ML20005G748
| 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 -
o . New Hompshire? 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 L
(b) NRC Bulletin 88-09 . dated' July 26, 1988, " Thimble Tube. I 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 i
response to NRC Bulletin 88-09 following completion of the first). refueling 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 s
- . required to breach-the reactor coolant pressure' boundary. -In the.h_ighly 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 l
Division of Reactor Projects ;
i Washington, DC 20555 !
l NRC Senior Resident Inspector l P.O. Box 1149 l Seabrook, NH 03874 l >
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