核电厂堆用^(235)U裂变电离室性能影响因素模拟研究

Simulation Study of Factors Affecting Performance of ^(235)U Fission Chamber Used in Nuclear Power Plant Reactor

为了研制性能更加优异的核电厂堆用^(235)U裂变电离室,利用Geant4模拟软件研究了电离室外壳材料、^(235)U镀层厚度、^(235)U丰度及电极间距等参数对电离室性能的影响,并对^(235)U镀层样品进行了拉曼光谱分析。模拟结果表明:(1)1 mm厚的钛金属可作为堆用裂变电离室外壳;(2)^(235)U镀层最佳厚度约为3μm,镀层厚度的影响机制与“自吸收层”和“出射层”有关;(3)^(235)U丰度变化仅影响电离室探测效率,最佳镀层厚度不变;(4)当可电离气体压强分别为0.1 MPa和0.4 MPa时,电极间距分别大于等于6mm和3mm即可区分U原子衰变产生的a粒子信号。拉曼光谱分析结果表明镀层成分主要为U,O,与所建模型一致,保证了模拟结果的可靠性。

In order to develop the^(235)U fission ionization chamber with more excellent performance used in nuclear power plant,the effects of ionization shell material,^(235)U coating thickness,^(235)U abundance,electrode distance and ionizable gas pressure on the performance of the chamber were deeply studied by Geant4 simulation software.The simulation results show that:①1 mm thick titanium can be used as^(235)U fission ionization outdoor shell.②The optimal thickness of^(235)U coating is about 3 pm,and the mechanism of coating thickness is related to the“self-absorbing layer”and the“emitting layer”.③The variation of 235U abundance affects the detection efficiency of the ionization chamber,but has no significant effect on the optimal value of coating thickness.④For the selected 90%Ar+10%N2gas,when the pressure is 0.1 MPa and 0.4 MPa respectively,the electrode distance should be greater than or equal to 6 mm and 3 mm respectively so that the alpha particles generated by^(235)U decay can be excluded.The results of Raman spectroscopy shows that the composition of coating is Mainly U3 Og,which is consistent with the established model and ensures the reliability of the simulation result.