METHOD FOR MEASURING DISTRIBUTION OF VOID RATE IN BOILING WATER REACTOR

摘要

PPROBLEM TO BE SOLVED: To obtain a method for measuring void rates which makes it possible to easily measure a void rate inside a core and an effective void rate on the outer periphery in a boiling water reactor with an existing actual device without installing any new jigs for measurement, producing distortions of neutron flux or output or causing the loss of the reactivity in the core. PSOLUTION: Given a threshold energy causing an activation reaction by fast neutrons whose energy is a certain value or higher, the reactivity ratio[(F)/(S)] of the fast neuron activation reactivity (F) of fast neutron threshold reaction nuclides to the slow neutron activation reactivity (S) in the activation of slow neutrons consisting of thermal and epithermal neutrons through the absorption of them is measured to a void rate measurement position (x) and a position (0) of a known void rate. Then, the reactivity ratio R=[(Fx)/(Sx)]/[(Fo/So)] of the reactivity ratio (Fx)/(Sx) of the void rate measurement position (x) to the reactivity ratio (Fo/So) of the position (0) of the known void rate is determined and is used together with a calibration curve found otherwise to determine the axial distribution of void rates of the reactor. PCOPYRIGHT: (C)2006,JPO&NCIPI