Experimental Design and Result of Water Injection on Molten Zirconium-stainless Steel Metallic Pool

Water injection on molten zirconium-stainless steel metallic pool to partly remove decay heat is regarded as one of potential strategies to mitigate the “heat focus” effect of metal layer for larger power reactors. But complicated phenomena may appear when water injection on the molten metallic pool, it’s necessary to perform experiments to investigate this strategies to verify its feasibility and effectiveness. The innovative design of the experimental system named ATOM (wATer injectiOn on molten zirconium-stainless steel Metallic pool experiment) was introduced in this paper. The prototype metallic material of zirconium and stainless steel were used for the working medium in this experimental facility. Based on the built experimental facility, experimental researches were conducted. The effects of different mass fractions of zirconium, water injection flow rates, and water subcooling (or water temperature) were considered in the setting of experimental conditions. The typical mass fractions of zirconium were 13% and 60%, the typical water injection flow rates were 0.05 kg/s and 0.10 kg/s, and the typical water subcooling were 15 ℃ and 50 ℃. Nine experiments were conducted, and the results indicate that: 1) This experimental facility design can successfully achieve the bottom heating and melting of the zirconium iron metal that is close to the prototype, and maintain the bottom heating state during water injection; 2) The heat flux range of the molten metal layer surface with water injection is about 0.8-1.4 MW/m² under the setting conditions of this experiment; 3) The higher of the heat flux will achieve on the molten metal layer surface during water injection, with the larger of the water injection flow rate and the lower of the mass fraction of zirconium; 4) Water injection on molten zirconium-stainless steel metallic pool does not cause phenomena such as steam explosion, splashing of a large amount of molten material, or hydrogen explosion under the conditions of this experiment. It can be concluded that the heat flux removed from the surface of metal layer after water injection is higher than the upward radiation heat flux density when the stable molten pool is formed in the actual lower head of the power plant. Water injection on molten zirconium-stainless steel metallic pool can help alleviate the heat focusing effect of the metal layer. The results of this research can provide valuable reference for severe accident mitigation strategy.