Inspection proposals — a regulatory view

Abstract

The United Kingdom safety legislation places absolute liability on the licensee as regards the safe design and operation of nuclear installations. In this paper, the approach taken by HM Nuclear Installations Inspectorate (NII) in assessing the structural integrity safety case for the Sizewell B PWR reactor pressure vessel and the other incredible failure components is described. Attention is focused on the ultrasonic inspection proposals which must satisfy the NII Safety Principles in terms of the Special Case Procedure, appropriate inspection standards, the setting of realistic inspection goals, the extent of the validation, redundancy and diversity to be built into the inspection programme and the avoidance of common mode effects. It is argued that these safety concepts should be incorporated into the appropriate codes and standards and whilst these measures may appear excessive when compared with past practice, the increase in safety and the case of in-service inspection in later years, for outweigh the initial costs.