ML20236S234

Forwards RAI Re Licensee 970129 Response to GL 96-06, Assurance of Equipment Operability & Containment Integrity During Design Basis Accident Condition. Response Requested by 980930

ML20236S234
Person / Time
Site:	Wolf Creek
Issue date:	07/21/1998
From:	Thomas K NRC (Affiliation Not Assigned)
To:	Maynard O WOLF CREEK NUCLEAR OPERATING CORP.
References
GL-96-06, GL-96-6, TAC-M96887, NUDOCS 9807240215
Download: ML20236S234 (5)

Text

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1 July 21, 1998 Mr. Otto L'. Maynard

President and Chief Executive Officer Wolf Creek Nuclear Operating Corporation -

Post Office Box 411 -

' Burlington, Kansas 66839 -

)

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION RELATED TO GL 96 WOLF CREEK NUCLEAR OPERATING CORPORATION -

. WOLF CREEK NUCLEAR GENERATING STATION, UNIT 1 (TAC NO. M96887)

Dear Mr. Maynard:

The NRC staff has reviewed Wolf Creek Nuclear Operating Corporation's (WCNOC) u  ; January 29,1997, response to GL 96-06, " Assurance of Equipment Operability and - (

Containment integrity During Design Basis Accident Conditions," pertaining to the assessment of the waterhammer and two-phase flow issues for Wolf Creek Nuclear Generating Station, Unit 1.' As a result of the review, the staff has determined that additional information is needed to complete the' review. The information needed is detailed in the enclosure.

To assist the staff in meeting its review schedule, we request that you respond to this request for additional information by September 30,1998.

If you have any questions, please contact me at (301) 415-1362.

Sincerely, Original Signed By Kristine M. Thomas, Project Manager Project Directorate IV-2 L Division of Reactor Projects lil/lV.

Office of Nuclear Reactor Regulation Docket No. 50-482 , DISTRIBUTION- /

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Enclosure:

Request for Additional

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• Mr. Otto L. Maynard 2- July 21,1998 cc w/ encl:

- Jay Silberg, Esq. Chief Operating Officer Shaw, Pittman, Potts & Trowbridge Wolf Creek Nuclear Operating Corporation 2300 N Street, NW P. O. Box 411 Washington, D.C. 20037 Burlington, Kansas 66839 Regional Administrator, Region IV Supervisor Licensing U.S. Nuclear Regulatory Commission Wolf Creek Nuclear Operating Corporation 611 Ryan Plaza Drive, Suite 1000 P.O. Box 411 Arlington, Texas 76011 Burlington, Kansas 66839 Senior Resident inspector U.S. Nuclear Regulatory Commission U.S. Nuclear Regulatory Commission Resident inspectors Office P. O. Box 311 8201 NRC Road

• Burlington, Kansas 66839 Steedman, Missouri 65077-1032 Chief Engineer Utilities Division Kansas Corporation Commission 1500 SW Arrowhead Road Topeka, Kansas 66604-4027 Office of the Govemor State of Kansas Topeka, Kansas 66612 Attomey General Judicial Center 301 S.W.10th 2nd Floor Topeka, Kansas 66612 County Clerk Coffey County Courthouse Burlington, Kansas 66839 Vick L. Cooper, Chief Radiation Control Program Kansas Department of Health and Environment Bureau of Air and Radiation Forbes Field Building 283 Topeka, Kansas 66620 1

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l REQUEST FOR ADDITIONAL INFORMATION

! WOLF CREEK NUCLEAR OPERATING CORPORATION WOLF CREEK NUCI FAR GENERATING STATION. UNIT NO.1 I DOCKET NO. 50-482 RESOLUTION OF GL 96-06 ISSUES Generic Letter (GL) 96-06, " Assurance of Equipment Operability and Containment integrity l During Design-Basis Accident Conditions," dated September 30,1996, included a request j for licensees to evaluate cooling water systems that serve containment air coolers to assure l that they are not vulnerable to waterhammer and two-phase flow conditions. The Wolf Creek l

Nuclear Operating Corporation (the licensee) provided its assessment of the waterhammer and two-phase flow issues for the Wolf Creek plant in a letter dated January 29,1997. The licensee

. has previously determined that waterhammer will occur in the essential service water system (ESWS) due to column separation and rejoining. This condition was evaluated and in order to address this issue, modifications were made to piping supports in the vicinity of the containment coolers and the containment coolers were stiffened in all directions. In response to the concems expressed in GL 96-06, the licensee performed additional analyses and concluded that the corrective actions that were taken previously were sufficient to address the GL 96-06 waterhammer concems. The licensee also concluded that two-phase flow would not occur in the ESWS. In order to assess the licensee's resolution of these issues, the following additional l i

information is requested: '

l l Notes: a. Information that has been submitted previously may be referred to l L and supplemented as necessary to provide a complete response .

to the staff's questions.  !

b. The following questions are applicable to the system configuration j and analyses that are credited for the final resolution of the  !

waterhammer and two-phase flow issues.

'1. Provide a detailed description of the " worst case" scenarios for waterhammer and two-phase flow, taking into consideration the complete range of event possibilities, system configurations, and parameters. For example, all waterhammer types and water slug scenarios should be considered, as well as temperatures, pressures, flow rates, load

. combinations, and potential component failures. With regard to the two-phase flow analysis, describe the minimum margin to boiling that will exist throughout the ESWS for the applicable accident scenarios. Confirm that all applicable scenarios have been considered such that the measures that have been taken are adequate to address the waterhammer and two-phase flow concems.

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2-Note: In addition to heat transfer effects, two-phase flow conditions involve structural and system integrity effects that need to be

! considered. The following effects, for example, must be ,

addressed for two-phase flow conditions: 1 i

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l the effects of void fraction on flow balance and heat .

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the consequences of steam formation, transport, and accumulation; I a cavitation, resonance, and fatigue effects; and erosion considerations.

Licensees may find NUREG/CR-6031," Cavitation Guide for Control Valves," helpful in addressing some aspects of the two-phase flow conditions.

2. If a methodology other than that discussed in NUREG/CR-5220,"Diagr ; is of Condensation-Induced Waterhammer," was used in evaluating the efias of waterhammer, describe this attemate methodology in detail. Also, explain why this methodology is applicable and gives conservative results (typically accomplished through rigorous plant-specific modeling, testing, and analysis).

3. Identify any computer codes that were used in the waterhammer and two-phase flow analyses and describe the methods used to validate and bench mark the codes for the specific application and loading conditions involved.

4. Describe and justify all assumptions and input parameters (including those used in any computer codes) that were used in the waterhammer and two-phase flow analyses, and ,

provide justification for omitting any effects that may be relevant to the analyses (e.g., '

fluid structure interaction, flow induced vibration, erosion). Confirm that these assumptions and input parameters are consistent with the existing design and licensing basis of the plant. Any exceptions should be explained and justifukj.

5. Explain and jestify all uses of " engineering judgement" that were credited in the waterhammer and two-phase flow analyses.

6. Discuss specific system operating parameters and other operating restrictions that must be maintained to assure that the waterhammer and two-phase flow analyses remain valid, and explain why it would not be appropriate to establish Technical Specification j requirements to acknowledge the importance of these parameters and operating restrictions. Also, describe and justify use of any non-safety related instrumentation and controls for maintaining these parameters.

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4 l l l 7. Confirm that the waterhammer and two-phase flow analyses included a complete failure l modes and effects analysis (FMEA) for all components (including electrical and I

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.

8. Describe the uncertainties that exist in the watertiammer and two-phase flow analyses, including uncertainties and shortcomings associated with the use of any computer codes, and explain how these uncertainties were accounted for in the analyses to assure conservative results.

l 9. Provide a simplified diagram of the affected system, showing major components, active l components, relative elevations, lengths of piping runs, and the location of any orifices and flow restrictions.

10. Describe in detail any plant modifications or procedure changes that have been made or are planned to be made to resolve the waterhammer and two-phase flow issues, including completion schedules.

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