Activation analysis and dose assessment of reactor components are prerequisites for decommissioning, cost estimation, and radiation protection. At present, improving the accuracy of nuclear safety analysis remains the key area of research. To this end, based on the coupling method of Monte Carlo code and the fuel depletion code, the historical nuclide depletion and radioactivity of detectors in spent fuel assemblies, are calculated and analyzed, the law of typical nuclide activity with burnup depth is studied, and the dose rate distribution after the cooling of spent fuel assemblies, is evaluated. The results of the calculations are in good agreement with the actual measurements, and the error is within an acceptable range. Crucially, it was found that after a cooling period of 3 years, without applying shielding measures, the dose rate at a distance of 30 cm from the surface drops to below 1 mSvh-1. On this basis, the shielding design scheme of reactor detectors is proposed, which provides a reference for the research on the radiation shielding of a detector in the spent fuel assemblies.
Yan et al. (Thu,) studied this question.