Improvement of the “best representativity” method toward an industrial application

Abstract To judge the applicability of a critical experiment, it is necessary to confirm the similarities of the experiment with actual reactor conditions or equipment. The concept of the “representativity factor” has been well adopted since the late 1970’s, particularly for fast breeder reactors (FBRs) and future reactor studies. We extended this concept to the design of a light water reactor (LWR) system. In the first study, a new numerical evaluation method and a calculation system were developed and qualified. In the second study, an application calculation was conducted to validate the method. Based on the method, calculations were performed to correct the infinite neutron multiplication factor of a pressurized water reactor fuel assembly with using three kinds of critical experiments. The representativity factor became closer to unity. A correction of the infinite multiplication factor was well achieved. In this study, for aiming at an industrial application of the method, the method was improved to be more suitable for the single experiment case. In addition, a modification of the calculation procedures was proposed to prevent a very large increase of the final combined uncertainty. Furthermore, to validate the method, calculations were conducted according to ICSBEP 2010 data disk with utilizing critical experiments that were performed at different critical facilities. Simultaneously, with “SCALE 6.1.2” system and “ENDF/B-VII” 238G library, the applicability of the method was studied. All calculation results are shown and explained with physical considerations.