On the reliability of fire detection and alarm systems. Exploration and analysis of data from nuclear and non-nuclear installations

A literature review of reliability data of fire detection and alarm systems was made resulting to rough estimates of some failure frequencies. No theoretical or technical articles on the structure of reliability models of these installations were found. Inspection records of fire detection and alarm system installations by SPEK were studied, and transferred in electronic data base classifying observed failures in failure modes (59) and severity categories (3) guided by freely written records in the original data. The results of that work are presented without many comments in tabular form in this paper. A small sample of installations was collected, and number of components in them was counted to derive some distributions for determination of national populations of various components based on know total amount of installations. From NPPs (Loviisa, Olkiluoto and Barsebaeck) failure reports were analysed, and observed failures of fire detection and alarm systems were classified by severity and detection mode. They are presented here in tabular form for the original and new addressable systems. Populations were counted individually, but for all installations needed documents were not available. Therefore, presented failure frequencies are just first estimates, which will be refined later. (orig.)