Measurement of Coupling Coefficient by Variance-to-Mean Ratio Method, and Investigation of Its Space-Dependence

在核燃料机组的临界安全管理中，一个重要的问题是评价核燃料机组间的中子干扰效应。为了衡量这种影响，我提出了在耦合堆中使用代表堆芯之间耦合强度的耦合系数。本研究采用方差-均值比法，并以近畿大学原子能研究所的Argonout型耦合堆为例，对该方法的有效性进行了研究。测量系统的死区时间在数据处理中起着重要的作用。推导了考虑死区影响的新公式，并验证了其有效性.数据采集技术与数据记录器。然后，发现为了获得良好的统计数据，需要超过40，000个采样点。但是，尽管采用了这种技术，在大的门宽下，很难在实际的捕获时间内获得足够的采样点.测得的耦合系数为1.99 ± 0.53美元，与二维双能群扩散理论计算值2.33美元在实验误差范围内一致。

In the management of criticality safety, an important problem is to evaluate the effect of neutron interference between nuclear fuel units. As a measure of this effect, I have proposed to use the coupling coefficient representing the strength of coupling between cores in a coupled-core reactor.In this study, the variance-to-mean ratio method was employed, and its availability was investigated with the use of the Argonout-type coupled-core reactor at Kinki University Atomic Energy Research Institute.The following results were obtained through this study.1. The dead-time of a measuring system plays an important role in data processing. Then, the new formula taking account of the effect of dead-time was derived, and its validity was confirmed.2. The data acquisition technique with a data-recoder was employed. Then, it was found that the sampling points more than 40,000 were required in order to get good statistics. But, in spite of this technique, it was difficult to obtain the sufficient sampling points within practical acquisition time at large gate width.3. The coupling coefficient measured was 1.99+0.53 dollars, and it agreed with the calculational value of 2.33 dollars within the experimental error, which was evaluated by two-dimensional, two-energy group diffusion theory.