Evaluation of the programme for long-term operation for safety requirements during operational safety

Abstract

The programme for long-term operation (LTO) in the nuclear power plant (NPP) installations is one of the essential nuclear safety concerns. It may be defined as an operation beyond an established time frame set forth by, for example, licence term, design, standards, licence and/or regulations, which has been justified by safety assessment, with consideration given to life-limiting processes and features of systems, structures and components (SSCs). The objective of this paper is to provide evaluation and information on key technical considerations and activities to ensure safe LTO of pressurised power plants in accordance with regulatory requirements. We study the case of VVER-440/213 units at Paks NPP, Hungary, which is limited to the design lifetime of 30 years. Prolongation by additional 20 years of the operational lifetime is feasible. Paks NPP is a pioneer considering the power uprate and preparation of LTO of the VVER-440/213 design. Systematic preparatory work for LTO of Paks NPP has been started in 2000. This paper takes into account approaches, practices and experience of IAEA member states pursuing LTO. It aims to support the operating organisations in demonstrating the safety of their NPPs during LTO and the regulatory bodies in verifying their safety.