Calculation of radiation damage of key components of CSNS II target station

China Spallation Neutron Source I project was accepted by the state in 2018. At present, the beam power has reached 140kW. In order to further improve the output neutron strength of the target station moderator, a 500kW power upgrade plan has been proposed for China Spallation Neutron Source II. The target station is an important part of the spallation neutron source. In the target station, a large number of neutrons are produced by the spallation reaction between high energy protons and the target, these neutrons were moderated by the moderator and became neutrons for neutron scattering experiments. During operation, the target and other key components such as the target container, the moderator reflector container, and the proton beam window are irradiated by high-flux and high-energy particles for a long time, which will cause serious radiation damage. It is important to assess the accumulated radiation damage during operation to determine the service life of each component. At present, the physical quantities used to evaluate the radiation damage degree of materials include displacement per atom(DPA),H and He production. In this paper, the displacement damage cross sections of protons and neutrons and the H, He production cross sections for W, SS316 and Al-6061 materials were obtained by using PHITS. The effects of the Norgett-Robinson-Torrens(NRT) model and athermal recombination corrected (ARC) model on the calculation of displacement damage were analyzed. The results show that the cross section calculated based on ARC model is lower than that based on NRT model, because the NRT model does not take into account the resetting of the atom before reaching thermodynamic equilibrium. On this basis, DPA,H and He production of the key components of the target station operating for 5000h at a power of 500kW were calculated by combining the baseline model of the second phase target station of the spallation neutron source in China. The results showed that the yields of NRT-dpa, ARC-dpa, H and He produced by irradiation were 8.01dpa/y(In this paper,1y=2500MWh), 2.39dpa/y, 5110appm/y and 884appm/y, respectively. The radiation damage values of the target vessel were 5.34dpa/y, 1.92dpa/y, 2180appm/y and 334appm/y, respectively. The radiation damage values of the moderators and reflectors were 3.78dpa/y, 1.77dpa/y, 124appm/y and 36.7appm/y. The radiation damage values of the proton beam window are 0.35dpa/y, 0.19dpa/y, 962appm/y and 216appm/y. Subsequently, the life of each component is estimated by analyzing the radiation damage. These results are very important for analyzing the radiation damage of these parts, and constructing reasonable maintenance programs.