基于脉冲中子源法的CiADS反应性测量蒙卡模拟分析

脉冲中子源法(PNS)是加速器驱动次临界系统反应性测量的一种重要技术。利用蒙卡软件建立CiADS次临界反应堆模型，模拟注入脉冲质子束的过程，获得的中子通量的时间演化谱。采用Python语言编程实现脉冲叠加过程，给出稳定缓发中子本底，实现脉冲中子源法的次临界反应堆的反应性测量模拟，给出脉冲周期注入下堆芯不同位置处的中子变化情况。利用PNS面积比方法模拟了CiADS堆芯在不同次临界度和探测位置下的反应性，并与基准数值做了对比。研究表明了该方法在较高的有效增殖因数($k_{\mathrm{eff}}>0.94$)下，可以较为准确地测量次临界反应堆的反应性，探测器在散裂靶附近位置的结果显示出较强的空间效应，需要开展实验验证，目前考虑测量结果的稳定性，宜布置在燃料外区或反射层组件中，可为下一步CiADS反应性测量技术方案制定有益的参考。

Monte Carlo Simulation Analysis of CiADS Reactivity Measurement Based on Pulsed Neutron Source Method

Pulsed neutron source method(PNS) is an important technique for the reactivity measurement of accelerator driven sub-critical systems. The CiADS sub-critical reactor model is established using Monte Carlo code to simulate the neutron transport process bombarded by pulsed proton beam, and the time spectrum of neutron flux is obtained. A code is developed by Python programming language to finish the pulsed neutron superposition process. It can obtain a stable delayed neutron background and the variation of neutron flux at different positions of the core under the continuously pulsed period proton injection. The reactivity measurement simulation of the sub-critical reactor by PNS method come true. Subsequently, the PNS method is used to simulate the reactivity of the CiADS core under different sub-criticalities and detection positions, and the results is compared with the reference values. It shows that this method can accurately predict the reactivity of sub-critical reactor at high effective multiplication factor ($ k_{\mathrm{eff}} >0.94$). The result nearby the spallation target shows a strong spatial effect. It needs to do experiments to figure it out.While, the outer fuel zone and the reflector assembly positions are more suitable for detector placement. Those conclusions can be used as a reference for the reactivity measurement of CiADS in the future.