ML20100Q021

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Forwards CENPD-279 & Suppls 1 & 2 to CENPD-279, Annual Rept on C-E ECCS Codes & Methods for 10CFR50.46. Rept for 1992 Will Be Submitted After Rept Received from Vendor
ML20100Q021
Person / Time
Site: Calvert Cliffs  Constellation icon.png
Issue date: 01/30/1992
From: Creel G
BALTIMORE GAS & ELECTRIC CO.
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9202050209
Download: ML20100Q021 (1)
v • d • e


Text

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/' F3 ALTIMORC OAS AND ELECTRIC

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1650 CALVERT CLIFFS PARKWAY

  • 1.USBY, MARYLAND 20057 4702 oronor c. cn n viee race.ocwt January 30,1W2 Nucte Am F

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U. S. Nudear Regulatory Commission Washington, DC 205$5 ATTENTION:

Document Contr01 Desk

SUBJECT:

Calvert Cliffs Nuclear Power Plant Unit Nos.1 & 2: Dr.cket Nos. 50 317 & $0 318 Annual Report on !!CCS Codes and Methmis Reaulted by 10 CFR 50.46 Gentlemen:

Attached are the 19891991 Annual Reports on Emergency Core Cooling System (!!CCS) Codes and Methods required by 10 CFR 50.46. *lhe IW2 report will be submitted after we receive it from our vendor.

Should you br.ve any further quw:lons reprding this matter, we will be pleased to discuss them with you.

Very truly yours,

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GCC/DWM/dwm/bjd Attachments cc.

D. A. Brune, Esquire J. E. Silberg, Esquire R. A. Capra, NRC D. G. Mcdonald, Jr., NRC

1. T, Martin, NRC P. R. Wihon, NRC

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CENPD - 279

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el AN.NUAL REPORT ON C-E ECCS CODES AND METHODS FOR 10CFR50.46 4

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LEGAL llOTICE TIIIS REPORT WAS PREPARED AS AN ACCOUNT OF WORK SPo!! GORED BY ADB COMBUSTION ENGINEERIltG.

11EITi!ER ADO. COMBUSTION EltGINEERIl1G HOR ANY PERSON ACTING O!( ITS DEllALFt A.

MAKES ANY WARRANTY OR REPRESENTATION, EXPRESS OR IMPLIED INCLUDING T'IE WARRANTIES OF FITNESS FOR A PARTICULAR PURPOSE OR MERCl!ANTABILITY, WITl! RESPECT TO Tile ACCURACY, COMPLETENESS, OR USEFULNESS OF Ti!E INFOR!!ATIOlt CONTAINED IN Ti!IS REPORT, OR TilAT T!!E USE OF ANY INFORMATION, APPARATUS, METitOD, OR PROCESS DISCICSED IN Ti!IS REPORT MAY 110T INFRIltGE PRIVATELY OWNED RIGl!TSr OR D.

ASSUMES ANY LIADILIT'.'ES WITl! RESPECT TO Tl!E USE OR FOR DAMAGES RESULTING FROM THE USE OF, ANY INFORMATION, APPARATUS, METIIOD OR PROCESS DISCLOSED IN Ti!IS REPORT.

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CENPD - 279 hNNUAL REPORT ON C-E ECCS CODES AND METHODS FOR 10CFR50.4o TRANSIENT METHODS AND LOCA NUCLEAR FUEL ENGINEERING APRIL 1989 COMBUSTION ENGINEERING

l Abstract This report describes changes and errors in the Combustion Engineerin,; codes and analysis methodology for ECCS analysis itors the last approved version through tho end of 1988 per the requirements of 10CIV50.46. For this reporting period only one coreputer code had reportable changes or errors. The corrections and chan6es reduced the peak cladding ternperature by less than 1*F.

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Tabic of conttnLa 1.0 Introduction 1

2.0 Codes for ECCS Evaluation 2

3.0 Error Corrections and Model Changes in Computer Codes 2

3,1 STRIK113 11 3

4.0 Conclusions 4

5.0 References 4

11

1.0 Introduction This report addresses the NP.C requirement to report. changes or errors iti licensed codes f or ECCS analysin. The revision to the ECCS Acceptance criteria " spells out reporting requirements and actions required when I

errors are corrected or cha'.ges are tsade in an evaluation inodel or in t be application of a model for operating licensee or construction perinittee of a nuclear power plant.

The action requircinents in i 50.46(a)(3) are:

1. Each applicant for or holder of an operating license or construction perini t shall estimate the effect of any change to or error in an acceptable evaluation model or in the application of such a model to de te rtaine if the change or error is significant. For this purpose, a

significant change or error is one which results in a calculated peak fuel cladding +;ettpetature &CT) dif ferent by more than 50"P frotn the temperature calculated for the liiniting transient using the last acceptable :nodel, or is a cutuulation of changes and errors such that the $wa of the absolute tnagnitudes of the respective temperatute changes is greater t.han 50 r.

2. For each change to or error discovered in an acceptable evaluation snodel or in the application of such a uodel that affect s the temperature calculation, the applicant or licenseo shall report the nature of the change or error and its estimated effcct on the litniting ECCS analysis to the Cotmnission at least annually as specified in 5 50.4. This report is to be filed within one year of discovery of the error and snust be reported each year thereaf ter until a revised evaluation model or a revised evaluation correcting minor errors is approved by tha NRC staff.
3. If the change or error is significant, the applicant or;1icensee shall provide this report within 30 days and include with the report a proposed schedule for providing a reanalysis or taning other action as may be needed to shov compliance with 9 50.46 1

1 I

requiretacuts. This schedule itsy be developed using an integrat ed scheduling systets previously 'appivved for the facility by the linC.

For those facilities not using an !;RC apptoved integr at ed scheduling systein, a schedule will be ectablished by the liRC staf f within 60 days of receipt of the proposed i.chedale.

4. Any change or ortor correction t. hat results in a calculated ECCS pe r fo tinanc e that do. not confot1. to the criteria set forth in paragraph (b) of 5 50.46 is a reportable event an described in $$

50.55(e), 50.72 and 50.73. The affected applicant or licensee shall propose im:nediate steps to demonstrato compliance or bring plant design or operation into compliance with 6 50.46 requirements.

This report documents all the changes made to the presently licensed C E IDCA analysis models and itethodology which have not been reviewed by the

!?RC staf f. This is specifics 11y to catinfy the requirements described in the second item above.

2.0 Codes for ECCS Evaluation C E uses several digital computer codes for ECCS analysis that are described in topical repost.s, are licensed by the NRC and are covered by the provisions of CFR 50.46.

Those for large break loc 4 calculations are: CEFIASil 4A, COMPERC II, PARClle, CTRIKill-II, and COMZIRC. CEFLASil 4AS is used in conjunction with COMPERC II, STRIKIN II, and PARCll for sinall break ILCA calculations.

3.0 Error Corrections and Model Changes in Computer Codes This section discusses all error corrrections or model changes to the licensed codes which rany affect calculated PCT. Only t.he STRIKiti II computer code has been changed since the last approved subtnittal to the NRC. No changes to analysis procedures have been ;nade since the last approved submittal to the NRC.

2

y 3.1. STRIKIN.II A. Code Description j

STRIK1N+II is a TORTRAN digital computer program which is used by f

Combustion Engineering, Inc. to calculate the core hot spot cransient peak clad temperature (PCT) and peak local clad oxidation percentage for a large break LOCA. It is also used to provide initial fuel temperatures for the small break LOCA peak cladding temperature calculation. A detriled code description is presented in l

References 2 through $.

t B. Error in STRIKIN II DNA Model Coding i

An error in the approved virsion of STRIKIN II which may potentially affect calculated PCT has been identified and corrected. Reference i

(6). A revises version has been prepared for licensing calculations.

f Due to a coding error STRIKIN II formerly limited the fluid quality to a positive value for the liacBeth correlation. The revined version allows use of a negative fluid quality as appropriate. The icipact of of this correction for a large break LOCA is a 0.19"F decrease in the peak cladding temperature. The impact on a small break LOCA could be prediction of DNB slightly earl!ct than it would actually occur if MacBeth is used with a negative quality. Correction of the error actually produces no change in cladding temperature at the beginning of steam coolin6 therefore no change in PCT.

C.

Changec in STRIKIN II Code An option has been added to CTRIKIN.II to limit the cladding strain rate for. the pre-rupture strain model to a-realistic strain rato instead of-introducing the pre rureure strain in a single time step.

Without a strain rate limit. STRIKIN II changes the fuel cladding gap width too quickly when the pro rupture strain model is invoked, 3

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This cha11 cores the gap conduct ivity and tempo. tut e model and can cause the code to abort. Use of this option produced no et teet on PCT.

4 0 Conclusions T'.ie errer correction and the change to STRIKIN II have the potential to affect the PCT. Il> wever, the actual effect of the two changes is to reduce PCT by less than 1 T.

This is a very sina11 change in PCT for the liuiiting transient. There were no significant changes in the sense of Crn 50.46.

Tt is summarizes the error corrections and changes to the C E 113CA codes and models frort the last accepted versf ons through December 1988, 5.0 Refer 9nces

1. "Eruergency Core Cooling Systern; Revisions to Accept anco Criteria "
10CrR50, Federal Register, Vol 53, No. f.80, September 16, 1988
2. CENPD 135P, 'STRIKIN11,ACylindricalCes.h*tryfuelRodllcatTransfer Program," August, 1974
3. CENPD 135P, Supplement 2, "STRIK1N 11, A Cylindrical Geometry Fuel Rod sleat Transfer Program (Modifications)," February,1975
4. CENPD 135, Supplement 4 P, "STRIKIN II, A Cylindrical Geometry Fuel Rod llent Transfer Pro 6rarn," August, 1976 P
5. CENPD 135, Supplement 5 P, "STRIKIN I:,

Cylindrical Geometry Puel Rod llent Transfer Program," April, 1977 l

o 6 "STRIKIF 11 8 7316 f rorn 85074," CD TML 0(1., M. Michonski, January 20, 1988.

4

CEl1PD - 279 SUPPLEMENT 1

ANNUAL REPORT ON C-E ECCS CODES AND METHODS FOR 10CFR50.46 FEBRUARY 1990 COMBUSTION ENGINEERING nw u m-me

LEGAL NOTICE TitI REPORT WAS PREPARED AS AN ACCOUNT OF WORK GPollSORED BY ADD COMDUSTION ENGIltEERING.

NEITitER ADD COMBUSTION ENGINEERING HOR ANY PERSON AcrING Olt ITS DEllALP A.

MAKES ANY WARRANTY OR REPRESENTATION, EXPRESS OR IMPLIED INCLUDING T!!E WARRANTIES OF FITNESS FOR A PARTICULAR PURPOSE OR HERCIIANTABILITY, WITit RESPECT TO Tile ACCURACY, COMPLETENESS, OR USEFULNESS OF Tite INFORMATION CONTAINED IN TilIS REPORT, OR T!!AT Tile USE OF ANY INFORMATION, APPARATUS, METi!0D,

OR PROCESS DISCLOSED IN T!!IS REPORT MAY NOT INFRINGE PRIVATELY OWNED RIGitTS; OR D.

ASSUMES ANY LIABILITIES WITit RESPECT TO T!!E USE OR FOR DAMAGES RESULTIllG FROM Tile USE OF, ANY INFORMATION, APPlaATUS, METil0D OR PROCESS DISCLOSED IN TilIS REPORT.

CENPD - 279 SUPPLEMENT 1

ANNUAL REPORT ON C-E ECCS CODES AND METHODS FOR 10CFR50.46 V

TRANSIENT METHODS AND LOCA NUCLEAR FUEL ENGINEERING FEBRUARY 1990 COMBUS110N ENGINEERING i

C bbLLt.ALL This report describes changes and errors in the Combustion Engineering codes and analysis methodology for ECC5 eialysts in 1999 per the requirements of 10CFR50.46. For this reporting period only one computer code had reportable changes or errors. The corrections and changes did not affect the peak cladding temperature. The cummuletive temperature change for large break LOCA U

is a reduction of less than I f. No changes or errors that affect the peak cladding temperature for small break LOCA have occured. Per the criteria of 10CFR50.46, no action beyond this annual report is required.

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Inhls of Contents 1.0 Introduction 1

2.0 Codes for ECCS Evaluation 2

3.0 Error Corrections and Model Changes in Computer Codes 2

3.1 COMPERC-!!

3 4.0 Conclusions 5

5.0 References 5

11

1.0 Introduction This report addresses the NRC requirernent to report changes or errors in licensed codes for ECCS analysis. The revision to the ECCS Acceptance CriteriaO) spells out reporting requirements and actions required when errors are corrected or changes are made in an evaluation model or in the application of a model for an operating licensee or construction permittee of a nuclear power plant.

The action requirements in s 50.46(a)(3) are:

1. Each applicant for or holder of an operating license or construction permit shall estimate the effcet of any change to or error in an acceptable evaluation nedel or in the.ipplication of such a model to determine if the change er error is significant. For this purpose, a significant change or error is one wnich results in a calculated peak fuel cladding temperature (PCT) different by more than 50 F from the temperature calculated for the limiting transient using the last acceptable model, or is a cumulation of changes and errors such that the sum of the absolute magnitudes of the respective temperature changes is greater than 50 F.
2. For each change to or error discevered in an acceptable evaluation model or in the application of such a model that affects the temperature calculation, the applicant or licensco shall report the nature of the change or error and its estimated effect on the limiting ECCS analysis to the Commission at least annually as specified in 9 50.4. This report is to be filad within one year of discovery of the error and must be reported uch year thereaf ter until a revised evaluation medal or a revised evaluation correcting minor errors is approved by the NRC staff.

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3. If the change or error is significant, the applicant or licensee shall provide this report within 30 days and include with the report a proposed schedule for providing a reanalysis or taking other action as may be needed to show compliance with h 50.46 1

requirements. This schedule may be developed using an integrated scheduling system previously approved for the facility by the NRC.

For those facilities not using an NRC approved integrated scheduling system, a schedule will be established by the NRC staff within 60 days of receipt of the proposed schedule.

4. Any change or error correction that results in a calculated ECCS performance that does not conforn to the criteria set forth in paragraph (b) of 9 50.46 is a reportable cvent as described in 69 50.55(e), 50.72 and 50.73. The affected applicant or licensee shall propose immediate steps to demonstrate compliance or bring plant design or operation into compliance with 5 50.46 requirements.

This report documents all the changes made to the presently licensed C-E LOCA analysis models and methodology which have not been reviewed by the NRC staff. This is specifically to satisfy the requirements described in the secoad item above.

2.0 Codes for ECCS Evaluation C E uses several digital computer codes for ECCS analysis that are described in topical reports, are licensed by the NRC and are covered by the provisions of CFR 50.46. Those for large break LOCA calculations are: CEFLASH 4A, COMPERC-II, PARCH, STRIKIN-II, and COMZlRC. CEFLASH 4AS is used in conjunction with COMPERC-II, STRIKIN-II, and PARCH for small break LOCA calculations.

3.0 Error Corrections and Model Changes in Computer Codes This section discusses all error corrrections or model changes to the itcensed codes which may affect the calculated PCT. Only the COMPERC-Il for a large break has been changed in 1989. No changes to analysis procedures have been made since the last approved submittal to the NRC.

a 2

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l 3.1. COMPERC-Il A. Code Description COMPERC-Il is a FORTRAN digital compt.ter program which is used by Combustion Engineering, Inc. to calculate the core refill and reflood transient portion of a PWR loss of coolant accident (LOCA).

A detailed code description is presented in References 2 through 4.

B. Model Chhnge in COMPERC Il for S1 Spillage The model for the spillage calculation in r.0HPERC Il has been changed to reflect a more realistic physical representation. The change is as described below:

Present Model (Page 10 of Reference 2)

If ZA, MAX < IA 5 2 MAXI A

(IA,HAXI ' IA MAX) 2 ge#A BF A

Nspill

  • W g

spill where Wspill : Rate of water spillage out of the break, Kspill : L ss coefficient for the spillage of water out of the break, A

Flow area in the core, B,F Z
Height of the water in the downcomer, A

ZA, MAX : Distance between bottom of core and bottom of inlet pipe, ZA, MAXI: Distance between bottom of core and top of inlet

pipe, Density of water in the downcomer/ lower plenum, pA a

g

Conversion constant.

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Modificittiqn Equation (1) wat modified as 2

2 ' /2 1

- 2 MAX) 2 g pA A (Z

A A

e B,f Nspill "

(2)

, pl11 The difference between Equations (1) and (2) is the first term of the numerator on the right hand side of the equations. This channe uses the real head term instead of the fixed head term while the mixture level is in the span of the cold leg.

C. Reasons for the Modification As indicated in the previous section, this change reflects a better physical rcpresentation than the model described in Reference 1.

However, a more important reason for this modification is to remove low amplitude flow oscillations introduced by the discontinuity of the fixed head in the old model.

D. Impact of the Spillage Model Change on PCT The change in downcomer spillage head term has the possibility to affect PCT through two effects - reflood rate and two phase level.

Comparison of the reflood rates for cases without id with the change in head term shows that the small oscillat, is in the reflood rate are removed. However, the reflood rate selected for subsequent use is not changed; therefore, there is no change in PCT from this effect. The change in the head term for downccmer spillage also eliminates oscillations in the two ph.se-level but does not change the base two-phase level. Elimination of the oscillations reduces the uncertainty-in the two-p...se level selected for the next step in the analysis. However, due to the small sensitivity of the C-E methodology to two-phase level changes, the change in the two-phase 4

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level due to the change in the head term for spillage has no ef fect on PCT, 4.0 Conclusions The chance to COMPERC-Il has the potential to affect the PCT by changing the reflood rate or the *wo-phase level. However, an evaluation of the reflood rates and effect of the two-phase level for cases before and after the change in head term for the downcomer spillage shows that there is no change in PCT.

The cummulative change in PCT for large break LOCA including that from the previous annual report, Reference 5, is c. reduction of less than 1 F.

There have been no changes in the small break L.0CA results to date.

Therefore, thSre was no significant change in the sense of CFR 50.46 in 1989 and no action beyond the su' omission of this report is needed.

5.0 References y

1. "C,nergency Core Cooling System; Revisions to Acceptance Criterit.,"
10CFR50, Federal Register, Vol. 53, No.180, September 16, 1988.
2. CENPD-134P, "COMPERC-II, A Program for Emergency-Refill-Reflood of the Cc.

Sugust, 1974.

3. CENPD-la4P, Supplement 1, "COMPERC-II, A Program for Emergency Refill-Reflood of the Core (Modifications)," February,1975.
4. CENPD-134, Supplemert 2, "COMPERC-II, A Program for Emergency Refill-Reflood of the Core," June,1985.

3

5. CENPD-279, AnnLal Report on C-E ECCS Codes and Methods for 10CFR50.46, April, 1989.

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1 CENPD - P.79 SUPPLEl4ENT 2

ANNUAL REPORT ON C-E ECCS CODES AND METHODS FOR 10CFR50.46 APRIL, 1991 ABB Combustion Engineering Nuclear Power i

ra 3,;.,.~r ub0100 3W W c

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t LEGAL NOTICE T!!IS REPORT WAS PREPARED AS AN ACCOUNT OF WORK SPollSORED BY AB3 COMBUSTION ENGINEERING.

NEITilER ADP. COMBUST 10N ENGINEERING NOR ANY PERSON ACTING ON ITS BE11ALF:

A.

MAKES ANY WARRANTY OR REPRESENTATION, EXPRESS OR IMPLIED INCLUDING T!!E WARRANTIES OF FITNESS FOR A PARTICUIAR PURPOSE OR MERCHANTABILITY, WITH RESPECT TO THE ACCURACY, COMPLETENESS, OR USEFULNESS OF THE INFORMATION CONTAINED IN T!!IS REPORT, OR T11AT THE USE OF ANY INFORMATION, APPARATUS, METilOD, OR PROCESS DISCLOSED IN Tl!IS REPORT MAY NOT INFRINGE PRIVATELY OWNED RIGHTS; OR B.

ASSUMES ANY LIABILITIES WITH RESPECT TO THE USE OR FOR DAMAGES RESULTING FROM THE USE OF, ANY INFORMATIOtt, APPARATUS, METHOD OR PRCCESS DISCLOSED IN THIS REPORT.

CENPD - 279 SUPPLEMENT 2

ANNUAL REPORT ON C-E ECCS CODES AND METHODS FOR 10CFR50.46 LOCA ANALYSIS ANo METHODS NUCLEAR FUEL ENGINEERING

-APRIL, 1991 N

F

Abstratt

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This report describes changes and errors in the ABB Combustion Engineering codes and analysis methodology for ECCS analysis in 1990 per the requirements of 10CFR50.46. For this reporting period only one computer code had reportable changes or errors. The corrections and changes did not affect the peak cladding temperature. The cumulative temperature change for large break LOCA is a reduction of less than 1 F. No changes or errors that affect tha peak cladding temperature for small break LOCA have occured. Per the criteria of 10CFR50.46, no action beyond this annual report is required.

s

4 lable of Conisniji 1.0 Introduction 1

2.0 Codes for ECCS Evaluation 2

x 3.0 Error Corrections and Model Changes in Computer Codes 2

3.1 BORON 3

4.0 Conclusions 4

5.0 References 5

e ii

t 1.0 Introduction This report addresses the NRC requirement to report changes or errors in licensed codes for ECCS analysis. The revision to the ECCS Acceptance CriteriaII) spells out reporting requirements and actions required when errors are corrected or changes are made in an evaluation m M el or in the application of a model for an operating licensee or construction permittee of a nuclear power plant.

The action requirements in s 50.46(a)(3) are:

1. Each applicant for or holder of an operating license or construction permit shall estimate the effect.of any change to or error in an acceptable evaluation model or in the application of such a model to determine if the change or error is significant. For this purpose, a significant change or error is one which results in e calculated peak fuel cladding temperature (PCT) different by more than 50 F from the temperature calculated for the limiting transient using the last acceptable model, or is a cumulation of changes and errors such that the sum of the absolute magnitudes of the respective temperature changes is-greater than 50 F.
2. For each change to or error discovercd in an acceptable evaluation model or in the application of such a model that affects the temperature calculation, the applicant or licensee shall report the nature of the change or error and its estimated effect on the limiting ECCS analysis to the Commission at least annually as specified in & 50.4.
3. If the change or error is significant, the applicant or licensee shall provide this report within 30 days and include with the report a proposed schedule for:providing a reanalysis or taking other action as may be needed t'o show compliance with s 50.46 requirements. This schedule may be developed using an integrated scheduling system previously approved for the facility by the NRC.

For those facilities not using an NRC approved integrated scheduling 1

system, a schedule will be established by the NRC staff within 60

' days of receipt of the proposed schedule.

4. Any change or error correction that results in a calculated ECCS performance that does not conform to the criteria set forth in paragraph (b) of 9 50.46 is a reportable event as described in hs 50.55(e), 50.72 and 50.73. The affected applicant or licensee shall propose immediate steps to demonstrate compliance or bring plant design or operation into compliance with 9 50.46 requirements.

This report documents all the changes, made in the year covered by this report, to the presently licensed ABB C-E LOCA analysis models and methodology which have not been reviewed by the NRC staff. This document is provided to satisfy the reporting requirements of the second item above.

2.0 Codes for ECCS Evaluation ABB C-E uses several digital computer codes for ECCS analysis that are described in topical reports, are licensed by the NRC, and are covered by the provisions of 10CFR50.46. Those for large break LOCA calculations are CEFLASH-4A, COMPERC-II, PARCH, STRIKIN-II, and COMZIRC. CEFLASH-4AS is used.in conjunction with COMPERC-II. STRIKIN-II, and PARCH for small break LOCA calculations. The codes for post-LOCA long term cooling analysis are BORON, CEPAC, NATFLOW, and CELDA.

3.0 Error Corrections and Model Changes in Computer Codes This'section discusses all error corrrections or model changes to the licensed codes which may affect the calculated PCT. Only the BORON code for long term cooling analysis of large break LOCAs has been changed in 1990. This change was made to correct an error. No changes to analysis procedures have been made since the last approved submittal to the NRC.

2

~.

3.1. BORON A. Code Description BORON is a FORTRAN digital computer program which is used by Combustion Engineering, Inc. to calculate the boric acid concentration in the reactor core after a LOCA. This information is used to determine the point in time, if ever, at whicn boric acid concentration will reach the solubility limit before core flushing is initiated by starting combined hotside/coldside safety injection.

A detailed code description is presented in Reference 2.

B. Coding Error in BORON The coding that calculates the total bnric acid content of the system was found to have the variable VRCS mistyped as VCRS, where VRCS is the mass of solution in the reactor coolant system (RCS).

Correct coding is used if there is a boric acid storage tank (BAST) in the system, if it ernpties after the refueling water tank (RWT),

and if the-BAST can't supply as much water as is being boiled-off in the core. Normally the BAST can't supply as much water as is being boiled off in the core under these conditions. Otherwise, the incorrect coding is used.

The correct and erroneous equations are described below.

Correct Equation (Page C-9 of Reference 2)

BTOTL1 - VRCS*BRCS/100.040.9*VRWT* BRUT /100.0+VSIT*BSIf/100.0 (1)

BTOTAL - BTOTl + BBAST*VBAST/100.0 h

(2) where BTOTAL : Total boric acid mass in system (lbm),

SBAST : Boric acid concentration in BAST-(w/o),

BRCS

Boric acid concentration in RCS (w/o),

1 3

s-1 BRWT

Boric acid concentration in RWT (w/o),

Boric ' acid concentration in safety injection tank BSIT (SIT) (w/o),

VBAST : Mass of solution in BAST (lbm),

VRCS

Mass of solution in RCS (lbm),

VRWT

Mass of solution in RWT (1bm),

VSIT

Mass of solution in SIT (lbm),

Incorrect EcuatipJ1 BTOTL1 - VCRS*BRCS/100.0+0.9'VRWI*BRWT/100.04VSIT*BSIT/100.0 (3)

The difference between Equations.(1) and (3) is the first term on the right hand side of the equations. The error was introduced in 1983 and was detected and corrected in 1990.

C. Impact of RCS Mass Error on PCT The coding error in BORON caused the code to use undefined input for the RCS solution mass for some transients under the conditions described above. This error could affect the PCT by over-predicting the time available before ccre flushing must be initiated to prevent precipitation of boric acid and possible blockage of the coolant channels in the fuel, llowever, an evaluation of the effect of this error for those analyses that were performed with the code version with the erroneous coding shows that precipitation does not occur bafore flushing is started. Since cooling. water circulation is not impeded by_ boric acid precipitation throughout the post-LOCA period, the coding error has no effect on PCT for a large break LOCA.

4.0 Conclusions

' b.

2 The error in BORON had tne potential to affect the PCT by over-predicting the time until core flushing must be initiated. llowever, it is the case that precipitation will not occur before flushing is initiated by 4

t starting combined hotside/coldside safety injection. Consequently, there is no change in PCT for a large break LOCA due to the codo error.

The cumulative change in PCT for large break LOCA including that from the previous annual reports, References 3 and 4, is a reduction of less than I f. There have been no changes in the small break LOCA results to date.

Therefore, there was no significant change in the sense of 10CfR50.46 in 1990 and no action beyond the submission of this report is needed.

5.0 References

1. " Emergency Core Cooling System; Revisions to Acceptance Criteria,"
10CFR50, Federal Register, Vol. 53, No.180, September 16, 1988.
2. CENPD-254-P-A, " Post-LOCA Long Term Cooling Evaluation Model," June, 1980.
3. CENPD-279, " Annual Report an C-E ECCS Codes and Methods for 10CFR50.46," April, 1989.
4. CENPD-279, Suppleraent 1, " Annual Report on C-E ECCS Codes and Methods for 10CFR50.46," february, 1990.

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