NRC 2005-0053, ECCS Evaluation Model Changes
| ML051230202 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 04/25/2005 |
| From: | Koehl D Nuclear Management Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NRC 2005-0053 | |
| Download: ML051230202 (4) | |
Text
NMCA Committed to Nuclear Excellence Point Beach Nuclear Plant Operated by Nuclear Management Company, LLC April 25, 2005 NRC 2005-0053 10 CFR 50.46 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington DC 20555 Point Beach Nuclear Plant, Units 1 and 2 Dockets 50-266 and 50-301 License Nos. DPR-24 and DPR-27 ECCS Evaluation Model ChanQes, 10 CFR 50.46 As required by 10 CFR 50.46(a)(3)(ii), Nuclear Management Company, LLC (NMC), is submitting this annual report of changes to, and errors discovered in, emergency core cooling system (ECCS) evaluation models for Point Beach Nuclear Plant (PBNP)
Units 1 and 2. This letter is intended to provide a summary of ECCS evaluation model changes and errors identified since our previous annual report dated April 12, 2004 (NRC-2004-0038). Model changes include changes to the large break loss of coolant accident (LOCA) model and the small break LOCA model. Changes are summarized below with additional details and a summary sheet of peak cladding temperature (PCT) margin provided in the enclosure.
For PBNP Units 1 and 2, there is one evaluation model PCT change in assessment for the large break LOCA analysis, and no changes in assessment to the small break LOCA analysis. The change for the large break LOCA analysis resulted in a +5° F penalty being assessed against the reported PCT. The enclosure provides a more detailed discussion of the change.
Current PCT rack-up sheets are provided in the enclosure to this letter.
There are no new commitments contained in this submittal.
Dennis L. Koehl Site Vice-President, Point Beach Nuclear Plant Nuclear Management Company, LLC 6590 Nuclear Road
- Two Rivers, Wisconsin 54241 Telephone: 920.755.2321
,0J
Document Control Desk Page 2
Enclosure:
ECCS Evaluation Model Changes and Errors cc:
Regional Administrator, Region Ill, USNRC Project Manager, Point Beach Nuclear Plant, USNRC Resident Inspector, Point Beach Nuclear Plant, USNRC PSCW
ENCLOSURE ECCS EVALUATION MODEL CHANGES AND ERRORS POINT BEACH NUCLEAR PLANT, UNITS 1 AND 2 Large Break LOCA Evaluation Model The Large Break LOCA evaluation model assessment change is referred to as the "Revised Blowdown Heatup Uncertainty Distribution". Essentially, Westinghouse corrected "modeling inconsistencies and input errors" in the LOFT input decks, and reanalyzed the LOFT and ORNL tests using the current version of WCOBRAITRAC. The result is revised heatup heat transfer coefficients and cumulative distribution function during the blowdown phase of the LOCA. This was reported to the NRC by Westinghouse (LTR NRC-04-1 1). The overall code uncertainty for blowdown was also recalculated and programmed into a new version of MONTECF. The overall code uncertainty for the reflood phase was not affected. However, the reflood phase PCT does have a small assessment adjustment as a result of the changes during the blowdown phase.
The estimate of the PCT effect of these changes for Point Beach is 50 F. The total cumulative change in the PCT from the analysis of record is now 170 F, as indicated on the attached PCT rack-up sheets.
Small Break LOCA Evaluation Model There were no changes or errors to the Small Break LOCA evaluation model during this reporting period that resulted in a change to the calculated PCT for Point Beach Nuclear Plant.
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LARGE BREAK PEAK CLADDING TEMPERATURE MARGIN UTILIZATION FOR BELOCA PBNP Units 1 & 2:
A.
Analysis of Record (11/2000)
B.
Prior Permanent ECCS Model Assessments
- 1. MONTECF Decay Heat Uncertainty Factor C.
Planned Plant Change Evaluations
2004 10 CFR 50.46 Model Assessments E.
Temporary ECCS Model Issues (none)
F.
Other Margin Allocations (none)
Licensing Basis PCT + Margin Allocations PCT =
21280F APCT=
APCT =
APCT =
APCT =
APCT=
PCT =
40F 80F 50F 00F 00F 21450F SMALL BREAK PEAK CLADDING TEMPERATURE MARGIN UTILIZATION (Three Inch Cold Leg)
PBNP Units 1 & 2:
A.
Analysis of Record (11/2000)
B.
Prior Permanent ECCS Model Assessments
- 1. NOTRUMP Mixture Level Tracking/Region Depletion
- 2. NOTRUMP Bubble Rise/Drift Flux Model Inconsistency C.
Planned Plant Change Evaluations (none)
D.
2004 10 CFR 50.46 Model Assessments (none)
E.
Temporary ECCS Model Issues (none)
F.
Other Margin Allocations (none)
Licensing Basis PCT + Margin Allocations
- Unit 1/Unit 2 respectively PCT = 11570F/10460 F APCT =
130F APCT =
350F APCT =
00F APCT =
00F APCT =
0F APCT =
0F PCT = 1205°F / 1094°F Page 2 of 2