高浓铀金属临界装置缓发中子有效份额测量

缓发中子有效份额βeff是反应堆动态特性的重要参数,也是相对反应性与绝对反应性之间的转换桥梁,对于以反应性作为宏观参数的检验工作具有重要意义。测量采用基于Rossi-α方法的Nelson数法开展了快临界装置βeff的实验研究。通过采用铅屏蔽、更薄的6Li玻璃闪烁体、脉冲幅度甄别三种措施,降低了γ射线对测量的影响。实验中测量了反应堆从-60￠到缓发临界之间的7个状态,最终测量得到βeff值为0.006 66,不确定度为7.88%;与理论计算数值偏差为2.15%。测量结果与理论值符合良好,表明了测量方法的有效性。

Measurement of effective delayed neutron fraction in highly enriched uranium metal critical assembly

Effective delayed neutron fraction eff is an important parameter in dynamic behaviour of nuclear reactor. Besides, eff has the role of the conversion factor between a relative unit and an absolute unit in reactivity scale, which is important for examining work of macroparameter according to reactivity. An experiment was performed to measure theeff in a fast critical assembly using Nelson number method which is based on Rossi- method. Using lead for shielding, adopting the thinner 6Li glass scintillator and pulse amplitude discrimination, the influence of is decreased. The measurements were carried out for reactivity ranging from -60 ￠ to delayed critical state. The final measured value ofeff is 0.006 66, with 7.88% uncertainty, of which the deviation is 2.15% compared with the theoretical value. Because of the good matching between the measured value and the theoretical value, the experiment method is demonstrated to be effective.