First wall risk analysis for a loss of coolant accident in an experimental fusion reactor

One of the most vulnerable components in a fusion reactor may be the first wall, which is facing the plasma and which must be water cooled. Using statistically failure rate values coming from French fission facilities the probability of accident induced by pipe break inside the first wall has been calculated. The results show an occurrence probability of about 4 E-4 per year to contaminate the reactor hall, taking into account each prospective existing barrier. Occupational and environmental impacts are evaluated, considering all radioactive products which may be released. First results indicate that if the consequences to the reactor itself may be serious, induced doses to the public remain low enough to be achievable. An analysis of protection options which may decrease the risk is performed. (author)