ML20082E201
| ML20082E201 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 07/25/1991 |
| From: | Wallace E TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9107310275 | |
| Download: ML20082E201 (4) | |
Text
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k Tonnessee Valey Autrody hcl Ma+et Sveet Chatimooga Tennessee 37402 July 25, 1991 U.S. Nuclear Regulat ry Commission ATTN:
Document Control Desk Washington, D.C.
20555 Gentlemen:
In the Matter of
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Docket Nos. 50-327 ennessee-Valley Authority
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5"-328 r
SEQUOYAH NUCLEAR PLANT (SQN) - UNITS 1 AND 2 - DOCKET NOS. 50-327 AND 50-323 - FACILITY OPERATING LICENSES DPR-77 AND DPR FIhE PROTECTION PLAN AND 10 C7R 50, APPENDIX R - SPECI AL REPORT 91-ll The enclosed special report provides details concerning operation with unqualified penetration seals resultin; from inadequate cor
-tion of thermal pipe movements. This conditiot was initially rs
_a oy telephone notification on July 12, 1991, and confirmed y racsimile on the same day.
This event is being repoJted in accordance with Unit 2 License Concition 2.H and Technical Specification 3.7.12, Action Statement (a).
If you have any questions concerning this submittal, please telephone M. A. Cooper at (615) 843-8422.
Very truly yours, TENNESSEE VALLEY AUTHORITY w.
E. G. Wallace, Manager Nuclear Licensing and Regulatory Affairs Enclosure ec:
See page 2
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0 j l 9107310275 910725 PDR ADOCK 05000327 d
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U.S. Nuclear Regulatory Commission July 25, 1991 cc (Enclosure):
Ms. S. C. Black, Deputy Director Project Directorate II-4 U.S. Nuclear Regulatory Commission One f4hite Flint, North 11555 Rockville Pike Rockville, Maryland 20852 Mr. D. E. LaBarge, Project Manager U.S. Nuclear Regulatory Commission One 4hite Flint, North 11555 Rockville Pike Rockville, Maryland 20852 NRC Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy-Daisy, Tennessee 37379 Mr.
B. A. Wilson, Project Chief U S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite ?900 Atlanta, Georgia 30323
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1 ENCLOSURE SQN SPECIAL REPORT 91-11 1
Description of Condition On July ll, 1991~ at 2115-Eastern dayli ht time (EDT) with both units in F
Mode 1 (100 percent power, 578 degrees Fahrenheit, and 2,235 pounds per square Inch gauge), a condition was identif'.ed involving 15 penetration sleeve seals as a result of inadequate consideration of piping thermal movements.
rhis condition was identified during reanalysis of the-Unit 2 residual heat removal (RHR) system piping for an upcoming modification. The sleeve seals c 2sist of Dow-Oorning 3-6548 room tempercture vulcanizing (RTV) silicone foam a o are located in penetrations through the walls of the RHR pump rooms to the Elevacion 653 pipe chases and the RHR and containment spray (RHR/CS) heat exchanger rooms to the Elevation 690 pipe chases.
Piping throug5 four Unit 1 and five Ui.it 2 penetrations exceeded the sxial movement criteria of 15 percent of the minimum annular distance, established by the seal manufacturer, Dow-Corning.
Additionally, piping through three Unit 1 and three Unit 2 penetrations exceeded the one-quarter-inch limit for radial movements that was also established by the manufacturer. These limits ensure that gaps, which could potentially affect
.the pressure, hydraulic, and fire rating of the seal, are not created by pipo movement throughout the life of the plant.
Upon notification of this condition, both units entered Limiting Condition of Operation (LCO) 3.7.12, Action Statement (a), at 2115 EDT, and a fire watch was established in accordance with this action at 2145 EDT.
The RHR pump rooms are equipped with detection and suppression capability; therefore,
' roving fire watch patrols will-observe these rooms, the 2HR/CS heat exchanger
. rooms are not equipped'with suppression-and detection and are being observed by continuous fire watches stationed outside the door of the heat exchanger rooms for ALARA (as low as reasonably achievable) considerations. The doors to-these rooms (Doors A68, A69, A71 and A72) have been breached since July 12, 1991, to allow these observations.
This time,n4riod is greater than the seven days specified by Action Statement (a) of Techr.':s! Specification
(_ TS) 3. 7.12; therefore, - this event is also being reported in accordance with 4
ETS 3.7.12, Action Statement (a).
A visual inspection of the 15 sleeves reve.ned thct x* many cases, some disbonding at the top of.the sleeve or at tha-pipe had c.corred, with gaps approximately one-quarter-inch wide and huving an indeterminate depth. These gaps could_have been-caused by past pipe -
am norm.si seal shrinkage.
No ather' damage to the_ seals was observei.
Through various industry notices and l~(ernr1 11rrective action documents, SQN had -identified -a generic problem with s cwr. eating chat-penetration seal-designs comply with tested confire *14-Carrective actions had been completed to qualify the shield bui.Ji, renetrations for fire barrier, hydraulic, and pressure reten_ lot ! nc-
.ts (as repc,rted in LER 50-327/87040, Revision 1, dated-February
, 1988>.
neta corrective actions completely ensured penetration qual *F'esti b,e the shield building; however, the fire u
barrier and pressure reteni!an tunctions have net been verified for remaining plant structures, as was id;ntified in a 1990 corrective action document. 'The L.
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g condition ~ described in this report -is the first confirmed example of unqualified seals in structures other than the shield building, resulting from
.the documentation problems noted above.
Because of this condition, fire watches were established in plant areas containing penetrations, as a prudent measure, to generically address the potential for unqualified seals.
For areas that are not accessible because of ALARA considerations, such as the
~RHR/CS heat exchanger rooms, thermocouples'will be installed to replace the fire watches.
Cause of Condition The original design for the RTV silicone foam seals was inadequate.
Inadequate design requirements existed for allowable pipe movement within the seals. Additionally, no mechanisms existed to trigger the piping analyst to
~
interface with the seal engineer if large pipe movements were calculated.
. Investigation to further address the cause(s) and corrective actions is ongoing and will be provided in LER 50-327/91016.
Corrective Action Upon discovery of this condition, the affected areas with suppression and-detection were included in the surveillance of roving, hourly fire watch patrols.
Continuous fire watches were established for the areas without suppression and detection.
Because of this condition, fire watches were established as'a prudent measure in plant areas containing penetrations to generically address the potential for unqualified seals.
For areas that are not e.ccessible because of ALARA considerations, such as the RHR/CS heat exchanger rooms, thermocouples will be installed to replace the fire watches.
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