ML091480446
| ML091480446 | |
| 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: ML091480446 (3) | |
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l Preliminary Notification G:\\DRS\\Engineering Branch 1\\_LicRenewal\\Oyster Creek\\2008 Outage\\Backup\\OC PNO Nov-2008_Drywellrev-4.doc DCS No.: 0500021911XX08 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 vent Oyster Creek Alert Forked River, New Jersey Site Area Emergency.
Docket: 50-219 General Emergency X
Not Applicablt" Nqý,
n
Subject:
RESULTS OF IMPLEMENTATION OF OYSTER CREEK LICENSE RENEWAL COMMITMENTS RELATED TO THE DRYWELL PRIMARY CONTAINMENT The NRC staff is performing an inspection of AmerGen's action elated to license* renewal commitments, which were implemented during the 20A refueling outage at the Oyster Creek Nuclear Generating Station (OCNGS).,The NRC staff completed its on-site portion of a multi-week inspection of AmerGen's three aging*,anagement pro9grams associated with the drywell primary containment: Containment Metallic Liner Inservice I""o'ection; Structures Monitoring Program; and Protective Coating Monitoring andZMaintenancePogram.
In accordance with the NRC's agreement with the State of New Jersey, State.Engieers',ser portions of the NRC staff review. Based on the re~blts of the NRC's inspeetion activities to date, the NRC staff concluded there were no spafety sigificant conditions with res'pet to the drywell containment that would prohibit plant:startup.
In the mid-1 980s, G Nuclear (preibus licensee) identified corrosionof the drywell containment steel shelinthe sann d rege Initial licensee actions were not effective in arresting the-corrosion. 113119.9all sand s
ved from the sand bed region and the accessibleexte°riorsurlaces he drywell shell were cleaned and coated with epoxy. Ultrasonic test (UTIthickness measureme Vsof the drywell shell taken in 1992 and 1996 indicated the corrosion had been effecti\\tely arreste.d. This information was confirmed by UT measurements in 2006, during a refueling outage.
On October*"24,42008, OCNGshut down for a scheduled refueling and maintenance outage.
Outage work inleuded impleimpentation of various license renewal aging management programs.
During the 2008 relfueirnputage, 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 one small broken blister (with a small rust stain) and three small unbroken blisters (initially described as surface bumps) found in Bay-1 1, during the outage.
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 small cracks in moisture barrier seals in multiple sand bed bays, and a small seal crack in Bay-3 which also exhibited small rust stains.
Preliminary Notification
- 5. AmerGen's activities to monitor, evaluate, and mitigate water leakage from the reactor 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. AmerGen's inspection of the as-found condition of the external drj.ell shell epoxy coating, in the sand bed regions, was acceptable. Four small blisters on th*i6coating in Bay-11 were identified and repaired. AmerGen reported that some blistering:was expected, and would be identified during routine visual examinations. The NRC staff willreview AmerGen's cause evaluation after it is completed.
- 4. AmerGen's inspection of the as-found condition of the external dryell shell moisture barrier seal, between the shell and the sand bed floor, was acceptable. Surfac_ cracks, which did not appear to completely penetrate the seal, were identified in multiple bays'and were repaired. During one crack repair in Bay-3, some drywell shell surface corrosi on was also identified and repaired.
- 5. AmerGen's activities to monitor and mitigate waterleakage from the reactor refueling cavity onto the external surface of the drywell shell and into thstheand bed regions are still under evaluation.
During the outage, water leakage from the reactor*refueling cavity into the cavity drain trough, as monitored in the trough's drain line, increased from less.than 1 gallon per minute (gpm) to approximately 4 to 6 gpm. Some eof the water in the cavity drain trough spilled into the gap between the steel shell and.th.el Bcnrete shieldwalll, and ultimately into the sand bed regions.
AmerGen enhanced itsgleakage m_ itoring and performed visual inspections to detect any water entry. Water puddles ývere identified"in several san~d bed bays. After the cavity was drained, AmerGen performeddrject inspectifs* of the sand bed bays, and no significant adverse cnios nfie o dANer~ijne-whýether any increased drywell shell corrosion may conditions were identifil r'
N*
have occurred-as a result t iakage, ArG>'n stated they will perform UT thickness m
p
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'ell shell during the next refueling outage (2010).
AmerGeh identified andtfixed the* foblems found in sand bed Bay-3 and Bay-i 1, as part of their aging -anagement programmplemf.intation. The drywell shell epoxy coating and the moisture agn a'gm en I"V" barrier 9ý01' oth in the sanc~bed region, are-barrier systems used to protect the drywell shell from corrosion'., The problemsJidentified with these barriers had a minimal impact on the drywell steel shell and**ijhe projected Shell corrosion rate remains very small, as confirmed by NRC staff review of UT data Based on a review o*f the technical information, the NRC staff determined AmerGen has provided an adequate basis to conclude the drywell primary containment will remain operable during the period until the next scheduled examination.
The information presented herein has been discussed with AmerGen and is current as of November 17, at xxx p.m. The State of New Jersey has 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
¶ Preliminary Notification (c.nrc.Qov (610) 337-5183
- nrc.qov (610) 337-5220
)
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