ML041560344

Report Pursuant to 10 CFR 50.46, Changes to or Errors in an ECCS Evaluation Model for January - December 2003

ML041560344
Person / Time
Site:	Oconee
Issue date:	05/26/2004
From:	Mccollum W Duke Power Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML041560344 (6)

Text

_ Duke WILLIAM R MCCOLLUM, JR.

_E ovwere VP, Nuclear Support Duke Energy Corporation A Duke Energy Company Duke Power EC07H / 526 South Church Street Charlotte, NC 28202-1802 Mailing Address:

May 26, 2004 P. 0. Box 1006 - EC07H Charlotte, NC 28201-1006 704 382 8983 704 382 6056 fax U. S. Nuclear Regulatory Commission wrrnccoll@duke-energy.com Washington, D. C. 20555-001 Attention: Document Control Desk

Subject:

Duke Energy Corporation Oconee Nuclear Station, Units 1, 2, and 3 Docket Numbers 50-269, 50-270, and 50-287 Report Pursuant to 10 CFR 50.46, Changes to or Errors in an ECCS Evaluation Model

References:

1) Letter, H. N. Berkow (USNRC) to J. Mallay (Framatome ANP), "Evaluation of Framatome ANP Preliminary Safety Concern (PSC) 2-00 Related to Core Flood Line Break and Operator Action Time," (TAC No. MA 9973), April 10,2003.

2) Letter, M. S. Tuckman (DEC) to USNRC, "Report Pursuant to 10 CFR 50.46, Error Related to Application of the LBLOCA Evaluation Model," July 16, 2001.

3) Letter, H. N. Berkow (USNRC) to J. F. Mallay (Framatome ANP), "Issuance of Revised Safety Evaluation for Referencing of Appendices H and I to BAW-101 66P-A, "BEACH - Best Estimate Analysis Core Heat Transfer, A Computer Program for Reflood Heat Transfer Analysis During LOCA," (TAC No. MC0341),

November 7, 2003.

4) Letter, M. S. Tuckman (DEC) to USNRC, "Report Pursuant to 10 CFR 50.46, Error Related to Application of the LBLOCA Evaluation Model," May 31, 2002.

5) Letter, W. R. McCollum, Jr. (DEC) to USNRC, "Report Pursuant to 10 CFR 50.46, Changes to or Errors in an ECCS Evaluation Model," May 19, 2003.

10 CFR 50.46 (a)(3)(ii) requires the reporting of changes to or errors in the Emergency Core Cooling system (ECCS) evaluation models (EM). This report covers the time period from January 1, 2003 to December 31, 2003.

During this time period, two error corrections were made to the application of the evaluation model. Both of these corrections had an impact on the calculated peak cladding temperatures (PCTs) and both are classified as insignificant errors (APCT < 50 0F). The first error is related to an incorrect integrated mass and energy release used in the containment analysis. The calculated containment pressure is used as a boundary condition to the large break LOCA (LBLOCA) analysis. The second error was an incorrect core inlet area used in the BEACH analysis for the Mark-B 10 fuel.

www. dukepower. corn

U. S. Nuclear Regulatory Commission May 26, 2004 Page 2 Included in this report are three summary tables. Table 1 provides the changes/errors for which a PCT impact has been assessed. Table 2 presents changeslerrors for which no PCT impact has been assessed. Table 3 provides a summary of the peak cladding temperatures for all three units.

There are no regulatory commitments associated with this letter.

Please address any comments or questions regarding this matter to L. B. Jones at (704) 382-4753.

Very truly yours, W. R. McCollum, Jr.

Attachments Table 1 - Errors/Evaluation Model Changes with PCT Impact Table 2 - Errors/Evaluation Model with no PCT Impact Table 3 - Peak Cladding Temperature Summary - Oconee Units 1,2, and 3 xc (with Attachments)

L. A. Reyes, Regional Administrator U. S. Nuclear Regulatory Commission, Region II Sam Nunn Atlanta Federal Center 61 Forsyth St., SW, Suite 23T85 Atlanta, GA 30303-8931 L. N. Olshan (addressee only)

NRC Senior Project Manager U. S. Nuclear Regulatory Commission Mail Stop 0-8 H12 Washington, DC 20555-0001 M. C. Shannon NRC Senior Resident Inspector Oconee Nuclear Station

Table 1 Errors / Evaluation Model Changes with PCT Impact Error Correction for Containment Pressure Input An error was discovered in the mass and energy release data input to the CONTEMPT containment analysis. The error originates from allowing the CONTEMPT code to linearly interpolate in the mass and energy data that was generated over distinct time intervals. This results in the CONTEMPT integrated mass and energy release that is not consistent with the system analysis. The net impact is that the containment pressure is overpredicted. Lowering the containment pressure increases the CFT injection flow during the refill period which shortens the adiabatic heat-up period. This leads to a reduction in the calculated PCT. The PCT impact for this error correction is estimated to be -25 0 F.

Error Correction for BEACH Junction Area An error was discovered in the junction area between the core region and the lower plenum region for the Mark-B1 OT LBLOCA analyses. Correction of the error resulted in a slightly lower core reflood rate. The PCT change for this error correction is estimated to be +30F.

Table 2 Errors / Evaluation Model Changes with no PCT Impact Reactor Coolant Pump Degradation Model Change Preliminary Safety Concern (PSC) 2-00 investigated small break LOCAs (SBLOCAs) with reactor coolant pump (RCP) operation beyond the time of turbine trip. It was discovered that more severe consequences could be predicted for larger SBLOCA events when the RCPs were manually tripped at two minutes following loss-of-subcooling margin. In addition, the consequences were even worse when the M3-modified RCP degradation model (lower bound providing least pump degradation) was applied. The NRC, in Reference 1, approved the use of the M3-modified two-phase RCP degradation model in RELAP5/MOD2-B&W for resolution of PSC 2-00. This approval is contingent upon establishing that the M3-modified curve is conservative for each licensee's plant. This material is currently being reviewed and the NRC submittal is being prepared. Use of the M3-modified RCP degradation model was previously reported as an EM change in 2001. Thus, there is no new PCT impact associated with this change.

BEACH Topical Report Revision AREVA (formerly Framatome-ANP), submitted a revision to the BEACH topical report for LBLOCA analyses to extend the range of application for 1) the maximum initial cladding limit to 20450F, 2) the minimum reflood rate to 0.4 in/sec, and 3) the minimum applicable containment pressure to 14.7 psia. The extension of the initial cladding temperature limit was previously reported in Attachment 1 of the 2000 10 CFR 50.46 annual report (Reference 2). In Reference 3 the NRC approved revision 5 of the BEACH topical report, BAW-1 01 66P, and its use with once-through steam generator LBLOCA evaluation models, BAW-1 01 92P-A. For this evaluation model change there is no APCT determined since the analysis of record calculations are unaffected. The only change is to extend the applicable range of the BEACH computer code.

Table 3 Peak Cladding Temperature Summary - Oconee Units 1, 2 & 3 LBLOCA PCT (0F) Comments Evaluation model: RELAP5/MOD2-B&W _ ___II 2037 Mark-B111 (M5),16.8 kWM Analysis of record PCT At 6.021 ft elevation 2050 Mark-B1 OT, 16.8 kWM At 4.264 ft elevation Prior errors (APCT)

1. None 0 Prior evaluation model changes (A&PCT)

1. None 0 Errors (APCT) (PCT impacts estimated)

1. Containment press. correction -25 Applies to both fuel types

2. BEACH inlet area correction +3 Applies to only Mark-B10 Evaluation model changes (APCT)

1. None 0 Absolute value of errors/changes for this report 25 Mark-Bi 1 (APCOT) 28 Mark-B1lOT Net change in PCT for this report -25 Mark-Bi 1

-22 Mark-B1lOT Final PCT 2012 Mark-B11 2028 Mark-B1lOT SBLOCA PCT (IF) Comments Evaluation model: RELAP5/MOD2-B&W Analysis of record PCT 1369 Full Power 0.15 ft2 break Prior errors (APCT)

1. Change from min to max CFT level 43 Reference 4()

2. SG primary tube region drag model input error -14 Reference 4

3. Limiting RCP type & two-phase degradation model(PSC 1-99) -5 Reference 4

4. RELAP5 water property and Unix operating system -25 Reference 4

5. Implementation of void-dependent cross flow model -12 Reference 5 Prior evaluation model changes (APCT)

1. None 0 Errors (APCT)

1. None 0 Evaluation model changes (APCT)

1. None Absolute value of errors/changes for this report (APCT) 0 Net change in PCT for this report 0 _ _

Final PCT 1356

SBLOCA PCT (0F) Comments Analysis of record PCT 1261 Reduced Power - 50% FP (1HPI case) 0.06 ft2 break Prior errors (APCT)

1. None 0 Prior evaluation model changes (APCT)

1. None 0 Errors (APCT)

1. None 0 Evaluation model changes (APCT)

1. None 0 Absolute value of errors/changes for this report (APCT) 0 Net change in PCT for this report 0 Final PCT 1261 (1) In Reference 4 this PCT change was listed as an estimate since it was based on calculations using a model that was under review (void-dependent cross-flow model). Given that this model is now approved, the APCT value is no longer considered an estimate.