A First Approach to the Safety Analysis of a Tokamak Test Reactor by a System Study Methodology

The safety analysis and risk assessment of a Tokamak Test Reactor is approached by an iterative, probabilistic, system study methodology, jointly devoloped by ENEA^a and CEA^b. The first part of this methodology consists of a safety related functional analysis of the plant. That is developed in a quite systematic and exhaustive way, aiming at the identification of all the process functions and their modes of loss, so as to forecast all the possible initiating events of safety relevant accident sequences, and their subsequent evolution. This aim is achieved making use of functional interaction and interface matrices, functional fault trees and event trees. The second part concerns the overall plant risk assessment. This is performed using PRA (Probabilistic Risk Assessment) concepts and methods to work out the probabilistic quantification of the system event trees (and linked fault trees), and the evaluation of the related consequences. The methodology is applied by iterations, following the different stages of the plant design development. The first iteration has been applied to the safety analysis of the “Vacuum”, “Tritium and Fuel Handling”, “Blanket” and “First Wall and Divertor” systems of a Tokamak Test Reactor, with a particular reference to NET^c. ^aThe Italian National Committee for the Nuclear Energy and Alternative Energies. ^bCommissariat à l'Energie Atmoque, the French Natinal Commissariat for the Atomic Energy. ^cNext European Torus, IPP Garching, Germany F.R.