ML20198J670
| ML20198J670 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 10/16/1997 |
| From: | Cruse C BALTIMORE GAS & ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9710210243 | |
| Download: ML20198J670 (4) | |
Text
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i C=sts 11. Ce.tsi:
lithimore Gas and Electric Company Vice President Cahen Cliffs Nuclear Power Plant Nuclear Energy 1650 Calven Clif fs Parkway Lusby, htar) land 20657 410 495-4455 October 16,1997 U. S. Nuclear Regulatory Commission Washington, DC 20555 ATTENTION:
Document Control Desk
SUBJECT:
Calvert Cliffs Nuclear Power Plant Unit Nos.1 & 2; Docket Nos. 50 317 & $0 318 Report of a Significant Error in Emergency Core Cooling System Evaluation
(
Model as Requited by 10 CFR 50.46 MEFERENCES:
(a)
Letter from 1. C. Rickard (ABB CE) to NRC, dated August 14, 1997, j
Report Pursuant to 10 CFR 21 Regarding Error in the Energy Redistribution Factor used in LOCA Analysis (b)
CE Report CENPD 132P, " Calculative Methods for the C E Large Break LOCA Evaluation Model," August 1974 (c)
Combustion Engineering infobulletin No. 97-04, Revision 01, " Potential Error in the Energy Redistribution Factor U i in LOCA Analysis,"
July 11,1997 in accordance with the requirements of 10 CFR 50,46, this is a report of a signincant error in the Emergency Core Cooling System evaluation model used at Calvert Cliffs. As previously reported in Reference (a), the Energy Redistribution Factors (ERF) used by Asea Brown Boveri Combustion Engineering (ABB-CE) in the large break loss-of coolant accident (LOCA) analyses do not reDect the effects of moderator voiding. The c0'ects of moderator voiding on the ERF had been accounted for in it:
Nuclear Regulatory Commission approved Large Break LOCA Evaluation Model Topical Report, Reference (b), llowever, moderator voiding was not accounted for when ERP calculations were revised in 1975 to account for lower hot rod pin / box ratios.
Calculations have been performed by ABB-CE using current fuel designs and their current Monte Carlo computer code for photon transport to quantify the effect of moderator voiding on the ERF. The results of these calculations were initially forwarded to Baltimore Gas and Electric Company (BGE) on i
September 17,1997 and formally transmitted to BGE by Attachment (1). The results indicate that the p l
97102iO'243'971016 PDR ADOCK 05000317 fih
9 Document Control Desk October 16,1997 Page 2 i
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effect of moderator voiding is to increase the ERF for the Calvert Cliffs 14x14 fuel lattice and limiting pin / box ratio by 1.3 percent. Asea Brown Boverl-Combustion Engineering estimates that the effect of an increase in the ERF of 1.3 percent is an increase of 52'F in the large break LOCA peak clad temperature (PCT) for Calve:1 Cliffs. This estimate is based on a typleal plant where the limiting PCT occurs during the re0ood phase of the event. The small break LOCA analysis is not affected by the ERF error.
When BGB was initially notified of the potential ERF error by Reference (c), immediate action was taken, as recommended by ABB CE, to maintain the conservatism of the current large break LOCA analysis of record. On July 12,1997 BGE established administrative controls to reduce limits on the total planar radial peaking factor ( F[,) by 2 percent if monitoring linear heat rate using excore detectors, and to reduce the limit on Peak Linear llent Rate by 0.2 kW/fl if monitoring linear heat rate using incore detectors. These actions provided, and continue to provide, assurance that the PCT of the Calvert Cliffs large break LOCA analysis of record (2143'F) is conservative, that the 10 CFR 50.46 Emergency Core Cooling System performance criteria (i.e., PCT shall not exceed 2200*F) are met, and that the Emergency Core Cooling System is OPERABLE. Baltimore Gas and Electric Company plans to perform a plant specl0c re analysis of large break LOCA within the next four months. This revised analysis will provide the final design basis for core operating limits and conformance with 10 CFR 50.46 requirements.
Should you have questions regarding this matter, we will be pleased to discuss them with you.
Very truly yours, 2
/
^7 L%
for N
C.11. Cruse Vice President - Nuclear Energy CllC/RCG/bjd
Attachment:
(1)
Letter from J. Baum (ABB-CE) to W. J. Lippold (BGE), dated October 2,1997, 10 CFR 21 Concern on the Energy Redistribution Factors Used in the ECCS Performance Analysis cc:
R. S. Fleishman, Esquire
- 11. J. Miller, NRC J. E. Silberg, Esquire Resident inspector, NRC Director, Project Directorate 1 1, NRC R.1. McLean, DNR A. W. Dromerick, NRC J.11. Walter, PSC
A Hi October 2,1997 B 97156 Mr. W. J. Lippold Baltimore Gas & Electric 1650 Calvert Clift Parkway Lusby, MD 20657 Subject 10 CFR 21 CONCERN ON TIIE ENERGY REDISTRIBUTION FACTORS USED IN TIIE ECCS PERFORMANCE ANALYSIS Reibrence:
- 1. Combustion Engineering h fobullctin No. 97-04 Rev 01, " Potential Ermr in the t
Energy Redistribution Factor Used in LOCA Analysis," dated July 11,1997.
- 2. '. C. Rickard (ABB) Letter to NRC, LD 97-024, Report Pursuant to 10 CFR 21 Regarding Error in the Energy Redistribution Factor Used in LOCA Analysis,"
dated August 14,1997
Dear Mr. Lippold:
On 7/11/97, ABD issued the Reference ! Infobulletin which reported the initiation of a 10 CFR 21 evaluation of the Energy Redistribution Factors (ERFs) used in the ECCS performance analyses using ABB's large and small break LOCA ECCS performance evaluation models. This evaluation was initiated because of concerns raised regarding whether voiding had been considered in determining ERFs, and prompted ABB to make interim recommendations concerning margin to PLHGR limits. ABB's prelinhary fmdings, confirmed that voiding had been neglected in the ERFs employed in the large break LOCA analysis (LBLOCA), and estimated that the EFRs were understated by 0.5 to 1.5%, corresponding to a underestimation of PCT in the LBLOCA of between 20 and 60 degrees. ABB subsequently reported this error to the NRC pursuant to the requirements of 10 CFR 21 on August 14,1997 (Reference 2).
This letter provides the fmal results of the evaluation of the ERFs. This information was presiously released via e-mail distribution as " Status Update #4 on 10 CFR 21 Concem.. " on September 17,1997 Additional information was similarly provided by e mail on July 16, July 31 and August 15,1997. Copies of the four e-mail updates and the two References are enclosed.
As previously reported, the 1975 generated curve of ERFs as a function of pin / box peaking factor neglected to include the efTects of voiding that occurs during the LOCA event, LBLOCA analyses employed this curve in conjunction with a 0.8% allowance for uncertainty. This curve, including the associated uncertainty, has now been regenerated using the !(CNP i,tonte Carlo code for both 14X14 and 16X16 lattice types.
The net difference between the 1975 ERFs (including uncertainties) and the MCNP results (including uncertainties) varies somewhat as a function of pin / box factor and lattice type. The changes in ERFs are summarized in the table below for the range of pin /bu.. factors obsened in current designs. Bis table also prosides the efTect on peak clad temperature (PCT). He effect on PCT of a change in ERF was detemuned for a typical plant where the limiting PCT occurred during the re0ood phase of the event. A sensitivity of about 40 degrees F PCT per 1% change in ABB CENO Fuel Operations Comouston Eng noenng ine PO Bc4 500 Teiephone (660) 687 8001 2000 Day He %ad Fas (860) 687-8167 Wedsor CT 06095-c',00
Mr. W. J. Lippold B 97156 10/2/97 Page 2 the ERF was observed. He sensitisity of PCT to ERF rnay be somewhat plant specific, but the quoted sensitisity isjudged to be representative.
16 X 16 14 X 14 Pin / Box Change Change Change Change ERF,%
PCT,F 1.03 1.0 40 1.3 52 1.10 0.7 28 1.0 40 i
The sum of the absolute changes in PCT due to modifications and errors in the ABB ECCS evaluation model was less than one degree prior to correction of the error in ERFs. Consequently, the change in PCT including correction of the ERFs results in a total change in PCT that is less than 50 F, and thus is not reportable under the 30 day provision of 50.46, for the LDLOCA analyses of plants with 16X16 lattices. The Calvert Cliffs analysis (the only analysis for the 14X 14 lattice) employed a pin / box factor of 1.03, nerefore, this error is reportable under the 30 day provision for Calvert Cliffs.
please do not hesitate to contact me at 860-687 8010 or Dr. Norton Shapiro at 860 285-4420 if there are any questions regarding thi. infonnation.
Sincerely, CohmusnoN ENGINEERINO, INC.
6L{Jl&
hn Baum roject Manager, Fuel Operations w/gbge/b97156/JB:ms Distnbution (All w/ene)
J.
M. Cleary 9612 1916 R. O. Doney
$3181911 P. A. File BGE M. T. Finley BGE J.
D. Isakson ABB at Calvert Cliffs J.
A. Mihalcik BGE I.
C. Rickard 9488 1905 N. L Shapiro 5318 1917 D. J.
Wotus
$3181915
.