ML20217A640
| ML20217A640 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 04/16/1998 |
| From: | Salas P TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9804220301 | |
| Download: ML20217A640 (6) | |
Text
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Tennessee Valley Authority, Post Office Box 2000, Soddy-Daisy, Tennessee 37379-2000 April 16, 1998 10 CFR 50.50a (a) (3) (ii)
U.
S.
Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.
C.
20555 Gentleman:
In the Matter of
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Docket Nos. 50-327 Tennessee Valley Authority
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50-328 SEQUOYAH NUCLEAR PLANT (SQN) - REQUEST FOR APPROVAL OF RELIEF FROM AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME) CODE REQUIREMENTS - REQUEST FOR RELIEF RV CHECK VALVE TESTING This letter provides TVA's Request for Relief RV-8 from compliance to ASME OM-10, 4.3.2.4 (c) Code requirement pursuant to 10 CFR 50.55a (a) (3) (ii) as hardship or unusual difficulty without a compensating increase in the level of quality and safety.
TVA is requesting NRC's prompt review and approval of the enclosed request for relief (RV-8) to support the Unit 1 Cycle 9 refueling outage that is scheduled to start September 1998.
If you have any questions regarding this response, please contact me at extension (423) 843-7071 or James D.
Smith at extension (423) 843-6672.
Sincerely, s
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o Salas Licensing and Industry Affairs Manager
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h O N Enclosure l\\
cc:
See page 2 g3 9804220301 980416 PDR ADOCK 05000327 P
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l U.S. Nuclear Regulatory Commission Page 2 April 16, 1998 cc (Enclosure):
Mr.
R. W.
Hernan, Project Manager i
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 37379-3624
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J Regional Administrator U.S.
Nuclear Regulatory Commission Region II Atlanta Federal Center 61 Forsyth Street, SW, Suite 23T85
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Atlanta, Georgia 30303-3415 1
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O ENCLOSURE q
TENNESSEE VALLEY AUTHORITY SEQUOYAH NUCLEAR PLANT (SQN)
UNITS 1 AND 2 2 *8 10-YEAR INTERVAL REQUEST FOR RELIEF NO. RV-8 Summary:
TVA performs alternate testing of some check valves as addressed in Relief Request RV-1.
Relief Request RV-1 is documented in the valve testing program basis document for the second 10-year American Society of Mechanical Engineers (ASME) interval.
That relief request identified 13 check valve groups for disassembly and inspection in accordance with the guidance of Generic Letter (GL) 89-04, Position 2.
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The proposed request for relief (RV-8) addresses Valve Group 3 as contained in RV-1.
TVA is l
requesting use of alternate testing, that would not f
require check valve disassembly and inspection, because of a significant industrial safety hazard to plant personnel associated with test activities.
The alternative testing being proposed is to apply-Technical Specification (TS) Surveillance Requirement (SR) 4.6.2.1.1.d, "Each Containment Spray train shall be demonstrated OPERABLE: At least once per 10 years by performing an air or smoke flow test through each spray header and verifying each spray nozzle is unobstructed."
The request is consistent with the NRC position contained in GL 89-04, Position 2, and as defined in NUREG-1482 for the extension of test frequencies.
Unit Affected:
Units 1 and 2 System:
Containment Spray - System No. 72 Affected Components:
Check Valves 72-547, 72-548, 72-555, and 72-556; as shown in FSAR Figure 6.2.2-1 Code Class:
2 Component Function:
Containment Spray Check Valves 72-547, 72-548, 72-555, and 72-556 open to admit flow from the containment spray and residual heat removal pumps to E-1
e supply water to the spray headers.
They close for containment isolation.
Code Requirements From Which Relief is Requested:
OM-10,
- 4. 3.2. 4 (c) states that "As an alternative to (a) or (b) above, disassembly every refueling outage to verify operability of check valves may be used."
Basis for Relief:
The containment spray system is used during accident conditions to limit containment pressure by spraying cooler water into the containment vessel atmosphere.
This spraying action reduces the temperature and pressure inside the containment vessel.
To perform the pressure reduction function, containment spray-system piping continues from the containment spray 1
d check valves, that are inside the containment vessel, to the open spray nozzles on the spray headers.
Because the spray nozzles are open, it is not possible to perform flow tests on the check valves during any mode of plant operation.
Flow testing would result in a spray of borated water into the containment vessel atmosphere and wetting of equipment in the building.
Therefore, TVA has applied the code-accepted, alternate-testing method of disassembly and inspection of these valves.
Temporary scaffolding is used to pe:.t'em check valve
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disassembly and inspection of check
.1ve internal' components.
These check valves are located near the containment spray and the residual heat removal spray headers in the top of the reactor building's containment vessel.
No permanent access to the valves exists.
The valves are reached by construction of scaffolding approximately 30-foot high.
The scaffolding is installed on top of and secured to the polar crane.
Scaffold erection and use is typically a challenge to industrial safety.
Scaffold erection, use, and disassembly for inspection of the containment spray check valves is a significant industrial safety hazard.
The check valves are either 8-inch or 12-inch, 150 pound per square inch gauge rated valves, manufactured by Aloyco.
The check valves and associated piping are constructed of stainless steel material; therefore, no degradation to valve internals is expected.
A review of past test E-2
instruction performances indicated that there have been no failures or any indication of adverse problems.
Alternative Testing:
Containment Spray Check Valves 72-547, 72-548, 72-555, and 72-556 will be demonstrated operable in conjunction with the spray nozzle verification test required by TS SR 4.6.2.1.1.d.
In demonstrating the containment spray system to be operable, TS SR 4.6.2.1.1.d requires "At least once per 10 years verify each spray nozzle is unobstructed."
To perform this test, the water' leg
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is drained between the inboard and outboard
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containment isolation valves.
An air compressor,
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with heated air capsbility, is connected to the system upstream of the check valves.
Hot air is blown through the riser piping, the inboard containment check valves, and the header nozzles.
A thermographic camera is used to verify unobstructed flow through the nozzles.
Flow through the nozzles would also verify flow through the check valves.
i Justification for the Granting of Relief:
The valves are required for the purpose of containment isolation.
The check valves are not local leak-rate tested as required by Definition H, Criterion 3, in 10 CFR 50, Appendix J, where the system is required to operate intermittently under postaccident conditions.
These spray lines are water sealed and are'not potential containment atmosphere leak paths.
A water leg is maintained in each riser between the closed outboard containment isolation valves and the spray header.
These outboard valves are leak-rate tested with water to ensure a 30-day inventory as required by TS SR 4.6.1.2.b.
NRC found this acceptable as documented in NUREG-1232, Volume 2, Section 3.6.
TVA submitted an exemption to i
Appendix J to rely on the remote manual valve outside containment, the seal water system, and the closed containment spray system outside containment as the basis for not leak-rate testing the inboard check valves to Appendix J requirements.
NRC approved this exemption on September 22, 1988.
A review of past test instruction performances for valve disassembly and inspection indicated that there have been no failures or any indication of adverse problems.
Disassembly and inspection of these check E-3
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- e, valves does not provide any additional information to i
address degradation.
A review of industry experience using the manufacturer for a key word search indicates there are no industry problems with valves of the same manufacturer.
A review of EPRI's
" Application Guidelines for Check Valves in Nuclear Plants," yielded no additional concerns for this type of valve application.
The SQN TS SR for testing the spray header and nozzles for unobstructed flow paths is consistent with the standard TS.
The SQN TS SR requires air or smoke flow testing every 10 years for
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verification of unobstructed spray nozzles.
This indicates that NRC understands the low risk for degradation in this section of the system.
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Conclusion:==
Authorization to implement the proposed alternative is requested in accordance with 10 CFR 50.55a I
(a) (3) (ii).
Compliance with the ASME Code required testing presents a hardship in the form of a personnel industrial safety risk.
The increase in the margin of safety by compliance with the ASME Code I
requirement is minimal in comparison with the J
proposed alternative testing method.
Approval of this new relief request will supersede the Group 3 valve condition documented in Relief f
Request RV-1.
Subsequent to approval of RV-8, RV-1 1
will be revised to remove the containment spray check valves.
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