ML091480443
| ML091480443 | |
| 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: ML091480443 (2) | |
Text
V Preliminary Notification G:\\DRS\\Engineering Branch 1\\_LicRenewal\\Oyster Creek\\2008 Outage\\Backup\\OC PNO Nov-2008_Drywellrev-3.doc DCS No.: 0500021911XX08 Date: November XX, 2008 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE PNO-1-08-XXX Facility Licensee Emeraencv Classification AmerGen Energy Company, LLC Oyster Creek Forked River, New Jersey Docket: 50-219 Notification of Unusual Event Alert Site Area Emergency N
General Emergen6y X
Not Applicable b,
Subject:
RESULTS OF IMPLEMENTATION OF OYSTER CREEK IJCENSE RENEWAL COMMITMENTS RELATED TO THE DRYWELL PRIMARY\\CONTAINMENT The NRC staff is performing an inspection of AmerGen's actions related to license renewal commitments, which were implemented during the 2008 refueling outage at the Oyster Creek Nuclear Generating Station (OCNGS). The NRC staff compled its on-site portion of a multi-week inspection of AmerGen's three aging management programs associated with the drywell primary containment: Containment MetallicLiner Inservice *nspection; Structures Monitoring Program; and Protective Coating Monitorng and >Maintenance Program. In accordance with the NRC's agreement with the State of New Jersey, State Engineers observed portions of the NRC staff review. Based on the results of the r4RC's inspecptionactivities to date, the NRC staff concluded there were no safitysignificant,onditions with-respect t' the drywell containment that would prohibit plant*st p"ar.u' In the mid-1 980s, GP, Nuclear (prvifus licens. ) identified corrosion of the drywell containment steel shell, in the sand d region. Initial licensee actions were not effective in arresting the corrosion. lb, 199 g 1 em from the sand bed region and the accessible exteorsurfa e
- f.
dwe e....re cleaned and coated with epoxy. Ultrasonic test (UT). Hknsseasureme ts of the drywellshell taken in 1992 and 1996 indicated the corrosiorfhad been effc*tively affested. This information was confirmed by UT measurements onin c06, during a refuel inhg'ou tage-q, 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 2008Tfueling oitage, 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.
- 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. AmerGen's inspection of the as-found condition of the external drywell shell epoxy coating, in the sand bed regions, was acceptable. Four small blisters on thecoating in Bay-1 1 were identified and repaired. AmerGen reported that some blistering was expected, and would be identified during routine visual examinations. The NRC staff will review AmerGen's cause evaluation after it is completed.
- 4. AmerGen's inspection of the as-found condition of the extrnal dqrywel11 shell moisture barrier seal, between the shell and the sand bed floor, was*Ab.eptable. Surface 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, somie drywell shell surface corrosion was also identified and repaired.
- 5. AmerGen's activities to monitor and mitigate water leakagefr4om the reactor refueling cavity onto the external surface of the drywell shell andrnt tthe snd bed regions are still under evaluation.
During the outage, water leakage fromthe\\ reactor refueling cavity into the cavity drain trough, as monitored in the trough's drain line, increased frooniless than 1&gallon per minute (gpm) to approximately 5 gpm. Some of the Water in the cavitydra!in trough spilled into the gap between the steel shell and the concretek.hield wall, and ulti*'t'l:*ainto>the sand bed regions. AmerGen enhanced its leakage mohi tori rad performed visual inspecti*ns to detect any water entry.
Water puddles were idhinfied e
seral sandd beays. After the cavity was drained, AmerGen performed direct insp ptions of the sand bed bays-,and no significant adverse conditions were identified. To determ 8whether a', increased dry'Well shell corrosion may have occurred as a result of this leakage, AnrerGeno teI the'-will perform UT thickness measurements on the upper drywe!.-sh.ell during thenxt refueling outae (2010).
AmerGein identified and fixed th'evproblems found in sand bed Bay-3 and Bay-1 1, as part of their Amirmp lemsntaion aging aianagement program,m ientation. The drywell shell epoxy coating and the moisture barrier
~
al, both in the saiVd, bed reg,, are barrier systems used to protect the drywell shell from co roion. The problem.s identified with these barriers had a minimal impact on the drywell steel shell b" the projected sh'ell corrosion rate remains very small, as confirmed by NRC staff review of U-'dataa.
Based on a review bf the technical information, the NRC staff determined AmerGen has provided an adequate basis to conclude the drywell primary containment is operable.
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 (a-nrc.gov
(@-nrc.gov (610) 337-5183 (610) 337-5220