Analysis of liquid cryogen-water experiments with the MELCOR code

Vapor explosions are processes involving significant energy exchange betwee n a hot and colder, more volatile liquid. This phenomenon can cause signifi cant pressurization and may cause damage to structures. Historically, vapor explosions have been of interest in industrial processes with molten metal s, and postulated accident scenarios involving molten fuel and water in cur rent light water reactors. With the potential use of superconducting magnet s in fusion designs, postulated accident scenarios involving water used to cool various structures and cryogenic materials (i.e., helium and nitrogen) required for magnet cooling have to be addressed. A rapid increase in pres sure may be seen if liquid nitrogen or helium comes into contact with water . Because of significant temperature differences between the water and cryo genic materials, a rapid heat transfer event similar to a vapor explosion m ay be observed with the cryogen as the 'coolant' and the water as the 'fuel '. Experiments to quantify this phenomenon were performed at the University of Wisconsin-Madison. This paper reviews these experiments and presents co mparison analyses using the systems code, MELCOR. Experimental results show ed that no large 'shock' pressures were observed. Thus, one can consider th e 'fuel-coolant' interaction to be a boiling event controlled by 'bulk ther modynamics'. We hope to benchmark the code and show its usefulness in deter mining potential critical issues involving these fusion systems.