RCIC GOVERNING EQUATION SCOPING STUDIES FOR SEVERE ACCIDENTS

摘要

A simplified but mechanistic governing equation for a reactor core isolation cooling (RCIC) system is developed to support investigations into severe accident mitigation strategies. Since the RCIC uses a single-stage impulse turbine, the model is essentially the application of Newton's Laws for a rotational system. Specifically, the control volume formulation of angular momentum conservation is used to derive an equation of motion that is simple enough to be implemented as user input for lumped parameter codes such as MELCOR. Preliminary testing of the RCIC equations and solution methodology has been completed. The equations are integrated into MELCOR input via control functions for scoping calculations; the derivation of the equations and solution methods are intentionally selected to facilitate this effort and the subsequent scoping calculations. The MELCOR model used for the test calculations contains simplified representations of the RCS and RCIC piping for a generic 2000 MW BWR. Scoping calculations of the accident scenario at Fukushima unit 2 are presented that show promising initial results. In conjunction with a literature review of RCIC turbine design, a key conclusion is established that the simplicity and pure-impulse design of the turbine facilitates computational modeling using simplified (lumped-parameter) momentum methods.