ML20024G513

Responds to Re Fuel Densification in BWRs

ML20024G513
Person / Time
Site:	Monticello
Issue date:	08/15/1973
From:	Mayer L NORTHERN STATES POWER CO.
To:	Ziemann D US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20024G507	List: ML20024G506 ML20024G513
References
NUDOCS 9102120587
Download: ML20024G513 (9)

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Angast 15, 1973 lir. D L Zier. ann, Chicf operating panctors I: ranch 92 Directorate of I.icensL"3 United St.;tes Ate::1c Energy Cow.lcsion U2 shin;;t:n, D C 20M5 Dear lir. Zir.rnn;

!!CCITICI3J.0 '3CIIlul GOCrifl1;G pit.l?T Dochet Eo. 50-253 Lic=.se 1:o. DPR-22 Pacpense to July 15, 1973 f.sc teete-cp real r me;ficatien nin letter is vritten in resprma tr> your intter of July 16, 1973 to Mr. Arthur V Dituhsrt C:SP) which presented the elwcuts the /EC Staff rich:d t o be included in the evaluatica of fcel Gns '.fication in boiling tracer reactors.

Arc. lysis for tha I!cuticcllo rarctor :: s doan generically and is reported im Supp)c:ncut G to Gestral Elcetric Topical Report W-10735, "Densificatica Considerations in I',7R ruct Davicn and Terforrance," vhie.h is being cencurrently filed with AEC by General Elcetric.

% c July 16, 1973 letter asked ttat the effcces of densification usien the f taff assu=pticas be analyrad for ner:=1 operation, nnticipatcd transients and accidents inclenin the loss-of-coolunt netident (LC).

Each of these events is discussed in NIrd-20735, Supple =ent 6; evaluacic.n of the results presented shou tlut the culy siguificant effect of fucl densificatica involves the postulated 140A.

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'l As part of the Staff conclusions, the July 16, 1973 Ictter stated t. hat LE chang,o.s in design or uperattag conditions are necessary to waintain re-h quited nargins we rhould culait prepotied chan;;cs and operatint, limitations with thenaslysts.

Section 6 of NKLX-10735, supplement 6 precents, in Techni-ca.1 Specification fornat, tro potential I.iaiting Conditions for Operation l

l t&Ich voald r:mintaf.n regttired carpins r.hould the staff derof fication criteria

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be 1::ple=3ted.

7bo TACA analysis to ra.ct thin criteria var. perfor=ed in etu re,w First, t)_ :.

.:.no allo n ble average plcnar liccar hMt acceratica tnte (U'CC2) m detemir:ed as a function of caposura Lased en a very cen-carva:L'.a 6torprtraticn ci LS.) f taff critaria.

Fecend, nu nnetlycto un:: dere using n nitably coacorvative alternative interpretaticu of the AEC criteria taced en a necte: ical analysis of czlating data; the m-rim" alluvable AF1.W. vne. 111: men deterclud. ';he re ulen are prewnted in Tiruren 4 901 ced 4-9C2 of I!17.X-lO735, Supplcncat 6 aluaa with a ec::parison to that clieved by currenc Zach::i:cl Cpc.cification limits.

In additiva to the. LCCa analytis s t.htch detemi.ced allevable fuel bundle cepicut pe'.cr invels, the Otttff cri-teria ca pcraer spihing no it affects the narc:a1 opernting liccar heat genera-titut inta of the bottest fuel. pta can alco deternir.ed. 'iho r.=icu:2 allcrable 4

i IIGR in reduced from 17.5 h/f t as shown in Figure 3-6 and discussed im See-i rica 6 of "ZS10735. A su:=ary of resulto pertaining to the Ponticello Pl.ut

I is pecccated in colt.=n C og Table 6.2 of Irc

(-10735, Suppleccat 6.

f With royard to tbn postulated LOCA, provicus cnalyces indicato tint the Eenticello Plant catisfies the Interim Acceptance Critorin applicable to this i

cycr.t withcut cdditiceal specific rostriction or altered coden of operatica.

It is na:'n cle.ar in the.Taly 16, 1973 Ictier that the principi effect of the n

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L'e reccerand tht: th Staf f centinua. to utilica t.bn enictin7, l

1000 ttu/br it'*F value for all :.nslyces until cuch time as Cencral Electric can re.trer. ably c='lete derelv;=nt of a norn co;histicated cualytical redel reprewitin~, the cht.ngos of r p cendu: ten:o in relatica to the varioun yhtne:er.a. includi ~, Lu:.1 dentificr.tien, associ;*.ted with incrc391rq expnure.

There doen rot :.ppcar to l>e c.ny cafety reason for i=c41 ate act. ion.

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ta anvc revieved tha ir;..;t ca ;baticella cycla 2 oparativa, chould ca nu.p;t.d Oc.1:r:l Elcetric Tennic :1 ?euzfic ktican bc ibpleented falla.ang a._m. v c

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paced on uo:.al cperatica; the lattar, in the.: solves, would bava c.22:i:..al iq::: : :. c'* t. :' 2 m rntien. If O

• ui t r b l't c enr e: tati'ta. c ! terr.at.1. u ctrreact w re h e=ed c p p ro p ric t e. a n.::.2rc n l..: d e ra r e o f 5** tuy c e r e c eu;: ; u ra r t he end c i cycla 2, If cdharen:o f a ti.e are cocacrvative interpretation ei ;Lnt criterin vers r~":f red, it !"wrc that a greater plint thrate ray be nece -

r.aty during a d ra.ific.r.t roctica of :.he re uinder of cycle 2.

It should ba noted that the cur.~,ested Technic :1 f.necificatic n linitatican tefer t o bundle regncat p0Ver rattar than total plant power.

A detailed conlysis of the urect of these Lundle pever linit:tions on future plLat operation in bein~, initinted.

Projected r. car-tern operatien indica'.as that the plant vill c; erate belc-a the he ta cer /.-:: of TI;; red t.-PCI ned J.-902 n r tac c.

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Havin.g reviewed I;r.D;t-10755 und Supple =ents 1 through 6, we agree with the Ctmici I:lcctric po::Ltica that the Staff critaris presented with the July 16, 1973 letter is ovetly conservativo in lir,hc of c.xistini: data concerning I

Eva fuel dcnnificatien, r.13cd on ec pc.risons of tha inforstion in Supplccent.

6 to Isr:I!-10735 aca cur currr..t l'.:sticello cycic 2 epare. ting parce.aters,

• e bli.tre thu no irnedicte retien is required ned that norual oporntiin r.sy be safely centinuc<.i.

it in r.m;eested t'ut C= mal Cicetric generic fili.n;t of UED.l-10735, Rppi_=nts 1 tJ reu $ 6 be rn;rc: end in the :' aticello <'o&ct, ricaco

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' /a ["J Mr. D L Ziemann, Chief 9

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Dear Mr. Ziemann:

MCt4TICELLO NUCLEAR GENEl% TING PIANT Docket No. 50-263 License No. DPR-22 Response to July 16, 1973 AEC letter on Fuel Dennification This letter is written in response to your letter oi July 16, 1973 to Mr. Arthur V Dienhart (NSP) which presented the elements the AEC Staff wished t a be included in the evaluation of fuci densific.otion in boiling water reactors.

Analysis for the Monticello reactor was done generically and is reported in Supplement 6 to General Electric Topical Report NEDM-10735, "Densification Considerations in BWR ruel Design and Performance," which is being concurrently filed with AEC by General

.cctric.

The July 16, 1973 letter asked that the effects of densification using the Staff assumptions be analyzed for nomal operation, anticipated transients and accidents includir; the loss-of-coolant accident (LOCA).

Each of these events is discussed in NEDM-10735, Supplement 6; evaluation of the results presented show that the only significant effect of fuci densification involves the postulated LOCA.

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As part of the Staf f conclusions, the July 16, 1973 letter stated that if changes in design or operating conditions are necessary to naintain re-quired margins we should submit proposed changes and operating limitations with the malyses.

Section 6 of !;EDM-10735, Supplement 6 presents, in Techni-cal Specification format, two potential Limiting Conditions for Operation which wuld maintain required margins should the staf f densification criteria be impicmented.

The LOCA analysis to meet this criteria was performed in two ways.

First, the maximum allowable average planar linear heat generation rate (APUICR) was determined as a function of exposure based on a very con-scrutive interpretation of the Staf f criteria.

Second, an analysis was done using a suitably conservative alternative interpretation of the AEC criteria based on a statistical analysis of existing data; the maximum allok ble ArulGR was likewise determined.

The results are presented in Figures 4-9C1 and 4-9C2 of NEDM-10735, Supplement 6 along with a comparison to that allowed by current Technical Specification limits.

In addition to the LOCA analyr,is, which det.crmined allowable fuel bundle segment powe r levels, the Staff cri-teria on power spiking as it af fects the nomal operating linear heat genera-tion rate of the hottest fuel pin was also determined.

'Ihe maximum allowable IJIGR is reduced from 17.5 kw/ft as shown in Figure 3-6 and discussed in Sec-tion 6 of UEDM-10735. A surraary of results pertaining to the Monticello plant is presented in column C of Table 6.2 of SEDM-10735, Supplement 6.

With regard to the postulated LOCA, previous analyses indicate t.in t the Monticello Plant satisfies the Interin Acceptance Criteria applicable to this event without additional specific restriction or altered modes of operation.

It is made cicar in the July 16, 1973 letter that the principal ef fect of the

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H Staff's fuci densification models on the LOCA calculation is a modification 2

of the 1000 btu / hr f t P gap conductance in the AEC approved GE ECCS evalua-tion model.

We reconnend that the Staff continue to utilize the existing 20 1000 btu /hr ft F value for all analyses until such time as General Electric can reasonably complete development of a more sophisticated analytical model representing the changes of gap conductance in relation to the various phenomena, including fuel densification, associated with increasing exposure.

There does not appear to be any safety reason for frenediate action.

De fe rral of action until de.velopment of a complete analytical model upon which general agreement can be reached npp-is to be the preferabic alternative.

We have reviewed the impact on Monticello cycle 2 operation, should the suggested General Elcetric Technical Specifications be impicmented following AEC Staff evaluation. The APUICR limitations based on the 1.OCA analysis appear to be more restrictive, at all times, than the UlGR li.mitations in-posed on normal operatian; t.hc latter, in themscives, would have minimal impact on cycle 2 operation.

If the suitably conservative alternative approach were deemed appropriate, a maximum plant derate of 57 may be necessary near the end of cycic 2.

If adherence to the more conservative interpretation of Staf f criteria were required, it appears that a greater plant derate may be neces-sary during a significant portion of the remainder of cycle 2 It should be noted tha t the suggested Technical Specification limitations refer to bundle segment power rather than total plant power.

A detailed analysis of the impact of these bundle power limitations on future plant operation is being initiated.

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Projected near-torn operation indicates

t. hat the plant will operate below the beta curves of Figures 4-9C1 and 4-9C2 for the next one to two months and is cucrently below the gamma curve.

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11aving reviewed NEDM-10735 and Suppicments 1 through 6, we agree with the General Elcetric position that the Staff criteria presented with the July letter is overly conservative in light of existing data concerning j

16, 1973 BWR fuel densification.

Based on comparisons of the information in Supplement 6 to NEDM-10735 and our current Monticello cycle 2 operating parameters, we believe that no imediate action is required and that r.omal operation r.ay be safely continued.

It is requested that General Electric generic filing of NEDM-10735, Picase Suppicments 1 through 6 be referenced in the Monticello docket.

advise

's if any other action or additional infomation is required with regard to this matter.

Yours truly, M

L 0 Mayer, PE Director of Nuclear Eupport Services IDM/M11V/br cc: B 11 Grier G Charnoff Minnesota Follution Control Agency Attn. K D:ugan

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MCKNOWLEDGFn EONOT REurnm rrLei FROM:

DATE OF DOC DATE REC'D LTR' MEMO RPT OTIIER Shaw, Pittman, Potts & TrowbritJe 4

Washington, D. C.

20006 George F. Trowbridge 8-15-73 8-15-73 x

gog ORIG CC OTHER SENT AEC PDR x

D. L. Ziemann 1 signed SENT LOCAL PDR x

j CLASS UNCLASS PROP INFO II. TUT NO CYS REC'D DOCl2T NO:

x 40 50-263 DESCRIPTION:

ENCLOSURES:

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Ltr submitted on behalf.of NSP....re our Ler dtd 8-15-73 fm NSP ro our 7-16-73 ltr 7-16-73 itr....trans the followings furnishing info re GE Topical Report NEDM-

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10735. "Densification Considerations in BWR l

Fuel Design and Performance".

NOTE: 1 cy Advance to Ziemann 1 cy Advance to Butler PLANT NAME:

Monticello (40 cys enc 1 rec'd)

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