ML18153C904
| ML18153C904 | |
| Person / Time | |
|---|---|
| Site: | Surry, North Anna  |
| Issue date: | 02/21/1992 |
| From: | Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 92-108, NUDOCS 9202270276 | |
| Download: ML18153C904 (16) | |
Text
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VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 February 21, 1992 U. S. Nuclear Regulatory Commission Attn.: Document Control Desk Washington, D.C. 20555 Gentlemen:
VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS 1 AND 2 NORTH ANNA POWER STATION UNITS 1 AND 2 Serial No.92-108 NL&P/TAH: R2 Docket Nos.: 50-280 50-281 50-338 50-339 License Nos.: DPR-32 DPR-37 NPF-4 NPF-7 ASME SECTION XI VALVE TESTING INTERIM RELIEF REQUEST The NRC, by letter dated October 25, 1989, issued the minutes of public meetings held to discuss Generic Letter 89-04, "Guidance on Developing Acceptable lnservice Testing Programs." One question (#25) addressed in this letter concerned stop-check valve closure testing and the acceptable means to satisfy the ASME Section XI requirements. The NRC staff stated position was "Verification of closure capability of stop check valves by using the handwheel meets the ASME Code requirements. This, however is not the preferred method of test. The NRC staff considers reverse flow testing to be a more reliable indication of valve operability."
On September 26, 1991, the NRC issued a letter, "Supplement to Minutes of the Public Meetings on Generic Letter 89-04," which modified the position on that question by stating, "If a prompt closure of these valves on cessation or reversal of flow is required to accomplish a safety-related function, closure must be verified by reverse flow testing or such other positive means as acoustic monitoring or radiography."
The response to question 25, given in your 1989 letter, indicated that driving the valve stem down onto the disk would constitute a valid ASME Code closure test for stop check valves. We have successfully applied this method of testing to the Main Steam Non-Return Valves at both North Anna and Surry Power Stations but now we must develop and implement a new testing methodology to comply with the revised NRC position as provided by your September 26, 1991 letter. We are, therefore, requesting relief to allow us to continue with our current testing program for the Main Steam Non-Return Valves at both stations until we are able to evaluate and select an alternative testing means and develop the procedures necessary to implement it.
(
9202270276 920221 i
PDR ADOCK 05000290 p
&ket Nos.: 50-280&281 50-338&339 Serial No.92-108 Page 2 of 2 contains Relief Requests V-72 for North Anna Unit 1 and V-73 for North Anna Unit 2. Attachment 2 contains Relief Requests V-50 for Surry Unit 1 and V-50 for Surry Unit 2.
These interim relief requests present our schedules for evaluating, developing and implementing the new test method to satisfy the revised NRC position.
If our evaluation demonstrates that the testing methods described in the revised NRC position are unacceptable, we will propose other tests or inspection methods to the NRC by June 30, 1993.
If you have any further questions, please contact us.
Very truly yours,
- --~t~u ~
l.~ 0 3\\__~~
W. L. Stewart Senior Vice President - Nuclear : North Anna Interim Relief Requests V-72 (Unit 1) and V-73 (Unit 2). :
Surry Interim Relief Requests V-50 (Unit 1) and V-50 (Unit 2) pc: U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, N.W.
Suite 2900 Atlanta, Georgia 30323 Mr. M. W. Branch NRC Senior Resident Inspector Surry Power Station Mr. M. S. Lesser NRC Senior Resident Inspector North Anna Power Station
ATTACHMENT - 1 ASME SECTION XI VALVE TESTING REQUEST FOR INTERIM RELIEF REQUESTS V-72 (UNIT 1)
V-73 (UNIT 2)
NORTH ANNA POWER STATION UNITS 1 AND 2
e 9:>cket Nos.: 50-280&281 50-338&339 Serial No.92-108 - Page 2 of 7 INTERIM RELIEF REQUEST V-72 (North Anna Unit 1)
I.
IDENTIFICATION OF COMPONENTS System:
Main Steam Valve(s): 1-MS-NRV-101 A 1-MS-NRV-1018 1-MS-NRV-101 C Category: C Class:
2 Function: Main Steam Non-Return Valves
- 11.
SECTION XI CODE REQUIREMENT FOR WHICH INTERIM RELIEF IS REQUESTED Exercise valve for operability to the closed position every three months.
111. BASIS FOR INTERIM RELIEF These stop check valves are currently verified closed by driving the stem down onto the disk using the valve motor operator after the main steam system has been isolated during plant shutdown.
Full stroke or part stroke exercising of these valves during power operation could result in a turbine and reactor trip.
Closure testing of stop check valves was initially addressed in the response to Question 25 in the original meeting minutes to Generic Letter 89-04.
The question and response are as follows:
Question 25:
Previous to this, it was permissible to verify closure of stop check valves simply by operation of the stem (shaft).
Is this acceptable instead of reverse flow testing?
e
Response
.cket Nos.: 50-280&281 50-338&339 Seri~No.92-108 - Page 3 of 7 Verification of closure capability of stop check valves by using the handwheel meets the ASME Code requirements.
This, however, is not the preferred method of test.
The NRC staff considers reverse flow testing to be a more reliable indication of valve operability.
However, Item C in the NRC letter dated September 26, 1991 entitled, "Supplement to Minutes of the Public Meetings on Generic Letter 89-04," provided the following revision to the Question 25 response:
If a prompt closure of these valves on cessation or reversal of flow is required to accomplish a safety-related function, closure must be verified by reverse flow testing or such other positive means as acoustic monitoring or radiography.
North Anna Power Station interpreted the original Question 25 response to mean that driving the stem down onto the disk is a valid ASME Code closure test for stop check valves. However, Item C in the revision to the Question 25 response indicates that this test method is not adequate and that reverse flow testing or some other positive means as described above be used.
It is not practical to perform a reverse flow test at power for the reason previously stated.
It is not practical to perform a reverse flow test during shutdown because it would require that the valve stems remain in the open position during plant shutdown.
To ensure double valve isolation during a normal shutdown, the secondary plant piping is isolated from the steam source by driving the stem of the stop check valves onto the disk.
After the plant is shutdown, back seat testing these valves with air would require pressurizing under the disk to show free movement, and then pressurizing over the disk to verify closure. Given the mass of the 32" diameter disk and the large volume of pipe involved, lifting the disk off the seat to show free movement is not practical.
e
.cket Nos.: 50-280&281 50-338&339 Seri~No.92-108 - Page 4 of 7 Disassembly and inspection or other visual inspection techniques would be meaningless because the disk could have been driven to the seat during normal shutdown; therefore, the inspection would not provide verification that the disk went freely to its seat after cessation of flow.
Another test method identified in Item C is radiography.
This inspection technique suffers the same limitations as the visual inspection techniq-ues discussed above.
Also, given the size of these valves (32" nominal pipe size diameter) and internal surface irregularities, radiograph resolution would be poor.
The other test method identified in Item C is acoustic monitoring.
Virginia Electric and Power Company is reviewing in-house and vendor capabilities to acoustically monitor the valves during shutdown.
IV. ALTERNATE INTERIM TESTING During the Surry Unit 2, 1993 refueling outage, one or more test methods will be evaluated in the field to determine their practicality.
If a test method, as described in Item C, can be developed, it will be implemented at North Anna Power Station Unit 1 during the next refueling outage following the Unit 1 1993 refueling outage.
Until the new test methods are implemented, North Anna Power Station will continue to test these stop check valves to the closed position by driving the stem to the disk every cold shutdown.
This test will be adequate to demonstrate that the disk can be properly positioned on the seat.
Also, free movement of the disk from the seat to the full open position is demonstrated when steam flow is established in the mainsteam lines and 100% power is achieved.
eocket Nos.: 50-280&281 50-338&339 Serial No.92-108 - Page 5 of 7 INTERIM RELIEF REQUEST V-73 (North Anna Unit 2)
I.
IDENTIFICATION OF COMPONENTS System:
Main Steam Valve(s): 2-MS-NRV-201 A 2-MS-NRV-201 B 2-MS-NRV-201 C Category: C Class:
2 Function: Main Steam Non-Return Valves
- 11.
SECTION XI CODE REQUIREMENT FOR WHICH INTERIM RELIEF IS REQUESTED Exercise valve for operability to the closed position every three months.
111. BASIS FOR INTERIM RELIEF These stop check valves are currently verified closed by driving the stem down onto the disk using the valve motor operator after the main steam system has been isolated during plant shutdown.
Full stroke or part stroke exercising of these valves during power operation could result in a turbine and reactor trip.
Closure testing of stop check valves was initially addressed in the response to Question 25 in the original meeting minutes to Generic Letter 89-04.
The question and response are as follows:
Question 25:
Previous to this, it was permissible to verify closure of stop check valves simply by operation of the stem (shaft).
Is this acceptable instead of reverse flow testing?
Response
4locket Nos.: 50-280&281 50-338&339 Serial No.92-108 - Page 6 of 7 Verification of closure capability of stop check valves by using the handwheel meets the ASME Code requirements.
This, however, is not the preferred method of test.
The NRG staff considers reverse flow testing to be a more reliable indication of valve operability.
However, Item C in the NRG letter dated September 26, 1991 entitled, "Supplement to Minutes of the Public Meetings on Generic Letter 89-04," provided the following revision to the Question 25 response:
If a prompt closure of these valves on cessation or reversal of flow is required to accomplish a safety-related function, closure must be verified by reverse flow testing or such other positive means as acoustic monitoring or radiography.
North Anna Power Station interpreted the original Question 25 response to mean that driving the stem down onto the disk is a valid ASME Code closure test for stop check valves.
However, Item C in the revision to the Question 25 response indicates that this test method is not adequate and that reverse flow testing or some other positive means as described above be used.
It is not practical to perform a reverse flow test at power for the reason previously stated.
It is not practical to perform a reverse flow test during shutdown because it would require that the valve stems remain in the open position during plant shutdown.
To ensure double valve isolation during a normal shutdown, the secondary plant piping is isolated from the steam source by driving the stem of the stop check valves onto the disk.
After the plant is shutdown, back seat testing these valves with air would require pressurizing under the disk to show free movement, and then pressurizing over the disk to verify closure. Given the mass of the 32" diameter disk and the large volume of pipe involved, lifting the disk off the seat to show free movement is not practical.
eocket Nos.: 50-280&281 50-338&339 Serial No.92-108 - Page 7 of 7 Disassembly and inspection or other visual inspection techniques would be meaningless because the disk could have been driven to the seat during normal shutdown; therefore, the inspection would not provide verification that the disk went freely to its seat after cessation of flow.
Another test method identified in Item C is radiography.
This inspection technique suffers the same limitations as the visual inspection techniques discussed above.
Also, given the size of these valves (32" nominal pipe size diameter) and internal surface irregularities, radiograph resolution would be poor.
The other test method identified in Item C is acoustic monitoring.
Virginia Electric and Power Company is reviewing in-house and vendor capabilities to acoustically monitor the valves during shutdown.
IV. ALTERNATE INTERIM TESTING During the Surry Unit 2, 1993 refueling outage, one or more test methods will be evaluated in the field to determine their practicality.
If a test method, as described in Item C, can be developed, it will be implemented at North Anna Power Station Unit 2 during the next refueling outage following the Unit 2 1992 refueling outage.
Until the new test methods are implemented, North Anna Power Station will continue to test these stop check valves to the closed position by driving the stem to the disk every cold shutdown.
This test will be adequate to demonstrate that the disk can be properly positioned on the seat.
Also, free movement of the disk from the seat to the full open position is demonstrated when steam flow is established in the mainsteam lines and 100% power is achieved.
ATTACHMENT - 2 ASME SECTION XI VALVE TESTING REQUEST FOR INTERIM RELIEF REQUESTS:
V-50 (UNIT 1)
V-50 (UNIT 2)
SURRY POWER STATION UNITS 1 AND 2
.cket Nos.: 50-280&281 50-338&339 Seri~No.92-108 - Page 2 of 7 INTERIM RELIEF REQUEST V-50 (Surry Unit 1)
I.
IDENTIFICATION OF COMPONENTS System:
Main Steam Valve(s): 1-MS-NRV-101 A 1-MS-NRV-101 B 1-MS-NRV-101 C Category: C Class:
2 Function: Main Steam Non-Return Valves
- 11.
SECTION XI CODE REQUIREMENT FOR WHICH INTERIM RELIEF 15 REQUESTED Exercise valve for operability to the closed position every three months.
111. BASIS FOR INTERIM RELIEF These stop check valves are currently verified closed by driving the stem down onto the disk using the valve motor operator after the main steam system has been isolated during plant shutdown.
Full stroke or part stroke exercising of these valves during power operation could result in a turbine and reactor trip.
Closure testing of stop check valves was initially addressed in the response to Question 25 in the original meeting minutes to Generic Letter 89-04.
The question and response are as follows:
Question 25:
Previous to this, it was permissible to verify closure of stop check valves simply by operation of the stem (shaft).
Is this acceptable instead of reverse flow testing?
Response
.cket Nos.: 50-280&281 50-338&339 Serial No.92-108 - Page 3 of 7 Verification of closure capability of stop check valves by using the handwheel meets the ASME Code requirements.
This, however, is not the preferred method of test.
The NRC staff considers reverse flow testing to be a more reliable indication of valve operability.
However, Item C in the NRC letter dated September 26, 1991 entitled, "Supplement to Minutes of the Public Meetings on Generic Letter 89-04," provided the following revision to the Question 25 response:
If a prompt closure of these valves on cessation or reversal of flow is required to accomplish a safety-related function, closure must be verified by reverse flow testing or such other positive means as acoustic monitoring or radiography.
Surry Power Station interpreted the original Question. 25 response to mean that driving the stem down onto the disk is a valid ASME Code closure test for stop check valves.
However, Item C in the revision to the Question 25 response indicates that this test method is not adequate and that reverse flow testing or some other positive means as described above be used.
It is not practical to perform a reverse flow test at power for the reason previously stated.
It is not practical to perform a reverse flow test during shutdown because it would require that the valve stems remain in the open position during plant shutdown.
To ensure double valve isolation during a normal shutdown, the secondary plant piping is isolated from the steam source by driving the stem of the stop check valves onto the disk.
After the plant is shutdown, back seat testing these valves with air would require pressurizing under the disk to show free movement, and then pressurizing over the disk to verify closure. Given the mass of the 30" diameter disk and the large volume of pipe involved, lifting the disk off the seat to show free movement is not practical.
eocket Nos.: 50-280&281 50-338&339 Serial No.92-108 - Page 4 of 7 Disassembly and inspection or other visual inspection techniques would be meaningless because the disk could have been driven to the seat during normal shutdown; therefore, the inspection would not provide verification that the disk went freely to its seat after cessation of flow.
Another test method identified in Item C is radiography.
This inspection technique suffers the same limitations as the visual inspection techniques discussed above.
Also, given the size of these valves (30" nominal pipe size diameter) and internal surface irregularities, radiograph resolution would be poor.
The other test method identified in Item C is acoustic monitoring.
Virginia Electric and Power Company is reviewing in-house and vendor capabilities to acoustically monitor the valves during shutdown.
IV. ALTERNATE INTERIM TESTING During the Surry Unit 2, 1993 refueling outage, one or more test methods will be evaluated in the field to determine their practicality.
If a test method, as described in Item C, can be developed, it will be implemented at Surry Power Station Unit 1 during the next refueling outage following the Unit 1 1992 refueling outage.
Until the new test methods are implemented, Surry Power Station will continue to test these stop check valves to the closed position by driving the stem to the disk every cold shutdown.
This test will be adequate to demonstrate that the disk can be properly positioned on the seat.
Also, free movement of the disk from the seat to the full open position is demonstrated when steam flow is established in the main steam lines and 100% power is achieved.
e
~cket Nos.: 50-280&281 50-338&339 Seri~No.92-108 - Page 5 of 7 INTERIM RELIEF REQUEST V-50 (Surry Unit 2)
I.
IDENTIFICATION OF COMPONENTS System:
Main Steam Valve(s): 2-MS-NRV-201 A 2-MS-NRV-201 B 2-MS-NRV-201 C Category: C Class:
2 Function: Main Steam Non-Return Valves
- 11.
SECTION XI CODE REQUIREMENT FOR WHICH INTERIM RELIEF IS REQUESTED Exercise valve for operability to the closed position every three months.
111. BASIS FOR INTERIM RELIEF These stop check valves are currently verified closed by driving the stem down onto the disk using the valve motor operator after the main steam system has been isolated during plant shutdown.
Full stroke or part stroke exercising of these valves during power operation could result in a turbine and reactor trip.
Closure testing of stop check valves was initially addressed in the response to Question 25 in the original meeting minutes to Generic Letter 89-04.
The question and response are as follows:
Question 25:
Previous to this, it was permissible to verify closure of stop check valves simply by operation of the stem (shaft).
Is this acceptable instead of reverse flow testing?
e
Response
.cket Nos.: 50-280&281 50-338&339 Seri~No.92-108 - Page 6 of 7 Verification of closure capability of stop check valves by using the handwheel meets the ASME Code requirements.
This, however, is not the preferred method of test.
The NRC staff considers reverse flow testing to be a more reliable indication of valve operability.
However, Item C in the NRC letter dated September 26, 1991 entitled, "Supplement to Minutes of the Public Meetings on* Generic Letter 89-04," provided the following revision to the Question 25 response:
If a prompt closure of these valves on cessation or reversal of flow is required to accomplish a safety-related function, closure must be verified by reverse flow testing or such other positive means as acoustic monitoring or radiography.
Surry Power Station interpreted the original Question 25 response to mean that driving the stem down onto the disk is a valid ASME Code closure test for stop check valves.
However, Item C in the revision to the Question 25 response indicates that this test method is not adequate and that reverse flow testing or some other positive means as described above be used.
It is not practical to perform a reverse flow test at power for the reason previously stated.
It is not practical to perform a reverse flow test during shutdown because it would require that the valve stems remain in the open position during plant shutdown.
To ensure double valve isolation during a normal shutdown, the secondary plant piping is isolated from the steam source by driving the stem of the stop check valves onto the disk.
After the plant is shutdown, back seat testing these valves with air would require pressurizing under the disk to show free movement, and then pressurizing over the disk to verify closure. Given the mass of the 30" diameter disk and the large volume of pipe involved, lifting the disk off the seat to show free movement is not practical.
.cket Nos.: 50-280&281 50-338&339 Serial No.92-108 - Page 7 of 7 Disassembly and inspection or other visual inspection techniques would be meaningless because the disk could have been driven to the seat during normal shutdown; therefore, the inspection would not provide verification that the disk went freely to its seat after cessation of flow.
Another test method identified in Item C is radiography.
This inspection technique suffers the same limitations as the visual inspection techniques discussed above.
Also, given the size of these valves (30" nominal pipe size diameter) and internal surface irregularities, radiograph resolution would be poor.
The other test method identified in Item C is acoustic monitoring.
Virginia Electric and Power Company is reviewing in-house and vendor capabilities to acoustically monitor the valves during shutdown.
IV. ALTERNATE INTERIM TESTING During the Surry Unit 2, 1993 refueling outage, one or more test methods will be evaluated in the field to determine their practicality.
If a test method, as described in Item C, can be developed, it will be implemented at Surry Power Station Unit 2 during the next refueling outage following the Unit 2 1993 refueling outage.
Until the new test methods are implemented, Surry Power Station will continue to test these stop check valves to the closed position by driving the stem to the disk every cold shutdown.
This test will be adequate to demonstrate that the disk can be properly positioned on the seat.
Also, free movement of the disk from the seat to the full open position is demonstrated when steam flow is established in the main steam lines and 100% power is achieved.