IMPACT OF RADIOLYSIS ON HYDROGEN PRODUCTION IN A BWR SEVERE ACCIDENT

摘要

Conservative hypotheses were often made in the past about the importance of radiolytic process during severe accidents, so that new estimates have been made in the framework of the analyses of the recent meltdown accidents occurred at Fukushima. To limit the overestimation of radiolytic hydrogen, the present work considers the absorption of decay gamma rays in a sample region of fuel and water of Fukushima-Daiichi Unit 1 with a simulation based on the code MCNP (Monte Carlo N-Particle Transport Code). The calculated power absorption of gamma photons in the water is then used to have a reasonable estimate of the maximum hydrogen generation rate. The obtained value is compared with the actual performances of the hydrogen recombiner system operating in a large BWR plant and confirms the very limited contribution of the radiolytic effect in a meltdown accident.