Study on ¹³¹I Source Term in Reactor Coolant Under Shutdown Transient Condition

Abstract

¹³¹I activity in coolant under transient conditions is an important input for SGTR accident source term analysis in nuclear power plant, which directly affects whether the radioactive consequences of SGTR can meet the regulatory requirements. Based on the measurement results of ¹³¹I source term of several units in nuclear power plant A during shutdown, this paper study the variation law of ¹³¹I source term in the transient process of shutdown, analyzes the causes of ¹³¹I peak release, calculates the ¹³¹I release rate in the transient process, and obtains the following conclusions: 1) the ¹³¹I release rate based on the measured value is significantly lower than that used in the current safety analysis; 2) The larger the fuel rod break size, the smaller the peak factor of ¹³¹I in the primary circuit during transient.