ML20209H044

Forwards Response to NRC 990326 RAI Re GL 96-05, Periodic Verification of Design-Basis Capability of Safety-Related Movs. Summary of Util Commitments Provided in Attachment 2

ML20209H044
Person / Time
Site:	Wolf Creek
Issue date:	07/14/1999
From:	Mckinney B WOLF CREEK NUCLEAR OPERATING CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GL-96-05, GL-96-5, WO-99-0060, WO-99-60, NUDOCS 9907200108
Download: ML20209H044 (6)

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W4) LF NUCLEAR CREEKOPERATING CO Brc T. Mc-Kinney Vice President Plant Operations and Plant Manager JUL 141999 WO 99-0060 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Mail Station Pl-137 Washington, D. C. 20555

Reference:

Letter dated March 26, 1999, from K. M. Thomas, NRC, to O. L. Maynard, WCNOC

Subject:

Docket No. 50-482: Response to Request for Additional Information Regarding Generic Letter 96-05, " Periodic Verification of Design-Basis Capability of Safety-Related Motor-Operated Valves" Gentlemen:

Attached is Wolf Creek Nuclear Operating Corporation's (WCNOC) response to the Request for Additional Information (RAI) contained in the Reference for the Wolf Creek Generating Station (WCGS). The RAI requested additional information to complete the generic letter review, as discussed in a conference call between WCNOC staff and NRC staff on March 23, 1999.

Attachment 2 provides a summary of commitments made in this submittal.

If you have any questions concerning this matter, please contact me at (316) 364-4112, or Mr. Michael J. Angus at (316) 364-4077 Very truly yours, m

Britt T. 1:c-Kinney BTM/rir J

Attachments cc: J. N. Donohew (NRC), w/a W. D. Johnson (NRC), w/a E. W. Merschoff (NRC), w/a Senior Resident Inspector (NRC), w/a

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9907200108 990714 PDR ADOCK 05000482 P PDR PO. Box 411/ Burlington, KS 66839 / Phone: (316) 364-8831 An Equal Opportunity Employer M F 'HC. VET

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STATE OF KANSAS )

) SS-COUNTY OF COFFEY )

Britt T. Mc-Kinney, of lawful age, being first duly sworn upon oath says that he is Vice President Plant Operations and Plant Manager of Wolf Creek Nuclear Operating Corporation; that he has read the foregoing document and 'cnows the content thereof; that he has executed that same for and on behalf of said Corporation with full power and authority to do so; and that the facts therein stated are true and correct to the best of his knowledge, information and f belief.

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r By . h Britt T. Mc-KiM ey s )

Vice President Plant Operations and Plant Manager J

SUBSCRIBED and sworn to before me this f day of , 1999.

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. Attachment 1 to WO 99-0060

,Page 1 of 3 Response to Request for Additional Information - Generic Letter 96-05,

" Periodic Verification of Design-Basis Capability of Safety-Related Motor-Operated Valves" NRC Ouestion 1.

,By' letter dated July 21, 1995, the NRC staff closed its review of the motor-

' operated valve (MOV) program implemented at the Wolf Creek Generating Station (Wolf Creek) in response to Generic Letter (GL) 89-10, " Safety-Related Motor-Operated Valve . Testing and Surveillance," based on the results of NRC Inspection Peport 50-482/95-04 (dated March 22, 1995) and information contained in a letter from the licensee dated May 19, 1994. In the inspection report, the NRC staf f discussed certain aspects of WCNOC's MOV program to be addressed over the long term, including the need to revise the thrust calculations for valves BBHV0013, BBHV0014, BBHV0015, and BBHV0016 to use more conservative valve factors. In its July 21, 1995, letter, the staff noted that WCNOC committed to dynamically test a sample of butterfly valves to validate its butterfly valve setup methodology. Describe the actions WCNOC has taken to address the specific long-term aspects of the MOV program at Wolf Creek noted in the NRC inspection report and the staff's letter dated July 21, 1995.

WCNOC Response WCHOC revised thrust calculations for valves BBHV0013, BBHV0014, BBHV0015 and BBHV0016 by increasing the minimum thrust requirements. The minimum thrust requirements were increased to reflect a more conservative methodology for interpolating diagnostic data from higher than design basis conditions.

Subsequent to this revision of the minimum thrust requirements, WCNOC further optimized the subject MOVs such that the modified actuators are capable of accommodating a valve disc to seat friction coefficient in excess of 1.0 with margin.

WCNOC committed to perform differential pressure testing on a series of butterfly motor-operated valves to confirm their capability to meet design-basis operating requirements. The sample of valves included one each of five families of butterfly valves included in the Generic Letter 89-10 MOV population. These valves were all tested at differential pressure conditions during the eighth refueling outage. Four of the five valves were tested at or above the design basis differential pressure while the fifth valve was tested at 73% of design basis differential pressure. The test data was evaluated at design basis conditions and all valves were shown to meet design basis requirements with margin.

WCNOC has completed its periodic re-verification of dynamic testing performed on three gate valves and two globe valves as described in Reference 1.

Analysis of the dynamic test data did not reveal age related degradation of the valve disc to seat friction coefficients. In addition, WCNOC is participating in the Joint Owners' Group (JOG) MOV periodic verification program. Dynamic Testing performed to date to support JOG consists of two gate valves tested in each of the last two refueling outages.

Transition of the existing periodic verification program to the JOG periodic verification program at WCNOC will be accomplished upon completion of tne site-specific risk ranking process as described in response to question # 2 ,

below. The existing periodic verification program as detailed in Reference 1 i and the GL 96-05 180 day response (Reference 2) will continue to be applied to WCGS MOVs until such time that transition to the JOG periodic verification program can be completed.

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> Attachment 1 to WO 99-0060

,Page 2,of 3 NRC Question 2.

By letter dated March 17, 1997, WCNOC stated its commitment to implement the Joint Owners Group (JOG) Program on MOV Periodic Verification in response to GL 96-05. The JOG program specifies that the methodology and discrimination

, criteria for ranking MOVs according to their safety significance are the I

' responsibility of each participating licensee. As Wolf Creek is a pressurized water reactor (PWR) nuclear plant designed by Westinghouse, did WCNOC apply the Westinghouse Owners' Group (WOG) methodology for ranking MOVs based on their safety: significance as described in WOG Engineering Report V-EC-1658-A (Revision 2, dated August 13, 1998), " Risk Ranking Approach of Motor-Operated Valves in response to Generic Letter 96-05," and the NRC safety evaluation dated-April 14, ,1998? If not, describe the methodology used for risk ranking MOVs at Wolf Creek in more detail, including a description of (1) the process used to develop sample lists of high-risk MOVs from the Westinghouse plants; and (2) how expert panels were used to evaluate MOV risk significance. ,

1 WCNOC Response WCNOC is currently developing its risk ranking of motor-operated valves using the Westinghouse Owners' Group (WOG) methodology as described in WOG Engineering Report V-EC-1658-A (Revision 2, dated July, 1998). The methodology is being implemented in accordance. with the conditions and limitations described in the NRC Safety Evaluation dated April 14, 1998.

NRC Question 3.

'The JOG program focuses on the potential age-related increase in the thrust or torque required to operate valves under their design-basis conditions. In the NRC safety evaluation of the JOG program, dated October 30, 1997, the NRC staff specified that licensees are responsible for addressing the thrust or torque delivered by the MOV motor actuator and its potential degradation.

Describe the plan at Wolf Creek for ensuring adequate ac and de MOV motor actuator output capability, including consideration of recent guidance in

'Limitorque Technical Update 98-01 and its Supplement 1.

WCNOC Response The MOV program established at WCNOC accounts for potential valve and/or actuator degradation by including a specific degradation factor in MOV setup windows. The degradation margin is available to accommodate potential valve and/or actuator aging mechanisms. The degradation margin is in addition to other margin allowances such as diagnostic equipment accuracy, torque switch repeatability, rate-of-loading, etc. The degradation margin is also independent of ' the inherent conservatism associated with the design basis calculations. Design inputs that establish thrust or torque requirements, such as bounding disc / seat coefficients, conservative maximum expected differential pressure values, bounding stem-to-stem nut friction coefficients, and design packing friction loads, yield additional margin to account for potential valve and/or actuator aging mechanisms. The WCNOC diagnostic testing philosophy also provides additional inherent margin to account for potential valve and/or l actuator degradation. The torque switch settings of the MOV are set as high in ' the - setup window as practicable for torque-closed valves in order to optimize the margin available for potenti 1 degradation.

l In addition to the above, WCNOC preventative maintenance activities are l designed to detect changes in actuator condition that are indicative of degraded performance. If a degraded condition exists, corrective maintenance is performed.f Also, the actuator'and valve stem are lubricated on a periodic basis to ensure an optimum performance level. Trending of static diagnostic test results , provides confidence of capturing and recording actuator output changes.resulting from potential aging effects.

• . Attachment I to WO 99-0060

, ,Page 3 of 3 WCNOC .has evaluated each of its' motor-operated valves with respect to Limitorque Technical Update (LTU) 98-01 and its Supplement 1 Although the Limitorque guidance resulted in a general reduction in actuator capacity, all MOVs were shown to. possess sufficient - actuator capability to perform their safety related functions. WCNOC has initiated a design review with the objective of restoring lost margin. ~ Implementation of corrective actions to

.rrstore lost margin is ongoing and has been completed for several MOVs.

References

1. . Letter dated May 19, 1995 from N. S. Carns, WCNOC to USNRC.

2. Letter dated March 17, 1997 from R. A. Muench, WCNOC to USNRC.

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-, Attachment 2 to WO 99-0060 P. age 1.of 1 LIST OF COMMITMENTS The following table identifies those actions committed to by Wolf Creek Nuclear Operating Corporation (WCNOC) in this document. Any other statements in this submittal are provided for information purposes and are not considered to be commitments. Please direct questions regarding these commitments to Mr.

Michael J. Angus, Manag.er Licensing and Corrective Action, (316) 364-4077 COMHITMENT Due Date/ Event None

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