A new method for accurate incore-excore nuclear instrumentation recalibration

For pressurized water reactors, it is required to recalibrate the correlation between the incore and excore nuclear instruments after each refueling shut down. In order to obtain the correlation between incore power distribution and excore detector response, the authors have intentionally caused a xenon oscillation at a power level of about 75% of rated power. This procedure, however, usually requires 10 to 20 hours, but should be as short as possible from the point of view of economics. In this report, a new method to reduce time interval for the data acquisition is described and the results are presented. In their method they acquired the necessary data during the escalation of power from 50% to 75%. They also acquired another set of data at 75% power using the conventional procedure for comparison. They obtained good agreement, thus their new method was proven to be useful