ML11165A221

Day Report Pursuant to 10 CFR 50.46, Acceptance Criteria for Emergency Core Cooling Systems for Light-Water Nuclear Power Reactors

ML11165A221
Person / Time
Site:	Nine Mile Point
Issue date:	06/06/2011
From:	Sterio A Constellation Energy Group
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML11165A221 (6)

Text

P.O. Box 63 C EN G S.

a joint venture of Lycoming, New York 13093 Constellation eDF NINE MILE POINT NUCLEAR STATION June 6, 2011 U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 ATTENTION: Document Control Desk

SUBJECT:

Nine Mile Point Nuclear Station Unit No. 1; Docket No. 50-220 30-Day Report Pursuant to 10 CFR 50.46, Acceptance Criteria for Emergency Core Cooling Systems for Light-Water Nuclear Power Reactors In accordance with 10 CFR 50.46(a)(3)(ii), Nine Mile Point Nuclear Station, LLC (NMPNS) hereby provides notification of a significant change to and errors in the Nine Mile Point Unit 1 (NMP1)

Emergency Core Cooling System (ECCS) evaluation model.

10 CFR 50.46(a)(3)(ii) requires that a significant change to or error in an ECCS evaluation model be reported to the NRC. A significant change or error is one that results in a calculated peak cladding temperature (PCT) different by more than 50'F from the temperature calculated using the last acceptable model 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.

On May 3, 2011, NMPNS was informed by its fuel vendor (GE Hitachi (GEH)) of a change in its ECCS evaluation model PCT calculation that could affect NMP1. This change was required to address three individual errors and a model change identified by GEH for the previous calculation of record. On May 6, 2011, based on the information provided by GEH, NMPNS determined that correction of one of the identified errors resulted in a greater than 50'F increase in calculated PCT. Also, the sum of the absolute magnitudes of the respective temperature changes due to the three individual errors and the model change was greater than 50'F. Therefore, the error(s) and model change meet the 30-day reporting requirements delineated in 10 CFR 50.46(a)(3)(ii).

The Attachment provides a description of the errors and model change, the actions taken, and a tabular summary of the impact on the calculated PCT.

1~ Document Control Desk June 6, 2011 Page 2 There are no regulatory commitments in this submittal.

Should you have questions regarding the information in this submittal, please contact John J. Dosa, Director Licensing, at (315) 349-5219.

Very truly yours, Alex D. Sterio Manager Engineering Services -

Acting ADS/JMT

Attachment:

10 CFR 50.46 ECCS Evaluation Model - Errors and Model Change cc: Regional Administrator, NRC Project Manager, NRC Resident Inspector, NRC

ATTACHMENT 10 CFR 50.46 ECCS EVALUATION MODEL - ERRORS AND MODEL CHANGE Nine Mile Point Nuclear Station, LLC June 6, 2011

ATTACHMENT 10 CFR 50.46 ECCS EVALUATION MODEL - ERRORS AND MODEL CHANGE On May 3, 2011, Nine Mile Point Nuclear Station, LLC (NMPNS) was informed by its fuel vendor (GE Hitachi (GEH)) of a change in its Emergency Core Cooling System (ECCS) evaluation model peak clad temperature (PCT) calculation that could affect Nine Mile Point Unit I (NMP1). This change was required to address three individual errors and a model change identified by GEH for the previous calculation of record. On May 6, 2011, based on the information provided by GEH, NMPNS determined that correction of one of the identified errors resulted in a greater than 50'F increase in calculated PCT.

Also, the sum of the absolute magnitudes of the respective temperature changes due to the three individual errors and the model change was greater than 50'F. Therefore, the errors and model change meet the 30-day reporting requirements delineated in 10 CFR 50.46(a)(3)(ii). A description of the four individual notifications regarding the ECCS evaluation model, as detailed by the vendor, is as follows:

GEH Notification Letter 2011-01, Impact of CORCL Bundle Power Correction - Part-length Rods (Reference 1):

An option in the CORCL code distributes power in a manner considering part-length rods in the bundle. This modeling technique has been found to be non-conservative in that it slightly under predicts the total power generated in the hot bundle. As such, the PCT results in calculations using this option would be non-conservative.

This error impacted the NMP1 GElI fuel with a PCT effect of +60'F.

GEH Notification Letter 2011-03, Impact of Updated Formulation for Gamma Heat Deposition to Channel Wall for 9x9 and 1 Ox] 0 Fuel Bundles (Reference 2):

In the input formulation for the SAFER model, input coefficients are used to direct the deposition of gamma and neutron radiation energy produced by fuel fissions and decay heat, determining whether it would heat the fuel rod, cladding, channel, or control rod structural materials. The contribution of heat from gamma ray absorption by the channel was found to have been minimized. The method had been simplified such that initially all the energy was assumed to be deposited in the fuel rods prior to the Loss-of-Coolant-Accident (LOCA) and then adjusted such that the correct heat deposition was applied after the scram. This modeling was determined to be potentially non-conservative, as not accounting for this small fraction of total power generation outside the fuel rod would tend to suppress the hot bundle power required to meet the initial operating Planar Linear Heat Generation Rate (PLHGR). Also, there is a small effect on the initial conditions for the balance of the core as these are set in relation to the hot bundle condition.

This error impacted the NMP1 GEl 1 fuel with a PCT effect of-25'F.

GEH Notification Letter 2011-04, Impact of Droplet Flow Distribution Arra Alignment to Rod Groupings Error (Reference 3):

Programmed enhancements to the CORCL code allowed for an increased number of rod groupings to be defined so as to more accurately represent bundle configuration in the ECCS-LOCA analysis. It was noted that an array in the model, which describes distribution of droplets and film cooling from core spray across the several groupings of rods and the channel, was not populated with corresponding additional elements. This had the effect of denying the channel and peripheral groupings of this core spray distribution, preferentially distributing liquid film and droplets with cooling effect to represented rod groupings. This condition is potentially non-conservative for calculating temperatures in those groupings where the PCT may occur.

This error impacted the NMP1 GEl 1 fuel with a PCT effect of-30'F.

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ATTACHMENT 10 CFR 50.46 ECCS EVALUATION MODEL - ERRORS AND MODEL CHANGE GEHNotification Letter 2011-05, Impact of Update in CORCL Code Version (Reference 4):

The CORCL code has been updated to Version CORCL07E3. The update provided added functionality of the code with respect to power distribution, increased the number of rod groups that can be modeled, included PRIME-based properties on fuel, corrected film cooling that was credited and provided other updates by way of code maintenance.

This model change impacted the NMP1 GEl 1 fuel with a PCT effect of+35'F.

The combined impact of the errors and the model change described above is a +40'F increase in the calculated NMP1 fuel PCT from 2150'F to 2190'F (i.e., below the 10 CFR 50.46 acceptance criterion of 2200-F).

In anticipation of the GEH Notifications, the NMP1 evaluation model was corrected prior to the startup from the Spring 2011 refueling outage to resolve the identified errors and address the model change. The NMP1 Maximum Average Planar Linear Heat Generation Rate (MAPLHGR) limits were adjusted through a plant monitoring system (i.e., 3D Monicore) update to maintain the desired PCT margin of 50'F. The updated MAPLHGR limits have also been included in the NMP1 Core Operating Limits Report (COLR) for the current operating cycle (Cycle 20) which commenced following the 2011 outage.

As such, NMP1 is in full compliance with 10 CFR50.46 PCT requirements. Note that although Global Nuclear Fuel (GNF2) fuel was installed during the refueling outage, NMP1 did not operate with GNF2 fuel prior to the MAPLGHR adjustments and model corrections being made.

The individual effect of each error and model change is also described in the attached Table, LOCA Margin Summary Sheet - 30 Day Report, Nine Mile Point Nuclear Station, Nine Mile Point Unit 1.

References

1) GE Hitachi Nuclear Energy 10 CFR 50.46 Notification Letter 2011-01 for Nine Mile Point Unit 1, "Impact of CORCL Bundle Power Correction - Part-length Rods," April 29, 2011

2) GE Hitachi Nuclear Energy 10 CFR 50.46 Notification Letter 2011-03 for Nine Mile Point Unit 1, "Impact of Updated Formulation for Gamma Heat Deposition to Channel Wall for 9x9 and l0x10 Fuel Bundles," April 29, 2011

3) GE Hitachi Nuclear Energy 10 CFR 50.46 Notification Letter 2011-04 for Nine Mile Point Unit 1, "Impact of Droplet Flow Distribution Array Alignment to Rod Groupings Error," April 29, 2011

4) GE Hitachi Nuclear Energy 10 CFR 50.46 Notification Letter 2011-05 for Nine Mile Point Unit 1, "Impact of Update in CORCL Code Version," April 29, 2011 2 of 3

ATTACHMENT 10 CFR 50.46 ECCS EVALUATION MODEL - ERRORS AND MODEL CHANGE Table LOCA Margin Summary Sheet - 30 Day Report Nine Mile Point Nuclear Station Nine Mile Point Unit 1 Evaluation Model: General Electric SAFER / GESTR - LOCA Methodology Net Absolute PCT Effect PCT Effect A. Prior 10 CFR 50.46 Changes or Error Corrections - APCT = 00F 00F Previous Years B. Prior 10 CFR 50.46 Changes or Error Corrections - APCT = OOF O0F This Year C. Current 10 CFR 50.46 Changes:

1. Notification 2011-01 (GEl 1) APCT = 60OF 60OF

2. Notification 2011-03 (GEl 1) APCT = -25OF 250F

3. Notification 2011-04 (GE 11) APCT = -30OF 30°F

4. Notification 2011-05 (GEl 1) APCT = 35 0F 35OF 150 F Absolute Sum of 10 CFR 50.46 Changes APCT =

The sum of the PCT from the most recent analysis using an acceptable evaluation model and the estimates of PCT impact for changes and errors identified since this analysis is less than 22000 F.

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