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LOIT 2020 SIM phase COPY > SGTR > Flashcards

SGTR Flashcards

1
Q

State the RU monitors that may indicate the presence of a SGTR or SGTL.

A

RU-4, 5: SG# blowdown monitors

RU-139, 140: MS Line Monitor

RU-141: Condenser Off Gas Monitor

RU-142: Main Steam Line N-16 Monitor

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2
Q

State the major steps in the mitigation strategy for at SGTR

A
  • Cool the RCS using both SGs until Thot < 540°F: low enough to prevent lifting SG safeties. (uncontrolled release)
  • Identify and isolate the most affected SG. (Stops the uncontrolled release)
  • De-pressurize the RCS to below SG safety setpoint (< 1135 psia). (controls 1° to 2° leakage and SGWLC)
  • Equalize pressure between RCS and affected SG (± 50 psi)
  • Maintain affected SG level 45-80% NR (tube covered and prevents overfill / lifting MSSVs)
  • Cooldown the RCS using the un-isolated SG
  • Place SDC in-service.
  • Cooldown the ruptured SG after SDC temperature criteria is met.
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3
Q

What indications would one use to diagnose a SGTR?

A

Abnormal RU trends or alarms on steam plant monitors.

unexpected SG level trends with indications of an RCS leak

SG chemistry results.

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4
Q

How does RU-7 AS cond receiver tank monitor respond to a SGTR?

A
  • First monitor to alarm during U2 SGTR.
  • Re-aligns AS Condensate Return to LRS (isolates path to main condenser)
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5
Q

How would RU-4/5 SGBD monitor respond to a SGTR?

A
  • Isolated by SIAS, AFAS and MSIS. Supplied from SG sample line. Slow transport time (~ 10 min)
  • Manually isolate associated SGBD if in High alarm (per ARP)
  • Leaks high in the SG tubes will be indicated on steam line activity.
  • Leaks low in the SG tubes will be indicated on blowdown monitors RU-4/5.
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6
Q

How will RU-141 Cond. Vacuum/GS Exh monitors respond to a SGTR?

A
  • RU-141b (Ch. 2): Most sensitive real time estimate of total tube leakage.
    • Alarms at 50 gpd tube leak
    • Not diluted by GS exhaust (only reads vacuum exhaust)
  • RU-141a (Ch. 1): Diverts CAR exhaust flow through the post filter blower unit. (Thru Filter)
    • Ch. 1 alarms at 1 gpm leak with 1% failed fuel (1440 gpd)
  • ~ 20 minute transport time
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7
Q

How will RU-142A-D M. Steam line N-16 monitors respond to a SGTR?

A
  • Alarm: detects 30 GPD leak in area of highest susceptibility (upper hot side tube bundle)
  • Tube leak: all rise due to proximity of RUs (affected 2 rise higher)
  • Indication will lower with reactor power (N-16↓)
  • Alarms on change in leak rate (“Urgent” alarm)
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8
Q

How will RU-139/140 MS line monitors respond to a SGTR?

A
  • May only detect > 10-15 gpm tube leak under normal failed fuel conditions at 100% power.
  • Response is proportional to reactor power (N-16 detectors). Post trip, may not see the leak unless major fuel damage.
  • Manually isolate associated SGBD if in High alarm (per ARP)
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9
Q

During performance of the SGTR ORP, when are RCPs required to be secured?

A

If Ppzr remains below the SIAS setpoint, then stop 1 RCP in each Loop.

If RCS Subcooling is < 24F, then ensure ALL RCPs are stopped.

If any RCP is approaching App 16 RCP trip criteria, then ensure operating limits are not exceeded.

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10
Q

How is the step in the SGTR ORP to cooldown to <540F performed and what is the basis for this step?

A

Cooldown RCS to Thot < 540°F.

  • Perform brief (ODP-1)
  • Use SBCS (not 1007/1008)
    • 1001 50-70% open in manual-manual, then 20% open when < 540°F
  • If SBCS not available, use:
    • (1) ADVs from MCR
    • (2) 1007/1008 SBCVs
    • (3) ADVs locally
    • One ADV per SG 50-70% open, then 20% open when <540°F
  • 540°F: prevent lifting MSSVs in isolated SG.
    • Below Tsat of the lowest MSSV.
  • Initial CDR is ≤ 100°F/hr
  • 35 min to start / 70 minutes to complete (TCA)
  • CRS logs initial temp in place keeper (Tc or REP CET).
  • Commence rapid cooldown to allow rapid SG isolation. Rapid as possible while maintaining control, then slow the cooldown at 540°F and continue to SDC entry conditions at < 100°F/hr.
  • If possible, do not use AFA (steam release). If AFA is used, intact SG steam supply should be used.
  • Degraded HPSI/charging may limit C/D rate.
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11
Q

Describe the step in the SGTR ORP to isolate the most affected SG and why this is done.

A

* When Thot is < 540°F, isolate the most affected SG using App. 113 or 114.

  • Assign to the OATC
  • At least one SG should always be available for DHR.
  • Isolates ADVs, MSIVs/FWIVs, AFW, steam traps, SGBD, AFA steam supply.
  • Isolating a SG restores containment integrity
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12
Q

Discuss the step in the SGTR ORP that begins depressurization of the RCS and include the basis for this step.

A

Depressurize the RCS to meet all of the following:

  • PPZR < 1135 psia
  • PPZR within ± 50 psia of ruptured SG
  • Within P/T limits and RCP NPSH limits
  • Use main or aux spray.
  • Start with both Aux Sprays, Main spray for fine control.
  • Control charging, letdown, or HPSI flow if SI throttle criteria are met.
  • If pressure cannot be reduced or maintained within band, use RCGVS to reduce pressure (App. 102)
  • HPSI should be throttled promptly when conditions are met. Reduces excess RCS inventory and allows pressure reduction.
  • 1135 psia: below MSSV setpoint (1st one lifts at 1250 psig)
  • Minimizes loss of RCS to the SGs (leakage ↓)
  • Prevents SG overfill and potentially causing a MSSV to stick open
  • Maintaining SCM and NPSH has priority over matching PPZR to PS/G.
  • Maintain RCPs running if possible. Minimizes adverse effects of dilution from back flow.
  • Use caution if using RCGVS to prevent exceeding CTMT SFSC limits that would require FRP entry.
  • 230 min TCA to equalize pressure (single SGTR)
  • 74 min TCA to equalize pressure (multiple SGTR)
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13
Q

State the required actions and time associated with dpressurizing the RCS.

A

Following a single tube SGTR equalize RCS pressure with affected SG rpessure prior to overfill: 230min. This minimizes the potential for loss of coolant to the secondary side and reduces the possibility of lifting the MSSVs. And maximizes ability to isolate the SG to stop the loss of primary inventory and release of radioactivity.

Following a SGTR of multiple tubes, initiate a cooldown and equalize RCS pressure with affected SG pressure(+50psig): 74 minutes.

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14
Q

State the TCA associated with action of isolating the SG during a single tube SGTR.

A

210 minutes from rupture.

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15
Q

State the maximum secondary side pressure, bases and actions to ensure it is not violated.

A

Psg is < 1135psia.

Prevents challenging the MSSV lowest setpoint.

Accomplished by a continuous RCS cooldown to SDC.

If challenged, use of MSIV bypass valve and SBCS to the condenser instead of to environment is desired. However, during use of SBCS, should the setpoint be challenged, use of ADVs to environment is preferred over letting the MSSV relief lift.

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16
Q

What are the methods of isolated SG pressure control available under various conditions such as:

Forced circulation vs Natural Circulation

Condenser Vacuum available or unavailable

A

The isolated SG will be cooled down and depressurized by any of the following:

Forced circ: use of backfeed from the secondary to the primary. This is available if Prcs is < Psg and a RCP is running. Not possible if in natural circulation due to the dilution process that would occur.

If condenser vacuum is available, the SG can be steamed to the condenser using MSIV bypass and SBCS.

If condenser vacuum is unavailable, the isolated SG can be fed to 80% NR and drained to 70% NR. This method is very slow due to the method of heat transfer and will only be effective if the leakrate is < the blowdown capacity. Finally the SG can be allowed to cool to ambient temperatures but is very time consuming, requiring up to 27 hrs to complete.

17
Q

Describe the available methods to reduce Prcs.

A

Aux spray and main spray.

Std App 102 RCGVS

18
Q

Why are the unaffected SG trap isolations restored following an MSIS?

A

Ensures that AFA remains operable if needed. Water backing up in the AFA steam supply lines would disable and damage the AFW pump. Critical steam trap blowdown operation must be performed within 2 hours of a high condenser reheat tray or hotwell level.

19
Q

Why is NR SG level used as the primary indicator on the isolated SG?

A

Less sensitive to decalibration. the isolated SG is maintained 45-80% NR using backflow, draining to the condenser or steaming to the condenser(depends on appropriate plant conditions).

20
Q

Under the conditions of a LOOP and SGTR with a stuck open ADV, state the TCA associated with covering the affected SG tubes.

A

The affected SG tubes must be covered within 46 minutes of SGTR. Less iodine scrubbing woudl occur, resulting in an increased radiological release to the environment.

21
Q

During a SGTR, when is it permissible to throttle HPSI?

A

HPSI may be throttled under the following conditions:

At least one HPSI pump operating

RCS is > 24F[44F] subcooled

Lpzr is > 10%[15%].

Intact and operable SG is 45-60%NR[45-60%NR] or being fed to this level.

RVLMS is showing RVUH > 16%.

HPSI not being used for success path in FRP.

22
Q

How is contaminated water management strategy implemented and who performs the procedure, handoffs, etc.?

A

SGTR will direct performance of 40DP-9ZZ14 Contaminated Water Management. The strategy addresses:

minimizes generation of contaminated water

storage of water

and processing of water.

The affected unit SM directes another SRO to perform. This new SRO is responsible for determining the appropriate actions and transferring responsibility to the EC when the TSC is activated*****

23
Q

State the TCA associated with SGTR for aligning the RCS to SDC.

A

20.3 hrs following SGTR, ESD or SBLOCA.

24
Q

State SFSCs for Rx control as they pertain to SGTR

A
  1. Power lowering or <2x10^-4% and stable or lowering
  2. All FSCEAs are inserted OR > 40gpm boration OR SDM verified
25
Q

State the SFSCs for MVA as they pertain to SGTR

A
  1. At least 1 vital 4.16kv bus energized
  2. At least one of the following(must be on same train as above):
    1. PKA-M41, PKC-M43, and PNA-D25
    2. PKB-M42, PKD-M44, and PNB-D26
  3. No jeapordized safety functions require restoration of electrical power to avital AC or DC bus. Not met if recovery of equipment is dependant on restoration of power.
26
Q

State the RCS inventory control SFSCs as they pertain to SGTR

A

May be met by either:

  1. Condition 1
    1. Lpzr > 10%[15%]
    2. RCS 24F[44F] or more subcooled
    3. RVLMS > 16% in RVUH or more.
  2. Condition 2
    1. SI flow adequate per App2
    2. RVLMS indicates that the outlet plenum is 21% or more.
27
Q

State the RCS pressure control SFSCs as they pertain to SGTR

A
  1. Condition 1
    1. Ppzr within P/T limits
  2. Condition 2
    1. SI flow is adequate per App 2
28
Q

State Core heat removal SFSCs as they pertain to SGTR

A

Thot is < 650F.

Max quadrant CET temperature < 650F

29
Q

State the RCS heat removal SFSCs as they pertain to SGTR

A

Condition 1

The unisolated SG has 45-60%NR[45-60%NR] or FW is restoring the unisolated sg to the above.

AND
Tc is stable or lowering.

Condition 2:

SDC is in service.

30
Q

State the Cont Isolation SFSCs as they pertain to SGTR

A
  1. Condition 1
    • NO abnormal rise in containment sump levels.
    • Pcont < 2.5 psig
    • No valid containment area or radiation alarms or rise in activity
    • Isolated SG pressure is < 1135psia and stable or lowering.
31
Q

State the Cont Temperature and Press SFSCs as they pertain to sgtr

A
  • Tcont < 117F
    • < 125F if a LOOP also occurred.
  • Pcont < 2.5psig

LOIT 2020 SIM phase COPY (25 decks)

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