RETRAN-02 and fuel rod evaluation code FREY. RETRAN-02 determines the transient system responses and the peak reactor coolant system (RCS) pressure. FREY utilizes the core power and core flow transients generated by RETRAN-02 to evaluate the peak clad temperature (PCT) during the transient. FREY is needed for PCT calculations since the conservative modeling assumptions with respect to the PCT can be different from those with respect to the peak RCS pressure. Both computer codes have been properly qualified by benchmarking against the vendor's results. An asymmetric-flow condition would be developed following the initiation of the locked rotor incident. Although there is no guidance in EPRI's 'Reactor Analysis Support Package, Volume 3: PWR Event Analysis Guidelines' for the modeling of incomplete mixing at the downcomer and the lower plenum, it was observed from the sensitivity results that the maximum RCS pressure is very sensitive to the amount of mixing. Thus, a splitcore model is required to adequately simulate the asymmetric-flow effect.