ML20205L062

Discusses Results of Review of Info Re Corrosion of Plant Drywell Containment,Per Util 871120,880425 & 0912 Ltrs. Commitment to Provide Assessment of Corrosion Rate at Each Refueling Outage Acceptable

ML20205L062
Person / Time
Site:	Oyster Creek
Issue date:	10/26/1988
From:	Dromerick A Office of Nuclear Reactor Regulation
To:	Fitzpatrick E GENERAL PUBLIC UTILITIES CORP.
References
TAC-65448, NUDOCS 8811010459
Download: ML20205L062 (5)

Text

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. 8 o NUCLEAR REGULATORY COMMISSION B :j W ASHINGTON, D. C. 20555

\*****/ OCT 2 61988 Docket No. 50-219 Mr. E. E. Fitzpatrick Vice President and Director Oyster Creek Nuclear Generating Station Post Office Box 388 Forked River, New Jersey 08731

SUBJECT:

OYSTER CREEK DRYWELL CONTAINMENT (TAC NO. 65448)

By letters dated November 20, 1987 April 25, 1988 and September 12, 1988, GFU Nuclear Corporation (GPUN/ licensee) submitted information regarding corrosion of the Oyster Creek Nuclear Generating Station drywell containnent. The inforna-tion contained in your letter of Apria 25, 1988 on upper drp ell analysis is basically the sane as that contained in your letter of November 20, 1987. The staff has reviewed the inforsation provided by GPUN and the results of our review are presented below.

By using a uniform thickness of 0.59" GPUN found that the hoop stress in a 40" long section of the cylinder near elevation 75' - 0" is 20,806 psi. This exceeds the ASME code allowable of 19,250 psi for general primary membrane stress by 8.5% but nearly equals the allowable stress based on certified material test report (CMTR) values. The licensee concluded that the drywell was proven structurally adequate in spite of the deviation froni the design provisions of the ASPE Code because:

1. The uniform model thickness which is the thinnest as measured does not duplicate the actual local areas of degradation and r:ay over-estimate the actual stress.

2. The ASPE Code allowable stresses are intended for new construction.

3. The ASME Code allowable stresses are based on specified minimum mechanical properties rather than actual material properties.

4 The calculated stress only reduced the code factor of safety from 3.64 to 3.37.

The staff concerns regarding the justification given above are as follows:

1. There are no ultrasonic test (UT) thickress reasurenents at or near elevation 75' - 0". The UT measurecents were made at elevation 87' - 05".

Whether UT reasurenents at this latter elevation are representative of the cylinder analyzed is unknown.

8811010459 881026 PDR ADOCK 05000219 / \

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. Mr. E. E. Fitzpatrick 2. It is not certain whether the CVTRs cover the material used in the region for which the analysis was made.

3. The factor of safety as provided by the code is to take care of various uncertainties in material properties, loadings and construction, and therefore should be maintained.

4. There is no assurance that further corrosion will not occur in the region.

In order to alleviate staff's concerns, it was initially detertnined that the following actions are necessary on the part of GPUN:

1. The licensee should consnit to perfortn UT thickness measurenents of the drywell shell including the area at or near elevation 75' - 0" at future outages of opportunity including forced outages.

7. The licensee shall provide for staff review and approval, its plan to perfonn UT examination.

A meeting between the licensee and the NRC staff was held on July 28,1988, at -

One White Flint North, Rockville, MD, to discuss staff's concerns and requirements. In the meeting GPUN reiterated its position and felt that staff's '

concerns and requirenents as stated above are unwarrented. GPUN made a detailed presentation which is sumarized as follows:

1. Most of the corrosion of the drywell portion above the sand cushion region occurred before operation, that is, during the erection stage.

The corrosten envirorcent is ger.erally the same at all elevations above the sand cushion and there is no evidence that significant differences in wall thinning should exist from one elevation to any other.

2. UT measured thickness of pitted areas at elevations 50' - 2" and 87' - 5" and the conservatively estimated corrosion rates were applied to the entire region above the sand cushion in the structural evaluation.

3. In order to perform UT thickness measurement at elevation 75'- 0" scaffolding tower erection and take-down will be involved thus subjecting personnel to an additional exposure of 10 man-rem which is not in conforwance with ALARA.

4. CMTRs cover the plate raterial used in the cylinder.

After reviewing the detailed information presented at the n>eeting, the staff has a better understanding of the issue and cores to the conclusion that in order to assure the drywell integrity the following requirenents are to be fulfilled by the licensee:

1. GPUN should formalize the drywell inspection program and be specific as to what is planned for the refueling outages and what is planned for targets of opportunity outages.

. Mr. E. E. Fitzpatrick 2. Document the basis for not inspecting the drywell at the 75'- 0" elevation.

3. Comit to prnvide an assessment of corrosion rate at each refueling outage.

The above requirements were conveyed to GPUN at the meeting and GPUN's consnitment to these requirements has been provided in a letter from GPUN to NRC dated September 12, 1988. The staff has reviewed the infomation and found the comitment contained therein to be acceptable.

Sincerely, s hg;rgh; $ &t* <6 M.

exMder W. Dromerick, Project Manager Project Directorate I-4 Division of Reactor Projects I/II Office of Nuclear Reactor Regulation ec: See next page i

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, Mr. E. E. Fitzpatrick Oyster Creek Nuclear Oyster Creek Nuclear Generating Station Generating Station ec:-

Ernest L. Blake, Jr. Resident inspector Shaw, Pittman, Pctts and Trowbridge c/o U.S. NRC 2300 N Street, h4 Post Office Fox 445 Washington, D.C. 20037 Forked River, New Jersey 08731 J.B. Liberman, Esquire Con:issioner Bishop,.Liberman, Cook, et al. New Jersey Department of Energy 1155 Avenue of the Americas 101 Connerce Street New York, New York 10036 Newark, New Jersey 07102 Mr. David M. Scott, Chief Regional Administrator, Region I Bureau of Nuclear Engineering U.S. Nuclear Regulatory Connission Department of Environmental Protection 475 Allendale Road CN 411 King of Prussia, Pennsylvania 19406 Trenton, New Jersey 08625 BWR Licensing Manager GPU Nuclear Corporation 1 Upper Pond Road Parsippany, New Jersey 07054 Deputy Attorney General i State of New Jersey Department of Law and Public Safety 36 West State Street - CN 112 Trenton, New Jersey 08625 Mayor l Lacey Township 818 West Lacey Road

Forked River, New Jersey 08731 Licensing Manager Oyster Creek Nuclear Generating Station Mail Stop

Site Emergency Bldg.

P. O. Box 388 Forked River, New Jersey 08731 l

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Nr.E.E.Fitzpatrick 3-

2. Document the basis for not inspecting the drywell at the 75'- 0" elevation.

3. Comit to provide an assessinent of corrosion rate at each refueling outage.

The above requiretrents were conveyed to GPUN at the neeting and GPUN's conenitnent to these requirerrents has been provided in a letter from GPUN to NRC dated Septec:ber 12, 1988. The staff has reviewed the infortnation and found the contattroent contained therein to be acceptable.

Sincerely, 4

Alexander W. Drceerick, Project Panager Project Directorate I-4 Division of Reactor Projects I/II l Office of Nuclear Reactor Regulation cc: See next page i DISTRIBUTION l "' Docket Fil E m

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