抄録
Behavior of water injected into cold-leg piping by accumulator system and low pressure coolant injection system and the effect of the coolant injection on core cooling are discussed for the case of large double-ended cold-leg break. Major results are as follows:
(1) Steam-water counter-current two-phase flow in downcomer limits downcomer penetration rate of the injected water and results in longer duration of refill phase. Enlarging downcomer gap is effective for increasing the penetration rate.
(2) Steam binding due to high core temperature interferes with coolant entering into the core and the resultant core cooling. Chugging oscillation occurs while mixture level rises in the active core region.
(3) It is of considerable importance to note that in order to achieve effective core cooling during the long reflooding process, mixture level must be raised to the active core region before the core temperature becomes very high.
