压水堆核电厂燃料棒大破口情形下的辐射源项特征研究

Research on Radiation Source Term Characteristics with Large Fuel Rod Break of PWR Nuclear Power Plant

反应堆运行中,燃料棒出现大破口后,会引起燃料芯体材料的释放和一回路源项的明显上升,影响反应堆的安全运行。本文基于某核电厂的源项实测值进行燃料破损状态评估,分析表明堆芯燃料棒出现了大尺寸的破口,并出现了燃料的释放,与停堆后的破损检查结果基本一致。研究表明燃料棒大破口情形下的一回路源项存在以下特征:冷却剂中^(134)I源项的持续上升;典型裂变产物的活度谱与沾污铀的活度谱相近;功率瞬变时没有明显碘峰现象;冷却剂中可以检测出^(239)Np源项。这些规律可用于反应堆的燃料破损分析,有助于及时识别出堆芯出现燃料棒大破口的情形。

During the operation of the reactor,the large break of the fuel rod will cause the release of fuel core materials and the obvious rise of the source term in primary coolant circuit,which will affect the safe operation of the reactor.In this paper,the fuel damage status is evaluated based on the measured value of the source term of a nuclear power plant.The analysis shows that there is a large break in the core fuel rod and the release of fuel,which is basically consistent with the damage inspection results after shutdown.Research shows that in the case of a large break in the fuel rod,the source term of the primary coolant circuit has the following characteristics:there is the continuous rise of ^(134)I source term in coolant;the activity spectra of typical fission products are similar to those of contaminated uranium;and there is no obvious iodine peak during power transient;and ^(239)Np source term in coolant could be detected.These laws can be used to analyze the fuel damage of the reactor and help to identify the large fuel rod break in the reactor core.