L-MT-11-076, 2011 Report of Changes and Errors in ECCS Evaluation Models

2011 Report of Changes and Errors in ECCS Evaluation Models

ML113570179
Person / Time
Site:	Monticello
Issue date:	12/22/2011
From:	O'Connor T Northern States Power Co, Xcel Energy
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-MT-11-076
Download: ML113570179 (5)

Text

Xcel EnergyB Monticello Nuclear Generating Plant 2807 W County Road 75 Monticello, MN 55362 December 22,201 1 L-MT-11-076 10 CFR 50.46(a)(3)

U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Monticello Nuclear Generating Plant Docket 50-263 Renewed Facility Operating License No. DPR-22 201 1 Report of Changes and Errors in ECCS Evaluation Models

References:

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

2) GE Report, GE-NE-J1I03878-09-02P, "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.

4) GEH 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, 201 1.

5) GEH 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, 201 1.

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

(L-MT-11-039), dated July 7, 201 1.

Pursuant to 10 CFR 50.46(a)(3), the Northern States Power Company, a Minnesota corporation (NSPM), d/b/a Xcel Energy, is providing the annual report of changes or errors identified in the Emergency Core Cooling System (ECCS) evaluation models or application for the Monticello Nuclear Generating Plant (MNGP). This report is for the period between July 201 0 and July 201 1.

The MNGP Loss of Coolant Accident (LOCA) analyses of record are contained in General Electric (GE) reports submitted for the MNGP rerate (Reference I ) and the LOCA analysis for the GE14 fuel type (Reference 2). The current operating cycle (Monticello Cycle 26) core loading consists of only the GE14 fuel design type.

Document Control Desk L-MT-11-076 Page 2 of 2 During this reporting period two new errors or changes (References 4 and 5) were identified resulting in a net 80°F change in Peak Clad Temperature (PCT) since the last Analysis of Record (AOR). The sum of the absolute values of the PCT changes was 110°F since the last AOR. This change in PCT constitutes a significant error (greater than 50°F) as defined in 10 CFR 50.46(a)(3)(i). A 30-day report (Reference 6) submitted on July 7, 201 1, demonstrates that the facility remains in compliance with 10 CFR 50.46 requirements. provides an updated summary table of the applicable changes and errors in the LOCA analyses from when the last analyses of record were performed. The licensing basis PCT and the PCT Summary provided in Table 1 of Enclosure 1 were revised to reflect these changes. This table is identical to the one provided within the 30-day report. A new AOR directly accounting for these errors will result when the Extended Power Uprate license amendment is approved. The adjusted licensing basis PCT for the fuel type used at MNGP during the reporting period are:

Fuel Type Licensing Basis PCT (OF)

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

Summaw of Commitments This letter proposes nbp/ew commitments and does not revise any existing O'Connor 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 I MONTICELLO NUCLEAR GENERATING PLANT TABLE I-

SUMMARY

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

L-MT-I 1-076 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-J1103878-09-02P, Monticello ECCS-LOCA 2 < I 960 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 analyses. 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-I1-076 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 during the current reporting period. 65 Sum of absolute value of changes since last AOR. 110 Algebraic sum of changes during the current reporting period. +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, "lmpact of SAFER LevelNolume Table Error on the Peak Clad Temperature (PCT)," dated May 6, 2003.

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

5. 10 CFR 50.46 Notification Letter 201 1-02, "lmpact of database error for heat deposition on the Peak Cladding Temperature (PCT) for 10x10 fuel bundles," dated June 10,2011.

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