Measurement of eigenvalue separation by using Position Sensitive Proportional Counter

In recent years, a long and slender Position Sensitive Proportional Counter has been developed. By using this proportional counter, spatial neutron flux distribution of nuclear reactor can be measured rapidly. Using of this characteristics, we intend to develop the experimental method evaluating eigenvalue separation as an index for reactor stability. The method based on spatial integrals of measured neutron flux was introduced. To verify this method, experiments were carried out at Kyoto University Critical Assembly. It was confirmed that eigenvalue separation can be evaluated within a relative error of 10%. (author)