ML20248G372
| ML20248G372 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 09/29/1989 |
| From: | Croneberger D GENERAL PUBLIC UTILITIES CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 5000-89-1820, NUDOCS 8910100215 | |
| Download: ML20248G372 (3) | |
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GPU Nuclear Corporation f::
gg gf One Upper Pond Road Parsippany, New Jersey 07054 201-316-7000 TELEX 136-482 Writers Direct Dial Numbet September 29, 1989 U.S. Nuclear Regulatory Commission
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Attention: Document Control Desk Washington, D.C.
20555 Gentlemen.
Subject:
Oyster Creek Nuclear Generating Station (OCNGS)
Docket No. 50-219 License No. DPR-16 Oyster Creek Drywell Containment References (1) NRC Ltr. dated 8/10/88 (2) GPUN Ltr. 5000-88-1633, dated 9/12/88 (3) NRC Ltr. dated 10/26/88 (4) GPUN Ltr. 5000-89-1717, dated 2/9/89 (5) NRC Ltr. dated 4/28/89 In response to a request for supplemental information, GPU Nuclear submitted to the NRC staff the drywell inspection program for both a refueling outage and an outage of opportunity where a drywell entry is made. The NRC staff reviewed and concurred with this program for.the 12R outage (Ref. 3) and future outages of opportunity (Ref. 5).
Based on the results from the 12R UT inspections, GPUN will make a revision to this inspection program. First, GPU Nuclear will specify a minimum interval for inspections in order to limit the man-rem exposure. For example, the data collection.for a priority 1 area incurs a one man-rem exposure. Second, GPU Nuclear vill expand the areas for inspection to ascess the effectiveness of the cathodic protection system in the sand bed.
Cycle 12 is the first cycle where cathodic protection is in use.
We propose that priority 1 areas should not be inspected more frequently than about once every three months. We base this recommendation on the results of the statistical analysis (Ref. 4) used to determine a corrosion rate (See Table 1).
In our judgement, at least a 3 month interval between readings for priority 1 locations is required to detect a physically significant increase in the corrosion rate which was used to project drywell adequacy through June 1992. Likewise, an 18 month interval for priority 2 areas is adequate to detect changes in the corrosion rates which could impact the Safety Evaluation conclusions (Ref. 4) as no ongoing corrosion is apparent in these areas.
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GPU Nuclear Corporation is a subsidiary of General Public Utilities Corporation
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- Based.on these facts, GPUN has revised its drywellLinspection program to; specify the; minimum intervals. Also,.GPUN-will expand its UT data collection' (see Table 1) to provide' additional data to assess the' effectiveness of the cathodic, protection system.
If you have'any questions on this inspection.
program,;please contact Mr. Michael Laggart,1 Manager, BWR Licensing at ( 201)'
316-7968.
Ver t ly yours, j
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.',KIcroneberg Acting Director Technical Fune ions DKC/DJ/pa cc: Regional Administrator Region I
' U.S.' Nuclear Regulatory Commission 475 Allendale Road King of Prussia, PA 19406 Resident Inspector Oyster Creek Nuclear Generating Station Mr. Alex Dromerick U.S. Nuclear Regulatory Commission Mail Station PI-137 Washington, DC 20555 1.
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-TABLE'l' DRYWELL INSPECTION PROGRAM l
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.p PRIORITY *-
UT INSPECTION CORROSION RATE AREA ELEVATION fMPY)**
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'1j-11' 3"-
27.6'1 6.'1 Eleven 6" x 6", grids in.
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Bays;9, 11, 13,,15,.17, 19 and frame 17/19:
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.50'-2" 4.3 1 0.'03
'One 6" x 6" grid.above
' Bays 5 r
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87'-5" No ongoing Three 6" x 6" grids ~above corrosion' Bays 11 & 15:
'2.-
11'-3" No evidence of Eight strips ("1x6" significant reading 1" apart).in Bays L
corrosion 1, 3, 5, 7,'9, 13
- NOTES:
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Priority 1 areas: inspected at each outage of opportunity but 'not more frequently than once every three months.
Priority 2 areas inspected in an outage of_ opportunity if the previous set of. data was taken eighteen months or more before the outage.
- 1. MPY;= MiIs per. year.as of October 1988.
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