ML20249B983

Forwards Request for Addl Info Re GL 96-06, Assurance of Equipment Operability & Containment Integrity During Design-Basis Accident Condition,

ML20249B983
Person / Time
Site:	Fort Calhoun
Issue date:	06/23/1998
From:	Wharton L NRC (Affiliation Not Assigned)
To:	Gambhir S OMAHA PUBLIC POWER DISTRICT
References
GL-96-06, GL-96-6, TAC-M96813, NUDOCS 9806250138
Download: ML20249B983 (4)

Text

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June ~23,11998 ,

t Mr. S.' K. Gambhir' -

- Division Manager - Engineering & Operati0ns Support Omaha Public Power District .

Fort Calhoun Station FC-2-4 Adm.1 Post Office Box 399

. Hwy. 75 - North of Fort Calhoun ' '

Fort Calhoun, Nebraska 68023-0399 .

s. .

SUBJECT:

FORT CALHOUN STATION, UNIT NO.1 - REQUEST FOR ADDITIONAL INFORMATION RELATED TO GL 96-06 RESPONSE (TAC NO. M96813)

~

Dear Mr. Gambhir:

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. Omaha Public

. Power District (OPPD) provided its assessment for the Fort Calhoun Station in a letter dated January 24,1997.

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In order to complete the staff's review of OPPD's resolution of the waterhammer and two-phase flow issues, we request the additional information described in the enclosure. In order to maintain the staff's review schedule, please provide your response within 30 days of receipt of

- this letter.-

Sincerely,

~ Original Signed By L. Raynard Wharton, Project Manager Project Directorate IV-2 '

Division of Reactor Projects - lil/IV Office of Nuclear Reactor Regulation Docket No. 50-285 - DISTRIBUTION-Docket OGC

Enclosure:

Request for AdditionalInformation PUBLIC ACRS PDIV-2 Reading TMarsh EAdensam (EGA1) JTatum WBateman RWharton EPeyton PGwynn, Region IV DOCUMENT NAME: FC96-06.RAI WJohnson, Region IV ,

j OFC~ PDIV-2/PM PDIV-2/LAL g NAME1 [RWharton - EP k ,

DATE N ES/98

'6 & 3/98 .I  !

OFFICIAL RECORD COPY-

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Mr. S. K. Gambhir - June 23, 1998

'i cc w/ encl: .

Winston & Strewn ATTN: Perry D. Robinson, Esq.

1400 L Street, N.W.

Washington, DC 20005-3502 Mr. Jack Jensen, Chairman Washington County Board

- of Supervisors Blair, Nebraska 68008 .

Mr. Wayne Walker, Resident inspector U.S. Nuclear Regulatory Commission Post Office Box 309 :

Fort Calhoun, Nebraska 68023 Regional Administrator, Region IV U.S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 1000 Arlington, Texas ~ 76011 Ms. Cheryl Rodgers, LLRW Program Manager Environmental Protection Section Nebraska Department of Health 301 Centennial Mall, South P.O. Box 95007 Lincoln, Nebraska 68509-5007.

Mr. James W. Chase, Manager Fort Calhoun Station Post Office Box 399 Fort Calhoun, Nebras',w 68023 Mr. James W. Tills Manager- Nuclear Licensing Omaha Public Power District Fort Calhoun Station FC-2-4 Adm.

Post Office Box 399 l

. Hwy. 75 - North of Fort Calhoun Fort Calhoun, Nebraska 68023-0399 ,

o OMAHA PUBLIC POWER DISTRICT FORT CALHOUN STATION. UNIT NO.1 DOCKET NO 50 285 REQUEST FOR ADDITIONAL INFORMATION RESOLUTION OF GL 96-06 ISSUES Generic Letter (GL) 96-06, " Assurance of Equipment Operability and Containment integrity j 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 i

that they are not vulnerable to waterhammer and two-phase flow conditions. Omaha Public Power District (the licensee) provided its assessment in'a letter dated January 24,1997. The licensee's response indicated that vaporization in the component cooling water (CCW) system would not occur if CCW surge tank nitrogen overpressure is at least 32 psig (assuming a water level of 41"). Because the CCW surge tank pressure was allowed to be less than 32 psig, the -

licensee has taken interim corrective actions to address this issue and options fer permanent corrective actions were being evaluated. In order to adequately assess the licensee's resolution of the waterhammer and two-phase flow issues, the following additionst information is requested:

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, parameters, and potential component failures. Describe measures that have been taken to eliminate waterhammer and two-phase flow vulnerabilities.

2. 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.

3. Identify any computer codes that were used in the waterhammer and two-phase flow analyses and describe the methods used to bench mark the codes for use at the Fort Calhoun Station.

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

5. Detonnine the uncertainty 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 for the Fort Calhoun Staten.

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6. Explain and justih all uses of "enginiwring judgement."

7. Provide a simplified diagram of the CCW system (including nitrogen pressurization l system), showing major components, active components, relative elevations, lengths of piping runs, and the location of any orifices and flow restrictions.

8. Provide a copy of the 10 CFR 50.59 evaluation that was completed for modifications that

! were made to the CCW system operating requirements to address the waterhammer and two-phase flow issues (e.g., surge tank pressure and level), and explain why specific l technical specification requirements are not warranted for this situation.

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