Estimation of FBR MONJU's Average Fuel Temperatures and Fuel-to-coolant Heat Transfer Coefficients using Trip-Test Data

Abstract

Fuel temperature is an important parameter in reactor safety. However, temperatures of fuel sub-assemblies in power reactors usually cannot be directly measured. A means therefore has been devised to use heat removed by coolant from fuel sub-assemblies following a reactor trip to estimate the pre-trip average fuel temperatures and fuel-to-coolant heat transfer coefficients. Sub-assembly coolant mass flow and outlet temperature measurements are used to determine the heat removed. After accounting for the contribution from release of stored heat from non-fuel components and from decay heat, the contribution due to release of fuel-stored heat alone during the trip transient can be inferred. Average fuel temperatures and fuel-to-coolant heat transfer coefficients of the FBR “MONJU” at 45% thermal power were estimated using this energy balance approach. The trip-test data derived estimates compared favorably with plant simulation code calculated values.

KEYWORDS:

• monju reactor
• reactor safety
• reactor trip test
• fuel temperature
• fuel-to-coolant heat transfer coefficient
• heat transfer
• fuel coolant interactions
• fuel coolants