ML20236Y575

Forwards RAI Re GL 96-06, Assurance of Equipment Operability & Containment Integrity During Design-Basis Accident Condition. Target Date for Response Agreed for 981101

ML20236Y575
Person / Time
Site:	Vogtle
Issue date:	08/10/1998
From:	Jaffe D NRC (Affiliation Not Assigned)
To:	Benjamin Beasley SOUTHERN NUCLEAR OPERATING CO.
References
GL-96-06, GL-96-6, TAC-M96881, TAC-M96882, NUDOCS 9808120311
Download: ML20236Y575 (6)

Text

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Mr. B. Be:sley August 10, 1998

. Vice Pr:sident South rn Nuclar Oper; ting Company, Inc.

Post Office Box 1295 Birmingham, Alabama 35201-1295

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION CONCERNING GENERIC LETTER (GL) 96-06, " ASSURANCE OF EQUIPMENT OPERABILITY AND CONTAINMENT INTEGRITY DURING DESIGN-BASIS ACCIDENT CONDITIONS"- VOGTLE ELECTRIC GENERATING PLANT (VEGP), UNITS 1 AND 2 (TAC NCS. MG6881 AND M96882)

Dear Mr. Beasley:

In the course of reviewing your January 27,1997, response to GL 96-06 for VEGP, the staff has identified the need for additional information. The enclosed request for additional information has been discussed with Jim Bailey of your staff. A target date for your response has been agreed upon to be November 1,1998. Should a situation occur which prevents you from meeting the due date, please contact me at (301) 415-1439.

Sincerely, ORIGINAL SIGNED BY:

David H. Jaffe, Senior Projeci h anaer Project Directorate 11-2 Division of Reactor Projects - 1/11 Office of Nuclear Reactor Regulation Docket Nos. 50-424 emiS0-425

Enclosure:

Request for Additional Information cc w/ encl: See next page '

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NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 'annan nani

% . . . . . p' August 10, 1998 Mr. B. Beasley Vice President i

Southern Nuclear Operating l

Company, Inc.

Post Office Box 1295 Birmingham, Alabama 35201-1295

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION CONCERNING GENERIC LETTER (GL) 96-06, " ASSURANCE OF EQUIPMENT OPERABILITY AND CONTAINMENT INTEGRITY DilRING DESIGN-BASIS ACCIDENT CONDITIONS' - VOGTLE ELEC.TRIC GENERATING PLANT (VEGP), UNITS 1 AND 2 (TAC NOS. M96881 ANC, M96882)

Dear Mr. Beasley:

In the course of reviewing your January 27,1997, response to GL 96-06 for VEGP, the staff has identified the need for additionalinformation. The enclosed request for additional information has been discussed with Jim Bailey of your staff. A target date for your response has been agreed upon to be November 1,1998. Should a situation occur which prevents you

' from meeting the due date, please contact me at (301) 415-1439.

Sincerely,

\

David H. , Senior Project Manager Project Directorate ll-2 Division of Reactor Projects - l/II Office of Nuclear Reactor Regulation Docket Nos. 50-424 and 50-425

Enclosure:

Request for Additional Information cc w/ encl: See next page u_______.___--- - - - - -

7 l

Vogtle Electric Generating Plant I cc: Harold Reheis, Director Mr. J. A. Bailey Department of Natural Resources

, Manager, Licensing _

205 Butler Street, SE. Suite 1252

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i Southem Nuclear Operating Atlanta, Georgic 30334 Company, Inc.

P. O. Box 1295 Attomey General Birmingham, Alabama 35201-1295 Law Department l

- 132 Judicial Building l Mr. J. Gasser Atlanta, Georgia 30334 l General Manager, Vogtle Electric Generating Plant Mr. R. D. Barker i Southern Nuclear Operating Program Manager Company, Inc. Fossil & Nuclear Operations P. O. Box 1600 Oglethorpe Power Corporation

- Waynesboro, Georgia 30830 2100 East Exchange Place  ;

P. O. Box 1349 Regional Administrator, Region ll Tucker, Georgia 30085-1349 U. S. Nuclear Regulatory Commission Charles A. Patrizia, Esquire

. Atlanta Federal Center Paul, Hastings, Janofsky & Walker l j 61 Forsyth Street, SW., Suite 23T85 10th Floor

Atlanta, Georgia 30303 1299 Pennsylvania Avenue Washington, DC 20004-9500 Office of Planning and Budget Room 615B Arthur H. Domby, Esquire 270 Washington Street, SW. Troutman Sanders l Atlanta, Georgia 30334 NationsBank Plaza l 600 Peachtree Street, NE.

Mr. J. D. Woodard Suite 5200 i Executive Vice President Atlanta, Georgia 30308-2216

! Southern Nuclear Operating Company, Inc. Resident inspector

- P. O. Box 1295 Vogtle Plant

! Birmingham, Alabama 35201-1295 8805 River Road i Waynesboro, Georgia 30830 -

Steven M. Jackson Senior Engineer - Power Supply Office of the County Commissioner Municipal Electric Authority Burke County Commission l

of Georgia Waynesboro, Georgia 30830 1470 Riveredge Parkway, NW.

Atlanta, Georgia 30328-4684

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REQUEST FOR ADDITIONAL INFORMATION FOR RESOLUTION OF 4 GENERIC LETTER 96-06 ISSUES AT VOGTLE 1 AND 2 (TAC NOS. M96881 AND M96882)

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. Georgia Power Company (the licer,see) provided its assessment of the waterhammer and two-phase flow issues for Vogtle 1 and 2 in a letter dated January 27,1997. The licensee has concluded that existing flow orifices will prevent two-phase flow situations from occurring in the nuclear service cooling water (NSCW) system, which provides cooling water for the containment air coolers (CACs), the auxiliary containment air coolers, and the reactor cavity coolers. The licensee also concluded that the NSCW system is susceptible to waterhammer, and that pressure spikes could exceed system design pressure. However, the licensee determined that allowable piping stresses for the system would not be exceeded. In order to assess the licensee's resolution of these issues, the following additional information is requested:

Notes: a. Information that has been submitted previously may be referred to and supplemented as necessary to provide a complete response to the staff's questions.

b. To the extent that positive measures are implemented to eliminate the potential for waterhammer and two-phase flow conditions, question number 3 may not be applicable.

c. ~ The following questions are applicable to the system configuration 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. To the extent that the possibility for waterhammer and two-phase flow to occur is eliminated, describe the minimum margin to boiling that will exist.

2. If a methodology other than that discussed in NUREG/CR-5220, " Diagnosis of Condensation-induced 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).

1 Enclosure

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3. Identify any computer codes that were used in the waterhammer and two-phase flow analyses and describe the methods used to validate and benchmark 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, fl~v 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 justified.

5. Explain why voiding in the CACs is limited to the two top coils (i.e., is this an assumption or is it based on heat transfer considerations).

6. The January 27,1997, response indicated that additional analyses would be completed to determine if modifications or system operational changes would be required to reduce waterhammer stresses. Describe the additional analyses that were completed and conclusions that were reached.

7. Explain and justify all uses of " engineering judgement" that were credited in the

. waterhammer and two-phase flow analyses.

8. 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 requirements to acknowledge the importance of these parameters and operating restrictions. Also, describe and justify use of any nonsafety-related instrumentation and controls for maintaining these parameters.

9. Implementing measures to minimize or eliminate waterhammer and two-phase flow conditions may be a viable approach for addressing these issues. However, all scenarios must be considered to assure that the vulnerability to waterhammer and two-phase flow has been eliminated. Confirm that all scenarios have been considered, including those where the affected containment penetrations are not isolated (if this is a possibility), such that the measures that have been established (or will be established) are adequate to address the waterhammer and two-phase flow concems during (and following) all applicable accident scenarios.

l 10. 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 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.

11. Describe the uncertainties that exist in the waterhammer and two-phase flow analyses, including uncertainties and shortcomings associated with the use of any computer codes,

l l

l l end explain how these uncertainties were accounted for in the analyses to assure

conservative results, i

12. The waterhammer and two-phase flow analyses assume that there is no back flow through i the containment supply check valves. Describe measures that exist that assure that these j valves will remain leak-tight over the life of the plant. 1 l

13. The response seems to indicate that two-phase flow due to fluid conditions in concert with the pressure drop associated with various system components was not considered.

Confirm that the potential for two-phase flow throughout the affected system was l evaluated and that two-phase flow conditions do not exist for any of the applicable accident scenarios. If it is determined that two-phase flow does exist, then heat transfer, structural, and system integrity concems must be addressed. For example, the following i two-phase flow effects would be relevant:

a the effects of void fraction on flow balance and heat transfer; the consequences of steam formation, transport, and accumulation; 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 analyses.

14. The waterhammer analysis was based on analyses of the NSCW system associated with l Unit 1, Train A. Confirm that the analyses that were completed are bounding for the other NSCW trains for both of the Vogtle units.

15. 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.

l 16. Descrite in detail any plant modifications or procedure changes that have been made or f j are planned to be made to resolve the waterhammer and two-phase flow issues, including j schedules for completion. j 1

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