Primer Code: High Burnup BWR Fuel Behavior Modeling

In order to address high burnup mechanisms and to improve uranium utilization in current and new reactors designs, a new code has been developed and qualified by GNF to provide best-estimate predictions of the thermal and mechanical performance of (U, GD)O2 BWR nuclear fuel rods, the PRIME code. The PRIME code has been developed from the GESTR-Mechanical (GSTRM) code by (1) incorporating new models to address specific high exposure mechanisms (2) modifying existing material properties relations to reflect current materials properties data, including the effects of exposure where appropriate and (3) modifying existing us models to reflect high exposure experimental data that has become available since the original development of GSTRM. In particular, the PRIME code reflects the effects of burnup on fuel pellet thermal conductivity, Zircaloy creep, fuel pellet relocation, fission gas release, etc. The PRIME code is used by GENUSA (ENUSA and GNF) to perform the fuel rod thermal-mechanical design analysis of the advanced fuel designs such as GNF2. This paper will briefly discuss the new models in PRIME, qualification of the PRIME models and application of PRIME beyond the currently approved burnup limit. (Author)