ML19319B142

Forwards Reactor Physics Review for Inclusion in Rept to ACRS

ML19319B142
Person / Time
Site:	Oconee
Issue date:	07/20/1970
From:	Case E US ATOMIC ENERGY COMMISSION (AEC)
To:	Morris P US ATOMIC ENERGY COMMISSION (AEC)
References
NUDOCS 8001080917
Download: ML19319B142 (7)

Text

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JUL 2 01970 P. A. Morris, Director Division of Reactor Licensing OCORRE I, II, ARD III - DOCKET N05. 50-269/270/287 i-The anclased review is submitted for inclusion in your report to the ACRS.

Original signed by.

E. G. Case Edson C. Case, Director DRS:SPR:MSD Division of Reactor Standards Raclosures Review - Oconee I, II, III cc w/enci R. DeYoung, DEL C. lang, DEL A. Schwencer. DEL-Distribution:

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_g DR Reading-DRS. Reading SPB Reading bec: 'N. Dunenfeld-M. Rosen R.~ Case-

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e REACTOR ?liYSICS REVIEU FOR.

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5 OCONEE 1,-II. III_

I E ACTOR _L

'3.0 Introdu'etion Oconce

We have reviewed,the reactor physics related aspects of the licant in.the FSAR, c'rcactor? designs based on natcrial provided by the app in revisi'ons to the:FSAR in response to cur questions, discussions j.

d some independent

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meetings with the applicunt and~ Babcock 5 Wilcox, an calculations provided throudh our technical assistance program at the computer In general, vc find that Brookhaven National Laboratory.

l techniques used, and comparison calculations of expericenta prograns',

data: provide's his denrce of confidence that the nuclear characte

~ have been pre-

'of the reactors and attendant safcty.raliced provisions D

h dicted accurately. 'We: conclude, however, that greater conservatism t of power distribu-

~ the _ applicant has voluntected is required. in the arcas ii coderator~

tion'nonitoring and control and restriction of the BOL pos t ve Noef ficient,.'and' are working with him on technical' specification with those for H.: L. Robinson, Point Ecach, and Palisades.

licachivity - Calculation _s ;

and

, =The, applicant ;has provided discussions of the computer progra Wilcox uses;in prediction of the nuclear-characteris-techniques. Babcock 41

'Also provided-are exa ples of the ability

.: tics lof~its reactor'designa.-

and Pu 0 - UOpcritical asse=blies.

jofTthesemethodsto.predictUO 3

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6caonctrdte the validity of the ccthods'uced for predicting k,gg

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forilcrgepowerreactors.-

i Detdiled three-dinensional; power distribution neasurchents have been

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perfor=cd at the.Echcock & Wilcox Critical Experinentc Laboratory.

R'ecults of calculations with PDQ07, c three-dimensional program, agree The Babcock and Wilcox quite well-with neccured power distributions.

~ version of PDQ07 also' hcs ipcorporated a thercal feedback option,

.c

~

4 permitting ' accurate descriptions of the radici and axial power distri-butionc in analyses of control rod c2ncuvering, xenon stability analysis

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These distributions are and control, and reactivity coefficients.

nececcary in the evaluation of thermal margins.

Tuo-dinencional PDQ cn lyses with'Har:ony fuel cycle calculations are e

.also dibcusccd, and burnups and first and second cycle and equilibrium core enrich =cnts cre provided. We find the material presented decon-

-straten vell.the cbility to-predict phycles characteristics of the recctors.

ncnctivity Centrol necuirements The'applichnt-hsc provided cubstcntial caterial supporting his ability i

to' control'the:cxeces reactivity provided in the reactors and mainta n-a shutdown'cargin to hot critical of at' 1 cast 1% 4k/k throughout life -

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Sixty-one 10ith the noct reactive' control rod. stuck out of the core.

ffull length control-rods'cre provided. This is greater than the-

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number: providdd in'other P3 decignc. Their predicted vorth,12.1%/ik/i

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For 90% of the s

fii Oconce-I,Lis.alsofgreater.than usually.provided.

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l rod vorth is used ji

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Efuel:cyc'ic$in(OconeclI,l.0)to-l.3%ofthiscontro

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for partihl xenon override capability, in one of four.decignate

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'" 5 2 f Thic korth vi!1 normally be' inserted in the reactor and

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. groupings.;

than

unavdilabicffor. shutdown,- but;the re.nining worth is still corc-1the1 usual amount providch heept for_the trEnsient xenon override, in a =anner

, (solubicfboron;isiuced fo'r centrol11n th6 0conce reactors f

icypicalfof P W s.

of control requir=cnts for the core life

-The. applicant's accessncnt Doppler deficit based on the is conservative in that it aceunes a i t in life, maximum enpected' fuel temperatures at the'cppropriate.po n d'

'the;cr.lculated control. rod worth sas reduced by 10%, the calculat 5-Juorth of the stuA red appears' very ccascrvativa co= pared to e ed in the rod worth' i

. PkR's and aas not. reduced, - the assunpt on us

? calculations were conservativu, and the calculated increas fof the' full 1cngth rede frct tue pres::.nce of.'the 8 part length

-4 cas:not claimed. - For thc c rencons we concluda adequate co by Verification duringlthe

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worthhdsibbenprovidedtoaccureshutdown.

(0conce 1 startup progr= will' also provide ~ assurance-of sa 4

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conditions Jin this ares.. f Although there arc dif f crences in wor he' fuel loading, vc foresce no problems.

n jUsits{lIandIII,dependingon-t

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3 1The bAcic concep Lfokth'e pouce-rm;;e nucicar pcue s

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stion-monitoring {insthci cconce. reactors:is casentially th

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irecentPUR}cbeginningwit reliance'onfouraxidllyjcplitout-of-coredetcetorslocatedsyn=ctri-6 e

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'cally and.cppocitelthe-core diagonals, and provicion for:in-core cappi u

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in the Oconce recctors];the in-core ceppin;; provis on co 1

' assemblics of[ceven locci cnd onelfull' length self-powered neutron,

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bdctcetors.~ -Thece are11oedted roughly on a spiral, plus a-nu=ber of; b

provided in Oconee

'sy==ctry conitors. ?Special c:libration tu es are o.-

1 L1'. (Readout ~ic~through the-pinnt co=puter.

11 e: applicant's. initial pocition was that the in-core detectors were -

c provided mainly'for obtcining power distribution histories for fuel 1 cnnage: cat purpeces, plusl initial uce in the startup.lprogra= toLo Lcorrelctions with-out-of-core detectcr recponces..Our position is j

out-of-cor6 detectora crc adequate for nenitoring pouer naldistributions

~ c Jorigindting froit cnic1; xenon inctchility and nicplaced control. rods, i

ifor

provided there' th sveilable pcuar dictributica cappin3 capabil ty periodic calibratien of the cat-of-cors detectors cad for investigat indiccted by the out-of-core detectors..

.ofdpover distributica ano alict r

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LTha spplicdntLit pra; cat.has agread to write a technical specificatio m

^ forschefis core deccctorse

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Oconec re. actor'for control.

b

)Eijhtjpartklengthr$dc~cre;providedincach..

f axial xenon-L

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. of)the axial'pover/chepa. T!!cse are required for control c

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((nstabil'ibich,predietediicconce'l'tobeposcibicat. SOL ~viththe;

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[ fxen5nioverrideIro$h[inithe core. 2The cpplicant has stated 1h w

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> technica* specification licits on the inbalance of pcuer in the upper and ivver halves of the cerc, to prevent unacceptabl6 axial peaking

' factors.

Automatic protcetion is not provided.

It has beca our under-standing, howcVer, that notion of the part length rods in the wrong direction to control an inbalance (or fcilure to use the=, although the tine scalu then.uould be many hours) could lead to core de= ge.

We conclude automatic protection would be required in that casc.

Westing-houce provides nutonctic protcetion to prevent imbalance corresponding i

t to en exial pcching factor greater than design value. The pplicant, in response to our c'ucation, has provided analysis of only cac case,

-uhich.shows no probica frcn improper part length rod notion.

Uc have verbally inforced the applicent of our concern in this regard.

The appliccat has not yet responded to our request for a technical specificctica cnd basis for x-y (or radici) power tilt li=its.

Since

'the appliccnt c1cinc x-y ncnon stchility, cnd vill verify this in c scattup test, the only-knoun sourca for such tilts is nisplaced control

• rods.

Since single misplaced rods do not result in violation of safety

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limits, va necapt that only clercs cre required frcm the nuclear redi:1

. tilt systec. These provide' backup protection to the safeguards derived frou rod l position indientcrs.-

Modcretor Coefficient

.The cpplicant has proposed for Oconce I a technical specification for -

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a'E0L moderator _coefficieni of 40.9 n.10 Ah/k/*F at full pcuer, based upon'.use.of this'valuc in his accident analysis. Cur evaluation is i

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?th:t this iciaccept:bic for rod?cjection accidents, and for x-y xenon z

ictability.(because the pplicant in ec nitted to show stability) but-4 7 we-have dot (yet co=plcted cur ~ca lysis sf tha n :iinun poscible effect p

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'(cf[thc= relcted :$odcrater dr.nsity ec$fficient) ~ in lo: -df-coolent s

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The predicted codcretor tcuperature coefficient is-+0.27 x cccident.

10' $k/k/*7 fos _OconckI.. More ner;.tive coefficients are predicted

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The Unit I value for,Un'its 'IN add III,- which' predictions ec support.

feas:chtained'fren~c[pencridistributionweightedeniculntion,andis cu:ller then the'icothernal eccfficient.- Uc believe this effcet results Our technical assis-fron precence:of the'.xcnon override control bcnh.

tence consultants at I".1 hcve shown that the. pouer distribution weighted cocfd.cif.nt can be larger or'c= 11er then the icothernal, dependin3 on

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i the poucr!chcpc..;Furthsr, their calculations indicate a grcator-L

- ssluble boron ccccentraticnLdill be rcquircd than the applicant predicts, _

inhich1:culdreicathenodcretorcob.ffici2:t. ' Uc do not suggest the ICL p

Jccicui tions cre core valid th tha pplicent's,~but~they contribute

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- ;to our concern that_c core positive ccafficient night be present in s

w the; reactor thanithat pr'adicted..'Ue.;Ic therefore vorhin:,very. carefully A

. juith thi :.pplicant en'n ccchnical cpecification to ens rc that the EOL

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".fuib poucracccffidient nn predictcd frc iou power nessurc=ents'is

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- indeed?.linited3o.+0.9'x.10:4$li/k/*F,'accening!theresultsof-theloss-J of-coolant analycic cupportuthis' value. -

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