SI- Safety Injection Flashcards
What are the main purposes of the SI systems?
1) emergency core cooling
(safety injection)
2) residual heat removal
(shutdown cooling)
3) containment heat removal
(containment spray)
4) containment iodine removal
5) rcs inventory during SBO using HPSI
What are the main functions of the safety injection subsystem?
flood and cool the core with borated water after a LOCA
short and long term cooling after a LOCA
increase shutdown margin with borated water
Why does the RCS need to be flooded and cooled by the SI system after a LOCA?
to prevent cladding failure
What are the main functions of the shutdown cooling system?
keep RCS cool post shutdown
brings plant to cold shutdown
remove heat from containment
supplement cooling capacity of fuel pool cooling
transfer water from RWT to the refueling pool
What temp. and pressure does shutdown cooling keep the RCS after shutdown?
under 350*F and 395 psia
What are the main functions of the containment spray system?
cools containment atmosphere with borated water spray
rapidly reduce fission product iodine from containment atmosphere
additional flow to shutdown cooling
remove heat from containment by shifting heat exchangers to recirc mode
Mixing TSP into water in recirc sump to achieve desired >7 pH
Prevent localized accumulation of hydrogen by mixing hydrogen in containment
Per design basis, what is the peak cladding temp. limit?
2200*F
Per design basis, maximum cladding oxidation shall not exceed what?
17% times total cladding thickness
Per design basis, What is the maximum hydrogen generation?
1%
Per design basis, calculated changes in core geometry shall be what?
amenable to cooling
What are the design requirements of the RWT?
20 minutes full flow for both SI trains and all pumps plus 10%
fill refueling pool
equal flows to all RCS injection points
Where do the SITs inject borated water?
all four RCS cold legs
How many SITs are there? What holds the discharge check valve shut?
4
RCS pressure
Where do the HPSI, LPSI and CS pumps take suction from?
RWT initially
RAS sump
Where do the HPSI and LPSI pumps inject borated water?
HPSI
respective hot leg and all four cold legs
LPSI
two cold legs
How does the SI system interface with PB?
PB provides power to the HPSI, LPSI and CS pumps
How does the SI system interface with PH?
PH provides power to SI valves
How does the SI system interface with PK?
PK powers SI valves and breaker control
How does the SI system interface with PN?
PN powers SI valve position indicators and instrumentation
How does the SI system interface with PE/DG?
PE/DG provides emergency standby power for SI
How does the SI system interface with NE/GT?
NE/GT provides emergency standby power to SI during station blackout
How does the SI system interface with CH?
CH supplies borated water (RWT)
purification for SDC
relief valve discharges
SITs drainage
Where do the SI relief valves relieve to in containment? Outside containment?
RDT
Equipment Drain Tank (EDT)
Where can the SITs be drained to?
RDT or RWT
How does the SI system interface with EW?
EW is cooling water to SDCHX
How does the SI system interface with GA (service gases)?
supplies HP nitrogen to SITs
How does the SI system interface with IA?
air supply to pneumatic operators, instruments and controls
How does the SI system interface with HA (Aux. building HVAC)?
cools SI pump rooms
How does the SI system interface with ESFAS/SA?
ESFAS/SA sends signals to SI to operate pumps and valves
sends signal to BOP
Sends signals to Aux. relay cabinets which send signal to SI valves
How does the SI system interface with BOP ESFAS?
BOP sends LOP/LS and load sequencer signals to SI
What is the rumble region of the LPSI pumps?
2500-3500 GPM
What kind of pump is the LPSI pump? Where are they located?
vertical, single stage centrifugal
40 ft Aux building w/ 50 ft access
What kind of pump are the HPSI pumps? Where are they located?
horizontal, eight stage, centrifugal pumps
aux building 40ft w/ 50 ft access
How does the HPSI pump increase the pressure of the water high enough to inject into the RCS
The HPSI pump groups several stages together in series to obtain a higher discharge pressure.
Where are the SITs located?
in containment on each respective cold leg
What pressure are the SITs held at?
600 psig
If the SITs are held at 600 psig, at what pressure will they inject borated water into the RCS?
below 600 psig
What are the valves between the SITs and the RCS cold legs?
two check valves and one motor operated valve
What is the status of the SIT motor operated valve during normal operation?
open with power removed
What is done with the SITs before RCS drops below 600 psig?
MOV is repowered and closed
How many SITs are needed to safely recover to core during a LOCA?
3 out of 4
How is the water injected into the core from the SITs?
The water is injected by means of the Nitrogen over pressure passively flow water into the core when the RCS pressure drops below the SIT pressure.
Where are the recirculation sumps located? How many are there?
containment basement
2
What is the purpose of the recirculated sumps?
collect the water released from SI, a break in the RCS or from CS
When the RWT is depleted, SI pumps take suction from the sumps
What is the low level in the RWT that causes a RAS?
9.4%
What does a RAS do?
places the recirculation sumps in service
trips LPSI pumps
Why does a RAS trip the LPSI pumps?
ensure NPSH for CS and HPSI
What is the purpose of the Trisodium Phosphate (TSP) baskets in the containment?
raises the pH of the recirculation water to ensure that iodine stays in solution
inhibit Stress Corrosion Cracking (SCC) of austenitic stainless steel components in containment during the recirculation phase following an accident
Is the RAS suction piping self-venting? Must it be kept full?
it is not self-venting and must be kept full
What main components are used for SDC?
LPSI/CS pumps
SDCHX
LTOPs
valves and piping
What are LTOPs?
Low temperature over-pressure protection valves
What cools the SDCHX?
essential cooling water
For SDC, which pump is preferred?
LPSI preferred, so the CS pump is available for emergency spray
For SDC, can the LPSI and CS pump be used in parallel?
yes
Where do LTOPs relieve to?
recirculation sump
Where are the SDCHXs located?
aux building 70’
What type of HX are the SDCHX?
shell and U-tube
What removes RCS sensible heat and core decay heat and transfers that heat to the EW system?
SDCHX
What is the set point on the LTOPs?
467 psig
What is the purpose of the LTOPs?
to prevent RCS over pressure during:
start of idle RCP and secondary water temp of S/G is < 100*F above RCS cold leg temp
inadvertent SIAS with two HPSI pumps injecting into a water solid RCS, three charging pumps injecting and letdown isolated
What is the purpose of containment?
third barrier to releasing fission products
How does CS reduce containment temp. and pressure?
spraying subcooled borated water into the atmosphere
Besides lowering containment temp. and pressure, what else does CS do?
reduces iodine in the containment atmosphere
What are the major components of the containment spray sub system?
Containment spray pumps
Containment spray headers
Shutdown cooling heat exchangers (SDCHXs)
Spray isolation valve
What type of pump are the CS pumps? What is the rumble region?
vertical, single stage, centrifugal pumps
1800-2800 GPM
How long does it take for the CS pump to start after a SIAS or CSAS occurs?
15 seconds
What is the purpose of the containment spray pumps?
They provide the motive force to push the water into the spray header to cool down and depressurize containment.
What is the auto feature of the HPSI pumps?
auto start on receipt of a SIAS and CSAS
What are the auto features of the LPSI pumps?
auto start on SIAS and CSAS
auto trip on RAS
What is the auto feature of the CS pump?
auto start on SIAS and CSAS
What are the power supplies for the HPSI, LPSI and CS pumps?
PBA-S03 and PBB-S04
Which pump is used to recirculate the RWT?
LPSI
What pressure will the pressurizer drop to before generating a SIAS?
1837 psia
A LOCA or a steam line break inside the containment will cause a rise in containment pressure. The containment pressure set-point value that produces a SIAS is what?
3 pisg
Which pump is used to fill the SITs?
the B HPSI
What is the normal LPSI line up, through or bypassing the SDCHX?
bypassed
What is the pressure that containment reaches before initiating a CSAS? How many pumps start?
8.5 psig
two
Prior to heating up the primary plant above cold shutdown conditions, all components of the shutdown cooling system that are required for safety injection or containment spray are what?
realigned for possible emergency operation.
Will a loss of power to the (A) LPSI pump prevent the shut down cooling system from performing its job and why?
No, the shut down cooling system has redundant components that allows it to still perform its’ job.
RWT being inoperable would mean what for the plant?
SI would not meet its safety function and core degradation may occur
Without the CH system, What would happen to the chemistry of the RCS?
it would not get purified and no chemicals would be able to be added
What would happen to the RCS if the SDCHX lost EW cooling?
RCS would heat up, undesirably.
What is required for a SIT to OPERABLE?
MOV full open, power removed
limits in Surveillance Requirements (SR) for contained volume, boron concentration, and nitrogen cover pressure
In modes 3 and 4, what must the pressurizer pressure be?
less than 1837 psia
What is the tech spec for SITs while shutdown?
Operability is MOV must be full open when pressurizer pressure 430 psia or higher
power removed from MOV when PZR pressure is 1500 psia or higher
limits established for volume, boron and nitrogen
What does ECCS stand for?
Emergency core cooling systems
What is the tech spec for ECCS while operating?
Modes 1, 2, 3, PZR pressure greater than or equal to 1837 psia or RCS Tc greater than or equal to 485*F, an ECCS train consists of both a HPSI and LPSI subsystem
How long after a LOCA is the HPSI flow path diverted to both the hot and cold legs?
2-3 hours
What is the tech spec for ECCS while shutdown?
mode 3- PZR pressure less than 1837 and RCS Tc less than 485*F
mode 4- ECCS has one HPSI subsystem
What is the tech spec for the RWT?
modes 1-4, RWT must meet the limits for water volume, boron concentration, and temperature
What is the tech spec associated with the Trisodium Phosphate (TSP)?
TSP baskets shall contain greater than or equal to 524 ft^3 of active TSP
must keep pH greater than or equal to 7
describe the engineering study for RAS piping voids
venting is intended to minimize the amount of air going into the suction of the ECCS pumps and becoming air bound.
the purpose of the study was to validate and confirm that a 5 second vent was adequate for pump starts
For the RAS piping study, what is the maximum allowable air void in the RAS piping?
5.45 cu-feet
How far open do you throttle a vent valve initially?
1/4-1/2 open
How many vent valves can be vented at one time?
1
If air is present during venting, how far open can you throttle the valve in a controlled manner?
2 turns
How long must a solid stream of water be seen prior to shutting a vent valve?
2 minutes
What information must be provided to engineering when air is present during venting?
valve position required for air free flow
time to reach air free flow
When venting SINVA27, -28, SIAVA25 and SIBVA26, you still open the vent valve 1/4 turn. What is different about these valves compared to normal guidance on venting?
you don’t increase valve turns and recorded in seconds until air free flow
Describe the SI valve pressure locking mod
some have bonnet relief check valves discharging to the upstream line
some have pressure equalization lines that discharge to the suction of the valve
Where does the “rumble” occur in the LPSI pump when operating in the Rumble Region? Why is it detrimental?
Occurs approximately one foot upstream of the pump impeller. Operation in the rumble region creates increased erosion of the piping and impeller
What services does the Chemical and Volume Control system provide for Safety Injection?
Provide path for Charging pump flow to SI for check valve testing
Provide thermal relief protection paths to the RDT
Provide thermal relief paths to the EDT, via recycle vent header
Provide shutdown purification during shutdown cooling
Provide gravity feed suction path from RWT to charging pumps for boration
Provide collection of a bleed off from leaky check valves
Provide suction from RWT to HPSI, LPSI, and CS pumps
Where are the CS pumps located?
40’ aux. building w/50’ level access
Concerning the Containment Spray pumps, what is the purpose of the minimum flow orifices?
Provide alternate flow path used during pump startup to prevent pump damage while operating against a closed system
