核电厂大修期间一回路冷却剂中放射性指标监测与控制

Monitoring and Control of Radioactivity index in the Primary coolant During Outage of Nuclear Power Plant

核电厂大修期间,从机组降功率至卸料结束,由于一回路冷却剂温度和压力不断降低、pH和氧化还原环境的改变,冷却剂中裂变产物和活化腐蚀产物比活度会发生系列变化。结合海南核电三次大修经验,阐述了降功率期间存在小缺陷燃料元件的氙和碘释放规律、一回路冷却剂中活化腐蚀产物的释放与净化过程、稳压器开人孔阶段一回路冷却剂放射性指标反弹现象及原因分析、卸料结束后乏池放射性指标反弹现象及原因分析,为后续机组大修期间一回路冷却剂放射性指标监督与控制提供借鉴。

During outage of nuclear power plant,from the unit downpowerto completed the discharge of nuclear fuel,the fission products and activated corrosion products in the coolant had a series of changes,because of the temperature and pressure were decreasingand changed in pH and REDOX environment of the primary coolant.Hainan nuclear power three times outage experiences were introduced in this paper,included the release rule of xenon and iodine when the fuel element had a small defect;the release and purification processes of activated corrosion products in primary coolant;the rebound phenomenon and cause analysis of radioactivity index of the primarycoolant when regulator opened the manhole;the rebound phenomenon and cause analysis of radioactivity index of thespent fuel tank when completed discharge of nuclear fuel.These experiences could provide references for the monitoring and control of the radioactivity index of the primary coolant during the following outages.