NRC-84-0077, Responds to Request for Addl Info Re Proposed Rev of Diesel Generator Start Time from 10 to 12 S.Evaluation of Burst Blockage Penalty for Snupps Plants Encl

Responds to Request for Addl Info Re Proposed Rev of Diesel Generator Start Time from 10 to 12 S.Evaluation of Burst Blockage Penalty for Snupps Plants Encl

ML20084H307
Person / Time
Site:	Wolf Creek, Callaway, 05000000
Issue date:	05/02/1984
From:	Petrick N STANDARDIZED NUCLEAR UNIT POWER PLANT SYSTEM
To:	Harold Denton Office of Nuclear Reactor Regulation
References
SLNRC-84-0077, SLNRC-84-77, NUDOCS 8405080011
Download: ML20084H307 (6)

Text

_

s SNUPPS Standerdised Nuoteer Unit Powee Plant System

' 2"" ecut we b e May 2, 1984 SLNRC 84- 0077 FILE: 0278 SUBJ: Revision in Diesel Generator Start Time Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Docket Nos. STN 50-482 and STN 50-483

References:

1. SLNRC 84-0069, dated 4/17/84: Same Suoject

2. SLNRC 84-0071, dated 4/23/84: Same Subject

Dear Mr. Denton:

Reference 1 submitted information supporting the acceptability of an emergency diesel generator start time modification from 10 seconds to 12 seconds for the SNUPPS plants, Callaway Plant Unit No. I and Wolf Creek Generating Station Unit No.1. Reference 2 provided additional inform-4 tion resulting from a comparison of the SNUPPS ECCS evaluation model to the more recent,1981 evaluation model.

Based on a review of References 1 and 2, the NRC staff requested addi-tional information regarding the burst blockage penalty in the 1981 evaluation model. The enclosure provides the evaluation of the burst blockage penalty for the SNUPPS plants and shows that this penalty, when combined with the benefits from using improved analytical and modelling techniques (Upper Head Injection plant technology in the 1981 ECCS evaluation model), gives a net peaking f actor benefit of 0.16. This peaking f actor benefit of 0.16 was translated as a benefit of 160'F in the Reference 1 evaluation and along with the 15'F benefit in peak clad temperature from the reduction in initial pellet temperature modelling change, support the not peak clad temperature margin of 200*F to the 50.46 criteria for the SNUPPS plants, if there are any questions, please do not hesitate to call us.

Ver uly yours,

1. ~

-4t % c

{ Nicholas A. Petri (ck cc:

a n See Page 2 SEko!

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4 SLNRC 84- 0077 Page 2.

D. F. Schnell UE cc:

KGE G. L. Koester

! D. T. McPhee KCPL 1 J. Neisler/B. Little USNRC/ CAL W. Schum/A. Smith USNRC/ CAL

' B. L. Forney USNRC/RIII ,

E. H. Johnson USNRC/RIV l L ,

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Enclosure to SLNRC 84-0077

A. Evaluation of the potential impact of using fuel rod models pre-

, sented in draft NUREG-0630 on the Loss of Coolant Accident (LOCA) analysis for SNUPPS (SNP).

This evaluation is based on the limiting break LOCA analysis identi-fied as follows:

BREAK TYPE - DOUBLE ENDED COLD LEG GUILLOTINE BREAK DISCHARGE COEFFICIENT 0.6 (Max. SI)

WESTINGHOUSE ECCS EVALUATION MODEL VERSION FEBRUARY 1978 CORE PEAKING FACTOR - 2.32 HOT R03 MAXIMUM TEMPERATURE CALUCLATED FOR THE BURST REGION OF THE CLAD - 1941.36 F = PCTB ELEVATION - 6.0 feet HOT R0D MAXIMUM TEMPERATURE CALCULATED FOR A NON-RUPTURED REGION OF THE CLAD - 2174.220F = PCTN ELEVATION - 7.5 Feet CLAD STRAIN DURING BLOWDOWN AT THIS ELEVATION 2.43 Percent MAXIMUM CLAD STRAIN AT THIS ELEVATION - 2.43 Percent Maximum temperature for this non-burst node occurs when the core reflood rate is (LESS) than 1.0 inch per second and reflood heat transfe'r is based on the (STEAM COOLING) calculation.

AVERAGE HOT ASSEMBLY R0D BURST ELEVATION - 6.0 Feet HOT ASSEMBLY BLOCKAGE CALCULATED - 46 Percent I. BURST N0DE The maximum potential impact on the ruptured clad node is expressed in letter.NS-TMA-2174 in terms of the change in the peaking factor limit (FQ) required to maintain a peak clad tem-of 22000F and in terms of a change in PCT at a peratureFQ.

constant (PCT)Since the clad water reaction rate increases sig-nificantly at temperatures above 22000F individual effects.

(such as delta PCT due to changes ~in several fuel rod models) indicated her: 1ay not accurately apply over large ' ranges, but a simult u nus change in FQ which causes the PCT to remain in the neighborhood of 22000F' justifies use of this evaluation procedure.

s

Enclosure to SLNRC 84-0077 l -

Page 2.

From fiS-TUA-2174: .

For the Burst Mode of the clad:

0.01 AFQ -- < 150 F BURST NODE APCT p/ .Me eevaed' Wc' r6y Asu.ie bor r/ mo de /

- Use of the NRC burst modelg could r'equire an FQ reduction

. of 0.02.7 .

.!. ..- ..i .

- The maximum estimated impact of using the NRC strain .

model is a requi. red FQ reduction of 0.03.

Therefore, the maximum penalty for'the Hot Rod burst node is:

APCT1 = (0.02T+ .03) (1.500F/.01) = 8550F Margin to the 22000F limit is:

APCT2 = 2200.0F - PCTg = 4259. 4 oF The FQ reduc ~ tion required to mafat'a~in"the 22000F clad tempera-ture limit is:

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0 '

^ bFQ0 '= (hP.CT  : . w. ..

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.-:- x- 9 9 .4 pp:y r -

= . 0398 ' (but not Tess than zero).

2. NON-BURST NODE The maximum temperature calculated 'for a non-burst section of clad typically occurs at an elevatiori above the core mid-plane during the core reflood phase of.the.LOCA tranfient. The potan-

~

tial impact arr that maximum cTad temperature of using the NRC

' fuel rod mordeTs. can .be estimated'.by examining two aspects of the

~ ~ anaTyses~. 'The first aspect is' the change in pelTet-clad ga;r

.. conductance resul. ting frcm a. difference irr clad strain at the non-burst maximum.clai temperature. node elevaticrr. Note that clad' strain aTT aTong. the- fuer rod sto;:s after clad burst occurs -

,, ;and. use .of a. differant: clad burst model can change the time at which bur'st .is calcuTated. Three sets of LOCA. analy' sis results were studied to establisir ari acceptabTe sensitivity tc apply generically in this evaTuation. The pos-ible PCT increase resulting fred a chance.frr stca.irt (in the Hat Rodl is 40.0F per percent decriisei frs'.stfain,at. the. maximum ciad' . temperature.

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~4nce the clad strain calculato tcur 1nc :M =ccour locatio's. is ni,: : an ed by

. Enclosure to goo int lys blowdown phase c' the accic

ad SLNRC'84-0077 the .se ;f NRC fuel rod models, the maximum decrease

. Page 3. stra'n :. at must be considered -ere is the differer:s :t: ween '

the ' a: ura clad strain" and - .e " clad strain at :ne i of RCS '

blo,.:ow ' indicated above.

Ther sfe-s:

0 iPC

.2

= (20 F.01 strain ) (MAX STRAIN - BLOWDOWN 5 RA:i,

=( ) (2,+3 - g)

- O The sec:nd aspect of the analysis that can increase : is the ficw s.:cxage calculated. Since the greatest value :' : lockage indf:a ic by the NRC blockage : del is 75 percent, nt aximum PCT inc sase can be estimated y assuming that the :;-snt level of :lo:: age in the analysis (ir.dicated above) is raist: :o 75 percin: and then applying an a:oropriate sensitivity #:- tula showt - NS-TMA-2174.

Therefo s, iPC 4 = 1.250F (50 - PERCE. T-NCURRENT BLOCKAGE',

+ 2.360F (75-50)

= 1.25 (50 - 4 (o ) + 2.36 (75-50)

= d4 0F .(67.99 6: .$~

If .CTN :ccurs when the core reflood rate is grea:a - :. ease an 1.0 inc. or second APCT4 = 0. The total potential PC for nt on-burst node is then 9' .T = APCT3 + APCT4

M Mar;i  : the 22000F limit is .

19:~6 = 22000F - PCTn : JLW The C s:uction required to tintain this 22000F :'i: am-pera ;-i *imit is (from NS-TP -Il74)

- aro

~

v4 9 = (APCTS - aPCT I 6 ) ' .;;F APCT dQg = . 0 3ti2- but n:: less than Isrc.

l e

s.-

, y' . Enclosure to SLNRC 84-0077 7 * .

Page 4.

/*

l J,e pt.%ir.g factor reduct'cn r: wir d to .mn'.ain the 2~ 0 F clad tcmperature limit is therefcce the greatcr of L. FOB '"df70H '

or; A FQPEHALTY "

0 0 '

B. The effect on LOCA -analysis results of using improved analytical and modeling techniques (which are currently approved for use in the  ;

Upper Head Injection plant LOCA analyses) in the reactor coolant system blowdown calculation (SATAN.ccmputer code) has been quanti-fied via an analysis which has recently been submitted to the NRC for review. Recognizing that review of that analysis is not yet complete and that the benefits associated with those model improve-ments can change for other plant designs, the NRC has established a credit that is acceptab.le for this interim period to help offset penalties resulting from application of the GRC fuel rod models.

That credit fcr two, three and four loop plants is an increase in the LOCA peaking f actor limit of C.12, 0.1.5 and 0.20 respectively.

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C. The peak'ing factor limit adjuh%ufred.to justif' plant y ..b.-

operation for this ~ interim *p.er] . iiir.rined-asbthe'.apprep.rfated)E-Y --

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. AFQ credit identified in .secti -iBoves..'miniis s theb.FQ calculated in section (A) abovE

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