ML18082B113
| ML18082B113 | |
| Person / Time | |
|---|---|
| Site: | Salem  |
| Issue date: | 07/22/1980 |
| From: | Varga S Office of Nuclear Reactor Regulation |
| To: | Librizzi F Public Service Enterprise Group |
| References | |
| TAC-8670, NUDOCS 8009090792 | |
| Download: ML18082B113 (5) | |
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, REGULATORY DOCKET flt[ COPY JULY 2 Z i980 DISTRIBUTION Docket File~
NRC PDR Local PDR ORB Reading NSIC TERA Docket No. 50-272 NRR Reading D. Eisenhut SURNAME,.,.
DATE~
Mr. F. P. Librizzi, General Manager Electric Production Production Department R. Purple T. Novak R. Tedesco G. Lainas J; Olshinski Public Service Electric and Gas Company 80 Park Place, Room 7221 J. Heltemes, AEOD
- S. Varga C. Parrish i~. Ross Newark9 New Jersey 07101 OELD
Dear Mr. Librizzi:
I&E (3)
The NRC staff has been reviewing the*subject of control rod guide thimble wear in pressurized water reactors. The enclosure to this letter des-cribes our review and makes an* assessment of this problem in facilities with fuel assemblies designed by Hestinghouse.
- Based on our review, w~ have concluded that th-is issue is* resolved for the 17 x 17 fuel assemblies designed by Westinghouse* for the Salem Nuclear Operating Station, Unit No. 1.
It is not expected that the above conclusion will be altered by the pesults of the.surveillance program sponsored by a cooperative owners group to obtain post~irradiation examination data from Salem, Unit No. 1.
We will notify you of any additional conerns when the results of this examination are* evaluated.
Enclosure:
Evaluation of Control Rod Guide Thimble Wear
- CC'.*M/encl osure:
See next page 8 0 09 09 0 7'\\-i..
Sincerely, tO:riginal s!enea byf
, S. A. Varia Steven A.,Varga, Chief Operating Reactors Branch #1 Division of Licensing MlC FORM 318 (9*76) NRCM 0240
- U.S. GOVERNMENT PRINTING OFFIC~: 1978 - 26!1 - 769
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 Docket No. 50-272 Mr. F. P. Li bri zz i, Genera 1" Manager Electric Production Production Department July 22, 1980 Public Service Electric and Gas Company 80 Park Place, Room 7221 Newark, New Jersey 07101
Dear Mr. Librizzi:
The NRC staff has been reviewing the subject of control rod guide thimble wear in pressurized water reactors.
The enclosure to this letter des-cribes our review and makes an assessment of this problem in facilities with fuel assemblies* designed by 1-Jestinghouse.
Based on our review, we have concluded that this issue is resolved for the 17 x 17 fuel assemblies destgned by Westinghouse for the Salem Nuclear Operating Station, Unit No. l.
It is r:iot expected that the above conclusion will be altered by the results of the surveillance program sponsored by a cooperative owners group to obtain post-irradiation examination data from Salem, Unit No. 1.
~~e will notify you of any additional conerns when the results of this examination are evaluated.
Enclosure:
Evaluation of Control Rod Guide Thimble Wear cc w/enclosure:
See next page i,
Sincerely,
. *~
lg,rt.!UJ~
Operating Reactor~h~anch #1 Division of Licensing
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Mr. F. P *.Li bri.zzi Public Service Electric and G~s Company July 22, 1980 cc:
Mark J. \\~etterhahn, Esquire Conner,. Moore and Corber Suite 1050 1747 Pennsylvania Avenue,.NW Washington, D. c.
- 20006 Richard Fryling, Jr.~_-Esquire
- Assistant General Solicitor Public Service Electric and Gas Company 80 Park Place Newark, New Jersey 07101 Gene Fisher~ Bureau of Chief.
Bureau of Radiation Protection 380 Scotch Road Trenton, New Jersey 08628 Mr. Hank Midura, Manager Salem Nuclear Generating Station
- Public Service Electric and Gas Company 80 Park Place Newark, New Jersey* 07101
- Mr. R. L. Mittli General Manager Licensing and Environment Public Service Electric and Gas Company 80 Park Place Newark, New Jersey 07101 Salem Free Library 112 West Broadway Salem, New Jersey 08079,
- Leif J. Norrholm, Resident Inspector Salem Nuclear Generating Station
- u. S. Nuclear Regulatory CollTilission Drawer I Hancocks Bridge, New Jersey 08038
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. ---1 Enclosure EVALUATION OF CONTROL ROD GUIDE THIMBLE WEAR IN FACILITIES DESIGNED BY WESTINGHOUSE A degradation of control rod guide thimble/tube walls has been observed during post-irradiation examinations of irradiated fuel assemblies taken from several operating pressurized water reactors.
Subsequently, it has been detennined that coolant flow up through the guide tubes_ and turbulent.cross flow above the fuel assemblies have been res;;onsible fer inducing v-ibratory motion in the normally fully withdrawn ("parked")
controi rods oosition.
When* these vibratina rods are in contact 'Hith the inner surface of t~e guide tube wall, a fretting wear of the wall occurs. Significant wear has been found to be confined to the re1atively soft Zircaloy-4 guide tubes because the control r~d :la~dings--stainless steel for Westinghouse-NSSS designs--provide a relatively hard wear Sur.face.*
The extent of the observed wear is both time and NSSS-design depen-dent and has, in sorr.e non-~iestinghouse cases, been observed to extend completely through t~2 g~ide tube walls, thus resulting in the formation of holes.
Guide himbie/tubes function principally as the ~~in*structurai members of the fuel
- a-sse;;t; y and as channels to guide and decelerate control rod rr:otion.
Significant loss of ~ec anical integrity due to wear or hole formation could:
(1) result in the inability of :he guide thi~bie to withst~nd their ant~cipated loadings for ruel handling accidents d
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an cc::nc1t1on
-.., even.. s; an,
(.J in er scramao1 11.y.
~ res~onse to the staff's attempt to assess the susceptibilfty and impact of guide himble w~ar in Westinghouse plants, two meetings were held with Westinghouse and infor-o~tion was submitted (References l and 2) on their experience and understanding of the issue.
This information consisted of auide thirr~le wear measurements taken on irradiated fuel asse~blies from Point Beach, Units 1 and 2 (two-loo~ plants using 14 x 14 fuel assemblies).
Also described was a mechanistic wear model (developed from the Point Beach data) and the impact of the model's wear predictions on the safety analyses of plar.t designs.
Westinghouse believes that their fuel designs will experience less wear than that repor-ted in some other NSSS designs because the ~estinghouse designs use thinner, roore flexi-bie, controi rods that have a relatively rrore lateral support in the guide thimble asse~bly of the upper core structure.
Such construction provides the housing and guide oath ~or the rod cluster control assemblies (RCCAs) above the core and thus restricts control rod vibration due to lateral exit flow.
Also, Westinghouse be1ieves that their wear :::odel conservatively predicts guide thimble wear and that even with the worst anti-c~pated wear conditions (both in the degree of wear and the location of wear) their guide thi~bles wii1 be able to fulfill their design functions.
The staff concluded that the Westinghouse analysis probably accounts for all of the major variables that control this wear process.
However, because of the complexities and uncertainties in (a) detel"ii1ining contact forces, (b) surface-to-surface wear rates, (c) forcing functions, and (d) extrapolations of these variables to the new 17 x 17 fuel assembly design, the staff required several near-tenn OL applicants to submit to a survail:ance program.
For acceptability, the minimum objective of such program was to deITXJnstrate that there is no occurrence of hole fcrmation in rodded guid~ thimbles.
..,?-iants0sing 'ies~inghouse HIPAR fuel ass,e.'T!bly designs (stainless steel guide thimble tubes) are not considered susceptible to s~gnificant wear.
y
- Enclosure To satisfy this request for confirmation of the Westinghouse analyti ca 1 predications, a cooperative owners group was estabiished which is now sponsoring a program to obtain post-irradiation examination (PIE) data from the Salem, Unit No. 1 facility. This PIE program will examine all guide thimbl.es in six rodded fuel assemblies having either one or two cycles of burnup.
It is our expectation that the program will confirm Westing-house predictions, and therefore this issue should be considered resolved for all Westing-house p_lants using the newer 17 x 17 fuel assembly design.
The relevant prirrary system design differences in plants fueled with the 15 x 15 fuel asse.r..blies as compared with those of plants fueled with 14 x 14 fuel assemblies are minimal.
And certainly the extrapolation of wear prediction is less than that associated with the extrapolation to the newer plants using 17 x 17 fuel assemblies.
Thus it is reasonable to conclude that the wear in 15 x 15 fuel asse~blies should be equivalent to that experienced and measured in 14 x 14 f~el assemblies, and therefore these desions are not likely to experience.significant wear to the degree that the design capabiiities will be impaired.
iherefore, we conclude that the information that has been provided is sufficient to resolve the issue of guide thi~ble/tube wear in plants fueled with 14 x 14 and 15 x 15 fuel assemblies.
Ref eri:r.c es
- 1.
Letter from L. M. Mills, Tennessee Valley Authority, to L. S. Rubens-:-ein, NRC, Dockets 50-327 and 50-328, dated November 27, 1979.
- 2.
Let:ter from T. M. Anderson, Westinghouse, to H. R. Denton, *NRC, NS-T1'4A-2238, dated April 29, 1980.
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