Computational neutron emission spectrometry and radiation assessment in VVER-1200 reactor nuclear fuel

Abstract

To ensure long-term and trouble-free operation, the reactor fuel is modified by introducing various homogeneous and heterogeneous additives. This modified fuels exhibit satisfactory performances under irradiation at elevated temperatures and burnup levels. However, the challenges related to radiation safety during the handling of fresh and spent nuclear fuel remain unresolved. In this study, neutron emission spectra and effective doses for VVER-1200 reactor fuel containing a heterogenous distribution of natGd2O3 and Am2O3, microspheres were calculated. Unlike in the case of homogenous variants, this design did not reduce the thermal conductivity of the fuel and positively affected the core neutronics and thermophysics. Comparing the radiation characteristics of fresh FAs revealed a considerable increase in the neutron (more than 3.7∙102 times at a distance of 10 cm from the FA) and photonic (about 104 times) components of Am–containing fuel compared to U and U–Gd fuels. The yield and effective dose of neutrons emitted from spent Am-containing fuel is two times higher than that of uranium–based fuels. When calculating the dose, it is important to consider the energy spectrum of (α, n) neutrons in Am2O2 microcapsules. The findings of this study provide insights into the development of procedures and regulations for manufacturing and post-irradiation handling of new fuel in reactors.