ML13016A509
| ML13016A509 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 12/20/2012 |
| From: | - No Known Affiliation |
| To: | Division of License Renewal |
| References | |
| Download: ML13016A509 (7) | |
Text
Davis-BesseNPEm Resource From: dorts@firstenergycorp.com Sent: Thursday, December 20, 2012 2:04 PM To: CuadradoDeJesus, Samuel Cc: custerc@firstenergycorp.com
Subject:
FENOC Letter L-12-432 -- Supplemental Response to RAI B.2.2-3 Attachments: L-12-432 DOST Sealant Repair_2012-12-20.pdf Sam..... attached is a copy of FENOC letter L-12-432, providing a supplemental response to NRC request for additional information (RAI) B.2.2-3 related to the Aboveground Steel Tanks Inspection Program and the addition of sealant around the base of the Diesel Oil Storage Tank. The letter was sent today.
Should you have any questions regarding the attached, please contact me.
Thank you, Steve Dort Davis-Besse License Renewal
The information contained in this message is intended only for the personal and confidential use of the recipient(s) named above. If the reader of this message is not the intended recipient or an agent responsible for delivering it to the intended recipient, you are hereby notified that you have received this document in error and that any review, dissemination, distribution, or copying of this message is strictly prohibited. If you have received this communication in error, please notify us immediately, and delete the original message.
1
Hearing Identifier: Davis_BesseLicenseRenewal_Saf_NonPublic Email Number: 4002 Mail Envelope Properties (OFF004EBF9.7B7535B2-ON85257ADA.00684CB2-85257ADA.0068B51B)
Subject:
FENOC Letter L-12-432 -- Supplemental Response to RAI B.2.2-3 Sent Date: 12/20/2012 2:03:40 PM Received Date: 12/20/2012 2:04:19 PM From: dorts@firstenergycorp.com Created By: dorts@firstenergycorp.com Recipients:
"custerc@firstenergycorp.com" <custerc@firstenergycorp.com>
Tracking Status: None "CuadradoDeJesus, Samuel" <Samuel.CuadradoDeJesus@nrc.gov>
Tracking Status: None Post Office: FirstEnergyCorp.com Files Size Date & Time MESSAGE 1034 12/20/2012 2:04:19 PM L-12-432 DOST Sealant Repair_2012-12-20.pdf 61608 Options Priority: Standard Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:
Recipients Received:
Attachment L-12-432 Supplemental Reply to Request for Additional Information for the Review of the Davis-Besse Nuclear Power Station, Unit No. 1 (Davis-Besse),
License Renewal Application, Section B.2.2 Page 1 of 3 Supplemental Question RAI B.2.2-3 The NRC initiated a telephone conference call with FENOC on November 20, 2012, to discuss the condition of the diesel oil storage tank and the related FENOC response to NRC request for additional information (RAI) B.2.2-3 submitted by FENOC letter dated May 24, 2011 (ML11151A090). During a preventive maintenance task, it was discovered that there was no visible moisture barrier between the bottom of the diesel oil storage tank and the concrete support pad for the tank. Also, areas of corrosion were discovered on the horizontal flange at the bottom of the tank. The preventive maintenance task included an ultrasonic test (UT) examination of the tank bottom.
Following the discussion, both parties agreed that FENOC should submit a supplemental response to RAI B.2.2-3 to address the following items:
- 1. the as-found condition of the diesel oil storage tank;
- 2. that the condition was entered into the Corrective Action Program;
- 3. details of the UT examination and the results; and,
- 4. whether the design criteria for the tank was met, and if not, a justification as to why the condition of the tank is acceptable.
SUPPLEMENTAL RESPONSE RAI B.2.2-3
- 1. An external inspection of the diesel oil storage tank was performed by a tank inspection vendor during a periodic preventive maintenance task. The vendor performed the inspection using American Petroleum Institute (API) Standard 653, Tank Inspection, Repair, Alteration, and Reconstruction. The as-found condition of the exterior of the storage tank is summarized as follows:
x The concrete pad foundation was in serviceable condition with minor cracks observed throughout.
x No moisture barrier was observed between the tank horizontal bottom flange, which extends approximately 1-1/2 inches beyond the shell of the tank, and the concrete pad. Corrosion, including rust scale and minor pitting, was noted at the tank horizontal bottom flange to concrete pad interface. The vendor
Attachment L-12-432 Page 2 of 3 recommended cleaning, priming and recoating the areas of corrosion, and caulking or sealing the area between the bottom horizontal flange and concrete pad.
x The tank was sufficiently grounded.
x The tank shell showed minor corrosion on the first course near the bottom, but no bulging or distortions of the shell were identified. The tank coating (applied in 2006) was noted to be serviceable with no evidence of deterioration. UT thickness readings were taken on all three courses of the shell going up the vertical stairway; readings revealed no measured wall loss. No evidence of out of roundness was observed. Tank shell welds shows no evidence of corrosion to date.
x The fixed roof plates were free from corrosion. Roof plates and shell were free from significant distortion.
x Nozzles and flanges were in serviceable condition with no evidence of leakage noted. Nozzles had adequate reinforcement where required.
x The ladders, platforms, and handrails were in serviceable condition.
x No weld repairs were recommended as a result of the external visual inspection.
- 2. A Condition Report was written and entered into the FENOC Corrective Action Program to document two concerns related to the diesel oil storage tank external as-found condition:
x Contrary to the Davis-Besse design drawing, no moisture barrier was installed between the tank horizontal bottom flange and the concrete pad.
x The FENOC response to NRC RAI B.2.2-3 by letter dated May 24, 2011 (ML11151A090), which was based on the design drawing, stated that a sealant was installed between the tank and the foundation.
Further investigation revealed that FENOCs response to NRC RAI A.1.2-1 by letter dated July 22, 2011 (ML11208C274) also stated that a sealant was installed. On November 8, 2012, FENOC informed the NRC of the missing sealant at the base of the diesel oil storage tank and the discrepancy with the RAI responses.
A work order was created to install a moisture barrier at the base of the diesel oil storage tank. Sand blasting was performed on the tank bottom flange, bottom to shell weld, and the concrete pad around the flange to remove the corrosion from the tank flange and prepare the surfaces for priming. An industrial primer and joint
Attachment L-12-432 Page 3 of 3 sealant were applied according to the manufacturers instructions and FENOC procedures, coating the bottom to shell weld, the tank bottom flange, the gap between the tank bottom flange and the concrete pad, and the concrete pad several inches beyond the edge of the bottom flange. The sealant installation was completed on December 13, 2012.
Following the correction of the configuration control discrepancy by the installation of the moisture barrier between the diesel oil storage tank and the tank foundation, the FENOC responses to RAI B.2.2-3 by letter dated May 24, 2011 (ML11151A090),
and RAI A.1.2-1 by letter dated July 22, 2011 (ML11208C274), as described above, are complete and accurate.
- 3. An internal inspection of the diesel oil storage tank was also performed by the tank inspection vendor during the periodic preventive maintenance task. The vendor performed the inspection using American Petroleum Institute (API) Standard 653, Tank Inspection, Repair, Alteration, and Reconstruction. The storage tank was in service during the inspection. The purpose of the internal inspection was to measure the remaining bottom plate thickness of the diesel oil storage tank.
A robotic crawler with ultrasonic test (UT) probes was lowered into the diesel oil storage tank through the roof opening. Nine (9) UT runs of approximately 20 feet each were systematically taken of the tank bottom in a star pattern. Thickness measurements were taken continuously during the runs and fed into a computer for data capture and later evaluation. During the inspection approximately 345,000 data points were taken. All collected data was analyzed off site.
The nominal thickness of the diesel oil storage tank floor is 0.250 inches. The results of the UT readings showed that the average minimum measured bottom thickness was 0.247 inches. The minimum measured bottom thickness was 0.244 inches.
There were no runs where plate thinning of 10 percent or greater was observed during the inspection.
- 4. Based on the external and internal inspections of the diesel oil storage tank, the design criteria for the tank are met. The external visual inspection findings and external UT thickness readings taken on shell, nozzles, and roof plates demonstrates that the tank is suitable for continued service within the current operating parameters, with an estimated remaining life of greater than 20 years. The internal UT measurements of the bottom of the tank bottom plate were evaluated using an Extreme Value Analysis, which showed that the probability of the thickness of any portion of the bottom plate being less than 0.243 inches is less than one percent. The vendor concluded that the remaining life thickness of the tank bottom is greater than 20 years.