The recoil release caused by the collision of a neutron with a target nucleus has a significant impact on the analysis of activated corrosion product sources in a reactor. In water cooled reactors, a recoil release in the irradiated area can cause the activation corrosion products to leave the wall surface and enter the coolant, which then migrates to the non-irradiated area with the flow of coolant, thereby making the non-irradiated equipment also radioactive.

This study aims to analyze the influence of recoil release on the source term of activated corrosion product in reactor.

Based on the investigation of the mode of action of recoil release in a reactor, a calculation model and a program module for recoil release was established and integrated into the CATE program. Then, the effects of recoil release on the concentrations of activation corrosion products in the nuclear reactor were analyzed by using two approaches, one involved specifying a recoil release probability, while the other involved dynamically calculating the recoil release probability. Finally, values of the main activated corrosion products nuclides ⁵⁸Co and ⁶⁰Co in the core and steam generator before and after considering recoil release were calculated, and the impact of recoil release on the activation corrosion products and its implications for the actual operation of the reactor were explored.

The calculation results indicate that the recoil release probability decreases from 45% at the beginning of the simulation to 0.3% at the end of the simulation. However, the variation pattern of the activity ratio of ⁵⁸Co and ⁶⁰Co in the core and steam generator remains the same as that without recoil release. The activity ratio is 91% and 203% respectively, compared to the case without recoil release.

The total probability of recoil release is related to the thickness of the corrosion product layer and gradually decreases with the operating time of the reactor.