Host: The Japan Society of Mechanical Engineers
Name : Proceedings of FDR2022 International Topical Workshop on Fukushima Decommissioning Research
Date : October 14, 2022 - October 17, 2022
In the framework of the OECD/NEA ARC-F project, predictions of long-term MCCI progression by eight different computer codes have been compared for the configuration of the FUKUSHIMA DAIICHI UNIT 1 sump. Indeed, the severe accident at Fukushima Daiichi Nuclear Power Station occurred on March 11th 2011. Nevertheless, the effective cooling of the fuel debris was not restored before March 23rd. Therefore, Molten Core Concrete Interaction (MCCI) most likely occurred for more than 10 days without the presence of water (i.e., under dry conditions). Such a long period of MCCI is rarely studied.
This paper focuses on the detailed analyses of the results obtained with the TOLBIAC-ICB tool during the two steps of this benchmark. The first step consisted in a preliminary rough comparison of results allowing then to draw new converged axes of research. Results of TOLBIAC-ICB V3.4 mod2 is described and explained in relations with implemented physical models and results obtained from others codes. The second step presented simulations with more agreed initial data and boundary conditions. The detailed MCCI phenomenology is depicted and physically discussed based on the long-term evolutions of temperatures, detailed pool and crust compositions in term of chemical components, 2D ablation front, gas releases… All this advanced analysis raises the question of the validity of some models of current, intensively used, MCCI tool for very long term transients.
