ML20206C654

Forwards Response to NRC 990127 RAI Re GL 96-05 for Sequoyah Nuclear Plant,Units 1 & 2

ML20206C654
Person / Time
Site:	Sequoyah
Issue date:	04/23/1999
From:	Salas P TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GL-96-05, GL-96-5, TAC-M97100, TAC-M97101, NUDOCS 9905030132
Download: ML20206C654 (8)

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RA Tonnessee Vaney Aumordy Post Odice Bon 3X Suddy-D&sy Tennessee 37379 April 23, 1999 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555 Gentlemen:

TENNESSEE VALLEY AUTHORITY (TVA)- SEQUOYAH NUCLEAR PLANT (SON) UNITS 1 AND 2 - DOCKET NOS. 50-327 AND 50-328 -

FACILITY OPERATING LICENSE DPR-77 AND DPR RESPONSE TO NRC QUESTIONS CONCERNING GENERIC LETTER 96-05

Reference:

NRC letter to TVA dated January 27, 1999, " Request for Additional Information on Response to Generic Letter 96-05 for Sequoyah Nuclear Plant Units 1 and 2 (TAC Nos. M97100 and M97101)" j The enclosure to this letter provides the additional information requested in the referenced letter. If you have any questions about this response, please telephone me at (423) 843-7170 or J. D. Smith at (423) 843-6672.

Sincerely, '

[ W Salas Li' censing & Industry Affairs Manager i

Subscribed Jo and sworn to bef e 26 - day of April lYl l $ ) $A.s Notary @dblic "

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l Enclosure

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9905030132 995423 PDR ADOCK 05000327 P PDR _

1 U.S., Nuclear Regulatory Commission

'Page 2 April 23,-1999 Enclosure cc (Enclosure):

Mr. R. W. Hernan, Project Manager U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852-2739 NRC Resident Inspector .

Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy-Daisy, Tennessee 37384-3624 Regional Administrator U.S. Nuclear Regulatory Commission ,

Region II {

Atlanta Federal Center i 61 Forsyth Street, SW, Suite 23T85 l Atlanta, Georgia 30303-3415 ,

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ENCLOSURE Response To NRC Request For Additional Information Regarding Sequoyah Nuclear Plant Letter 96-05 Program NRC QUESTION NUMBER 1 In NRC Inspection Report No. 50-327 & 328/97-18, the NRC staff closed its review of the motor-operated valve (MOV) program implemented at Sequoyah Nuclear Plant (Sequoyah) in response to Generic Letter (GL) 89-10, " Safety-Related Motor-Operated ValveI Testing and Surveillance," based on the results of the inspection and the licensee's plan to resolve several outstanding MOV issues as described in a letter dated February 12, 1998. In the inspection report, the NRC staff discussed certain aspects of the licensee's MOV program to be addressed over the long term. For example, the inspectors noted that (1) additional industry valve factor information would be gathered for Walworth, Anchor / Darling, and Copes Vulcan gate valves; and (2) margin improvements were scheduled for valves 1/2FCV-72-002 and 1/2FCV-72-039 during the next outage for each unit. In addition to the NRC inspection report items, the licensee committed in its February 12, 1998, letter to take specific actions, including (1) use of the Electric Power Research Institute MOV Performance Prediction Methodology to establish thrust requirements for gate valve Grou.ps 1, 2, and 8; (2) application of additional industry information and revision of necessary calculations for Sequoyah's Pratt butterfly valves; and (3) implementation of maintenance improvements for the Unit l ' pressurizer power operated relief valve (PORV) block valves during the Fall 1998 outage. The Tennessee Valley Authority (TVA) should describe the actions taken to address the specific long-term aspects of the MOV program at Sequoyah noted in the NRC inspection report and its letter dated February 12, 1998.

TVA RESPONSE:

TVA has completed the actions included in the February 12, 1998 letter with one exception, the Unit 2 containment spray valves. .The commitment is to implement actuator design changes to increase the capabilities of these valves during the Unit 2 Cycle 9 refueling outage that began on April 18, 1999. Note that NRC Inspection Report No. 50-327/98-09 and 50-328/98-09 dated November 9, 1998, provides a status of these actions.

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. . 1 Actions that were taken to address the above question are

'discubsed in NRC Inspection Report 50-327, -328/98-09 except for the industry valve factor item. This information is provided below and supplements the information in the inspection report regarding the use of the 0.6 valve factor.

Information Regarding 0.6 Valve Factor

1. Gate Valve Group 9, Walworth 3-inch /1500# solid wedge gate valves.

SON initially utilized results from tests performed on two similar valves at Watts Bar Nuclear Plant to justify applying a 0.60 valve factor to Gate Valve Group 9. The closing valve factors obtained from the Watts Bar tests were 0.519 and 0.146, exhibiting a larger difference than expected for similar valves. The cause for this large variation was not explained. To satisfy this concern, the Electric Power Research Institute (EPRI) performance prediction methodology (PPM) was performed using the default valve factor values and incorporated into the associated calculations.

2. Gate Valve Groups 10, 14, and 21: Anchor / Darling 8, 18, and 14-inch /300# double-disc gate valves.

SON initially used in plant test results from Gate Valve Group 22 (Anchor / Darling 8-inch /300# double-disc gate valves) to justify applying a 0.60 valve factor to these three groups. NRC inspectors found some weakness in the support for this value because of the variability in the valve factors (0.23 to 0.59) determined from Group 22 test data and because Group 22 valves were significantly smaller (i.e., 8 inches) than the valves in Groups 14 and

21. The concern regarding these valves was limited, since they have the capability of accommodating much higher (1.2 or greater) valve factors than 0.60.

These valves are double-disc valves for which two friction factors must be considered. At initial disc bottoming, the dp force provides seating contact forces. The stem then drives the disc against the seats using a wedging mechanism. This results in one valve factor to reach the valve bottom (flow isolation) and a second friction factor to spread the discs (wedge friction).

The valves in Groups 10, 14, and 21 are not required to perform a function that includes a specified " critical" leakage requirement. Therefore, only the flow isolation friction factor applies.

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I Valve No. 1-FCV-074-033 is the valve in Group 22 (as discussed above) which demonstrated the highest friction factor (i.e., 0.59). This is one of the valves that SON is dp testing in support of the Joint Owners Group (JOG) program. The valve has been tested again and the friction factors were reduced in the closing direction from 0.48 to 0.45 and opening from 0.59 to 0.55. This is due to the more stringent controls placed on dp testing by the JOG program, which refines the test data to reflect the true condition of the valve.

The valves in Groups 10, 14, and 21 also have system design temperatures of 400 degrees F. EPRI TR-103232 (Table 3-2) suggests a bounding friction factor of 0.5 at temperatures of 400 to 500 degrees and 0.6 at temperatures ranging from 100 to 200 degrees for these Anchor / Darling double-disc valves.

Regarding the concern raised relative to using dp test ,

data for 8-inch valves in Group 22 to justify the 0.60 valve factor for the larger (18 and 14 inches) valves in l y

Groups 14 and 21; testing performed by Commonwealth Edison i demonstrates a general trend of decreasing valve factor with increasing size. The testing establishes a

" conservative group valve factor" for this type of valve, which ranges from a high value of 0.72 for a 3-inch valve (smallest size shown) to a low of 0.59 for a 12-inch valve (largest size shown). The SON valves in Groups 14 and 21 are 18 and 14 inches. This further supports the 0.6 friction factor used at SQN.

3. Gate Valve Group 23, Copes Vulcan 14-inch /1500# double-disc gate valves.

TVA initially used the results of open stroke tests performed on four similar valves at Diablo Canyon to justify a 0.60 valve factor for Group 23. The adequacy of the testing was questioned by NRC inspectors as they found that the tests had been performed with hydro pumps for the pressure source instead of system pumps, resulting in little flow. Also, TVA did not have valve factor data for the closing direction, which was a safety function direction for these valves. The concern regarding these valves was limited, since the valves are capable of accommodating a much higher (0.85) valve factor than would be expected for gate valves.

The Diablo Canyon (Hydro) dp test data is the only dp data known to be available for these Copes Vulcan valves.

Additionally, the EPRI performance prediction program does not directly address these valves.

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l The New York Power Authority _ (NYPA) utilizes these Copes  !

l Vulcan valves in the same application as SON. NYPA l contracted MPR Associates to perform an EPRI PPM analysis, which was done based on the similarities between the Copes

Vulcan and Anchor / Darling valves. The MPR report justifies the use .f a 0.6 valve factor for these Copes Vulcan valves. This further supports the 0.6 friction factor-used at SQN.

l NRC QUESTION NUMBER 2:

l TVA indicates that its MOV static diagnostic periodic verification program will include test methods at the valve and the motor control center. Will diagnostic data be obtained for all GL 96-05 MOVs, including gate, globe and butterfly valves? If not, TVA should describe its plans to monitor degradation in capability for those MOVs not diagnostically tested.

l TVA RESPONSE:

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l Yes, diagnostic data is obtained for the MOVs outlined in

[ GL 96-05.

NRC QUESTION NUMBER 3: j TVA should briefly describe its plans for the use of test data from the motor control center (.MCC) including (1) correlation of new MCC test data to existing direct force measurements; (2) interpretation of changes in MCC test data to changes in MOV thrust and torq%3 performance; (3) consideration of system accuracies and sensitivities to MOV degradation for both output and operation performance requirements; and (4) validation of MOV operabilitu using MCC testing.

l TVA RESPONSE:

Currently, TVA intends to use the MCC diagnostic test method to monitor degradation for Henry Pratt butterfly valves only.

We will continue to monitor the industry effort relative to MCC testing and may chose to utilize this method in the future for gate and globe valves, as appropriate.

The Henry Pratt butterfly valves are equipped with Limitorque actuators, including HBC gearboxes. The yoke and valve to actuator connections block direct access to the valve stem and prevents installation of strain gauges for direct torque measurements. The actuator torque switches are not utilized te

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in the control circuitry for any of these valves. The valves are controlled by a position limit switch in both the open and close directions. Therefore, full torque capability of the motor and actuator is provided to close or open these valves as required.

Periodic verification tests are designed to detect mechanical degradation that could affect the output torque capability of these actuators or the torque requirements of the valves.

These tests employ MCC based motor torque (quantitative data) to assess performance and functional margin.

In order to use motor torque measurements to determine functional margin, the actuator throughput efficiency must be known. Local instrumentation to measure the actuators output torque cannot be used. A laboratory test program is used to establish the proper relationship (correlation) between input motor torque and output actuator torque for the affected actuators.

Testing in a laboratory environment of a statistically valij sample of procotype actuators meeting the specifications of d the plant-installed actuators is required. Motor torque test results are compared in order to ensure that the performance of the laboratory specimens is similar to the plant installed equipment. These actuators are tested on precision torque stands at loads and load rates expected during plant testing conditions. The resulting efficiency values are analyzed and established for use during future periodic verification data analysis. Equipment measurement errors are combined with uncertainties in ef ficiency and allowance for degradation is included in the assessment. Functional margin is assessed during periodic verification tests by comparison of running load measurements plus the design basis differential pressure requirement to the torque capability of the motor at reduced voltage.

NRC QUESTION NUMBER 4:

The Joint Owners Group (JOG) program focuses on the potential sge-related increase in the thrust or torque required to operate valves under their design-basis conditions. In the i

NRC safety evaluation dated October 30, 1997, on the JOG progra.n , the NRC staff specified that licensees are responsible for addressing the thrust or torque delivered by the MOV motor actuator and its potential degradation. In a letter dated April 28, 1998, the licensee stated that potential actuator degradation would be identified through review and trending of actua tor performance parameters. The licensee shoula describe the actions taken at Sequoyah for ES

ensuring adequate ac and dc MOV motor actuator output

' capability, including consideration of recent guidance in Limitorque Technical Qadate 98-01 and Supplement 1 in more detail.

TVA RESPONSE:

TVA/SQN has reviewed Limitorque Technical Update (TV)-98-01 and Supplement 1. In-plant reviews were performed for alternating current powered actuators in accordance with TU 98-01. This review is documented in SON's Corrective Action Program. A list of MOVs requi. ring specific I configuration review was sent to Limitorque as recommended by I TU 98-01. 'the results of these reviews are being  !

incorporated into the actuator sizing portion of the MOV I design basis calculation, as part of SON's GL 96-05 Program.  !

Additionally, SON's GL 96-05 Program requires monitoring and  !

trending of actuator performance parameters.

1 These include: l J

l e thrust / torque at control switch trip i e thrust / torque at unseating j

e total thrust / torque e average running thrust / torque j e average running current e peak inrush current .

e spring pack displacement at control switch trip e stroke time

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e stem factor at control switch trip, and e rate of loading when DP data is available 1

i TVA/ SON is an active member of the JOG and any new '

recommendations from the JOG regarding the direct current MOVs will be evaluated and incorporated into the MOV Program, as appropriate. It should be noted that there are only two (vr.c per unit) direct current actuators.

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