Evaluation and modification of COMETHE III-J. Final report

The predictions of the COMETHE III-J fuel performance code, as modified by EPRI and subsequently by the S.M. Stoller Corporation were compared with experimental data from well characterized fuel rod performance. The comparison was made for the rods analyzed in EPRI's RP 397 program (AECL, ELP, Halden, Maine Yankee) and additional rods from Calvert Cliffs, Oconee, Oyster Creek and Inter Ramp. The major conclusion of the evaluation was that for current LWR fuel types, the predictions of both COMETHE III-J and COMETHE III-J Modified show reasonable agreement with the experimental data. However, this conclusion must be qualified by the fact that some of the validation data were previously used in the code modification process. Comparing the two versions over the entire data set, predictions of fission gas release and temperature are approximately equivalent. Modified III-J tends to give better prediction of clad creep strain