High-head safety injection pumps

High-pressure safety injection water is provided by separate high-head pumps while lower pressure injection water is supplied by the RHRS pirnips. Passive accumulator tanks are inside the containment to provide for fast injection of water after a LCXZA. Figure 2.19 shows the injection phase of the SIS and is the configuration for a four-loop plant. The configurations for two- and three-loop plants differ only in the size of the components and the number of branch injection lines to the RCS. 

HPSI system pressure - means the water pressure delivered by the HPSI system to the reactor. Normally, HPSI pump head pressure at the rated HPSI pump flowrate will be entered. Units using other systems of high pressure safety injection (e g. a gas-driven water injection used at CANDU reactors) should enter the maximum attainable pressure of water being injected by HPSI to the core. The appropriate value should be expressed in MPa. 

The safety injection system, which has a large capacity, consists of 2 charging pumps, 4 high head injection pumps, 2 low head injection pumps and 2 accumulators (passive action). If a LOCA occurs, the boronated water will be made to pass into RCS by the safety injection system. 

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