ML091480442
| ML091480442 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 11/30/2008 |
| From: | Conte R, Richmond J NRC Region 1 |
| To: | |
| References | |
| FOIA/PA-2009-0070 | |
| Download: ML091480442 (2) | |
Text
Preliminary Notification G:\\DRS\\Engineering Branch 1\\_LicRenewal\\Oyster Creek\\2008 Outage\\Backup\\OC PNO Nov-2008_Drywellrev-2.doc DCS No.: 0500021911 XX08 Date: November XX, 2008 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE PNO-1-08-XXX Facility Licensee Emergency Classification AmerGen Energy Company, LLC Notification of Unusual Event Oyster Creek Alert Forked River, New Jersey Site Area Emergency Docket: 50-219 General Emergen*8y.
X Not Applicable
Subject:
RESULTS OF IMPLEMENTATION OFCY*STER CREEK LICENSE RENEWAL COMMITMENTS RELATED TO THE PRIMARY CONTAINMENT( DRYWELL)
The NRC staff conducted an on-site inspection of AmerGen's *a.ct*ons related to license renewal commitments to be implemented during the 2008 refueing, outage at the Oyster Creek Nuclear Generating Station (OCNGS). In particular, the NRC review! involved a multi-week inspection of AmerGen's three aging management programs associatedwith the primary containment (drywell): Containment Metallic Liner Inservice Inspection; Structures Monitoring Program; and Protective Coating Monitoring and Maintenance Program. In accordance with the NRC's agreement with the State of New Jersey, State Engineers observd portions of the NRC staff review. Based on the results of the NRC's inspection activities to date, the NRC staff concluded there were no safety significant conditions with respect to the primary containment that would prohibit plant startup.
In the mid-I 980s, GPU Nuclear(previous licensee) ýidentified corrosion of the drywell containment steel shell, in the sand bed region. initial licensee actions were not effective in arresting corrosion. In 1992, all sand was removed from the sand bed region and the accessible exterior surfaces of the drywel shell were cleaned and coated with epoxy. Ultrasonic test (UT) thickness measuremnentsof the*drywell shell taken in 1992 and 1996 indicated the corrosion had been effectively arrested This information was confirmed by UT measurements in 2006, during a refueling outage.
On October-24, 2008, OCNGS shut down for a scheduled refueling and maintenance outage.
Outage work included implementation of various license renewal aging management programs.
During the 2008 refueling outage, the NRC's drywell shell inspection focused on:
- 1. Results of drywell shell UT thickness measurements.
- 2. Direct observation of drywell shell conditions both inside the drywell, including the floor trenches, and outside the drywell, in the sand bed regions.
- 3. Condition and integrity of the drywell shell epoxy coating, including AmerGen's activities to evaluate and repair four small coating blisters found in Bay-1 1.
- 4. Condition and integrity of the drywell shell moisture barrier seal between the shell and the sand bed floor, including AmerGen's activities to evaluate and repair identified cracks in moisture barrier seals in multiple sand bed bays, including a seal crack in Bay-3 which also exhibited small rust stains.
- 5. AmerGen's activities to monitor, evaluate, and mitigate water leakage from the reactor
Preliminary Notification refueling cavity onto the external surface of the drywell shell and into the sand bed regions.
With respect to AmerGen's implementation of license renewal commitments, the NRC staff has concluded:
- 1. All drywell shell UT thickness measurements satisfied AmerGen's acceptance criteria and current licensing basis design requirements.
- 2. There were no identified significant conditions affecting the drywell shell structural integrity.
- 3. The as-found condition of the external drywell shell epoxy coatingjin the sand bed regions, was acceptable, except for one small broken blister and three smallui nbroken blisters (initially described as surface bumps) that were found on the coating in Bay-1 1. The blisters were repaired. AmerGen reported that some blistering was*epcted and would be identified during routine visual examinations. The NRCO wlllt rview AmerGen's cause evaluation when it is complete.
- 4. The as-found condition of the external drywell shell Pisture barrier s.eal; between the shell and the sand bed floor, was acceptable, except fori mtiple surface cracO which did not appear to completely penetrate the seal. The identified seal cracks were repaired. During one crack repair, in Bay-3, some drywell shellsurface corrosion was identified ý,dd repaired.
- 5. AmerGen's activities to monitor and mitigate \\terJeakagemfrom the reactor reteling cavity onto the external surface of the drywell shell and~IbM'thefland bed regions were acceptable.
During the outage, water leakage from the' reactor refui avity cavity drain trough, as monitored in the trough's drain line, increased from less thari itgallon per minute (gpm) to approximately 5 gpm. Some spill-over from the ca'yjdrain trou..t r
resulted in water entry into the sand bed region. Am
,re rehnanVd its leakage monitoring and performed visual inspectionstto detect any waer enyVl
-uddleswere identified in several sand bed bays. After the cavity was drained, AmerGen performed direct inspections of the sand bed bays, and no adverse conditions were identified. To determine whether any increased drywell shell corrosion may have occurred as a result of this leakage, AmerGen has committed to perform UT thickness, measurements on the upper drywell shell during the next refueling outage (2010).
AmerGen, ln.iified'nd fixed th4e problems found in sand bed Bay-3 and Bay-i 1, as part of their aging marigement program imilmentation. The drywell shell epoxy coating and the moisture barrier eals, both in thosand befr6gion, are barrier systems used to protect the drywell shell from cr;bsion. The probleffs identifiedwith these barriers had a minimal impact on the drywell shell, andthe projected shell.*orrosion rate remains very small.
Based on a
- ,re'Aeof the teh rical information, the NRC staff determined AmerGen has provided an adequate bagis*Iregarding the primary containment (drywell), to restart OCNGS.
The State of New Jerserhas been notified.
This Preliminary Notification is being issued for information only and will not be updated.
ADAMS Accession Number: ML.....................
CONTACT:
Richard J. Conte John Richmond (nrc.gov (a.nrc.gov (610) 337-5183 (610) 337-5220