ML15078A332

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NRC Staff Evaluation of Core Operating Limits Report for Cycle 15
ML15078A332
Person / Time
Site: LaSalle Constellation icon.png
Issue date: 03/26/2015
From: Blake Purnell
Plant Licensing Branch III
To: Bryan Hanson
Exelon Generation Co, Exelon Nuclear
Blake Purnell, NRR/DORL
References
TAC MF2396
Download: ML15078A332 (9)
v • d • e


Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 March 26, 2015 Mr. Bryan C. Hanson Senior Vice President Exelon Generation Company, LLC President and Chief Nuclear Officer (CNO)

Exelon Nuclear 4300 Winfield Road Warrenville, IL 60555

SUBJECT:

LASALLE COUNTY STATION, UNIT 2 - THE U.S. NUCLEAR REGULATORY COMMISSION STAFF EVALUATION OF CORE OPERATING LIMITS REPORT FOR CYCLE 15 (TAC NO. MF2396)

Dear Mr. Hanson:

By letters dated March 6 and August 28, 2013 (Agencywide Documents Access and Management System (ADAMS) Accession Nos. ML13072A228 and ML13262A292, respectively), Exelon Generation Company, LLC (the licensee) submitted the core operating limits report (COLR), Revisions 0 and 1 for Cycle 15 at LaSalle County Station, Unit 2. By letter dated September 30, 2013 (ADAMS Accession No. ML13193A043), the U.S. Nuclear Regulatory Commission (NRC) staff issued a request for additional information regarding these submittals. The licensee responded to this request by letter dated October 31, 2013 (ADAMS Accession No. ML13308B026).

The NRC staff has completed its review of the COLR and supplemental information. Enclosed is a copy of the staff's evaluation.

Should you have any questions, please contact me at 301-415-1380 or by email at blake.purnell@nrc.gov.

Sincerely, Blake Purnell, Project Manager Plant Licensing 111-2 and Planning and Analysis Branch Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-37 4

Enclosure:

Staff Evaluation cc w/encl: Distribution via Listserv

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 STAFF EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION CORE OPERATING LIMITS REPORT, CYCLE 15 EXELON GERNATION COMPANY, LLC LASALLE COUNTY STATION, UNIT 2 DOCKET NO. 50-374

1.0 INTRODUCTION

On February 27, 2013 (Agencywide Documents Access and Management System (ADAMS)

Accession No. ML13050A637; Reference 9), the U.S. Nuclear Regulatory Commission (NRC) staff issued Amendment No. 192 to Facility Operating License No. NPF-18 for the LaSalle County Station, Unit 2 (LSCS2). This amendment changed the safety limit minimum critical power ratio (SLMCPR) in technical specification (TS) 2.1.2 to support the LSCS2 transition to Global Nuclear Fuel (GNF) GNF2 fuel from the resident AREVA ATRIUM-10 fuel starting in Cycle 15. The LSCS2, Cycle 15, core had 764 fuel assemblies, which consisted of 304 fresh GNF2 bundles, 312 once burned ATRIUM-10 bundles, and 148 twice burned ATRIUM-10 bundles.

The SLMCPR changed from 1.11 to 1.14 for two recirculation-loop operation (TLO) and from 1.12 to 1.17 for single-loop operation (SLO). These SLMCPR values are for the reactor steam dome pressure greater than or equal to 785 pounds per square inch gauge and core flow greater than or equal to 1O percent of rated core flow.

By letters dated March 6 and August 28, 2013 (ADAMS Accession Nos. ML13072A228 and ML13262A292, respectively}, Exelon Generation Company, LLC (the licensee) submitted the core operating limits report (COLA), Revisions 0 and 1 for LSCS2, Cycle 15. By letter dated September 30, 2013 (ADAMS Accession No. ML13193A043}, the NRC staff issued a request for additional information regarding these submittals. The licensee responded to this request by letter dated October 31, 2013 (ADAMS Accession No. ML13308B026).

This NRC staff evaluation reviewed (1) the licensee's analyses supporting the COLR, (2) the licensee's assessment of the transition to GNF2 fuel, and (3) other mixed core compatibility analyses related to the fuel transition.

Enclosure

2.0 REGULATORY EVALUATION

Paragraph (c)(1) of Title 10 of the Code of Federal Regulations (10 CFR) Section 50.36, "Technical Specifications," requires that power reactor facility TS includes safety limits for process variables that protect the integrity of certain physical barriers that guard against the uncontrolled release of radioactivity. The fuel cladding is one of the physical barriers that separate the radioactive materials from the environment. The purpose of the SLMCPR is to ensure that specified acceptable fuel design limits (SAFDLs) are not exceeded during steady state operation and analyzed transients.

General Design Criterion 10 (GDC 10), "Reactor Design," of Appendix A to 10 CFR Part 50 states that the reactor core and associated coolant, control, and protection systems shall be designed with appropriate margin to assure that SAFDLs are not exceeded.

Guidance on the acceptability of the reactivity control systems, the reactor core, and fuel system design is provided in NUREG-0800, "Standard Review Plan [SRP] for the Review of Safety Analysis Reports for Nuclear Power Plants." Specifically, SRP, Section 4.2, "Fuel System Design," specifies all fuel damage criteria for evaluation of whether fuel designs meet the SAFDLs. Section 4.4, "Thermal Hydraulic Design," provides guidance on the review of thermal-hydraulic design in meeting the requirement of GDC 10 and the fuel design criteria established in Section 4.2.

Section 50.59, "Changes, Tests, and Experiments," to 10 CFR establishes the conditions or process under which licensees may make changes to the facility or procedures and conduct tests or experiments without prior NRC approval.

3.0 TECHNICAL REVIEW

SUMMARY

3.1 COLR, Cycle 15, Revision 1 Power and flow dependent limits are listed for various power and flow levels in the COLR (Reference 1). Operation up to 105 percent rated flow is licensed for this cycle. Linear interpolation is used to find intermediate values for power and flow. The 100 percent rated power and core flow values can be used for thermal limit monitoring at higher power and core flow values, respectively, unless otherwise indicated in the applicable table. The results from safety analyses, such as fuel-thermal mechanical limits, core thermal hydraulics limits, emergency core cooling system (ECCS) limits, nuclear limits, and transient and accident analysis limits, are provided in the reload licensing documents (Reference 2).

The three exposure ranges defined in the COLR, Table 3-1, are beginning to middle of cycle, middle to end of cycle, and beginning to end of cycle. The COLR also defines the end of rated (EOR) exposure as the cycle exposure corresponding to all rods out, 100 percent power/100 percent flow, and normal feedwater temperature. The EOR exposure for LSCS2 is 33,310 Megawatt-days per metric ton (MWd/MT) (Reference 2).

The ECCS-loss-of-coolant accident (ECCS-LOCA) analyses for GNF2 and ATRIUM-10 fuel are based on the NRC-approved SAFER/PRIME-LOCA methodology. The ECCS-LOCA maximum

average planar linear heat generation rate (MAPLHGR) limits, including the SLO multiplier, for all fuel types are listed in Section 4 of the COLR.

Table 5-2 of the COLR lists the maximum values of operating limit minimum critical power ratio (OLMCPR) obtained from analysis of the pressurization events, non-pressurization events, and the Option Ill stability evaluation (Reference 2). Table 5-3 lists the power-dependent minimum critical power ratio (MCPR) multipliers (Kp) for the application group of equipment out-of-service.

Tables 5-4 and 5-5 list the flow dependant MCPR limit as a function of the core flow, based on the applicable plant conditions and determined from these tables the flow-dependent of OLMCPR.

Section 6 of the COLR provides information in the linear heat generation rate (LHGR). The LHGR limit is the product of the exposure dependent limit for the specific fuel types and the minimum power- or flow-dependent LHGR factor, as appropriate. The COLR shows that the maximum value for the flow-dependent LHGR multipliers for SLO is 0.78.

Appendix A to the COLR contains the fuel bundle information report for LSCS2, Cycle 15, reload. This appendix lists the U0 2/Gd (uranium oxide/gadolinium) thermal-mechanical LHGR limits for the GNF2 fuel that was loaded in Cycle 15.

The NRC staff reviewed the COLR and found that it contains thermal-mechanical limits calculated from reload-licensing analyses performed for Cycle 15 using NRC-approved methodologies.

3.2 Assessment of Fuel Transition The NRC staff reviewed the 10 CFR 50.59 process documents (References 3 and 4) regarding the fuel transition to GNF2 design. The 10 CFR 50.59 activity included the core loading configuration of fuel assemblies in the reactor and the associated fuel change package, reload safety and transient analysis, design analysis calculations, core models, procedure changes, and other changes necessary to implement and operate the Cycle 15 core for LSCS2.

The LSCS2, Cycle 15, reload core safety analyses and cycle-specific reload analyses were performed in accordance with the NRC-approved GNF licensing topical report NEDE-24011-P-A-19, "General Electric Standard Application for Reactor Fuel (GESTAR II)," and other NRC-approved methodologies identified in LSCS2 TS 5.6.5, "Core Operating Limits Report." These reload analyses covered all operating conditions identified in GNF report 0000-0156-1147-SRLR, Revision 1, "Supplemental Reload Licensing Report (SRLR) for LaSalle Unit 2 Reload 14 Cycle 15," dated January 2013.

According to the GNF2 compliance document (Reference 11 ), in addition to the generic aspects, the plant-specific application process is to confirm that the cycle-independent aspects of the GNF2 fuel introduction meet the design and licensing basis of the plant. The cycle independent analyses will be defined and evaluated consistent with the plant licensing basis.

Also, the GNF2 compliance document states that the new fuel introduction (NFI) report needs to document the cycle-independent, plant-specific analyses listed in Table 4-1 of Reference 11 for use by the licensee as input to the plant's 10 CFR 50.59 evaluation. The following events and accidents have been analyzed by the licensee for the Cycle 15 reload (Reference 2):

  • Load Rejection Without Bypass
  • Rod Withdrawal Error
  • Stability Analyses - Stability Option Ill Solution
  • Stability Analyses - Direct and Suppress Evaluation
  • Off-rated Power Dependent Limits
  • Off-rated Flow Dependent Limits The NRC reviewed the licensee's 10 CFR 50.59 screening and determined that the expected transient and accident analyses were performed for the LSCS2, Cycle 15, transition to the GNF2 fuel design.

3.3 Other Analyses Performed for Fuel Transition Mechanical compatibility analysis was explicitly performed for the fuel for LSCS2 (Reference 5).

Mechanical compatibility ensures that all fuel designs adhere to standard mechanical specifications established for this plant regardless of vendor.

In its October 31, 2013, letter, the licensee stated that the nuclear compatibility of GNF2 fuel and the Atrium-10 fuel is established through the design of the reference loading pattern using the modeling parameters for ATRIUM-10 fuel. The reference loading pattern establishes the licensing-basis core loading pattern and demonstrates that the designed core meets thermal margin and operability requirements, which demonstrate nuclear and thermal-hydraulic compatibility (Reference 5). The thermal-hydraulic compatibility report shows that the introduction of GNF2 fuel does not significantly affect the thermal-hydraulic performance of the resident ATRIUM-10 fuel in the core (Reference 5).

The thermal-hydraulic and nuclear compatibility of the mixed core was evaluated with NRC-approved methods. The methodology requires only parametric information regarding fuel characteristics, which was available for all fuel types. The assessments made to ensure the validity of the nuclear and thermal-hydraulic method fidelity against data provided for other vendor fuel are described in the licensee's October 31, 2013, letter (Reference 5). The NRC staff concludes that the compatibility between fuel types and demonstration of the modeling capability for mixed core situations has been validated by a multi-cycle benchmark of Atrium-1 O transition cores.

Thermal margin performance calculations were made using the GEXL 17 critical quality-boiling length correlation for GNF2 fuel (Reference 6). Thermal performance calculations for ATRIUM-10 fuel were carried out using the GEXL97 critical quality-boiling length calculation (Reference 7).

The NRC staff determined that all required analyses had been performed to determine mechanical, hydraulic, and neutronic compatibility between the new and resident fuel designs at the LSCS2 core during this transition cycle.

4.0 CONCLUSION

The NRC staff has reviewed the Cycle 15 COLR for LSCS2, selected 10 CFR 50.59 documents related to the fuel transition, related transient and accident analyses, and other mixed core and thermal margin analyses. The staff concludes that the COLR was prepared from the results of the reload licensing analyses for Cycle 15 using NRG-approved methodologies, and that all required mixed core analyses for thermal-hydraulic and neutronic compatibility analyses had been performed.

5.0 REFERENCES

1. Letter from Peter Karaba (LaSalle Station) to USN RC, "Unit 2 Cycle 15 Core Operating Limits Report (COLR), Exelon Generation, August 2013.
2. GNF Report 0000-156-1147-SRLR, Revision 1, "Supplemental Reload Licensing Report for LaSalle Unit 2 Reload 14 Cycle 15, January 2013.
3. LS-AA-104-1001, Revision 3, 50.59 Review Coversheet form, "LaSalle Unit 2 Cycle 15 (L2C15) Core Design/FCP 38153, LaSalle".
4. LS-AA-104-1003, Revision 3, 50.59 Screening Form, LaSalle, January 2013.
5. Letter, LDC-EXN-HA2-13-081, form Leah D. Crider (GNF) to Jill Fisher (Exelon), "GNF Response to NRC RAls for LaSalle Unit 2 Cycle 15 Core Operating Limits Report,"

October 13, 2013.

6. Global Nuclear Fuel, "General Electric Standard Application for Reactor Fuel (GESTAR II) (Supplement for United States), NEDE-24011-P-A-19-US, May 2012.
7. Global Nuclear Fuel, "GEXL97 Correlation for Atrium-1 O Fuel," NEDC-33106P-A, Revision 4, August 2012.
8. Letter from David P. Rhoades (Exelon Nuclea4) to USNRC, "Unit 2 Cycle 14 Core Operating Limits Report (COLR)," Exelon Generation, February 2011.
9. Letter from USN RC to Michael J. Pacilio (Exelon Nuclear), "LaSalle County Station 2 -

Issuance of Amendment No. 192 Regarding Technical Specification Change for Safety Limit Minimum Critical Power Ratio (TC No. ME9769)," USNRC, February 27, 2013.

10. NEI 96-07, Revision 1, Guidelines for 10 CFR 50.59 Implementation, "Nuclear energy Institute", November 2000.
11. Letter from Andrew A. Lingenfelter (Global Nuclear Fuel-Americas, LLC) to U.S. Nuclear Regulatory Commission, "Amendment 33 to NEDE-24011-P, General electric Standard

Application for Reactor Fuel (GESTAR II) and GNF2 Advantage Generic Compliance with NEDE-24011-P-A (GESTAR 11), NEDC-33270P, Revision 3, March 2010," Global Nuclear Fuel, March 2010.

Principal Contributor: Mathew M. Panicker, NRR

Should you have any questions, please contact me at 301-415-1380 or by email at blake.purnell@nrc.gov.

Sincerely, IRA!

Blake Purnell, Project Manager Plant Licensing 111-2 and Planning and Analysis Branch Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-37 4

Enclosure:

Staff Evaluation cc w/encl: Distribution via Listserv DISTRIBUTION:

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