ML082130096
| ML082130096 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 07/29/2008 |
| From: | Geer T Duke Energy Carolinas, Duke Energy Corp |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML082130096 (5) | |
Text
P Duke THOMAS C. GEER D k Vice President ci2Energy Nuclear Engineering Duke Energy Corporation 526 South Church St.
Charlotte, NC 28202 July 29, 2008 Mailing Address:
EC08H / PO Box 1006 Charlotte, NC 28201-1006 U. S. Nuclear Regulatory Commission 704 382 4712 Washington, D. C. 20555-0001 704 382 7852 fax Attention: Document Control Desk tcgeer@duke-energy. com
Subject:
Duke Energy Carolinas, LLC 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 Evaluation Model 10 CFR 50.46 (a)(3)(ii) requires the reporting of changes to or errors in the Emergency Core Cooling (ECCS) evaluation model (EM). This report covers only a six month time period from July 1, 2007 to December 31, 2007 in order to return to a regular calendar year reporting period. The last report covered an 18-month time period from January 1, 2006 to June 30, 2007.
During this time reporting period, there were three errors identified in the application of the large break loss of coolant accident (LBLOCA) EM. All three errors were related to the CONTEMPT analyses, which provide the containment pressure response as input into the Mk-B1 1 LBLOCA peak clad temperature (PCT) analyses. These errors were (1) an input error in the curve fit to model the heat removed by the reactor building cooling units (RBCUs), (2) an incorrect time step in the mass and energy release rate inputs, and (3) an incorrect final containment response value at 0.21 seconds due to a typographical error. AREVA determined the limiting LBLOCA PCT results were not affected by any of these errors.
There were also four plant changes identified during this time reporting period. Three of these plant changes needed evaluation with respect to the CONTEMPT analyses and the LBLOCA EM. The plant changes needing further evaluation using the CONTEMPT code were (1) a change in the maximum RBCU heat removal rate, (2) a 10°F decrease (1 00°F to 900F) in the expected average containment temperature during nol-mal operation, and (3) a reduction in reactor building (RB) spray flow to 2500 gpm. AREVA determined the limiting LBLOCA PCT results were not affected by any of these plant changes.
The fourth plant change was a minor fuel design change to be carried forward beginning with the Oconee Unit 3 startup in the fall of 2007. O-conee fuel batches began incorporating minor changes to the blanket fuel pellet dish and Chamfer geometry as well as changes to the upper end cap and plenum spring. These minor changes affected the dish volume fraction, the axial blanket enrichment, the effect of the upset shape weld to the cladding length, and the plenum volume modeled in the TACO3 www. duke-energy. corn O
V -
U.S. Nuclear Regulatory Commission July 29, 2008 Page 2 LOCA initialization cases. The net result was a calculated fuel temperature increase that remained well within the 20°F variation allowed by the LBLOCA EM to account for variations in the calculated and input parameters from the TACO3 fuel rod mechanical code. Therefore, the limiting LBLOCA PCT results were not affected by this minor fuel design change.
Included in this report is a PCT summary table for Units 1, 2, and 3. Included are errors reported above as well as errors and/or EM changes from prior years as they relate to the current EM. Since plant changes are not considered errors or EM changes, and there were no resultant PCT impact due to these specific plant changes, these are not listed in the PCT summary table. Also, as evident in the attached PCT summary table, the small break loss of coolant accident (SBLOCA) EM reporting is unaffected by the aforementioned errors and plant changes.
Also note Mk-B1 OT fuel is no longer reported in the attached PCT summary table.
During this time reporting period, Oconee Unit 3 was the only unit to operate with Mk-B10T fuel. However, the Mk-B10T fuel type in Oconee Unit 3 is clearly non-limiting during this time reporting period as eight Mk-B1OT assemblies were completing their fourth cycle of operation.
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.
Sincerely, Thomas C. Geer Vice President, Nuclear Engineering Attachment Table 1 - Peak Cladding Temperature Summary - Oconee Units 1, 2, and 3
U.S. Nuclear Regulatory Commission July 29, 2008 Page 3 L. A. Reyes, Region II Administrator U.S. Nuclear Regulatory Commission Sam Nunn Atlanta Federal Center, 23 T85 61 Forsyth St., SW Atlanta, GA 30303-8931 L. N. Olshan, Senior Project Manager (ONS)
U. S. Nuclear Regulatory Commission 11555 Rockville Pike Mail Stop 0-8 G9A Rockville, MD 20852-2738 G. A. Hutto, NRC Senior Resident Inspector Oconee Nuclear Station
ATTACHMENT Table 1 - Peak Cladding Temperature Summary - Oconee Units 1, 2, and 3
Table 1: Peak Cladding Temperature Summary - Oconee Units 1, 2, and 3 LBLOCA PCT(°F)
Comments Evaluation model: RELAP5/MOD2-B&W Analysis of record PCT 2035 Mark-B11 (M5), 17.7'kW/ft at 6.021 ft elevation Prior errors (APCT)
- 1. Energy Deposition Factor 0
Reference A (see below)
Prior evaluation model changes (APCT)
- 1. None 0
Errors (APCT)
- 1. Input error to RBCU heat removal rate curve fit 0
- 2. CONTEMPT mass and energy input time step 0
- 3. Typo on containment pressure response value 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
Comments Evaluation model: RELAP5/MOD2-B&W Analysis of record PCT 1461 Full Power -100% FP (2 HPI Case) 0.15 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
Comments Analysis of record PCT 1774 Reduced Power - 75% FP (1 HPI case) 0.075 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 1774 Reference A: letter, T. C. Geer (Duke) to USNRC, "Report Pursuant to 10 CFR 50.46, Changes to or Errors in an ECCS Evaluation Model", December 18, 2007.