ML20249A611

Forwards Request for Addl Info Re Util 970128 Response to GL 96-06, Assurance of Equipment Operability & Containment Integrity During Design-Basis Accident Conditions

ML20249A611
Person / Time
Site:	Monticello
Issue date:	06/08/1998
From:	Kim T NRC (Affiliation Not Assigned)
To:	Richard Anderson NORTHERN STATES POWER CO.
References
GL-96-06, GL-96-6, TAC-M96835, NUDOCS 9806170142
Download: ML20249A611 (4)

Text

y.

Mr. Roger'O. Anderson, Dir ctor ( tJune 8, 1998-NucleIr Energy Engineering

• Northern Stit:s Pow:r Comp:ny..

414 Nicollet Mall -

Minneapolis, MN 55401

SUBJECT:

- MONTICELLO NUCLEAR GENERATING PLANT - REQUEST FOR ADDITIONAL INFORMATION RELATED TO NORTHERN STATES POWER COMPANY'S RESPONSE TO GENERIC LETTER 96-06 (TAC NO. M96835)

Dear Mr. Anderson:

- By letter dated January 28,1997, Northern States Power Company (NSP) submitted its -

response to NRC Generic Letter (GL) 96-06, " Assurance of Equipment Operability and Containment I:Aegrity During Design-Basis Accident Conditions," dated September 30,1996..

--GL 96-06 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. In order to complete our review of NSP's response to the generic letter, the staff requests that you provide a response to the enclosed request for additional information. To

- support the staff's review schedule for GL 96-06, we request that you provide this information within 60 days of the date of this letter. If you have any questions regarding this request, please contact me at (301) 415-1392.

Sincerely, ORIGINAL SIGNED BY //  ;

Tae' Kim, Senior Project Manager Project Directorate lil-1 1B06170142 98060s Division of Reactor Projects - lil/IV gNt ADOCK O 3 Office of Nuclear Reactor Regulation -

1 Docket No: 50-263-

Enclosure:

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Mr. Roger O. Anderson, Director Monticello Nuclear Generating Plant Northern States Power Company ,

cc: -

J. E. Silberg, Esquire Kris Sanda, Commissioner Shaw, Pittman, Potts and Trowbridge Department of Public Service 2300 N Street, N. W. 121 Seventh Place East Washlagton DC 20037 Suite 200 St. Paul, Minnesota 55101-2145 U.S. Nuclear Regulatory Commission Resident inspector's Office Adonis A. Nr:Jolett 2807 W. County Road 75 Assistant Adorney General Monticello, Minnesota 35362 Office of the Attorney General 445 Minriesota Street Plant Manager Suite 900 Monticello Nuclear Generating Plant St. Paul, Minnesota 55101-2127 ATTN: Site Licensing Northern States Power Company 2807 West County Road 75 Monticello, Minnesota 55362-9637 i

Robert Nelson, President Minnesota Environmental Control Citizens Association (MECCA) 1051 South McKnight Road St. Paul, Minnesota 55119

. I Commissioner j Minnesota Pollution Control Agency 520 Lafayette Road St. Paul, Minnesota 55119 Regional Administrator, Region til  ;

U.S. Nuclear Regulatory Commission 801 Warrenville Road Lisle, Illinois 60532-4351 Commissioner of Health -

Minnesota Department of Health 717 Delaware Street, S. E.

Minneapolis, Minnesota 55440 Darla Groshens, Auditor / Treasurer Wright County Government Center 10 NW Second Street Bufblo, Minnesota 55313 January 1995 l

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1 REQUEST FOR ADDITIONAL INFORMATION RELATED TO NORTHERN STATES POWER COMPANY'S I RESPONSE TO GENERIC LETTER 96-06  !

Generic Letter (GL) 96-03, " Assurance of Equipment Operability and Containment Integrity During Design-Basis Accident Conditions," dated September 30,1996, included a request for

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i licensees to evaluate cooling water systems that serve containment air coolers to essure that  !

they are not vulnerable to waterhammer and two-phase flow conditions. Northem States Power Company (the licensee) provided its assessment of the waterhammer and two-phase flow 4

issues for Monticello in a letter dated January 28,1997. The licensee concluded that the

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Reactor Building Closed Cooling Water (RBCCW) System may be susceptible to waterhammer {

during a design-basis loss-of-coolant accident (LOCA) coincident with a loss of power, but l determined that the controlled restoration of RBCCW flow would result in a very minor I waterhammer and would not challenge the integrity of the piping system or that of the containment penetrations. The licensee alco concluded that in the unlikely event that two-phase flow did occur, no safcty-related functions would be affected. Because there is a possibility that waterhammer and two-phase flow can occur in the RBCCW system, the following additional information is requested:

1. If a methodology other than that dit. cussed in NUREG/CR-5220, " Diagnosis of Condensation-Indxed Waterhammer," was used in evaluating the effects of waterhammer, describe this alternate methodology in detail. Also, explain why this methodology is applicable and gives conservative results (typically accomplished through rigorous plant-specific modeling, testing, and analysis).

2. For both the waterhammer and two-phase flow analyses, provide the following information:

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a. Identify any computer codes that were used in the waterhammer and two-phase J fiow analyses and describe the methods used to bench mark the codes for the specific loading conditions involved (see Standard Review Plan' Section 3.9.1).

b. Describe and justify all assumptions and input parameters (including those used in any computer codes) such as amplifications due to fluid / structure interaction, cusoioning, speed of sound, force reductions, and mesh sizes, and explain why the values selected give consemative results. Also, provide justification for omitting any effects that may be relevant to the analysis (e.g., fluid / structure interaction, flow-induced vibration, erosion).

'NUREG-0800, ' Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants, LWR Edition," July 1981 l l ENCLOSURE l

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c. Provide a detailed descr;, . . _. .. e " 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. Additional examples include:

= the consequences of steam formation, transport, and accumulation; e cavitation, resonance, and fatigue effects; and

. erosion considerations.

Licensees may find NUREG/CR-6031, " Cavitation Guide for Control Valves,"

helpfulin addressing some espects of the two-ohase flow analyses. (Note: it is important for licensees to realize that in additien to heat transfer considerations, two-phase flow also involves structural and system integrity concems that must be addressed.)

'd. Confirm tha't the 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.

e. Explain and justify all uses of " engineering judgement."

3. Determine the uncertaint) in the waterhammer and two-phase flow analyses, explain how the uncertainty was determined, and how it was accounted for in the analyses to assure conservative results

4. Confirm that the waterhammer and 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.

5. Provide a simplified diagram of the system, showing major components, active  !

components, relative elevations, lengths of piping runs, and the location of any orifices -

and flow restrictions.

6. 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.

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