Research and Application of Radioactive Control Methods on the Primary Circuit of PWR Fuel Cladding with Loss of Air Tightness

During the operation of a pressurized water reactor nuclear power plant, a large number of radionuclides are generated by the fuel fission and contained within the fuel rod. When the fuel cladding suffers from a loss of air tightness, some inert gases and iodine in the gaseous form are easily released into the primary coolant, causing an abnormal increase in radioactivity in the primary circuit and associated systems, which may result in an increase in the radioactivity of the effluent that cannot be discharged. At the same time, the radiation dose of the plant in the nuclear island control area increased. In this paper, a method to control radioactivity in the primary loop following loss of fuel cladding air tightness is studied, and the operation mode during shutdown state transition is optimized, which has been applied in a domestic nuclear power plant. The application of the research results shows that when a domestic nuclear power plant experienced a loss of fuel cladding air tightness, I-131 in the primary coolant was controlled below 3.0E4Bq/L and Xe-133 below 1.0E6Bq/L before the last main pump was shut down and the reactor was uncovered. The qualified emission of radioactive effluents and the collective radiation dose of personnel did not increase significantly. The research results of this method have achieved good application effect, and have reference significance for similar types of reactors.