Radioisotope flaw detection during the inspection of the NPS equipment

The radioisotope method for non-destructive inspection is widely used in the USSR because of its specific features and advantages, namely, the possibility to inspect the items made of various materials, with a wide range of thickness, or located in places access to which is difficult, in the case of absence of power supply, under the effect of high level radiation background, etc. The methods and means of radioisotope flaw detection are used for the following fields of nuclear power engineering: inspection of the equipments during the scheduled preventive and major repairs of nuclear power stations (NPS); during the mounting and assembling of nuclear reactors; and during the manufacture of NPS equipments on the shop scale. Some features and specifications of such facilities are described briefly. The All-Union Scientific Research Institute of Radiation Engineering carries out the investigations connected not only with the apparatuses for flaw detection, but also with their effective applications. As the results of the performed investigations, a method of optimizing instrumental parameters based on the sensitivity and expense, the influence of different factors upon the selected criteria, the radiation exposure dose rate, etc., were suggested. It must be noted that the economical effect produced by the optimization of the technical characteristics of the instruments intended for the inspection has been obtained, as a rule, without additional capital expenses. (Wakatsuki, Y.)