Abstract: An object of the present invention is to provide a method of operating a nuclear reactor, which is capable of effectively suppressing the initiation and growth of SCC of reactor structural members of a BWR without increasing the dose rate of a main steam system and thereby reducing radioactivity of reactor water, by carrying out, at a suitable period, a control for injecting hydrogen in the reactor water while adjusting the pH of the reactor water on the alkali side.

Abstract: A method and an apparatus for estimating the remaining service life of an object by measuring the physical quantity of a sample and which are applicable to a nuclear reactor. A plurality of model samples are experimentally prepared by preliminarily disposing a material having substantially the same composition as the object to be subjected to the estimation in an environment substantially the same as the object and measuring the physical quantities of the model samples in relation with exposure times. From this experiment, a relationship between the exposure time and the physical quantity under such an environment is obtained. Further, a critical exposure time which will cause an unstable fracture of a material of an actual sample, which is made of a material substantially the same as the object and placed in substantially the same environment as the object, is preliminarily obtained from the relationship between the exposure time and the physical quantity for the model samples.