ML15112A643
| ML15112A643 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 06/17/1998 |
| From: | Labarge D NRC (Affiliation Not Assigned) |
| To: | Mccollum W DUKE POWER CO. |
| References | |
| GL-96-06, GL-96-6, TAC-M96840, TAC-M96841, TAC-M96842, NUDOCS 9806180264 | |
| Download: ML15112A643 (5) | |
Text
J3une 17, 1998 Mr. W. R. McCollum Vice President, Oconee Site Duke Energy Corporation P. 0. Box 1439 Seneca, SC 29679
SUBJECT:
REQUEST FOR ADDITIONAL INFORMATION - RESPONSE TO GENERIC LETTER 96-06 FOR OCONEE NUCLEAR STATION, UNITS 1, 2, AND 3 (TAC NOS. M96840, M96841, AND M96842)
Dear Mr. McCollum:
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. Duke Energy Corporation (DEC) provided an assessment of the waterhammer and two-phase flow issues for Oconee Nuclear Station, Units 1, 2, and 3, in letters dated January 28, April 15, June 30, and August 1, 1997.
In order for the staff to complete its review of DEC's resolution of these issues, additional information is needed as discussed in the enclosure. Please provide this information by August 30, 1998, in order to support our review schedule for GL 96-06.
Sincerely, ORIGINAL SIGNED BY:
David E. LaBarge, Senior Project Manager Project Directorate 11-2 Division of Reactor Projects - 1/11 Office of Nuclear Reactor Regulation Docket Nos. 50-269, 50-270, and 50-287
Enclosure:
Request For Additional Information cc w/encl: See next page Distribution:
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1 AUNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 2055-001 June 17, 1998 Mr. W. R. McCollum Vice President, Oconee Site Duke Energy Corporation P. 0. Box 1439 Seneca, SC 29679
SUBJECT:
REQUEST FOR ADDITIONAL INFORMATION - RESPONSE TO GENERIC LETTER 96-06 FOR OCONEE NUCLEAR STATION, UNITS 1, 2, AND 3 (TAC NOS. M96840, M96841, AND M96842)
Dear Mr. McCollum:
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. Duke Energy Corporation (DEC) provided an assessment of the waterhammer and two-phase flow issues for Oconee Nuclear Station, Units 1, 2, and 3, in letters dated January 28, April 15, June 30, and August 1, 1997.
In order for the staff to complete its review of DEC's resolution of these issues, additional information is needed as discussed in the enclosure. Please provide this information by August 30, 1998, in order to support our review schedule for GL 96-06.
Sincerely, David E. LaBarge, Senior Project Manager Project Directorate 11-2 Division of Reactor Projects - III Office of Nuclear Reactor Regulation Docket Nos. 50-269, 50-270, and 50-287
Enclosure:
Request For Additional Information cc w/encl: See next page
Oconee Nuclear Station cc:
Mr. Paul R. Newton Mr. J. E. Burchfield Legal Department (PBO5E)
Compliance Manager Duke Energy Corporation Duke Energy Corporation 422 South Church. Street Oconee Nuclear Site Charlotte, North Carolina 28242 P. 0. Box 1439 Seneca, South Carolina 29679 J. Michael McGarry, III, Esquire Winston and Strawn Ms. Karen E. Long 1400 L Street, NW.
Assistant Attorney General Washington, DC 20005 North Carolina Department of Justice Mr. Robert B. Borsum P. 0. Box 629 Framatome Technologies Raleigh, North Carolina 27602 Suite 525 1700 Rockville Pike L. A. Keller Rockville, Maryland 20852-1631 Manager - Nuclear Regulatory Licensing Manager, LIS Duke Energy Corporation NUS Corporation 526 South Church Street 2650 McCormick Drive, 3rd Floor Charlotte, North Carolina 28242-0001 Clearwater, Florida 34619-1035 Mr. Richard M. Fry, Director Senior Resident Inspector Division of Radiation Protection U. S. Nuclear Regulatory North Carolina Department of Commission Environment, Health, and 7812B Rochester Highway Natural Resources Seneca, South Carolina 29672 3825 Barrett Drive Raleigh, North Carolina 27609-7721 Regional Administrator, Region II U. S. Nuclear Regulatory Commission Atlanta Federal Center 61 Forsyth Street, S.W., Suite 23T85 Atlanta, Georgia 30303 Max Batavia, Chief Bureau of Radiological Health South Carolina Department of Health and Environmental Control 2600 Bull Street Columbia, South Carolina 29201 County Supervisor of Oconee County Walhalla, South Carolina 29621
I REQUEST FOR ADDITIONAL INFORMATION RESOLUTION OF GENERIC LETTER 96-06 ISSUES OCONEE NUCLEAR STATION, UNITS 1. 2. AND 3 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 ensure that they are not vulnerable to waterhammer and two-phase flow conditions. Duke Energy Corporation (DEC) provided the assessment of the waterhammer and two-phase flow issues for Oconee Nuclear Station, Units 1, 2, and 3, in letters dated January 28, April 15, June 30, and August 1, 1997. DEC's submittals indicate that substantial work has been completed to assess waterhammer and two-phase flow conditions, including completion of two independent analyses, use of RELAP5 for system modeling, and performance of a failure modes and effects analysis. However, additional clarification is required in order to fully assess DEC's resolution of these issues, as described below:
Note: Where the requested information is contained in a previous submittal, please make reference to the submittal and supplement the information as necessary to provide a complete response.
- 1. For both the waterhammer and two-phase flow analyses, provide the following information:
- a. Identify any computer codes that were used in the waterhammer and two-phase flow analyses; describe the methods used to benchmark the codes for the specific application and 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 (e.g., explain why only horizontal nodes were considered, definition of "significant voiding," Froude number criteria of less than 0.5). Also, provide justification for omitting any effects that may be relevant to the analysis (e.g., fluid structure interaction, pipe-wall temperature effects, steam transport and accumulation, flow induced vibration, erosion). Confirm that worst-case conditions were identified and used in the waterhammer and two-phase flow analyses that were performed.
- c. Describe in detail the limitations and uncertainties associated with use of any computer codes (e.g., RELAP5, GOTHIC) in analyzing waterhammer and two-phase flow in low pressure cooling water systems, and explain how these limitations and uncertainties were accounted for in the analysis to assure conservative results.
- d. 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. Ad ditional examples include:
Enclosure
-2
- 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.
You may find NUREG/CR-6031, "Cavitation Guide for Control Valves," helpful in addressing some aspects of the two-phase flow analyses. (Note: It is important to realize that in addition to heat transfer considerations, two-phase flow also involves structural and system integrity concerns that must be addressed).
- e. Confirm that the analyses include 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.
- f., Explain and justify all uses of "engineering judgement."
- 2. 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 ensure conservative results.
- 3. 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.
- 4. Explain the differences that exist between the DEC analysis and the Altran analysis that were performed, and describe any corrective actions that may be needed to ensure conservative results.
- 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, and the schedule for completing these corrective actions.