Criteria of Leakage Occurrence and Pressure Vessel Failure as Applied to Reactors

Abstract

This paper reports that the safety concept of a nuclear district heating plant (NDHP) reactor for emergency coolant losses is based on the realization of the leak before break criterion. Its acceptance became possible owing to the large experience of designing and operating the different type NPPs, as well as due to the modern achievements in the practical use of fracture mechanics. It is known that a metal's destruction is associated with the presence or birth and subsequent development of a crack under cyclic thermo-mechanical loading due to a plant's unsteady operating regime. That is why the study of the realization of hazardous states as the consequences of crack development up to local instability occurrence is the main task of investigations. The experimental part of the research program included tests of full-scale vessel models. This enabled us to reproduce with maximum possible accuracy the stress-strain state in the crack's mouth and to thereby remove the problem of carrying the results obtained over to the realone.