ML18153A390
| ML18153A390 | |
| Person / Time | |
|---|---|
| Site: | Surry, North Anna  |
| Issue date: | 10/23/1997 |
| From: | Ohanlon J VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 96-516B, GL-96-06, GL-96-6, NUDOCS 9710290073 | |
| Download: ML18153A390 (4) | |
Text
e VIRGINIA ELECTRIC AND PowER COMPANY RicuMOND, VIRGINIA 23261 October 23, 1997 United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, D. C. 20555 Serial No.
96-516B NL&OS/MWH R3 Docket No.
50-280, 281
, * * "50-338,
- 339
- Gentlemen:
VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS 1 AND 2 License No.
DPR-32, 37 NPF-4, 7 NORTH ANNA POWER STATION UNITS 1 AND 2 SUPPLEMENTAL RESPONSE TO GENERIC LETTER (GL) 96-06 In our letter dated January 28, 1997 (Serial No. 96-516A}, Virginia Electric and Power Company (Virginia Power) provided our 120 day response to Generic Letter 96-06, "Assurance of Equipment Operability and Containment Integrity During Design Basis Accident Cor:iditions." The response included an evaluation of the piping systems in each containment penetration configuration that could be susceptible to thermal expansion of fluid such that overpressurization could occur. The evaluation identified penetrations at Surry and North Anna that exceeded ASME Section Ill acceptance criteria (2Sm) but were capable of sustaining overpressurization conditions without ultimate failure.
We committed in our previous response to perform further analysis of the penetrations that exceeded the 2Sm criteria and to determine whether modifications were necessary.
As noted in the letter referenced above, the piping design codes for Surry (USAS B31.1-1967) and North Anna (ANSI B31.7 - 1969) do not provide specific criteria for evaluating isolated pipe segments under faulted conditions. However, we have conservatively re-evaluated the piping systems in each containment penetration configuration using the respective pipe code acceptance criteria from USAS B31.1 (1.2 Sm) and ANSI B31.7 (1.0 Sm for Class 1 and 1.2 Sm for Class 2) that address conditions that result from variations from normal operations. As a result of this conservative re-evaluation, we determined that even though certain penetrations exceeded their respective general code acceptance criteria, each penetration evaluated was capable of sustaining the single event overpressurization conditions without ultimate failure.
We have completed our initial plant specific analysis. It had been our intent to prepare design modification packages after we completed our determination of which penetrations exceeded acceptance criteria.
However, we have recently received information
~'\\'V i\\ '
e
, applicable to the resolution of this issue that may modify our course of action and potentially preclude the need for plant modifications. First, a recent ASME Code Case, "Rules for Evaluating Fluid Thermal Expansion Effects, Section Ill, Division 1, Class 2 and 3
11 has provided an acceptance criterion that is directly related to this one time faulted event.
The new ASME Code Case would afford the opportunity of evaluating the containment penetrations using an appropriate faulted code acceptance criterion.
Second, it is our understanding that a supplement to Generic Letter 96-06 may be forthcoming from the NRG. We do not want to commit to a course of action that may be inconsistent with the pending Code Case or information to be provided in the forthcoming supplement.* Finally, we are *current1y *assessirtg'the *need to mbdify-the curre'rit piping code design basis at North Anna and Surry to include ASME Section Ill, Appendix F, "Rules for Evaluation of Service Loading with Level D Limits," in order to address conditions such as postulated by GL 96-06.
Virginia Power's preferred approach would be to justify the adequacy of the existing design to accommodate the potential thermal expansion of fluid without failure, or, if necessary, to determine modifications for compliance which enhance overall safety.
Plant modifications to address this issue, such as the installation of relief valves in certain systems, may not increase plant safety and system reliability. Specifically, installation of relief valves tend to increase system complexity and the potential for system leakage. As a preferred option to hardware modifications, we believe it would be prudent to evaluate the penetrations that exceed our conservative code acceptance criteria using either the ASME Ill Code Case criteria or Appendix F criteria for this postulated one time faulted event. Using a more directly applicable acceptance criteria will likely minimize or possibly eliminate the need for plant modifications.
The two acceptance criteria options will be more fully evaluated pending generic resolution of the use of the Code Case and/or issuance of the supplement to Generic Letter 96-06.
Specific acceptance criteria will be selected for application to the penetrations for North Anna and Surry Power Stations by February 27, 1998.
The penetrations will then be evaluated using the selected acceptance criteria for this postulated one time faulted event and this response will be amended as applicable. In the interim, our evaluation has concluded that a loss of containment integrity will not occur due to the postulated one-time overpressurization of containment piping penetrations.
Please contact us if you have any questions or require additional information.
Very truly yours,
~?~
James P. O'Hanlon Senior Vice President - Nuclear
, cc:.U. S. Nuclear Regulatory Commission Region II Atlanta Federal Center 61 Forsyth Street, SW, Suite 23T85 Atlanta, Georgia 30303 Mr. R. A. Musser NRC Senior Resident Inspector Surry Power Station Mr. M. J. Morgan NRC Seriior Resident Inspector North Anna Power Station Commitment Summary The following represents the specific commitment made in this letter:
- 1.
The two acceptance criteria options will be more fully evaluated pending generic resolution of the use of the Code Case and/or issuance of the supplement to Generic Letter 96-06. Specific acceptance criteria will be selected tor application to the penetrations tor North Anna and Surry Power Stations by February 27, 1998. The penetrations will then be evaluated using the selected acceptance criteria tor this postulated one time faulted event and this response will be amended as applicable.
COMMONWEAL TH OF VIRGINIA
)
)
COUNTY OF HENRICO
)
The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today by J. P. O'Hanlon, who is Senior Vice President - Nuclear, of Virginia Electric and Power Company. He has affirmed before me that he is duly authorized to execute and file the foregoing document in behalf of that Company, and that the statements in the document are true to the best of his knowledge and belief.
Acknowledged before me th is d3YJJ day of ~l fu ne.,(
, 19 !fl__.
My Commission Expires: March 31, 2000.
Notary Public (SEAL:}' :