Risk indicators at Cofrentes NPP

Following the tend to try to find indicators to show the excellence in the performance where Nuclear Power Plants are currently involved, Cofrentes NPP are managing several indicators related with risk. The concept of risk is classically associated with the product RISK = PROBABILITY * DAMAGE So what a risk based indicator will show is the probability of having a 'damage'. Speaking about a period of time, we will have frequencies of having 'damages'. What is call 'damage' can be differently interpreted depending of what we concern. In western NPP is very extended the concept of 'core damage', meaning the loss of fuel integrity, as a final state to avoid. This have carried in most of western NPP to develop a Probabilistic Risk Assessment (PRA/PSA), that using technical based in fault trees and event trees models, looks for the frequency to reach core damage. The PSA in Cofrentes NPP has been deeply applied to find weakness in the design and procedures, prioritizations in maintenance activities, quality assurance requirements, justifications to continued operation, and others. A Risk Monitor based in PSA models (and so monitoring the Core Damage Frequency) has been developed and is currently installed in the Control Room to help operators to control the risk associated with each configuration of availability or unavailability of equipments. This PSA Monitor is the source for some indicators that Cofrentes NPP has defined and are sharing with IAEA trying to find an standard. Maximum Core Damage Frequency reached and accumulated annual probability is calculated and compared with expected values and with predefined limits. As the PSA in Cofrentes NPP is only for at power Operations, there has been developed a methodology based on NUMARC 91-06 to measure and control the risk during shutdowns. The 'damage' here is a concept related with the safety functions. Some coefficients are applied to each configuration according with how the safety functions are fulfilled (defense-in-deep). Each outage is scheduled taking in care these indicators, and then a real following of the tasks shows the evolution of these index along the outage. It is notorious how this method has improved the safety during the outages in the last years. Finally, another risk that is being measured in Cofrentes NPP is related with the loss of production, translated into money. Several elements are joined into this risk analysis: generation and prize, availability, regulation and environment. Each one of this elements is quantified through applicable factors, for example to quantify prize is taken into account cost of fuel, residues, salaries, operation and maintenance costs, prize of the generated kWh. The risk of having a core damage is also translated into money and taken into account in this analysis. Each factor is measured according with historical data when available or industry experience. As a result Cofrentes NPP is creating a global methodology to learn the most important contributors in each aspect, looking for a way to improve the general performance of the plant. (authors)