Analysis for iodine release from unit 3 of Fukushima Dai-ichi nuclear power plant with consideration of water phase iodine chemistry

The accident at unit 3 of the Fukushima Dai-ichi nuclear power plant was analyzed with THALES2 for the progression of severe accident coupled with Kiche for the iodine chemistry in aqueous phase. The analysis indicated that, compared with the analysis without the aqueous phase iodine chemistry, a significantly larger amount of iodine was released from the water pool of the suppression chamber (S/C) with forms of molecular iodine and organic iodine due to the repeated operation of the containment venting system. It was also implied in the sensitivity analysis that the late phase release of the volatile iodine species was largely influenced by the pH of the S/C water and gas–liquid mass transfer coefficient under a gas–liquid two-phase flow condition.