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NRC DISTRIBUTION roa PART 50 DOCKET MATERIAL<

FROW!!r Stolz J Fla Power Corp DATE oF ooCUMgg

, St Petersburg, FlaDATE RECEIVE o 1-29-77J T Rodgers"

_LETTrn ONoronizEn enor iseuT reau NuusEn or ComiEs nECEivED. jo::f GIN AL 8 UNC LAS$1FIE DDCorv .

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DESCRi? Tion ENCLOSURE ,

Ltr te 1-21-77 meeting..... notarized 1-27-17 Info relat ive t'o B&W topical BAU-10104A.......trans the following: '.'B&W's ECCS Evaluation Model" as revised

. . . . .ad . s ing that it pertains to Crystal

River... .(40 Cys enc 1 rec'd)

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PLANT NAME:Crystal River #3

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SAFCTY FOR ACTION'INFORMATION t'm.? T D Q 2-1-77 chi

/lASSIGNED AD: V6 s .s .T //o ASSIG' fen An*_

/ BRANCILC1'35 M o / 2.- .

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g g g ggy,_dGER. AC.,//an LIC, ASST.PROJECT _fgu\GER:

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_ INTERNAL DISTRIBUTION

('1GG PILE. ) SYSTEMS SAFETY PLA!sT SYS'" EMS SI.TE_SRFJY &/ Iliw run_ !!EINEMAN TED_ESCO Ch'VIR0_31?ALYSIS/ I & E f.3/ SCllROEDER REFAROYA DENT 01L&lUErR0/ OELD TAIEAS

GOSSICK & STAFF ENGIllEERING I MOLITO E!NIRQ_ IECH-MIPC MACARRY KIRD?OOD ERNSTCASE KNIGitT BALLARDIIINAITER sit!WEIL OPERATING REACTORS SPANGLERHARLESS PAWhLCXI STELLO

SITE TEC11.PF0 JECT MANAGEMENT REACTOR SAFETY OPERATING TECli. Calli 1LLBOYD / ROSS EISEN!!UT _ _STEl'PP._ COLLINS / NOVAK SILAO IlUL!!ANll0USTON / ROS.7TOCZY BAER3

PETERSON CllECK BlJrl.Eg SITE ANALYSISHEl.TZ / L . C v o t. M GPWirS VOLL]ERa .

liELTEMES AT_&__I / f' (4), / / # a e 3 BUNC11 1

SKOVHOLT SALTZMAN J. COLLINSRUTBFRG I KREGER

EXTEHN AL DISTRIBU TION CONTROL NUMSE RLLPOR:C ry 3 ta j kau,fIA NAL_.LABJ BR00X11AEtLI AT. LAN/., TI_CJ REG V.IE ULRLKSON (ORNL)/ NSIC: TA PDR

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/OO(Ar5SLB: CONSULTANTS: _ *7 ) o[AM Slb CYS Hetswer ,E:. T 43 c.nr o a/, in ii o a 1 a o i < oc >

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N C r J RM 105 (2 76)

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E.JCOOk Er. V.ldCOX'

power cenerat:en cecuo~

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P.O. Box 1260. Lp:2.tura. Va. 24',C5,

Telep$ione:(804)3s4 5111.

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January 24, 1977.

.

.

Mr. S. A. Varga, utiefLWR Branch #4Division of Project ManagementOffice of Nucicar Reactor Regulation ,

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U.S. Nuclear Regulatory Commission.

Washington, D.C. 20555f

* Reference: D. F. Ross December 2, 1976 Ictter to K. E. Suhrkeon B4W ECCS Evaluation Model.

.). -

Dear Mr. Varga:-

A revision to B5W's ECCS Evaluation Model is proposed -

herein which addresses the NRC Staff concern regarding theuse of a nucleate boiling heat transfer correlation during.

blowdoun af ter critical heat flux (CHF) is first predicted.This proposed revision supersedes the revision submitted-

in our letter of Decemaer 16, 1976 from K. E. Suhrke toS. A. Varga. We believe this revision adequately addresses

-NRC concernd with the information provided in.the. December 16, 191; submittal. .

Your expeditious review and approval is requested toensure an orderly progression of licensing and startupactivities in plants utilizing the B6W NSS. Following

-

. approval, we will incorporate the change into TopicalReport BAW-10104A, Rev. 1, "B6W's ECCS Evaluation Model."

We would be willing to meet with you to discuss thischange at your convenience. If you.have additional questions,pledsc contact H. A. Bailey of my staf .

g. 3.

Very truly yours, j.. ..

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Kenneth E. Suhrke I.

Manager, Licensing.

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cc: ?.oltan it. Ron:toeny (NRC)hT. 11. Novah (.'!RC) -

J. Angelo (NRC) 1D

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J. F. Stol: (NRC) -

R. B. Borsum (BGW).j

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lho Datrock & Wilcoi Cem;uny / Cot.iblished 1667-

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1. Introduction .

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It has been determined by.fiRC Staff that the post-CHF heat transfer

calculations performed in the BDI THETA 6F computer code r6ay not be consistent ,

with the requirements set orth in Appendix K of 10 CFR 50. In particular,

the calculation of local heat transfer by nucleate boiling subsequent to the *occurrence of CHF as is performed in THETA 6F was considered questionable. An

investigation was undertaken at BMI tc. establish an alternate post-CHF heat ,,

transfer model for implementation in the THETA code. The scope of resulting.

nodifications to be proposed includes both revisions of the post-CHF switchinglogic and eliminatiori of the post-CHF return to nucleate boiling.

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2. THETA Code 1,4odification . - .. .

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. "If departure from nucleate boiling (DNB) has been calculated to have. ,

. occurred for a particular axial node, both transition flow boiling and nucleate_

bailing will be. calculated; the lower heat flux is useEl." Examination of the~

THETA 6F switching logic showed that the,ccmparison of transition. boiling heatflux to nucleate boiling heat flux was not made. Rather, referring to Figure 1,

2'a trial value of.the heat flux was calculated for a particular axial noda. .

according to the fluid void fraction.'

%. .

| for: 01ai.80 nucleate boiling (mode 2) .h'

.80 < a < .90 interpolation between nucleate boiling (mode 2) andforcedconvectionvaporization(mode 3). .- .

1. 90 l a < l.0 ' forced convecticn vaporization -

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If the trial heat flux was less than CHF, the trial value was taken as the -|' local heat flux. If the trial value exceeded CHF, transition boiling (~.ede 4) -]

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. heat flux was used. To correct this, the post-CI:F switching logic was r: edifiedso th'at subsequent to CHF at a particular axial node, regressica on the -

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, transition b' oiling curve is restricted to heat fluxes (1) less than CMF for ,1

" loc'al fluid void fractions less than 80 percent, (2) less than the heat flux. calculated by interpolation between nuciente boiling (meda 2) and forced -

convection vaporization (mode 2) for local void fractions between 80 cercent-

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4. Spectrum Studies .

The validity of the Spectrum Analysis results and trends reported inReferences 3 and 4 was demonstrated by re-analyzing the worst soectrum case for

each of,these two plant categories. The results of this're-analysis are,

presented in Table 2. For both cases, the hot spot peak clad temperature

. increased less than 20 F. Since the worst spectrum cases were reanalyzed, th.e

peak clad temperature increases should provide an coper bound for all other

spectrum cases. Hence, the spectrum results and trends in References 3 and 4

are still valid. Furthermore, since the spectrum trends in Reference 2 are

basically the same as those in References 3 and 4 and since the THETA analysesfor the worst spectrum cases in References 2,3, dd 4 all proceed in a similarnanner, the spe:trum results :and these presented in Reference 2 should also stillbe valid.

5. LOCA Limits Studies *

The final modification (Case 5) presented in Reference 1 showed *

:no significant impact on the LOCA limits presented in References 2,3, and 4.TXis lack of impact is due to the fact than in these base LOCA limit cases

-(those presented in References 2,3, and 4) minimal time is spent in transition--boiling and oscillating between transition and nucleate boilina type heat,

fluxes. By approximately 0.5s the ruptured and the hot spot nodes are locked" int _o film and/or film pool boiling by virtue of the 300 F temperature difference

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criteria. Hence, for the THETA code modification presented herein,(Section 2),eno impact on the LOCA limits should be evidenced.

During the course of this THETA code modification program it was determinedv

that by evaluating the ruptured and unruptured node temperature differer.ces j,

dbdified - Tbasecase) nce the forced convection to superheated ster.n coolir.g .;

Mode (code 8) was established (sl3s) an accurate determination of the final l

'cffect on peak clad temperatures,can be made. Of fact, the Ats at approximately'13s translate one to one relative to the peak clad temperatures of the basecases. Use of the method allows an accurate deternination of the ruptured I

and unruptured node peak clad temperatures by executing cases on acdificd THETAversions to only 15s. This method is restricted by assuring that significtnt

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tiode 2: Nucleate Eoiling 't'

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Mode 5: Flow Film Boiling .-

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Mode 7: Fool Film Boiling -

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Case 1 '. 2-,

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Version . Original 6F THETA 6 CY=1

Post-CHF -

Old llew-.

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Switch Logic (ifodi5"or3) , (Mo'de4)~~~

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Returnable Modes ~ - "

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Ruptured flode (Base) (+67 F)~0Peak T F 1992 202g .. .... . . . . .' * ' ' - Unruptured !!ade -' (Base) ' - (+31 F)

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Elevation[Tsic81 Ft. IMde Case Hodified 1. ~g , g .

1 1316 1317 +12 1531 1531 03 1645 1645 0

MV.10103 2 Clad 4(ruptured) 1530 1530 0Fef. 02 5(hot spot) M70 1670* 0

6 1645 1645 0.

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7 1544 1547 +31 1402 1402 0

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2 1667 1667 0.

3 1024 1824 0Fuel 4 1950 1950 0

5 1872 .1871 -16 1847 1847 .- 0

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7 1757 1761 +41

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1659 1658 01687 1687 0

3(ruptured) 1693 1698 0.

. .__------6 Clad 4(hot spot) 1698 1699 +1,5 1691 1692. +1

6 1675 1676 +17 1644 1644 0

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1 1855 1855 0 .2 1885 1885 0

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3 1893 1893 0 .

Fuel 4 18E5 1883 ~ 425- 1871 1872 +16 1843 1844 +17s

__1792 1792 0

1- 1291 1291 02 1591 1591 0-

3 1763 1764 +1BN4-10105, 2 Clad 4(ruptured) 1843 1847 -1-

P.cv. 01 5(hotspot) 1832 1832 0.

6 1751 1752 . +17 1685 1689 +31 1373 :1373 0

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2- 1688 1688 0.

3 1859 1869 0-

Feel 4 1953 1958 05 1933 1930 06 1854 1854 0 -

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7 1785 1789 +3- --- 1 1553 1550 +7

2 1651 1651 0,

3 1657 1559 +2.'

6 Cird 4. 1674 1676 +2

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6 1652 1654 +2-. .'5 1655- 1563 +2

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7- 1625 1025 0.-

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