Gamma dose rate determination of TRR irradiated fuel assemblies

Abstract

Determination of gamma radiation dose-rate emitted from the irradiated nuclear fuel and prediction of the resulting dose rates are essential issues in the context of the design and construction of transport and storage casks for the spent nuclear fuels. This paper aims to evaluate the dose rate of gamma radiation emitted from the irradiated nuclear fuel in the Tehran Research Reactor (TRR) through different computational and measurement methods. First, four irradiated fuel assemblies with different operating histories have been taken into account, and the dose rate of emitted gamma radiation has been measured using Amber dosimeters at different distances from the fuel assembly. Then, an axial profile of gamma radiation dose-rate has been measured by placing 10 Amber dosimeters at the distance of 6 cm from each other along a 61.5 cm active length of the fuel assembly with a burnup of 56.45% of FIMA. The performed dosimetry experiment was simulated using the computational ORIGEN2.1 and MCNPX2.7 codes to verify the performance of the computational code in predicting the gamma radiation dose rate; the obtained results have been then compared with measurements. For calculating the dose rate, first, a spectrum and flux density of the gamma radiation emitted from the nuclear fuels with different irradiation histories at 18 energy groups has been accurately predicted by ORIGENT2.1, followed by calculating four fuel assemblies-induced dose by MCNPX2.7. Findings illustrate a very good agreement between the results from calculations and those of measurements.