Refractory Geopolymers: Thermal Shock Resistant Material for Nuclear Safety

There has been an increased interest in geopolymer materials thanks to their properties often superior to commonly used concrete. In nuclear technology, geopolymers are mostly studied for the immobilization of radioactive waste. These materials exhibit increased radiation stability, low water content and the ability to embed various filling materials to enhance or modify their physicochemical properties. Therefore, straightforward, but often omitted, applications are as sacrificial, construction or refractory materials in passive or active safety systems of NPPs. These can be helpful in increasing the nuclear power plant safety or the mitigation of severe accident consequences. Herein, we present a scoping interaction test of geopolymer material with simulated molten corium. It covers the melting of prototypic corium (diluted with sacrificial material) and its impact on the refractory geopolymer plate. The results of macro and microanalysis showed a good impaction resistance of the geopolymer, no cracking, and minimal interaction zone. Chemical interactions between the corium melt and refractory geopolymer plate were studied by scanning electron microscopy. It was found that the silicate mixture melt is enriched in magnesium content and, therefore, probably responsible for the MgO filler dissolution. The distributions of uranium and gadolinium showed limited solubility the silicate matrix and existence of their solid solution after solidification.