Analysis of material effect in molten fuel–coolant interaction, comparison of thermodynamic calculations and experimental observations

Molten Fuel–Coolant Interaction (FCI) is considered an important phenomenon in the frame of nuclear reactor severe accident research and development. Recently, the so-called “material effect” in FCI was observed in several experimental research programs. It was found that chemically different melts yield to different explosion energetics or trigger-ability during FCI tests. The presented work is focused on the thermodynamic modeling of high temperature chemical reactions during the melt–coolant interaction and consequent comparison with results obtained by material analyses of debris coming from KROTOS (CEA, France), MISTEE (KTH, Sweden) and PREMIX (FZK, Germany) experimental research programs. Calculations at thermodynamic equilibrium were obtained using the Gemini 2 (Thermodata) Gibbs energy minimizer. Information about debris composition, morphology and structure were collected using solid-state characterization techniques such as scanning electron microscopy, X-ray powder diffraction and thermogravimetry. Chemical reactions of melt and water vapor were theoretically predicted and experimentally confirmed, and therefore, features like melt solidification path, hydrogen production and melt oxidation are discussed.

► Our work id focused on the description of the material effect in FCI.
► We performed thermodynamic modeling describing chemical reactions of melt and water.
► Calculated results are compared with recent solid-state analyses of FCI debris.
► Various FCI debris were characterized by solid-state analytical techniques.