ML20151Q401
| ML20151Q401 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 08/01/1988 |
| From: | Gridley R TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| NUDOCS 8808110145 | |
| Download: ML20151Q401 (2) | |
Text
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TENNESSEE VALLEY AUTHORITY
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5N 157B Lookout Place W 011988 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C.
20555 Gentlemen:
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) - PERFORMANCE TESTING OF REACTOR RELIEF AND SAFETY VALVES
Reference:
TVA letter from J. A. Domer to E. Adensam, NRC, dated March 18, 1985 Enclosed is an update to the referenced letter for SQN unit 1.
If you have any questions, please telephone Kathy S. Whitaker at (615) 870-7748.
Very truly yours.
TENNESSEE VALLEY AUTHORITY R. Gridley, Di ctor Nuclear Licensing and Regulatory Mfairs Enclosure cc (Enclosure):
Ms. S. C. Black, Assistant Director for Projects TVA Projects Division U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852 Mr. F. R. McCoy, Assistant Director i
for Inspection Programs i
TVA Projects Division U.S. Nuclear Regulatory Commission Region II
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101 Marietta Street, NW, Suite 2900 j
Atlanta, Georgia 30323 Sequoyah Resident Inspector Sequoyah Nuclear Plant 2600 Ige, Ferry Road i
Soddy DLay, Tennessee 37379 8808110145 880801 PDR ADOCK 05000327 An b4 Opportunity Employe -
P PDC m,
e 'l ENCLOSURE' PERFORMANCE TESTING OF REACTOR RELIEF AND SAFETY. VALVES SQN UNIT l I'
The original design for SQN included water-filled loop seals on both the power-operated relief valves (PORVs) and the safety / relief valves (S/RVs)~.
Reanalysis of the discharging piping loads after completion of the Electric Power Research Institute (EPRI) relief valve test program indicated that' loads caused by the discharge of the loop seal slug were excessive.
IVA decided to eliminate the PORV loop seals (by rerouting of the piping), to drain the S/RV loop seals, and to install steam trim in the S/RVs. These modifications ~were implemented on unit i during the refueling outage after fuel cycle 2.
Subsequent to this modification on unit 1, high S/RV tail pipe temperatures were observed that were interpreted to indicate valve leakage past the seat.
To eliminate the leakage, TVA reestablished the S/RV loop seals.
After evaluating the options available to resolve the issue, TVA implemented the changes (removing the PORV loop seals, draining the S/RV loop seals, and installing the steam trim in the S/RVs) on unit 2 during the refueling outage after fuel cycle 2.
Modifications and additions were made to the supports on the discharge piping to reduce the S/RV flange loads in order to reduce the likelihood of valve seat leakage. As a contingency, mcdifications were installed to allow operation with a heated loop seal to reduce the magnitude of the slug discharge piping loads; heat tracing and insulation were installed l
l on the loop seals to maintain elevated fluid temperatures; and' supports on the l
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discharge piping were added or modified to accommodate the slug discharge loads. The piping was qualified to loads predicted with the RELAP5/ MOD 1 and i
REPIPE computer codes.
Seat leakage during startup necessitated the refilling of the loop seals.
In August 1985, FQN units 1 and 2 entered' extended shutdowns.
Unit I was nearing completion of the refueling outage at the end of fuel cycle 3, and unit 2 was in fuel cycle 3.
During the extended shutdown, water trim was installed in the unit 1 and unit 2 S/RVs in keeping with the heated loop seal operation. During heatup of unit 2 af ter the extended outage S/RV seat leakage and problems with the loop seal temperature control occurred.
TVA then decided to reevaluate the options.
TVA now plans to operate units 1 and 2 with drained loop seals and steam trim in the S/RVs.
The piping wa-designed for a heated icop ceci discharge and is more than adequate for the s uam discharge. The piping has also been rigorously oualified to loads generated with RELAP5/ MODI and REPIPE for discharge of steam from the S/RVs (without PORV actuation) and for steam discharge from the PORVs.
To eliminate the problems with valve seat leakage, supports have been modified l
to reduce the S/RV flange loads to within those specified by Crosby Valve and Gauge Company (the valve manufacturer).
The valves have also been serviced and tested by Wyle Laboratories before installation.
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