High temperature reaction between sea salt deposit and (U,Zr)O simulated corium debris

Takano, Masahide ; Nishi, Tsuyoshi

In order to clarify the possible impacts of sea salt deposit on the chemical and physical state of the fuel debris formed in the severe accident at Fukushima Daiichi Nuclear Power Plant, the high temperature reaction between sea salt deposit and (U,Zr)O simulated fuel debris (sim-debris) was examined in the temperature range from 1088 to 1668 K. The dense layer of calcium and/or sodium uranate formed on the surface of sim-debris pellet at 1275 K under airflow, with the thickness of over 50 m. When the oxygen partial pressure is low, calcium likely dissolve into the sim-debris to form solid solution. The diffusion depth was 5-6 m from the surface at 1275 K for 12 h. The crystalline MgO remains as the main residue stuck on the surface. A part of it can dissolve into the sim-debris depending on the temperature.