Phased Mission Analysis of Maintained Systems. A Study in Reliability and Risk Analysis

摘要

The present study is devoted to system reliability and is mainly directed to the quantitative evaluation of accident sequences. Event tree methodology and fault tree analysis are applied as basic techniques. It introduces a new methodology for the calculation of the probability of occurrence of an accident sequence. This new methodology takes correctly into account shared equipment dependencies between the different systems present in an accident sequence. Since large and/or complex systems may contain a large number of minimal cut sets (sometimes millions of it), it is not possible as a rule to obtain the exact analytical solution. Therefore, upper and lower bounds for the probability of occurrence of an accident sequence are presented. Calculation results show that this probability is under-estimated if system dependencies are not fully taken into account. The new methodology also offers the possibility to get insight into the degree of dependency between systems based on quantitative calculations. To make the methodology manageable for complex systems, it is implemented in the reliability computer program PHAMISS. This program is written in FORTRAN-IV for the CDC-Cyber 175. PHAMISS is users friendly and has proven to be a fast and efficient program. (Atomindex citation 16:042283)