International Journal of Reliability, Quality and Safety Engineering Vol. 16, No. 6 (2009) 483–493 c  World Scientific Publishing Company DOI: 10.1142/S0218539309003526 RISK INFORMED DECISION MAKING USING MULTIOBJECTIVE OPTIMIZATION TECHNIQUE G. SRINIVAS Nuclear Power Corporation of India Ltd. Anushaktinagar, Mumbai-400094 gsrinivas@npcil.co.in A. K. VERMA Department of Electrical Engineering Indian Institute of Technology, Bombay, Mumbai-400076 akv@ee.iitb.ac.in A. SRIVIDYA Department of Civil Engineering Indian Institute of Technology, Bombay, Mumbai-400076 asvidya@civil.iitb.ac.in Nuclear Power Plant operations are guided by Limiting conditions of operations (LCO’s) laid out in the document referred to as the Technical Specifications (TS). This Techni- cal Specification is a legitimate framework approved by the Regulatory Bodies for the Safe operations of the Nuclear Power plants. In the past, the regulatory bodies used a deterministic approach as the basis for making decisions on safety issues and organizing the activities that they carry out. This was done by applying high level criteria such as the need to provide defence in depth and adequate safety margins. However with the availability of detailed Plant Specific Level-1 Probabilistic Safety Assessment (PSA), these limiting conditions need to be reviewed/revised based on the analysis results. This review of the LCO’s is not a trivial exercise if the entire solution space of the variables defining the variables has to be investigated. This paper reviews the case for revision of Surveillance test frequencies of the Emergency Core Cooling System injection valves, using the multiobjective optimization technique. Keywords : Level-1 PSA; technical specification; multi-objective optimization. 1. Introduction The Technical Specifications (TS) define the limits and conditions for safe operation of a nuclear power plant. These limits and conditions are mostly based on deter- ministic analyses and engineering judgment. Experience has (however) indicated operational and safety concerns with some of these requirements. Some elements of these requirements may be considered unnecessary or may not be conducive to the safety of the plant. Requirements are at times unnecessarily restrictive and 483