Assessment Cases

A high-level summary of an effort to assess the predictive capability of BISON, a nuclear fuel performance code, is presented. This assessment was focused mainly on LWR fuel, and to a lesser degree, TRISO particle fuel. A comparison of BISON simulation results to a variety of experimental measurements of instrumented LWR fuel rods are shown. The source of LWR experimental data is primarily from the IAEA's FUMEX program. Benchmark simulation results of TRISO-coated particles are compared to BISON simulations. The TRISO benchmark simulations originate from the IAEA Coordinated Research Program. A brief discussion of material models and modeling approaches is also presented. There was a concerted effort to avoid model tuning to a particular set of experimental measurements. The material models and approaches were reviewed by the BISON team, and a subset of these were used for all the BISON simulations.

Overall, BISON simulations compare quite well with LWR experimental measurements and benchmark TRISO simulations.

BISON and its supporting software is updated and modified frequently. Structured after the regression testing system, an automated system runs all validation cases daily. Running the complete set of validation cases regularly provides the ability to determine how code modifications affect the comparisons. As this automated system evolves, each case will be compared to results from several prior runs and to the available experimental data. Statistical analysis and plotting will permit an evaluation of code validation status and an indication of whether code changes have adversely affected simulation/experiment comparisons. Systematic comparisons to experimental data will be made in each of the several validation areas.

For BISON to reach the status of being generally considered as a validated code and useful predictive tool, it is essential that the simulation-to-experiment comparison database expands and improves. As each new case is analyzed, it will be added to the set that are run daily. In addition, the validation system is available to users to permit addition of their own cases and allow them to analyze cases according to their specific validation requirements.