L-MT-16-071, Submittal of 2016 Annual Report of Changes in Emergency Core Cooling System Evaluation Models Pursuant to 10 CFR 50.46

Submittal of 2016 Annual Report of Changes in Emergency Core Cooling System Evaluation Models Pursuant to 10 CFR 50.46

ML16355A117
Person / Time
Site:	Monticello
Issue date:	12/19/2016
From:	Gardner P Northern States Power Company, Minnesota, Xcel Energy
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-MT-16-071, TAC MD9990, TAC ME3145
Download: ML16355A117 (11)

Text

2807 West County Road 75 Monticello, MN 55362 Xcel Energy R ESP 0 N S I B l E BY NAT U R E 800.895.4999 xcelenergy.com December 19, 2016 L-MT-16-071 10 CFR 50.46(a)(3)(ii)

ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 Monticello Nuclear Generating Plant Docket No. 50-263 Renewed Facility Operating License No. DPR-22 2016 Annual Report of Changes in Emergency Core Cooling System Evaluation Models Pursuant to 10 CFR 50.46

References:

1) NSPM (T. O'Connor) to NRC, "License Amendment Request: Extended Power Uprate (TAC MD9990)," L-MT-08-052, dated November 5, 2008 2) NSPM (M. Schimmel) to NRC, "Monticello Extended Power Uprate and Maximum Extended Load Line Limit Analysis Plus License Amendment Requests:

Supplement for Analytical Methods Used to Address Thermal Conductivity Degradation and Analytical Methods Limitations (TAC Nos. MD9990 and ME3145)," L-MT-13-053, dated July 8, 2013 3) NSPM (P. Gardner) to NRC, "2015 Annual Report of Changes in Emergency Core Cooling System Evaluation Models Pursuant to 1 0 CFR 50.46," L-MT-15-091, dated December 22, 2015 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 annual report concerning changes or errors identified in the Emergency Core Cooling System (ECCS) evaluation models for the Monticello Nuclear Generating Plant (MNGP). The MNGP Loss of Coolant Accident (LOCA) analyses of record (AOR) are contained in the General Electric-Hitachi (GEH) reports submitted for the MNGP Extended Power Uprate and the Maximum Extended Load Line Limit Analysis Plus (MELLLA+)

license amendments (References 1 and 2). Provided within Enclosure 1 is a report.concerning any changes or errors identified in the GEH ..... ECCS evaluation models for the MNGP. This report is for the period between July 2015 and July 2016 for the GEH fuel. The core for the current operating cycle (Cycle 28) consists solely of the GE14 fuel type. During this period no notifications of any changes or errors resulting in a change to the calculated Peak Clad Temperature (PCT) were received from GEH.

L-MT-16-071 Page 2 of 2 Therefore, the licensing basis PCT of less than 2170oF for the GE14 fuel and the PCT summary provided in the 2015 annual report is unchanged (Reference 3). The 2017 Refueling Outage (RFO), scheduled for early 2017, will be the first loading of the AREVA ATRIUM 10XM fuel type into the MNGP core (Cycle 29).(1) Pursuant to 10 CFR 50.46(a)(3)(ii), NSPM is providing within Enclosure 2 a report concerning any changes or errors identified in the AREVA ECCS evaluation models for MNGP for the period between July 2015 and July 2016. During this reporting period, AREVA provided two notification letters involving a total of nine specific changes or errors, resulting in a minus 5°F change, and an adjusted licensing basis PCT of less than 2083°F for the ATRIUM 10XM fuel type. Summary of Commitments This letter makes no new commitments and no revisions to existing commitments.

7 @/ 1 Peter A. Gardner Site Vice President, Monticello Nuclear Generating Plant Northern States Power Company-Minnesota

Enclosures:

(2) cc: Administrator, Region Ill, USNRC Project Manager, Monticello, USNRC Resident Inspector, Monticello, USNRC 1. Until all the GE14 fuel is permanently discharged from the MNGP core, annual reports will continue to be provided for the associated GEH evaluation models, pursuant to 10 CFR 50.46. While both GE14 and ATRIUM 10XM fuel are in the core, NSPM intends to provide an annual report to include both the GEH and AREVA changes.

ENCLOSURE 1 MONTICELLO NUCLEAR GENERATING PLANT TABLE 1 -

SUMMARY

OF MONTICELLO LOCA CHANGES AND ERRORS INVOLVING CHANGES IN PEAK CLADDING TEMPERATURE (PCT) FOR GE14 FUEL L-MT-16-071 Enclosure 1 Page 1 of 3 TABLE 1 -

SUMMARY

OF MONTICELLO LOCA CHANGES AND ERRORS INVOLVING CHANGES IN PEAK CLADDING TEMPERATURE (PCT) FOR GE14 FUEL Licensing Applicable Analysis or Error/Change Description Ref. Basis PCT(°F) GE14 NEDC-33322P, Revision 3, Safety Analysis Report for Monticello G1& <2140 Constant Pressure Power Uprate G2 PRIME Fuel Properties Implementation for Fuel Rod T/M Performance, replacing GESTR Fuel Properties (1 0 CFR 50.46 Notification Letter 2012-01, Revision 1) This change is due to the application of an NRC-approved G3 +10 procedure to estimate the change in Peak Clad Temperature (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.

SAFER04A E4-Maintenance Update Changes (1 0 CFR 50.46 Notification Letter 2014-01) This change is for a new version (E4) of SAFER04A that G4 +0 resolves several accumulated observations that are code maintenance items. Sensitivity calculations show these items have an insignificant effect on calculated PCT. SAFER04A E4-Mass Non-Conservatism (1 0 CFR 50.46 Notification Letter 2014-02) This change is due to a logic error that occurs when upper G5 +15 plenum liquid mass and core spray flow rate are low. System mass is gradually lost due to core spray being discarded, resulting in marginally less ECCS flow credited as reaching the core. SAFER04A E4-Minimum Core DP Model (1 0 CFR 50.46 Notification Letter 2014-03) This change is due to the use of a minimum Lip that could be G6 +20 offering inappropriate steam cooling benefit above the core two-phase level.

• .-** ,, L-MT-16-071 Enclosure 1 Page 2 of 3 TABLE 1 -

SUMMARY

OF MONTICELLO LOCA CHANGES AND ERRORS INVOLVING CHANGES IN PEAK CLADDING TEMPERATURE (PCT) FOR GE14 FUEL Licensing Applicable Analysis or Error/Change Description Ref. Basis PCT(°F) GE14 SAFER04A E4-Bundle/Lower Plenum CCFL Head (1 0 CFR 50.46 Notification Letter 2014-04) This change is due to the counter current flow limitation (CCFL) G7 -15 calculation representing the pressure head slightly different from that of the calculated water level in the bundle. Sum of absolute value of changes for the current reporting period, which 0 includes all changes since the 10 CFR 50.46 report. Sum of absolute value of changes since last A OR. 60 Algebraic sum of changes for the current reporting period, which includes +0 all changes since the 10 CFR 50.46 report. Algebraic sum of changes since last A OR. +30 Current Adjusted Peak Cladding Temperature

<2170 References G1. GE Report: NEDC-33322P Revision 3, "Safety Analysis Report for Monticello Constant Pressure Power Uprate," dated October 2008 (Enclosure 5 of NSPM (T. O'Connor) to NRC, "License Amendment Request: Extended Power Uprate (TAG MD9990)," L-MT-08-052, dated November 5, 2008) G2. NSPM (M. Schimmel) to NRC, "Monticello Extended Power Uprate and Maximum Extended Load Line Limit Analysis Plus License Amendment Requests:

G3. Supplement for Analytical Methods Used to Address Thermal Conductivity Degradation and Analytical Methods Limitations (TAG Nos. MD9990 and ME3145)," L-MT-13-053, dated July 8, 2013 GEH 10 CFR50.46 Notification Letter 2012-01, Revision 1, "PRIME Fuel Properties Implementation for Fuel Rod T/M replacing GESTR Fuel Properties," dated July 30, 2013 G4. GEH 10 CFR 50.46 Notification Letter 2014-01, "SAFER04A E4-Maintenance Update Changes," dated May 21, 2014 L-MT-16-071 Enclosure 1 Page 3 of 3 TABLE 1 -

SUMMARY

OF MONTICELLO LOCA CHANGES AND ERRORS INVOLVING CHANGES IN PEAK CLADDING TEMPERATURE (PCT) FOR GE14 FUEL References G5. GEH 10 CFR 50.46 Notification Letter 2014-02, "SAFER04A E4-Mass Non-Conservatism," dated May 21, 2014. G6. GEH 10 CFR 50.46 Notification Letter 2014-03, "SAFER04A E4-Minimum Core DP Model," dated May 21, 2014. G7. GEH 10 CFR 50.46 Notification Letter 2014-04, "SAFER04A E4-Bundle/Lower Plenum CCFL Head," dated May 21, 2014.

ENCLOSURE 2 MONTICELLO NUCLEAR GENERATING PLANT TABLE 2-

SUMMARY

OF MONTICELLO LOCA CHANGES AND ERRORS INVOLVING CHANGES IN PEAK CLADDING TEMPERATURE (PCT) FOR ATRIUM 10XM FUEL L-MT-16-071 Enclosure 2 Page 1 of 4 TABLE 1 -

SUMMARY

OF MONTICELLO LOCA CHANGES AND ERRORS INVOLVING CHANGES IN PEAK CLADDING TEMPERATURE (PCT) FOR AREVA 1 OXM FUEL Licensing Applicable Analysis or Error/Change Description Ref. Basis PCT(°F) 10XM ANP-3212(P)

Revision 0, Monticello EPU LOCA-ECCS Analysis A1 <2088 MAPLHGR Limits for ATRIUMŽ 10XM Fuel Implementation of ACE in RELAX. The approved interpolation scheme required by Licensing A2 +0 Topical Report (L TR) EMF-2361 (Section 3.2.2) was not employed when the ACE Critical Heat Flux (CHF) correlations were implemented in RELAX. Modified Analysis Approach (1). Extraneous messages written in RELAX minor edits can impact A2 +0 the modified analysis approach.

This error did not impact the limiting PCT. Modified Analysis Approach (2). The performance of a specific action under the modified analysis A2 +0 approach is overly conservative.

This error did not impact the limiting PCT. Modified Analysis Approach (3). The time when a specific action under the modified analysis A2 +0 approach began might be incorrectly reported in the documentation of the calculation.

The error did not impact the time used in any of the MNGP LOCA calculations.

L-MT-16-071 Enclosure 2 Page 2 of 4 TABLE 1 -

SUMMARY

OF MONTICELLO LOCA CHANGES AND ERRORS INVOLVING CHANGES IN PEAK CLADDING TEMPERATURE (PCT) FOR AREVA 1 OXM FUEL Licensing Applicable Analysis or Error/Change Description Ref. Basis PCT(°F) 10XM Low Pressure Coolant Injection (LPCI) Loop Selection Logic. Relates to an input error when modeling breaks smaller than 0.4 ft2. MNGP has instrumentation and logic to detect which recirculation line contains a break. When a break is detected, the logic injects all LPCI flow into the recirculation line that does not contain the break and closes the discharge isolation valve in that same recirculation line. If a break is not detected, the LPCI A2 +0 flow is injected and the discharge isolation valve is closed in a predefined recirculation line. LOCA analyses for breaks smaller than 0.4 ft2 conservatively assumed the break was in the recirculation line that was predefined to receive the LPCI flow and should have closed the discharge isolation valve in the same recirculation line. Instead, the discharge isolation valve was modeled as closing in the intact recirculation line. End of Slowdown.

A modeling assumption was made that could result in an error in the time when rated Low Pressure Core Spray (LPCS) is reached. The time when rated LPCS flow is reached is used in two parts of the LOCA calculation and it relates to the use of the A2 -5 modified analysis approach.

This error did cause a small change in the time when the heat transfer coefficients in the heatup calculation change from the calculated values to the values specified in 10 CFR 50 Appendix K. Modeling Assumption for Time of Bypass Reflood. A modeling assumption could result in an error in the time of A2 +0 bypass reflood. The time of bypass reflood is the time the heat transfer coefficient beneath the bypass mixture level is set to 25 Btu/hr-ft2 -°F.

L-MT-16-071 Enclosure 2 Page 3 of 4 TABLE 1-

SUMMARY

OF MONTICELLO LOCA CHANGES AND ERRORS INVOLVING CHANGES IN PEAK CLADDING TEMPERATURE (PCT) FOR AREVA 10XM FUEL Licensing Applicable Analysis or Error/Change Description Ref. Basis PCT(°F) 10XM Using End-of-Slowdown (EOB) Time for Selecting HUXY Boundary Conditions.

At the EOB (which is the time of rated core spray), the hottest axial slab in the RELAX hot channel calculation is identified.

This establishes the boundary conditions that are passed into the A2 +0 HUXY calculation.

While this is appropriate under some conditions when the slabs continue to heat up after EOB, it may not be appropriate for other conditions when the EOB time is much later and the nodes have cooled down. Pressure Permissive for Closing Recirculation Discharge Isolation Valve (RDIV) during Single Loop Operation (SLO). Monticello has two recirculation lines. Each line has a location for injecting LPCI flow and a RDIV on the discharge side of the recirculation pump. Monticello also has Loop Selection Logic which will route all of the LPCI flow to the unbroken loop and close the RDIV in the same loop. During SLO the pressure must be less than or equal to 900 psig A3 +0 before the RDIV will begin to close. This pressure permissive during SLO was not modeled in the SLO LOCA calculations.

Evaluations were performed that indicate modeling the pressure permissive would not impact the limiting SLO break. This issue does not impact a LOCA initiated during Two-Loop Operation (TLO) because the RDIV pressure permissive is modeled correctly.

Therefore, this issue has zero impact on the limiting PCT. Sum of absolute value of changes for the current reporting period, which +0 includes all changes since the 10 CFR 50.46 report. Sum of absolute value of changes since last AOR. 5 Algebraic sum of changes for the current reporting period, which includes +0 all changes since the 10 CFR 50.46 report. Algebraic sum of changes since last AOR. -5 Current Adjusted Peak Cladding Temperature

<2083 L-MT-16-071 Enclosure 2 Page 4 of 4 TABLE 1 -

SUMMARY

OF MONTICELLO LOCA CHANGES AND ERRORS INVOLVING CHANGES IN PEAK CLADDING TEMPERATURE (PCT) FOR AREVA 1 OXM FUEL References A1. AREVA Report ANP-3212(P)

Revision 0, "Monticello EPU LOCA-ECCS Analysis MAPLHGR Limits for ATRIUMŽ 10XM Fuel," AREVA NP, May 2013 (Enclosure 20 of NSPM letter to NRC, "License Amendment Request for Transition to AREVA ATRIUM 10XM Fuel and AREVA Safety Analysis Methodology," L-MT-13-055, dated July 15, 2013 A2. AREVA Report FS1-0026440 Revision 1, "Monticello 10 CFR 50.46 PCT Reporting Estimates for ATRIUM 10XM Fuel," approved May 13, 2016 A3. AREVA Report FS1-0029081 Revision 1, "Monticello 10 CFR 50.46 PCT Reporting Estimates for ATRIUM 10XM Fuel-Through July 2016," approved October 12, 2016