ESTIMATION OF ABLATION DEPTH IN CONCRETE SLAB UNDER REACTOR DURING NUCLEAR ACCIDENT

Abstract

The molten reactor core-concrete interaction, which describes the effect of molten reactor spread on the concrete floor of the reactor pit, is a very complex process to simulate and predict, but the knowledge of this process is of major importance for planning the emergency counteractions in this Fukushima-style accident. The key issue is to predict the rate of the melt-through process which is affected by the concrete composition, especially by the aggregate type. A limited number of small-scale experiments have been conducted over the past years along with accompanying numerical models which focused mainly on the siliceous type of aggregate. It is common for the concrete structures that the limestone type or the mixture of these two types of aggregate are used as well. Then, the objective of this paper is to extend the knowledge gained from the experiments with the siliceous aggregate to the concrete structures which are made of limestone aggregate or their combination, such as limestone sand and siliceous gravel. The proposed one-dimensional model of the melt-through process is based on the fuzzy-logic interpretation of the thermodynamic trends which reflect the aggregate type. This approach allows to estimate the asymptotic cases in terms of the melt-through depth in the concrete floor over time with respect to the aggregate type, which may help to decide the rather expensive further experimental efforts.