Failure analysis in nuclear industry - specialities and ensuing strategies

Abstract

Failure of plant components, resulting in loss of production is a problem relevant to every industry; the nuclear industry is no exception. In this paper, a detailed analysis on various specialties relevant to failure analysis in nuclear industry, the methodologies applied to carry out failure analysis and the strategies adopted in preventing failures are given. Some of the specialties like (i) extent of damage and spread of radioactivity, (ii) safety implications, (iii) special materials, service conditions and novel damage mechanisms, (iv) radioactivity associated with failed components and necessity for handling them in post irradiation examination (radioactive hot cells) facilities, and (v) adoptability of suggested remedies under hostile environmental conditions are discussed. Important failure case histories pertaining to (i) thermal reactor fuel elements, (ii) coolant channels and end shield of pressurised heavy water reactors, (iii) delayed neutron monitoring instrumentation tubing, (iv) stainless steel dished ends, and (v) bellows used in high temperature circuits are given as examples. Finally, the strategies adopted to minimise prevent failures or damage to components in nuclear industry are discussed. The strategies highlighted in this paper include (i) quality assurance from design to decommissioning, (ii) use of weldment rather than parent material properties in design of welded components to prevent weld related failures, (iii) zero failure concept in the case of fuel elements, and (iv) in-service inspection with an objective to assess damage and determine residual life in an effective manner.