Fuel rod stored energy estimates for the LOFT LOCA tests

Abstract

Loss-of-coolant accident (LOCA) tests performed in the Loss-of-Fluid Test (LOFT) Facility provide an important data base for verification of thermal-hydraulic computer models. An important parameter which must be known for LOCA model evaluation is the initial fuel rod stored energy prior to initiation of a LOCA test. While fuel rod surface temperatures are measured in the LOFT tests, pellet internal temperatures are not; thus, the fuel stored energy must be estimated via computer predictions. A method has been evaluated to estimate fuel rod stored energy in the LOFT experiments based on the measured post-critical heat flux (CHF) cladding temperature rise. This summary compares the stored energy as determined using the post-CHF cladding temperature evaluation to that calculated from best-estimate fuel code predictions for LOFT LOCA Tests L2-2 and L2-3. These tests simulated a large break in the reactor vessel inlet coolant pipe of a pressurized water reactor