ML20217K520

Forwards Request for Addl Info Re Responses to GL 96-06, Assurance of Equipment Operability & Containment Integrity During DBA Conditions Re Waterhammer & two-phase Flow Issues

ML20217K520
Person / Time
Site:	Grand Gulf
Issue date:	04/27/1998
From:	Donohew J NRC (Affiliation Not Assigned)
To:	Hagan J ENTERGY OPERATIONS, INC.
References
GL-96-06, GL-96-6, TAC-M96815, NUDOCS 9805010237
Download: ML20217K520 (7)

Text

( p** tog p k UNITED STATES Lj g j NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 200eHoo1 g

+.,*****/ April 27, 1998 )

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Mr. Joseph J. Hagan Vice President, Operations GGNS Entergy Operations, Inc.

P. O. Box 756 l Port Gibson, MS 39150 - i 1

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION RELATED TO GL 96-06 FOR GRAND GULF NUCLEAR STATION, UNIT 1 (TAC NO. M96815)

Dear Mr. Hagan:

This letter addresses your responses to Generic Letter (GL) 96-06, " Assurance of Equipment Operability and Containment integrity During Design-Basis Accident Conditions," which was issued by the staff on September 30,1996. The GL requested that the evaluate cooling water systems that serve containment air coolers at GGNS be evaluated to ensure that these systems I are not vulnerable to waterhammer and two phase flow conditions during postulated accident accidents.

You submitted the assessment for Grand Gulf Nuclear Station, Unit 1 (GGNS) in your letter of January 28,1997 (GNRO-97/00011). In that letter, you provided the results of an engineering evaluation of (1) containment air cooler systems for susceptibility to waterhammer and two-phase flow and (2) containment /drywell penetrations for susceptibility to over pressurization due to thermal expansion of fluid. The conclusion of the evaluation of containment air cooler systems was that the scenarios described in the GL are not a concem for GGNS because no credit is taken for coolers during accident mitigations and that postulated water system operation during ,

accident mitigation would not compromise the safety-related containment /drywell isolation I function. The conclusion of the evaluation of containment /drywell penetrations was that the j penetration integrity is expected to be maintained during the scenarios described in the GL. I On September 15,1997, we sent you a request for additional information (RAI) based on 'the # I review of your letters of October 29,1996 (GNRO 96/00122), and Janua:y 28,1997. In the letter of October 29,1996, you initially responded to the GL and stated that the results of evaluations on the containment air cooler cooling water systems and piping systems that penetrate containment, as requestad in the GL, would be submitted on or before January 28,1997. The results of these evaluations were submitted in your letter of January 28,1997. The RAI concemed the 12 pipes penetrating containment and the six pipes penetrating the drywell that ,

were identified as susceptible to thermal-induced pressurization in the letter of January 28,1997. l You responded to the RAI in your letter of November 20,1997 (GNRO-97/00114).  !

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' Joseph J. Hagan - To date, your responses to the GL have been the three letters of October 29,1996, January 28 and November 20,1997.

In order to complete our review of your responses to the GL and the resolution of the waterhammer

'and two-phase flow issues for GGNS, we request that you provide the additional information listed in the enclosure to this letter concoming water hammer and two-phase flow issues in the GL. You are requested to provide this information by June 30,1998, in order to support our schedule for the resolution of the GL.

Sincerely, O

6% W ick N. Donohew, Senior Project Manager roject Directorate IV-1 vision of Reactor Projects lil/IV Office of Nuclear Reactor Regulation Docket No. 50-416

'nclosure: Request for AdditionalInformation cc w/ enclosure: See next page l

DISTRIBUTION:

Docket File . PUBLIC PD4-1 r/f i E. Adensam (EGA1) J. Donohew T. Gwynn, RIV l ACRS OGC (15B18) C.Hawes J.Hannon L.B. Marsh J. Tatum  ;

l Document Name: GG96815.RAI (Memo dated April 1,1998)

OFC PW: LA/PD4-1 PD/PCiV 1[  !

NAME J hv/vw CHawesdlllN JHanh q DATE Y/ /98 h'Q7/96 TOl/98 COPY YES/NO YES/NO YES/NO OFFICIAL RECORD COPY

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l Joseph J. Hagan To date, your responses to the GL have been the three letters of October 29,1996, January 28 and November 20,1997.

In order to complete our review of your responses to the GL and the resolution of the waterhammer and two-phase flow issues for GGNS, we request that you provide the additional information listed in the enclosure to this letter conceming water hammer and two-phase flow issues in the GL. You are requested to provide this information by June 30,1998, in order to support our schedule for the resolution of the GL. <

Sincerely, I f Tktuh, l '

i u Jack N. Donohew, Senior Project Manager Project Directorate IV-1 j Division of Reactor Projects Ill/IV Office of Nuclear Reactor Regulation 1

Docket No. 50-416

Enclosure:

Request for AdditionalInformation cc w/ encl: See next page I J

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Mr. Joseph J. Hagan Entergy Operations, Inc. Grand Gulf Nuclear Station cc:

Executive Vice President General Manager, GGNS

& Chief Operating Officer Entergy Operations, Inc.

Entergy Operations, Inc. P. O. Box 756 P. O. Bcx 31995 Port Gibson, MS 39150 Jackson, MS 39286-1995 4 Attomey General Wise, Carter, Child & Caraway Department of Justice P. O. Box 651 State of Louisiana Jackson, MS 39205 P. O. Box 94005 Baton Rouge, LA 70804-9005 Winston & Strawn 1400 L Street, N.W. - 12th Floor State Health Officer Washington, DC 20005-3502 State Board of Health P. O. Box 1700 Director Jackson, MS 39205 Division of Solid Waste Management Mississippi Department of Natural Office of the Govemor Resources State of Mississippi P. O. Box 10385 Jackson, MS 39201 Jackson, MS 39209 Attomey General President, Asst. Attomey General Claibome County Board of Supervisors State of Mississippi P. O. Box 339 P. O. Box 22947 Port Gibson, MS 39150 Jackson, MS 39225 Regional Administrator, Region IV Vice President, Operations Support U.S. Nuclear Regulatory Commission Entergy Operations, Inc.

611 Ryan Plaza Drive, Suite 1000 P.O. Box 31995 Arlington, TX 76011 Jackson, MS 39286-1995 Senior Resident inspector Director, Nuclear Safety U. S. Nuclear Regulatory Commission and Regulatory Affairs Route 2, Box 399 Entergy Operations, Inc. '

Port Gibson, MS 39150 P.O. Box 756 Port Gibson, MS 39150

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REQUEST FOR ADDITIONAL INFORMATION FOR RESOLUTION OF GL 96-06 ISSUES AT THE GRAND GULF NUCLEAR PLANT ENTERGY OPERATIONS. INC. l DOCKET NO 5H16 TAC NO M96815 1

Generic Letter (GL) 96-06, " Assurance of Equipment Operability and Containment integrity During Design-Basis Accident Condit.ons," 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. Entergy Operations, '

incorporated (the licensee) provided its assessment for the Grand Gulf Nuclear Station, Unit 1 in the letter dated January 28,1997. The licensee's response dated November 20,1997, concemed questions from the staff on pipe lines penetrating the containment and drywell that were susceptible to thermally-induced pressurization.

The licensee's response of January 28,1997, indicated that the containment coolers and drywell coolers are not safety related, except for their cooling water penetrations and the associated isolation valves for the containment isolation function.

In the case of the containment coolers, the licensee's response stated that the containment temperature should not exceed 185' F, and no procedural guidance exists directing use of the containment coolers during the potential waterhammer and two-phase flow scenarios described in the GL. On this basis, the licensee concluded that waterhammer and two-phase flow concems are not applicable to the containment coolers.

In the case of the drywell coolers, the licensee's response indicated that the Emergency Operating Procedures do allow their use during waterhammer and two-phase flow scenarios.

The licensee evaluated the containment isolation function of the chilled water system (provides cooling for the drywell coolers) and concluded that, should a waterhammer occur that compromises the integrity of the chilled water system, the condition would be annunciated in the control room and operators would take action in accordance with existing procedures to close the drywell isolation valves for the chilled water system.

The licensee did not expect that a waterhammer event would compromise the containment /drywell isolation function of the chilled water system.

ENCLOSURE l

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2 Based on the licensee's responses in its January 28,1997, letter, the staff concludes that the licensee has not fully addressed the concems on potential waterhammer and two-phase flow in the GL, and requests the following additional information:

1. Although existing procedures do not specify use of the containment coolers for accident mitigation, operators may decide to use these coolers as an option for accident mitigation purposes. Desenbe measures that exist or that will be taken to assure that cooling water for i the containment coolers will remain isolated following a plant accident. l The following questions on the water hammer and two-phase flow analyses r e applicable to accident scenarios where the penetrations are not isolated for the containmen 'drywell cooling function:  ;

2. If a methodology other than that discussed in NUREGICR-5220 " Diagnosis of Condensation-Induced Waterhammer," was used in evaluating the effects of waterhammer, describe this )

attemate methodology in detail. Also, explain why this methodology is applicable and gives ]

conservative results for the Grand Gulf plant (typically accomplished through rigorous plant-  !

specific modeling, testing, and analysis).

3. For both the waterhammer and two-phase flow analyses, provids the following information:

a. 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 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, cushioning, speed of sound, force reductions, and mesh sizes, 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., fluid structure interaction, flow induced vibration, erosion). '

c. 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 j 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; j

• cavitation, resonance, and fatigue effects; and

• erosion considerations.

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

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d. Confirm that 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. Discuss and justify all uses of " engineering judgement."

4. Determine 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 Grand Gulf plant. l

5. Confirm that the waterhammer and two-phase flow loading conditions do not exceed any i design specifications or recommended service conditions (including those stated by equipment vendors) for the containment /drywell isolation valves that could be affected; and confirm that the containment /drywell isolation function will not be compromised.

6. The January 28,1997, letter response indicated that if the chilled water system should fait during a waterhammer event, the loss of chilled water inventory would cause the chilled water pumps to trip and annunciate in the control room. Discuss the reliability of the annunciation that is being referred to and assurances that exist that this annunciation will occur as expected (power supplies, quality classification, redundancy, periodic calibration and testing, failure modes, etc.). Also, discuss what effects the chilled water inventory i will have on the accident analysis and drywell performance as previously analyzed.  ;

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

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