Preliminary Radiation Field Analysis of HTR-PM600 Main Shield Based on Monte Carlo Method

Radiation shielding calculations are essential throughout the lifecycle of nuclear power plants. The HTR-PM600 builds upon the technological advancements of the High-Temperature Gas-Cooled Reactor Pebble-Bed Module (HTR-PM) demonstration project. Its modular design concept holds significant promise for the future deployment of commercial nuclear power plants. The Monte Carlo method offers an efficient approach for simulating the transport of particles, such as photons and neutrons, through the complex geometries within a nuclear facility. In this study, a three-dimensional geometry model of HTR-PM600, based on new shielding design, is developed using the Constructive Solid Geometry (CSG) method. The Monte Carlo code RMC is employed for critical coupled neutron-photon calculations within the HTR-PM600 core, enabling detailed mapping of neutron and photon dose rate distributions. The comprehensive composition of core materials, encompassing over 400 nuclides, along with the gamma spectra of fission products, are determined using the self-developed depletion code NUIT. Fixed-source calculations are conducted to complement the dose rate analyses after core shutdown. Shielding calculations are performed at various core operating stages, followed by comparative analyses to identify factors influencing dose rates in the core area. This study utilizes up-to-date methodologies and data, with the findings serving as a valuable reference for the engineering application of future HTR-PM600 nuclear power plants. (authors)