Possibilities of material replacement in containments using the ice condenser for LOCA accidents

conference paper

English

Generally containments of pressurized water reactors (PWR) secure the function for hermetic protection from leakage of hazardous / radioactive substances into the environment in case of accident and also ensure mechanical protection against external hazards. An internal or external cooling system for enormous heat release must be used in the event of emergency situations associated with loss of coolant outside the primary cooling circuit (the loss-of-coolant accident – LOCA). Steam produced from the cooling water on the basis of pressure changes between the primary circuit and open space close to the pipeline defect (or another part of the primary circuit) fills up empty surroundings. The raising volume of produced steam may cause the pressure increase in the containment which means the risk of its failure. One of the used passive cooling systems applied directly in the containment is an ice condenser. The ice condenser is designed for melting of contained ice when produced steam flows through it and condenses. The ice phase change from solid to liquid state provides a storage capacity for the released heat and also decrease of the pressure from produced steam. Worldwide, 13 such ice condensers within nuclear power plants operate (two in Japan, two in Finland and nine in the U.S.). Application of ice as the condensing material allows reducing the overall size of the containment, which means smaller built-up area and lower investment costs for construction. However, keeping water in the solid state is associated with demands for higher operating costs and overall complexity of the cooling system. The possible ice replacement, as a heat storage material, would clearly reduce operating costs and simplify the reactor system required maintenance. Materials capable accumulating heat from the steam must be selected according to strict requirements for absolute stability and nuclear safety (i.e. without any risk of corrosion of structural materials, explosive reaction, toxicity, flammability or degradation). A simple model of the material replacement based on computational simulation was carried out. The model evaluates the ice replacement by two types of paraffin with the melting temperature markedly above the water freezing point. The model compares the rate of melting for water and paraffin on the time scale and analyzes the increase of the temperature during and after the melting within these phase changing materials.

nuclear safety, containment, phase change, energy storage, ice condenser

MARTINEC, J.; ŠKODA, R.; KATOVSKÝ, K.

2012

23. 5. 2012

978-80-214-4514-7

Proccedings of the 13th International Scientific Conference Electric Power Engineering 2012

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1250

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