ML20217Q631
| ML20217Q631 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 05/04/1998 |
| From: | Buckley B NRC (Affiliation Not Assigned) |
| To: | Geoffrey Edwards PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| References | |
| GL-96-06, GL-96-6, TAC-M96827, TAC-M96828, NUDOCS 9805080256 | |
| Download: ML20217Q631 (5) | |
Text
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7 May_4, 1998-Mr. Gstrett D. Edwards d-m s
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M- ' Director Licensing, MC 62A-1/
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- 1. Nuclear Group Headquarters U-Correspondence Control Desk.
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- P. O. Box No.195 '
-Wayne, PA.19087-0195 iL
SUBJECT:
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REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE GENERIC 5
' LETTER 96-06 RESPONSE FOR LIMERICK GENERATING STATION, UNITS 1 l~
- AND 2 (TAC NOS. M96827 AND M96828)
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Dear Mr. Edwards:
Generic Letter (GL) 96-06, " Assurance of Equipment Operability and Containment Integrity During Design-Basis Accident Conditions," dated September 30,1996, included a request for licensees to evaluate cooling water systems that serve containment air coolers to assum that they are not vulnerable to waterhammer and two-phase flow conditions.~ Philadelphia Electric Co,mpany provided its assessment of the waterhammer and two-phase flow issues for Limerick 1' & 2 in letters dated January 28, and February 10,1997. In order to continue our review of your resolution of these issues, we request that you provide additional information, as
' ". discussed in the enclosure, by July 30,1998, in order to support our review schedule for GL 96-
~ 06.
Sincerely, 4
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Bartholomew C. Buckley, Senior Project Manager Project Directorate 1-2
. Division of Reactor. Projects - t/11
~ Office of Nuclear Reactor Regulation
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l Docket Nos.: 50-352 r
and 353
Enclosure:
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May 4,1998 Mr. Garrett D. Edwards Director-Licensing, MC 62A-1 PECO Energy Company Nuclear Group Headquarters 4orrespondence Control Desk
- 18. O. Box No.195 Wcyne, PA 19087-0195
SUBJECT:
REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE GENERIC LETTER 96-06 RESPONSE FOR LIMERICK GENERATING STATION, UNITS 1 i
AND 2 (TAC NOS. M96827 AND M96828)
Dear Mr. Edwards:
Generic Letter (GL) 96-06, " Assurance of Equipment Operability and Containment integrity During Design-Basis Accident Conditions," dated September 30,1996, included a request for licensees to evaluate cooling water systems that serve containment air coolers to assure that they are not vulnerable to waterhammer and two-phase flow conditions. Philadelphia Electric Company provided its assessment of the waterhammer and two-phase flow issues for Limerick 1 & 2 in letters dated January 28, and February 10,1997. In order to continue our review of your resolution of these issues, we request that you provide additionalinformation, as discussed in the enclosure, by July 30,1998, in order to support our review schedule for GL 96-06.
Sincerely, op A
etuvid C
Bartholomew C. Buckley, Senior Proje Manager Project Directorate 1-2 Division of Reactor Projects -1/ll Office of Nuclear Reactor Regulation Docket Nos.: 50 352 and 50-353
Enclosure:
As stated cc w/ encl: See next page
Mr. Garrett D. Edwards Umerick Generating Station, Units 1 & 2 PECO Energy Company cc:
J. W. Durham, Sr., Esquire Chief-Division of Nuclear Safety Sr. V.P. & General Counsel PA Dept. of Environmental Resources PECO Energy Company P.O. Box 6469 2301 Market Street '
Harrisburg, PA 17105-6469 Philadelphia, PA 19101 Manager-Umerick Ucensing,62A 1 Director-Site Engineering PECO Energy Company Umerick Generating Station 965 Chestert> rook Boulevard P.O. Box A Wayne, PA 19087-5691 Sanatoga, PA 19464 Mr. James D. von Suskil, Vice President Umerick Generating Station Manager-Experience Assessment Post Office Box A Umerick Generating Station Sanatoga, PA 19464 P.O. Box A Sanaloga, PA 19464 Plant Manager Umerick Generating Station Ubrary P.O. Box A U.S. Nuclear Regulatory Commiss' en Sanatoga, PA 19464 Region i 475 Allendale Road Regional Administrator, Region l King of Prussia, PA 19406 U.S. Nuclear Regulatory Commission 475 Allendale Road Senior Manager-Operations King of Prussia, PA 19406 Umerick Generating Station P.O. Box A Senior Resident inspector Senatoga, PA 19464 U.S. Nuclear Regulatory Commission
.Umerick Generating Station Dr. Judith Johnsrud P.O. Box 596 National Energy Committee Pottstown, PA 19464 Sierra Club 433 Orlando Avenue Director-Site Support Services State College, PA 16803 Umerick Generating Station P.O. Box A Sanatoga, PA 19464 Chairman Board of Supervisors of Umorick Township 646 West Ridge Pike Unfield, PA 19468
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REQUEST FOR ADDITIONAL INFORMATION FOR RESOLUTION OF GL 96-06 ISSUES AT LIMERICK 1 & 2 (TAC NOS. M96827 AND M96828)
Generic Letter (GL) 96-06, " Assurance of Equipment Operability and Containment integrity Du,ing Design-Basis Accident Conditions," dated September 30,1996, included a request for licensees to evaluate cooling water systems that serve containment air coolers to assure that they are not vulnerable to waterhammer and two-phase flow conditions. PECO Energy Company (the licensee) provided its assessment of the waterhammer and two-phase flow issues for Limerick 1 & 2 in letters dated January 28, and February 10,1997. The licensee indicated that cooling water to the containment air coolers is provided by the non-safety related Drywell Chilled Water System (DCWS), a closed loop system. The licensee determined that the elevated head tank in the DCWS would prevent the formation of steam bubbles in the system such that waterhammer is not a possibility. Also, since the DCWS does not perform a safety-related heat removal function, two-phase flow is not a concem. In order to assess the licensee's resolution of these issues, the following additional information is requested:
1.
Discuss specific system parameter requirements that must be maintained to assure that waterhammer will not occur (e.g., head tank level, temperature, pressure), and state the minimum margin to boiling that exists, including consideration of measurement and, e slytical uncertainties. Describe and justify reliance on any non-safety related instrumentation and controls for assuring that waterhammer will not occur, and explain why it would not be appropriate to establish Technical Specification requirements for maintaining these parameters.
2.
The GL 96-06 response' indicated that for small break loss-of-coolant accidents, operators will reestablish DCWS using existing emergency operating procedures (EOPs) before containment temperatures reach a point where steam generation could occur.
Describe in detail the actions required by the EOPs for this situation, operator response and the timing involved, and the minimum margin to boiling that will exist, including' consideration of inherent uncertainties.
3.
In order to more fully address the two-phase flow concem, provide the following information:
a.
Provide a detailed description of the " worst case" scenario for two-phase flow, taking into consideration the complete range of event possibilities, system configurations, and parameters. For example, temperatures, pressures, flow rates, load combinations, and potential component failures should be considered.
Additional examples include:
the consequences of steam formation, transport, and accumulation; cavitation, resonance, and fatigue effects; and erosion considerations.
2-I.icensees may find NUREG/CR-6031, " Cavitation Guide for Control Valves,"
helpfulin addressing some aspects of the two-phase flow analyses. (Note: it is important for licensees to realize that in addition to heat transfer considerations, two-phase flow also involves structural and system integrity concems that must be addressed).'
b.
Identify any computer codes that were used in the two-phase flow analysis and describe the methods used to bench mark the codes for the specific loading conditions involved (see Standard Review Plan Section 3.9.1).
I c.
Describe and justify all assumptions and input parameters (including those used in i
any computer codes), and explain why the values selected give conservative -
results. Also, provide justification for omitting any effects that may be relevant to the analysis (e.g., flow induced vibration, erosion).
d.
Determine the uncertainty in the two-phase flow analysis, explain how the uncertainty was determined, and how it was accounted for in the analysis to ~
assure conservative results.
e.
Confirm that the two-phase flow loading conditions do not exceed any design specifications or recommended service conditions for the piping system and components, including those stated by equipment vendors; and confirm that the system will continue to perform its design basis functions as assumed in the
- safety analysis report for the facility, and that the containment isolation valves will remain operable.
4.
Confirm that the waterhammer and two-phase flow analyses included a complete failure modes and effects analysis (FMEA) for all components (including electrical and pneumatic failures) that could impact performance of the cooling water system and confirm that the FMEA is documented and available for review, or explain why a complete and fully documented FMEA was not performed.
5.
Explain and justify all uses of " engineering judgement."
l 6.
Provide a simplified diagram of the affected system, showing major components, active components, relative elevations, lengths of piping runs, and the location of any orifices and flow restrictions.
7.
Describe in detail any modifications that have been made (or will be made) to system design or operating requirements to resolve the waterhammer and two-phase flow issues.
Enclosure