Methodology of reliability calculation of international thermonuclear experimental reactor and optimization of risk mitigation actions

The article is devoted to one of the most important issues of creation of International Thermonuclear Experimental Reactor (ITER), namely, reliability. The principles of ITER reliability analysis approach which are applicable to the ITER and its subsystems are described. The basis of the reliability increasing is so-called RAMI-analysis (RAMI stands for Reliability, Availability, Maintainability, Inspectability). This analysis covers main aspects of the issue: increasing of availability and reliability, the ability to control, to maintain, to renovate, and so on. The main steps of the RAMI-analysis (functional analysis, calculation of availability and reliability, failure mode effects and criticality analysis, and determination of a list of mitigation actions) are shown on the base of real ITER subsystems. The determination of a list of mitigation actions is closely linked with optimization of possible actions which are focused on decreasing of failure possibility and decreasing of mean time to repair the failed component. A mathematical model allowing automating the selection of the most effective and the least expensive mitigation action process which is coupled with processing of large amounts of information is proposed.