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NLO Systems 2023 > SI- Safety Injection > Flashcards

SI- Safety Injection Flashcards

1
Q

What are the main purposes of the SI systems?

A

emergency core cooling
(safety injection)

residual heat removal
(shutdown cooling)

containment heat removal
(containment spray)

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2
Q

What are the main functions of the safety injection subsystem?

A

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

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3
Q

Why does the RCS need to be flooded and cooled by the SI system after a LOCA?

A

to prevent cladding failure

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4
Q

What are the main functions of the shutdown cooling system?

A

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

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5
Q

What temp. and pressure does shutdown cooling keep the RCS after shutdown?

A

under 350*F and 395 psia

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6
Q

What are the main functions of the containment spray system?

A

cools containment atmosphere with borated water spray

remove iodine from containment atmosphere

additional flow to shutdown cooling

remove heat from containment by shifting heat exchangers to recirc mode

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7
Q

Per design basis, what is the peak cladding temp. limit?

A

2200*F

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8
Q

Per design basis, maximum cladding oxidation shall not exceed what?

A

17% times total cladding thickness

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9
Q

Per design basis, What is the maximum hydrogen generation?

A

1%

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10
Q

Per design basis, calculated changes in core geometry shall be what?

A

amenable to cooling

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11
Q

What are the design requirements of the RWT?

A

20 minutes full flow for both SI trains and all pumps plus 10%

fill refueling pool

equal flows to all RCS injection points

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12
Q

Where do the SITs inject borated water?

A

all four RCS cold legs

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13
Q

How many SITs are there? What holds the discharge check valve shut?

A

4

RCS pressure

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14
Q

Where do the HPSI, LPSI and CS pumps take suction from?

A

RWT initially

RAS sump

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15
Q

Where do the HPSI and LPSI pumps inject borated water?

A

HPSI
respective hot leg and all four cold legs

LPSI
two cold legs

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16
Q

How does the SI system interface with PB?

A

PB provides power to the HPSI, LPSI and CS pumps

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17
Q

How does the SI system interface with PH?

A

PH provides power to SI valves

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18
Q

How does the SI system interface with PK?

A

PK powers SI valves and breaker control

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19
Q

How does the SI system interface with PN?

A

PN powers SI valve position indicators and instrumentation

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20
Q

How does the SI system interface with PE/DG?

A

PE/DG provides emergency standby power for SI

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21
Q

How does the SI system interface with NE/GT?

A

NE/GT provides emergency standby power to SI during station blackout

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22
Q

How does the SI system interface with CH?

A

CH supplies borated water (RWT)

purification for SDC

relief valve discharges

SITs drainage

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23
Q

Where do the SI relief valves relieve to in containment? Outside containment?

A

RDT

Equipment Drain Tank (EDT)

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24
Q

Where can the SITs be drained to?

A

RDT or RWT

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25
Q

How does the SI system interface with EW?

A

EW is cooling water to SDCHX

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26
Q

How does the SI system interface with GA (service gases)?

A

supplies nitrogen to SITs

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27
Q

How does the SI system interface with IA?

A

air supply to pneumatic operators, instruments and controls

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28
Q

How does the SI system interface with HA (Aux. building HVAC)?

A

cools SI pump rooms

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29
Q

How does the SI system interface with ESFAS/SA?

A

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

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30
Q

How does the SI system interface with BOP ESFAS?

A

BOP sends LOP/LS and load sequencer signals to SI

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31
Q

What is the rumble region of the LPSI pumps?

A

2500-3500 GPM

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32
Q

What kind of pump is the LPSI pump? Where are they located?

A

vertical, single stage centrifugal

40 ft Aux building w/ 50 ft access

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33
Q

What kind of pump are the HPSI pumps? Where are they located?

A

horizontal, eight stage, centrifugal pumps

aux building 40ft w/ 50 ft access

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34
Q

How does the HPSI pump increase the pressure of the water high enough to inject into the RCS

A

The HPSI pump groups several stages together in series to obtain a higher discharge pressure.

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35
Q

Where are the SITs located?

A

in containment on each respective cold leg

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36
Q

What pressure are the SITs held at?

A

600 psig

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37
Q

If the SITs are held at 600 psig, at what pressure will they inject borated water into the RCS?

A

below 600 psig

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38
Q

What are the valves between the SITs and the RCS cold legs?

A

two check valves and one motor operated valve

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39
Q

What is the status of the SIT motor operated valve during normal operation?

A

open with power removed

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40
Q

What is done with the SITs before RCS drops below 600 psig?

A

MOV is repowered and closed

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41
Q

How many SITs are needed to safely recover to core during a LOCA?

A

3 out of 4

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42
Q

How is the water injected into the core from the SITs?

A

The water is injected by means of the Nitrogen over pressure forcing the water into the core when the RCS pressure drops below the SIT pressure.

43
Q

Where are the recirculation sumps located? How many are there?

A

containment basement

2

44
Q

What is the purpose of the recirculated sumps?

A

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

45
Q

What is the low level in the RWT that causes a RAS?

A

9.4%

46
Q

What does a RAS do?

A

places the recirculation sumps in service

trips LPSI pumps

47
Q

Why does a RAS trip the LPSI pumps?

A

ensure NPSH for CS and HPSI

48
Q

What is the purpose of the Trisodium Phosphate (TSP) baskets in the containment?

A

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

49
Q

Is the RAS suction piping self-venting? Must it be kept full?

A

it is not self-venting and must be kept full

50
Q

What main components are used for SDC?

A

LPSI/CS pumps

SDCHX

LTOPs

valves and piping

51
Q

What are LTOPs?

A

Low temperature over-pressure protection valves

52
Q

What cools the SDCHX?

A

essential cooling water

53
Q

For SDC, which pump is preferred?

A

LPSI so the CS pump is available for emergency spray

54
Q

For SDC, can the LPSI and CS pump be used in parallel?

A

yes

55
Q

Where do LTOPs relieve to?

A

recirculation sump

56
Q

Where are the SDCHXs located?

A

aux building 70’

57
Q

What type of HX are the SDCHX?

A

shell and U-tube

58
Q

What removes RCS sensible heat and core decay heat and transfers that heat to the EW system?

A

SDCHX

59
Q

What is the set point on the LTOPs?

A

467 psig

60
Q

What is the purpose of the LTOPs?

A

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

61
Q

What is the purpose of containment?

A

third barrier to releasing fission products

62
Q

How does CS reduce containment temp. and pressure?

A

spraying subcooled borated water into the atmosphere

63
Q

Besides lowering containment temp. and pressure, what else does CS do?

A

reduces iodine in the containment atmosphere

64
Q

What are the major components of the containment spray sub system?

A

Containment spray pumps

Containment spray headers

Shutdown cooling heat exchangers (SDCHXs)

Spray isolation valve

65
Q

What type of pump are the CS pumps? What is the rumble region?

A

vertical, single stage, centrifugal pumps

1800-2800 GPM

66
Q

How long does it take for the CS pump to start after a SIAS or CSAS occurs?

A

15 seconds

67
Q

What is the purpose of the containment spray pumps?

A

They provide the motive force to push the water into the spray header to cool down and depressurize containment.

68
Q

What is the auto feature of the HPSI pumps?

A

auto start on receipt of a SIAS and CSAS

69
Q

What are the auto features of the LPSI pumps?

A

auto start on SIAS and CSAS

auto trip on RAS

70
Q

What is the auto feature of the CS pump?

A

auto start on SIAS and CSAS

71
Q

What are the power supplies for the HPSI, LPSI and CS pumps?

A

PBA-S03 and PBB-S04

72
Q

Which pump is used to recirculate the RWT?

A

LPSI

73
Q

What pressure will the pressurizer drop to before generating a SIAS?

A

1837 psia

74
Q

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?

A

3 pisg

75
Q

Which pump is used to fill the SITs?

A

the B HPSI

76
Q

What is the normal LPSI line up, through or bypassing the SDCHX?

A

bypassed

77
Q

What is the pressure that containment reaches before initiating a CSAS? How many pumps start?

A

8.5 psig

two

78
Q

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?

A

realigned for possible emergency operation.

79
Q

Will a loss of power to the (A) LPSI pump prevent the shut down cooling system from performing its’ job and why?

A

No, the shut down cooling system has redundant components that allows it to still perform its’ job.

80
Q

RWT being inoperable would mean what for the plant?

A

SI would not meet its safety function and core degradation may occur

81
Q

Without the CH system, What would happen to the chemistry of the RCS?

A

it would not get purified and no chemicals would be able to be added

82
Q

What would happen to the RCS if the SDCHX lost EW cooling?

A

RCS would heat up, undesirably.

83
Q

What is required for a SIT to OPERABLE?

A

MOV full open, power removed

limits in Surveillance Requirements (SR) for contained volume, boron concentration, and nitrogen cover pressure

84
Q

In modes 3 and 4, what must the pressurizer pressure be?

A

less than 1837 psia

85
Q

What is the tech spec for SITs while shutdown?

A

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

86
Q

What does ECCS stand for?

A

Emergency core cooling systems

87
Q

What is the tech spec for ECCS while operating?

A

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

88
Q

How long after a LOCA is the HPSI flow path diverted to both the hot and cold legs?

A

2-3 hours

89
Q

What is the tech spec for ECCS while shutdown?

A

mode 3- PZR pressure less than 1837 and RCS Tc less than 485*F

mode 4- ECCS has one HPSI subsystem

90
Q

What is the tech spec for the RWT?

A

modes 1-4, RWT must meet the limits for water volume, boron concentration, and temperature

91
Q

What is the tech spec associated with the Trisodium Phosphate (TSP)?

A

TSP baskets shall contain greater than or equal to 524 ft^3 of active TSP

must keep pH greater than or equal to 7

92
Q

describe the engineering study for RAS piping voids

A

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

93
Q

For the RAS piping study, what is the maximum allowable air void in the RAS piping?

A

5.45 cu-feet

94
Q

How far open do you throttle a vent valve initially?

A

1/4-1/2 open

95
Q

How many vent valves can be vented at one time?

A

1

96
Q

If air is present during venting, how far open can you throttle the valve in a controlled manner?

A

2 turns

97
Q

How long must a solid stream of water be seen prior to shutting a vent valve?

A

2 minutes

98
Q

What information must be provided to engineering when air is present during venting?

A

valve position required for air free flow

time to reach air free flow

99
Q

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?

A

you don’t increase valve turns and recorded in seconds until air free flow

100
Q

Describe the SI valve pressure locking mod

A

some have bonnet relief check valves discharging to the upstream line

some have pressure equalization lines that discharge to the suction of the valve

101
Q

Where does the “rumble” occur in the LPSI pump when operating in the Rumble Region? Why is it detrimental?

A

Occurs approximately one foot upstream of the pump impeller. Operation in the rumble region creates increased erosion of the piping and impeller

102
Q

What services does the Chemical and Volume Control system provide for Safety Injection?

A

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

103
Q

Where are the CS pumps located?

A

40’ aux. building w/50’ level access

104
Q

Concerning the Containment Spray pumps, what is the purpose of the minimum flow orifices?

A

Provide alternate flow path used during pump startup to prevent pump damage while operating against a closed system

NLO Systems 2023 (67 decks)

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