LaBr3（Ce）元件破损在线监测关键核素确定及效率校准

Efficiency Calibration and Key Radionuclides Determination for On-line Fuel-rod Failure Monitor of LaBr3（Ce）

常用的元件破损在线监测方法受外在因素影响较大,以γ能谱中关键裂变产物核素比活度进行在线定量分析是一种可靠的元件破损监测方法。针对新型LaBr3(Ce)元件破损监测仪,设计了元件破损模拟实验,对逸出的裂变产物采用HPGe和LaBr3(Ce)探测器进行了对比测量。通过不同冷却时间γ能谱的核素分析,确定了135Xe,88Kr,138Xe,88Rb,138Cs等可作为LaBr3(Ce)元件破损γ能谱监测的关键核素。同时,制备了覆盖能量范围(250~2 400) keV,含60Co,137Cs,133Ba;241Am,152Eu;109Cd,88Y,57Co及24Na的4组放射性标准溶液,在建立的效率校准系统上,校准了LaBr3(Ce)在线监测仪的效率。在反应堆一次异常情况分析中,已校准的LaBr3(Ce)元件破损监测仪对关键核素的现场分析结果与HPGe的取样分析结果一致,表明效率校准结果准确,校准方法可靠。

The method of common fuel failure on-line monitoring is greatly influenced by external factors,but the on-line quantitative analysis with specific activity of key fission product nuclide in γ energy spectrum is a reliable fuel failure method. In this paper,for LaBr3( Ce) of a new type monitor,a fuel failure simulation experiment was designed,and the escape fission products was analyzed using HPGe and LaBr3( Ce) detectors respectively. Through the nuclide analysis results at different cooling time,it was determined the 135Xe,88Kr,138Xe,88Rb,138Cs and so on can be used as the key nuclides for γenergy spectrum method of LaBr3( Ce). At the same time,four groups of radioactive standard solutions including 60Co,137Cs,133Ba,241Am,152Eu,109Cd,88Y,57 Co and 24Na were prepared,the energy range was 250 keV to 2400 keV,The efficiency of LaBr3( Ce) on-line monitor was calibrated on the established solution circulation calibration device. Finally,in an abnormal situation of reactor,The results of the calibrated LaBr3( Ce) are in agreement with the results of sampling analysis of the HPGe spectrometer. It indicated that the efficiency calibration result is accurate and the calibration method is reliable.