On the risk based limits for the International Thermonuclear Experimental Reactor

ITER is an experimental fusion facility, involving new technology and exploring new physics. A complete safety evaluation is best achieved by involving probabilistic methodologies in conjunction with the deterministic ones. The current design guideline for radioactivity releases as consequences of individual accident sequences with the corresponding frequencies is similar to the Farmer limit line. However, that approach does not include important considerations such as overall risk and uncertainties in both frequency and consequence of accident sequences. Previous work showed that the regulation of risk from technological systems should take into account several aspects of risk: overall risk, the rate at which accident frequency decreases with increasing consequences, the impact of high frequency-low consequence accidents. In the present paper, a rigorous derivation of a parametric complementary cumulative distribution function (CCDF) for ITER which complies with all of these requirements is performed. Moreover, CCDF allows for the treatment of uncertainties in accident frequencies and consequences unlike the Farmer limit line approach. Therefore, defining the ITER risk limit in a CCDF form is more appropriate than the current formulation of the limit line