ML19275A170

Forwards Requests for Info on Guide Thimble Tube Wear in Westinghouse Fuel Assemblies.Requests Response by 790928. Requests Also Sent Directly to Westinghouse

ML19275A170
Person / Time
Site:	Sequoyah
Issue date:	09/14/1979
From:	Rubenstein L Office of Nuclear Reactor Regulation
To:	Parris H TENNESSEE VALLEY AUTHORITY
References
NUDOCS 7910020798
Download: ML19275A170 (8)

Text

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P00RORGIUI.

DISTRIBUTION NRC PDR R. Mattson Local PDR S. Hanauer 1 -,< -

SEP 14

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, Docket Files J. P. Knight

/ TERA R. Tedesco LWRT4 tile R. DeYoung Docket l42s. 327/323 D. Vassallo V. Moore D. Rc.is W. Kreger

5. Varga M. Ernst i'r.

E. G. Parris F. Willia s R. Denise M m r of Pa..;r L. Rubenstein Atty., ELD Te~.:ssec Vall e. Aut heri t s-C. Stahle IE (3) 5M Cnastnat 5'treet To.c II M. Service K. Kniel CM itance;.a. Tennessee 37?J1 bcc:

NSIC

Dear Mr. Parris:

TIC ACRS (16)

SU; ::T-REQUEST F07 A?JITIONAL INFOPTATIO' ON SEQUOYA4 Enclose cre requests for inform tion on the guide thir.ble tube wear in Westin;tase fuel asse-Slies for which we require your responses in order to cn>lue our revie iri this area. To keep on schedule, adequate respc.ses are needed by Septem.ber 23. 1979.

Also, the enclosed requests have been submitted directly to Westinghouse for resolution with regard to operating reactors.

Sincerely, Original tiCne d 17:

L. S. Rubenstein. Acting Chief Light Water Reactors Branch No. 4 Division of Project Management

Enclosures:

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ENCLOSURE 231.0 CORE PERFOR"ANCE BRANCH i

1.

Please preside the basis and derivatior of the guide thirble wear model described in Re'eren:e 1.

In particular, explain assurrtion 4 and the easations prosided under assa ;.ior 7.

Doe; the moccl predict maximur lo:al wea-or aserage circu 'e ential wea '

'e wea-m de', Wt-tin;5:sse has predicted ramiru-2.

Ul i; **e g idt 16 1:

51-e. -

a: s -e:

irie ; i li 't! ':

w :-- g ide t*i"!'c wa'Is in f

sat;e:te1 tc a 6; hand'ing load.

'y de: i; 5, m

" we-e t*: 'o('

at: r-'

These ca':.'ated valuei are listed in Tat'e 4.1 of Re'erence 1 We lir ts increase as a function of time i

n te ttzt thi stress ir*ersity for b:t' fue' asse-i'y desig s and that the limits always remain greater tha-the ani a-stresses, w*i:t increase as the wall is wo*n away.

From the supp:-tin; discussio preteeding tam e 4.1, it is not clear if the

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streit irie s'*y lirits are tire dependert.

Satt er assurption would explait the noted in:rease ir stress lirits,but does nct address the de:reasir.; rateria' toughness, associated with irradiation hardening.

If su:t credi* is being used, it is contrary to the presicus Westinghouse positio-in Reference 2 and iter 4.0.5 of Reference 1.

Please clarify whether or not Westinghouse has taken credit for irradiation strengthening.

Show that the criteria adopted represents the more conservative approach.

3.

Guide thirtle wear data, which were taken fro-Point Beach Units 1 and 2 spent fuel, are dis:ussed, listed, and plotted in Section 2.3, Table 2.1, and Figure E, respe:tively, of Reference 1.

Please cor'irr that the time units in Se: tion 2.3 and Table 2.1 are in error and rake corrections as s

needed.

55c? d n:t the u-its be day: ir:tead o' hours'

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Sab-itted Westin;*..se ir':-ca tion does not explain why the guide thimble wear model, w't:* was de, eloped fro reas rements taken on tw 2-loop ple-ts wit' 14>'

f.e' asse-t'ies, is a:p'icable tc wear predictions on p'a"ts c' cthe-de:1; :. Other NEIS-vende -desigred plaris have exper-ie :ed e *:'a-t-steri'i:' a-d ";ces-;:siti

" depender.:e ir the observed wei-

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t *. r: :t ' a t:0.* t s for wea r differ-e :e: a ' : :,i de s.:::-t ' : da'.a f:- a'l We stir;50;se desig variations, if tti a'vii: ' tecat e-ef desigt variatiors are justified, the sup-p: *.i"; data ca-be E-:vited ir a cor firmatery manner after NR' approval of the rete'.

please p*: vide details of your data-gathering proposal, a sched.le f;r it s 1 ;'e e-tatio", ard state your co7-itment to carry out this c:*#ireat:

-c;-a. Tnis date-gathe-ing progra should be completed e> pedi ti:_s'

s;:e-i ; the a,eilarilit cf irradiated assemblies in all Westin-5:.se ;1a-ts.

5.

In Re'erence 3, Westin;tcase stated that the effe:t of hydrogen content cr. the ne:hari;e' p-operties of Zircaloy is discussed in WCAp-9179 (Refe-en:e 4).

We have reviewed that topical rep:rt and found no inforr.a-tion or this issue.

Please provide your evaluation of how this considera-tics affe:ts the safet.> ar,alysis.

Include in this evaluatior. a description of the propensity for hyd*oger uptake of the Zirtaloy as a function of the accu alative wear.

6.

Wnen eddy currett testing was condacted or. werr. guide thimble tubes frot i

the Point Bea:t Urits, did the presence of zirconiu-hydrides affect the results?

He. sensitive is the ir.terpretatier of eddy currer,t signal s to hydride presen:e? How is this effect take into account'

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7 Referen:es 1, 3, an: 5 de n:t address the consequences of hole fomation in worn guide thir!'e tute:.

Mc-eover, it is net clea-froc the submitted info *ratice. if Westing 5c;se (1) has observed holes during inspection of tre 49 c; ice thirtles tubes that were exa-ined in the Point Beach spent fue', c- (I' has p-edicted bitt the guide thimble wea* model) hole fomation t: c:: - d -i ; p-:fe::et fue: lifetire.

Please clarify.

Also, if holes ha.e be+

tt:e,ed - are articipated, prcvide a discussion on the impact c' s :' b:'ei C-guite thirtle tube inte;-ity, control rod motion, and t e t'-tyd a 'i: pe-f: m ae:e.

This discussion should also account for fic ind :ed vib-atier resulting in crack propagation and possibly fatigue fra:ture ir lo: ally thinned areas of the thimble wall. This dis-cussion sh sid address the integrity of the thimble tubes during the entire I

core reside :e tire, both during periods of wear (under RCCA) and when the fuel asse-ilies a-e n t unde-R::As.

8.

Durin; the revie. of W:Ar-9179 (Reference 6), the staff questioned the Westingtse value for the ultimate tensile strength of Zircaloy components.

The subsequent Westin;5;sse response (Reference 2) stated that the ultimate tensile strength of Zircaloy was not used in the design analyses of present fuel assembly designs.

However, the analysis contained in Reference 1 uses the ultimate strength as a liciting variable. Therefore, please submit for review the Westinghouse correlation for the ultfrate tensile strength of Zircalcy.

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. t 9.

Se: tion 4.1 of Referen;e 1 states that the stress intensity factors are plotted as a fun: tion o' ti e for 14x14 and 17x17 fuel assentlies in Fig;-e 5.

This is net true.

Please provide such a figure or amend Fig.,-e 5 as ne:essar.

Pe-ite-a, Se: tic-4.C c' Re'e-e :e 1. yo;- ara'yses are based on uni forr 1:

Address the ra gir cf co*servatis-for this wea-ir e

t i-f t te:.

assu : tic.

Ccca-e yo;- res.,lts with an analysis that corsiders nor.-

r u r. i f t e-wea-resulting ir a shift of the neutral axis. hote that such stifts will result in bott direct stress and bending stresses.

11.

For Condition-1 and -2 load analyses of Reference 1, a skew factor is mertioned that a::ouets for the uneven axial load distribution. Cl ari fy ho the sk e. f a:t:r is related to both geo etric changes (resJ1 ting fror uneven wea") and assettly misalien ert. How does the sken factor impact the load analyses?

The equatior, for the wear volu.e in Reference 1 appears linear with time.

12.

However, in Figures 5 and 6, wear depth is plotted versus time, and the resulting correlation appears to be non-linear. Please provide infomation on how these parameters are related.

13.

For Condition-3 and 4 load analyses described in Reference 1, it is stated that the stresses in a worn guide thimble tube are based on generic stress calculations.

Please reference where these generic stress calcula-i tions can be found.

It is also stated that the stresses in the unworn guide thimble tubes are increased to accourt for the reduction of the tube This would indicate credit for a load cross section due to the wea scar.

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FNCLOSU0E

Reference:

1 T. F. Ande-se- (W 1 e t t e- (N 5-TK:-210.' ' tt D. G. Eisenhut (USNR:).

d a t e d J u"4 27,II?i, 2.

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P. A-te-se-

'W' lette- (*:-T*.: '9? ' te J. F. Stol: (USN:~),

date: N:,e :e-1?, 's-3.

t. " : :+-:--

iet:t-D. Tw.

1: E. G. Eise* hut (US*.:),

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" -::e-tie. c' Fue' a d Core Co o:r.e t Material s,"

We -i"; : ie E'e:t-i: :: ::-a t io-Re;:-1, W:A r - 917 Re.

1, dated s.

5.

T. v. A * :e - : - :. lette- (N3-TMi-199:' te D. G. Eisenhut (USNR:),

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3.

6.

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J. L;:.i-ka, "Fr:re-tie: c.f Fuel and Core Component Materials,"

We:ti ; :.se E e:

': C:-; -etior Re;:-t, W:Ar-9'.79, dated October 25, li-.

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redistribution to the unw;rn guide thimble tubes.

Is a skew factor employed in the Condition-3 aad 4 load analyses? Describe the stace of stress in the w:an guide tubes and boa thE unebEP Wear affects the load-bearing char-a:te istics of the w:rr tubes.

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