Concrete Pixels

In the concrete world, we have a very special type of concrete called the “the redeemer or sacrificial concrete”. This concrete is indeed special as it has an exceptional purpose in the new designs of nuclear power plants. It is very useful in case of core melting, one of the possible failure of a nuclear reactor. Although the possiblity is very remote for such thing to happen under the new generation reactors, provisions are still made just in case it happens. This type of concrete I believed is not yet in textbooks and there are still very few if none available literatures that deals with it. Designing such concrete involves not only concrete engineers but also chemists. This concrete under extremely high temperature during core melt will oxidize the aggressive substances of the materials coming from the molten metal of the reactor and at the same time enhancing the spreading of the melt in a specially designed compartment inorder to avoid the escape of radioactive materials and a basemat failure. An in-depth understanding of what we call MCCI or molten core and concrete interaction is essential inorder to develop this concrete. The company I worked for, Areva NP, the designer and builder of the world’s first generation III+ EPR nuclear reactor project in Finland has made extensive research of such type of concrete. Although this concrete should melt along with the reactor vessel, the strength has to be maintained like the ordinary concrete. Meticulous choice of materials is indespensable. Mix designs, trial mixes and pumping tests were successfully done by our team here at the project site in Finland with the able leadership of our two “concrete gurus”. Sometimes I call these guys the “walking concrete” encyclopedias.