Processing of raw data-for reliability parameter estimation

The objective of Nuclear Power Plant Safety is to ensure and demonstrate that the risk from plant to public and plant personnel is acceptably low. Probabilistic Safety Assessment (PSA) is a standard tool in safety evaluation of nuclear power plants, which provides a useful, consistent and structured framework for evaluation of safety. PSA provides an integrated model of the overall safety of the plant, which puts the safety issues in perspective, and helps in safety decisions related to both design and operations. Reliability of a system is the best representation of operating and maintenance practices if performed with plant specific reliability parameters. In order to establish this, it is necessary to collect the plant specific failure data by utilization of the data recording sources maintained at plant. Failure data can be collected from various sources such as Computerized Maintenance Management System (CMMS), Surveillance check lists, O&M logbooks, Internal Plant Failure Reports (like significant event reports) and Outage Reports. The reliability parameters like U = Unavailability, Q_d = Failure on demand, λ_r = Failure rate during running, T_r = Time to repair, λ_g, = Failure rate during standby, T_ra = Time to repair of standby component, t_m = Unavailable period during maintenance, T_m = Maintenance frequency Time between two maintenance can be calculated from the failure data. This paper deals with collection of plant specific data from various sources and the efforts put in for processing of the same to generate plant specific reliability parameters for PSA study and to find out reliability of plant equipment, calculating unavailable hours from the collected and processed data, best utilization of Computerized Maintenance Management System to get the raw data which consists of Deficiency report no. (DR no.), component tag no., Description of Failure, defect rectif- cation details, Failure Detection date and time etc.