Benchmark on Dose Rate Calculations for Irradiated Assembly

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The Task Force on Dose Rate Calculations for Irradiated Fuel Assembly was launched in 2015 to assess code predictions of dose rates from bare spent fuel assemblies and to benchmark multiple codes and validate them against available experimental data. This report provides details of the benchmark specifications, method and code characteristics, as well as a comparison and analysis of the calculation results.

The dose rate from a spent fuel assembly (FA) is an important attribute for two reasons. The first is to determine shielding and handling requirements to protect personnel working with spent fuel, while the second is related to non-proliferation aspects; the gamma and neutron radiation may serve as a self-protecting deterrent to theft for decades after the fuel is discharged. The United States Nuclear Regulatory Commission (US NRC) and the International Atomic Energy Agency (IAEA) consider the “self-protecting” dose rate to be 1 Sv/h at 1 m from the FA. The uncertainty inherent in dose rate calculations can be addressed by using conservative estimates. For personnel protection, an overestimation of the dose is conservative while for self-protection, an underestimation is conservative.