DIAGNOSTIC METHOD AND DEVICE FOR REMAINING LIFE OF REACTOR

PURPOSE: To provide a method and device for diagnosing remaining life of a reactor by accurately grasping the irradiation dose of neutron at each part of a reactor and predicting the aging degradation of in-core structure. CONSTITUTION: A small neutron flux detector 44 is inserted from outside of a reactor pressure vessel 1 and used during reactor operation by positioning more than one measuring position in the vicinity of structure material arranged around fuel assemblies. The neutron flux detected at the measuring position by the small neutron flux detector 44 is measured with a neutron flux measuring device 56 and the measured value is recorded on a neutron flux recorder 58. By evaluating neutron irradiation dose to the structure material of in-core structure at the measuring position based on the measured record of the neutron flux accumulated in the neutron flux recorder 58 and the reactor operation record, the aging degradation of the in-core structure using degradation characteristics data of various structure material and remaining life is diagnosed.