L-MT-11-039, Submittal of 10 CFR 50.46 Thirty Day Report

Submittal of 10 CFR 50.46 Thirty Day Report

ML111890240
Person / Time
Site:	Monticello
Issue date:	07/07/2011
From:	O'Connor T Northern States Power Co, Xcel Energy
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
L-MT-11-039
Download: ML111890240 (5)

Text

@ Xcel Energy* Monticello Nuclear Generating Plant 2807 W County Road 75 Monticello, MN 55362 July 7, 201 1 L-MT-11-039 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 10 CFR 50.46 Thirty Day Report

References:

1) GE Report, NEDC-32514P, Revision 1, "Monticello SAFERIGESTR LOCA Loss of Coolant Accident Analysis," dated October 1997.

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

3) NSPM to NRC letter, "2010 Report of Changes and Errors in ECCS Evaluation Models," (L-MT-10-075), dated December 20, 2010 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 this 30-day report of changes or errors identified in the Emergency Core Cooling System (ECCS) evaluation models or their application for the Monticello Nuclear Generating Plant (MNGP). The most recent 10 CFR 50.46 report MNGP has provided was in 2010 (Reference 3). This 30-day report is being made due to several recent General Electric (GE) IHitachi Nuclear Energy 10 CFR 50.46 notifications received that have resulted in a cumulative increase in Peak Cladding Temperature (PCT) exceeding 50°F.

The MNGP Loss of Coolant Accident (LOCA) analyses of record are contained in GE reports submitted for the MNGP rerate (Reference 1) and the LOCA analysis for the GE14 fuel type (Reference 2), adjusted for the estimated effect of errors subsequently discovered in the evaluation models or their application. The LOCA analyses for the Extended Power Uprate have not received approval via issuance of a license amendment, are therefore not part of the current licensing basis, and hence are not discussed herein.

The combined impact on PCT of the errors 1 changes described above is 65°F for the GE14 fuel, comprising the MNGP core. An evaluation to show compliance with 10 CFR 50.46 requirements is provided per 10 CFR 50.46(a)(3)(ii) as follows:

Document Control Desk L-MT-11-039 Page 2 of 2 Considering all estimated effects of errors and changes, the adjusted PCT is 2040°F.

This is 160°F below the 2200°F acceptance criterion of 10 CFR 50.46(b)(I). This is sufficient margin to justify taking no further action. No further reanalysis or other actions are planned. provides additional information on the nature of the errors, and their effect on the limiting ECCS analysis. This information is submitted in accordance with the requirements of 10 CFR 50.46(a)(3)(ii) for the MNGP because the PCT increase is greater than 50°F and qualifies as a significant change according to 10 CFR 50.46(a)(3)(i).

If you have any questions or require additional information, please contact Mr. Richard Loeffler at (763) 295-1247.

Summary of Commitments commitments and does not revise any existing ident, Monticello Nuclear Generating Plant pany - Minnesota Enclosure cc: Regional Administrator, Region Ill, USNRC Project Manager, Monticello Nuclear Generating Plant, USNRC Resident Inspector, Monticello Nuclear Generating Plant, USNRC

ENCLOSURE I MONTICELLO NUCLEAR GENERATING PLANT TABLE I

SUMMARY

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

L-MT-11-039 Enclosure 1 Page 1 of 2 TABLE I -

SUMMARY

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

Licensing Applicable Analysis or Error Description Ref. Basis PCT("F)

GE14 NEDC-32514P, Rev 1, Monticello SAFERIGESTR-LOCA ----

1 Loss of Coolant Accident Analysis GE-NE-J1103878-09-02P1Monticello ECCS-LOCA 2 4960 Evaluation for GE14 lmpact of SAFER LevelNolume Table Error on 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.

lmpact 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 analysis. It was determined that a top-peaked axial power shape can result in higher calculated PCT.

lmpact of database error for heat deposition on the PCT for 10x10 fuel bundles (Notification Letter 201 1-02)

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

lmpact of updated formulation for gamma heat deposition to channel wall for 9x9 and 10x10 fuel bundles (Notification Letter 201 1-03)

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 the fuel rods prior to the LOCA and then adjusted 6 +5 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.

L-MT-11-039 Page 2 of 2 TABLE 1 -

SUMMARY

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

Sum of absolute value of changes since the last 10 CFR 50.46 report for 2010. 65 Sum of absolute value of changes since last AOR. 110 Algebraic sum of changes since the last 10 CFR 50.46 report for 2010. +65 Algebraic sum of changes since last AOR. +80 Current Adjusted Peak Cladding Temperature ~2040 References

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

2. GE-NE-J1103878-09-02P, "Monticello ECCS-LOCA Evaluation for GE14,"

dated August 2001.

3. 10 CFR 50.46 Notification Letter 2003-01, "Impact of SAFER LevelNolume 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 201 1-02, "Impact of database error for heat deposition on the Peak Cladding Temperature (PCT) for 10x10 fuel bundles," dated June 10,201I.

6. 10 CFR 50.46 Notification Letter 201 1-03, "Impact of updated formulation for gamma heat deposition to channel wall for 9x9 and 10x10 fuel bundles," dated June 10,2011.