ML20133N535

Summary of 850808 Meeting W/Util in Bethesda,Md Re Proposed Revs to ECCS Codes & Input to Assure Compliance w/10CFR50.46.Agenda & Viewgraphs Encl

ML20133N535
Person / Time
Site:	Yankee Rowe
Issue date:	10/22/1985
From:	Clifford J Office of Nuclear Reactor Regulation
To:	Office of Nuclear Reactor Regulation
References
NUDOCS 8510290554
Download: ML20133N535 (98)

Text

1. g ung'o ~g UNITED STATES 8 o NUCLEAR REGULATORY COMMISSION g WASHINGTON, D. C. 20555

.. j October 22, 1985

\....+

Pccket No. 50-29 LICENSEE: Yankee Atomic Electric Company FACILITY: Yaakee Nuclear Pcwer Station

SUBJECT:

MEETING

SUMMARY

- MEETING WITH Y/ECO Off FCCS CODE REVISION A reeting was held betweer Yerkee Atomic Electric Company (YAECc) and the NRC staff to discuss proposed revisions to tFe ECCS codes and code assumptions for the Yankee plant. The meeting was held in Eethesda, Maryland on Aucust 8,1985 at the request of YAECo. A list of attendees is provided in Enclosure 1. The meeting agenda and objectives are provided as Enclosure 2.

After a brief introduction by the NPC and YAECo project managers, the

- licensee provided discussiers rcgarding the reasons for the current reevaluation of the Yankee ECCS codes, the Yankee plant characteristics, the core flux shapes and associated uncertainties, the history of the Yankee ECCS code development, and proposals for modifying the ECCS codes and input assumptions to assure continued empliance with 10 CFR 50.46. A more detailed discussion of each of these presentations is provided in the following paragraphs. The handouts used for these presentations are provided in Enclosures 3 cnd d.

In its introduction, the licensee explained that it was infomed in tre Spring of 1985 that the axial power shapes it had been using for ECCS analyses may no longer be acceptable to the NRC staff. Specifically, the cosine shaped axial power shape had been questioned. The licensee explaired that it had taken action to linit flux in the upper core region by operating with a rodded core which ensured a bottom-peakad pcwer distributier. This provided assurance that Yankee remained in compliance with 10 CFR 50.46 while the ECCS analysis rethods were being reviewed. The desirebility of operating the Yankee core in a rodded condition was discussed.

since this is not the nomal operating mode for Yankee. The licensee and the staff also discussed the likelihood that the staff's concern fcr corpliance with 10 CFR 50.46 was not a safety issue due to the conservatisms that the licensee felt existed in the Yankee ECCS codes. A nore dctelled discussion of the code conservatisms was provided by Yankee later in the meeting.

The licensee provided a discussion on the Yankee core power distributions (Enclosure 3). Following a description of the plant characteristics, the licensee described its calculated flux distributions for Cycle 18 (Enclosure 3, paces 5-8). The graphs show nominal flux distributions for various times in core life, and show the effects of xenon on the flux 8510290554 851022 PDR P

ADOCK 05000029 PDR

distributions. As sFewr en page 8 of Enclosure 3, the calculated xenon transient induces a top-peaked power distribution late in core life. In response to a staff ouestien, the licensee explained that load-following calculations for xenon transient evaluatico were performed at full-power steady state conditions, with Technical Specification (TS) limits that require the plant to be held at a reduced power following a power transient to limit the effects of the xenon trersients if the rods are outside the rod insertion limit shown on pages 3 erd 19 of this enclosure. Tha licensee then described the self-darping characteristics of tbc xeron transient following a rod-induced power transient (Enclosure 3, pages 9 cnd 10).

The licensee then provided the NRC staff with a comparison of actual measured flux levels against calculated levels to show that the current codes estimate flux levels within approxiretely 1%, except at the outermost regions of the core. The correrison was provided for the current and previous cores (cores 17 and 16). Graphs of calculated versus actual axial flux distributions are providad on pages 17 and 18 of Enclosure 3, which show a close corparison between calculeted and actual axial flux.

The licensee provided a discussion of the administrative centrols currently in place at Yankee to provide assurance that the requirements of 10 CFR 50.46 are met with the currert code for Cycle 17. The licensee has added administrative controls to limit control red neverent which limits power levels in the upper core reoion to limit any top peaked power distribution.

In addition, current TS have a restriction on how soon after a power reduction the core can be returned to full power if the rod heights are outside the rod insertion limit, and there is a restrictict on rod reactivity transient rates. Ecth cf these TS restrictions serve to limit the effect of xenon transients on the axial flux distribution. The licensee has stated that the additieral restriction on rod withdrawal limits will remain in effect until reaching 801 power during the power coastdown. Cerpensation for xence trensients will be accomplished using boron, to keep the rods within the administrative restrictier.

l To show the effects of operating with a redded core, graphs were provided l

~

shewing the axial flux distribution with and without the rod restriction, at two times in core life (page 20, 21, Enclosure 3). Page 22 (Enclosure 3) shows the effect on xenon transierts with and without the rod restriction.

The graphs point out that the flux distribution is botton-peaked with the rodded core, which has the plant within the criciral analysis assumptions for cycle 17 operations. The graph on page 23 (Enclosure 3) further sijows the effect of reactivity rates on the axial power distribution, which points to

! the reason for reirteining the TS limits on reactivity rates.

The licensee then provided infomation regardire the conservatisms in the LOCA limits of Linear Pret Generation Rate (LPGR) vs. core burnup. The licensee presented information regarding conservatisns that exist in the Xenon Redistributier Factor (Fxe) and the Rod Insertion Factor (Fi). The licensee also discussed three other factors (the Feasurerent Uncertainty (Fu), the Power Uncertainty (Fp), and the Engineering Factor (Fe)) in the TS LHGR limit. The licensee proposes to combine these three factors i statistically, es opposed to the current method of combining them multiplicatively, as discussed on page 27 of Enclosure 3. The NRC staff

stated its belief that based on the information presented in the meeting, statistically ecmbining the three factors (Fu, Fp, and Fe) should be acceptable. The NRC staff stated that the licensee shculd provide its justificatier fer this proposal to allow for TRC staff review.

The next three slices (peges 28-30, Enclosure 3) shov inferration regarding the integratico cf boren dilution with control rod motion, to support the Yankee proposal to use nominal flux shapes in its calculations, cs opposed to the current approach of usin The slide on page 30 (Enclosure 3)shows g the the xenon-induced difference influx axialshapes.

flux shapes for the nominel erd xenon shapes, and shows a bottom-peaked power distribution for the nominal case, and a top-peated distribution for the yeror ccsc.

Fclierire the presentation, the NPC staff pointed out that the normal analysis assumptions consider TS allowable transients (i.e.. if TS allow red rotion between 80-90 inches, the analysis should use these limits).

in addition, the NRC staff stated that adninistrative controls may ret te afpropriate, but that the TS shculd be modified appropriately. The licensee provided the argument that the nominal approach is more like the vey the plant operates, and therefore should be used for the calculatters.

The NRC restated its position of using the limiting analysis for the licensing basis. On the issua of using a statistical combination of the uncertainties, the NRC staff stated that similar proposals from other lieprsees have been accepted, while others have not, on the merits of the individual cases. The NRC staff would need to look at the details cf the Verkre preposal. The NRC steff stated that the information to be provided by the licensee needed to include an apprcpriate data base, and to sber indererdence of the factors involved. Based on the infomation presented et tha reeting, the NRC staff felt that the Yankee approach to statistical ccmbination of uncertainties was appropriate, but that the staff veuld have te see the specifics before making its final determination.

The NPC staff then questioned the licensee regarding plans for renceirc Fi and Fxe frcr the LHGR calculations. The licensee felt that a bottom shaped flux distribution bounded the cosine curve, and Fi would not be nEeded in the celculction. In the consideration for Fxe, the current TS value for Fxe would be modified as a part of the cycle 18 reload submittal, erd the licersee is considering other restrictions (e.g., rod motion limits) that may eliminate the need for Fxe. As part of the reload submittel the licersee intends to make a case for eliminating the Fxe bottom mutiplier (page 26 of Enclosure 3).

, The licensee presented information releted to the LOCA analysis rethods

• thet are being investigated (Enclosure 4). The licensee explained the history behind the previous analyses performed up through cycle 17. The analysis for cycle 18 had been perfcrmed using the cosine shaped flux distribution, and the licensee exple. ired that the calculations would need to be re-performed based on the current NRC concerns. To complete the reanalysis, the models that are currently being used will have to be modified in order to remove the crerating rod withdrawal restrictions to allow operation without a rodded ccre. In 1975, the licensee had identified the Yankee models, exple.ining the differences between the Yankee model and the generic effort based en the Exxon model being used fer the H.L.

Robinson plant. Since Yarker ves using the cosine-shaped flux l

4-distribution, it used Fi and Fxe rutipliers to add additional conservatisni.

Since the initial code devclerment, a number of changes have been rade to the Yankee model as more knowledce or limitations in codes have been identified. The latest questicrs regarding the Yankee ECCS codes deal with conditions during the reflecd phase of the accident analyses (af ter the blowdown and refill phases beve ended). Based on the current concerns, e composite flux distribution was used te perfom the LOCA analyses. The composite distribution ircluded the most limiting of the ccsine and the physics-deterrired flux distributions.

The technical issue of concern in the reflood phase was to rot have the flux peak in the upper ccre region because of the time it took to raficod that region. In the previous analyses using the cosinc stered flux distribution, the flux peak was in the core nidplane, and as long as the peak remained a below this core midplane, the analysis using the cesire shape would be bounding. The currcnt analysis which identified a top-peaked power distribution led to rod withdrawal restrictions te provide flux suppression in the upper core region to obtcin a bottom peaked flux distribution, and therefore make the cosine shaped flux distribution again bound the actual flux distribution. Pace 6 cf Erclosure 4 shows the licensee's proposed cperating restrictions for the powcr ccestdewn phase of the operating cycle.

This page shews that rod withdrawal above the current restriction of 83 inches will be necessary. To allew for this, the licensee propcsed a rod withdrawal rate limit of less than or eaual to ? inches per day te ersure the analysis' peak centerline torporeture (PCT) remains less than 2200 degrees post-LOCA.

The licensee then provided a discussion of the cycle 18 erelyses that have been perferred to date. Page 8 (Enclosure a) shows the items the licensee is requesting regarding the model and analysis parameter changes for its roccl.

Ore of the issues shown deals with an injection delta-P penalty, which is e conservatisr ir.cluded in the model to account for pressure loss due to in.iectier parameters of angle and flow rate. The licensee is currently usino a 90

. decree ergle of injection, which results in a delta-P penalty of 0.8 psid.

With a modified model, the licensee proposes a delta-P pcrelty of 0.15 osid. The staff's initial impression is that there should not be any problem in grantirg a modification of the delta-P penalty, but the staff needs to evaluete the-licensee's calculations and assurptions before making a final decision.

l The NP.C staff questioned the approprieteness of using nominal power shapes in the licensee's calculations. The licersee uplained that it intends to I perfonn a series of power shere calculations, which are an extension of burnup sensitivity stucies, using calculated flux sheper., rot the TS limits. The licensee acknewlevoed that this approach needs to be justified. The TS would then be based en a calculation to allow operating rargin providing

for errors in calculations compared to measured flux levels. This extra margin has in past efforts resulted in calculatiors based on TS kW/ft limits to show possible problems in meeting Appendix K. The licensee had then proposed a single TS limit which would be limiting, er bounding, and be shown to he 14riting based on sensitivity studies. The staff pointed l out that the licensee's efforts to meet Appendix K would be helped by using a variabh limit er the kW/ft limit based on core height.

The licensee explained the differences between its analyses and the Westinghouse methods (which result in a variable kW/ft limits). The licensee explained that to show one kW/ft lirit, as opposed to a variable one,

, sensitivity studies are needed to show the limit is bcunding. The current Yankee kW/ft TS linits are based on cosine-shaped flux distribution calculations. The licensee is working on develepirg kW/ft TS limits based on a top-peaked flux distribution, and add a krown enount of conservatism.

for its variable kW/ft limits. Vestinghouse uses heicht-dependent flux (F delta H) lir.its fer departure from nucleate boiling (DhB) and hot channel calculations. These sane limits are used in the Westirchcuse LOCA calculaticrs. The Yankee model does not use F delte H in its LOCA rodel. The licensee does not feel there are any radial flux (Fxy) dependencies in the LOCA calculations, and therefore uses kW/ft instead.

It was also noted that Westinghouse shows rerpliance with Appendix K in pre-cycle calculations, while Yankee verifies conpliance throughout the cycle using actual measurements to compare to its calculations.

The licensee then explained that if the delta-P penalty rodification is i approved, there would be no need to benchmark the modified Yankee model, due to the nature of the charces. The licensee also pointed out that this change in its model would be a permanent chante. The licensee proposed to provide the changes tc tha redel as a separate enclosure to the reload package. The staff felt it would be more apprcpriate to provide the LOCA model changes in a separata letter, while at the same time use the rodified rodel in the cycle 18 submittal. The staff felt that Yankee had provided sufficient infomatier in the reeting such that the f!PC staff feels the change to the modal will be acceptable, perding confirmation of the information provided at the reeting. The licensee stated that if a problem with the cycle 18 analyses or the TS were to necer, the falloack position would be to rely on currert TS with rod restrictions.

The licensee stated that es it develops its final proposal, it may ask for additional conference calls or meetings te discuss its approach with the staff. This approach is acceptable to the staff. The licensee was asked to provide a letter of commitment, to irclude the bases for removing the current rod restrictions, irciuding any additional restrictions that may be necessary during the power coastvern, as discussed earlier in the reetir.g.

The licensee asked one additioral cuestion regarding whether the proposed modifications to the Yankee LOCA model would teve tc be prenoticed as a license amendment. The staff's position is that the proposed rodifications, other than the TS that result frcm the calculations, are of such a nature that the lictnte is not being modified, and therefore would nct require prenoticing.

TFe resident inspector noted that with the changes in operating restrictions proposed by the licensee, the Licensee Event Report (LEP) vould need to be rodified. The licensee agreed to submit a modified LER.

i

I l

l

, The teeting was adjourned. The staff took special note of the forthrici+

l cpproech presented by the licensee in this meeting, and also noted the i sound and timely technical efforts that have been expended by the lictr.ste l ir its investigations of the LOCA model.

b

,,wdd. 0! kA 1 t j Ja es W. Clifford, Project Marager Operating Reactors Branch No. 5 i

1

Enclosures:

! 1. List of Attendees I 2. Meeting Agerda

3. Core Power Distribution Handouts 4 - LOCA Analysis Methods Handouts i cc w/ enclosures:

See next page 1

4

+

l l-e i

_. ___-_- . _ _ _, _ _ _ , _ _ _ _ . _ , _ _ _ . _ . ~ . . _ _ . . _ _ . . _ . - , _ , . , _ , . . . , _ . . . . . . _ . - . - - _ ~ _ . . . . _ . - . _

j t

j -

'cc:

Mr. Janes E. Tribble, President Yankee Atomic Electric Company 1671 Worcester Poed Framingham, Massachusetts 01701 ,

! Thomas Dignan, Esquire  !

! Ropes and Gray i j  ??5 Franklin Street '

Boston, Massachusetts 02110 ,

Mr. N. N. St. Laurent Plant Superintendent i Yankee-Atomic Electric Company i Star Route

Powe, Massachusetts 01367

Chairran l Board of Selectmen

} Town of Rowe Powe, Passachusetts 01367 Pesident Inspector  !

- Yankee Nuclear Power Station i c/o U.S. NRC

! Post Office Box 28 j Monroe Bridge, Massachusetts 01350

) Fegional Administrator, Pegion I

! U.S. Nuclear Pegulatory Commission j 631 Park Avenue j King of Prussia, Pennsylvania 19406 1

4 l Robert M. Hallisey, Director

! Radiation Control Program  !

! Massachusetts Department of Public Health 150 Tremont Street, 7th Floor  ;

j Boston, Massachusetts 02111 t

i' Mr. Georce Papanic, Jr.

Senior Project Engineer - Licensing j Yankee Atomic Electric Company

1671 Worcester Poad Framingham, Massachusetts 01701 I

l l

l t

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ENCLOSURE 1 YAE Cc Re m3 Gde :

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l

ENCLOSURE 2 AGENDA YANKEE PLANT AXIAL POWER SHAPE MEETING 10:00 INTRODUCTION B. C. Slifer 10:15 CORE POWER DISTRIBUTIONS R. J. Cacciapouti

-Yankee Core Characteristics

-Typical Axial Power Shapes

-Xe Transients: Durations and Axial Shapes

-Cycle 17 Measured vs. Predicted Power Distributions

-Impact of Rod Program on Cycle 17 Power Shapes

-Core Power Monitoring

-Application of Uncertainty Factors

-Basis for Cycle 18 Power Shapes 11:15 LOCA ANALYSIS A. Husain

-Background Information

,, -Basis for Previous Analyses

-Axial Power Shape Discussions to Date

-Response to NRC Letter of May 22, 1985 i -Analysis for Cycle 17

-Analysis for Cycle 18

-Prospective Methods Improvements t -Axial Power Shapes i

I 12:00 DISCUSSION

\ .

-Cycle 18 Schedules BCS

-Basis for Cycle 18 Analysis 8/8/e

OBJECTIVES 1 To explain actions taken to assure compliance with 10CFR50.46 for Cycle 17.

2. To explain actions planned to assure c'ompliance with 10CFR50.46 for Cycle 18.

3. To obtain NRC feedback on a) basis for axial power shapes for LOCA analysis b) statistical combination of ur certainties c) injection AP penalty reduction

4. To discuss Cycle 18 schedules.

5. Time permitting, to discuss future LOCA methods improvements.

1 BCS 8/8/85

ENCLOSURE 3 l I

YANKEE ROWE CHARACTERISTICS POWER LEVEL 600 MWT NUMBER OF ASSEMBLIES 76 RODS PER ASSEMBLY 230/231 ACTIVE HEIGHT 7.5 ft.

CONTROL ROD TYPE CRUCIFORM NUMBER 24 c

GROUPS 4 MATERIAL Ag-In-Cd

L l

1 i

l CONTROL ROD CROUP IDEhTIFICATION

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32 33 34 35 36 3[ 38 29 30 31 '

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B A g o 56 , 57 55 52 53 54 55 49 50 51 D B B E 1 63 64 65 66 59 60 61 92 C D e .

69 70 , 71 72 67 68 D . .

73 74 75 76

' ASSDSLY POSITION #

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3 YANKEE CORE 17 POWER DEPENDENT INSERTION LIMIT 110 ,

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5 i CORE 18 TYPICAL RXIAL POWER SHAPES FRESH FUEL i 1.s -

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CORE 18 NOMINRL RNO XENON POWER PROFILES FRESH FUEL RT 14000 MWD /NTU ,

1.s '

a - NOMINRL SHRPE

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CORE HEIGHT (%) y

- - _ , - _ - ,, _ _ , . m .,___ __ _ . _ . . .s a , . _ _ _ . . ~ __

CORE 18 XENON TRANSIENT AT FULL POWER CORE AVERAGE FOR NODES 10 AND 3 -

1.6 .

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CORE RVERAGE FOR NODE 10 .

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(1 COMPARISON Of MEASURED VS PRE 0!CTED REACTION RATES

~

~

INCORE RUN YR-17-012 1337. MWD /MTU 599.7 MWT. GROUP C AT 83.8 INCHES R B C D E F G H J K

.990

.es?

3

.433

.981

.387

.506 1.015 1.003 3

.395 1 101 1 011 1.107 '

1 009 1 097 4

.220 .995 1 145 1 093 1.144 1 093 5 .047

.255 1.142 1 136 6 .518 1 115 1.019 1 115 1 004 7

.032 1 573 1 018 1 023 on 8

.. .453

.964 994 g .990 1 013

-3 997 -1 902 MER5URED

"3

0 x otrr

\ -- __

lL l .

l i l COMPARISON OF MERSURED VS PREDICTED REACTION RATES '

l INCORE RUN YR-17-018 l

6873. MWD /MTU 699 9 MWT. OR00P C RT 82.875 INCHES R B C D E F G H J K

.991

.997 g

-.017 e

.993 1 000 2 -1 996 1 029 1 019 3 .996

.790

' 1 024 1 104 1 014 1 094 4 1.019 .992 1 125 1.092 1 126 1 093 5 .008 .067 1 124 1 123

- .096 1 102 1.028 1 102 1 012

.023 1 572 1.026 i

- 1 024

.238

.983 .992

.980 1 005 g

i -1 320

_-2.564 MEASURE 0 PREDICT [0 10 x otrr l

1 I

- - - - . . - - . . ~ . , . - - - _ - - , __- __. -. , .___ _ - . . - - - - _ _ - -

13 COMPRRISON of MERSUREO VS PRE 01CTED REACT!0N RATES INCORE RUN YR-17-023 11840.0 MWD /MTU 699 0 MWT. OROUP C RT 82.126 INCH C D E F G H J K A B

.593

.701 g

-1 167

.990 t.009 2 -1 986 1 036 1 036

"3'

3 .664 .743 s.034 1 101 1 024 1 091 4 1 006 .384 1 110 1 000 1 107 1 006 5 .282 -.707 1 108 1 107 6 .000 1 094 1 037 1 094 1 024 7 .046 1 283 1.033 I.030 8 .304

.654 .992

.862 1 004 g

-1 189 -1 134 PLASURLD PRlotCil0 10 x otrr

l'l COMPARISON OF MEASURED AND PREDICTED SIGNALS INCORE RUN YR-16-013

~

599.9 MWT. GROUP C AT 85.0 INCHES 1172. MWD /MTU 0.605 0.0 14

-t4 SS t004 1.070

-1.450 1.016 1034 t029 t051

-t2 41 -1.663 t031 1.100 t051 t085

-t901 1.385 t084 tote 1063 t024 1.987 -0.482 t074 t063 t041 tt10 1.045 1.085 t051 2.3 11 -0.573 t045 t028 1.051 t020

-0.589 -0.058 0.462 1.084 WCASURID $1GN AL 0A46 1.079 PftCDICTED SIGNAL 2.444 0.404 POtCOff Dif7DENCC L

Ib COMPARISON OF MEASURED AND PREDICTED SIGNALS INCORE RUN YR-16-025 599.9 MWT. GROUP C AT 84.6 INCHES 6492. MWD /MTU

0. m 0.645 0.039 4030 1042

-1.188 1038 1042 1037 1047 0.%8 - 0.478 t040 1000 t047 t009

- 0.6 91 0.092 1077 1.040 t073 t040 0.3 91 0.020 t075 t073 0.196 1.090 1.001 t009 1.047 l

0.133 0.393 t042 t033 1047 1.037

-0.487 -0.283 0.046 1.040 WCAstJRED 50FAL 0.84 5 t042 PREDICTE $1GNAL 3.044 -0.91 POtCOff DIFTIRD4CC t

lb COMPARISON OF MEASURED AND PREDICTED SIGNALS INCORE RUN YR-16-035 12420. MWD /MTU 599.8 M%T. GROUP C AT 85.6 INCHES 0.689 0.666 3.505 1.023 1022 0.132 1045 10+6 1.042 1047 0.204 -0.097 t045 1.088 1.047 1.086

-0.M1 0.24 t044

?.078 1.075 1.049 0.3 T1

-0.494 t072 1.075

-0.287 1075 1045 1086 1.047

-0.991 -0.77 1.045 t029 1.047 1.042

-0.185 -1.2 41 WEASURED SIGNAL 0.662 1.013 1.022 PREDICTG SIGNAL 0.648

-0.802 PERCDU OlF7TAENCE 2.110 l

CORE 17 INCORE RUN 022 RT 10677 MWO/MTU .

CORE RVRERGE RXIRL POWER GROUP C RT 82 .

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80 90 100 0 10 20 30 40 50 60 70 _

4 CORE HEIGHT (%)

i CORE 17 INCORE RUN 023 RT 11840 MGID/MTU

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l CORE HEIGHT (%) *o l

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(0 YANKEE CORE 17 POWER DEPENDENT INSERTION LIMIT l 110 100 -

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CORE 17 COMPARISON OF RXIRL PROFILES RESTRICTED AND UNRESTRICTED R00 MOTION .

BURNED FUEL AT 10000 MWD /NTU 1*8 a - UNRESTRICTED o - RESTRICTED

1. 4 ,

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CORE 17 COMPRRISON 0F RXIRL PROFILES RESTRICTED RNO UNRESTRICTED ROD MOTION .

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CORE 17 COMPRRISON OF XENON RXIRL PROFILES RESTRICTED AND UNRESTRICTED ROD MOTION CORE AVERAGE RXIRL RT 12S00 MWD /MTU ,

1.s o - UNRESTRICTED o - RESTRICTED

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l l

CORE 17 COMPRRISDN OF RXIRL PROFILES y

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• l'l POWER DISTRIBUTION LIMITS TECHNICAL SPECIFICATION

- bx=F xy F, F u F,, F, F, F, Fx,2 F xy RADIAL POWER F, AXIAL PEAK -TO- AVERAGE F

u MEASUREMENT UNCERTAINTY (1.068)

F,, STACK SHORTENING (1.009)

F, POWER UNCERTAINTY (1.03)

~

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F, ROD INSERTION FACTOR l F,x MONEQMNWBWMG@

l AVERAGE KW/FT l

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17  :

l STATISTICAL COMBINATION F

u MEASUREMENT UNCERTAINTY (1.068)

F, POWER UNCERTAINTY (1.03)

F, ENGINEERING FACTOR (1.04)

~ .

MJLTIPLICITIVE (1.144)

STATISTICAL (1.084) l l

l

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LS CORE 18 BASIS FOR POWER SHAPE I

I NOMINAL XENON INDUCED ,

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ENCLOSURE 4

>8 . YANKEE LOCA METHODOLOGY i

l ORIGINAL l 0 XN-75-41 VOLUMES I TO Ill AND SUPPLEMENTS 1 TO 7 1

SEPTEMBER 11, 1975 0 GENERIC SER ON H B ROBINSON 0 YR SAMPLE PROBLEM XN-75-41 APPENDIX C

CH0PPED COSINE POWER SHAPE USED i

0 YR SER DECEMBER 4, 1975 APPLICABILITY OF 6ENERIC METHOD SPECIAL REVIEW OF SHORTER CORE, IHINNER FUEL ROD, DIFFERENT ACCUMULATOR CONFIGURATION GENERIC MODEL CONSERVATIVELY COVERED MODEL CHANGES AT YAEC 0 REVISED CALCULATION OF E0BY 3/77 O LOW FLOW FILM BOILING HTC 6/77 0 CORE FLOOD RATE STABILIZATION 7/77 0 LOWER PLENUM PHASE SEPARATION MODEL 11/80 0 RELAP5YA METHOD DEVELOPMENT (IN PROGRESS) l l

i i

I . _ . -. - ._. -

Z-AX1AL POWER SHAPE DISCUSSIONS i

i 0 MARCH 29, 1985 (CALL FROM NRC)

EXXON CONCERNS APPLICABLE TO YANKEE PLANT YP USES COSINE POWER SHAPE YANKEE WILL ASSESS POWER SHAPE IMPACT l

0 APRIL J ,1985 (CALL FROM YANKEE)

ACTUAL POWER SHAPE FLAT AT E0C I

- ACTUAL PEAK 8.2 KW/FT; ANALYZED PEAK 11.2 KW/FT AT 80% ELEVATION; ACTUAL KW/FT)> ANALYZED KW/FT EXISTING COSINE T00DEE-2 RUN REANALYZED WITH ACTUAL POWER SHAPES AT HIGHER blEVATIONS.

U PCT <[2200 F NRC TO CALL BACK FOR MORE INFORMATION, IF NEEDED.

i I,

YRNKEE CORE 17 RXIRL SHAPE COMPRRISON HOT FULL POWER, 8000 MWD /MTU 15 o - LOCR (INFERRED) o - PHYSICS DESIGN 12 -

P 9- e

• e o k c -

m

=

] 6-3-

i t ,

0 ,. .. ... , .,_ ... ,. , ,

0 10 20 30 40 50 60 70 80 90 100 PERCENT OF CORE HEIGHT u i

YANKEE CORE 17 RXIRL SHAPE COMPRRISON HOT FULL POWER, 12500 MWD /MTU

o - LOCR (INFERRED)

! o - PHYSICS DESIGN i .

I 12 -

i 4 l

D h

9-i N r

M =' c a c -

i e en 3 e-i l

! s-l l

0' ... ... ... ..

, 0 10 20 30 40 50 60 70 80 90 100 l PERCENT OF CORE HEIGHT -t_

b CYCLE 17 REANALYSIS ACTIVITIES Futt POWER O P E R_AI LQN 0 XE INDUCED IOP SKEW POWER SHAPES MAY LEAD TO DERATE r

0 EXISTING LICENSING ANALYSES WILL COVER BOTTOM SKEWED POWER SHAPES 0 RODDED OPERATION WILL FORCE BOTTOM SKEWED POWER SHAPES 0 PLANT WAS ORDERED TO INSERT RODS (80" TO 83")

t 0 BOTTOM PEAK WITH IECH. SPEC. LIMIT OF 11.2 KW/FT

^

on WAS ANALYZED 0 PCT < 2200 F I

l

b

- POWER COAST DOWN ANALYSIS "O rod WITHDRAWAL BEYOND 83" REQUIRED 0 PCT < 2200 F, IF POWER ( 85%

rod WITHDRAWAL RATE f 2" PER DAY O

~7 INJECTION AP PEN ALTY i

~

i  !

O CURRENT MODEL (BASED ON XN-75-41) i A P PENALTY

ANGLE OF INJECTION WITH Acc. WITH PUMP f 90 1.8 0.8

! 75 1.5 0.35 0 0.4 0.35 60 l 45 0.6 0.30

.I i

! 0 XN-NF-78-30 MODEL I

i i

l BASED ON 1/14 AND 1/3 SCALE TEST l - A P = 0.15 PS I D i

GENERIC APPROVAL SER 3/30/79 i

! O A P = 0.15 PSID APPLICABLE TO YP i

, s l

l l- . - _ . _ _ _ . . _ _ . _ . _ _ _ _ _ _ . _ _. _ . _ _ . _ _ _ _ _ _ _ _ _ , _ _ _ _

3 l

~

CYCLE 18 ANALYSIS WANT Av01D POWER DERATE Av0to UNWARRANTED OPERATING REETRICTIONS SER BEFORE PLANNED PLANT STARTUP NEED NEAR IERM MODEL CHANGES l

INJECTIONd6P PENALTY STATISTICAL COMBINATION OF UNCERTAINTIES i

USE OF NOMINAL POWER SHAPES CHANGE IN F XE AND F, TECH. SPEC.

l l

l l

l

- ~~ -

e f

3 I I i ,

ly .

I 0.2 ..

Upper Bound _

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~

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. 1 A4 Scale Data t

• 1/3 Scale Data . . x m

i

• i i i  ! 1 . x

-0.3 0.6 0.7 T 0.2 0.3 0.4 0.5 w 0 0.1 pV 2  ?

5 w

INLET STEAM DYilAMIC HEAD, 29 o

. m 4

f!C.tlRE 2.3 PRESSURE LOSS DUE TO PUMPE0 SAFETY INJECTION t - - - - - - _ _ . _

l

, . -6_ 0012 2 EB5 4

The meeting was adjcurned. The staff took special rote of the forthright approach presented by the licensee in this mentirg, and also noted the i sound and timely technical efforts that have bear e.vrerded by the licensee t in its investiget.icos of the LOCA model.

Original sisad br James V. Clifford, Project Manager Operatino Peacters Eranch f;o. 5 Erclosures:

1. List of Attende.es T. Peeting Agenda

. Cere Pcwer Distribution Handouts 4 LCCA Analysis Methods Fandcuts cc v/crclosures:

See rext page DISTRIBUTION

' Docket File.

ORBE5 Pdg CJamerson JClifford JZwolinski NRC PDR Local PDR 0 ELD Edordan BGrimes ACRS(10)

HRC Participants DL:0RBh5 DL 5 DL:0RD CJar:erson JClifford:tm J7wnlirski 10/p /85 10//6/85 10/g1/85

1. o g UNITED STATES E o NUCLEAR REGULATORY COMMISSION g p WASHINGTON, D. C. 20555 October 22, 1985

\ . . . . . .o pccket No. 50-29 LICENSEE: Yankee Atemic Electric Company FACILITY: Yaakee Nuclear Pcwer Station

SUBJECT:

FEETING

SUMMARY

- MEETING WITH Y/ECO ON FCCS CODE REVISION A reeting was held between Yankee Atomic Electric Company (YAECc) and the NRC staff to discuss proposed revisions to the ECCS codes and code assumptions for the Yankee plant. The meeting was held in Eethesda, Maryland on Aucust 8,1985 at the request of YAECc. A list of attendees is provided in Enclosure 1. The meeting agenda and objectives are provided as Enclosure 2.

After a brief introduction by the NPC and YAECo project nanagers, the

! licensee provided discussiers rcgarding the reasons for the current reevaluation of the Yankee ECCS codes, the Yankee plant characteristics, the core flux shapes and associated uncertainties, the history of the Yankee ECCS code development, and proposals for modifying the ECCS codes and input assunptions to assure continued cmpliance with 10 CFR 50.46. A more detailed discussion of ecch of these presentations is provided in the following paragraphs. The handouts used for these presentations are provided in Enclosures 3 and 4 In its introduction, the licensee explained that it was infomed in the Spring of 1985 that the axial power shapes it had been using for ECCS acelyses may no longer be acceptable to the NRC staff. Specifically, the cosine :haped arial power shape had been questioned. The licensee i explaired that it had taken action to limit flux in the upper core region by operating with a rodded core which ensured a bottom-peakad pcwer distributier. This provided assurance that Yankee remained in compliance with 10 CFR 50.46 while the ECCS analysis methods were being reviewed. The desirebility of operating the Yankee core in a rodded condition was discussed, sirce this is not the normal operating mode for Yankee. The licensee and the staff also discussed the likelihood that the staff's concerr. fcr ccrpliance with 10 CFR 50.46 was not a safety issue due to the conservatises that the licensee felt existed in the Yankee ECCS codes. A nore dctriled discussion of the code conservatisms was provided by Yankee later in the i reeting.

i The licensee provided a discussion on the Yanker. core pcwer distributions (Enclosure 3). Following c description of the plant characteristics, the

, licensee described its calculated flux distributions for Cycle 18

! (Enclosure 3, paces 5-8). The graphs show nominal flux distributions for various times in core life, and show the effects of yenon on the flux l

l l

1 i

l t

i distributions. As shewr en page 8 of Enclosure 3, the calculated xenon transient induces a top-peaked power distribution late in core life.

In j response to a staff ouestien, the licensee explained that load-followirg calculations for xenon transient evaluatfor were performed at full-power 4

steady state conditions, with Technical Specification (TS) limits that  ;

} require the plant to be held at a reduced power following a power transient i to limit the effects of the xenon trerrier.ts if the rods are outside the rod i insertion limit shown on pages 3 rrd 19 of this enclosure. Tra licensee then j described the self-darping characteristics cf the xenon transient following a

! rod-induced power trarsient (Enclosure 3, pages 9 cod 10).

. The licensee then provided the NRC steff with a comparison of actual measured flux levels against calculated levels to show that the current codes estimate flux levels within appreyirttoly 11, except at the outermost regions of the core. The corperison was provided for the current and  ;

previous cores (cores 17 and 16). Graphs of calculated versus actual axial l

flux distributions are providad on pages 17 and 18 of Enclosure 3, which show i a close corparison between calculeted end actual axial flux.

l The licensee provided a discussion of the administrative centrols currently j in place at Yankee to provide assurance that the requirements of 10 CFR  ;

! 50.46 are met with the currert code for Cycle 17. The licensee has added

! administrative controls to limit control red r.cverent which limits power

} levels in the upper core renion to limit any top peaked power distribution.

4 In addition, current TS have a restriction on how soon ef+er a power reduction

the core can be returned to full power if the rod heights are outside i

the rod insertion limit, and there is a restricticr. cn rod reactivity i transient rates. Octh cf these TS restrictions serve to limit the effect i of xenon transients on the axial flux distribution. The licensee has stated i that the additirrel restriction on rod withdrawal limits will remain in

effect until reaching 801 power during the power coastdown. Cerpensation for xener trrnsients will be accomplished using boron, to keep the rods within

! the administrative restrictier.

l l To show the effects of operating with a redded core, graphs were provided i

shewing the axial flux distributinr with and without the rod restriction, at two times in core life (page 2p, 21, Fnclosure 3). Page 22 (Enclosure 3)

! i shows the effect on xenon transierts with and without the rod restriction.

{ The graphs point out that the flux distribution is bottom-pealed with the 1 rodded core, which has the plant within the cricinal analysis assumptions for cycle 17 operations. Tbc creph on paoe 23 (Enclosure 3) further shows the i effect of reactivity rates on the exial power distribution, which points to t 7 the reason for refrteining the TS limits on reactivity rates. [

The licensee then provided infomation regardfrg the conservatisms in the

LOCA limits of Linear Fret Generation Rate (LPGR) vs. core burnup. The i licensee presented information re t Xenon Redistributier Factor (Fxe)garding and the conservetisns Rod Insertion that Factor exist in The (Fi). the licensee also discussed three other factors (the Peasurerent Uncertainty (Fu), the Power Uncertainty (Fp), and the Engineering Factor (Fe)) in the TS LHGR limit. The licensee proposes to combine these three factors statistically, es opposed to the current rethod of combining them

multiplicatively, as discussed on page 27 of Enclosurr 3. The f;PC staff

, - ,_.- -- -._,-.--, _m. -m,--,- - - _.- -. , _ - - - _ _ . - _ - , . . - - - . . __ . - - - - _ , - , , ~ , . ~ , _ . ~ .

. stated its belief that based on the information presented in the meeting, statistically ecmbining the three factors (Fu, Fp, and Fe) should be acceptable. The NRC staff stated that the licensee shculd provide its justification fer this proposal to allow for tlRC staff review.

The next three slides (peges 28-30 Enclosure 3) shev infomation regarding the integratico cf beron dilution with control rod motion, to support the Yankee proposal to use nominal flux shapes in its calculations, cs opposed to the current approach of using the xenon-induced flux shapes. The ,

slide on page LO (Enclosure 3) shows the difference in axial flux shapes for the nominel erd xenon shapes, and shows a bottom-peaked power distribution fer the nominal case, and a top-peaked distribution for the yeror cese.

Eclicefre the presentation, the NPC staff pointed out that the normal analysis assumptions consider TS allowable transients (i.e.. if TS allcw rod retien between 80-90 inches, the analysis should use these limits).

in addition, the NRC staff stated that adninistrative controls may ret te l arpropriate, but that the TS shculd be modified appropriately. The

, licensee provided the argurrent that the nominal approach is more life the s vry the plant operates, and tharefore should be used for the calculatiers.

} . The hRC restated its position of using the limiting analysis for the licensing basis. On the issue of using a statistical combination of the uncertainties, the NRC staff stated that similar proposals from other licersees have been accepted, while others have not, on the merits of the individual cases. The NRC staff would need to look at the details of the Verkre preposal. The NRC staff stated that the infomation to be provided by the licensee needed to include an apprcpriate data base, and to sber irdererdence of the factors involved. Based on the information presertad at tFa reeting, the NRC staff felt that the Yarkee approach to statistical ccmbination of uncertainties was appropriate, but that the staf# reuld have tc see the specifics before making its final determination.

The NPC staff then questioned the licensee regarding plans for rencHrg Fi and Fxc frce the LHGR calculations. The licensee felt that a bottom shaped flux distribution bounded the cosine curve, and Fi would net be reeded in the criculation. In the consideration for Fxe, the current TS value for Fxe would be modified as a part of the cycle 18 reload submittal, erd the licersee is considering other restrictions (e.g., rod motion limits) that may eliminate the need for Fxe. As part of the reload submittel. the licersee intends to make a case for eliminating the Fxe bottom mutiplier (page 26 of Enclosure 3).

The licensee presented information related to the LOCA analysis rethods that are being investigated (Enclosure 4). The licensee explained the i history behind the previous analyses performed up through cycle 17. The 1

anelysis for cycle 18 had beer performed using the cosine shaped flux distribution, and the licensee explained that the calculations would need to be re-perforned based on the current NRC concerns. To complete the i

reanalysis, the models that are currently being used will have to be modified in order to remove the crerating rod withdrawal restrictions to allow operation without a rodded cere. In 1975, the licensee had identified the Yankee models, explaining the differences between the Yankee j model and the generic effort based en the Exxon model heira used fer the H.B.

i Robinson plant. Since Yarkee was using the cosine-shaped flux l

, , . - - - - --,-------r-- - - - - -

i distribution, it used Fi and Fxe rutipliers to add additional conservatisn,.

Since the initial code devcicpment, a number of changes have been made to the Yankee model as more knowledge or limitations in codes have been identified. The latest questiers regarding the Yankee ECCS codes deal with conditions during the refleed phase of the accident analyses (after

, the blowdown and refill phases have ended). Based on the current concerns, e composite flux distribution was used te perfom the LOCA analyses. The composite distribution included the most limiting of the cosine and the physics-deterrired flux distributions.

The technical issue of concern in the reflood phase was to not have the flux peak in the upper ccre region because of the time it took to reflood that region. In the previous analyses using the cosirc shered flux distribution, the flux peak was in the core nidplane, and as long as the peak remained below this core midplane, the analysis using the ccsire shape would be bounding. The current analysis which identified a top-peaked power distribution led to rod withdrawal restrictions te provide flux suppression in the upper core region to cbtain a bottom peaked flux distribution, and therefore make the cosine shaped flux distribution again bound the actual flux distribution. Page 6 ef Erclosure 4 shows the licensee's proposed cperating restrictions for the power ccestdeWn phase of the operating cycle.

This page shews that rod withdrawal above the current restriction of 83 inches will be necessary. To allow for this, the licensee proposed a rod withdrawal rate limit of less than or equal to ? inches per dey te ersure the analysis' peak centerline tcrperature (PCT) remains less than 2200 degrees post-LOCA.

The licensee then provided a discussion of the cycle 18 crelyses that have i been perferred to date. Page 8 (Enclosure 4) shows the items the licensee is j *cquesting regarding the model and analysis parameter changes for its redcl.

Ore cf the issues shown deals with an injection delta-P penalty, which is e conservatisr included in the model to account for pressure loss due to in,iectier j parameters of angle and flow rate. The licensee is currently using a 90 l degree arple of injection, which results in a delta-P penalty of 0.8 psid.

With a modified model, the licensee proposes a delta-P pcrelty of 0.15 osid. TFe staff's initial impression is .that there should not be any problem in grantirg a modification of the delta-P penalty, tut the staff l needs to evaluete the licensee's calculations ard assunptions before making a final decision.

1 The NRC staff questioned the approprieteress of using nominal power shapes in the licensee's calculations. The licersee 0:plained that it intends to 1 perform a series of power shere calculations, which are an extension of burnup

sensitivity studies, using calculated flux sheres, rot the TS limits. The licensee ackncwledoed that this approach needs to be ,iustified. The TS l would then be based on a calculation to allow operating rargin providing for errors in calculations compared to reasured flux levels. This extra margin has in past efforts resulted in calculatfors based on TS kW/ft i limits to show possible problems in meeting Appendix K. The licensee had l then proposed a singic TS limit which would be limiting, er bounding, and be shown to be 14riting based on sensitivity studies. The staff pointed out that the licensee's efforts to meet Appendix k would be helped by using a variable limit en the kW/ft limit based on core height.

The licensee explained the differences bctueen its analyses and the Westinghouse methods (which result in a variable kV/ft limits). The licensee explained that to show one kW/ft limit, as opposed to a variable one,

5-sensitivity studies are needed to show the limit is bcunding. The current Yankee kW/ft TS linits are based on cosine-shaped flux distribution calculations. The licensee is working on develepirg kK/ft TS limits based on a top-peaked flux distribution, and add a known amount of conservatism.

for its variable kW/ft limits. Vestinghouse uses heicht-dependent flux (F delta H) linits fer departure from nucleate boiling (DhB) and hot channel calculations. These sane limits are used in the Westirchcuse LOCA calculaticrr. The Yankee model does not use F delta H in its LOCA rodel. The licensee does not feel there are any radial flux (Fxy) dependencies in the LOCA cciculations, and therefore uses kW/ft instead.

It was also noted that Westinghouse shews corpliance with Appendix K in pre-cycle calculations, wFile Yankee verifies conpliance throughout the cycle using actual measurements to compare to its calculations.

The licensee then explained that if the delta-P penalty rodification is approved, there would be no need to benchmark tFr rodified Yankee model, due to the naturc of the cFarces. The licensee also poir.ted out that this change in its model would be a permanent chance. The licensee proposed to provide the changes tc tha redel as a separate enclosure to the reload package. The staff felt it would be more apprcpria.te to provide the LOCA rodel changes in a separata letter, while at the same time use the modified redel in the cycle 18 submittal. The staff felt that Yankee had provided sufficient infonnctier ir the reeting such that the flPC staff feels the change to the modal will be acceptable, perding confirmation of the infonnation provided at the reeting. The licensee stated that if a problem with the cycle 18 analyses or the TS were to occer, the fallback position would be to rely on currert TS with rod restrictions.

The licensee stated that es it develops its final proposal, it may ask for additional conference calls or meetings to t*iscuss its approach with the staff. This approach is acceptable to the staff. The licensee was asked to provide a letter of comitment, to irclude the bases for removing l the current rod restrictions, frcluding any additional restrictions that

ray be necessary during the power coastvern, as discussed earlier in the reeting. -

The licensee asked one additional cuestion regarding whether the proposed modifications to the Yankee LOCA model would have to be prenoticed as a license amendrent. The staff's position is that the proposed j mooifications, other than the TS that result frcm the calculations, are of such a nature that the lictnse is rot being modified, and therefore would net require prenoticing.

The resident inspector noted that with the changes in operating restrictions proposed by the licensee, the Licensee Event Report (LEF) vould

need to he rodified. The licensee agreed to submit a modified LER.

l

l. l The meeting was adjourned. The staff took special note of the forthrist t cppreech presented by the licenst.e in this meeting, and also.noted the

! sound and timely technical efforts that have been expended by the licersrc j f r its investigations of the LOCA model.

i j pGpl$. k Ja es W. Clifford,' Project Pare.ger Operating Reactors Branch No. F ,

i

Enclosures:

1. List of Attendees ,

2. Meetire Agerda

3. Core Power Distribution Handouts

. 4 LOCA Analysis Methods Handouts cc w/ enclosures: .

See next page i

i i

i  :

l 1

i s

~

1 l

l l

l l

,w- - , , , r, - - - +.. -<-,-.w-+,=-y7 ,-e, , - -- y -,-w -

-.3.e--,-.. ,n-.-,,-,=, + , ~ ,m -,y,- .r,-,y-r---,- --,r--,--ee. --e,- --

cc:

Mr. Jares E. Tribble, President Yankee Atomic Electric Company 1671 Worcester Poed Framingham, Massachusetts 01701 Thomas Dignan, Esquire

Popes and Gray 225 Franklin Street Boston, Massachusetts 02110 Mr. N. N. St. Laurent

< Plant Superintendent Yankee Atomic Electric Company Star Poute Powe, Massachusetts 01367 Chairman Board of Selectmen Town of Rowe Pove, Massachusetts 01367 Pesident Inspector Yankee Nuclear Power Station c/o U.S. NRC Post Office Box 28 Monroe Bridge, Massachusetts 01350 Pegional Administrator, Region I U.S. Nuclear Regulatory Commission

631 Park Avenue l King of Prussia, Pennsylvania 19406 Robert M. Hallisey, Director Radiation Control Program Massachusetts Department of Public Health 150 Tremont Street, 7th Floor Boston, Massachusetts 02111 Mr. Georoe Papanic, Jr.

Senior Project Engineer - Licensing Yankee Atomic Electric Company 1671 Worcester Road Framingham, Massachusetts 01701 i

_ _ - , ~ _ . . . - , _ _

_ - , . . _ - . _ --r- . . _ . . - , , - - . , _

ENCLOSURE 1 LC (T H YA5 ( lc. En Code :

M EETic G

& ?nYs6 A(FILt:1 TIC /J sJ. m Ceirw .ut efj.m /Di-Jom A b ouwsm NRc,Mulou s Geaxac 74rnme. In YAEC Teu 2. H .ne u:n vaer

)wnb /-lun rc7e. YdG AusAF Mu s AN yAEC- Loc A Cwcq k unD T.CAccaarc~To 1AEC - Ga9erce Syrics Marv6 Dune. dell hRL /Lfd

})o wA f a ft c /J uj C- 5 t/ 't kiWom AV2C-[7$

& il S z y n .= z d - Wet-t.ock Gour Sm g %e. 2/ik- YA6C svan yAcc- vudw Ey.py t.

Aam Ocaumoa ssc/drwa nsncra Cvnr.c.orer A. MArsa- Ype_c.- Rucrog r-wiceerucc, MO fJCC//56 l

l 1

- ENCLOSURE 2 AGENDA YANKEE PLANT AXIAL POWER SHAPE MEETING 10:00 INTRODUCTION B. C. Slifer 10:15 CORE POWER DISTRIBUTIONS R. J. Cacciapouti

-Yankee Core Characteristics

< -Typical Axial Power Shapes

-Xe Transients: Durations and Axial Shapes

-Cycle 17 Measured vs. Predicted Power Distributions

-Impact of Rod Program on Cycle 17 Power Shapes

-Core Power Monitoring

-Application of Uncertainty Factors

, -Basis for Cycle 18 Power Shapes 11:15 LOCA ANALYSIS A. Husain

-Background Information

-Basis for Previous Analyses

-Axial Power Shape Discussions to Date l -Response to NRC Letter of May 22, 1985

-Analysis for Cycle 17

-Analysis for Cycle 18

-Prospective Methods Improvements I

-Axial Power Shapes 12:00 DISCUSSION I

l

-Cycle 18 Schedules Bcs

,-B_asi_s for Cycle 18 Analysis _8/8/8f___

OBJECTIVES

1. To explain actions taken to assure compliance with 10CFR50.46 for Cycle 17.

2. To explain actions planned to assure compliance with 10CFR50.46 for Cycle 18.

3. To obtain NRC feedback on a) basis for axial power shapes for LOCA analysis b) statistical combination of uncertainties c) injection AP penalty reduction

4. To discuss Cycle 18 schedules.

! 5. Time permitting, to discuss future LOCA methods improvements.

Bcs 8/8/85

ENCLOSURE 3 l YANKEE ROWE CHARACTERISTICS POWER LEVEL 600 MWT NUMBER OF ASSEMBLIES 76

. RODS PER ASSEMBLY 230/231 ACTIVE HEIGHT 7.5 ft.

CONTROL ROD TYPE CRUCIFORM NUMBER 24 GROUPS 4 MATERIAL Ag-in-Cd 1

l

z CONTROL ROD CROUP IDENTIFICATION 3 4 1 _2 D-5 6 7 8 9 }0 D. C - .

18 15 16 17 11 ,12 13 14 B B D 3 24 25 26 - 27 ,28 19 20 21 22

~

A B D_ B 35 36 37 38 31 32 33 34 29 30 '

C A A C 44 e5 46 47 48 40 41 42 43 39 ,

B A B D 56 , 57 58 52 53 54 55 49 50 51 D B B '

l 63 64 65 66 60 61 $2 59 ' .

l C D E A 69 70 , 71 72 67 68

~

D . .

73 74 75 76 .

- ASSEMBLY POSITIOS e

__ _- - - . . - - - . - - - - - - - --------,--------r-,--- .,, ,,,v,--aw<w..,,, ._,,...e, . , - , _ -

3 YANKEE CORE 17 POWER DEPENDENT INSERTION LIMIT 110 ;

4 100 -

4 90 -

e w 80 -

r O

0-

_a E 70-e e

r H

y 60 -

_a o

c r

3

_a 50 -

E ta.

O 40 -

H z

w

- O

'n x w 30 -

o_

20 -

10 -

y i y y y ii y y v v gy s u y a gs 90 T Y y 30 40 50 60 70 80 0 10 20 l

l GROUP C POSITION (INCHES)

y YANKEE ASSEMBLY TYPE A l

l 1 II-  :

II II II X lI II II II II

~

ZZZZZZZZ EZZZ YANKEE ASSEMBLY TYPE B n I a

(

X

, s l

l 9 u w

l

CORE 18 TYPICAL AXIRL POWER SHAPES FRESH FUEL 1.s o - 1000 MWD /NTU

1. 4 - o - 6000 MWD /NTU i a - 14000 MWD /MTU l 1.3 - 0 1.2 - c e ,

C c 1.1 -

a:

y 1.0 -

O

' E- 0.9 -

_3 b

X 0.8 -

C g 0.7 -

"g 0.6 -

c w 0.5 -

e

0. 4 -

O.3 -

0.2 -

0.1 .

l 0.0 .

0 10 20 30 40 50 60 70 80 90 100 l

CORE HEIGHT (*/.) q

9 8

CL C LJ

~b I CL (O C I

JCD C _o ZZ mO (O EZ LJ O ld Q ZX C

I I I _o N

LO OO D

T H LJ E.

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Z O O H Z O > X hJ O G X - 0-Q E-. a Z e I C t G3 3

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a. 3 WN E -

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.J [J 3

m C D O Z ts. -S O e--e r I (J()

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2 O O O f*

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ra O s- I Z C IJ C IJ

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-9 Y w r y w w v 7 7 w w y 5 r v v w y v y w y v v y w 9

Y Y 9 T 9 9 1 9 9 9 D 9 9 9 o

9 o

9 o

9 o o

- .. .- - o o o o o 83M0d 191XU 3AIIUl38

~ ,.

6 i CORE 18 XENON TRANSIENT RT FULL POWER CORE RVERAGE FOR NODES 10 RND 3 -

, 1.6 o - NODE 10 (80%)

o - NODE 3 (20%)

! 1.5 -

l l

1. 4 -

x to 1,3 -

c .

o Q.

d a

1.2 - c c c j Z -

0 0 0 0 l

u ~ "

m 1.1 ] '

H i

$ = = c c -

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, CE - - -

1 j 0.9 -

i 0.8 -

l 0.7 , , , , , , , , ,

0 5 10 15 20 25 30 35 40 45 50 TIME (HOURS) ._o

0 JO 9 8 o (

m OO - 4!

OO Zw i

JO C- o Z e m IJ EQ M OO i U ZZ Z )

O I I m LL- n OO U

dO Q

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• R R  %

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?

0

- - o o a 83M0d 1900N 3AI19738 1

II COMPARISDN OF MERSURED VS PRE 0!CTED REACTION RATES

~

INCORE RUN YR-17-012 1337. MWD /MTU 599.7 MWT. GROUP C AT 83 8 INCHES A B C D E F G H J K

.990

.687

}

.433

.991 2

.596 1.016 1.003 1 011 .sez 3

.396 1 101 1.011 1 107 1 009 1.097

.22C .986 1 146 1.093 1 144 1.093

.266 .047 1 142 1 136

.sts 1 116 1 019 1 116 1 004 7

.032 1 573 r 1.018 1 023

.483

.864 .994 g 990 1 013

-3 997 -1 902 RER$URED PRE 01CTED 10 E O!FF l

II COMPRRISON OF MERSURED VS PREDICTED REACTION RATES INCORE RUN YR-17-018 6873. MWD /MTU 599 9 MWT. OROUP C RT 82 875 INCHES R 8 C D E F G H J K

' .091

.997

}

.817

.983 1 000 g - 1 996 1.028 1 018 1 020 i.011 3 .986

.790 1 024 1 104 1 014 1 004 4 1 018 .992 1 125 1 092

• ** 8 883 5 .DO8 .067 1 124 1 123 6 .086 1 102 1.028 1 102 1 012 7 .023 1 572 1 028 1 024 8 .238

.883 .992 g .980 t.005

-2 554 -1 320 MEASURE 0 PRE 01CTED 10 x otrr

- , - - - . - - - . - , ,7-> - , -.--r,--,- ,- r --. - , , . - - - ,

1

' 13 ll COMPRRISON Of MERSUREO VS PREDICTED REACTION RATES INCORE RUN YR-17-023 11840.0 MWO/MTU 599.0 MWT. OROUP C RT 82.125 INCH C D E F G H J K R B

.693

.701 1

-1 167

.990 1 009 2 -1 986 1 036 1 036 1 03I I'028 3 .684 '743 i

1 034 1 101

! 1 024 1 091 4 1 006 .984 1

1 110 1 000 i 1 107 1 088

.282 -.107 1 108 1 107 6 .088 1 094 1 037 1 094 1 024 7 .046 1 283 1.033 1 030 8 .304

.654 .992

.662 1 004 g

-1 189 -1 134 MERSURCO

' PRCOICTED 10 x 0 rr l

l i

I t

l I

W COMPARISON OF MEASURED AND PREDICTED SIGNALS INCORE RUN YR-16-013 599.9 'AWT. GROUP C AT 85.0 INCHES 1172. MWD /MTU 0.605 0.614

-1455 1.064 1.079

-1.450 1016 1.0 34 1029 1051

- 1.2 41 -1.663 t031 1.10 0 1.051 1.085

-1.901 1385 1.084 t019 t063 t024 1.987 -0.492 1.074 1.063 1.0 41 1.11 0 1.045

=1.0 85 1.051 2.3 11 -0.573 1.045 1.028 1.051 1029

-0.589 -0.058 0.862 1.064 WEASURED SIGNAL 0A44 1.079 PREDICTED SIGNAL 2.444 0.404 PERCOU DIFTERENCE

pj !

l l

COMPARISON OF MEASURED AND PREDICTED S!GNALS INCORE RUN YR-16-025 599.9 MWT. GROUP C AT 84.6 INCHES 6492. MWD /MTU 0..+3 0.645 0.030 1030 1042

-1.18 8 1038 1042 1037 1047 0.M8 -0.476 1.040 t000 LO47 t009

- 0.691 0.0 92 1077 1.040 1073 1.040 0.3 91 0.020 t075 t073 0.196 ,

1.090 t051 t089 t047 0.133 0.393 l

t042 t033 l 1.037 1047

• a- C.467 -0.293 0.968 1.040 WEASURED DONAL 0.845 t042 PREDICTED SIGNAL 3.046 -0.f71 PDtCOff DIFTERENCC 1

. _ - - - - _ ~ . _

Ib COMPARISON OF MEASURED AND PREDICTED SIGNALS INCORE RUN YR-16-035 599.8 MWT. GROUP C AT 85.6 INCHES 12420. MWD /MTU 0.689

• 0.666 3.505 1.023 t022 0.132 t045 1.046 1.042 1047 0.294 - 0.007 1.045 1.088 1.047 LOSS

-0.H1 0.2 M t044 1.078 1.040 t075 0.3 T1

-0.494 1.072 1.075

-0.287 1075 1045 1086 1.047

-0.991 - 0.177 1.04 5 1.029 1.047 t042

-0.185 -1.2 41 WEASURED S1CHAL 0.662 1.013 PREDICTG SIGNAL O.648 1.022

-0.892 PERCENT DIFTERENCE 2.110 l

l

CORE 17 INCORE RUN 022 RT 10677 MWD /MTU

CORE AVREAGE RXIRL POWER GROUP C RT 02

1.5

- CALCULRTED

1. 4 -

1.3 -

1.2 * '

O -

1.1 H O ru y 1.0 -

o G- 0.9 -

d u 0.8 -

E g 0.7 -

"g 0.6 "

, 5 w 0.5 ..

a:

0.4-0.3 -

0.2 -

0.1-0.0 ... ... ... .,. .,. .,. .,. .,.

90 100 0 10 20 30 40 50 60 70 80 _

4 CORE HEIGHT (%)

CORE 17 INCORE RUN 023 RT 11840 MWD /MTU CORE RVRERGE RXIAL POWER GROUP C RT 82 1.5 1.4 -

- CALCULRTED 1.3 -

1.2 - .

V O o a- 0.9 -

_.)

b x

0.8 -

o c

g 0.7 -

i >

l [ 0.6 -

e i

d x

0.5-

0. 4 -

0.3 -

0.2 -

0.1-:

0.0 ... ... ... ... ... ... ... ... ...

0 10 20 30 40 50 60 70 80 90 100 CORE HEIGHT (%) 2 1

~ _ _ _ _ _ _ _ _

l9 t

YANKEE CORE 17 POWER DEPENDENT INSERTION LIMIT 110 ,

1 90 -

1 f

' U M-3 o

3 E

tr 70 -

(AJ

~C H

y 60 -

.J (D

[

3 o

g 50 -

[

CA_

o 40 -

H Z

l ta]

! O i

Y c_

M-l 10 -

1 O ,. ... ...

90 30 40 50 60 70 80 0 10 20 GROUP C POSITION (INCHES) t

. . . __ _ __ ' ' - ~ ~ -g--- - . _ . . _ , _ _ ,_ , _ _ _ ,

CORE 17 CONPARISON OF RXIRL PROFILES RESTRICTED AND UNRESTRICTED R00 NOTION BURNED FUEL RT 10000 hWD/NTU 1.s a - UNRESTRICTED o - RESTRICTED t

i 1.4 f 1.3 - -

1 g 1.2 -

] taJ l

2 i O l

' 1.1 -

3 j $

X 5 3 0 5 g 1.0 -

) a I

j [

c 0.9 -

J taJ

• a.8 -

l l 4 I

J 0 7~

j i 1

0.8 -

i i

l 0.5 . .... .. . .

l 0 10 20 30 40 50 60 70 80 90 100 M

O CORE HEIGHT (%)

l i

l l

l i

o CORE 17 COMPRRISON OF RXIRL PROFILES e

RESTRICTED AND UNRESTRICTED ROD HOTION l

BURNED FUEL RT 12S00 MWD /MTU <

1.s o - UNRESTRICTED l o - RESTRICTED 1.4 -

l 1.3 -

g 1.2 - 1 to 1

o Q- 1.1 -

d

- c

=

x e

g- 1.3 - i w

[ 0.9 -

a-

d E 0.8 -

I 0.7 -

1 D.6-0.5 ... ... ... ... ...

50 60 70 80 90 100 20 30 40 0 10 CORE HEIGHT D.) h I

CORE 17 COMPRRISON OF XENON RXIRL PROFILES RESTRICTED AND UNRESTRICTED ROD MOTION CORE AVERAGE AXIAL RT 12500 MWD /MTU .

1.s . o - UNRESTRICTED I o - RESTRICTED 1.4-i 1.3 - .

i

! e 1.2 -

N o

' 1.1 - e _

e _

a 1

5 X

c 1.0 -

Y l p 0.s -

e d

E i 0.8 -

0.7 -

i l

0.6 -

0.5 ,- -

60 70 80 90 100 l

0 10 20 30 to 50 x

[

CORE HEIGHT (%) u l

CORE 17 COMPRRISON OF RXIRL PROFILES 9

RESTRICTED AND UNRESTRICTED ROD MOTION CORE RVERAGE RXIRL RT 85 % POWER IN CORST00WN 1.7 o - INSTRNTRNEOUS 1.s -

- 2 IN/12 HOURS a - 2 IN/24 HOURS 1.5 -

1.4 -

1.3 -

8' g 1.2 -

5 I y 1.1 - ,

s 1.0 -  ;  ;  ;

5 g 0.9 -

0.8 -

\

j 0.7 -

0.6 -

0.5 ... ,. ...

0 10 20 30 40 50 60 70 80 90 100 N CORE HEIGHT (%) w

i'l POWER DISTRIBUTION LIMITS TECHNICAL SPECIFICATION

?

I bx = F,y F, F u F,, F, F, F, Fx,7 F xy RADIAL POWER F, AXIAL PEAK -TO- AVERAGE F

u MEASUREMENT UNCERTAINTY (1.068)

F,, STACK SHORTENING (1.009)

F, POWER UNCERTAINTY (1.03)

F, ENGINEERING FACTOR (1.04)

F, ROD INSERTION FACTOR F,x XENON REDISTRIBUTION FACTOR i AVERAGE KW/FT

YANKEE CORE 17 CONTROL ROD INSERTION MULTIPLIER -

1.02 W

e -

N

_a b 1.01 -

'3 -

a z

e 1.00- , , , ,

80 82 84 86 88 90 GROUP C POSITION (INCHES) 5

YANKEC CORE 17 MULTIPLIER FOR XENON REDISTRIBUTION

• 1.20 1.15 -

J U

h 1.10 -

'3 A

) -

1.05 -

l l

l 1.00 '

0 $ k h i l0 l2 1t is  %

CYCLE BURNUP (GWD/MTU) e

17 l

l STATISTICAL COMBINATION F

u MEASUREMENT UNCERTAINTY (1.068)

F, POWER UNCERTAINTY (1.03)

F, ENGINEERING FACTOR (1.04)

MJLTIPLICITIVE (1.144)

STATISTICAL (1.084)

a. _ . _ _ _ _ . 's_ m -a- - -m - - A A--- -' -a----- L - - -- ^ ---- -

I CORE 18 BASIS FOR POWER SHAPE  :

a NOMINAL XENON INDUCED S'

1 l

CORE 17 TYPICAL ROD MANEUVERS _

STERDY STRTE FULL POWER OPERATION .

90 89 -

es - .

^

tn ta 87 -

W C es-E 3

[ es- ] \

84 - -

= c -

g 83 -

e 82 -

81 -

80 , , , ,

18 20 22 24 6 8 10 12 14 16 0 2 4 TIME (HOURS) w

__c

30 8

La.)

CL C IJ -@

. I a_

Ln T I

-) Ln C

ZZ _oO (f) MC L) y EZ l

__) O [J

.-. ZX la I I O

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2 O O O H O X f

x W- e

- Q e-.e 5-*

u a C 1 Z a C __3 IJ

[J Z g ..*O oO x D z L m

E O O

Z K CD ' d q)

-8

[4.J Z

O o O O _N

-9

. . O f $ $ 1 5 9 $ $ D $ $ $ 9 9 5 9 O

• * * * *

• O O O O O O Q O O 83M0d 19IXU 3AIIU138 1

'- YANKEE LOCA METHODOLOGY 1

l i

l ORIGINAL t

i 0 XN-75-41 VOLUMES l TO lil AND SUPPLEMENTS 1 TO 7 1

0 GENERIC SER oN H B ROBINSON SEPTEMBER 11, 1975 1

0 YR SAMPLE PROBLEM XN-75-41 APPENDIX C [

CH0PPED COSINE POWER SHAPE USED 2

0 YR SER DECEMBER 4, 1975 APPLICABILITY OF GENERIC METHOD

]

- SPECIAL REVIEW OF SHORTER CORE, IHINNER FUEL ROD, DIFFERENT ACCUMULATOR CONFIGURATION GENERIC MODEL CONSERVATIVELY COVERED MODEL CHANGES AT YAEC 0 REVISED CALCULATION OF E0BY 3/77 0 LOW FLOW FILM BOILING HTC 6/77

}

0 CORE FLOOD RATE STABILIZATION 7/77 l

O LOWER PLENUM PHASE SEPARATION MODEL 11/80 0 RELAP5YA METHOD DEVELOPMENT (IN PROGRESS) 1

2%

i AxlAt POWER SHAPE DISCUSSIONS 1

0 MARCH 29, 1985 (CALL FROM NRC)

EXXON CONCERNS APPLICABLE TO YANKEE PLANT YP USES COSINE POWER SHAPE i

YANKEE WILL ASSESS POWER SHAPE IMPACT i

0 APRIL ) , 1985 (CALL FROM YANKEE)

ACTUAL POWER SHAPE FLAT AT E0C

- ACTUAL PEAK 8.2 KW/FT; ANALYZED PEAK 11.2 KW/FT AT 80% ELEVATION; ACTUAL KW/FT)> ANALYZED KW/FT Ex1 STING COSINE T00DEE-2 RUN REANALYZED WITH ACTUAL POWER SHAPES AT HIGHER ELEVATIONS.

PCT <[2200 F

- NRC TO CALL BACK FOR MORE INFORMATION, IF NEEDED.

D l

e YANKEE CORE 17 RXIRL SHRPC COMPRRISON v

HOT FULL POWER, 8000 MWD /MTU 15 o - LOCR (INFERRED) o - PHYSICS DESIGN 12 -

0 C 9- m e ,

c

(

O e ,

_5 3 6-l 3-t 3 4

'

• v - 'v ' - y = = -

0 10 20 30 40 50 60 70 80 90 100 PERCENT OF CORE HEIGHT W

YRNKEE CORE 17 RXIRL SHAPE COMPRRISON HOT FULL POWER, 12500 MWD /MTD 15 o - LOCR (INFERRED) o - PHYSICS DESIGN 12 -

t y 9-1 M c c c e o s

] 6-3-

0 'I'd 2d $d IN NO NN 7d 8O Nd 100 PERCENT OF CORE HEIGHT r

!. b i

j CYCLE 17 REANALYSIS ACTIVITIES l .

Full POWER OPERATION '

i T

i j 0 XE INDUCED IOP SKEW POWER SHAPES MAY LEAD TO DERATE 0 EXISTING LICENSING ANALYSES WILL COVER BOTTOM SKEWED POWER SHAPES 0 RODDED OPERATION WILL FORCE BOTTOM SKEWED

]

POWER SHAPES l 0 PLANT WAS ORDERED TO INSERT RODS (80" TO 83")

i i

i 0 BoTron PEAK WITH IECH. SPEC. LIMIT OF 11.2 KW/FT I WAS ANALYZED i

i

! O PCT < 22000F i

i i

1

(0

- POWER COAST DOWN ANALYSIS O rod WITHDRAWAL BEYOND 83" REQUIRED O PCT < 2200 F, IF POWER,( 85%

rod WITHDRAWAL RATE 4 2" PER DAY 1

l

7 INJECTION AP PENALTY 1

0 ' CURRENT MODEL (BASED ON XN-75-41)

AP PENALTY ANGLE OF INJECTION WITH Acc. WITH PUMP L

90 1.8 0.8 75 1.5 0.35 i 60 0.4 0.35 45 0.6 0.30 1

~ .

i-0 XN-NF-78-30 MODEL BASED ON 1/14 AND 1/3 SCALE IEST l - A P = 0.15 P S I D GENERIC APPROVAL SER 3/30/79 i

i 0 A P = 0.15 PsID APPLICABLE To YP i

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3 I l

l i

CYCLE 18 ANALYSIS l

i i

i WANT i

Av01D POWER DERATE Av01D UNWARRANTED OPERATING RESTRICTIONS 1

SER BEFORE PLANNED PLANT STARTUP ,

4

, NEED I^

NEAR IERM MODEL CHANGES i

INJECT 10N AP PENALTY STATISTICAL COMBINATION OF UNCERTAINTIES ..

USE OF NOMINAL POWER SHAPES CHANGE IN F XE AND F, TECH. DEC. .

f l

. ,5m

.,,..,-,,m,,,-e , - , - , . - - . - - .,. , . ., _ , _ - _ , __.m.-

$t i I I 3 0.2 _

Upper Bound

\ .

- s **

3m 0.1 _ ,

3 . . . .

c +.

. t o . *

'S .

e .s u .

e .

p 0 0 * *

• N *" .. . .

i g . =

y o .

a ". ,

e 8 **

• -0.1 , ., , ,

s y = .

{

m

, .,=

l.

m

= n L E _

• CL *

-0.2 -

• Duplicate Runs 1/14 Scale Data 2

n 1/3 Scale Data x

- z

> ^ ' i

-0.3 I 8 0.6 0.7 0.2 0.3 0.4 0.5 {

O 0.1 pV 2 ("

, s 4, INLET STEAM DYNAMIC llEAD. 29 o 9

v FIC.tlRE 2.3 PRESSURE LOSS DUE TO PUMPED SAFE 1Y INJECTION a

. . . _ . - _ ,