L-MT-13-116, 2013 Annual Report of Changes and Errors in Emergency Core Cooling System Evaluation Models

2013 Annual Report of Changes and Errors in Emergency Core Cooling System Evaluation Models

ML13361A076
Person / Time
Site:	Monticello
Issue date:	12/27/2013
From:	Fili K Northern States Power Co, Xcel Energy
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-MT-13-116
Download: ML13361A076 (7)

Text

Xcel Energy Monticello Nuclear Generating Plant 2807 W County Road 75 Monticello, MN 55362 December 27, 2013 L-MT-13-116 10 CFR 50.46(a)(3)(ii)

U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Monticello Nuclear Generating Plant Docket 50-263 Renewed Facility Operating License No. DPR-22 2013 Annual Report of Changes and Errors in Emergency Core Cooling System Evaluation Models

References:

1) NSPM to NRC letter, "2012 Report of Changes and Errors in Emergency Core Cooling System Evaluation Models," (L-MT-12-099),

dated December 20, 2012

2) NRC to NSPM, "

Subject:

Monticello Nuclear Generating Plant-Issuance of Amendment No. 176 to Renewed Facility Operating License Regarding Extended Power Uprate (TAC No. MD9990)," dated December 9, 2013.

3) GE Report, NEDC-32514P, Revision 1, "Monticello SAFER/GESTR LOCA Loss of Coolant Accident Analysis," dated October 1997

4) GE Report, GE-NE-J1103878-09-02P, "Monticello ECCS-LOCA Evaluation for GE14," dated August 2001

5) GE Notification Letter 2012-01, Revision 1, "PRIME Fuel Properties Implementation for Fuel Rod T/M Performance, replacing GESTR Fuel Properties," dated July 30, 2013

6) NSPM to NRC letter, "August 2013, 10 CFR 50.46 Thirty-Day Report,"

(L-MT-13-090), dated August 27, 2013 Pursuant to 10 CFR 50.46(a)(3)(ii), the Northern States Power Company, a Minnesota corporation (NSPM), doing business as Xcel Energy, is providing the annual report of changes or errors identified in the Emergency Core Cooling System (ECCS) evaluation model for the Monticello Nuclear Generating Plant (MNGP). This report is for the period since the last annual update (Reference 1), i.e., between July 2012 and July 2013.

Document Control Desk L-MT-13-116 Page 2 of 3 An Extended Power Uprate (EPU) amendment (Amendment 176) was issued December 9, 2013 (Reference 2), but the changes related to this amendment are not included herein because they did not occur during the reporting period. A separate 10 CFR 50.46 report discussing changes and errors in EPU ECCS evaluation models is under development and is to be submitted to re-baseline this annual report with the adoption of EPU.

The MNGP Loss of Coolant Accident (LOCA) analyses of record (AORs), for the reporting period, are contained in General Electric (GE) reports performed for the MNGP rerate to the previous licensed thermal power (1775 MWt) (Reference 3) and the LOCA analysis for the GE14 fuel type comprising the MNGP core (Reference 4). These analyses were adjusted for the estimated effect of errors or changes subsequently discovered in the evaluation models or in their application.

During this reporting period, a notification of an error or change resulting in a change to the Peak Cladding Temperature (PCT) was received from General Electric Hitachi (GEH) Nuclear Energy. GEH Notification Letter 2012-01, Revision1 (Reference 5),

reflects a reduction in the change in PCT from 45°F to 10°F, when applying the PRIME fuel properties model for fuel rod thermal I mechanical (T I M) performance, which replaced the GESTR fuel properties model. This resulted in an Adjusted PCT of 2050°F. The modeling change still, however, resulted in a cumulative increase in PCT exceeding the 50°F threshold specified in 10 CFR 50.46, and was reported in a 30-day report on August 27, 2013 (Reference 6).

As prescribed by 10 CFR 50.46, a proposed reanalysis schedule or an evaluation is required to demonstrate the facility remains in compliance with the requirements of the regulation when the cumulative increase in PCT threshold is exceeded. With the adoption of the EPU amendment this reanalysis has been completed. No further reanalysis or other actions are planned.

The enclosure provides additional information on the nature of the change, and the previous changes and errors, and their effect on the prior MNGP LOCA analysis. This information is being submitted in accordance with the requirements of 10 CFR 50.46(a)(3)(ii) for the MNGP.

Document Control Desk L-MT-13-116 Page 3 of 3 If you have any questions or require additional information, please contact Mr. Richard Loeffler at (763) 295-1247.

Summary of Commitments This letter proposes no new commitments and does not revise any existing commitments.

Karen D. Fili, Site Vice-President, Monticello Nuclear Generating Plant Northern States Power Company- Minnesota Enclosure cc: Regional Administrator, Region Ill, USNRC Project Manager, Monticello Nuclear Generating Plant, USNRC Resident Inspector, Monticello Nuclear Generating Plant, USNRC

ENCLOSURE MONTICELLO NUCLEAR GENERATING PLANT TABLE 1 -

SUMMARY

OF MONTICELLO LOCA CHANGES AND ERRORS INVOLVING CHANGES IN PEAK CLADDING TEMPERATURE (PCT)

(3 Pages Follow)

L-MT-13-116 Enclosure Page 1 of 3 Table 1 -Summary of Monticello LOCA Changes and Errors Involving Changes in Peak Cladding Temperature Licensing Applicable Analysis or Error Description Ref. Basis PCT(°F)

GE14 NEDC-32514P, Revision 1, Monticello SAFER/GESTR-LOCA 1 ----

Loss of Coolant Accident Analysis GE-NE-J1103878-09-02P, Monticello ECCS-LOCA 2 < 1960 Evaluation for GE 14 Impact of SAFER LeveiNolume Table Error on [Peak Cladding Temperature] PCT (Notification Letter 2003-01) 3 - 15 Level and volume tables used by SAFER were not updated when a revised initial water level was implemented.

Impact of Top Peaked Power Shape for Small Break LOCA Analysis (Notification Letter 2006-01)

Small Break LOCA analyses had assumed a mid-peaked axial 4 + 30 power shape consistent with the DBA break analyses. It was determined that a top-peaked axial power shape can result in higher calculated PCT.

Impact of database error for heat deposition on the Peak Cladding Temperature (PCT) for 10x10 fuel bundles (Notification Letter 2011-02)

The input coefficients used to direct the deposition of gamma 5 + 60 radiation energy produced by the fuel caused the heat deposited in the fuel channel (post scram) to be over-predicted and the corresponding heat in the fuel to be under-predicted.

(continued)

L-MT-1 3-116 Enclosure Page 2 of 3 Licensing Basis Applicable Analysis or Error Description Ref.

PCT(°F)

GE14 Impact of updated formulation for gamma heat deposition to channel wall for 9x9 and 1Ox1 0 fuel bundles (Notification Letter 2011-03)

In the input formulation for SAFER, the method for the contribution of heat from gamma ray absorption by the channel had been simplified so that initially all energy was deposited in 6 +5 the fuel rods prior to the LOCA and then adjusted to the correct heat deposition after the scram. Not accounting for this small fraction of power generation outside the fuel rod tends to suppress the hot bundle power required to meet the initial operating Peak LHGR. Also, there is a small effect on the initial conditions for the rest of the core as these are set in relation to the hot bundle condition.

PRIME Fuel Properties Implementation for Fuel Rod T/M Performance, replacing GESTR Fuel Properties (Notification Letter 2012-01, Revision 1)

This change is due to the application of an NRC-approved 7 + 10 procedure to estimate the change in PCT due to the change in fuel properties from GESTR to PRIME primarily to address inaccuracies in fuel pellet thermal conductivity as a function of exposure.

Sum of absolute value of changes during the current reporting period. 10 Sum of absolute value of changes since last AOR. 120 Algebraic sum of changes during the current reporting period. + 10 Algebraic sum of changes since last A OR. + 90 Current Adjusted Peak Cladding Temperature < 2050

L-MT-13-116 Enclosure Page 3 of 3 References

1. GE Report: NEDC-32514P, Revision 1, "Monticello SAFER/GESTR-LOCA Loss-of-Coolant Accident Analysis," dated October 1997.

2. GE-NE-J11 03878-09-02P, "Monticello ECCS-LOCA Evaluation for GE14,"

dated August 2001.

3. 10 CFR 50.46 Notification Letter 2003-01, "Impact of SAFER LeveiNolume Table Error on the Peak Cladding Temperature (PCT)," dated May 6, 2003.

4. 10 CFR 50.46 Notification Letter 2006-01, "Impact of Top Peaked Power Shape for Small Break LOCA Analysis," dated July 28, 2006.

5. 10 CFR 50.46 Notification Letter 2011-02, "Impact of database error for heat deposition on the Peak Cladding Temperature (PCT) for 1Ox1 0 fuel bundles," dated June10,2011.

6. 10 CFR 50.46 Notification Letter 2011-03, "Impact of updated formulation for gamma heat deposition to channel wall for 9x9 and 1Ox1 0 fuel bundles," dated June 10, 2011.

7. 10 CFR 50.46 Notification Letter 2012-01, Revision 1, "PRIME Fuel Properties Implementation for Fuel Rod TIM Performance, replacing GESTR Fuel Properties,"

dated July 30, 2013.