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 cavity, is a very complex process to simulate and predict, but the knowledge of this process is of major importance for planning the emergency counteractions for severe accidents with respect to the Stress Tests requirements after the Fukushima-Daiichi accident. The key issue is to predict the rate and most probable focusation 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 fuzzylogic interpretation of the thermodynamic trends which reflect the aggregate type. This approach allows estimating 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.

Fuzzy Logic Model of Irradiated Aggregates

“…Since the data used for the development of the model are limited, the fuzzy logic approach is utilized for the same reasons as in the previous work [15,10].…”