ANALYSIS OF REVERSE FLOW RESTRICTION DEVICE TO PREVENT FUEL DRYOUT DAMAGE DURING BOILING WATER REACTOR INSTABILITY

摘要

This paper analyses a new method for preventing Boiling Water Reactor (BWR) fuel damage due to the growth of unstable density wave oscillations to large magnitudes. The method uses a device called Reverse Flow Restriction Device (RFRD) to limit the growth of the density waves by limiting the magnitude of the oscillation of the coolant mass flow rate at the inlet of fuel bundles such that only upward flow is permitted. Detailed TRACE/PARCS simulations have been used to investigate the effect of RFRD on the flow rate as well as power oscillations of BWR. The results demonstrate that by adding the RFRD device flow reversal in fuel bundles could be substantially blocked and growth of the density wave beyond inlet flow reversal is thus prevented. The RFRD device also showed a modest impact on reducing the power oscillations. The use of RFRD device could prevent fuel dryout damage by preventing excessive high clad temperatures due to sustained dryout without timely rewetting. This device could be useful for accident scenarios when the reactor scram function fails so that it limits the consequences of unstable oscillations. In addition, this device could be useful in large Loss of Coolant Accidents (LOCA), a topic reserved for future studies.