DEVELOPMENT OF A 'BEST REPRESENTATIVITY' METHOD FOR MEASUREMENT DATA ANALYSIS -APPLICATION TO CRITICAL EXPERIMENT SIMULATING PWR AT THE TOSHIBA NCA FACILITIY

摘要

For the qualification and the validation of the nuclear calculation codes, the precise measurement data from the nuclear critical experiments are both necessary and profitable. At Toshiba, we have a tank type light water moderated nuclear critical facility named Toshiba Nuclear Critical Assembly (NCA). After the recent realization of the collaboration between Toshiba and Westinghouse, Toshiba NCA is becoming the facility of choice utilized both for BWR and PWR experiments and research. In a PWR core, the boric acid (H3BO3) is employed to control the core reactivity. At the operating conditions, the light water moderator in the core is under high pressure (15.8 MPa) and at high temperature (-580 K), thereby the water density is about 0.7 g/cm3 which is much smaller than the density of room conditions. In order to closely simulate these specific operating PWR situations, polystyrene blocks containing the boron carbide (B4C) material have been developed. In addition to these preparations for the experiments, when we judge the value/worth of the experimental data, it is quite important to evaluate the experiment similarities to the objective of the actual reactor conditions or actual reactor equipment. Recently a concept of "the representativity factor" is often used in the nuclear critical experiment field. In accordance with this concept, a new numerical evaluation method and a calculation system have been developed to understand the representativity of NCA experiments to the target reactor conditions. In this paper this mathematical method and simplified numerical results are presented.