ESFAS

Question 1

Discuss the basis for ESFAS.

Answer 1

Limits core damage and minimize offsite releases during design bases events by the actuation of systems designed to provide core cooling, establish containment isolation, and protect containment integrity

Question 2

List the inputs to ESFAS.

Answer 2

• RWT level (4)
• Pzr pressure (4)
• Ctmt pressure (4)
• Ctmt radiation (4)
• SG A pressure (4)
• SG B pressure (4)

Question 3

Discuss what is contained by the four ESFAS Measurement Channels (MA, MB, MC, MD).

Answer 3

• Trip bistables.
• Isolation modules.
• Auto and manual test circuits

Question 4

Discuss what the two Actuation Trains (SA & SB) each contain.

Answer 4

• Actuation modules with logic matrix.
• Isolation modules.
• Auto and manual test circuits.
• Output relays.
• A separate enclosure for “C” component actuation circuitry.
• Each train has parallel output relays for “C” CCW, ICW, and Charging pump.

Question 5

Discuss EDFAS interfaces.

Answer 5

RPS Instrumentation inputs that is shared.
a) Pressurizer pressure
b) Containment pressure
c) S/G pressure A
d) S/G pressure B.
* Radiation Monitoring System shares CIS monitors.
* ATWS/DSS shares PZR Pressure

Question 6

Discuss the ESFAS Measurement Cabinets.

Answer 6

• Four measurement cabinets (MA, MB, MC, MD) are located behind RTGB 106 [206] separated by metal barriers.
  Channel MA: ‘A’ Train Power: (MA instrument bus)
  Channel MC: ‘A’ Train Power: (MC instrument bus)
  Channel MB: ‘B’ Train Power: (MB instrument bus)
  Channel MD: ‘B’ Train Power: (MD instrument bus)
• ATI located in {MA Cabinet on Unit 1} and [SA Actuation Train on Unit 2]

Question 7

If an ‘A’ MSIS signal is generated, what indications will be present?

Answer 7

• The ‘A’ MSIS handswitch “RED” light will illuminate. The ‘B’ MSIS handswitch “RED” light will NOT illuminate, but the ‘B’ train MSIS components will reposition.
• No matter which train gets the actuation signal, interposing relays ensure actuation of both trains of components

Question 8

How are ESFAS bistables tripped?

Answer 8

UNLIKE RPS, WE DO NOT PULL THE TRIP BISTABLES FOR ESFAS
WE ONLY PULL THE ISOLATION MODULES*

Question 9

Discuss Auto Test Insertion Module (ATI).

Answer 9

• {Located on Panel MA} [Located on Panel SA]
• Continuously monitors the ESFAS operability by performing on-line testing of the ESFAS circuitry.
• Accomplishes by continuous “pulsing” of actuation circuitry:
• Under-pulse: A 5% under setpoint signal to check for no actuation.
• Over-pulse: A 5% over setpoint pulse to check for actuation
• The ATI inserts signals into 2/4 bistable actuation flowpaths:
  a) It inserts an under pulse; and then monitors that the bistable DOES NOT trip
  b) It inserts an an over pulse; and then monitors that the bistable DOES trip
• Why doesn’t the ATI module signal generate an ESFAS actuation signal?
  The ATI test signals only trip the bistables/actuation modules for 2 milli-seconds
  a) Output relays need signal present for ~ 30 milli-seconds to actuate
  b) Signal resets before output relays can “actuate” on the signal
  c) No actual component actuations occur

Question 10

Discuss ATI Test LEDs.

Answer 10

• Not illuminated – Means bistable tripped on under-pulse.
• “Constantly” illuminated or Illuminated for a longer time – means failure to trip on over-pulse.
• Either results in Annunciator alarm and indicator lights on ATI panel.
• Test Panel is for I&C to periodically test and verify the B/S trip setpoints

Question 11

Discuss ESFAS Actuation Cabinets.

Answer 11

• Two trains (SA, SB) with 2 cabinets per train
• Each cabinet uses auctioneered power supplies to ensure the loss of one power supply will not cause an actuation
• Cabinet SA: Dual Powered from MA & MC instrument buses
• Cabinet SB: Dual Powered from MB & MD instrument buses
• Actuation modules:
  a) Input to the actuation module is isolation module output
  b) Develops the 2/4 actuation logic
  c) Logic signal development from B/S to Actuation Logic is “electronically” generated and passed (i.e., no relays)

Question 12

Discuss ESFAS Signal Flowpath.

Answer 12

Instrument Channels
2/4 Logic Matrix
Actuation Module
Output Relays
Equipment Operation

Question 13

Discuss ESFAS Block Modules.

Answer 13

• Output is signal to actuation relays.
• Applicable to SIAS and MSIS only.
• Requires 3/4 logic to block – meaning you must have 3/4 channels at the block setpoints

Question 14

Discuss ESFAS Blocking.

Answer 14

• Requires key switch manipulation to block the applicable ESFAS signal
• Amber light lit above Block key switch
• Annunciator should light for Block permissive
• When switch is taken to block, then red block light should come on and amber light will go out
• Block annunciator will also come in.

Question 15

Discuss ESFAS Manual Actuation/Reset Pushbuttons.

Answer 15

• It is a two function switch which will allow actuation or resetting of SIAS or CIAS
• Signal actuation requires two actions. First a pushbutton must be held depressed and then a control switch is taken to “Actuate”
• For reset, positioning of the switch to the “Reset” position is all that is required. (Assuming no signal is present, or signal has been blocked)
• To reset an ESFAS signal: You must either block the actuation signal, or not have the signal present.
• Can’t block containment pressure into SIAS [MSIS]

Question 16

Discuss EOP-99 additional reset criteria.

Answer 16

SIAS
Unit 1
CTMT Pressure < 4 psig and not rising
Low RCS pressure input met or blocked
Unit 2
CTMT pressure < 3.4 psig and not rising
Low RCS pressure input met or blocked

CIAS
Unit 1
CTMT Pressure < 4 psig and not rising
CTMT Radiation is < 8 REM and not rising
SIAS not actuated or is reset
Unit 2
CTMT pressure < 3.4 psig and not rising
CTMT Radiation is < 8 REM and not rising
SIAS not actuated or is reset

MSIS
Unit 1
Low SG Pressure input met or blocked
Unit 2
Low SG Pressure input met or blocked
CTMT pressure < 3.4 psig and not rising

CSAS
Unit 1
No extra criteria
Unit 2
No extra criteria

Question 17

Discuss ESFAS Normal / Isolate Switches.

Answer 17

• Allows remote operation of components and isolation from Control Room circuitry
• Incorporated into component circuitry so that a fire in the control room would not result in unwanted component actuations during a control room evacuation
• Switch is normally in “Normal”
  a) Electrically inserts the ESFAS auto initiation circuitry into component control circuits.
  b) Administrative controls ensure these switches properly positioned.
• Normal/Isolate in “Isolate”;
  a) This position defeats all auto ESFAS signals by electrically “removing” the auto initiation circuitry from component control circuits.
  b) Also electrically removes all control room circuitry from the component control circuitry.
  c) Component would be rendered inoperable
  d) “Isolate” position annunciated when in “Isolate.”

Question 18

Discuss Safety Injection Actuation Signal.

Answer 18

Designed to assist with reactivity control and inventory control post RX Trip with a LOCA by injecting borated water into the RCS.
Auto initiated from:
PZR Press Low (2/4) {≤ 1600}[≤ 1736] psia
CNMT Press Hi (2/4) {≥ 5.0} [≥ 3.5] psig
De-energizes the bistable to actuate
Can be manually actuated from the RTGB

Block Feature:
* Via a key switch. Train specific capability. Allows a controlled C/D without SIAS actuation
* Can only occur when 3/4 PZR pressure channels decrease to {≤ 1725} [≤ 1836] psia
* Blocks pressurizer pressure input only.
* Failure to Block SIAS (or MSIS) during a cooldown would result in a full actuation and an LER to the NRC
* Can still manually actuate if blocked – blocks auto actuation only
* Generates Annunciator & red light on cabinet

Auto Unblocks when:
* 2/4 PZR pressure channels are {> 1725} [> 1836] psia (with dead band)

Resetting SIAS
* Unit 1- components may change position (BAM Pumps will stop if on automatically)
* Unit 2- only overridden components will change position, such as CCW N header valves
* Remember, to reset a signal, you must be less than the initiation setpoint or have signal blocked

Question 19

Discuss Containment Isolation Signal {CIS} [CIAS].

Answer 19

Designed to isolate the Containment from all but essential systems during a LOCA
Auto initiated from:
SIAS Actuated
CNMT Press Hi (2/4) {≥ 5.0} ]≥ 3.5] psig
CNMT Radiation Hi (2/4)
(Modes 1 – 4) 10 R/HR
(Mode 6: When moving recently irradiated fuel) 90Mrem/HR

De-energizes the bistable to actuate
Can be manually actuated from the RTGB
There are NO Blocks of CIS [CIAS]
Resetting Unit 2 CIAS could result in the SBVS fans swapping to the refueling pool from the Annulus if refueling pool high radiation levels (i.e., > 15 mr/hr) are present.

Question 20

Discuss Main Steam Isolation Signal.

Answer 20

Designed to mitigate the consequences of a main steamline break
Auto initiated from:
S/G Press Low (2/4) ≤ 600 psia
[CNMT Press Hi (2/4) ≥ 3.5 psig]

When 2/4 instruments exceed the actuation setpoint (not auctioneered like RPS)
Can be manually actuated from the RTGB
Interposing Relays: Actuation logic on either S/G will actuate a MSIS on BOTH S/Gs.

Block feature
* Used during controlled cooldown.
* Cannot block Hi CTMT Pressure signal – [ Which is a Unit 2 only signal]
* Block procedurally controlled and similar to blocking SIAS

Unit 2 Only Design
* The Unit 2 MSIV design could allow some backflow of steam from the non-ruptured S/G into containment BEFORE the MSIVs would auto close on low S/G pressure.
* Therefore, by closing the Unit 2 MSIV’s on High CTMT pressure, we would assure that the Unit 2 CTMT pressure rise from the non-faulted S/G is terminated.
This setpoint assumes that the MSIV on the faulted S/G fails to close, which lines up a flowpath from the non-faulted S/G to the faulted S/G through the turbine bldg. steam header.

Question 21

Discuss Containment Spray Actuation Signal.

Answer 21

Designed to limit containment peak pressure during a LOCA

Auto initiated from:
Unit 1
SIAS Actuated
AND
CNMT Press Hi-Hi (2/4) ≥ 10.0 psig
Unit 2
SIAS Actuated
AND
CNMT Press Hi-Hi (2/4) ≥ 5.4 psig

Energizes to actuate to prevent a failed actuation relay from causing an inadvertent actuation
There is NO Block feature for CSAS

Question 22

Discuss Recirc Actuation Signal.

Answer 22

Designed to swap injection pump suction to containment sump as RWT empties during LOCA injection phase

Auto initiated from:
RWT Level (2/4) {4 ft} [5.67 ft (6 ft – nominal value)}

Energizes to actuate to prevent a failed actuation relay from causing an inadvertent actuation
There is NO block feature for RAS

Question 23

Discuss Aux Feedwater Actuation Signal.

Answer 23

Considered part of ESFAS

Auto initiated from:
S/G Level (2/4) ≤ 19 % for {235} [210] seconds without level rising ≥ 29 %

Deenergize to actuate

Question 24

Discuss ATWS / DSS Actuation Signal.

Answer 24

Protects the RCS pressure boundary from severe over pressure due to a failure of the RPS to trip the reactor when required. DBE for the DSS is total loss of feed with a failure of the RPS to trip the reactor

Auto initiated from:
Hi RCS Pressure (2/4) ≥ 2450 psia

• Setpoint: Fed from PT1103A-D
• Actually set at 2437.5 psia

On 2/4 high pressurizer pressure the DSS actuates to open a line contactor in series with each CEA MG set, de-energizing the CEA bus
Actuation relays are energized to actuate
Alarms when ATWS/DSS channel actuated or bypassed.
No manual actuation – from RTGB
No Block feature– from RTGB
DSS cannot be manually Actuated or Blocked from the RTGB; can be blocked (but not actuated) with a key-switch located on the Actuation Module in the SA & SB Actuation Cabinets
ATI performs continual testing of ATWS circuitry

Question 25

Discuss ESFAS Measurement Channels: (Sensor Channels).

Answer 25

• Have 12 Trip Bistables
• Trip on Loss of Power to the Measurement Channel only
• Actuation Cabinet sees this as trip input for all Signals that de-energize to Actuate SIAS, CIAS, MSIS
• Measurement Channel Bistables Reset Automatically when the tripped condition clears
• However the Light on the bistable module will remain lit until it is depressed by operator
• This also clears the annunciator alarm
• Bypass Key-switches places actuation logic in 2/3

Question 26

Discuss what happens if a Measurement Channel Bistable Trip Module Is Removed.

Answer 26

Unit 1 -
The circuitry is placed in a BYPASS condition. Now in 2/3 logic
Unit 2 -
The circuitry is placed in a TRIP condition. Now in 1/3 logic

Question 27

Discuss Bypass All 4 Channels of ESFAS.

Answer 27

• When RCS Temperature < 200F, Prevents inadvertent safeguards actuations
• Other 3 sets of Bypass Keys are kept in the MT&E AREA
• Keys verified in MT&E AREA by a QC Hold Point prior to RCS temperature exceeding 200 F

Question 28

Discuss how to Place An ESFAS Measurement Channel (Sensor Channel) In Trip.

Answer 28

• Must pull out BOTH Isolation Modules to get a trip that goes to each Actuation cabinet
• For MSIS - Only pull out the Isolation Module for the desired train

Question 29

Discuss how to Place an ESFAS Trip Unit in Trip.

Answer 29

RPS Pull out the Trip Unit Bistable
ESFAS Pull out BOTH the Upper & Lower Isolation Modules
AFAS Contact I&C to install Jumpers

Question 30

Discuss what happens if an ESFAS Measurement Cabinet loses power and another channel is failed.

Answer 30

Components that receive these signals actuate
1) SIAS
2) CIS [CIAS]
3) MSIS

Components that receive these signals don’t actuate
1) CSAS - Do not want to spray down CNMT for an inadvertent actuation
2) RAS - Do not want to have ECCS pumps aligned to empty CNMT sump
3) DSS (ATWS) - Not an ESFAS Signal

Question 31

Discuss Manual ESFAS Actuation.

Answer 31

• Manual Actuation and Reset is done from the RTGB (RESET/AUTO/ACTUATE)
• Actuation - Hold in Think PB & position the Actuation Switch to Actuate
• Reset - Take the Actuation Switch to the Reset position
• Manual Actuation will always work regardless of Logic

Question 32

Discuss the Effects of ESFAS Actuation on Plant Components.

Answer 32

• The ESFAS is designed to protect the reactor during various credible accident conditions.
• The following details the actuation signal(s) that are expected for the listed accidents.
• Loss of Coolant Accident (LOCA) SIAS, CIS [CIAS], CSAS
• Main Steam Line Break (MSLB) outside containment – MSIS
• MSLB inside containment – MSIS, SIAS, CIS [CIAS], CSAS

Question 33

Discuss SIAS Effects on Plant Components.

Answer 33

• CCW ‘N’ header isolates
• Four containment fan coolers run [4 run in slow speed]
• HPSI/LPSI pumps start and safety injection headers unisolate
• RAB emergency exhaust fans start; normal exhaust fans secure
• SIAS signal generates CIS [CIAS]
• Isolates main feedwater by closing MFW pump discharge valves (after a 30 second time delay) and the 2 MFIV’s (Unit 1 only) [there is no feedwater isolation in Unit 2 on SIAS]
• Isolates CCW to/from RCPs
• BAM pumps start, gravity feed and emergency borate valves open, Isolates VCT, Isolates letdown
• 3 [2] charging pumps start
• Isolates ICW to TCW and the OBCS heat exchanger (MV-21-2 and MV-21-3 close)
• EDG’s start
• [Trips MG set output breaker]
• [Note: SIAS will Open the MG Set INPUT Breaker on Unit 2 Only.]
• SIAS provides direct actuation containment isolation in event of small break LOCA

Question 34

Discuss CIS [CIAS] Effects on Plant Components.

Answer 34

• Isolates containment penetrations
• Isolates BD & BD sample isolation valves
• Station Air isolation valve
• CR isolation & Emergency Filtration Systems

Question 35

Discuss CSAS Effects on Plant Components.

Answer 35

Containment spray pumps start
Unisolates containment spray header
Unisolates the Iodine Removal System by opening NaOH injection valves on Unit 1
[Hydrazine pumps start and discharge valves open due to CSP start circuit.]

Question 36

Discuss RAS Effects on Plant Components.

Answer 36

• Unisolates ECCS pump suction path from containment sump 30 sec
• Isolates ECCS pump suction path from RWT 90 sec
• LPSI pumps stop
• Isolates safeguards pump recirc path
• (Unit 1 requires RTGB 106 key-switch positioning)

Question 37

Discuss MSIS Effects on Plant Components.

Answer 37

• MSIV’s close, [Closes MSIV bypass valves]
• Main feedwater isolation valves (MFIV’s) close.
• On Unit 1, MSIS trips the main feedwater pumps and closes their discharge valves
• Trips the heater drain pumps and condensate pumps
• MSIS SA and SB each have a dedicated relay that trips all pumps.

Question 38

Discuss ESFAS Blocks.

Answer 38

3/4 Logic - Block using key-switches on RTGB
2 of 4 channels above block setpoint will automatically unblock
3 Lights
Green Not Blocked.
Amber 3/4 Block Permissive satisfied (out once blocked)
Red Blocked

Question 39

Discuss MG sets as applicable to ESFAS.

Answer 39

• CEA MG Set Output Breaker & Output Contactor Interlocks
• Output Line Contactor must be closed before the Output Breaker can be closed
• If the Output Line Contactor opens, the Output Breaker opens
• Output breaker interlocked to open if input breaker opens-prevents motoring MG on reverse power
• Unit 1 ATWS Opens Output Line Contactor @ 2437 psia
• Unit 2 ATWS Opens Output Line Contactor @ 2437 psia & SIAS Opens the Input Breaker

Question 40

Discuss effect of Loss of DC on ESFAS.

Answer 40

• Loss of a 1 DC bus WILL cause actuation of both channels of SIAS, CIAS, and MSIS
  They are de-energize to actuate, due to loss of power to 2/4 measurement channels (and actuation cabinet loses power).
• Loss of 1 DC Bus or de-Energization of an Actuation Cabinet WILL NOT cause actuation on CSAS, RAS, or DSS.
  A loss of power to the instrument channel would be seen by the CSAS, RAS, and DSS if it were not for the fact that the measurement cabinet will not pass the signal on if there is a loss of power to the cabinet. Therefore the signal is automatically bypassed to the remaining actuation cabinet. If a subsequent valid CSAS, RAS, or DSS signal (2/2) is generated, then the remaining actuation cabinet will cause an initiation on its associated side components only.

Question 41

Discuss ESFAS System Operation.

Answer 41

• At least 3 channels operable before going to Mode 4
• All channels of CNMT pressure, RWT Level, Ppzr, and Psg bypassed when < 200F
• All channels bypassed when < 140F (except Hi Rad CIS) – inadvertent actuation

Question 42

Discuss ESFAS Miscellaneous Info.

Answer 42

• LOOP will NOT start a Green Flagged CCW or ICW Pump
• SIAS will Start a Green Flagged CCW or ICW Pump (SIAS does not look at the flag)
• SIAS start of CCW/ICW pump, other pump in “Pull to Lock” & Proper Electrical Alignment
• (AB-A3) Normal/Isolate switch in Isolate would prevent ESFAS actuation
• All signals with the exception of MSIS will only actuate their respective components, i.e. if ‘A’ train of CSAS reaches its’ setpoint, only the ‘A’ containment spray components will actuate.
• If a measurement channel is bypassed or actuation signal is blocked with keylocks and you push the manual actuation pushbutton, the actuation will still happen.
• If a SIAS channel is bypassed and pressure goes above bypass setpoint, trip is re-enabled. If pressure subsequently lowers below the bypass setpoint, the trip is NOT bypassed again without operator action. (The key switch will not stay in bypass position)