实验测量CFBR-Ⅱ堆启动Am-Be中子源的初始增殖倍数

Measurement of CFBR-Ⅱ Reactor’s Initialization Multiplication Started up by Am-Be Neutron Source

由于CFBR-Ⅱ堆原启动中子源252 Cf源半衰期较短,中子发射率已降低至无法满足使用要求,因此采用半衰期较长的Am-Be中子源替代。通过分别测量252 Cf源与Am-Be源在裸源情形下的计数率以及处于活性区中心时引起的泄漏中子计数率,建立比例关系,借助于252 Cf源对应的初始增殖倍数间接给出了Am-Be源对应的初始增殖倍数,为反应堆运行提供参数。

252Cf neutron source was CFBR-Ⅱ reactor＇s old start-up neutron source. Its neutron emissivity became too weak to be used because of short half life. Am-Be neu- tron source, which has long half time, was choosed to replace 252Cf neutron source. Neutron count rate arosed by bare 252Cf neutron source and bare Am-Be neutron source were measured respectively. Leakage neutron count rate of CFBR-Ⅱ reactor started up by these two kinds of sources were also measured respectively. According to these data, initialization multiplications of Am-Be source were gained in proportion to 252Cf source＇ s. These parameters were applied to CFBR- Ⅱ reactor＇s running.