ML13266A108

30-Day Report of a Significant Change in the Loss-of-Coolant Accident(Loca)/Emergency Core Cooling System (ECCS) Models Pursuant to 10 CFR 50.46

ML13266A108
Person / Time
Site:	Fort Calhoun
Issue date:	09/20/2013
From:	Cortopassi L Omaha Public Power District
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
LlC-13-0133
Download: ML13266A108 (4)

Text

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DjjjjD Omaha Pub/it: Power DIstrict 444 South 1(11' Street Mall Omaha, NE 68102-2247 September 20,2013 LlC-13-0133 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555

References:

1. Docket 50-285

2. EMF-2328(P)(A), Revision 0, "PWR Small Break LOCA Evaluation Model, S-RELAP5 Based," Framatome ANP, INC., March 2001

3. EMF-2103(P)(A), Revision 0, "Realistic Large Break LOCA Methodology for Pressurized Water Reactors," Framatome ANP, Inc., April 2003.

4. Letter from OPPD (J. B. Herman) to NRC (Document Control Desk), Annual Report for 2011 Loss-of-Coolant Accident/Emergency Core Cooling System (ECCS) Models pursuant to 10 CFR 50.46, dated April 27, 2012 (LlC-12-0053)

5. Letter from OPPD (L. P. Cortopassi) to NRC (Document Control Desk), Annual Report for 2012 Loss-of-Coolant Accident/Emergency Core Cooling System (ECCS) Models pursuant to 10 CFR 50.46, dated April 30, 2013 (LlC-13-0056)

Subject:

30-Day Report of a Significant Change in the Loss-of-Coolant Accident (LOCA)/Emergency Core Cooling System (ECCS) Models Pursuant to 10 CFR 50.46 In accordance with 10 CFR 50.46(a)(3)(ii), the Omaha Public Power District (OPPD) is submitting a 30-day 10 CFR 50.46 report of a significant change in the Small Break Loss-of-Coolant Accident (SBLOCA) ECCS model and evaluation. 10 CFR 50.46(a)(3)(i) states: for this purpose: a significant change or error is one that 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 modeJ, 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.

Omaha Public Power District communicated to AREVA the need to evaluate a High Pressure Safety Injection (HPSI) flow reduction for the SBLOCA and Realistic Large Break (RLB) LOCA analyses as the result of a modification needed to prevent HPSI pump runout. This modification is currently undergoing system acceptance review by plant personnel.

The attached report identifies a change in the SBLOCA analysis in which a reduction in the credited HPSI flow rate has increased the expected PCT from the event. The RLBLOCA has not been adversely affected but is also reported for completeness.

There are no regulatory commitments contained in this submittal.

Employment with Equal Opportunity

U. S. Nuclear Regulatory Commission LlC-13-0133 Page 2 If you should have any questions, please contact Mr. Bill Hansher at (402) 533-6894.

ouis P. Cortopassi Site Vice President and CNO LPC/TAH/brh Attachment c: S. A. Reynolds, Acting NRC Regional Administrator, Region IV J. M. Sebrosky, NRC Senior Project Manager L. E. Wilkins, NRC Project Manager J. C. Kirkland, NRC Senior Resident Inspector

L1C-13-0133 Attachment Page 1 Evaluation of the Reduction of HPSI Delivery Flow for RLBLOCA Analysis For the RLBLOCA analysis, the timing of the event, the overall contribution of HPSI flow compared to total ECCS flow, and the reactor vessel downcomer inventory have been evaluated to assess the impact of the HPSI flow reduction. As a result of the evaluation, the HPSI flow reduction has been determined to have no impact on the Analysis of Record (AOR) limiting PCT. The PCT for RLBLOCA is 1581°F.

For the purpose of 10 CFR 50.46, no change occurred in the RLBLOCA, but the current RLBLOCA AOR estimated changes are greater than 50°F. OPPD plans to submit a new RLBLOCA analysis using Revision 3 of Reference 3 within one year of its approval by the NRC. (AR 60118)

Evaluation of the Reduction of HPSI Delivery Flow for SBLOCA Analysis The SBLOCA analysis has been re-evaluated to quantify the impact of the HPSI flow reduction.

In the AOR, the limiting break size reported corresponds to a 3.5 inch diameter break. With the HPSI flow reduction, the new limiting break size was identified as a 3.0 inch diameter break. The smaller break deploys the safety injection tanks later, due to the slower primary system depressurization. This effect, combined with the reduction in HPSI flow, contributes to the rise in the limiting PCT.

The PCT impact of the HPSI flow reduction for the Fort Calhoun SBLOCA AOR is +309°F. In combination with changes/errors from previous years, this +309°F changes the SBLOCA from the baseline value (153rF) reported in the FCS USAR to 1746°F.

Evaluation of the Reduction of HPSI Delivery Flow with Methodology Changes for SBLOCA Analysis In light of the recent NRC request for the Millstone Nuclear Power Plant (ML13074A795 and ML13192A102), AREVA re-analyzed the SBLOCA event with the HPSI flow reduction while incorporating the items introduced in Supplement 1 of Reference 2 which have the largest impact on the transient. Specifically, the following items were incorporated:

• Spectrum of break sizes analyzed according to the Supplement 1 of Reference 2.

• Loop seal clearing according to Supplement 1 of Reference 2.

• Core bypass model: the gaps identified in Supplement 1 of Reference 2 are assumed closed for the entire simulation.

The evaluation includes the methodology changes and the HPSI flow reduction. The SBLOCA analysis utilizing the changes above from Supplement 1 of Reference 2 resulted in a new limiting PCT of 1513°F (a decrease of 233°F) for a 3.4 inch break. This PCT addresses all the items in the rack-ups reported since 2006.

L1C-13-0133 Attachment Page 2 Large Break LOCA Margin Summary Sheet Plant Name: Fort Calhoun Station, Unit No.1 Utility Name: Omaha Public Power District Evaluation Model: Large Break LOCA Net PCT Effect Absolute

(~PCT) PCT Effect Prior 10 CFR S0.46 Changes or Error Corrections -SsoF 8soF A.

- Previous Years 10 CFR S0.46 Changes or Error Corrections - OaF B. +O°F HPSI Pump Runout Prevention Modification C. Absolute Sum of 10 CFR S0.46 Changes 8soF The sum of the PCT from the most recent analysis using an acceptable evaluation model and the estimates of the PCT impact for changes and errors identified since this analysis is less than 2200°F. The Net PCT Effect was reported incorrectly in the 2012 report as -62°F (Reference S).

The Net PCT reported in the 2011 report (Reference 4) was -62°F for previous years, +8°F for the current year, which results in a -S4°F for net effects. An additional Net PCT Effect of -1°F change resulting from a SO.S9 activity (Cycle 2S core bypass change) implemented in 2008 resulting in the Net PCT Effect of -SsoF. This also results in an Absolute PCT Effect of 8soF versus 84°F reported in Reference S. This reporting error has been entered into the FCS corrective action program.

Small Break LOCA Margin Summary Sheet Plant Name: Fort Calhoun Station, Unit No.1 Utility Name: Omaha Public Power District Evaluation Model: Small Break LOCA Net PCT Effect Absolute

(~PCT) PCT Effect Prior 10 CFR S0.46 Changes or Error Corrections A. -100°F 108°F

- Previous Years 10 CFR S0.46 Changes or Error Corrections -

B. +309°F 309°F HPSI Pump Runout Prevention Modification C. Absolute Sum of 10 CFR S0.46 Changes 417°F The sum of the PCT from the most recent analysis using an acceptable evaluation model and the estimates of the PCT impact for changes and errors identified since this analysis is less than 2200°F