Safety Injection Flashcards
What are the 3 functional areas of the SI system?
emergency core cooling (safety injection), residual heat removal (shutdown cooling), and containment heat removal (containment spray)
How does the safety injection system accomplish emergency core cooling?
by injecting borated water into the RCS to cool the core in the event of a LOCA and maintain flow through the core for extended periods.
Why is borated water injected into the core following a secondary steam line rupture?
to increase shutdown margin. The plant will rapidly cool due to the large amount of steam being drawn off the steam generator. Cold water = reactivity addition, so borated water is added to counter the cold water.
What is the maximum temperature and pressure that shutdown cooling can be installed?
350F and 395 psia
How is the shutdown cooling system used to remove heat from containment following a LOCA?
by shifting the heat exchangers to the recirculation mode
What is the shutdown cooling system also used for during re-fueling?
supplement cooling capacity of the fuel pool cooling system and transfer water between the refueling water tank and the refueling pool.
Is the SI system class or non-class?
CLASS
What does the containment spray system do for us?
a) spray borated water into containment atmosphere during a LOCA or steam line rupture to reduce temp and pressure and limit airborne activity release from containment.
b) remove iodine from containment atmosphere
c) remove heat from containment following a LOCA by shifting HX to the recirc mode
d) provide additional flow during shutdown cooling to maintain cooldown rate at lower temps.
What is meant by a passive component of the SI system?
Refers to the SITs. 4 of them connected to the RCS cold legs lined up ready to inject through check valve if rx pressure < 600psig
Where to HPSI and LPSI initially take a suction from and discharge to?
suction from RWT and discharge to all 4 cold legs. Can be lined up to hot legs.
Draw SI system
include:
RWT, suction lines and valves, containment sumps lines and valves, HPSI pumps with lines and valves, LPSI pumps with lines and valves, Recirc lines and valves for HPSI & LPSI pumps, CS pump, Hot leg injection lines and valves, Cold leg injection lines and valves, and SITs and their valves/lines
What does EW supply in the SI system?
cooling to shutdown cooling heat exchanger
What is the “rumble region” and what pump is affected by it?
The LPSI pump has a rumble region of 2500-3500 GPM and should not be operated in this region. It’s caused by the swirling of water past the pump suction elbow and the swirl of water induced by the pump impeller interacting.
Where does each HPSI pump inject?
to all four cold legs and can be lined up to inject to the hot legs.
How does the HPSI pump increase pressure high enough to inject water into the RCS?
through 8 stages that compound the pressure.
When and how are the SIT isolation valves closed?
during shutdown BEFORE RCS pressure drops below SIT pressure the isolation valves are energized and shut.
What keeps pressure on the SITs?
Nitrogen supplied by the GA system (service gases)
Where are the RAS (recirculation) sumps?
basement of the containment building
Why do the LPSI pumps trip on a RAS signal?
to ensure adequate NPSH is available for the CS pumps and HPSI pumps.
When can the shutdown cooling subsystem be used?
Post shutdown to get the RCS down to refueling temperature and during normal operations it can be used to remove decay heat when the RX is shutdown and steam generators are not available
What components make up the shutdown cooling subsystem?
LPSI pumps, CS pumps, SD cooling HX, LTOPS (low temp over pressure protection relief valves), and vlvs and piping
Describe the basic flow path of the shutdown cooling system.
suction from the hot leg, into LPSI pump, through the SDCHX, and back in through the LPSI loop injection valves
What other pump can supply shutdown cooling (with limitations)?
CS pump
What system supplies cooling water to the SDHX?
Essential cooling water
Where are the SDHXs?
70’ of the Aux building in their own rooms
When do the LTOP valves provide over pressure protection?
If an RCP is started w/ S/G secondary water temp <= 100F above RCS cold leg temps
OR
inadvertent SIAS with 2 HPSI pumps injecting into a water solid RCS, 3 charging pumps injecting, and let down isolated
What is the set point of the LTOP valves?
467 psig
What is the main function of the CS subsystem?
a) prevent containment building failure by reducing pressure and temperature during a LOCA
b) remove iodine from the containment atmosphere
What is the flow path for CS?
from RWT, through CS pump, through SDHX and out into containment through valves
What is the rumble region for the CS pumps?
1800-2800 gpm
What signals will start a CS pump?
SIAS or CSAS will start the CS pump after 15 seconds.
What signals will start a HPSI pump?
SIAS/CSAS
What signal will stop a LPSI pump?
RAS.
What is the LPSI pump used for during normal operations?
mixing the RWT via recirc
What pressures actuate a SIAS alarm?
1837 psia pressurizer pressure during plant operation or containment pressure of 3 psig
At what pressure will a CSAS signal be sent to the CS pumps?
8.5 psig
