ML20005G748

Provides Currently Available Info Re Subj of in-core Instrumentation Thimble Thinning.Util Planning to Provide Requested Response to NRC Bulletin 88-009 Following Completion of First Refueling Outage

ML20005G748
Person / Time
Site:	Seabrook
Issue date:	01/11/1990
From:	Feigenbaum T PUBLIC SERVICE CO. OF NEW HAMPSHIRE
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
IEB-88-009, IEB-88-9, NYN-90010, NUDOCS 9001230028
Download: ML20005G748 (2)

Text

.

t '

v: y New Hompshire?

o m.,

Senior Vice President and '

Chief Operating Officer l

NYN-90010

)

January 11, 1990 United States Nuclear Regulatory Commission Washingtoni DC-20555 a

Attention: Document Control Desk i

References:

(a). Facility Operating License NPF-67,. Docket No. 50-443' l

(b) NRC Bulletin 88-09. dated' July 26, 1988, " Thimble Tube.

I L

l Thinning-in Westinghouse Reactors' i

Subject Information Regarding Incore Instrumentation Thimble Thinning' L

Gentlemen:

i This letter provides currently-available information regarding.the

(

subject of incore instrumentation ' thimble thinning as it' applies to Seabrook l

Station.

New Hampshire Yankee.(NHY) is planning to-provide the requested i

response to NRC Bulletin 88-09 following completion of the first). refueling i

outage of Seabrook Station Unit 1 in accordance with.the schedule specified i

by the Bulletin.

The Seabrook Station fixed / movable incore instrumentation system features a unique mechanical design which provides in-depth protection,against. reactor coolant leakage consequent to thimble wear. The'in-core instrumentation l

thimble contains fis:ed detectors. Consequently, the design Includes two concentric thimbles.

The inner thimble permits the moveable = detector'to l

traverse the core and serves as the reactor: coolant pressure-boundary.- The l

outer thimble serves as the housing for the fixed incore'detectoru and incore thermocouples, which are located between the inner and outer

~

thimbles.

Failure of the outer thimble would not breach the reactor coolant-pressure boundary.

Failure of both outer and inner thimbles would'be required to breach-the reactor coolant pressure' boundary. -In the.h_ighly s

unlikely event of a wear-induced failure of both inner and outer thimbles, isolation valves at the seal table can be used to terminate reactor = coolant leakage.

New Hampshire Yankee expects to develop.n inspection program to monitor thimble performance.

The program will 'e based, in part, upon industry experience and' vendor recommendations.

The program will'be-implemented at'

..I the first refueling outage of Seabrook Station Unit 1.

The report 6

confirming that the program has been established and that the initial thimble inspections have been performed in accordance with the requirements of the program will be submitted within thirty (30) days of completion of the inspections.

[

9001230028 900111 F

PDR ADOCK 05000443

/

Q PDC New Hampshire Yonkee Division of Public Service Company of New Hampshire (p

i P.O. Box 300

• Seabrook, NH 03874

• Telephone (603) 474 9521 -

I, United States. Nuclear Regulatory Commission January 11, 1990-Attention: Document Control Desk Page 2.

L If you have any questions on this matter please contact Mr. Geoffrey

[

Kingston at (603) 474-9521..

Very truly yours, h&f 4 L

Ted C. Feigenbaum j

cc:

Mr. William T. Russell l.

Regional Administrator l

United States Nuclear Regulatory Commission Region I l

475 Allendale Road l

King of Prussia, PA 19406 Mr. Victor Herses, Project Manager l

Project Directorate I-3 j

l United States Nuclear Regulatory Commission l

Division of Reactor Projects l

i Washington, DC 20555 l

NRC Senior Resident Inspector l

P.O. Box 1149 l

Seabrook, NH 03874 l

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