Abstract: According to the investigation of outage deposition source term of Unit 1 of Fuqing NPP, the surface activity, dose-rate contribution of ⁵⁸Co and ⁶⁰Co on the inner wall of primary loop pipeline and their variation with time are analyzed. Meanwhile, the formation, deposition and existence form of activated corrosion products in this PWR are introduced. By analyzing the influence of the main pump shutdown on the oxidation operation effect and the radiation level of the SG channel head during the outage 201, combined with the characteristics of the solubility change of the corrosion products in the acidic oxidation environment, a suggestion for improving the shutdown timing of the main pump to improve the oxidation operation effect is proposed. In addition, the influence on source term by the introduction of cobalt metal particles into the primary loop system caused by valve seal face maintenance is analyzed. It is suggested that strict measures should be taken to control the valve seal face maintenance process to reduce ⁵⁹Co entering into the primary loop system.

Key words: PWR, investigation of the source term, activated corrosion products, cobalt, oxidation operation, main pump, valve hard face