Study and Verification of Diagnosis Method for Secondary Neutron Source Breakage

The secondary neutron source used in the PWR nuclear power unit has a risk of breakage. Physical inspection of the status of the secondary neutron source is not possible at reactor power operation condition. According to the activation characteristics of the secondary neutron source, ¹²²Sb and ¹²⁴Sb are used as the characteristic nuclides to diagnose the damage of the secondary neutron source. The feasibility of the method for diagnosing the damage of secondary neutron source by using the on-line monitoring data of γ radioactivity of primary coolant and the specific activity of ¹²²Sb and ¹²⁴Sb in primary coolant is analyzed, the secondary neutron source damage diagnosis process is designed, and the secondary neutron source damage problem of the second generation improved 1000 MW PWR nuclear power unit is diagnosed using the above diagnosis methods. The verification results show that the specific activity change trend of ¹²²Sb and ¹²⁴Sb obtained by the primary coolant sampling analysis after the damage of the secondary neutron source should be consistent with the γ radioactivity change trend of the primary coolant monitored by the nuclear radiation monitoring equipment.Therefore, the secondary neutron source damage diagnosis method proposed in this study is effective.