Development of an integrated methodology in support of remaining life assessment of Co-60 based gamma irradiation facilities

An integrated approach has been developed for the remaining life assessment of an irradiation facility. The probabilistic safety assessment (PSA) was performed for the plant to develop the quantified indicators of safety for various situations. PSA results were used to identify and prioritize the systems and components for deterministic assessment. The insight developed from various accidents world over has also been used as an input to investigate the likelihood of such failures and assessment of safety provisions against such failures. This paper discusses development of safety indicator in details and touches upon the other aspects as and when required. The objective is that the extended life of the facility should be predicted in a manner that likelihood of accident is low. As far as Cobalt-60 based Gamma Irradiation Facilities are concerned a survey of available literature shows that this study is unique in three respects; (a) it is for the first time that such a comprehensive re-assessment work has been performed on an irradiation facility. (b) In this study an integrated framework has been developed and applied for safety reassessment of Gamma Irradiation Plant (ISOMED) for Sterilization of Medical Products) one of the oldest, category - II type Cobalt-60 based Gamma Irradiation Facilities in the world and (c) A procedure has been developed in support of regulatory re-licensing and life extension of the Cobalt-60 based Gamma Irradiation plant. Based on this study eleven recommendations dealing with system retrofitting, change in operation and maintenance practices and further testing and qualification to get added confidence as part of life extension programme. Even though this study recommended life extension of ten years the first regulatory clearance of three years was given by the regulatory agency. (C) 2010 Elsevier B.V. All rights reserved.