ML091470369

Draft Preliminary Notification of Event of Unusual Occurrence, PNO-1-08-XXX, Facility Amergen Energy Company, LLC, Oyster Creek, Subject - Results of Implementation of Oyster Creek Renewal Commitments Related to the Drywall Primary Containm

ML091470369
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: ML091470369 (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 LICENSE 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 completedilits on-site portion of a multi-week inspection of AmerGen's three aging management pr~ rs associated with the drywell primary containment: Containment Metallic Liner Inservice'hIspection; Structures Monitoring Program; and Protective Coating Monitoring and Maintena'nce 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's ins pection activities to date, the NRC staff concluded there were no safety significant, conditions with respect to the drywell containment that would prohibit plant startup.

In the mid-1980s, GPU Nuclear (previous licensee) identified corrosion of the drywell containment steel shell, in the sand bed region. Initial licensee actions were not effective in arresting the corrosion. In 1992, all sand was removed from the sand bed region and. the.

accessible exterior surfaces of the drywell shell werlecleaned and coated with epoxy:. Ultrasonic test (UT) thicknessmeasurements 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 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 one small broken blister (with a small rust stain) and three small unbroken blisters (initially described as surface bumps) found in Bay-11, 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 refueling cavity onto the external surface of the drywell shell and into the sand bed regions.

A 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. 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 the coating 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 external drywell shell moisture barrier seal, between the shell and the sand bed floor, was acceptable. 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, some dywell shell surface corrosion was also 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 san d 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 5 gpm. Some of the water, in thebcavitydrain trough spilled into the gap between the steel shell and the concrete shield wall~liland ultimatelyrinto theblsand bed regions. AmerGen enhanced its leakage monitoring and perforfined visual ins*ictionsto detect any water entry.

Water puddles were identified in several sand.,bed bays. Afterthe cavity was drained, AmerGen performed direct inspections of the sand bed bays, and no significant adverse conditions were identified. To determine whether any increased drywell shell corrosion may have occurred as a result of this leakage, AmerGen stated they will perform UT thickness measurements on the upper drywell shell during the next refueling outage (2010).

AmerGen identified and fixed the problems found in sand bed Bay-3 and Bay-1 1, as part of their aging management program implementation. The drywell shell epoxy coating and the moisture barrier seal, both in the sand. bed region, are barrier systems used to protect the drywell shell from corrosion. The problems identified with these barriers had a minimal impact on the drywell steel shell and the projected shell corrosion rate remains very small, as confirmed by NRC staff review of UT data.

Based on a review of 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 hasbeen 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