Burnup relative distribution measuring method, burnup relative distribution measuring apparatus, radiation signal distribution measuring apparatus, and burnup relative distribution measuring program

摘要

An upper detector 2 and a lower detector 3 that detect radiation facing at least one side surface A of the fuel assembly 1 irradiated with neutrons in the nuclear reactor are installed at predetermined intervals in the axial direction of the fuel assembly 1. Then, while relatively moving the fuel assembly and the upper detector and the lower detector along the axial direction of the fuel assembly, the distribution of the radiation signal is measured by the upper detector and the lower detector, and the upper detector By comparing the radiation signal distribution measured by multiplexing the same axial part of the fuel assembly with the lower detector, the soundness of the radiation signal measured by the upper detector and the lower detector is determined for each measurement. Thereafter, the relative burnup is calculated using the measured radiation signal, and the burnup relative distribution is measured. According to the present invention, the reliability of the measurement result can be ensured and the burnup relative distribution of the fuel assembly can be measured.