ML20246G286
| ML20246G286 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 07/06/1989 |
| From: | Tucker H DUKE POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 8907140218 | |
| Download: ML20246G286 (4) | |
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DUKE POWER GOMPANY
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P.O. Box 33180 CHARLOTTE, N.O. 28242 HAL B. TUGKER TELernowe vms Pnemenwr (704) 373 4 531 RUCLEAM PRespUCTION i:
July.5, 1989-1 U. S. Nuclear Regulatory Commission Washington, D.C.
20555-Attent. ion: Document Control Desk
Subject:
Catawba. Nuclear Station, Units'1 and 2 Docket Nos. 50-413 and 50-414 Special Report.-
Gentlemen:
My May 11, 1989 letter to the Document Control Desk transmitted a Special Report concerning the inoperability of the Cathodic Protection System. This report was submitted pursuant to Catawba Technical Specifications 6.9.2, 3.8.1.~1.2, and.
4.8.1.1.
Please find attached an-update to my May 10, 1989 submittal including actions taken to return the Cathodic Protection System to operable status.
Ve y truly yours, f
H B. Tucker JGT102/lcs.
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Mr. S. D. Ebneter Regional Administrator,. Region II
.U. S. Nuclear Regulatory Commission 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 Mr. W. T. Orders NRC Resident Inspector 1 -
Catawba Nuclear Station l
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n 8907140218 890706 PDR ADOCK 05000413
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CATAWBA NUCLEAR STATION UPDATE TO SPECIAL REPORT DATED MAY 11, 1989 CATHODIC PROTECTION SYSTEM TECHNICAL SPECIFICATIONS 3.8.1.1(G), 4.8.1.1.2(d)
On April 11, 1989, the Cathodic Protection System was declared inoperable after the system did not pass the acceptance criteria of the sixty (60) day surveillance.
Failure to restore the system to operable status within the required period of ten (10) days resulted in implementing action statement "g" of Catawba Technical Specifications 3.8.1.1 and 6.9.2..
i On April 11, 1989, while performing the sixty (60) day surveillance on Rectifiers No. 7 (Unit 1 D/G Fuel Storage Tank Cathodic Protection) and No. 3 (Unit 2 D/G Fuel Storage Tank Cathodic Protection), the readings for Test Stations TS-34, TS-35, and TS-36 (Rectifier No. 7) and TS-19 (Rectifier No. 3 were found to be below the acceptance criteria indicating inadequate cathodic protection of the D/G Fuel Storage Tank Pipes. The system was declared inoperable and Design Engineering was contacted.
On April 17, 1989, the station (Nuclear Production Department) and Design Engineering personnel tested the system by checking for proper voltage on the i
l anodes associated with Rectifiers Nos. 7 and 3.
During this testing, several anodes were found to have no voltage supplied to them indicating cut or broken buried power cables. Following the testing, it was determined that one or more of the following could have caused the low voltage readings at the Test Stations.
- 1) The loss of voltage at the anodes.
- 2) Possible deteriorating Test Stations due to age.
- 3) Possible deteriorating anodes.
Based on the above, it was determined that a survey of the areas would be required. However, this could not be accomplished until voltage was restored to the de-energized anodes. Therefore, the following corrective actions were planned:
.1 ) Restore voltage to the de-energized anodes.
- 2) Adjust the output voltage of the Rectifiers to approximately 75 volts.
- 3) Survey the areas to determine if adequate readings are being provided by the Test Stations.
- 4) Based on the findings in the previous step, evaluate the need for additional review / testing by Design Engineering and Ebasco Consultants.
Gn June 7, 1989, station NPD personnel began determining which underground power cables to the de-energized anode wells associated with Rectifier No. 3 (Unit 2 D/G Fuel Storage Tank Cathodic Protection) were cut.
It was determined that the cables to Anode Wells Nos. 9, 10, 11, 12, 13, 14, 16, and 18 had been cut.
Station personnel began temporarily restoring voltage to the above anode wells and verified that the output voltage of Rectifier No. 3 was approximately 75 volts. A survey of the area showed that restoring voltage to Anode Wells Nos. 14 and 9 brought the voltage reading on Test Station TS-19 to an acceptable level.
All other test stations associated with Rectifier No. 3 also read acceptable voltage levels.
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.On June 9, 1'989, station personnel began determining which underground power p
cables to the de-energized anode wells associated with Rectifier No. 7 (Unit 1 D/G Fuel Storage Tank Cathodic Protection) were cut.
It was determined that the cable to Anode Well No. 37 had been cut. On June 12, 1989, station NPD personnel temporarily restored voltage to Anode Well No.-37 which also restored voltage to Anode Wells Nos. 38, 39,,40, and 42 (Anode Wells Nos.'37 through 42 are connected in series). Station personnel then adjusted the output voltage of Rectifier No.
7 to approximately 75 volts and the system was allowed to stabilize for at 1 cast 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
On June 14 and-15, 1989, station-NPD and Design Engineering personnel surveyed the area covered by Rectifier No. 7.
The survey showed that Test Station TS-36 was reading an acceptable voltage level, but Test Stations TS-34 and TS-35 were still reading low. All other test stations associated with Rectifier No. 7 read acceptabic voltages. Above. ground voltage readings of the area around TS-34 and TS-35 were taken by Design Engineering personnel using a portable half cell and data was recorded. 'In addition, a second survey of the area associated with Rectifier No. 3 was performed and it was determined that it was'only necessary to restore power to Anode Well No. 14 in order to return the Unit 2 D/G Fuel Storage Tank Cathodic Protection portion of the system to operable status.
On June 20, 1989, temporary power cables were installed under Temporary Station Modification work requests to restore voltage to Anode Well No. 14 (Rectifier No.
- 3) and Anode Well No. 37 (Rectifier No. 7) until all of the cut cables can be l
repaired or replaced. After review of the data collected on June 14 and 15, Design Engineering personnel made the following observations:
1.
Above ground voltage readings recorded during the survey of the area around TS-34 and TS-35 were not consistent with the voltage readings read from TS-34 and TS-35.
Voltage readings taken on the surface were higher in value than voltages read on the two test stations. Voltage readings above ground are expected to be lower than readings underground near protected piping.
2.
Voltage measured on TS-34 and TS-35, are not consistent with voltage readings on TS-36.
Voltage readings on TS-36, which is in the same area as TS-34 and TS-35, show acceptable readings indicating adequate cathodic protection is being provided to the Unit 1 D/G Fuel Storage Tank piping.
Based on the above, Design Engineering personnel concluded that the low voltage readings on TS-34 and TS-35 are due to problems with the test stations' electrodes and recommended that the Cathodic Protection System be declared operable.
In addition, Design Engineering personnel recommended that Test Stations TS-34 and TS-35 not be used for fulfilling surveillance requirements as TS-36 is sufficient to monitor cathodic protection of the Unit 1 D/G Fuel Storage Tank piping.
I On. June 21, 1989, Test Stations TS-34 and TS-35 were deleted from the Cathodic J
Protection System surveillance procedure. The surveillance procedure was performed and all test stations met the acceptance criteria showing adequate protection to the Unit I and 2 D/G Fuel Storage Tanks and Piping. The Cathodic Protection System was then declared operabic.
J.
At present, the Unit 2 D/G Fuel Storage Tank Cathodic Protection System (Rectifier No. 3) is providing adequate protection with no immediate concerns.
The Unit 1 D/G Fuel Storage Tank Cathodic Protection System (Rectifier No. 7) is presently providing adequate protection, however, trending of the surveillance readings indicate that the anode wells associated with Rectifier No. 7 are deteriorating and may eventually be unable to provide adequate protection.
In addition, three test stations associated with Rectifier No. 7 have failed within the last two years. Station NPD and Design Engineering personnel are presently evaluating these problems. Preliminary discussions indicate the possible need to add additional anode wells and test stations to Rectifier No. 7 within the next year. Station NPD and Design Engineering personnel will continue to evaluate and initiate corrective action as necessary. This will include evaluating the need for testing by Ebasco Consultants.
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