ML20092H197
| ML20092H197 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 09/15/1995 |
| From: | Keaten R GENERAL PUBLIC UTILITIES CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 5000-95-0088, 5000-95-88, C321-95-2235, NUDOCS 9509200308 | |
| Download: ML20092H197 (3) | |
Text
GPU Nuclear Corporation heye One Upper Pond Road
'4' EwEEuu Parsippany, New Jersey 07054 201-316-7000 TELEX 13G-482 Wnter's Direct Dial Number.
September 15, 1995 C321-95-2235 5000-95-0088 U. S. Nuclear Regulatory Cornmission Att: Document Control Desk Washington, DC 20555 Gentlemen:
Subject:
Oyster Creek Nuclear Generating Station (OCNGS)
Docket No. 50-219 Facility Operating License No. DPR-16 Drywell Corrosion Monitoring Program
References:
(1)
GPU Nuclear Letter C321-92-2163, " Oyster Cree'k Drywell Containment," May 26, 1992.
(2)
NRC Letter dated June 30,1992, " Oyster Creek Drywell Containment."
(3)
GPU Nuclear Letter C321-93-2100, " Oyster Creek Drywell Inspection," March 25, 1993.
In compliance with item (3) of References 1 and 2, and Reference 3, GPU Nuclear has (1) assessed the condition of the drywell based upon inspections performed at Oyster Creek during the 15R Outage and is (2) submitting an extended drywell inspection plan for the remaining life of the plant. GPU Nuclear remains committed, as stated in Reference 1, to continue taking drywell thickness measurements for the life of the plant.
$a.
Through the 15R Outage, GPU Nuclear's drywell containment vessel thickness monitoring W
program, item (2) of References 1 and 2, consisted of ultrasonic thickness (UT)
$8 measurements taken at the sandbed region and upper elevations (cylinder, sphere) of the pg drywell during refueling outages and other outages of opportunity.
mx og Assessment of the most recent UT data taken during the 15R Outage has determined that g
there is no evidence of ongoing corrosion in the upper elevations of the drywell and that corrosion has been arrested in the sandbed region of the drywell which was cleaned of sand g.
and rust and coated during the 14R Outage (December 1992). The attached table n.o summarizes the 15R Outage UT inspection results for both the sandbed region and upper GPU Nuclear Corporation is a subsidiary of General Pubhc Utihties Corporation
C321-95-2235 -
i, Page 2 i
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surfaces indicates that, after 21 months of service, the coating is performing satisfactory with no signs of deterioration such as blisters, flakes, discoloration, etc.
}
GPU Nuclear's extended inspection plan for the Oyster Creek drywell containment vessel covers both the upper elevations of the drywell and the coated sandbed region.
i For the upper elevations of the drywell, this program will perform UT measurements during the 16R Outage (currently scheduled to begin September,1996) and, as a minimum, again 1
during every other refueling outage (18R,20R, etc.). The UT measurement locations will be j
the nine areas identified as most severely corroded. Assessment of the most recent UT data 1
taken during the 15R Outage has determined (and will be reconfirmed by the 16R I
inspections) that there is no evidence of 6ngoing corrosion in the upper elevations of the drywell. After each inspection, a technical assessment of the drywell condition will be made, any appropriate corrective action will be taken, and any necessary additional inspections would be scheduled to ensure that drywell integrity is maintained for the remaining life of the plant.
l For the sandbed region of the drywell, this program will perform visual inspection of the external epoxy coating during the 16R Outage and, as a minimum, again during the 18R Outage (year 2000). The epoxy coating has an estimated life of 8-10 years which makes the current projected end of life between December,2000 and December,2002. Coating inspection shall be by direct (physical) and/or remote methods on a sample basis. Based i
upon these inspections, a technical assessment of the coating condition will be made, any 1
5 appropriate corrective action will be taken, and the need for additional (post 18R) inspections i
will be determined to ensure that drywell integrity is maintained for the remaining life of the j
plant. In addition, while not technically required based upon the performance of the epoxy coating, UT thickness measurements will be taken one more time in the sandbed region during the 16R Outage, to the same extent as the 15R Outage inspections.
j i
In compliance with Reference 3, GPU Nuclear remains committed to inform the NRC prior to implementing any changes to this drywell mspection program.
l i
Very truly yours,
[ Vice President and Director l
R. W. Keaten Technical Functions Attachment RTZ/ pip c:
Administrator, Region 1 Senior Resident Inspector j
Oyster Creek NRC Project Manager 4
4
4 i
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TABLE 1 ACCEPTABLE MEAN DRYWELL THICKNESSES ISR OUTAGE INSPECTION DRYWELL TIIICKNESSES UT CODE LOCATION NOMINAL MEASURED REQUIRED MARGIN MINIMUMS (1)
Sandbed Region 1.154" 0.806"
.736" (2)
.070" (3)
Sphere (el. 50' - 2")
0.770" 0.733" 0.541" 0.192" Sphere (el. 51' - 10")
0.722" 0.695" 0.518" 0.177" Sphere (el. 60' - 11")
0.722" 0.709" 0.518" 0.191" Cylinder (el. 87' - 5")
0.640" 0.613" 0.452" 0.161" (1)
Thinnest Location as measured during the 15R outage, September,1994.
(2)
Controlled by buckling, j
(3)
Corrosion arrested (sandbed region coated in 14R outage).
.