ML20078D553
| ML20078D553 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 11/03/1994 |
| From: | Keaten R GENERAL PUBLIC UTILITIES CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 5000-94-0046, 5000-94-46, C321-94-2171, GL-94-03, GL-94-3, NUDOCS 9411040283 | |
| Download: ML20078D553 (5) | |
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Never.ber 3, 1994 5000-94-0046 C321-94-2171 U. S. Nuclear Regulatory Commission Att: Document Control Desk Washington, DC 20555
Dear Sir:
SUBJECT:
Oyster Creek Nuclear Generating Station (OCNGS)
Docket No. 50-219 Inspection Results for Oyster Creek Core Shroud Oyster Creek Nuclear Generating Station started its 15th refueling outage (15R) on September 10, 1994.
This is Oyster Creek's first refueling outage subsequent to the issuance of Generic Letter (GL) 94-03.
In accordance with the GL, Oyster Creek inspected its core shroud.
Numerous equipment and access problems were encountered during the course of the inspection.
GPU Nuclear informed the NRC staff of these situations by ccnference call as they emerged.
While most welds were free of any significant indications, weld H4 did have crack indications in a number of places.
Extensive additional inspection may have provided sufficient information to determine analytically that there was sufficient ligament for one or more cycles of operation.
Considering cost, schedule and the impact upon future outages it was decided that installation of the shroud enhancement was warranted.
After that decision was made, additional inspections of H4 were terminated.
In compliance with the GL, attached to this letter is a' report which conveys the scope, methodology and the results of the inspection.
The formal records and video tapes are located at the site and are available for NRC inspection at any time.
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C321-94-2171 Page 2 If you have any questions or require additional information, please contact Pr. Michael Laggart of GPU Nuclear Corporate Licensing (201) 316-7968.
Sincerely,/
bf.bdA R. W. Keaten Vice' President and Director Technical Functions RWK/DK/plo cc: Administrator, Region I Oyster Creek NRC Project Manager Senior Residen; Inspector, OC l
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.c.n 0YSTER CREEK CORE SHROUD INSPECTION ABSTRACl Durirg the 1994 Refueling Outage (15R) at Oyster Creek Nuclear Generating Station, an augmented inspection program was implemented for the core shroud.
The core shroud is a stainless steel cylindrical assembly that provirias a.
partition between the core region and the downcomer annulus to~ separate the' downward finw from the upward flow throu0h the core. The core shroud provides support for the top guide, and core spray assenbly. The shroud includes 10 l
welds labeled H1 to H9 (H6 is two welds, H6A & H68); and 36 conical supports'-
which span welds H7 and H8. A combination of ultrasonic and/or visual inspections woro performed on H1, H2, H3, H4, H5, H6A, H6B, H9, and 30 brackets. Cracks were detected on H2, H3, H4, H6A, ard H6B. A linear indication was found above one bracket (label ll2).
i I-Introduction The augmented inspections of the shroud. utilized the raethodology of the BWb VIP inspection documents for visual and ultrasonic examinations.
Prior to the inspections, the_ GPU Nuclear visual level III atterided the Ve>>el Internals Prcgran shroud training course at the EPRI NDE Center.
In addition, the GPU Nuclear visual level III tundutled a Lrdinifig class for all individucis i
perforning the visual inspections. A 1/2 mil wire standard was used when visual inwections were perfurmed on the shroud welds and-b'ackets. Cleaning of the surfaces was performed prior to visual inspections.
The ultrasonic inspections were perforned using the outside diameter (0.0.)
tret.Ler and/or. suction cup scanner (H3 was examir.ed from the ID).
The system i
used to collect data was GE's Smart 2000.
Personnel were qualified / certified i
to level II and III. Data evaluation was performed at a GE remote location at l
the EPRI center in Charlotte, N.C.
The ultrasonic technique employed a 45' Shear, 60* Longitudinal, and a 80' Longitudinal (creeping wave for surface and near surface flaws).
i All inspection results have been reviewed by GPU Nuclear's' level III in both l
visual and ultrascnics.
The following is a summary of the' results of the i
L shroud inspections, i
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WELD I.D.
INSPECTION TOTAL AREA RESULTS METHO,D.. -..
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m H1 UT (0.0.
81.64" or 13.75% of No cracks detected.
Tracker) total ci rcumfe re n_c e.
H2 UT (0.0.
161.93" or 27.27%
6 cracks, I.D. - for Tracker) of total total length of 19.33" 1 circumference.
crack, 0.D. - length -
8.86".
l H3 VT 107" of total 4 approxinatly equally i
circumference.
spaced areas from I.D. -
Total length 9 0 - 15"
@ Approx. 90 = 18" G Approx. 180' - 22"
@ Approx., 300* - 18" Two cretks were located
@ 90* approx. = 6" long and @ 250' = 28" icng.
H3 UT (suction cup 64.34" or 11.64% of No cracks detected, scanner,I.D.)
total Note: Total length circumference.
scarned showed.a lack of l
fusion indication.
The EFRI HDE Center-concurred with GE's disposition.
H4 UT (0.D.
276.5" or 49% of 21 cracks indicated.
tracker) total Upper side of weld ID circumference.
- 63.19" total
- Lower side of weld 00
- 137.99" total
- Lower side of weld ID
- 173" total l
H5 UT (0.D.
237" or 42% of No cracks recorded.
l tracker) total I
circumference.
H6A UT (0.0.
250" or 44.56% of.
9 surface indications tracker &
total recorded.
suction cup circumference.
scanner 0.D.)
H68 UT (0.D.
216.91" or 30.57%
2 surface indications tracker &
of total recorded.
suction cup circumference.
scanter 0.D.)
H9 Visual 4 equally spaced No cracks detected.
areas of 56* for total of 224" Brackets Visual 30 brackets 29 with no relevent I
indications 1 bracket (#2) has a linear indication.
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l NOTE There are 36 brackets which span H7 and H8.
A tctal of 10 were inspected. The results are listed on the previous page. Tne following are the ident ifications givnn to the brackets inspected Tney are numbered 1 36 ard start ct 0 RPV and 90 clockwise to 2, 3, etc.
Inspected:
1, 2, 3, 4, 5, 6, 8, 9, 10, 11, 12, 13, 14, 15, 17, 18, 20 j
21, 2 2, 2 3, 24, 26, 27, 28, 29, 30, 3 2, 33, 35 and 36.
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TOTAL P.06
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