A comparison of thermal hydraulic models for pressurized water reactors

Abstract

This thesis compares a new dynamic moving boundary thermal hydraulics fuel pin model (FUELPIN) to a known thermal hydraulics code (COBRA) for the following relationships: (1) Minimum Departure from Nucleate Boiling Ratio (MDNBR) versus time for transient conditions in a Pressurized Water Reactor (PWR) channel, and (2) Position of Minimum DNBR versus time for transient conditions. Relationships between MDNBR and position of MDNBR versus time were analyzed by comparing: (1) output of COBRA, a steady state thermal hydraulics model, with inputs from a PWR simulation code (CEPAC-L), (2) output of CEPAC-L linked FUELPIN. CEPAC-L computer model was shown to be a good simulation of a PWR during steady state conditions and a loss of all primary coolant flow casualty by comparison with an accepted PWR simulation code (CEPAC). FUELPIN was shown to predict larger thermal margins than COBRA for loss of all primary coolant flow transients in PWRs.