ML043230504
| ML043230504 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 09/23/2004 |
| From: | Warner M Florida Power & Light Energy Seabrook |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| IR-04-003 RGN-001 | |
| Download: ML043230504 (37) | |
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Agenda Introduction FPL Energy Seabrook Presentation
- Mark Warner, Site Vice President Raj Kundalkar, Vice President, Nuclear Engineering Paul Freeman, Engineering Manager - Seabrook Station Closing Remarks
- Mark Warner FPL Energy Seabrook Station 2
Introduction Purpose of the Conference Present FPLEs position on an apparent violation and its significance Raj Kundalkar and Paul Freeman wi discuss the details of our evaluation FPL Energy Seabrook Station I
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E ng i nee ri n g Overview NAESCO's 1997 evaluation was incorrect and NRC approval should have been obtained FPLE performed a detailed evaluation of:
- design history
- 1 OCFR50.59 history
- mitigative and corrective actions
- risk from a Turbine Building flood FPL Energy Seabrook Station 4
E ng i nee ri ng Overview FPLEs 2004 1 OCFR50.59 evaluation confirms that the design change resulted in a less than minimal change in frequency of an accident Determination Assessment concluded the CDF increase is less than E-O7/yr FPLEs Phase 3 Significance FPL Energy Seabrook Station 5
Engineering Oven ievl The 1997 1 OCFR50.59 Evaluation does not meet FPLE standards FPLE performed a root cause evaluation and extent-of-condition review,rObbs fp4 I$
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extensive corrective actions 1
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- no similar issues identified 6 0 \\
U FPLE now has the benefit of the FPL Corporate Engineering organization for consultation FPL Energy Seabrook Station 6
Chronology 198511 986 Scuppers included in original FSAR descriptions Physical plant, design drawings and design calculation-of-record for Turbine Building flood did not include scuppers Flood mitigation relied on operator action Turbine Building sump contained alarm to alert operators of flooding Scuppers and condenser pit alarms not installed during construction Condenser pit alarm deleted from FSAR in 1985 FSAR/as built plant discrepancy was not recognized I
during plant licensing 4B FPL Energy Seabrook Station 7
Chronology 1985/1986 (cont)
NRC SER discussed scuppers as mitigative 1997 Discrepancy between UFSAR and plant design feature identified by Seabrook personnel during circulating water pipe leak investigation
- Revised UFSAR to reflect as-built plant condition (w/o Design Change Issued scuppers)
FPL Energy Seabrook Station 8
Chronology 1997 (cont)
Added redundant switches in Condenser pit with Control Room alarms Developed alarm response procedures for new switches NRC Inspection Report 97-06 Discusses action taken to resolve the scupper issue Concluded consequences of issue were small Non-Cited Violation issued FPL Energy Seabrook Station 9
Chronology 2004
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Performed 1 OCFR50.59 Evaluation to the new rule criteria Conducted Root Cause Evaluation Implemented corrective actions and enhancements FPL Energy Seabrook Station 10
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Turbine Building North Rollup Door Seabrook Station Turbine Building Rollup Door 14 FPL Energy Seabrook Station
Turbine Building Elevation ELECTR I CAL EOU I PMENT EL 2 1 ' - 1 0 "
( TYP 1 1
RELAY RM,,FLOOR
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I r EL 2 1 ' - 6 Fa 0 CRNO EL 21'-0" FLOOR
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P I T
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-O"( WEST S I D E 1 T U R B I N E B U I L D I N G D I A G R A M C R O S S S E C T ION E A S T L O O K I N G WEST FPL Energy Seabrook Station 15
Postulated Sequence of Events 1 Initiation - Circumferential failure of expansion joint resulting in a 56,000 gpm leak Altran and General Rubber Analysis
- Circumferential tear is not a credible failure
- Operating Experience at Diablo Canyon - 2 by 6 tear after 25 years of service FPL Energy Seabrook Station I
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Postulated Sequence of Events
- 2. Water level rises in Condenser pit
- High level alarm activates 3 fl
- High-High level alarm activates q P -
- Turbine Building sump high-high level alarms activate 3 y rp" If operator action is taken in response to alarms, the following postulated sequence of events will not occur FPL Energy 17 Seabrook Station
Postulated Sequence of-Events I
- 3. If no operator action is taken in response to alarms, water enters Relay Room #I and at room elevation (4) causes loss of Switchgear Room and at room elevation I 9 offsite power (LOOP)
(4) causes the loss of vital bus E5 and A train ECCS equipment
- @75 gpm drain to storm drain
- door gap small FPL Energy Seabrook Station
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Postulated Sequence of Events - Timeline Without Operator Action 0
Event Begins 5.5 hr 29.4 min Loss Train 'A' LOOP Essential switchgear With Operator Action 4.8 rnin doors opened n
22.2 min doors must be opened if doors open c8 rnin 43.9 min 9.8 rnin CW pumps secured to secure CW pump U
Event Begins/CW Pumps secured to avoid LOOP and avoid LOOP +
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FPL Energy Seabrook Station 19
1997 1 OCFR50.59 Evaluation 1997 1 OCFR50.59 evaluation was incorrect 2004 root cause concluded:
- deletion of the scuppers description from the UFSAR was not recognized as a change to a design function
- NRCs reliance upon scuppers in acceptance review was not recognized
- Station Operation Review Committee did not identify existence of unreviewed safety question FPL Energy Seabrook Station 20
1997 1 OCFR50.59 Evaluation The 10CFR50.59 procedure did not have adequate guidance
- reconciliation of design basis and licensing basis differences
- interpretation of the licensing basis Design change seen as a true-up to have the UFSAR match the as-built plant and design drawings and calculations FPLEnergy Seabrook Station 21
Corrective Action Case study of the issue will be presented to all qualified 1 OCFR50.59 screeners, evaluators and
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SORC members
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UFSAR change procedure and 10CFR50.59 Reference Manual will be revised to reference,d' the issue as a lesson learned FPL Energy Seabrook Station 22
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Corrective Action Comprehensive training provided for personnel authorized to perform Applicability Det e rm i nat ions, Screen i ngs and Eva1 uat ions
- Lessons learned from the issue will be Additional Enhancements included in the 1 OCFR50.59 Initial Training Program
- Turbine Building flood Abnormal Operating Procedure developed FPL Energy Seabrook Station 24
Extent of Conpition Review d j Detailed review of 65 10CFR50.59 evaluations performed from 1996 - 2003
- performed by Seabrook staff, MPR Associates, FPL
- high level of confidence, based on sampling plan, that Corporate Engineering there are no similar issues Seabrook Station 25
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Risk Evaluation Key SDP Inputs Validating FPLE Risk Model and Conclusions Updated flooding frequencies Updated scenario timing
- Detailed Flood Spread Modeling More than 5.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> to affect Train A Switchgear Train B Switchgear unlikely to be affected Detailed Human Reliability Analysis
- Operations crew exercises
- Equipment operator field trials
- All Operators trained on new Turbine Building flood Abnormal Operating Procedure FPL Energy Seabrook Station 27
Risk Evaluation Scenario of concern =
- LOOP caused by Turbine Building flood due to rupture
- Assumes a 2 wide, circumferential failure of the Circulating Water Piping expansion joint FPL Energy Seabrook Station 28
Postulated Sequence of Events - Timeline Without Operator Action 0
Event Begins 5.5 hr 29.4 min Loss Train A LOOP Essential switchgear A
With 4.8 min n doors opened 9.8 rnin U
Event BeginiCW Pumps secured A
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A Operator Action 22.2 min doors must be opened CW pumps secured to avoid LOOP if doors open <8 min 43.9 min to secure CW pump and avoid LOOP i
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Flooding Frequency Original flooding frequency used data through 1988 Update uses data through 2003 Sources: NUREGKR 5750, LERs & INPO One additional very large flood
- Methodology meets requirements of R.G.
1.200 and ASME PRA Standardcapability Category I1
- PRA received WOG Peer Review Grade 3 in 1999 FPL Energy Seabrook Station 30
Flooding Frequency Update Results - I he flooding frequency is reduced
- Very large 04/yr (factor of 2.3 )
flood: from 2.25 E-03/yr to 9.61 E=
- Large flood:
(factor of 8) from 9.26 E=O3/yr to 1.22 E-O3/yr FPL Energy Seabrook Station 31
Simulator Validation of Operator Response e
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e Four crews tested on the Turbine Building flood scenario All personnel involved in scenario development signed confidentiality agreements Precautions taken to ensure crews were not aware of the scenario Two Scenarios - with and without Condenser pit alarms FPL Energy Seabrook Station 32
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Risk Conclusions Core Damage Frequency Increase SPAR Updated Flood Frequency 5.5E=O7/yr Updated Flood I HEP FPLE Updated Flood/HEP FPL Energy Seabrook Station 5.36E-08 ACW 5.4 E - 08/y r 34
Conclusions 0 1 An error was made in 1997 and NRC approval to change the Turbine Building design should have been requested
- 2. We performed a root-cause evaluation and extent-of-condition review and i m plem en ted corn p re hens ive corrective actions and enhancements FPL Energy Seabrook Station 35
Conclusions
- 3. We evaluated the design change under current 1 OCFR50.59 rule
- design change can be implemented without prior NRC approval
- 4. Pursuant to NRC Enforcement Policy provided in the Statements of Consideration for the current 1 OCFR50.59 rule, we request NRC exercise enforcement discretion in this case FPL Energy Seabrook Station 36
Conclusions
- 5. If enforcement discretion is not utilized, 1997 10CFR50.59 issue should not be considered for escalated enforcement because the risk is not significant FPL Energy Seabrook Station 37