Status of the experiment NACOK for investigations on the ingress of air into the core of an HTR-module

Experimental investigations on the ingress of air into the core of an HTR can be divided into two categories: generic experiments, e.g. the measurement of material properties for the corrosion of specific graphite types with air to create data for the numerical calculation of air ingress accidents, and design related experiments, with the intention to investigate the course of an air ingress accident for a specific HTR design, under certain assumptions for the initiation of the accident. General safety discussions, but also the demand for catastrophe-free nuclear reactors require, that the computational predictions for the course of heavy accidents must be proven experimentally as realistic as possible, which leads in general to design related experiments. Therefore, the Forschungszentrum Juelich has set up an experimental facility to investigate for an HTR with the Siemens design the course and the local distribution of corrosion damages associated with an air ingress accident. The facility has been termed NACOK, which stands for NAtural COnvection in the core with Korrosion (i.e. the German word for corrosion). 4 refs