用于在线测量反应堆内热中子相对通量密度分布的闪烁体光纤探测器研究

闪烁体光纤探测器采用双探头甄别中子信号,利用252 Cf裂变源对探测器系统进行了测试,并与3 He计数管的计数进行了对比。在启明星1#上进行了热中子相对通量密度分布的测量,结合Geant4得到的不同能量段的中子转化率及MCNPX模拟得到的反应堆中子能谱,对探测器进行了相对效率刻度,测试结果与固体核径迹探测器测得的裂变率分布进行了对比。测量结果表明,闪烁体光纤探测器对于252 Cf中子源的响应基本符合点源的衰减趋势,与3 He计数管的测量结果符合较好。在启明星1#热区测得的热中子相对通量密度分布与固体核径迹探测器测量到的结果一致,快区测得的热中子相对通量密度分布与3 He计数管的测量结果及MCNPX的模拟结果符合较好。测量结果为闪烁体光纤探测器的研究提供了较好的实验依据。

Study on Scintillator Fiber Detector for Online Measurement of Thermal Neutron Relative Flux Density Distribution in Reactor

The scintillator fiber detector used two probes to identify the neutron signal.The detector system was tested by 252Cf fission source and was compared with the 3He counter.Meanwhile,the detector was used in Venus 1# assembly to measure the thermal neutron relative flux density distribution.The relative efficiency of the detector was calibrated with the neutron conversion rate from Geant4 code and neutron spectrum from MCNPX code.The results were compared with the fission rate measured by solid-state nuclear track detector.The measurement results show that the response of the scintillator fiber detector to the 252Cf neutron source agrees well with the attenuation of the point source,which is in good agreement with the counting rate of 3He counter.The relative distribution of the thermal neutron relative flux density measured at the Venus 1# thermal zone is consistent with fission rate distribution by the solid-state nuclear track detector.The same result of fast region is in line with the counting rate distribution measured by 3He counter and simulated by MCNPX code.The results provide important experimental data for the development of the detector.