DECAY HEAT Flashcards
Purpose/function
Provides a means for removing residual heat and fission product decay heat when the reactor is shutdown
Decay heat
Purpose/function
Provides a means of automatically injecting a stored supply of borated water into the reactor in the event that LOCA occurs during reactor operation
In the even of a reactor coolant system rupture ECCS operation will perform the following 5 things?
Limit the peak clad temp to <2200F
Limit clad oxidation to 17% of original clad thickness
Limit the zirc water reaction to that which represents less than 1% of the clad
Maintain a coolable core geometry
Establish long-term cooling
In the event of a small reactor coolant leak, in which BWST boarted water has been exhausted, system can be placed in in recirculation mode using what system to remove spilled water from rx building and supply that water to which pumps?
What is this called?
HPI system can be placed in recirculation mode
Using the LPI system
Supply that water to the HPI pumps
It’s also known as PIGGYBACK
Components
BWST
TS minimum
350,000 gallons (56ft), 2500 ppmB, 40F
Components
BWST
Admin limits
350,000 gallons(56ft), 2552-2750 ppmB, 40-100F
Components
BWST
Volume alarms
LOW setpoint open which valve(s)
Low low setpoint, close which valve(s)
Low: 9.5 ft -> Open DH-V-6A/B
Low low: 6.3 ft -> DH-V-5A/B
BWST
Temp
Temp min and temp max
40 F min
100 F max
BWST
Temp
Electric heaters maintain temp by turning on at what temp and off at what temp?
Where is temp sensed?
Heaters trip on low BWST level of what?
Do not energize heaters < how many feet?
On at 50F, Off at 55F
Temperature sensed at 52’ elevation
Heaters trip on low BWST level 6.3’
Do not energize heaters <3’
RB ECCS Sump DH-T-7
Overflows to where and what height?
Overflows to RB floor at 86”
RB ECCS Sump DH-T-7
Normally dry, no low level alarm
setpoints
HI PPC alarm, Hi map alarm, HI HI PPC alarm, HI HI map alarm, overflow to RB floor
Hi PPC alarm 5
Hi MAP alarm 10
Hi Hi PPC alarm 80
Hi Hi MAP alarm 84
Overflow to RB floor 86
TSP (tri-sodium phosphate)
T.S require how many pounds of TSP?
18,815-28,840 pounds
DH-V-5A/B
Opens on which ES signals?
What block?
What position are these valves usually in?
Opens on ES signal (1600/500/4)
Block 1
Normally open
DH-V-5A/B
Manually close DH-V-5A/B when BWST lowers to what level
OR
RB flood level increases to what level?
BWST lowers to 9.5’
OR
RB flood level increases >56”
DH-V-1
Power supply and breaker normal position?
Powered from 1C ESV MCC
Breaker normally locked open
DH-V-1
Interlocks (4)
Rcs< 400# open permissive
RCS >400# auto close
Prevents overpressurizing DH piping
Interlock override at ESAS bistable #1 cabinet
DH-V-1
Administratively
> 370# or >300F must remain closed
Pressure locking prevention ensures valve will travel
DH-V-2
Power supply
Interlocks (4) same as DH-V-1 except it’s ESAS bistable #2 (different pressure transmitter)
RCS<400# open permissive
RCS>400# auto close
Prevents overpressurizing DH piping
Interlock override at ESAS Bistable #2 cabinet
DH-V-2
Administratively
> 370# or >300 F must remain closed
Pressure locking prevention ensures valve will travel
DH-V-3
Power supply
Are the pushbuttons JOG or not?
1C ESV MCC
OPEN pushbutton is JOG
Close is not jog
DH-V-12A/B
Normal position for each
DH-V-12A is normally locked closed
DH-V-12B is normally locked open
DH-P-1A/B
Power supplies
Auto start
Cooled by what?
Powered from 1D/E 4kv
2.)Auto start on ESAS (1600/500/4) block 1
Pump remains on recirc until RCS pressure drops below pump shutoff head (~190#)
Motor breaker remains closed on UV
3.)Cooled by DCCW
Flow path/limits for LPI
Through DH-V-56a/b
Train suction from BWST w/ dh-v-38a/b closed
Total suction from BWST w/ DH-V-38a/b open
Through DH-V-56a/b 125-150 gpm
Train suction from BWST w/ dh-v-38a/b closed 3300 gpm
Total suction from BWST w/ DH-V-38a/b open 3300 gpm
Flow path/limits for LPI
Train suction from ECCS sump w/ DH-V-38a/b closed
Total suction form ECCS sump w/ DH-V-38a/b open
Subtract 100 gpm if utilizing pzr aux spray (DH-V-64 to RC-V-4)
Train suction from ECCS sump w/ DH-V-38a/b closed 3000 gpm
Total suction form ECCS sump w/ DH-V-38a/b open 2800 gpm
Subtract 100 gpm if utilizing pzr aux spray (DH-V-64 to RC-V-4)
DH-C-1A/B
Cooled by what?
Inlet throttled rather than outlet to prevent what?
Cooled by DCCW (shell)
To prevent cavitation across valve
DH-V-7A/B
Power supply
Used for what? Allows MU pumps to do what? BWST will be depleted but RCS pressure still too high for what?
Powered from 1A/B ESV MCC
Used for small break LOCA
Allows MU pumps to use water from RB sump
BWST will be depleted but RCS pressure still too high for DH pumps
DH-V-4A/B
Power supply
Does what and on which ES signals?
Powered from 1A/B ESV MCC
OPENs on ES signal (1600/500/4) block 1
Boron Precipitation Control
Methods to control
Preferred (first 24 hours)
Secondary (after 5 days)
Preferred: DHR dropline to DH-P-1B suction header which is lined up to the sump and then returned to core via CF nozzles
Secondary: Aux spray (DH-V-64) through pressurizer via DH-P-1A
After 5 days aux spray alone will prevent boron precipitation
Pump vortexing
May occur when?
Low water level in hot leg coupled with what will result in vortexing?
Why is it bad?
May occur during drain down condition
Low water level in hot leg coupled with high DHR flow rate will result in vortexing
Risk air intrusion into the DHR system
Vortex formation curve
The lower the level…
The lower the DHR flow permitted
Indications of vortexing?
Oscillating motor current
Oscillating pump discharge pressure
Oscillating pump discharge flow
Noise/vibration
When is Piggyback mode used?
Used when BWST <15ft and RCS temp >25F superheat or LPI flow <1250 gom in each LPI line
Loss of DHR actions
Urgency to restore DHR cooling:
Local boiling can occur at the fuel pins before bulk temp reaches what temp?
Sustained loss of heat removal can result in?
212F
Core uncovery
Minimum RCS venting
If decay heat can make steam, must vent to atmosphere to keep RCS pressure what?
Low
The longer since shutdown, the what decay heat remains, the what vent area required?
The less decay heat remains, the less vent area required
Decay heat/RCS cleanup
Cleaned water returns to what?
To the suction side of the DH-P-1A
Decay heat removal
DH-C-1A/B should be properly filled and vented to prevent what on tubes and baffles prior to starting a pump?
To prevent impact or water hammer forces on tubes and baffles prior to starting a pump
Decay heat removal
DH-C-1A/B
Do not exceed what temp on DH coolter dT
Max allowed DH flow through a DH cooler is
200F
4500 gpm
Cooldown
RCS> what temp RCS cooldown rate is what temp/hr or 15F in 9 min?
RCS >255 RCS cooldown rate is 100F/hr or 15F in 9 min
Pressurizer cooldown rate is what?
100F/hr
RCS cooldown rate on natural circulation is what?
50F/hr
Limits and precautions
Low pressure injection/ES standby
Throttle DH-V-4A/B to maintain LPI flow indication < what gpm?
<3300 gpm
DH-P-1A/B
Min allowable flow for continuous operation of a DH pump is how many gpm?
The minimum recirc line provides approximately how many gpm at DH pump shutoff head?
100 gpm
150 gpm
Do not operate DH pump in minimum recirculation mode without cooling of the recirculating fluid for longer than how many minutes?
10 minutes
Containment
Purpose
Containment systems provide the last of the 3 boundaries (fuel cladding, RCS, RB) between fission products and the public
RB pressure and temp control
Pressure
Internal calculated accident press of 50.6 psig, caused by a hypothetical LOCA
RB pressure and temp control
Temp
Maintain the following RB conditions:
Average air temp below 320 ft elevation <120F
Average air temp above 320 ft <130F
>70F when shutdown/refueling for NDTT of CF tanks
<150F for concrete protection (degradation at 200F)
Penetrations
Hot mechanical penetration
Process fluid greater than what temp?
Insulation between pipe and cooling jacket protects concrete from heat damage > what temp?
150F
200F
Penetrations
cold mechanical penetration
process fluid greater than what temp?
electrical penetrations
Nitrogen (what pressure?) is used instead of air to limit what?
150F
30#, used instead of air to limit cable insulation breakdown
Containment isolation valves
4 types of process lines and their isolation valve requirements:
Type 1-Type IV
Type-1 = lines connected directly to RCS
Type-2 = lines connected directly to RB atmosphere
Type-3 = lines not directly connected to RB/RCS (low rupture probability), with at least one external valve; closed loop considered second isolation
Lines never opened during reactor operation
RB purge valves AH-V-1A/B/C/D
Used to control temp/press and airborne rad levels inside containment for personnel access
Do NOT USE PURGE to do what?
Do NOT use purge to control RB temp
RB purge valves AH-V-1A/B/C/D
The valves close automatically in response to what 3 things?
RM-A-9-HI
4# ESAS
RTI
What to know about door positions in control room?
On the PLF, there are individual door position indications and alarms in the control room
Equipment hatch
There a what rubber seal around the outside of the flange with a testable interspace between inner and outer seal
Double “O” ring silicone rubber seal
Equipment hatch
When containment is established, what from the PP tanks is used to pressurize and maintain inter-space to how much pressure?
IA from PP tanks
Maintain inter-space to 60#
RB sump
Normal level > how many inches (level maintained > how many inches? And why?
Normal level >23”
Level maintained >15” to keep drain line covered to act as a seal between RB atmosphere and AB
RB sump
Overflows to ECCS sump at what level?
How many gallons/inch
Overflows to ECCS sump at 69”
9 gallons/inch
RB sump drain valves WDL-V-534/535
Power supplies?
WDL-V-534 powered from XCC
WDL-V-535 powered from XCL
RB sump drain valves WDL-V-534/535
Both close on 3 conditions (for 2 of them state each channel)
Reactor trip isolation (534 on A/535 on B)
4# ES actuation (534 on A/535 on B)
RM-A-9 gas channel high alarm
WDL-V-535 auto closes on it’s own (not with 534) on what?
Auto closes on low level of 23”
Tech specs
Containment integrity set when:
3 things are met
Reactor coolant pressure >300 psig
Reactor coolant temp > 200F
Nuclear fuel in the core
RB Sump
Instrumentation
WDL-LT-804/805 (normal sump)
High alarm at what level?
Overflows to ECCS sump at what level?
55”
69”
Penetration cooling system
Maintain concrete temperatures around specific reactor building penetrations below what allowable temp to prevent concrete degradation?
200 F
Penetration cooling system
On loss of cooling, how much time to reach what temp?
15-30 mins to reach 150F
Penetration cooling system
Two fans (AH-E-9A/B)
Each fan is what percent capacity does it have auto start features? How must the standby fan be started?
Power supply?
100% capacity
No auto start
Standby fan must be started manually
1A/B ES MCC
Penetration cooling system
Activation of any of the following protective devices will trip the running fan and close the running fan’s discharge damper (AH-D-91A/B):
Fan intake fire/smoke detector (TS-671)
Fan discharge temp high at 195F (TS-706A/B)
AH-E-9A trips on an ES signal (1600/500/4 load shed)
Penetration cooling system
Dampers
Inlet senses inside or outside air? From where?
Inlet senses outside air temp from turbine building air shaft
Penetration cooling system
Dampers
At what temperature sensed which dampers open?
<75F AH-D-90 inlet from turbine building air shaft is open
>75F AH-D-89 inlet from outside airshaft (AIT) is open
Penetration pressurization
3 subsystems, what are they and their purpose?
Main- supplies constant 60 psig air to the RB equipment access plug flange
Instrument air is the ONLY air supply to the Main subsystem
Electrical- continuously pressurizes RB electrical penetrations with N2 to 30 psig to prevent deterioration of epoxy seals
Purge interspace- pressure source for the piping between the two RB purge supply valves and between the two RB purge exhaust valves
During normal operation, instrument air is reduced to what pressure and is supplied through what to main subsystem manifolds?
Instrument air is reduce to 60 psig and is supplied through individual flow roto-meters to main subsystem manifolds C,J, and N.
IA pressurizes what around the perimeter of the equipment access hatch plug?
‘O’ rings
The normal electrical subsystem manifolds (which ones? 4 of them) are pressurized by what which is reduced to what pressure?
Manifolds D,E,F, and G
Pressurized by nitrogen
Which is reduced to 30 psig
How many purge interspace tanks are pressurized to what pressure band by IA and float on the IA header?
2 purge interspace tanks
Pressurized to 85-100 psig by IA
Limits and precautions
Elevated Containment temperature
Containment temperature affects the what contained in the reference leg of the level instrumentation?
Fluid density
Limits and precautions
Elevated containment temperature
Elevated temperatures of the reference leg will result in what?
Erroneously HIGH OTSG and pzr level indications
Limits and precautions
Elevated containment pressure
Containment pressure affects the what pressure for pressure indication?
Reference pressure
Limits and precautions
Elevated Containment Pressure
Elevated containment pressure results in which pressure instrumentation reading what by the amount of the elevated containment pressure?
Elevated containment pressure results in RCS and OTSG pressure instrumentation reading LOW by the amount of the elevated containment pressure
Limits and precautions
OP-TMM-244-901
Containment isolation
Prior to opening a CIV after automatic closure, verify all the following:
Containment and RCS rad levels have been assessed based on radiation monitor readings or samples
The integrity of the system have been confirmed (stable surge tank level, visual inspection or ability to hold pressure)
The emergency director, or shift manager if E-plan not activated concurs with the need to open the valve(s)
Installed rad monitors or portable monitors are available to detect any release that may result from opening the valve
Containment integrity and Access limits
At least one door on each of the personnel and emergency air locks shall be closed and sealed
One door of personnel hatch or emergency hatch may be open for up to 24 hrs for maintenance, so long as other is shut and found to meet criteria 24 hrs prior
During the handling of irradiated fuel in the reactor building, at least one door in the personnel and emergency air locks shall be capable of being closed
NN-2-7 RB air temp high alarm response
Average air temp below 320 ft elevation is what > what temp?
Average air temp above 320 ft >what temp?
Below 320ft >115F
Above 320ft >125F
NN-2-7 RB air temp high alarm response
Manual actions
IAAT average temp above 320ft is approaching what time or avg temp below 320 is approaching what temp, then initiate op-tm-530-440 to do what?
Above 320 ft is approaching 130F, below 320 ft is approaching 120F, then initiate controlling RB air temp using RBEC system
NN-2-7 RB air temp high alarm response
Manual actions
IAAT avg temp above 320ft increases to >130F what temp, or avg temp below 320ft increases to >120F then perform the following
Ensure compliance with tech spec 3.17
Initiate RB emergency cooling
Reactor building
Except as provided in spec 3.6.6, 3.6.8, and 3.6.12, containment integrity shall be maintained whenever ALL three of the following conditions exist:
Reactor coolant pressure is ≥300 psig
Reactor coolant temp ≥200F
Nuclear fuel is in the core
The reactor shall NOT be critical when:
The reactor building internal pressure exceeds 2 psig or 1.0 psi vacuum
When containment integrity is required, if a CIV is determined to be inoperable:
(1 of 2)
For lines isolable by 2 or more CIV(s) required to isolate the penetration shall be verified operable. If inoperable valve is not restored within 48 hours, at least on CIV in the line will be closed or the reactor shall be brought to HOT SHUTDOWN within the next 6 hours and to the Cold Shutdown condition within an additional 30 hours
When containment integrity is required, if a CIV is determined to be inoperable:
(2 of 2)
For lines isolable by one CIV, where the other barrier is a closed system, the line shall be isolated by at least one closed and de-activated automatic valve, closed manual valve, or blind flange within 72 hours or the reactor shall be brought to HOT SHUTDOWN within the next 6 hours and to the COLD SHUTDOWN condition within an additional 30 hours.
If inoperability is due to reasons other than excessive combined leakage, due what to the associated valve and within how long verify that the associated valve is what?
Close the associated valve, and within 24 hours verify that the associated valve is OPERABLE
If inoperability is due to excessive combined leakage, within how many hours restore the leaking valve to what?
Within 48 hours, restore to OPERABILITY
Personnel or emergency air locks
requirements
At least one door in each of the personnel or emergency air locks shall be closed and sealed
One door of the personnel or emergency air lock may be OPEN FOR MAINTENANCE, REPAIR, OR MOD PROVIDED THE OTHER DOOR OF THE AIR LOCK IS VERIFIED CLOSED WITHIN 1 HOUR, LOCKED WITHIN 24 HOURS, AND VERIFIED TO BE LOCKED CLOSED MONTHLY.
Entry and exit is permissible to perform repairs on emergency air lock components. Entry and exit is permissible for 7 days.
Polar crane
Reactor building polar crane hoists shall not be operated over the what when any fuel assembly is being moved?
Fuel transfer canal
Polar crane
During the period when the reactor coolant system is pressurized above what pressure? And is above what temp? and fuel is in the core, reactor building polar crane hoists shall not be operated over the what?
300 psig
200F
Over the steam generator compartments
RB air temp
Primary containment average air temp above 320 ft shall not exceed what temp? and average air temp below 320 ft shall not exceed what temp?
130F
120F
While the reactor is critical the above stated temp limits are exceeded, the average temp shall be reduced to the above limits within how much time or be in what condition in how much time? And what condition within the following how many hours?
8 hours or be in at least HOT STANDBY within the next 6 hours.
And in cold shutdown within the following 30 hours
Components
Heaters
On temp, off temp?
Sensed where?
Low level heater cutout at what level?
50F ON, 55F OFF
Sensed at 52ft in tank
Low level heater cutout at 6.3ft
BWST
Based on T.S. must be:
> 350,000 gal (56 ft)
2500 ppmb
40F
DH-T-7 ECCS sump
Overflow level?
86”
DH-V-5A/5B
Power supply
What does it do on ES signal and which ones?
Normal position?
1A/1B ESV MCC
Open on ES signal (1600/500/4) block 1
Normally open
DH-V-5A/5B
Manually close DH-V-5A/B when:
BWST lowers to 6.33’ OR
RB flood level>56”
RB flood level <37” is -a NPSH concern for BS pumps
DH-V-6A/B
BS pump suction from RB ECCS sump
Accidental operation would allow BWST to what to where?
Gravity drain to RB sump?
DH-V-6A/B
BS pump suction form RB ECCS sump
Manually (from CR) open DH-V-6A/B when what at what level?
When BWST lowers to 9.5’
BS-V-3A/B
Opens on what pressure ES?
Opens on 4# ES signal ONLY
BS-P-1A/B
Power supply
Cooled by what?
1D/1E 4kv
BS-P-1A/B
With no DR pump running the BS can continue to run without any temp concerns until what?
Until suction is swapped to the ECCS sump. Then is when temps start to rise.
BS-P-1A/B
Pump flow limitations
Flow is limited to 1100 gpm by flow orifice
Shutdown BS pump if flow is <60 gpm for pump protection
Shutdown BS pump if flow is >1400 gpm to ensure LPI suction
BS-P-1A/B
Start signals
Auto Start, need both conditions present:
Block 4 permissive from ANY ESAS signal (1600/500/4)
AND
30# RB pressure (2/3 logic 200 series switches)
-BS-P-1A/B each have 3 individual switches
-these pressure switches are different from RB 30# ESAS RB ISOLATION (900 series switches)
CAUTION
To prevent challenging the ECCS strainer design…
Building spray must be shut down within 24 hours
BS-P-1A/B
Manual start
Control Console
Verify valve lineup prior to starting BS pump, suction and discharge valve normally what and not what?
Normally shut and not interlocked with pump
BS-V-1A/B
Position on which ES signal?
OPEN on 4# ES signal ONLY
Reactor Building spray headers
2 main headers (one each train)
Each header has a flow orifice installed to:
-Restrict flow within pump design limits (1100 gpm)
-Achieve design flow rate through spray headers
Pressure Sensing Manifolds
Provide input to:
BS start (2/3 logic) 200 series:
PS- 283/286/289 30# BS-P-1A start
PS-284/287/290 30# BS-P-1B start
ESAS RB Isolation (2/3 logic) 900 series
PS 932/933/934 A train 30# Valves
PS 935/936/937 B train 30# Valve
ESAS 4# (2/3 logic)
PT-282/285/288 (4 psig)
RPS- reactor trip (2/4 logic)
PS – 672/673/674/675
HSPS – EFW actuation (2/4 logic)
PT- 1186/1187/1188/1189
TSP
Provides a passive mechanism for post LOCA sump water buffering
The TSP loaded inside of the baskets will dissolve in post accident flooding and will be mixed within the ECCS system to maintain TB sump ph range of what within how much time at what temp?
7.3 to 8.0 (Raise pH)
30 mins at 30 deg C
Operating parameters
Pump flow limitations:
<60 gpm- Shutdown for pump protection
>1400 gpm – Shutdown Ensure NPSH for LPI
1100 gpm – Flow Orifice
BS-P-1A/B pump start
Two conditions much be present
Block #4 permissive ANY ESAS 1600#/500#4# (permissive goes away if ES signal defeated)
AND
30# RB pressure (not esas)- can’t be defeated
2 of 3 pressure logic (200 series)
3 on each BS P
Manual ESAS actuation
Manual 1600#, 500#, 4# will provide necessary block #4 permissive for pump start
Bs-v-1a/b and bs-v-3a/b will only open on 4# esas
Bs-p-1a/b will not start when esas manual 30# is actuated
30# pushbutton will not actuate building spray
Manual initiation of building spray
First 2 out of 4 conditions (goodluck)
RCS leak >500 gpm at 1600#
And, significant breech in containment exists
Tclad >1400F OR failed fuel is expected to exceed 5% And,
RB pressure >5# OR a significant breech in containment
Manual initiation of building spray
Last 2 out of 4 conditions (goodluck)
Child thyroid does> 5 REM at site boundary due to containment leakeage
IAW severe accident management guidelines
Manual shutdown of Building spray
1 of 2 conditions
RB pressure has been reduced to <5# And RM-G-22/23 are below hi alarm setpoint or TSC has determined that I-131 concentration is acceptable
Manual shutdown of Building spray
2 of 2 conditions
Operating time is approaching 24 hours
Heat removal capability is no longer effective
RB equipment damage may worsen
Limits and precautions
To avoid overheating:
Do no operate a BS pump for more than how long with flow less than how many gpm?
More than 60 seconds
With flow less than 60 gpm
Limits and precautions
To avoid overheating:
How many successive starts are allowed for the BS pump motor with the motor at either normal or ambient temp?
2 successive starts
