ML051370177
| ML051370177 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom, Perry, Ginna, Quad Cities, LaSalle  |
| Issue date: | 05/12/2005 |
| From: | Constellation Energy Group |
| To: | Office of Nuclear Reactor Regulation |
| Thompson John W., NRR/DIPM/IIPB 415-1011 | |
| Shared Package | |
| ML051380314 | List: |
| References | |
| Download: ML051370177 (43) | |
Text
I Constellation Energy
I
- Ginna scram was the result of the grid instability on August 14, 2003.
- Voltage and frequency fluctuations caused the digital feedwater control system to switch to a failsafe manual mode.
- S/G levels increased to high level until the feedwater isolation occurred.
- Overfeed of the steam generators cooled the RCS temperaturesk well below no load temperatures.
9
- MSIV's were closed as directed in emergency procedures in response to the high S/G level.
- All steam dumps were closed and RCS temperature was below program when MSIV's were closed.
MSIV's could have been opened and steam dump to the condenser established once high S/G levels were cleared and the steam header evaluated for overfill.
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Constellation EnergyD I The way energy works.'m 2
i, Timeline for Ginna Scram Event 8/14/03 16:11:25 Turbine Runback 16:11:26 First Steam Dump Valve Opens 16:11:27 Pressurizer PORVs Open 16:11:29 Pressurizer PORV's Closed 16:11:33 All Steam Dump Valve Open 16:11:35 Reactor Scram on OTDT 16:11:36 Turbine Stop Valves Closed 16:11:48 First Steam Dump Valve Begins to Close 16:11:55 7/8 Steam Dump Valves Closed (V3349 Mid-Position) 16:12:09 Tavg Below No Load Tref (547 Deg. F) 16:12:36 Generator Output Breakers Open 16:13:05 All Steam Dump Valves Closed 16:13:09 A Feedwater Isolation (S/G A High Level) 16:13:14 B Feedwater Isolation (S/G B High Level) 16:31:02 A MSIV Closed 16:31:05 B MSIV Closed 16:32:27 Tavg Reaches No Load Tref 16:34:16 B ARV Opens 16:37:06 A ARV Opens constellation Energy I The way energy worksY'
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- Reactor coolant pumps tripped at 16:35 on 8/14/03 due to under frequency. The station remained at mode 3 with natural circulation cooling until the following day.
- None of the Main Steam Safety Valves opened during the event.
- Condenser steam dump system functioned as designed during the runback and immediately after the scram.
- Reactor decay heat at the time of MSIV closure was 2.4% which is well within the capability of the main steam atmospheric relief valves (1 0%).
Constellation Energy I The way energy works.TM 4
Constellation Energy(D I The way energy works.TM 4
111-3 Response: This event should not be counted as an unplanned scram with loss of normal heat removal.
NEI 99-03 states: "Operator actions or design features to control the reactor cooldown rate or water level, such as closing the main feedwater valves or closing all MSIVs, are not reported in this indicator as long as the normal heat removal path can be readily recovered from the control room without the need for diagnosis or repair.
In this case, a feedwater isolation signal had automatically closed the main feed regulation valves, effectively mitigating the high level condition. Manually closing the MSIVs was a conservative procedure driven action in response to steam generator water level.
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Constellation Energy I The way energy works.TM 5
Sa AI The main feed regulating valves were capable of being easily opened from the control room.
The MSIVs were capable of being opened from the control room after local actions to bypass and equalize pressure (see NEI 99-02 Appendix D, page 38).
No repairs were required for these systems to be used.
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3 NEI 99-02 also states:
"Examples that do not count: loss of all main feedwater flow, condenser vacuum, or turbine bypass capability caused by full or partial loss of offsite power;"
The Ginna Station scram event was caused by a massive grid disturbance which resulted in the feedwater isolation and the operators closing the MSIVs. FAQ 355 as incorporated in Rev. 3, supports the premise that a partial loss of offsite power which affected feedwater, condensate, and condenser systems should not be counted.
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Exekons.
Nuclear Peach Bottom Atomic Power Station NRC / Industry Frequently Asked Question Appeal Meeting NRC / Industry FAQ Meeting 5/12/05 - FAQ 36.2 1
ExekOn..
Nuclear Presentation of Rationale for FAQ 36.2 Jamie Mallon PBAPS Regulatory Assurance Manager NRC / Industry FAQ Meeting 5/12/05 - FAQ 36.2 2
Exekrn.m Nuclear Summary of Event (7/22/03) 1345 hour0.0156 days <br />0.374 hours <br />0.00222 weeks <br />5.117725e-4 months <br />s: Unit 2 Scram due to Generator Lockout
- Cause due to Foreign Material in Generator Isophase Buswork
- Expected Primary Containment Isolation (Group H/II/I) on Level 3 Reactor Water Level (Lo Level)
- Group III PCIS isolation includes Reactor Building Ventilation Isolation / Standby Gas System Start NRC / Industry FAQ Meeting 3
5/12/05 - FAQ 36.2
Exekn.m SM Nuclear Summary of Event (7/22/03)
- 1358 hour0.0157 days <br />0.377 hours <br />0.00225 weeks <br />5.16719e-4 months <br />s: PCIS Group I (MSIV Closure)
- Caused by high temp in vicinity of MSLs resulting from loss of Reactor Bldg. Ventilation due to Group II/III isolation
- 1413 hour0.0164 days <br />0.393 hours <br />0.00234 weeks <br />5.376465e-4 months <br />s: Group II / III isolations reset and ventilation restarted
- 1417 hour0.0164 days <br />0.394 hours <br />0.00234 weeks <br />5.391685e-4 months <br />s: Group I Isolation signal is reset due to ventilation restart
- 1525 hour0.0177 days <br />0.424 hours <br />0.00252 weeks <br />5.802625e-4 months <br />s: MSIVs re-opened
- Could have been re-opened earlier if desired NRC / Industry FAQ Meeting 4
5/12/05 - FAQ 36.2
Exekon.M Nuclear MSIV Closure Analysis
- Operators are aware of Group I isolation possibility when GP II/III isolation occurs
- Plant was not in an off-normal condition
- No steam leaks
- High ambient temperature on 7/22/03 resulted in high area temperature causing isolation
- Unit 2 specific design issue with location of temperature instruments Subsequent Tech Spec Amendment raised setpoints from 200OF to 2300F (Issued 6/16/04)
NRC / Industry FAQ Meeting 5
5/12/05 - FAQ 36.2
Exekon.M Nuclear NEI 99-02 Loss of Heat Removal Criteria
- Event does not count if normal heat removal path is
- Easily Recovered From the MCR
- Without the Need for Diagnosis or Repair NRC / Industry FAQ Meeting 5/12/05 - FAQ 36.2 6
Exek(n.M Nuclear Easily Recovered
- Group I / II / III Reset procedures Simple to Perform Operators have JPM
- Actions to Reset PCIS isolations and re-open MSIVs performed in MCR
- Local operation of 5 fan switches required for ventilation restart
- Fans are turned off during Group III Reset procedure to provide more control when restarting ventilation
- Normal post-scram operation NRC / Industry FAQ Meeting 7
5/12/05 - FAQ 36.2
Exe Onm Nuclear Without Diagnosis or Repair
- Plant Documents recognize potential for Group I when Group II / III occurs
- Procedures
- Tech Spec Bases
- Training (JPM)
- No Repairs Required
- Reactor Building ventilation promptly lowers MSL area temperature NRC / Industry FAQ Meeting 8
5/12/05 - FAQ 36.2
ExekOnSM Nuclear Conclusion
- This event should not be counted as a loss of normal heat removal (IE02)
- Not a Complicated Scram
- MSIV closure was not due to an off-normal event (hot summer day)
- Heat Sink Easily Recoverable NRC / Industry FAQ Meeting 5/12/05 - FAQ 36.2 9
ExekOn.
Nuclear LaS alle County Generating Station NRC / Industry Frequently Asked Question Appeal Meeting NRC / Industry FAQ Meeting 5/12/05 1
Exe krn.M Nuclear Presentation of Rationale for FAQ 27.3 David J. Distel Licensing and Regulatory Affairs NRC / Industry FAQ Meeting 5/12/05 2
ExekOn.
Nuclear Summary of Event
- Unit 2 - 100% power, steady state, both TDRFPs Running
- Both Reactor Recirc pumps downshifted to slow on an invalid Level 3 low level signal
- Resulting swell caused reactor level to reach Level 8 high level trip setpoint
- 2A and 2B TDRFPs tripped
- Turbine trip, reactor scram at 0909 hours0.0105 days <br />0.253 hours <br />0.0015 weeks <br />3.458745e-4 months <br /> on 4/6/01 NRC / Industry FAQ Meeting 3
5/12/05
ExekIn.
SM Nuclear Summary of Event
- Operators started MDRFP
- No flow path available for MDRFP, because FRV had failed shut due to blown fuse
- Operators chose to start RCIC to control level, rather than recover TDRFPs
- Finer level control
- Allowed per procedures and training NRC / Industry FAQ Meeting 4
5/12/05
Exeke~n.?
Nuclear Feedwater Availability 2A TDRFP recoverable:
- Tripped due to high reactor water level
- No other off-normal conditions preventing use
- Sufficient to provide flow to maintain level and normal heat removal
- Other two FW pumps were not available:
- 2B TDRFP Manual/Automatic Transfer Station de-energized due to blown fuse
- MDRFP FRV failed shut due to blown fuse NRC / Industry FAQ Meeting 5
5/12/05
ExekOnM Nuclear NEI 99-02 Loss of Heat Removal Criteria Event does not count if normal heat removal path is
- Easily Recovered from the MCR
- Without the Need for Diagnosis or Repair NRC / Industry FAQ Meeting 6
5/12/05
Exek0n.s Nuclear Conclusion Normal Heat Removal Was Available
- 2A TDRFP was fully recoverable from the control room using normal operating procedures without diagnosis or repair
- Operators chose to use RCIC for level control
- Permitted by Station procedures and training
- NEI 99-02 states that the determining factor is availability, not whether the operators choose to use another path.
5/12/05
Nuclear Quad Cities Nuclear Power Station NRC / Industry Frequently Asked Question Appeal Meeting NRC / Industry FAQ Meeting 5/12/05 I
Exektn.M Nuclear Presentation of Rationale for FAQ 36.1 David J. Distel Licensing and Regulatory Affairs NRC / Industry FAQ Meeting 5/12/05 2
Exekrn.m Nuclear Summary of Event Quad Cities Unit 2 - April 16, 2003
- 1322 - RPV Relief Valve Stuck Open
- Steps taken to close valve - not successful
- 1337 - Manual Scram
- Torus temperature at 95 degrees
- 1353 - Operators closed MSIVs per training
- Procedure directs taking actions to limit reactor cooldown rate to less than 100 degrees/hour NRC / Industry FAQ Meeting 3
5/12/05
Nuclear Summary of Event cont'd
- -41430 - Condenser vacuum below bypass valve permissive
- 2104 - Shutdown cooling initiated per procedure
- 2109 - RPV Relief Valve indicated closed
-Reactor pressure at r50 psig At no time during this event was condenser vacuum required NRC / Industry FAQ Meeting 4
5/12/05
Exek n.m Nuclear System Availability
- MSIVs were available to be opened at any time
- The Condenser was intact and available throughout the event
- For the first 30 minutes, condenser vacuum was sufficient to reopen the MSIVs without needing to recover vacuum
- For the duration of the event, condenser vacuum could have been recovered using the usual condenser startup procedures, and the MSIVs could have been opened.
NRC / Industry FAQ Meeting 5
5/12/05
Exek!)n.
Nuclear NEI 99-02 Loss of Heat Removal Criteria
- This indicator monitors that subset of unplanned automatic and manual scrams that were complicated by the loss of the normal heat removal path
- Actions to control cooldown rate, such as closing all MSIVs, are not reported as long as the path is readily recovered from the CR without diagnosis or repair NRC / Industry FAQ Meeting 6
5/12/05
Exe kn.m Nuclear NEI Criteria cont'd The event was not complicated by the closure of the MSIVs
- The closure of the MSIVs was performed solely to control cooldown in accordance with operator training and procedures.
- MSIV closure not required to mitigate any off-normal condition; this action was the appropriate choice by the operator to maintain critical plant parameters.
- There was no leak downstream of the MSIVs, or any other aspect of the event that made the normal heat removal path unavailable.
NRC / Industry FAQ Meeting 7
5/12/05
Exe knM Nuclear NEI Criteria cont'd The recovery of the condenser would not have involved repair or diagnosis With condenser vacuum, reopening MSIVs would take approximately 10-15 minutes Recovering condenser vacuum and reopening MSIVs would take approximately 45-50 minutes Although some operations outside the control room would be required, they are simple, trained, proceduralized actions involving no repair or diagnosis.
- Normal Heat Removal Path is recoverable.
NRC / Industry FAQ Meeting 8
5/12/05
Exekrn.
Nuclear Conclusion
- The MSIVs were closed only to control cooldown.
- Normal heat removal path was readily recoverable, at the discretion of the control room operator.
- Event is not a scram with loss of normal heat removal.
NRC / Industry FAQ Meeting 9
5/12/05
,