Effect of water injection on hydrogen generation during severe accident in PWR.pdf

Nuclear Science and Techniques 20(2oo9)312-316 Effect of water injection on hydrogen generation during severe accident in PW R TAO Jun CAO Xuewu SchDDlofMechanicalandPowerEngineering，ShanghaiJiao Tong University,Shanghai200240,China Abstran Efectofwaterinjection onhydrogen generation during severe accidentin a1000NIW pressurizedwater react0r was studied．The analyses were carried out with diferent water injection rates at diferent core damage stages· he core can be auenched and accident progression can be terminated by water injection at the time before cohesive core debris is formed at lower core region．Hydrogen generation rate decreases with water injection into the core at the Deak coretemperatureof1700 K’becausethe coreis quenched and refloodedquickly．Thewaterinjection atthepeak core temperature of 1900 K，the hydrogen generation rate increases at low injection rates ofthe wate~as the core 1s auenched slowly an d the core remains in uncovered condition at high temperatures for a longer time than the situation 0f high injection rate．At peak core temperature of 2100-2300 K the Hydrogen generation rate increases by water injection because of the steam serving to the high temperature steam-starved core．Hydrogen generation rate increases significantly after water injection into the core at peak core temperature of 2500 K because of the steam serving to the r曲0ca血坦 Zr．U．O mixture．Almost no hydrogen generation can be seen in base case after formation of the molten pool at the lower core region．However,hydrogen is generated if water is injected into the molten pool，because steam serves to the crust supporting the molten poo1．Reactor coolant system (RCS)depressurization by opemng power ODerated relief vaires has importan t efect on hydrogen generation．Special attention should be paid to hydrogen generation enhancement caused by RCS depressurization． Key words Pressurized water reactor(PWR)，Severe accident，Core damage state，Depressurization，Water itection， Hydroge