ML20214A032
| ML20214A032 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 05/12/1987 |
| From: | Kuncl L NEBRASKA PUBLIC POWER DISTRICT |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| CNS877236, GL-87-05, GL-87-5, NUDOCS 8705190213 | |
| Download: ML20214A032 (4) | |
Text
Nebraska Public Power District
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C N S S877236 May 12,1987 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C.
20555
Subject:
NPPD Response to Generic Letter 87-05 Gentlemen:
Pursuant to your request for additional information contained in Generic Letter 87-05, the following information is provided for Cooper Nuclear Station:
All Mark I Owners 1.
f rovide a discussion of your current program and any future plans for determining if the drain lines that were provided at your facility for removing any leakage that may result from refueling or from spillage of water into the gap between the drywell and the surrounding concrete or from the sand cushion itself are unplugged and functioning as designed.
NPPD Response NPPD does not have a program to verify that the subject drain lines are unplugged and are functioning properly.
Such testing would be difficult because the drain lines were not originally constructed to facilitate periodic testing.
However, any leakage past the reactor well seal and/or reactor wall liner is indicated by Flow Indicating Switch FPC-FIS-64.
This indicating switch, which is set to trip and alarm at 5 gpm, is observed once per shift by station operators when the reactor well is flooded.
Additionally, this switch is periodically removed and calibrated to verify operability.
NPPD will continue to perform this inspection, as well as implement new surveillance measures for inspecting the sand cushion drains for signs of leakage during refueling outages.
NPPD feels that these measures are adequate to detect any leakage which may occur.
2.
Provide a discussion of preventive maintenance and inspection activities that are currently performed or are planned to minimize the possibility of leakage from the refueling cavity past the various seals and gaskets that might be present.
ON 8705190213 870512 PDR ADOCK 05000298 s lj P
F-s U.S. Nuclear Regulatory Cocaission May 12,1987 Page 2 NPPD Response At Cooper Station, all reactor well drains are welded and do not use seals or gaskets.
Due to limited access, no visual inspection of the drywell to reactor well bellows is performed.
Based on the leak detection measures discussed in the response to the previous question, no other preventive maintenance and inspection activities are planned.
3.
Confirm the information listed in Table 1 is correct with regard to your facility.
NPPD Response See Attachment A for revised Table 1 information for Cooper Nuclear Station.
Mark I Owners Whose Designs Are Such That The Sand Cushion Is Open To Gap Between The Drywell Shell And Surrounding Concrete.
I 1.
Provide any plans for performing ultrasonic thickness measurements of the drywell shell plates adjacent to the sand cushion or any other proposed actions to ascertain if plate degradation has occurred.
Since the degradation that has occurred at Oyster Creek is localized, sufficient details should be included to show that the sampling basis for ultrasonic thickness measurements is adequate in terms of size and test location.
NPPD Response Due to the inaccessibility of the drywell shell area of interest, the traditional UT method did not provide meaningful results.
NPPD is considering a specialized method of ultrasonically examining the drywell shell in the sand pocket area (and thus, below the concrete drywell floor).
However, because this specific problem of accessibility is common to other BWRs, NPPD will pursue resolution of the problem through the BWR Owners Group or through a joint utility effort.
If an acceptable method of ultrasonic examination can be established through these efforts, a sampling basis which will detect localized degradation will be formulated and im plemented.
Sinc rely, j
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) ',& w u L. G. K u cl Vice President-Nuclear LGK:SSF:ss cc:
N RC Regional Office Region IV NRC Resident Inspector Cooper Nuclear Station
, U.S. Nuciscr Ragu1= tory Commission M:y 12, 1987 Peg 2 3 STATE OF NEBRASKA)
)ss PLATTE COUNTY
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L. G. Kunct, being first duly sworn, deposes and says that he is an authorized representative of the Nebraska Public Power District, a public corporation and political subdivision of th estate of Nebraska; that he is duly authorized to submit this request on behalf of Nebraska Public Power District; and that the statements contained herein are true to the best of his knowledge and belief.
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} L. G. Kuitel Subscribed in my presence and sworn to before me this d day of Tan 1987.
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C C NS S877236 Att:chcant A Page 1 of 1 REVISED TABLE 1 RESULTS OF MARK I CONTAINMENT SURVEY UT SAND WALL METHOD /
WAS GAP THICK RESULTS THE DETAIL UT SENT GAP PLANT NAME DKW.
PER-TO GAP MATERIAL (A/E)
AVAIL.
FORMED NRC MATERIAL REMOVED COMMENTS Ccoper (Burns & Roe) yes yes yes Polyurethane
- 1) Cap not sealed
- 2) UT not meaningful (Original construction contract documents indicate that polyurethane foam strips were placed ct concrete construction joints in the gap between the drywell shell and the surrounding concrete during plant construction. NPfD will attempt to verify this arrangement during the Spring 1988 Refueling Outage.
- -