ML18153A499
| ML18153A499 | |
| Person / Time | |
|---|---|
| Site: | Surry, North Anna  |
| Issue date: | 03/12/1997 |
| From: | Ohanlon J VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 95-504A, GL-96-05, GL-96-5, NUDOCS 9703180235 | |
| Download: ML18153A499 (7) | |
Text
VIRGINIA ELECTRIC AND PowER COMPANY RICHMOND, VIRGINIA 23261 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001 Gentlemen:
March 12, 1997 VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS 1 AND 2 NORTH ANNA POWER STATION UNITS 1 AND 2 Serial No.
NL&P/MAE:
Docket Nos.
License Nos.
96-504A RB 50-280/-281 50-338/-339 DPR-32/-37 NPF-4/-7 GENERIC LETTER 96-05 PERIODIC VERIFICATION OF DESIGN-BASIS CAPABILITY OF SAFETY-RELATED MOTOR-OPERATED VALVES On September 18, 1996, the NRC issued Generic Letter 96-05, entitled "Periodic Verification of Design-Basis Capability of Safety-Related Motor-Operated Valves." The generic letter requested that each addressee establish a program, or ensure the effectiveness of its current program, to verify on a periodic basis that safety-related motor operated valves (MOVs) continue to be capable of performing their safety-related functions within the current licensing bases of the facility.
The generic letter also requested that the program ensure that changes in required performance resulting from degradation (such as those caused by age) can be properly identified and accounted for. Finally, the generic letter requested that periodic verification programs previously developed in response to Generic Letter 89-1 0 be reviewed to determine whether any changes are appropriate in light of the information contained in Generic Letter 96-05.
The generic letter required a 60 day response and a 180 day response. The 60 day response required utilities to indicate whether or not they would implement the requested actions and submit a schedule for completing implementation. The 180 day response required utilities to provide a written summary description of its MOV periodic verification program established in accordance with the requested actions.
Virginia Electric and Power Company's (Virginia Power's) 60 day response was documented in a letter dated November 13, 1996 (Serial No.96-504). This letter fulfills the 180 day response request. A summary description of our enhanced MOV periodic verification program is attached.
Virginia Power had previously developed a periodic verification program in response to Generic Letter 89-10. This program was reviewed in light of Generic Letter 96-05 and is presently being enhanced to address the issue of possible MOV performance changes resulting from age-related degradation. The enhancement consists of the temporary addition of dynamic diagnostic testing on selected MOVs and is currently
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diagnostic tests will then be evaluated and a determination will be made as to whether dynamic diagnostic testing needs to be continued; expanded or terminated.
Selection of MOVs for this additional testing is on-going.
This additional dynamic diagnostic testing is scheduled to begin during the Unit 2 refueling outages at Surry and North Anna Power Stations which are currently scheduled for October 4, 1997 and April
- 3~ 1998, respectively. Commitments made by this letter are specifically noted below.
If you have any questions, please contact us.
Very truly yours, James P. O'Hanlon Senior Vice President - Nuclear Attachment Commitments made by this letter:
- 1. The enhanced MOV periodic verification program which includes dynamic diagnostic testing on selected MOVs is scheduled to begin during the Unit 2 refueling outages at Surry and North Anna Power Stations which are currently scheduled for October 4, 1997 and April 3, 1998, respectively.
- 2. The results of these additional dynamic diagnostic tests will then be evaluated and a determination will be made as to whether dynamic diagnostic testing needs to be continued, expanded or terminated.
cc:
Regional Administrator U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, N.W.
Suite 2900 Atlanta, Georgia 30323 Mr. R. A. Musser NRC Senior Resident Inspector Surry Power Station NRC Senior Resident Inspector North Anna Power Station
VIRGINIA POWER MOV PERIODIC VERIFICATION PROGRAM I.
Purpose Establish the requirements for implementing the motor operated valve (MOV) periodic verification program for Virginia Power at Surry and North Anna Power Stations. The periodic verification program consists of preventive maintenance, static diagnostic testing and dynamic diagnostic testing.
II.
Scope The Virginia Power MOV Periodic Verification Program addresses MOVs which were included in the scope of Generic Letter 89-10.
This program is being enhanced to address possible MOV changes in performance resulting from degradation as discussed in GL 96-05.
Ill.
Selection of MOVs Preventive maintenance and static diagnostic testing will be performed on MOVs within the scope of this program.
Potential candidates for dynamic diagnostic testing are the testable MOVs within the scope that are susceptible to age-related degradation and have a design margin of less than 25%. These MOVs will be grouped based on like valve design.
A representative MOV from each group will be selected for testing based upon safety significance and application.
A.
Ability To Be Tested
- 1.
Ability to test under conditions which approach design basis conditions and are repeatable.
- 2.
Ability to monitor necessary MOV parameters such as a)
Thrust b)
- 3.
Ability to monitor system conditions such as a)
Pressure b)
Flow c)
Differential pressure d)
System temperature Page 1 of 5
,r B.
Design Margin
- 1.
Gate and Globe Valve Margin Margin =(Actuator Output Thrust - Required Thrust)
Required Thrust a)
Actuator Output Thrust (1)
For torque switch controlled MOVs, this value is the thrust at torque switch trip.
(2)
For limit switch controlled MOVs, this value is the thrust capability of the motor, gearing and stem nut at design basis conditions, with consideration of weak link.
b)
Required Thrust Calculated stem thrust at design basis conditions.
- 2.
Quarter Turn Valve Margin Margin= (Actuator Output Torque - Required Torque)
Required Torque a)
Actuator Output Torque (1)
No active torque switch The torque capability of the motor and gearing at design basis conditions with the consideration of weak link.
(2)
Active torque switch The lesser of the torque capability of the motor and gearing at design basis conditions with the consideration of weak link and the stem torque measured at torque switch trip.
b)
Required Torque Calculated stem torque at design basis conditions.
Page 2 of 5
I I
C.
Safety Significance D.
- 1.
The safety significance of each MOV will be evaluated using probabilistic safety analysis (PSA) models.
The MOVs will be categorized as having a high, medium, or low risk significance.
- 2.
An Expert Panel will review the MOV ranking and may adjust it based upon their discussion.
The Station Nuclear Safety and Operating Committee will review the results as appropriate.
Application MOVs that are not susceptible to age-related degradation will not be considered as a candidate for dynamic diagnostic testing. The MOVs in each system will be reviewed for the following factors and a list of MOVs that are challenged by operating or environmental conditions will be compiled.
- 1.
Fluid type and cleanliness which could lead to degradation (e.g., valves in raw water systems).
- 2.
Stroking conditions which could induce age-related degradation (e.g.,
valves normally stroked under significant differential pressure).
IV.
Frequencies A.
Preventive Maintenance frequencies are governed by the appropriate administrative procedure.
B.
Static diagnostic testing for each MOV will be conducted once every 3 refueling outages or 5 years, which ever is longer.
C.
Dynamic diagnostic testing will be conducted on the selected MOVs for three consecutive periods. Each period will be a minimum of one year.
D.
Test frequencies for static and dynamic diagnostic testing may be modified based upon the following conditions.
1.
Plant specific maintenance data
- 2.
Plant specific test data
- 3.
Manufacturer's recommendations
- 4.
Industry information
- 5.
P SA reviews
- 6.
Regulatory requirements
- 7.
Maintenance Rule information Page 3 of 5
- 8.
Advances in testing and evaluation methods E.
Changes in testing and preventive maintenance frequencies and methods will be formally evaluated and documented in accordance with the appropriate administrative procedures.
V.
Preventive Maintenance A.
The purpose of preventive maintenance is to both identify and prevent age and environmentally initiated degradations.
B.
A preventive maintenance program is established for MOVs in accordance with the appropriate administrative procedure.
C.
Preventive maintenance evaluations will consider the following items:
- 1.
Manufacturer's recommendations
- 2.
Equipment operating history
- 3.
Engineering analysis
- 4.
Industry findings and recommendations
- 5.
Lessons learned and Station experience
- 6.
Conditions of operation (system and environmental)
VI.
Static MOV Diagnostic Testing A.
The purpose of static diagnostic testing is to detect age-related degradations in motor, actuator, and stem factor.
These degradations may be manifested in a decrease in motive force to the valve.
B.
MOVs within the scope will have periodic static testing scheduled through the use of the preventive maintenance program.
C.
Diagnostic evaluations will be documented in a test report.
VII.
Dynamic Diagnostic MOV Testing A.
Dynamic diagnostic testing of MOVs is performed to identify age-related degradations in the valve assembly that may lead to an increase in the thrust or torque requirements.
B.
MOVs within the scope will have dynamic diagnostic testing scheduled through the use of the preventive maintenance program.
C.
As more information is collected, MOVs may be removed from the testing frequency discussed in Section IV.C with written justification. In addition, new MOVs may be added based on utility or industry experience.
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D.
-Approved regulatory analytical techniques in combination with static test data may be applied to minimize the MOVs that are selected for dynamic diagnostic testing.
VIII.
Post Maintenance Testing Post maintenance testing will be controlled through the use of the appropriate administrative procedure to ensure that the MOV continues to be capable of performing its design functions following maintenance.
IX.
Acceptance Criteria Acceptance criteria will be delineated in the appropriate procedures and will ensure that the MOV is capable of performing its design basis functions.
X.
Corrective Action A.
Corrective action will be initiated for any MOV for which test analysis shows it may not have sufficient margin to ensure operability at the time of the next scheduled test. This corrective action can include rescheduling of a diagnostic test which would monitor the MOV's condition at a time to ensure continued operability.
B.
Any conditions which would cause the MOV to become inoperable before the next scheduled test will be completely evaluated to assess the impact on related MOVs in the same group.
C.
If any differential pressure testing evaluations show a negative margin trend, or an MOV appears to require more margin than was previously estimated, then the margin values should be revised. Margin revisions to other similarly grouped MOVs should also be evaluated.
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