LARGE SCALE VULCANO MOLTEN CORE CONCRETE INTERACTION TEST CONSIDERING FUKUSHIMA DAIICHI CONDITION

Fuel debris removal is one of the most important processes for decommissioning a severely damaged nuclear power plant (NPP) such as Fukushima Daiichi NPP (1F). In order to develop relevant removal tools, characteristics of fuel debris are required. Assuming that the test products generated in a MCCI experiment under similar conditions to 1F have similar characteristics to that encountered in actual 1F MCCI products, a VULCANO MCCI test was performed in order to obtain prototypical corium samples and analyze them. The objective of the test was to reach a concrete ablation ratio ΔV/V (where ΔV is the concrete ablation volume, and V is the initial corium volume) close to the concrete ablation ratio of 1F unit 1 (1F1) estimated with the MCCI simulation code TOLBIAC-ICB (~1.6 for 3 days of MCCI). The test named VF-U1 was carried out on January 19, 2017. About 40 kg of a metal and oxide corium pool has been obtained thanks to inductive heating. Corium was directly melt into the test section made of a representative Fukushima 1F unit 1 concrete with Japanese basaltic aggregates. The test section was 2D cylindrical with an inner diameter of 250 mm, an outer diameter of 500 mm surrounded by the induction coils. The maximum concrete thickness that could be ablated radially and axially was about 100 mm. During 12 minutes, a representative MCCI in terms of heat fluxes and ablation velocities occurred. On the whole experiment that lasted 18 minutes, the bestestimate relative ablation volume ratio was 1.68 which was consistent this the target value. Dismantling of corium has been performed and shows a separation of oxide and metal phases. From practical point of view, technical issues were pointed out which are based on the insights from the dismantling of the test section.