L-PI-14-060, Annual Report of Changes and Errors to the Emergency Core Cooling System (ECCS) Evaluation Models

Annual Report of Changes and Errors to the Emergency Core Cooling System (ECCS) Evaluation Models

ML14175A959
Person / Time
Site:	Prairie Island
Issue date:	06/23/2014
From:	Davison K Northern States Power Co, Xcel Energy
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-PI-14-060
Download: ML14175A959 (57)

Text

Xcel Energy L-PI-14-060 JUN 2 3 2014 10 CFR 50.46 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington DC 20555-0001 Prairie Island Nuclear Generating Plant, Units 1 and 2 Dockets 50-282 and 50-306 Renewed License Nos. DPR-42 and DPR-60 2013 Annual Report of Changes and Errors to the Prairie Island Nuclear Generating Plant (PINGP) Emergency Core Cooling System (ECCS) Evaluation Models Pursuant to 10 CFR 50.46, Northern States Power Company, a Minnesota corporation, doing business as Xcel Energy (hereafter "NSPM") submits the 2013 annual report of changes and errors to the PINGP Units 1 and 2 ECCS evaluation models.

In January 2014, Prairie Island Unit 2 transitioned from the Large Break Loss of Coolant Accident (LBLOCA) analysis described in WCAP 16891-P to the Large Break LOCA analysis described in WCAP 17783-P. Since the current PINGP Unit 2 analysis of record (AOR) is WCAP 17783-P, the annual report will reference this analysis.

Therefore, the peak cladding temperature (PCT) rack-up sheets for Unit 2 will reference WCAP 17783-P rather than WCAP 16891-P. This transition was due to the Unit 2 Steam Generator replacement. The change in WCAP numbers unifies the two units, thus there is no new analysis (refer to L-PI-14-053). Following the Unit 2 Steam Generator replacement, the Unit 2 Small Break LOCA Analysis of Record (AOR) was changed to the current Unit 1 Analysis of Record.

Two changes to the PCT for PINGP Unit 1 and Unit 2 occurred since the last annual report for the large break LOCA analysis. The changes to the PCT were a -2 degree Fahrenheit (F) penalty to account for revised heat transfer multiplier distributions, and a

+25 degree F penalty to account for errors in the burst strain application. contains the "Non-Plant Specific (LOCA) Errors and Changes" and summarizes the changes made to both the large break LOCA (LBLOCA) and small break LOCA (SBLOCA) analysis.

The SBLOCA and LBLOCA peak clad temperature (PCT) assessment sheets for Unit 1 and Unit 2 are included in Enclosure 2. The limiting LOCA analysis PCT for PINGP Unit 1 and Unit 2, with consideration of all 10 CFR 50.46 assessments, remains the LBLOCA analysis as summarized in Enclosure 2.

1717 Wakonade Drive East

• Welch, Minnesota 55089-9642 Telephone: 651.388.1121

Document Control Desk Page 2 A historical summary of the LOCA PCT for both Prairie Island Unit 1 and Unit 2 changes and errors to the LBLOCA and SBLOCA Evaluation Models are included in Enclosure 2. is the Westinghouse Letter LTR-LIS-14-98.

Summary of Commitments This letter contains no new commitments and no revisions to existing commitments.

~~iJ~~

Kevin Davison Site Vice-President, Prairie Island Nuclear Generating Plant Northern States Power Company - Minnesota Enclosures (3) cc: Regional Administrator, Region Ill, USNRC Project Manager, Prairie Island Nuclear Generating Plant, USNRC Resident Inspector, Prairie Island Nuclear Generating Plant, USNRC

ENCLOSURE 1 Non-Plant Specific LOCA Errors and Changes 20 Pages Follow

March 17, 2014 Attachment to LTR-LIS-14-98 Page 1 of27 GENERA L CODE MAINTEN ANCE Backgroun d Various changes have been made to enhance the usability of codes and to streamline future analyses.

Examples of these changes include modifying input variable definitions, units and defaults; improving the input diagnostic checks; enhancing the code output; optimizing active coding; and eliminating inactive coding. These changes represent Discretionary Changes that will be implemented on a forward-fit basis in accordance with Section 4.1.1 ofWCAP-1 3451.

Affected Evaluation Model(s) 1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model 2004 Westinghouse Realistic Large Bre'ak LOCA Evaluation Model Using ASTRUM Estimated Effect The nature of these changes leads to an estimated Peale Cladding Temperature (PCT) impact of 0°F.

Attachment to LTR-LIS-14-98 March 17,2014 Page 2 of27 BURST ELEVATION SELECTION

Background

It is stated on page 11-20 of WCAP-16009-P-A that the burst option is applied at the elevation corresponding to the (Y{COBRA/TRAC) hurst elevation for the hot assembly rod. This approach was modified to apply the burst option at the HOTSPOT predicted burst elevation as described on page 19 of to LTR-NRC-06-8. The HOTSPOT code has been updated to incorporate the following changes to the burst elevation selection logic if multiple nodes burst at the same time: (1) the node that has the highest cladding temperature at the time of burst is selected; (2) if multiple nodes have the same burst time and cladding temperature at the time of burst, the lowest ordered elevation of those nodes is selected. These changes represent a closely-related group of Discretionary Changes in accordance with Section4.1.1 ofWCAP-13451.

Affected Evaluation Model(s) 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRUM Estimated Effect This improvement in burst elevation selection is a forward-fit change, leading to an estimated Peak Cladding Temperature (PCT) impact of0°F.

Attachment to LTR-LIS-14-98 March 17, 2014 Page 3 of27 ELEVATIONS FOR HEAT SLAB TEMPER ATURE INITIALI ZATION Backgr~und An error was discovered in WCOBRA/TRAC whereby an incorrect value would be used in the initial fuel rod temperature calculation for a fuel rod heat transfer node if that node elevation was specified outside of the bounds of the temperature initialization table. This problem has been evaluated for impact on existing analyses and its resolution represents a Discretionary Change in accordance with Section 4.1.1 ofWCAF-13451.

Affected Evaluation Model(s) 1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRUM Estimated Effect Based on inspection of plant analysis input, it was concluded that the input decks for existing analyses are not impacted by this error, leading to an estimated peak cladding temperature impact of0°F.

March 17,2014 Attachment to LTR~LIS-14-98 Page4 of27 HEAT TRANSFE R LOGIC CORREC TION FOR ROD BURST CALCULA TION Backgroun d A change was made to the WCOBRA/TRAC coding to correct an error which had disabled rod burst in separate effect test simulations. This change represents a Discretionary Change in accordance with Section 4.1.1 ofWCAP~l3451.

Affected Evaluation Model(s) 1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRUM Estimated Effect in Based on the nature of the change and the evaluation model requirements for plant modeling Westinghouse best estimate large break LOCA analyses with WCOBRA !TRAC, it is judged that existing analyses are not impacted by this change, leading to an estimated peak cladding temperature impact of 0°F.

Attachment to LTR-LIS-14-98 March 17,2014 Page 5 of27 WCOBRAIT RAC U19 FILE DIMENSIO N ERROR CORRECTI ON

Background

A problem was identified in the dimension of an array used to generate the ul9 file in WCOBRA/TRAC.

The u19 file is read during HSDRIVER execution and provides information needed to generate the HOTSPOT thermal-hydraulic history and user input files. The array used to write the desired information to the u19 file is dimensioned to 2000 in WCOBRA/TRAC. It is possible, however, for more than 2000 curves to be written to the ul9 file. If that is the case, it is possible that the curves would not be stored correctly on the ul9 file. A survey of current Best Estimate Large Break LOCA analyses indicated that the majority of plants had less than 2000 curves in their u19 files; therefore these plants are not affected by the change. For those plants with more than 2000 curves, plant-specific sensitivity calculations indicated that resolution of this issue does not impact the peak cladding temperature (PCT) calculation for prior analyses. This represents a Discretionary Change in accordance with Section 4.1.1 of WCAP-13451.

Affected Evaluation Model(s) 1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRUM Estimated Effect As discussed in the Background section, resolution of this issue does not impact the peak cladding temperature calculation for prior LBLOCA analyses, leading to an estimated peak cladding temperature impact of 0°F.

March 17, 2014 Attachment to LTR"LIS" 14"98 Page 6 of27 HEAT TRANSFER MODEL ERROR CORRECTIONS

Background

ed which affected the Several related changes were made to WCOBRA/TRAC .to correct errors discover used in calculation

• heat transfer models. These errors included calculat~on of the entrained liquid fraction tempera ture calculation, of the drop wall beat flux, application of the grid enhancement factor for grid on for the heat transfer calculation of the Reynold's number used in the Wong"Hochrieter correlati of cladding inner radius with coefficient from fuel rods to vapor, fuel rod initialization and calculation radiation compon ent in single phase creep, application of grid and two phase enhancement factors and ture when J=2. These errors have been vapor heat transfer, and reset of the critical heat flux tempera A analysis results. Co)Iecti on of these errors evaluated to estimate the impact on existing LBLOC ce **with Section 4.1.2 of represents a closely-related group of Non"Discretionary Changes in accordan WCM-1 3451.

Affected Evaluation Model{s) 1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model M

2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRU Estimated Effect and integral effects test Based on the results of representative plant calculations, separate effects ns have a negligib le local effect on heat transfer, simulations, it is concluded that the error correctio leading to an estimated peak cladding tempera ture impact of 0°F.

Attachment to LTR-LIS-14-98 March 17, 2014 Page 7 of27 CORRECTI ON TO HEAT TRANSFER :NODE INITIALIZA TION

Background

An error was discovered in the heat transfer node initialization logic in WCOBRA/TRAC whereby the heat transfer node center locations could be inconsistent with the geometric node center elevations. The primary effects of this issue are on the interpolated fluid properties and grid turbulent mixing enhancement at the heat transfer node. This problem has been evaluated for impact on existing analyses and its resolution represents a Non-Discretionary Change iri accordance with Section 4.1.2 of WCAP-13451.

Mfected Evaluation Model(s) 1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRUM Estimated Effect Based on engineering judgment and the results from a matrix of representative plant calculations, it is concluded that the effect of this error is within the code resolution, leading to an estimated peak cladding temperature impact of 0°F.

Attachment to LTR~LIS-14-98 March 17, 2014 Page 8 of27 MASS CONSERVATION ERROR FIX

Background

It was identified that mass was not conserved in WCOBRAffRAC one-dimensional component cells

. when void fraction values were calculated to be slightly out of the physical range (greater than 1.0 or smaller than 0.0). This was observed to result in artificial mass generation on the secondary side of steam generator components. Correction of this problem represents a Non~Discretionary Change in accon;lance with Section 4.1.2 of WCAP~ 13451.

Affected Evaluation Model(s) 1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRUM Estimated Effect This error was observed to primarily affect the mass on the secondary side of the steam generator. This issue was judged to have a negligible impact on existing LBLOCA analysis results, leading to an estimated peak cladding temperature impact of0°F.

March 17,2014 Attachment to LTR-LIS-14-98 Page 9 of27 CORREC TION TO SPLIT CHANNE L MOMENT UM EQUATIO N Backgroun d An error was discovered in the momentum equation calculations for split channels in WCOBRA/TRAC.

This error impacts the (1) continuity area of the phantom/boundary bottom cell; (2) bottom and top continuity area correction factors for the channel inlet at the bottom of a section and for the channel outlet at the top of a section; and (3) drop entrainment mass rate per unit volume and drop de-entrainment mass rate per unit volume contributions to the momentum calculations for split channels. This problem has been evaluated for impact on existing analyses and its resolution represents a Non-Discretionary Change in accordance with Section 4.1.2 ofWCAP-13451.

Affected Evaluation Model(s) 1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRUM Estimated Effect of Based on the results from a matrix of representative plant calculations, it is concluded that the effect this error on the quantities directly impacted by the momentum equation calculation s for split channels (velocities, flows, etc.) is negligible, leading to an estimated peak cladding temperature impact of0°F.

March 17,2014 Attachment to LTR-LIS-14-98 Page 10 of27 CHANGES TO VESSEL SUPERHEATED STEAM PROPE RTIES

Background

vessel super-heated water Several related changes were made to the WCOBRA/TRAC coding for the to be consiste nt with WCAP-12945-P'-A properties, including updating the HGAS subroutine coding in the TGAS subrouti ne to be consistent with Equation 10-6, updating the approximation of the enthalpy ure iteration method and convergence criteria in the HGAS subroutine coding, and updating the temperat a closely- related group ofNon-D iscretion ary Changes in the TGAS subroutine. These changes represent accordance with Section 4.1.2 ofWCAP-13451 .

Affected Evaluation Model(s) 1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model M

2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRU Estimated Effect y less than 1op impact on The updates to the calculations of the superheated steam properties had generall estimate d peak cladding tempera ture impact of0°F.

the resulting steam temperature values, leading to an

March 17, 2014 Attachment to LTR-LIS-14-98 Page 11 of27 UPDATE TO METAL DENSITY REFERENCE TEMPERATURES

Background

304 or 316 It was identified that for one-dimensional components in which heat transfer to stainless steel re for the metal density calculatio n was allowed to vazy; as a result the is modeled, the reference temperatu

. Correctio n of this problem represent s a Non-Disc retionary Change in total metal mass was not preserved accordance with Section 4.1.2 of WCAP-134? 1.

Affected Evaluation Model(s) 1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model 2004 Westinghouse Realistic Large Break LOCA Evaluation Model 'Using ASTRUM Estimated Effect break loss-of-This change primarily impacts the reactor coolant system loop piping modeled in the large A/TRAC models. It*was judged that the effect of this change on the coolant accident (LBLOCA) WCOBR was negligible , leading to an estimated peak cladding temperature peak cladding temperature results impact of 0°F.

March 17, 2014 Attachment to LTR-LIS-14-98 Page 12 of27 DECAY HEAT MODEL ~RROR CORRECTIONS

Background

correct the erroneously coded value The decay heat model in the WCOBRAJTRAC code was updated to to include the term for uncertainty of the yield fraction directly from fission for Group 1.9 ofPu-2 39, and power uncertainty. Correction of in the prompt energy per fission in the calculation of the decay heat Change s in accordance with Section these errors represents a closely-related group ofNon-Discretionary 4.1.2 ofWCA P-1345 1.

Affected Evaluation Model(s) 1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model ASTRUM 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using Estimated Effect power, leading to an estimated peak These changes have a negligible impact on the calculated decay heat cladding temperature impact of 0°F.

March 17,2014 Attachment to LTR-LIS-14-98 Page 13 of27 R

CORRECTION TO THE PIPE EXIT PRESSURE DROP ERRO

Background

al pressure drop at the split break TEE An error was discovered in WCOBRA/TRAC whereby the friction ted using the TEE hydraulic diameter connection to the BREAK component was incorrectly calcula been evaluated for impact on existing instead of the BREAK component length input. This error has Chang e in accordance with Section 4.1.2 of analyses and its resolution represents a Non-Discretionary WCAP-1;3451.

Affected Evaluation Model(s)

Model 1996 Westinghouse Best Estimate Large Break LOCA Evaluation Break LOCA Evalua tion Model Using ASTRUM 2004 Westinghouse Realistic Large Estimated Effect tions, it is concluded that the effect of Based on the results from a matrix of representative plant calcula negligible, leading to an estimated peak this error on the pressure at the break and the break flow is cladding temperature impact of 0°F.

March 17, 2014 Attachment to LTR-LIS-14-98 Page 14 of27 GRID HEAT TRANSFER ENHANCEMENT CALCULATION

===.

Background===

elevation s for An issue was identified which could affect the calculation of the heat transfer at gridded (EMs). For a Best-Estimate (BE) Large-Break Loss-of-Coolant Accident (LBLOCA) Evaluation Models based on an erroneous specific input condition, the grid heat transfer enhancement factor is calculated coefficien t at gridded elevation s.

core geometry, which can cause an over-prediction of the heat transfer LBLOCA analysis results. The resolution This issue has been evaluated to estimate the impact on existing

-13451.

of this issue represents a Non-Discretionary Change in accordance With Section 4.1.2 ofWCAP Affected Evaluation Model(s) 1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRUM Estimated Effect analysis results, The effect described above was judged to have a negligible effect on existing LBLOCA leading to an estimated Peak Cladding Temperature (PCT) impact of 0°F.

March 17,2014 Attachment to LTR-LIS-14-98 Page 15 of27 REVISED HEAT TRANSFER MULTI PLIER DISTRIBUTIONS Backgro und impacts of these changes Several changes and error corrections were made to WCOBRA/TRAC and the this investigation, errors on the heat transfer multiplier uncertainty distributions were investigated. During includin g errors in the grid were discovered in the development of the original multiplier distributions, and G2 Reflood tests, and errors in locations specified in the WCOBRA/TRAC models for the G2 Refill multipli er distribut ion. Therefore, the processing test data used to develop the reflood heat transfer heat transfer multipli er distribut ions were blowdo'Wn beatup, blowdown cooling, refill, and reflood er developm ent, the evaluati on time window s for each redeveloped. For the reflood heat transfer multipli on were separate ly defined based on the time at which set of test experimental data and each test simulati d flow film boiling beat transfer conditio ns characte ristic of the the test or simulation exhibited disperse on evaluated for impact reflood time period. The revised beat transfer multiplier distributions have been ry of Non-Dis cretiona existing analyses. Resolution of these issues represents a closely related group Changes in accordance with Section 4.1.2 ofWCAP-13451.

Mfected Evaluat ion Model(s) 1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model M

2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRU Estimat ed Effect 2 transient behavior was A plant transient calculation representative of Prairie Island Unit 1 and Unit

, a matrix of HOTSPOT performed with the latest version of WCOBRA/TRAC. Using this transient er distribution changes.

calculations was performed to estimate the effect of the heat transfer multipli s from limiting cases Using these results and considering the heat transfer multiplier uncertainty attribute been establish ed for 10 CFR for Prairie Island Unit 1 and Unit 2, an estimated PCT effect of -2°F bas RSG AOR) and an estimated PCT 50.46 reporting purposes for Prairie Island Unit 1 and Unit 2 (future reporting purposes for Prairie Island Unit 2 effect of -16°F has been established for 10 CFR 50.46 (current AOR).

March 17,2014 Attachment to LTR-LIS-14-98 Page 16 of27 ERROR IN BURST STRAIN APPLIC ATION Backgro und for the An error in the application of the burst strain was discovered in HOTSPOT. The equation 2945-P-A.

application of the burst strain is given as Equation 7-69 in WCAP-16009-P-A and in WCAP-1 strain, and the The outer radius of the cladding after burst occurs should be calculated based on the burst T, the burst strain inner radius of the cladding should be calculated based on the outer radius. In HOTSPO radius is then calculated is applied to the calculation of the cladding inner radius. The cladding outer rather than the based on the inner radius. As such, the burst strain is incorrectly applied to the inner radius at the burst elevation after burst occurs.

outer radius, which impacts the resulting cladding geometry cladding at the burst node and more fuel Correction of the erroneous calculation results in thinner in the Peak Cladding Temperat ure (PCT) at the burst relocating into the burst node, leading to an increase the impact on existing Best-Esti mate (BE) Large-Br eak node. This issue has been evaluated to estimate A) analysis results. The resolution of this issue represent s a Non-Loss-of-Coolant Accident (LBLOC Discretionary Change in accordance with Section 4.1.2 ofWCAP-13451.

Affected Evaluatio n Model(s) 1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRUM Estimate d Effect plant-specific The issue described above was evaluated based on the results of executing the most limiting a HOTSPO T version that includes the correction of this error.

HOTSPOT runs for similar plants with This resulted in an estimated PCT impact of 25°F for Prairie Island Units 1 and 2.

Attachment to LTR-LIS-14-98 March 17,2014 Page 17 of27 CHANGES TO GRID BLOCKAGE RATIO AND POROSITY

Background

A change in the methodology used to calculate grid blockage ratio and porosity for Westinghouse fuel resulted in a change to the grid inputs for large break loss-of-coolant accident (LBLOCA) analyses. Grid inputs affect heat transfer in the core during a LBLOCA. This change represents a Non-Discretionary Change in accordance with Se<?tion 4.1.2 ofWCAP-13451.

Affected Evaluation Model(s) 1996 Westinghouse Best Estim!!-te Large Break LOCA Evaluation Model 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRl.JM Estimated Effect The updates to the methodology to calculate grid blockage ratio and

• porosity used as input in Westinghouse LBLOCA models resuited in a negligible change to heat transfer in the core for the fuel type used in Prairie Island Unit 1 and Unit 2. The estimated penalty associated with the changes is 0°F for 10 CFR 50.46 reporting purposes.

March 17,2014 Attachment to LTR-LIS-14-98 Page 18 of27 INITIAL FUEL PELLET AVERAGE TEMPER ATURE UNCERTAINTY CALCULATION Backgro und Large-In the Automated Statistical Treatment of Uncertainty Method (ASTRUM) Best-Estimate (BE)

) Evaluatio n Model (EM), uncertain ties are applied to the gap Break Loss-of-Coolant Accident (LBLOCA pellet thermal conductiv ity to capture the uncertain ty in the initial fuel pellet heat transfer coefficient and temperature average temperature. This approach was compared to the initial fuel pellet average conservat ive in uncertainties predicted by the PAD code at beginning-of-life conditions and found to be re uncertain ty Section 25-4-2-4 of WCAP-12945-P-A. However, the initial fuel pellet average temperatu ty range predicted range analyzed at higher burnups in the ASTRUM EM is much wider than the uncertain pellet average by the PAD code, which may result in excessively low or high analyzed initial fuel impact on existing ASTRUM LBLOCA temperatures. This issue has been evaluated to estimate the s a Non-Disc retionary Change in accordanc e with analysis results. The resolution of this issue represent Section 4.1.2 ofWCAP-13451.

Affected Evaluati on Model(s) 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRUM Estimate d Effect LBLOCA The issue described above is judged to have either no effect or a negligible effect on existing (PCT) impact of 0°F.

• analysis results, leading to an estimated Peak Cladding Temperature

Attachment to LTR-LIS-14-98 March 17,2014 Page 19 of27 SBLOCTA CLADDING STRAIN REQUIREMEN T FOR FUEL ROD BURST Background 1 An error was discovered in the minimum local strain required for burst for ZIRL0 cladding in the SBLOCTA code. The coding does not enforce reaching the minimum percent local strain threshold prior to calculating fuel rod burst. However, a review of licensing basis analyses revealed no instances of this error impacting calculated results. Resolution of this issue represents a Non-Discretionary Change to the Evaluation Model as described in Section 4.1.2 ofWCAP-13451 .

Affected Evaluation Model(s) 1985 Westinghouse Small Break LOCA Evaluation Model with NOTRUMP Estimated Effect Based on a review of current licensing basis analyses, and the phenomena and physics of a small break LOCA transient, it is concluded that this error has a negligible effect on small break LOCA analysis results, leading to an estimated Peak Cladding Temperature (PCT) impact of 0°F.

1 ZIRLO is a registered trademark of Westinghouse Electric Company LLC, its affiliates and/or its subsidiaries in the United States of America and may be registered in other countries throughout the world. All rights reserved.

Unauthorized use is strictZv prohibited. Other names may be trademarks of their respective owners

Attachment to LTR-LIS-14-98 March 17,2014 Page20 of27 PRAIRIE ISLAND UNIT 2 EARLIER CONTAINMENT SPRAY ACTUATION TIME DUE TO DEGRAD ED FAN COOLER HEAT REMOVA L CAP ACITY Backgrou nd

• During the installation of the replacement steam generators (RSGs) at Prairie Island Unit 2, fan coolers were damaged, resulting in a degraded heat removal capacity. Due to the design' of the Prairie Island emergency core cooling system (ECCS), a complete interruption in high head safety injection (HHSI) flows can occur during the switchover to sump recirculation for the small break loss-of-coolant accident (SBLOCA) transient. The Prairie Island analysis-of-record (AOR) uses containment pressurization calculations to determine the time when the containment sprays would actuate for the smaller break sizes (1.5-inch and 2-inch breaks). This ultimately dictates the time to switch to ECCS sump recirculation and therefore the flow interruption. The containment pressurization calculations are impacted by the degraded fan coolers and result in an earlier containment spray actuation time. This change represents a Non-Discretionary Change to the Evaluation Model as described at Section 4.1.2 of WCAP-13451.

Affected Evaluation Model(s) 1985 Westinghouse Small Break LOCA Evaluation Model with NOTRUMP Estimated Effect When considering the reduced heat transfer capability of the fan coolers for the 1.5-inch and 2-inch breaks, the containment spray pumps actuate earlier than modeled in the AOR but the interruption in is ECCS flow during the switchover to sump recirculation still occurs after the core has recoveFed. There sufficient RCS inventory during the flow interruption such that additional, post-switch over core uncovery 2

would not occur. Therefore, this issue is estimated as a 0°F PCT impact on the Prairie Island Unit SBLOCA analysis with the RSGs installed.

ENCLOSURE 2 LOCA peak Clad Temperature Summary (Rack-Up Sheets)

Prairie Island Nuclear Generating Plant (Includes plant specific changes and non-zero plant specific changes) 4 Pages Follow

March 17,2014 Attachment to LTR-LIS-14-98 Page 21 of27 Large Break Westingh ouse LOCA Peak Clad Temperat ure Summary for ASTRUM Best Estimate Plant Name: Prairie Island Unit 1 Utility Name: Xcel Energy, Inc Revision Date: 2/27/2014 Analysis Informatio n ASTR~ Analysis 11/30/2007 Limiting Break Split E~:

FQ: 2.5 FdH: 1.77 Fuel: 422 Vantage+ SGTP(%) : 10 Notes:

Clad Temp (OF) Ref. Notes LICENSI NG BASIS 1765 1 Analysis-Of-Record PCT PCT ASSESSMENTS (Delta PCT)

A. PRIOR ECCS MODEL ASSESSM ENTS (a) 227 2 I . Evaluation of Fuel Pellet Thermal Conductivity Degradation and Peaking Factor Bum down B. PLANNED PLANT MODIFIC ATION EVALUA TIONS I . None 0 C. 2013 ECCS MODEL ASSESSM ENTS 3 I . Revised Heat Transfer Multiplier Distributions -2 25 4 2

• Error in Burst Strain Application D. OTHER*

I . None 0 LICENSI NG BASIS PCT + PCT ASSESSM ENTS PCT= 2015 to

+ It is recommended that the licensee determine if these PCT allocations should be considered with respect 10 CFR 50.46 reporting requirements.

Reference for the Prairie I . WCAP-16890-P, Revision l, "Best-Estimate Analysis ofthe Large-Break Loss-of-Coolant Accident Island Nuclear Plant Unit 1 Using ASTRUM Methodology," June 2008.

Pellet Thermal 2 . LTR-LIS-12-414, "Prairie Island Units 1 and 2, I0 CFR 50.46 Notification and Reporting for Fuel Conductivity Degradation and Peaking Factor Bumdown," September 20, 2012.

Tran~fei' 3 . LTR-LIS-13-366, Revision 1, "Prairie Island Units I and 2 10 CFR 50.46 Report for Revised Heat Multiplier Distributions," August 2013.

Error 4 . LTR-LIS-14-50, "Prairie Island Units I and 2 10 CFR 50.46 Report for the HOTSPOT Burst Strain Correction," January 2014.

Notes:

(a) This evaluation credits peaking factor bumdown, see Reference 2.

March 17,2014 Attachment to LTR-LIS-14-98 Page 22 of27 Westinghouse LOCA Peak Clad Temperature Summary for Appendix K Small Break Plant Name: Prairie Island Unit 1 Utility Name: Xcel Energy, Inc Revision Date: 2/27/2014 Analysis Information EM: NOTRUMP Analysis 1/21/2008 Limiting :Break 3 inch FQ: 2.5 FdH: 1.77 Fuel: 422 Vantage+ SGTP (%): 10 Notes: Zirlo (14X14), Framatome RSG Clad Temp (DF) Ref. Notes LICENSING BASIS 959 Analysis-Of-Record PCT PCT ASSESSMENTS (Delta PCT)

A. PRIOR ECCS MODEL ASSESSMENTS 0

I . None B. PLANNED PLANT MODIFICATION EVALUATIONS 0

I . None C. 2013 ECCS MODEL ASSESSMENTS 0

I . None D. OTHER* 0 I . None LICENSING BASIS PCT + PCT ASSESSMENTS PCT= 959

• It is recommended that the licensee detennine ifthese PCT allocations should be considered with respect to 10 CFR 50.46 reporting requirements.

Reference I . LTR-LIS-08-158, "Transmittal of Future Prairie Island Units I and 2 PCT Summaries," February 2008.

Notes:

None

Attachment-to LTR-LIS-14-98 March 17,2014 Page 23 of27 Westinghouse LOCA Peak Clad Temperature. Summary for ASTRUM Best Estimate Large Break Plant Name: Prairie Island Unit 2 Utility Name: Xcel Energy, Inc Revision Date: 2/27/2014 Analysis Information EM: ASTRUM (2004) Analysis Date: 11/30/2007 Limiting Break Size: Split FQ: 2.5 FdH: 1.77 Fuel: 422 Vantage+ SGTP(%): 10 Notes:

Clad Temp (OF) Ref. Notes LICENSING BASIS Analysis-Of-Record PCT 1765 PCT ASSESSMENTS (Delta PCT)

A. PRIOR ECCS MODEL ASSESSMENTS I . Evaluation of Fuel Pellet Thermal Conductivity Degradation and Peaking 227 2 (a), (b)

Factor Bum down B. PLANNED PLANT MODIFICATION EVALUATIONS 1

• None 0 C. 2013 ECCS MODEL ASSESSMENTS 1

• Revised Heat Transfer Multiplier Distributions -2 3 2 . Error in Burst Strain Application 25 4 D. OTHER*

I . None 0 LICENSING BASIS PCT + PCT ASSESSMENTS PCT= 2015

• It is recommended that the licensee determine if these PCT allocations should be considered with respect to I0 CFR 50.46 reporting requirements, References I . WCAP-17783-P, "Best-Estimate Analysis of the Large-Break Loss-of-Coolant Accident for Prairie Island Units I and 2 with Replacement Steam Generators Using ASTRUM Methodology," June 2013.

2 , LTR-LIS-12-414, "Prairie Island Units I and 2, 10 CFR 50.46 Notification and Reporting for Fuel Pellet Thermal Conductivity Degradation and Peaking Factor Bumdown," September 20, 2012.

3 , LTR-LIS-13-366, Revision I, "Prairie Island Units I and 2 10 CFR 50.46 Report for Revised Heat Transfer Multiplier Distributions," August 2013.

4 . LTR-LIS-14-50, "Prairie Island Units I and 2 10 CFR 50.46 Report for the HOTSPOT Burst Strain Error Correction," January 2014.

Notes:

(a) This evaluation credits peaking factor bumdown, see Reference 2.

(b) The reporting text and line item originally identified for Unit I in Reference 2 is applicable to Unit 2 with RSGs.

Attachment to LTR-LIS-14-98 March 17, 2014 Page 25 of27 Westinghouse LOCA ~eak Clad Temperature Summary for Appendix K Small Break Plant Name: Prairie Island Unit 2 Utility Name: Xcel Energy, Inc Revision Date: 2/27/2014 Analysis Information EM: NOTRUMP Analysis Date: 1/21/2008 Limiting Break Size: 3 inch FQ: 2.5 FdH: 1.77 Fuel: 422 Vantage+ SGTP (%): 10 Notes: Zirlo (14X14), AREVA RSG Clad Temp (OF) Ref. Notes LICENSING BASIS Analysis-Of-Record PCT 959 1, 2 a PCT ASSESSMENTS (Delta PCT)

A. PRIOR ECCS MODEL ASSESSMENTS 1 . None 0 B. PLANNED PLANT MODIFICATION EVALUATIONS I . None 0 C. 2013 ECCS MODEL ASSESSMENTS I

• None 0 D. OTHER*

I . None 0 LICENSING BASIS PCT + PCT ASSESSMENTS PCT= 959

• It is recommended that the licensee detennine if these PCT allocations should be considered with respect to I0 CFR 50.46 reporting requirements.

References I . LTR-LIS-08-158, "Transmittal ofFuture Prairie Island Units 1 and 2 PCT Summaries," February 2008.

2 . LTR-LIS-13-274, "Prairie Island Units I and 2, 10 CFR 50.46 Summary Sheets for the Evaluation to Support the Unit 2 Installation of AREVA Model 56/19 Replacement Steam Generators (RSGs)," June 20 I3.

Notes:

(a) The Unit I AOR is applicable to Unit 2 with the RSGs installed.

ENCLOSURE 3 Westinghouse Letter LTR-LIS-14-98 28 Pages Follow

Westinghouse Non-Proprietary Class 3 Westinghouse Electric Company Westinghouse Engineering, Equipment and Major Projects 1000 Westinghouse Drive Cranberry Township, Pennsylvania 16066 USA Direct tel: (412) 374-2202 Direct fax: (724) 720-0857 e-mail: teoliscd@westinghouse.com Our ref: LTR-LIS-14-98 March 17,2014 Prairie Island Units 1 and 2 10 CFR 50.46 Annual Notification and Reporting for 2013

Dear Sir or Madam:

Company This is a notification of 10 CFR 50.46 reporting infonnation pertaining to the Westinghouse Electric Westingho use Methodolo gy for Implement ation of Evaluation Models/analyses. As committed to in WCAP-13451, Core Cooling System (ECCS) 10 CFR 50.46 Reporting, Westinghouse is providing an Annual Report for Emergency changes and errors Evaluation Model changes and errors for the 2013 model year. Standardized reporting pages for all the for the Evaluation Models utilized for your plant(s) are enclosed, consistent with the commitment following sheets are enclosed. All necessary revisions for any non-NUPIC audit in early 1999. Peak Clad Temperature (PCT) of oaF will zero, non-discretionary, PCT change to Section C have been included. Non-discretionary PCT impacts of the model for 2013 will generally not be presented on the PCT sheet. Any plant-specific errors in the application (except any also be provided in Section C with discussion enclosed or cited. The Evaluation Model changes and errors plant-specific errors in the application of the model) will be provided to the NRC via Westinghouse letter.

CFR 50.46.

This infonnation is for your use in making a detennination relative to the reporting requirements of 10 Manageme nt The infonnation that is provided in this letter was prepared in accordance with Westinghouse's Quality System (QMS).

Author: (Electronically Approved)* Verified: (Electronically Approved)*

Carmen D. Teolis Danial W. Utley LOCA Integrated Services I LOCA Integrated Services II Approved: (Electronically Approved)*

Kyler J. Gates Manager, LOCA Integrated Services II

Attachment:

10 CFR 50.46 Reporting Text and PCT Summary Sheets (27 Pages)

• Electronically appraved records are authenticated in the electronic document management system.

© 2014 Westinghouse Electric Company LLC All Rights Reserved

March 17,2014 Attachment to LTR-LIS-14-98 Page 1 of27 GENERAL CODE MAINTENANCE Bacl{ground future analyses.

Various changes have been made to enhance the usability of codes and to streamline variable definition s, units and defaults; improving the Examples of these changes include modifying input optimizin g active coding; and eliminatin g inactive input diagnostic checks; enhancing the code output; nary Changes that will be implemen ted on a forward-f it basis in coding. Thest1 changes represent Discretio accordance with Section4.1.1 ofWCAP -13451.

Affected Evaluation Model(s) 1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRUM Estimated Effect impact of 0°F.

The nature of these changes leads to an estimated Peak Cladding Temperature (PCT)

Attachment to LTR-LIS-14-98 March 17,2014 Page 2 of27 BURST ELEVATION SELECTION

Background

It is stated on page 11-20 of WCAP-16009-P-A that the burst option is applied at the elevation corresponding to the QYCOBRAJTRAC) burst elevation for the hot assembly rod. This approach was modified to apply the burst option at the HOTSPOT predicted burst elevation as described on page 19 of to LTR-NRC-06-8. The HOTSPOT code has been updated to incorporate the following changes to the burst elevation selection logic if multiple nodes burst at the same time: (1) the node that has the highest cladding temperature at the time of burst is selected; (2) if multiple nodes have the same burst time and cladding temperature at the time of burst, the lowest ordered elevation of those nodes is selected. These changes represent a closely-related group of Discretionary Changes in accordance with Section 4.1.1 of WCAP-13451.

Affected Evaluation Model(s) 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRUM Estimated Effect This improvement in burst elevation selection is a forward-fit change, leading to an estimated Peak Cladding Temperature (PCT) impact of0°F.

Attachment to LTR-LIS-14-98 March 17, 2014 Page 3 of27 ELEVATIONS FOR HEAT SLAB TEl\'IPERATURE INITIALIZATION

Background

An error was discovered in WCOBRA/TRAC whereby an incorrect value would be used in the initial fuel rod temperature calculation for a fuel rod heat transfer node if that node elevation was specified outside of the bounds of the temperature initialization table. This problem has been evaluated for impact on existing analyses and its resolution represents a Discretionary Change in accordance with Section 4.1.1 of WCAP-13451.

Affected Evaluation Model(s) 1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRUM Estimated Effect Based on inspection of plant analysis input, it was concluded that the input decks for existing analyses are not impacted by this error, leading to an estimated peak cladding temperature impact of oop.

Attachment to LTR-LIS-14-98 March 17, 2014 Page4 of27 HEAT TRANSFER LOGIC CORRECTION FOR ROD BURST CALCULATION

Background

A change was made to the WCOBRA/TRAC coding to correct an error which had disabled rod burst in separate effect test simulations. This change represents a Discretionary Change in accordance with Section 4.1.1 of WCAP-13451.

• Affected Evaluation Model(s) 1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model.

2004 Westinghouse Realistic Large Break LOCA Evaluation Model ~sing ASTRUM Estimated Effect Based on the nature of the change and the evaluation model requirements for plant morfeling in Westinghouse best estimate large break LOCA analyses with WCOBRA/TRAC, it is judged that existing analyses are not impacted by this change, leading to an estimated peak cladding temperature impact of 0°F.

Attachment to LTR-LIS-14-98 March 17,2014 Page 5 of27 WCOBRA/TRA C U19 FILE DIMENSION ERROR CORRECTION

Background

A problem was identified in the dimension of an array used to generate the u19 file in WCOBRA/TRAC.

The u19 file is read during HSDRIVER execution and provides information needed to generate the HOTSPOT thermal-hydraulic history and user input files. The array used to write the desired information to the u19 file is dimensioned to 2000 in WCOBRA/TRAC. It is possible, however, for more than 2000 curves to be written to the u19 file. If that is the case, it is possible that the curves would not be stored correctly on the ul9 file. A survey of current Best Estimate Large Break LOCA analyses indicated that the majority of plants had less than 2000 curves in their ul9 files; therefore theseplants are not affected by the change. For those plants with more than 2000 curves, plant-specific sensitivity calculations indicated that resolution of this issue does not impact the peak cladding temperature (PCT) calculation for prior analyses. This represents a Discretionary Change in accordance with Section 4.1.1 of WCAP-13451.

Mfected Evaluation Model(s) 1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRUM Estimated Effect As discussed in the Background section, resolution of this issue does not impact the peak cladding temperature calculation for prior LBLOCA analyses, leading to an estimated peak cladding temperature impact of 0°F.

March 17,2014 Attachment to LTR-LIS-14-98 Page 6 of27 HEAT TRANSFER MODEL ERROR CORREC TIONS Backgroun d Several related changes were made to WCOBRA/TRAC to correct errors discovered which affected the heat transfer models. These errors included calculation of the entrained liquid fraction used in calculation of the drop wall heat flux, application of the grid enhancement factor for grid temperature calculation, calculation of the Reynold's number used in the Wong-Hochrieter correlation for the heat transfer coefficient from fuel rods to vapor, fuel rod initialization and calculation of cladding inner radius with creep, application of grid and two phase enhancement factors and radiation component in single phase vapor heat transfer, and reset of the critical heat flux temperature when J=2. These errors have been evaluated to estimate the impact on existing LBLOCA analysis results. Correction of -these errors represents a clb11ely-related group of Non-Discretionary Changes in accordance with Section 4.1.2 of WCAP-13451.

Affected Evaluation Model(s) 1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRUM Estimated Effect Based on the results of representative plant calculations, separate effects and integral effects test simulations, it is concluded that the error corrections have a negligible local effect on heat transfer, leading to an estimated peak cladding temperature impact of0°F.

March 17,2014 Attachment to LTR-LIS-14-98 Page 7 of27 CORRECTION TO HEAT TRANSFER NODE INITIALIZATION

Background

whereby the An error was discovered in the heat transfer node initialization logic in WCOBR NTRAC center elevations. The heat transfer node center locations could be inconsistent with the geometric node grid turbulent mixing primary effects of this issue are on the interpolated fluid properties and analyses enhancement at the heat transfer node. This problem has been evaluated for impact on existing e with Section 4.1.2 of WCAP-and its resolution represents a Non-Discretionary Change in accordanc 13451.

Mfected Evaluation Model(s) 1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRUM Estimated Effect ns, it is Based on engineering judgment and the results from a matrix of representative plant calculatio to an estimated peak cladding concluded that the effect of this error is within the code resolution, leading temperature impact of0°F.

March 17, 2014 Attachment to LTR-LIS-14-98 Page 8 of27 MASS CONSER VATION ERROR FIX Backgro und nt cells It was identified that mass was not conserved in WCOBRA/TRAC one-dimensional compone d to b~ slightly out of the physical range (greater than 1.0 or when void fraction values were calculate to result in artificial mass generatio n on the secondary side of steam smaller than 0.0). This was observed n of this problem represent s a Non-Disc retionary Changt;: in accordan ce generator components. Correctio with Section 4.1.2 ofWCAP -13451.

Affected Evaluatio n Model(s) 1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model 2004 Westirighouse Realistic Large Break LOCA Evaluation l-4?del Using ASTRUM Estimate d Effect .

This error was observed to primarily affect the mass ort the Secondary side of the steam generator. This*

issue was judged to have a negligible impact on existing LBLOCA analysis results, leading to an estimated peal.< cladding temperatu re impact of 0°F.

March 17,2014 Attachment to LTR-LIS-14-98 Page 9 of27 CORRE CTION TO SPLIT CHANNEL MOMENTUM EQUATION

Background

in WCOBRAJTRAC.

An error was discovered in the momentum equation calculations for split channels cell; (2) bottom and top This error impacts the (1) continuity area of the phantom/boundary bottom and for the channel outlet continuity area correction factors for the channel inlet at the bottom of a section and drop de-entra inment mass at the top of a section; and (3) drop entrainment mass rate per unit volume split channels . This problem has rate per unit volume contributions to the momentum calculations for n represen ts a Non-Dis cretiona ry Change been evaluated for impact on existing analyses and its resolutio in accordance with Section 4.1.2 of WCAP-13451.

Mfected Evaluation Model(s) 1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model M

2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRU Estimated Effect ed that the effect of Based on the results from a matrix ofrepresentative plant calculations, it is conclud equation calculati ons for split channels this error on the quantities directly impacted by the momentum d peak cladding tempera ture impact of0°F.

(velocities, flows, etc.) is negligible, leading to an estimate

Attachment to LTR-LIS-14-98 March 17,2014 Page 10 of27

. CHANGES "TO VESSEL SUPERHEA TED STEAM PROPERTI ES Background .

Several related changes were made to the WCOBRAITRAC coding for the vessel super-heated water properties, including updating the HGAS subroutine coding to be consistent with WCAP-12945-P-A Equation 10-6, updating the approximation of the enthalpy in the TGAS subroutine to be consistent with the HGAS subroutine coding, and updating the temperature iteration method and convergence criteria in the TGAS subroutine. These changes represent a closely-related group of Non-Discretionary Changes in accordance with Section 4.1.2 ofWCAP-13451.

Mfected Evaluation Model(s) 1996 Westinghouse Best Estimat!;'l Large Break LOCA Evaluation Model **

2004 Westinghous.e Realistic Lru.:ge Break LOCA Evaluation

. Model Using ASTRUM Estimated Effect The updates to the calculations of the superheated steam properties had generally less than 1op impact on the resulting steam temperature values, leading to an estimated peak cladding temperature impact of 0°F.

March 17, 2014 Attachment to LTR-LIS-14-98 Page 11 of27 UPDATE TO METAL DENSITY REFERENCE TEMPERATURES

Background

304 or 316 It was identified that for one-dimensional components in which heat transfer to stainless steel as a result the is modeled, the reference temperature for the metal density calculation was allowed to* vary; retionary Change in to tar' metal mass was not preserved. Correction of this problem represents a Non-Disc accordance with Section 4.1.2 ofWCAP -13451.

Affected Evaluation Model{s) 1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRUM Estimated Effect

'break loss-of-This change primarily impacts the reactor coolant system loop piping modeled in the large

) WCOBRA JTRAC models. It was judged that the effect ofthis change on the coolant accident (LBLOCA temperature peak cladding temperature results was negligible, leading to an estimated peak cladding impact of 0°F.

March 17,2014 Attachment to LTR~LIS~l4-98 Page 12 of27 DECAY HEAT MODEL ERROR CORRECTIONS

Background

ly coded value The decay heat model in the WCOBRAJTRAC code was updated to correct the erroneous uncertainty of the yield fraction directly from fission for Group 19 of Pu~239, and to include the tenn for uncertain ty. Correctio n of in the prompt energy per fission in the calculation of the decay heat power in accordanc e with Section these errors represents a closely~related group of Non-Discretionary Changes 4.1.2 ofWCAP~l3451.

Affected Evaluation Model(s) 1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRUM Estimated Effect estimated peak These changes have a negligible impact on the calculated decay heat power, leading to an cladding temperature impact of 0°F.

March 17,2014 Attachment to LTR-LIS-14-98 Page 13 of27 CORRECTION TO THE PIPE EXIT PRESSURE DROP ERROR

Background

An error was discovered in WCOBRA/TRAC whereby the frictional pressure drop at the split break TEE TEE hydraulic diameter connection to the BREAK component was incorrectly calculated using the d for impact on existing instead of the BREAK component length input. This error has been evaluate ce with Section 4.1.2 of analyses and its resolution represents a Non-Discretionary Change in accordan WCAP-13451.

Affected Evaluation Model(s) 1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model M

2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRU Estimated Effect ed that the effect of Based on the results from a matrix of representative plant calculations, it is conclud to an estimated peak this error on the pressure at the break and the break flow is negligible, leading cladding temperature impact of0°F.

Attachment to LTR-LIS-14-98 March 17,2014 Page 14 of27 GRID HEAT TRANSFE R ENHANCEMENT CALCULATION

Background

An issue was identified which could affect the calculation of the heat transfer at gridded elevations for a

Best-Estimate (BE) Large-Break Loss-of-Coolant Accident (LBLOCA) Evaluation Models (EMs). For specific input condition, the grid heat transfer enhancement factor is calculated based on an erroneous core geometry, which can cause an over-prediction of the heat transfer coefficient at gridded elevations.

This issue has been evaluated to estimate the impact on existing LBLOCA analysis results. The resolution of this issue represents a Non-Discretionary. Change in accordance with Section 4.1.2 of WCAP-13451.

Affected Evaluation Model(s) 1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model

• 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRUM Estimated Effect The effect described above was judged to have a negligible effect on existing LBLOCA analysis results, leading to an estimated Peak Cladding Temperature (PCT) impact of0°F.

March 17, 2014 Attachment to LTR-LIS-14-98 Page 15of27 REVISED HEAT TRANSFER MULTIPL IER DISTRIBUTIONS Backgroun d Several changes and error corrections were made to WCOBRA/TRAC and the impacts of these changes on the heat transfer multiplier uncertainty distributions were investigated. During this investigation, errors were discovered in the development of the original multiplier distributions, including errors in the grid locations specified in the WCOBRA/TRAC models for the 02 Refill and 02 Reflood tests, and errors in processing test data used to develop the reflood heat transfer multiplier distribution. Therefore, the blowdown heatup, blowdown cooling, refill, and reflood heat transfer multiplier distributions were redeveloped. For the reflood heat transfer multiplier development, the evaluation time windows for each set of test experimental data and each test simulation were separately defined based on the time at which the test or simulation exhibited dispersed flow film boiling heat transfer conditions characteristic of the reflood time period. The revised heat transfer multiplier distributions have been evaluated for impact on existing analyses. Resolution of these issues represents a closely related group of Non-Discretionary Changes in accordance with Section 4.1.2 ofWCAP-13451.

Affected Evaluation Model(s) 1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRUM Estimated Effect A plant transient calculation representative of Prairie Island Unit 1 and Unit 2 transient behavior W!l:S performed with the latest version of WCOBRA/TRAC. Using this transient, a matrix of HOTSPOT calculations was performed to estimate the effect of the heat transfer multiplier distribution changes.

Using these results and considering the heat transfer multiplier uncertainty attributes from limiting cases for Prairie Island Unit 1 and Unit 2, an estimated PCT effect of -2°F has been established for 10 CFR 50.46 reporting purposes for Prairie Island Unit 1 and Unit 2 (future RSO AOR) and an estimated PCT effect of -16°F has been established for 10 CFR 50.46 reporting purposes for Prairie Island Unit 2 (current AOR).

March 17, 2014 Attachment to LTR-LIS-14-98 Page 16 of27 ERROR IN BURST STRAIN APPLICA TION Backgroun d An error in the application of the burst strain was discovered in HOTSPOT. The equation for the application of the burst strain is given as Equation 7-69 in WCAP-16009-P-A and in WCAP-12945-P-A.

The outer radius of the cladding after burst occurs should be calculated based on the burst strain, and the inner radius of the cladding should be calculated based on, the outer radius. In HOTSPOT, the burst strain is applied to the calculation of the cladding inner radius. The cladding outer radius is then calculated based on the inner radius. As such, the burst strain is incorrectly applied to the inner radius rather than the outer radius, which impacts the resulting cladding geometry at the burst elevation after burst occurs.

Correction of the erroneous calculation results in thinner cladding at the burst node and more fuel relocating into the burst node, leading to an increase in the Peak Cladding Temperature (PCT) at the burst k

node. This issue has been evaluated to estimate the impact on existing Best-Estimate (BE) Large-Brea Loss-of~Coolant Accident (LBLOCA) analysis results. The resolution of this issue represents a Non-Discretionary Change in accordance with Section 4.1.2 ofWCAP-1 3451.

Affected Evaluation Model(s) 1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRUM Estimated Effect fic The issue described above was evaluated based on the results of executing the most limiting plant-speci HOTSPOT runs for similar plants with a HOTSPOT version that includes the correction of this error.

This resulted in an estimated PCT impact of 25°F for Prairie Island Units 1 and 2.

March 17, 2014 Attachment to LTR-LIS-14-98 Page 17 of27 CHANGE S TO GRID BLOCKA GE RATIO AND POROSIT Y Backgroun d A change in the methodology used to calculate grid blockage ratio and porosity for Westinghouse fuel resulted in a change to the grid inputs for large break loss-of-coolant accident (LBLOCA) analyses. Grid inputs affect heat transfer in the core during a LBLOCA. This change represents a Non-Discretionary Change in accordance with Section 4.1.2 ofWCAP-13451.

Mfected Evaluation Model(s) 1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRUM Estimated Effect The updates to the methodology to calculate grid blockage ratio and porosity used as input in Westinghouse LBLOCA models resulted in a negligible change to heat transfer in the core for the fuel type used in Prairie Island Unit 1 and Unit 2. The estimated penalty associated with the changes is 0°F for 10 CPR 50.46 reporting purposes.

March 17,2014 Attachment to LTR-LIS-14-98 Page 18 of27 TY CALCULATION INITIAL FUEL PELLE T AVERAGE TEMP ERATU RE UNCERTAIN Backgr ound UM) Best-Estimate (BE) Large-In the Automated Statistical Treatment of Uncertainty Method (ASTR uncerta inties are applied to the gap Break Loss-of-Coolant Accident (LBLOCA) Evaluation Model (EM),

the uncerta inty in the initial fuel pellet heat transfer coefficient and pellet thermal conductivity to capture to the initial fuel pellet average temperature average temperature. This approach was compared fe conditio ns and found to be conservative in uncertainties predicted by the PAD code at beginning-of-li the initial fuel pellet average tempera ture uncertainty Section 25-4-2-4 of WCAP-12945-P-A. However, M EM is much wider than the uncerta inty range predicted range analyzed at higher burnups in the ASTRU d initial fuel pellet average by the PAD code, which may result in excessively low or high analyze on existing ASTRUM LBLOCA temperatures. This issue has been evaluated to estimate the impact ary Change in accordance with analysis results. The' resolution of this issue represents a Non-Discretion Section 4.1.2 ofWCAP-13451.

Affected Evalua tion Model(s)

ASTRUM 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using Estima ted Effect le effect on existing LBLOCA The issue described above is judged to have either no effect or a negligib impact of0°F.

analysis results, leading to an estimated Peak Cladding Temperature (PCT)

March 17,2014 Attachment to LTR-LIS-14-98 Page 19 of27 SBLOCTA CLADDING STRAIN REQUIREMENT FOR FUEL ROD BURST Background 1 for ZIRL0 cladding in the An error was discovered in the minimum local strain required for burst percent local strain threshold prior SBLOCTA code. The coding does not enforce reaching the minimum s revealed no instances of this to calculating fuel rod burst. However, a review of licensing basis analyse a Non-Discretionary Change to the error impacting calculated results. Resolution of this issue represents Evaluation Model as described in Section 4.1.2 ofWCAP-13451.

Affected Evalua tion Model( s)

MP 1985 Westinghouse Small Break LOCA Evaluation Model with NOTRU Estimated Effect ena and physips of a small break Based on a review of current licensing basis ru;talyses, and the phenom has a negligib le. effect on small break LOCA analysis LOCA transient, it is concluded that this error of 0°F.

results, leading to an estimated Peak Cladding Temperature (PCT) impact LLC, its affiliates and/or its subsidiaries in 1

ZIRLO is a registered trademark of Westinghouse Electric Company s throughout the world. All rights reserved.

the United States of America and may be registered in other countrie rks oftheir respective owners Unauthorized use is strictly prohibited. Other names may be tradema

March 17,2014 Attachment to LTR-LIS-14-98 Page 20 of27 TIME DUE TO.

PRAIRIE ISLAND UNIT 2 EARLI ER CONTAINMENT SPRAY ACTUATION DEGRADED FAN COOLE R HEAT REMOV AL CAPAC ITY Backgro und Island Unit 2, fan coolers During the installation of the replacement steam generators (RSGs) at Prairie of the Prairie Island were damaged, resulting in a degraded heat removal capacity. Due to the design head safety injection (HHSI) emergency core cooling system (ECCS), a complete interruption in high small break loss-of-c oolant accident flows can occur during the switchover to sump recirculation for the uses containm ent pressurization (SBLOCA) transient. The Prairie Island analysis-of-record (AOR) sprays would actuate for the smaller break sizes calculations to determine the time when the containment the time to switch to ECCS sump recircula tion and (1.5-inch and 2-inch breaks). This ultimately dictates d ent pressuri zation calculati ons are impacte d by the degrade therefore the flow interruption. The containm ent spray actuatio n time. This change represen ts a Non-fan coolers and result in an earlier containm P-13451.

Discretionary Change to the Evaluation Model as described at Section 4.1.2 ofWCA Affected Evaluat ion Model(s) 1985 Westinghouse Small BreakL OCA Evaluation Model with NOTRUMP Estimat ed Effect the 1.5-inch and 2-inch When considering the reduced heat transfer capability of the fan coolers for than modeled in the AOR but the interruption in breaks, the containment spray pumps actuate earlier recircula tion still occurs after the 'Core has recovered. There is ECCS flow during the switchover to sump tchover core uncovery sufficient RCS inventory during the flow interruption such that additional, post-swi the Prairie Island Unit 2 would not occur. Therefore, this issue is estimated as a 0°F PCT impact on SBLOCA analysis with the RSGs installed.

March 17, 2014 Attachment to LTR~LIS~l4-98 Page 21 of27 M Best Estimate Large Break Westinghouse LOCA Peak Clad Temper ature Summa ry for ASTRU Plant Name: Prairie Island Unit I Utility Name: Xcel Energy, Inc Revision Date: 2/27/2014 Analysis Informa tion Analysis 11/30/2007 Limiting Break Split EM: ASTRUM FQ: 2.5 FdH: . 1.77 Fuel: 422 Vantage+ SGTP(% ): 10 Notes:

Clad Temp eF) Ref. Notes LICENSING BASIS 1765 1 Analysis~Of~Record PCT PCT ASSESS MENTS (Delta PCT)

A. PRIOR ECCS MODEL ASSESSMENTS 227 2 (a)

I . Evaluation of Fuel Pellet Thennal Conductivity Degradation and Peaking Factor Burn down B. PLANNED PLANT MODIFICATION EVALUATIONS 0 1 . None C. 2013 ECCS MODE L ASSESSMENTS -2 3 I . Revised Heat Transfer Multiplier Distributions 25 4 2 . Error in Burst Strain Application D. OTHER* 0 I . None PCT== 2015 LICENSING BASIS PCT + PCT ASSESSMENTS be considered with respect to

• It is recommended that the licensee detennine ifthese PCT allocations should I 0 CPR 50.46 reporting requirements.

Reference Loss-of-Coolant Accident for the Prairie I . WCAP-16890-P, Revision 1, "Best-Estimate Analysis of the Large-Break Island Nuclear Plant Unit 1 Using ASTRUM Methodology," June 2008.

n and Reporting for Fuel Pellet Thenna\

2 . LTR-LIS-12-414, "Prairie Island Units 1 and 2, 10 CPR 50.46 Notificatio Conductivity Degradation and Peaking Factor Burndown," September 20, 2012.

Report for Revised Heat Transfer 3 . LTR-LIS-13-366, Revision 1, "Prairie Island Units I and 2 10 CFR 50.46 Multiplier Distributions," August 2013.

HOTSPOT Burst Strain Error 4 . LTR-LIS-1~50, "Prairie Island Units I and 2 10 CFR 50.46 Report for the Correction," January 2014.

Notes:

(a) This evaluation credits peaking factor bumdown, see Reference 2.

March 17,2014 Attachment to LTR-LIS-14-98 Page22 of27 Westinghouse LOCA Peak Clad Temperat ure Summary for Appendix K Small Break Plant Name: Prairie Island Unit 1 Utility Name: Xcel Energy, Inc Revision Date: 2/27/2014 Analysis Information Analysis 1/21/2008 Limiting Break 3 inch EM: NOTRUMP FQ: 2.5 FdH: 1.77 Fuel: 422 Vantage+ SGTP (%): 10 Notes: Zirlo (14Xl4), Framatome RSG Clad Temp (OF) Ref. Notes LICENSING BASIS 959 Analysis-Of-Record PCT PCT ASSESSMENTS (Delta PCT)

A. PRIOR ECCS MODEL ASSESSMENTS 0

I . None B. PLANNED PLANT MODIFIC ATION EVALUATIONS 0

I . None C. 2013 ECCS MODEL ASSESSMENTS 0 I . None D. OTHER*

0 I

• None LICENSING BASIS PCT + PCT ASSESSMENTS PCT== 959 to

• It is recommended that the licensee detennine iflhese PCT allocations should be considered with respect I0 CPR 50.46 reporting requirements.

Reference 2008.

I . LTR-LIS-08-158, "Transmittal of Future Prairie Island Units I and 2 PCT Summaries," February Notes:

None

March 17,2014 Attachment to LTR-LIS-14-98 Page 23 of27 Westinghouse LOCA Peak Clad Temperature Summary for ASTRUM Best Estimate Large Break Plant Name: Prairie Island Unit 2 Utility Name: Xcel Energy, Inc Revision Date: 2/27/2014 Analysis Information EM: ASTRUM (2004) Analysis Date: 11130/2007 Limiting Break Size: Split FQ: 2.5 FdH: 1.77 Fuel: 422 Vantage+ SGTP(%): 10 Notes:

Clad Temp (OF) Ref. Notes LICENSING BASIS Analysis-Of-Record PCT 1765 PCT ASSESSMENTS (Delta PCT)

A. PRIOR ECCS MODEL ASSESSMENTS I . Evaluation of Fuel Pellet Thennal Conductivity Degradation and Peaking 227 2 (a), (b)

Factor Bumdown B. PLANNED PLANT MODIFICATION EVALUATIONS I . None 0 C. 2013 ECCS MODEL ASSESSMENTS I . Revised Heat Transfer Multiplier Distributions -2 3 2 . Error in Burst Strain Application 25 4 D. OTHER*

I . None 0 LICENSING BASIS PCT + PCT ASSESSMENTS PCT= 2015

• It is recommended that the licensee detennine ifthese PCT allocations should be considered with respect to I 0 CFR 50.46 reporting requirements.

References I . WCAP-17783-P, "Best-Estimate Analysis of the Large-Break Loss-of-Coolant Accident for Prairie Island Units 1 and 2 with Replacement Steam Generators Using ASTRUM Methodology," June 2013.

2 . LTR-LTS-12-414, "Prairie Island Units I and 2, 10 CFR 50.46 Notification and Reporting for Fuel Pellet Thennal Conductivity Degradation and Peaking Factor Bumdown," September 20, 2012.

3 , LTR-LIS-13-366, Revision 1, "Prairie Island Units I and 2 10 CFR 50.46 Report for Revised Heat Transfer Multiplier Distributions," August 2013.

4 . LTR-LIS-14-50, "Prairie Island Units I and 2 I 0 CFR 50.46 Report for the HOTSPOT Burst Strain Error Correction," January 2014.

Notes:

(a) This evaluation credits peaking factor bumdown, see Reference 2.

(b) The reporting text and line item originally identified for Unit 1 in Reference 2 is applicable to Unit 2 with RSGs.

March 17,2014 Attachment to LTR-LIS-14-98 Page 24 of27 Break Westinghouse LOCA Peale Clad Temperat ure Summary for ASTRUM Best Estimate Large Plant Name: Prairie Island Unit 2 OSG Utility Name: Xcel Energy, Inc Revision Date: 2/27/2014 Analysis Information EM: ASTRUM (2004) Analysis Date: 11/30/2007 Limiting Break Size: Split FQ: 2.5 FdH: 1.77 Fuel: 422 Vantage+ SGTP(%) : 25 Notes:

Clad Temp (DF) Ref. Notes LICENSI NG BASIS 16:L3 Analysis-Of-Record PCT PCT ASSESSMENTS (Delta PCT)

A. PRIOR ECCS MODEL ASSESSMENTS 2 (a)

I . Evaluation of Fuel Pellet Thermal Conductivity Degradation and Peaking 340 Factor Bumdown B. PLANNED PLANT MODIFIC ATION EVALUATIONS I . None 0

C. 2013 ECCS MODEL ASSESSMENTS -16 3 I . Revised Heat Transfer Multiplier Distributions D. OTHER*

I

• None 0 LICENSI NG BASIS PCT + PCT ASSESSMENTS PCT= 1947

• It is recommended that the licensee determine if these PCT allocations should be considered with respect to 10 CFR 50.46 reporting requirements.

References Prairie Island Nuclear Plant I . WCAP-16891-P, "Best-Estimate Analysis of the Large-Break Loss-of-Coolant Accident for the Unit 2 Using ASTRUM Methodology," June 2008.

Fuel Pellet Thermal 2 . LTR-LIS-12-414, "Prairie Island Units I and 2, 10 CPR 50.46 Notification and Reporting for Conductivity Degradation and Peaking Factor Bumdown," September 20, 2012.

Transfer Multiplier 3 . LTR-LIS-13-366, Revision I, "Prairie Island Units I and 2 10 CFR50.46 Report for Revised Heat Distributions," August 2013.

Notes:

(a) This ~valuation credits peaking factor bumdown, see Reference 2.

Attachment to LTR-LIS-14-98 March 17,2014 Page 25 of27 Westinghouse LOCA Peak Clad Temperature Summary for Appendix K Small Break Plant Name: Prairie Island Unit 2 Utility Name: Xcel Energy, Inc Revision Date: 2/27/2014 Analysis Information EM: NOTRUMP Analysis Date: 1/21/2008 Limiting Break Size: 3 inch FQ: 2.5 FdH: 1.77 Fuel: 422 Vantage+ SGTP (%): 10 Notes: Zirlo (14Xl4), ARE.VA RSG Clad Temp (DF) Ref. Notes LICENSING BASIS Analysis-Of~Record PCT 959 1, 2 a PCT ASSESSMENTS (Delta PCT)

A. PRIOR ECCS MODEL ASSESSMENTS 1 . None 0 B. PLANNED PLANT MODIFICATIO N EVALUATIONS 1

• None 0 C. 2013 ECCS MODEL ASSESSMENTS I

• None 0 D. OTHER*

I . None 0 LICENSING BASIS PCT + PCT ASSESSMENTS PCT= 959

• It is recommended that the licensee detennine if these PCT allocations should be considered with respect to I 0 CFR 50.46 reporting requirements.

References I , LTR-LIS-08-158, "Transmittal of Future Prairie Island Units 1 and 2 PCT Summaries," February 2008.

2 . LTR-LIS-13-274, "Prairie Island Units I and 2, 10 CFR 50.46 Summary Sheets for the Evaluation to Support the Unit 2 Installation of AREVA Model 56/19 Replacement Steam Gen~rators (RSGs)," June 2013.

Notes:

(a) The Unit I AOR is applicable to Unit 2 with the RSGs installed.

Attachment to LTR~LIS~14~98 March 17,2014 Page 26 of27 Westinghouse LOCA Peak Clad Temperature Summary for Appendix K Small Break Plant Name: Prairie Island Unit 2 OSG Utility Name: Xcel Energy, Inc Revision Date: 2/27/2014 Analysis Information EM: NOTRUMP Analysis Date: 1/21/2008 Limiting Break Size: 2 inch FQ: 2.5 FdH: 1.77 Fuel: 422 Vantage+ . SGTP(%): 25 Notes: Zirlo (14X14)

Clad Temp (DF) Ref. Notes LICENSING BASIS Analysis~Of~Record PCT 965 1 PCT ASSESSMENTS (Delta PCT)

A. PRIOR ECCS MODEL ASSESSMENTS 1 . None 0 B. PLANNED PLANT MODIFICATION EVALUATIONS 1 . None 0 C. 2013 ECCS MODEL ASSESSMENTS 1 .None 0 D. OTHER*

1 . None 0 LICENSING BASIS PCT + PCT ASSESSMENTS PCT= 965

• It is recommended that the licensee detennine ifthese PCT allocations should be considered with respect to 10 CFR 50.46 reporting requirements.

References I

• LTR-LIS-08-158, "Trnnsmittal ofFuture Prairie Island Units 1 and 2 PCT Summaries," February 2008.

Notes:

None

Attachment to LTR-LIS-14~98 March 17,2014 Page27 of27 10 CFR 50.46 Reporting SharePoint Site Check:

EMs applicable to Prairie Island:

Realistic Large Break- ASTRUM (2004)

Appendix K Small Break- NOTRUMP 2013 Issues Transmittal Letter Issue Description LTR-LIS-13-219 10 CFR 50.46 Report for the Initial Fuel Pellet Average Temp.

Uncert. Calculation LTR-LIS-13-346 10 CFR 50.46 Notification and Reporting for WCOBRA-TRAC Changes and Error Corrections LTR-LIS-13-366, Prairie Island Units 1 and 2 10 CFR 50.46 Report for Revised Rev.1 Heat Transfer Multiplier Distributions LTR-LIS-14-50 Prairie Island Units 1 and 2 10 CFR 50.46 Report for the HOTSPOT Burst Strain Error Correction LTR-LIS-13-274 Prairie Island Units 1 and 2 10 CFR 50.46 Summary Sheets for the Evaluation to Support the Unit 2 Installation of AREVA Model56/19 Replacement Steam Generators (RSGs)