ML19257C052
| ML19257C052 | |
| Person / Time | |
|---|---|
| Issue date: | 12/20/1979 |
| From: | Eisenhut D Office of Nuclear Reactor Regulation |
| To: | Lewis M AFFILIATION NOT ASSIGNED |
| Shared Package | |
| ML19257C053 | List: |
| References | |
| NUDOCS 8001240039 | |
| Download: ML19257C052 (1) | |
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Mr. Nrvin I. Lewis 6504 Bradford Terrace PhiladeJphia, Pennsylvania 19149 Gear Mr. Lewis:
Your letter to. Harold Dentos asked fee infonnetton. on the-problem. of
.. y swelling of metal fuel cladding. In. enswer to your speciffe gaetticas,
,-J J the recent. problem resultig from tests conducted at Oak. Midge National Laborateries deals only with rirealloy cladding and does not involve.
pellst swelling, manufacturing defects nor fuel pellet defects.
Enclosed is a Movember 9,1979 letter that was sent to all ommers of operator light water reacters that gives additional information on this recent problem.
Sincerely, Stiginal signed by Darrell G. Eisenhut Acting Director for Operating Raacter Projects Diffs,i'oo. Af Operating Reactors
Enclosure:
Ltr. Giuing Additional nformation dtd. ll/9/79
..m DISTRIBUTIONg gg Local POR NRR Reading H. Denton E. Ca-se H. Berkow/W. Russell D. Haller F. Schroeder D. Vassallo V. Stello D. Eisenhut R. Vollmer B. Grfnes T. J. Carter i 804 154 A. Schwencer i
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a UNITED STATES
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'i NUCLEAR REGULATORY COMMISSION
. E WASHINGTCN. D. C. 20555 o
Novemoer 9,1979 (LETTER TO ALL OPERATING LIGiT WATER REACTORS)
Gentlemen:
On Novemoer 1,1979, the 1RC met witn reoresentatives of the NSSS vendors and fuel sucoliers to discuss those cortions of their ECCS evaluation models dealing with fuel cladding swelling and the incidence of rupture. The staff indicated that as a result of its ongoing evaluatier. of data from confir-atory research crograms concerning reactor fuel, it was uncertain that presently accroved ECCS models conform to Section I.B. of Aopendix K,10 CFR Part 50 and whether coerating plants conform to Section 50. 6 of 10 CFR Dart 50.
The staff discussed now these data. sere developed into new fuel cladding strain and fuel assembly flow blockage models. This issue received considerable media and otner puDlic attention during the aeek of October 29 and was addressed in the Comission's ?ress Announcement (see Attachment 1) cateo Octooer 31, 1979, and in a Commission briefing on November 2,1979, that was attended by the public.
At the November 1,1979 meeting each vendor or sucolier was asked to show how, in view of these new models, the olants of their design continued to meet the limits of Section 50.26 of Part 50. Their cresentations were documented and formally submitted to the staff on November 2,1979 (see ).
The information presented demonstrates that, in general,
- cr coerating L'.vRs the calculated ;eak cladding temoerature following a
- ostulated LOCA would not exceed the 22000F limit in Section 50.16.
As you are aware, our preliminary evaluation, based on tne infor ation received from the fuel suopliers, caused us to conclude that there is no significant safety concern for your facility. There remains, however, a need for you to confirm that the reoresentations made in your benal f are correct. There-fore, you are hereby recuested to provide, within sixty (60) days of the date of this letter, written statements, signed under catn or affirmation, wnicn will enable the staff to determine, in light of the concerns described above, wnether or not further action is necessary.
We are enclosing copies of the material relating to fuel cladding strain and fuel assemoly flow clockage that was presented by the staff at the Novemcer 1 and 2,1979 meetings. Also included is the documented rescanse of eacn vendor or fuel suoplier.
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. November 9,1979 You are requested to review the enclosed information on the new fuel cladding strain and fuel assembly flow blockage models, designated as Staff's Analysis on the enclosures. Where the models used by you for cladding strain and assembly blockage in your ECCS calculations are as conservative as the staff's new models, please confirm that this is the case. If your models are as conservative as the new models no further calculations are necessary. However, if regir.is exist where either of your models is less conservative than the st.ff's model additional calculations must be performed to demonstrate compliance with the limits o f 10 CFR 50.46. Aporopriate sensitivity studies may also be submitted with your evaluations.
If you have any questions regarding this matter, please contact Mr. Paul Check, Chief, Reactor Safety 3 ranch (301-492-2030).
- incerely,
/
cting Director
.cs e,
Division of Operating Reactors Office of fluclear Reactor Regulation
Enclosures:
1.
NRC Press Release (79-192) 2.
'/endor Resocnses 3.
Staff Analyses 4
Background Material
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Washington, D.C. 20555 No.79-192 FCR IMMEDIATI RELEASE
Contact:
Fran'k Ingram (Mailed - October 31, 1979)
Tel.
301/492-7715 NRC STAFF TO MEET WITH FUEL SUPPLIERS ON EMERGENCY CORE' COOLING SYSTEM CCCES The Nuclear Regulatory Commission staff will meet tomorrow, November 1, with representatives of reacter venders and nuclear fuel suppliers--Combusticn Engineering, Inc.,
Exxen Ccrporation, General Electric Ccmpany, Wes:Inghouse Electric Corporation and Babecck and Wilecx Cc=pany.
Utilities which operate nuclear power plants have been infermed.
The purpose of the meeting is to discuss the staff's cngoing eva.3uation cf the results or. tests on eAectricaA;y-heated fuel assemblies conducted at the Oak Ridge (Tennessee)
National Laboratory.
They indicate that emergency core cooling system analytical codes currently used ec evaluate the effects of postulated loss-of-ccolant accidents might not be in ecm-pliance with NRC regulations.
The portion of the codes n
question deal with the effects of fuel swelling and rupture and bicekage of cooling water.
The information presented by One vendors at the meeting will be used by the staff to assess whether the codes presently ased might underestimate the peak temperature of the hettest fuel red in a pcwer reacter which, by regulatien, should not exceed the NRC limit of 2200 degrees Farenheit under postulated accident conditiens.
The staff will then decide what acticns, if any, may need to be taken in regard ec pcwer reacecrs currently licensed for cperation.
The meeting, which is open tc the public, will begin at 9 a.m.
in the NRC 's of fices at 7920 Norfolk Avenue in Sethesda, Maryland.
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%vesoer 2,1979 NS-TMA-2147 M. :arrell G. Eisenhuf.
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'Asti ;5:use recrasantstives were in attencance at h resting esMed by tre Much.:.- Ecgula c ry Cz nissden en ?:cve rar 1, MM in 3cce:ca, :: discu:s tae cra f n:Or: *Cisddies hellir.g and.luo:::re R:els far LCCA Analysis' by O. 4. ? *,ert ac4 E. C. Veyer. That NAC re: Ort :r eser,ts inferration en Nel
- d :5 tvier under t.:ss of Ccolan Acciden; i.LCCA) c ndittens and concer9 was ex: ras s t: : hat the craiyt! cal ecceis cerived in =e MC re::ce; indicata thct the '45-ingrouse ECCS evaluatica r:cel may cct. te in ;.cliance with ;?.e re;;irerenu of ICC.:R50 Appendix L it tha ::r.:lusien of ths meting, :.*e U.C recues:ad ihn Wes:irghcuse r:s t 'c a wri. ten resxcse to wes:Ter.s caal fcq tn tMs concerr.. This le ner is in res::. :a :n wt recen.
Nestice In Ugh of me data :rasented in me MRC eport, do ce 'Jastingnc;sa fuel red cecu's reet ICCTR50 Accer,oi.x X7 Ou m ien 2 I! 2e NRC fuel red cceTs were used ta ce Westin,nr.me ECCS avelnatien c ccs!,
woulc =c 1 plants rett 'CCR50.46 limits?
Senien 3 If any plants : not t e'. IOC7E50.l.6 F e --
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d nter'n and Ic.99 ;c-: e;;cmene3-t DUPLICATE DOCUMENT Entire document previously entered into system under:
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4 Mr. Darrell G. Eisechut it2vember 2,1979 Retecnse The edels fer fuel rod burst enq:erature, post-burst strain and ficw channel bicckaga used in the Westinghouse Appendix X ECCS evaluatten inodel are derived free an extensive data base consiscing of single re,d ar.d s2ritired test re uits.
This data base was cer:ared to the new data base used to derive tne pre;0 sed NRC fuel roc ecdels. These new data revealed ec ucycected trenes or behavier not previcusly extarice.c+d and in fact cerclerent the data base used to derhe ths Westir.ghouse fuel rct redels. The Westir,ghcuss het red r.odeis currently in use were develc;ed witn scecific c:nsideratten of tecwn biases in the experir. ental d:ta and accrcpriate statistical treat ent of *.tc dats. It is Westingh use's cair.fcr. that similar statistical rea:.ent of the new da.a base ar.d ::r.sideratica of tnewn biases in :ne data wuld shew that the West-inshouse fuel red codels in fact adecuately ccver fuel red behavier observed in the new data.
Westinghcute has evaluated the potantial ircact of directly using tne EC fuel red blockage :occel in the Westingneuse ICC5 evaluatien model. Inferraticn cer-tainir,g te the fuel r:c recel of interest was extracted f cm recent large treak ECCS cralyses for c;:e-atiry Ves:ir.gtcuse piants :n estatifsh the applicacle range of in ares anc thus provide a basis to esti= ate the potential iq:act of the fuel red blecXage change.
Table I st:ws the clad str*st, tre clad hestue rate and the clad temerature at rupture tice fer the 11nitir9 large brNk scalysis.
The fclicwing sumartres cur evaluaticn of tas three fuel red :x:dals.
- 1) Burse As shcwn in the ateve ta:le, the hecs stress "rier to ru:ture falls in *te rtr':e
.of S to 2.2 KPSI. !c that racte of h oo stress, the Westinqnouse turt,t *.y:ees-ture curve is sufficiently close to tne !GC EE"C/Sec curve that diffeneces ir peak clad tecerature (MT) resulting frc= use of Oe ::.o burst curves
- cult be Sr.all.
In excaring c.ites fer whien the heatup rates are les: than the ES'C/Sec case, a sensitivity stuay was erfor ee usir.g a '4estiegneuse hcatuc rata curve of 6.7"C/Sec. This stucy s?,cwed a PC"' increase cf 10"F, For 5 all Snat LOCA er.aiyses, a heatuo rate de:encenes has alreedy teen fac.cred into t'.e calculation using the 'westirs*.cuse excerimental data base.
- 2) Strain The range of intarest for ccscaring results of t$f V and Fp~ F.
circs ferar.tial strain redels is fer burst tercerature from 15550E T.o if,M The curves for the two models are very si=ilar and cross in 'nis range of interest. the effect of lacreasing nr decreasing ctre:.efe.~='.tial st.-ain ny the a= cunt of diffennce between ins two c:.rves is ::all, and furce-cre have cceceticc, self-cancell t effects. It was cerclucec by -he staff anc w a: the Neverter i < ce :t.o tha: no s.gniffeant i:cact would result fm the if ffer~ecca in tne two curvu.
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