ML091470372
| ML091470372 | |
| 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: ML091470372 (2) | |
Text
Preliminary Notification 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 Event Oyster Creek Alert Forked River, New Jersey Site Area Emergency Docket: 50-219 General Emergency X
Not Applicable
Subject:
RESULTS OF IMPLEMENTATION OF OYSTER CREEK LCQENSE RENEWAL COMMITMENTS RELATED TO THE PRIMARY CONTAINMENT (DRYWELL)
The NRC staff conducted an on-site inspection of AmerGen's actions related tolicense renewal commitments to be implemented during the 2008 refueling 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 associated with 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 observed portions of the NRC staff review. Based on the results of the NRC'sinspection:activities to date, the NRC staff concluded there were no safety significant conditions Withirespect to theiipi mary containment that would prohibit plant startup.
In the mid-1 980s, G:PU Nuclear (prdvious license'e) identified corrosion of the drywell containment steel sh'l!!in the sandted, region. Initial licensee actions were not effective in arresting corrosion. In 1992, all:sania**
fremovedrfrom the sand bed region and the accessible exterior surfaces of.the drywell shell were cleaned and coated with epoxy. Ultrasonic test (UT) thickness,,me'asurements of 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 pdtage, 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 refueling cavity onto the external surface of the drywell shell and into the sand bed regions.
V Preliminary Notification 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 coating, in the sand bed regions, was acceptable, except for one small broken blister and three small unbroken 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 expeted, and would be identified during routine visual examinations. The NRC staff wiuill review AmerGen s cause evaluation when it is complete.
- 4. The as-found condition of the external drywell shell moisture barrier seal, between the shell and the sand bed floor, was acceptable, except for multiple surface cracks, which did not appear to completely penetrate the seal. The identified seal cracks were repaired. During one crack repair, in Bay-3, some drywell shell surface corrosion was identified and repaired.
- 5. AmerGen's activities to monitor and mitigate water leakage from the reactor refueling cavity onto the external surface of the drywell shell and into the sandbed regions wer,&'acceptable.
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 5 gpm. Some spill-over fro* the cavity drain trough appeared to occur, which resulted in water entry into the sand bed region. 'Aý'erGen enhanced its leakage monitoring and performed visual inspections to detect any water entry.* Water puddles were identified in several sand bed bays. After the cavitywas drained, AmerGen performed direct inspections of the sand bed bays, and no adverseconditions 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 identified and fixed the problems foundrin sand bed Bay-3 and Bay-i 1, as part of their aging managementli'rograrý implementation. The drywell shell epoxy coating and the moisture barrier*seals, both in th* sand beqdregion, are barrier systems used to protect the drywell shell fromiborrosion. The problems idenitified with these barriers had a minimal impact on the drywell shell, and the projected shellcorrosion rate remains very small.
Based on a =review of the technical information, the NRC staff determined AmerGen has provided an adequate basis regarding the primary containment (drywell), to restart OCNGS.
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
(@nrc.gov (nrc.gov (610) 337-5183 (610) 337-5220