ML14167A431

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ANP-3243NP, Rev. 1, Seabrook Station, Unit 1, Fixed Incore Detector System Analysis Supplement to YAEC-1855PA, Licensing Report.
ML14167A431
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Site: Seabrook NextEra Energy icon.png
Issue date: 05/31/2014
From:
AREVA
To:
Office of Nuclear Reactor Regulation
References
LAR 13-05, SBK-L-14090 ANP-3243NP, Rev. 1
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{{#Wiki_filter:AAREVASeabrook Station Unit I Fixed IncoreDetector System Analysis Supplement to YAEC-1 855PAANP-3243NP Revision 1Licensing ReportMay 2014AREVA Inc.(c) 2014 AREVA Inc. Copyright © 2014AREVA Inc.All Rights Reserved AREVA Inc.ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensinq Report Paqe iNature of ChangesSection(s) Item or Page(s) Description and Justification 1 Abstract Discuss new uncertainty analysisSection 1.1Section 5.3Section 6.2Section 7.0Appendix B AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensinq Report Page iiContentsPaqe1.0 TECHNICAL EVALULATIO N ................................................................................ 11.1 Background ............................................................................................. 12.0 NEUTRO N CO NVERSIO N FACTO R .............................................................. 42.1 Current Licensing Basis .......................................................................... 42.2 Proposed M ethod ................................................................................. 63.0 REPLACEM ENT DETECTO RS ........................................................................ 83.1 General ................................................................................................... 83.2 Current Licensing Basis .......................................................................... 93.3 Proposed M odification ........................................................................... 94.0 DEPLETIO N CO RRECTIO N FACTO R .......................................................... 114.1 Current Licensing Basis ....................................................................... 114.2 Proposed M odification ......................................................................... 115.0 CO M PARISO N O F FINC RESULTS ............................................................... 125.1 General ................................................................................................. 125.2 Surveillance Param eter Com parisons ................................................... 125.3 Statistical Results ............................................................................... 266.0 UNCERTAINTY ANALYSIS ............................................................................ 276.1 Current Licensing Basis ....................................................................... 276.2 Proposed Uncertainty M odifications .................................................... 306.2.1 Overview .................................................................................... 306.2.2 M ethodology ............................................................................. 316.2.3 Uncertainty Calculation Details .................................................. 366.2.4 Uncertainty Calculation Results ................................................ 386.2.5 Analysis of Significant Trends .................................................. 427.0 CO NCLUSIO NS ............................................................................................ 4

68.0 REFERENCES

............................................................................................... 47APPENDIX A ................................................................................................................. 48APPENDIX B ................................................................................................................. 71 AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensinq Report Page iiiList of TablesTable 1 Uncertainty Components and Confidence Multipliers from YAEC-18 5 5 P A .................................................. .......................................... ..2 9Table 2 95/95 Uncertainty Limits for FAH and FQ ............................ .......................... 43Table B-1 Conservative Trend Slope of FAH UL(95/95) and FQ UL(95/95) for aMaximum of 8 Failed Detector Strings .................................................. 75 AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page ivList of FiguresFigure 1 Comparison of Heat Flux Hot Channel Factor FQ for Cycle 1 .................... 14Figure 2 Comparison of Heat Flux Hot Channel Factor FQ for Cycle 2 .................... 14Figure 3 Comparison of Heat Flux Hot Channel Factor FQ for Cycle 3 .................... 15Figure 4 Comparison of Heat Flux Hot Channel Factor FQ for Cycle 4 .................... 15Figure 5 Comparison of Heat Flux Hot Channel Factor FQ for Cycle 5 .................... 16Figure 6 Comparison of Heat Flux Hot Channel Factor FQ for Cycle 6 .................... 16Figure 7 Comparison of Heat Flux Hot Channel Factor FQ for Cycle 7 .................... 17Figure 8 Comparison of Heat Flux Hot Channel Factor FQ for Cycle 8 .................... 17Figure 9 Comparison of Enthalpy Rise Hot Channel Factor FAH for Cycle 1 ........ 18Figure 10 Comparison of Enthalpy Rise Hot Channel Factor FAH for Cycle 2 ....... 18Figure 11 Comparison of Enthalpy Rise Hot Channel Factor FAH for Cycle 3 ....... 19Figure 12 Comparison of Enthalpy Rise Hot Channel Factor FAH for Cycle 4 ....... 19Figure 13 Comparison of Enthalpy Rise Hot Channel Factor FAH for Cycle 5 .......... 20Figure 14 Comparison of Enthalpy Rise Hot Channel Factor FAH for Cycle 6 .......... 20Figure 15 Comparison of Enthalpy Rise Hot Channel Factor FAH for Cycle 7 .......... 21Figure 16 Comparison of Enthalpy Rise Hot Channel Factor FAH for Cycle 8 .......... 21Figure 17 Comparison of Axial Offset for Cycle 1 ................................................... 22Figure 18 Comparison of Axial Offset for Cycle 2 ................................................... 22Figure 19 Comparison of Axial Offset for Cycle 3 ................................................... 23Figure 20 Comparison of Axial Offset for Cycle 4 ................................................... 23Figure 21 Comparison of Axial Offset for Cycle 5 ................................................... 24Figure 22 Comparison of Axial Offset for Cycle 6 ................................................... 24Figure 23 Comparison of Axial Offset for Cycle 7 ................................................... 25Figure 24 Comparison of Axial Offset for Cycle 8 ................................................... 25Figure 25 Flow Diagram of Calculations .................................................................. 35Figure 26 FAH UL(95/95) Plots for Cycle 14, FAH Near Maximum ........................... 44Figure 27 FQ UL(95/95) Plots for Cycle 14, FAH Near Maximum ............................. 45Figure A-1 Measured Signal Divided by Detector Power versus DetectorExposure, O riginal Detectors ............................................................... 55Figure A-2 Measured Signal Divided by Detector Power versus DetectorExposure, Replacement Detectors ...................................................... 56 AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page vFigure A-3 Calculated Gamma Signal Divided by Detector Power versusDetector

Exposure, Original Detectors

................................................ 57Figure A-4 Calculated Gamma Signal Divided by Detector Power versusDetector

Exposure, Replacement Detectors

........................................ 58Figure A-5 Inferred Neutron Signal Divided by Detector Power versus DetectorExposure, O riginal Detectors ............................................................... 59Figure A-6 Inferred Neutron Signal Divided by Detector Power versus DetectorExposure, Replacement Detectors ...................................................... 60Figure A-7 Neutron Conversion Factor versus Detector

Exposure, OriginalD e te cto rs ...........................................................................................

..6 1Figure A-8 Neutron Conversion Factor versus Detector

Exposure, Replacement D e te cto rs ...........................................................................................

..6 2Figure A-9 Calculated Gamma Divided by Measured Signal versus DetectorExposure, O riginal Detectors ............................................................... 63Figure A-10 Calculated Gamma Divided by Measured Signal versus DetectorExposure, Replacement Detectors ...................................................... 64Figure A-1 1 Depletion Correction Factor .................................................................. 65Figure A-12 Difference between Predicted and Measured

Signals, OriginalDetectors, Proposed M odel .................................................................

66Figure A-13 Difference between Predicted and Measured

Signals, Replacement Detectors, Proposed M odel .................................................................

67Figure A-14 Ratio of Measured Signals for Original to Replacement Detectors, B atch 1, C ycle 14 .............................................................................. ..68Figure A-15 Ratio of Measured Signals for Original to Replacement Detectors, B atch 1, C ycle 15 .............................................................................. ..69Figure A-16 Ratio of Measured Signals for Original to Replacement Detectors, B atch 2 , C ycle 15 .............................................................................. ..70Figure B-1 Example Linear Least Square Fits of FAH (UL 95/95) and FQ (UL 95/95) ........ 76 AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensina Reoort Paae viNomenclature (If applicable) AcronymFAHFdhFQFIDSNCFGCFDPCSTSGSMCyOThlOTh avgRnCnCdERMS2D3DOaObOcOdOtOrkDefinition Enthalpy rise hot channel factorSame as FAH; nomenclature used in YAEC-1855PA Heat flux hot channel factorFixed Incore Detector SystemNeutron Conversion FactorGamma Correction FactorDepletion Correction FactorTotal calculated detector signalCalculated detector signal due to gammaMeasured signalUnit conversion factor for calculated detector gamma signalThermal neutron fluxAverage thermal neutron fluxNeutron reaction rate for Pt-1 95Same as NCFCoefficient of DPC versus detector exposureDetector exposureRoot Mean SquareTwo-dimensional Three-dimensional Standard deviation for signal reproducibility Standard deviation for analytical methodsStandard deviation for axial power shapeStandard deviation for detector processing Standard deviation for integral detector processing Standard deviation for total system (3D)Standard deviation for integral processing (2D)Confidence interval multiplier AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensinq Report Paqe viiABSTRACTThis document provides modifications to the Fixed Incore Detector System (FIDS)Analysis methodology described in YAEC-1855PA. The FIDS Analysis methodology has been in use at Seabrook Station to monitor core power distribution surveillance parameters since Cycle 5 in 1995. The FIDS uses fixed platinum detectors which arepredominantly gamma sensitive and have a contribution from neutron capture. TheFIDS has operated successfully for over 20 years of operation. In 2007, Seabrookundertook a phased detector replacement project. The Seabrook specification forreplacement detectors was written to produce a like-for-like replacement of the originaldetectors.

However, changes in manufacturing techniques required changes to theFIDS Analysis methodology to incorporate correction factors to normalize thereplacement and the original detector signals to the standard detector performance required by the analysis methodology.

Two replacement detector strings were installed in Cycle 14 and three detector strings were installed in Cycle 15. During Cycle 16,Seabrook undertook a program to trend detector performance over the 15 cycles ofoperation to determine appropriate modifications to the Fixed Incore Detector Code(FINC).Based on the trending

analysis, revisions were made to the FIDS Analysismethodology.

The modifications include a more precise method to determine thedetector neutron conversion factor to better predict the neutron portion of the fixeddetector signal based on the predicted neutron reaction rate. Modifications were alsomade to track detector exposure and to make a depletion correction to the measuredsignal based on the detector exposure. To normalize the replacement and originaldetectors, correction factors were quantified and incorporated as a multiplier on themeasured signal of the replacement detectors. The FINC code was modified to incorporate the revised FIDS Analysis methodology andthe proposed modifications were used to rerun all 15 cycles of flux maps. AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensingq Report Page viiiThe measurement of a core power distribution is built upon a series of comparisons between measured incore signals and predicted incore signals in instrumented locations of the core, and expansion of the resultant power distribution data to uninstrumented locations. In YAEC-1855PA the uncertainty for detector processing is calculated bycomparing detector signals measured at various core conditions to predictions of thedetector signals at these same core conditions. While the FIDS uncertainty based onthe difference between measured and predicted detector signals is conservatively

bounding, it is not a good representation of the true measurement uncertainty.

TheYAEC-1855PA uncertainty analysis is replaced by a method that propagates theuncertainties through the FIDS analysis system using a Monte Carlo statistical simulation and determines a better representation of the true measurement uncertainty for FQ and FAH over a wide range of conditions. This uncertainty analysis methodology is similar to that employed by the Reference 5 and 6 core power distribution monitoring systems previously reviewed and approved by the NRC.This report describes the detector performance trending analysis of the 15 cycles,documents the proposed modifications to the FIDS Analysis methodology and providesa new determination of the resulting measurement uncertainty for the FQ and FAHTechnical Specifications (Tech Specs) surveillance parameters. AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Paqie 11.0 TECHNICAL EVALULATION

1.1 Background

Seabrook Station started Cycle 1 with a combination fixed/movable detector system in58 locations within the reactor core. The Detector Assemblies at that timeaccommodated the movable incore detector path, the qualified core exit thermocouple, and the five fixed platinum incore detectors. The movable detector system was usedduring the first four cycles of operation and was also used to benchmark the fixedplatinum incore detectors. The fixed detector system was licensed by the NRC duringCycle 3 using the methodology described in YAEC-1855PA (Reference 1). The fixedplatinum incore detectors and the methodology described in YAEC-1855PA have beenused exclusively to monitor the core since Cycle 5.YAEC-1855PA describes the methodology and uncertainty analysis used to determine the measured core power distribution using the fixed incore detectors and theassociated uncertainty. The fixed incore detectors are self-powered platinum detectors which are predominantly gamma sensitive and produce a signal proportional to the localgamma flux in the reactor core. Although the majority of the signal from the platinumdetectors is derived from the gamma flux, a portion of the signal is due to the neutronflux from an n,y reaction. There are 58 incore detector assemblies distributed radiallythroughout the core. Each assembly contains 5 individual fixed incore detectors uniformly spaced axially along the height of the core. Thus, a total of 290 detectors areproviding continuous core power distribution information. The detector signals arescanned once per minute and stored such that they may be retrieved and analyzed todetermine the three dimensional power distribution and associated Tech Specsurveillance parameters. The computer software package used to analyze the fixedincore detector signals to determine the power distribution parameters is referred to asS3FINC and is described in YAEC-1855PA. AREVA Inc. ANP-3243NP Revision 1.Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 2S3FINC has two major components. The first is the predictive codes CASMO-3(Reference

2) for cross section generation and gamma response and SIMULATE-3 (Reference
3) for predicting the core power distribution and individual detectorresponses.

The second is the Fixed Incore Detector Code (FINC) which uses theSIMULATE-3 output and measured fixed incore detector signals to determine themeasured core power distribution. Included in YAEC-1855PA is a discussion on how the detector signals are treated asinputs to the methodology. Important points to note from YAEC-1855PA are:* The use of the CASMO-3/SIMULATE-3 for power distribution prediction

  • The use of a standard detector approach for power distribution analysis* The assumption that 25% of the signal is due to neutrons* The overall uncertainty analysis for use with Tech Specs surveillance of FQ and FAH.Although not specifically addressed in YAEC-1855PA, detectors need to be replaceddue to long term wear on the high pressure seals and signal connectors.

To this extent,Seabrook has a prototype Replacement Project to replace Detector Assemblies startingwith the OR13 (Cycle 14) refueling outage. Two detectors were replaced during OR13and three were replaced during OR14 (Cycle 15). Seabrook has also embarked on aprogram to analyze data from the first 15 cycles of operation to quantify trends in thedetector performance data and to validate the uncertainty analysis presented in YAEC-1855PA. This topical report serves as a supplement to YAEC-1 855PA. The changesproposed are:* An improved prediction of the neutron component of the detector signal -NeutronConversion Factor (NCF),* Applying correction factors to the measured detector signal of the replacement detectors to better assure normalization to a standard detector performance -Gamma Correction Factor (GCF), AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 3* Accounting and correcting the measured detector signal for detector depletion tobetter assure normalization to a standard detector performance -Depletion Correction (DPC), and* Replacing the uncertainty analysis with a new analysis that better represents thetrue measurement uncertainty for FQ and FAH over a wide range of conditions bypropagating the uncertainties through the FIDS analysis system using a Monte Carlostatistical simulation method. AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 42.0 NEUTRON CONVERSION FACTOR2.1 Current Licensing BasisThe signal from a platinum fixed incore detector is predominantly from gammainteraction with the platinum. A portion of the detector signal is from neutron interaction with the platinum, predominantly the Pt-1 95 isotope. It was recognized in both thetopical report YAEC-1855PA and in the associated NRC SER dated 12/23/1993 that thefraction of the total detector signal due to neutrons is approximate and not well known atthe time. Section 3 of YAEC-1855PA describes the assumptions used to determine anestimate for the fraction of total detector signal due to neutrons. At that time, publicdomain studies and a Seabrook specific sensitivity study based on operational datawere used to determine the estimate of the fraction neutron component to be used asan input assumption in determining the predicted detector signal. Based on theliterature and the sensitivity study, a value of 25% of the total signal was attributed toneutrons. To accommodate the platinum detectors, SIMULATE-3 was modified, to allow the userto input the fractional neutron component of the predicted detector signal. This fractionis given in terms of the total detector signal, and it can be distributed by either or boththe fast and thermal neutron flux. The gamma portion of the detector's signal isdetermined through the total responses determined in CASMO-3 cases and localdetector neutron flux calculations within SIMULATE-3. This is the standard method ofdetector calculations used within SIMULATE-3. The total neutron portion of detectorsignal is determined from the input fraction and is then distributed by the SIMULATE-3 calculated relative local thermal neutron flux levels at the detector locations. Theindividual detector's gamma and neutron portions are then summed to determine thedetector's total signal.As described in YAEC-1 855PA, a value of 0.25 was used for the thermal neutroncomponent of the predicted detector signal. Thus the total gamma signal wascalculated in SIMULATE-3 as: AREVA Inc. ANP-3243NP Revision ISeabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 5The above value of ST was used in FINC starting in Cycle 1. AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 62.2 Proposed MethodTo better cover a broader range of reactor core design and operating conditions, a newformulation for determining the neutron component of the predicted detector signal wasdeveloped. Rather than use the straight 25% of the gamma signal to represent theneutron portion, it was determined that a more accurate representation of the totalsignal could be accomplished by adding a neutron portion to the gamma signal basedon total neutron reaction rate. To do this, a new factor called the Neutron Conversion Factor (NCF) was introduced. The new formulation using the neutron conversion factoris shown in Equation

2.

AREVA Inc. AISeabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensina ReDortNP-3243NP Revision 1Paae 7I AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 83.0 REPLACEMENT DETECTORS 3.1 GeneralThe Seabrook specification for replacement detectors was written to produce a like-for-like replacement of the original detectors. The replacement detectors were built to theoriginal specification and within the as-built attributes of the original detectors including detector

geometry, dielectric densities and component material impurities.

Thereplacement detectors were also constrained to the characteristics assumed in theanalysis software licensed for the system. These precautions served to preserve thelike-for-like nature of the replacement detectors to the original detector. Nonetheless, the manufacturing enhancements developed in more than 20 years of detector serviceresult in differences in detector performance as observed in gamma testing of thereplacement detectors and archive original detectors. AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 93.2 Current Licensing BasisAs described in YAEC-1855PA, the FINC code depends on the concept of a standarddetector. In the standard detector

approach, the raw measured detector signals mustbe corrected for individual detector differences.

The signal from any individual detectoris a function of the incident flux, the amount of detector material and manufacturing differences. Thus, each detector's signal must be modified to correspond to a signalgiven by a standard detector. The standard detector is one built to exact designdimensions. Since Cycle 1, each measured detector signal is corrected by a sensitivity factor. The sensitivity factor is defined as the ratio of the detector surface area to thesurface area of a standard detector. The data required for the calculation of thesensitivity factors is provided by the detector manufacturer's as-built data of detectorlength and weight. The sensitivity factors for the replacement detectors were calculated in the same manner as the original detectors in Cycle 1 using the as-built length andweight. This feature in the current licensing basis has not changed. The sensitivity factor is applied to the measured signal and is used to create a standard detector byusing the manufacturer's measured weight and length for each detector compared tothe weight and length of a standard detector. 3.3 Proposed Modification The replacement detector specification required that each individual replacement detector is tested for operation using a gamma source. In addition, to verifycompatibility, original archive detectors are tested in the same gamma sourceenvironment. During the testing, it was noted that the replacement detectors produceda lower signal than the original detectors in the same gamma field and could not becorrected by application of the simple sensitivity factor based only on as-built detectorlength and weight. AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 10The Gamma Correction Factor (GCF) was introduced in Cycle 14 to make thereplacement detector signal compatible with the signal from the original detectors. TheGCF is input to FINC as a simple multiplier on the measured signal for the replacement detectors. Different values of the GCF are used for the Batch 1 and Batch 2replacement detectors based on changes in the manufacturing process. As part of thetrending

analysis, the GCF was refined through the trending analysis of Appendix A asshown in Figure A-14, Figure A-15, and Figure A-16. The trending analysis comparedthe difference in signal between the replacement detectors and their symmetric partnersover Cycles 14 and 15 for the Batch 1 replacement detectors and over Cycle 15 for theBatch 2 replacement detectors.

The GCF values reflect in-reactor measurements ofsymmetric partners in the Seabrook reactor environment. The value of Batch 1 GCF is1.0577 and the Batch 2 GCF is 1.0849. The Batch 2 replacement detectors defined thefuture manufacturing process. It is the intent to use the Batch 2 GCF for future batchesof replacement detectors.

However, since the magnitude of the detector signal can beaffected by the manufacturing
process, future batches of detectors may require theirown GCF determined through testing.

AREVA Inc. AM'Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensino RenortJP-3243NP Revision 1Paae 11Licensina Renort4.04.1DEPLETION CORRECTION FACTORCurrent Licensing BasisThe current licensing basis does not include a depletion correction factor. The modelingof the effects of elemental platinum depletion is not required as described in YAEC-1855PA in response to RAI Question

4. [] Thus, no provisions were provided inthe current licensing basis for a depletion correction.

4.2Proposed Modification ] This effect is primarily due tothe consumption of the Pt-195 isotope which is the predominant contributor to theneutron component of the total gamma signal of the detector. From the trending analysis covering all 15 cycles, a linear Depletion Correction (DPC)was derived in Appendix A as a function of detector exposure as shown in Figure A-1 1.Detector exposure is the accumulated fuel exposure of the assembly containing thedetector, averaged over the detector length. With the proposed modification of FINC,the DPC will be calculated for each detector based on detector exposures using thederived curve. The DPC will be applied to each individual detector and will vary withdetector exposure. [From Equation 3, the depletion correction factor utilizes the detector exposure to obtaina multiplier to be applied to the measured signal for each detector. AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PALicensing Report Page 125.0 COMPARISON OF FINC RESULTS5.1 GeneralWith the completion of the trending analysis in Appendix A, the proposed modifications to FINC were established. To determine the effect of these modifications on thesurveillance parameters, all 15 cycles of flux maps were rerun with the revised versionof FINC incorporating the proposed modifications. The 15 cycles provides a good testof the proposed modifications to FINC under an array of operating conditions thatinvolved changes in fuel management

strategy, changes in fuel design, power uprate,normal core tilt condition and axial offset anomalies.

The evaluation of the data is forflux maps that were run under equilibrium conditions as would be the case for normalsurveillance. 5.2 Surveillance Parameter Comparisons This section shows the comparison of the original FINC version to the modified FINCversion for the Tech Spec surveillance parameters. Although all 15 cycles of flux mapswere rerun with the modified version of FINC, comparisons are provided here for thefirst eight cycles. During these cycles the licensing model used a fixed 25% of thegamma signal as the neutron portion of the signal and did not include a correction fordetector exposure. The proposed modifications to FINC utilize a neutron conversion factor and the neutron reaction rate to determine the neutron portion of the signal. Theproposed model also includes a correction for depletion based on the exposure of eachindividual detector. The comparisons for the heat flux hot channel factor FQ areprovided in Figure 1 through Figure 8. The value of FQ includes the currentmeasurement uncertainty of 5.21% and the engineering heat flux uncertainty of 3%.The comparisons for the enthalpy rise hot channel factor FAH are provided in Figure 9through Figure 16 and the comparisons for axial offset are provided in Figure 17through Figure 24. FAH values are shown without any uncertainty because theuncertainty factor is applied to the limit, as specified in the core operating limits report. AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 13The results provided in Figure 1 through Figure 24 show that performance of theproposed model compares well to the current licensing basis model. In these figuresthe proposed model contains the neutron conversion factor, detector exposure trackingand the depletion correction. The NCF was introduced in Cycle 9 in 2002 so that acomparison to the original FINC version, consistent with the current licensing basismethodology could not be made after Cycle 8. AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PALicensinq Report Paqie 14Figure 1 Comparison of Heat Flux Hot Channel Factor FQ for Cycle 12.20 -2.00 11.80 -0E1.60. -1.40 -1.20 -*Licensing Model OProposed Model1.00 -0 2000 4000 6000 8000 10000 12000 14D00Cyde Exposure (MWD/MTU) Figure 2 Comparison of Heat Flux Hot Channel Factor FQ for Cycle 21.951.90 -1.85EE: 1.80 [] 01.75 -001.75 -01.70* Licensing Model O Proposed Model1.650 2000 4000 6000 8000 10000 12000Cyde Exposure (MWD/MTU) AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensina ReDort Paae 15Figure 3 Comparison of Heat Flux Hot Channel Factor FQ for Cycle 32.001.95001.90E 0E1.851.80 -+1.75 -0* Licensing Model OProposed Model1.70 1 1..0 2000 4000 6000 8000 10000 12000 14000 16000Cyde Exposure (MWD/MTU) Figure 4 Comparison of Heat Flux Hot Channel Factor FQ for Cycle 41.901.851.80E 1.751.701.651.601.55VPOD1000*Licensing Model OProposed Model0500010000Cyde Exposure (MWD/MTU) 1500020000 AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PALicensing Report Page 16Figure 5 Comparison of Heat Flux Hot Channel Factor FQ for Cycle 52.00 ,1.95 ___---__0___-__ _1.90 [ 113 t 01.85 I=0X 180 -1.75o1.70 -* Licensing Model 0Proposed Model1.65 1 T0 5000 10000 15000 200D0Cyde Exposure (MWD/MIU) Figure 6 Comparison of Heat Flux Hot Channel Factor FQ for Cycle 62.05.2.001.95S1.90.X 1.851.80*Licensing Model OProposed Model1.70 1 1 10 5000 10000 15000 20000 25000Cyde Exposure (MWD/MTU) AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensinq Report Page 17Figure 7 Comparison of Heat Flux Hot Channel Factor FQ for Cycle 71.901.85E1.701.651 Licensing Model -0 Proposed Model1.60 ,,,0 5000 10000 15000 20D00Cycle Exposure (MWD/MTU) Figure 8 Comparison of Heat Flux Hot Channel Factor FQ for Cycle 81.901.881.861.84EE 1.801.781.761.741.721.70200000 5000 100O0 15000Cycle Exposure (MWD/MTU) AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensinq Report Page 18Figure 9 Comparison of Enthalpy Rise Hot Channel Factor FAH forCycle I1.401.381.361.3413E1.3291.301.281.261.24p0*0 0* Licensing Model 0'Proposed Model0 2000 4000 6000 8000 10000Cyde Exposure (MWD/MTU) 12000 14000Figure 10 Comparison of Enthalpy Rise Hot Channel Factor FAH forCycle 21.46[0 D1.441.42 -= 1.401.381.36#Licensing Model r-Proposed Model1.34 -I0 5000 10000 150D0 20000Cyde Exposure (MWD/MTU) AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 19Figure 11 Comparison of Enthalpy Rise Hot Channel Factor FAH forCycle 31.46+0 0 001.45 0 00*E_E1.431.42 -1.41*Licensing Model OProposed Model1.40 .......0 2000 4000 6000 8000 10000 12000 14000 16000Cyde Exposure (MWD/MTU) Figure 12 Comparison of Enthalpy Rise Hot Channel Factor FAH forCycle 41.46n n1.44i*1.421.401.381.36*Licensing Model OProposed Model I1.34 -I0 5000 10000 15000 20000Cyde Exposure (MWD/MTU) AREVA Inc. ASeabrook Station Unit 1 Fixed I ncore Detector.System Analysis Supplement to YAEC-1855PA Licensino Renort4P-3243NP Revision 1Paae 20Figure 13 Comparison of Enthalpy Rise Hot Channel Factor FAH forCycle 51.491.481.471.46U' 1.45_E1.441.43on r0p*Licensing Model n Proposed Model1.421.411.400500010000Cycle Exposure (MWD/MTU) 1500020000Figure 14Comparison of Enthalpy Rise Hot Channel Factor FAH forCycle 61.561.541.52 A 171E 5x 1.481.46- i_1.44 ,1.42 Licensing Model OProposed Model0 5000 10000 15000 20000 25000Clyde Exposure (MWD/MTU) AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 21Figure 15 Comparison of Enthalpy Rise Hot Channel Factor FAH forCycle 71.451.441.431.42E 1.41E OS1.401.391.381.371.360500010000 15000 2000OCyde Exposure (MWD/MTU) Figure 16 Comparison of Enthalpy Rise Hot Channel Factor FAH forCycle 81.441441.431.431E1.42~ 001.40 -1.39 -1.9 #Licensing Mode 1 0Proposed ModelI0 5000 10000 15000 20000Cycle Exposure (MWD/MTU) AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 22Figure 17 Comparison of Axial Offset for Cycle 10.0-1.0-2.0--3.0Z -4.0950-6.0-7.0-8.0-9.0O [.* 00*0 00*Licensing Model OProposed Model2000i 100 120 400200D4000 6000 8000CYde Exposure (MWD/MTU) 10000120D0 140006.05.04.03.02.01.00.0-1.0-2.0-3.0-4.0Figure 18 Comparison of Axial Offset for Cycle 20.,0 [0 *0 P

  • de*Licensing Model OProposed Model020004000 6000 8000Cycle Exposure (MWD/MT1) 1000012000 AREVA Inc. AI,Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA L icensina RenortJP-3243NP Revision 1Paae 23Figure 19 Comparison of Axial Offset for Cycle 30.0--0.5-1.0- 13..0_9-2.0- A-+q S0 *-3.0 B-0-3.5-Licensing Model 0 Proposed Model-4.0-0 2000 4000 6000 8000 10000 12000 14000 16000Cyde Exposure (MWD/MTU) 1-461.441.42E_E 1.401.38Figure 20 Comparison of Axial Offset for Cycle 40* *0 00 +#* Licensing Model OProposed Model I 1*1.361.340500010000Cyde Exposure (MWD/MTU) 1500020000 AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit I Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensinq Report Page 24Figure 21 Comparison of Axial Offset for Cycle 532.01.00.0-1.0-2.0-3.0-4.0-5.0-6.0*Licensing Model 0 Proposed Model "0--~J-5 0w 0~ ,d0[ED .*+ ,, n o O0500010000Cyde Exposure (MWD/MTU) 15000200004.03.02.01.00.0-1.0-2.0.2.1Figure 22 Comparison of Axial Offset for Cycle 64,,5A.- FII I ~cen~ng odi ropoedM~iA

-3.0-4.0-5.0-6.00500010000150002000025000Cyde Exposure (MWD/MTU) AREVA Inc. AI'Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensina Report4P-3243NP Revision 1Paoe 25Figure 23 Comparison of Axial Offset for Cycle 74.0 -3.0-2.0-1.0 *Licensing Model 0 Proposed Model +0-3.0-4.0-5.00 5000 10000 15000 20000Cyde Exposure (MWO/MTU) Figure 24 Comparison of Axial Offset for Cycle 80.0-0.5-1.01. 5.5I -2.0-2.5-3.0-3.5-4.005000 10000 15000Cyde Exposure (MWD/MnU) 20000 AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PALicensinq Report Paqe 265.3 Statistical ResultsWith the proposed modifications, a new uncertainty analysis was performed that betterrepresents the true measurement uncertainty for FQ and FAH over a wide range ofconditions by propagating the uncertainties through the FIDS analysis system using aMonte Carlo statistical simulation method. This statistical simulation method replacesthe signal reproducibility and detector processing uncertainty terms in the YAEC-1855PA uncertainty analysis. [] Theresults of the simulation analysis were statistically combined with the Analytical Methodsand Axial Signal Power Shape uncertainty terms from YAEC-1855PA, which remainedunchanged, and determined a total measurement uncertainty of the FIDS analysissystem of less than 4.0% for FAH and less than 5% for FQ.The accuracy and functionality of the FIDS analysis system remains comparable to theoriginal YAEC-1855PA analysis and the Moveable Incore Detector System. AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 276.0 UNCERTAINTY ANALYSIS6.1 Current Licensing BasisAs noted in YAEC-1 855PA, the uncertainty of the fixed incore detector system isaddressed in four individual parts. Each of these parts are quantified and thenstatistically combined to achieve a total system uncertainty at a 95/95 confidence levelwith a one-sided tolerance limit. The uncertainties associated with FAH and FQ havetraditionally been treated independently. The uncertainty in the three-dimensional parameter FQ contains all axial and radial components of the system uncertainty.

However, the two-dimensional parameter FAH is an axially integrated quantity that doesnot contain the axial uncertainty component.

Uncertainties for each of these quantities are defined independently below.The total system uncertainty applied to the three-dimensional quantity of FQ defined as: AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 28The second uncertainty factor is applied to the two-dimensional axially integrated quantity of FAH. The radial or FAH uncertainty requires the combination of three of thefour uncertainty components. The axial power shape uncertainty does not apply to theintegrated radial parameters and the radial detector processing uncertainty containsonly the axially integrated processing component. The system two-dimensional uncertainty, as applied to FAH, is defined as:The 95/95 confidence level with a one-sided tolerance limit can be calculated from thestandard deviation for each component and the appropriate confidence level multiplier. The confidence level multiplier (k) is directly dependent on the size of the data set andwas determined from Reference

4. For reference, the components and confidence factors from YAEC-1 855PA are provided in Table 1 below.

AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PALicensing Report Paae 29Table I Uncertainty Components and Confidence Multipliers fromYAEC-1855PA AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 306.2 Proposed Uncertainty Modifications 6.2.1 OverviewA new uncertainty analysis was performed that better represents the true measurement uncertainty for FQ and FAH over a wide range of conditions by propagating theuncertainties through the FIDS analysis system using a Monte Carlo statistical simulation method. This statistical simulation method replaces the signal reproducibility (aa), and detector processing (Gd and Ge) uncertainty terms in the YAEC-1855PA uncertainty analysis. The FIDS analysis system is statistical in nature. Consequently, the determination ofthe measured peaking factor is affected by detector measurement variability, thenumber and layout of available detectors, signal replacement techniques, expansion ofthe measured power to uninstrumented core locations, and any differences betweenpredicted and true power distribution. Accordingly, a range of conditions need to beconsidered in determination of the system uncertainty. For this reason the FIDSanalysis system uncertainty has been determined using the Monte Carlo statistical simulation method in which [] The FIDS analysis system determines the measured powerdistribution FAH and FQ surveillance parameters from these simulated detector signalsusing the power distribution processing methodology described in Section 4.0 of YAEC-1855PA, including the proposed modifications described in Sections 2.2, 3.3, and 4.2 ofthis document. In the simulation, a range of detector failures is considered incombination with a range of perturbations between the predicted and true powerdistribution. This uncertainty analysis methodology is similar to that employed by the Reference 5and 6 core power distribution monitoring systems previously reviewed and approved bythe NRC. AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 316.2.2 Methodology The FIDS analysis system contains two major software components: FINC andSIMULATE-3. In normal core monitoring, SIMULATE-3 provides the predicted detectorsignals and a predicted power distribution. FINC uses the measured and predicted detector signals to adjust the predicted power distribution to produce the measuredpower distribution. This algorithm is described in YAEC-1855PA, Section 4.4.For the uncertainty calculation, [I AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensinq Report Page 32 AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 33] The uncertainty factors forAnalytical Methods and Axial Signal Power Shape (ob and Oc in Equations 7 and 8 ofYAEC-1855PA) are retained because those effects cannot be analyzed by thisuncertainty methodology. FQ UL(95/95) and FAH UL(95/95) are also computed with an equivalent non-parametric method that does not assume the distributions are normal. [[I AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PALicensing Report Page 34 AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensingq Report Page 35Figure 25 Flow Diagram of Calculations AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 366.2.3 Uncertainty Calculation Details6.2.3.1 Physics Analytical Methods Uncertainty The CASMO-3 and SIMULATE-3 code package used to generate all analytical predictions for power distribution related parameters has not changed since the initiallicensing analysis in YAEC-1855PA. Since the physics analysis methods have notchanged, the analytical methods uncertainty, 0b, has not changed6.2.3.2 Axial Power Shape Uncertainty As noted in YAEC-1855PA, the axial profiles calculated by SIMULATE-3 are the basisfor determining the measured axial power shapes from the fixed detector data within thecore. Measured axial power distributions are determined from the fixed incore detectorsignals and from the detailed axial power shapes generated by the SIMULATE-3 analytical model. Since the SIMULATE-3 methodology has not changed, the axialpower shape uncertainty, ao, has not changed.6.2.3.3 Simulation Uncertainty Analysis6.2.3.3.1 Operating State PointsThree operating state points were chosen for the uncertainty analysis:

  • Cycle 14, cycle exposure where FNH is near the maximum, excluding the beginning of cycle non-equilibrium cases.* Cycle 14, cycle exposure where FQ is near the maximum, excluding the beginning ofcycle non-equilibrium cases.* Cycle 13, cycle exposure where axial offset is near minimum (largest negative value)and the Axial Offset mismatch is also near maximum.

AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PALicensing Report Page 376.2.3.3.2 Perturbations in Measured Power Distributions 6.2.3.3.3 Detector Signal VarianceDetector signal variance consists of reproducibility of detector responses, uncertainty inplant parameter measurements, variability in reactor conditions, uncertainty in detectorsensitivity corrections (including sensitivity, gamma, and depletion corrections), anduncertainty in the detector predictive model. [I AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 386.2.4 Uncertainty Calculation ResultsThree reactor operating state points were analyzed. [I AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PALicensinq Report Pa-qe 39 AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 40 AREVA Inc. AIPSeabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA R~nnrtXlP-3243NP Revision 1Paae 41Licensinn Report Paoe 41 AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 426.2.5 Analysis of Significant Trends AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Paqe 43Table 2 95/95 Uncertainty Limits for FAH and FQ AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 44Figure 26 FAH UL(95/95) Plots for Cycle 14, FAH Near Maximum AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 45Figure 27 FQ UL(95/95) Plots for Cycle 14, FAH Near Maximum AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 4

67.0 CONCLUSION

S The information provided here to supplement YAEC-1 855PA shows the modifications made to the FINC code to improve the accuracy and accommodate replacement detectors consistent with the concept of the standard detector as noted in YAEC-1855PA. The modifications to FINC utilize the information determined from anextensive trending program to analyze the first 15 cycles of operation of Seabrook. Thererun of 15 cycles of flux maps showed detector performance data Which providesconfidence in the proposed method of analysis. The current licensing basis uncertainty analysis methodology is replaced with a newmethodology that determines the true measurement uncertainty for FQ and FAH. Theseuncertainties are specific to the analytical physics methods, CASMO-3 and SIMULATE-3 and the incore data processing code, FINC, and the general design of the platinumfixed detectors for Seabrook Station. Conservatively bounding measurement uncertainty values of 4.0% for FAH and 5.0% for FQ for the FIDS analysis methodology are proposed. These are slightly higher than the values supported by the uncertainty analysis and are consistent with the Moveable Incore Detector System (MIDS). AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PALicensinq Report Paqe 4

78.0 REFERENCES

1. Joseph P. Gorski, "Seabrook Station Unit 1 Fixed Incore Detector SystemAnalysis,"

YAEC-1855PA, October 1992.2. M. Edenius and Bengt-Herman

Forssen, "CASMO-3:

A Fuel AssemblyBurnup Program, User's Manual," STUDSVIK/NFA-89/3, January 1991.3. K.S. Smith, K.R. Rempe and D.M. VerPlanck, "SIMULATE-3: AdvancedThree-Dimensional Two-Group Reactor Analysis Code, Methodology," STUDSVIK/NFA-89-04, November 1989.4. D.B. Owen, Factors for One-Sided Tolerance Limits and for Variables Sampling Plans, SCR607, US Dept. of Commerce, March 1963.5. R. Kochendarfer, "Statistical Universal Power Reconstruction with FixedMargin Technical Specifications," ANP-1 0301 P-A. AREVA, Inc.,September 2013.6. R. Kochendarfer, C. T. Rombaugh and A.Y. Cheng, Fixed MarginTechnical Specifications," BAW-10158P-A. Babcock and Wilcox, August1986.7. Carl A. Bennett and Normal L. Franklin, "Statistical Analysis in Chemistry and the Chemical Industry", John Wiley & Sons, New York, 1954.8. Gerald J. Hahn and Samuel Shapiro, "Statistical Models in Engineering", John Wiley & Sons Inc., New York, 1967.9. Mary Gibbons Natrella, "Experimental Statistics", National Bureau ofStandards", 1963. AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 48APPENDIX AThe trending analysis processed the measured signal data for 15 cycles of Seabrookoperation. The trending analysis used the calculation sequence of cross sectiongeneration by CASMO-3, power prediction generation by SIMULATE-3 and measureddata processed by FINC. The CASMO-3 and SIMULATE-3 codes are the sameversions used in YAEC-1855PA and have not changed. The trending analysiscontained the use of the Neutron Conversion Factor (NCF) that was introduced inCycle 9.CASMO-3 provides the cross section input and gamma response to SIMULATE-3. Thepower distribution predictions, predicted gamma signal, and neutron reaction rate areproduced by SIMULATE-3. For the trending

analysis, the data extracted fromSIMULATE-3 was the three dimensional power distributions, the detector gamma signaland the nodal neutron reaction rate for platinum.

FINC processed the measured signalscorrecting for the surface area to obtain results for a standard detector. Post processing software and Excel spreadsheets were used to analyze the data. Thefollowing pieces of data were used in the trending analysis: " The measured signal, SM, from FINC corrected for surface area to correct to astandard detector.

  • The predicted gamma signal, SG, for the five detector levels came from SIMULATE-3 without modification.

" The detector neutron reaction rate came from the 3D predicted nodal neutronreaction rate for platinum from SIMULATE-3 and collapsed by the post processing software over the detector length and axial location to obtain Rn. AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensinq Report Page 49" Detector power was generated by the post processing software from the 3D nodalassembly power fraction from SIMULATE-3. The nodal assembly power fractionwas collapsed over the detector length and axial location to generate a detectorpower in megawatts.

  • Detector exposure was generated by the post processing software from the 3Dnodal assembly exposure from SIMULATE-3.

The nodal assembly exposure wascollapsed over the detector length and axial location to generate a detector exposurein GWD/MTU. The detector exposure was accumulated to be current for each fluxmap.* A power independent measured detector signal was generated by the postprocessing software by dividing the measured signal, SM, by the detector power. AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 50The trending analysis is based on 15 cycles of Seabrook operation as summarized below:* Seabrook contains 58 detector strings with 5 detectors per string.* The 15 cycles comprise 813 reactor flux maps." Failed detectors or detector strings were removed, i.e., no signal produced. " The analysis considered only original detectors for the determination of the NCF andDPC. Replacement detectors were incorporated into the figures to showconsistency.

  • This resulted in 221,226 unique data points." A total of 145 anomalous flux maps were removed.

Non-equilibrium flux maps andflux maps with an axial offset anomaly were removed in order to obtain a goodestimate of the NCF and DPC parameters. A total of 145 flux maps were removed.* The result was that 180,393 unique data points were used in the trending analysis. The results of the trending analysis are provided in Figure A-1 through Figure A-16.The trending analysis for the original detectors is over all 15 cycles while the trendingfor the replacement detectors is over Cycle 14 and 15 for the Batch 1 replacement detectors and Cycle 15 for the Batch 2. replacement detectors. Where applicable, thefigures show a linear fit through the data as a solid black line.Figure A-1 shows the measured signal (SM) divided by the detector power versusdetector exposure for the original detectors. Figure A-2 shows the measured signaldivided by the detector power versus detector exposure for the replacement detectors. The overall trend shows a decrease in signal as a function of detector exposure for boththe original and replacement detectors. The trend shows changes due to changes inneutron and gamma spectrum during cycle burnup; changes from cycle to cycle due tocore design and operating conditions; and changes due detector depletion. AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PALicensing Report Page 51Figure A-3 shows the calculated gamma signal (Cy*SG from Equation 2 in Section 2.2)divided by the detector power versus detector exposure for the original detectors. Figure A-4 shows the calculated gamma signal divided by the detector power versusdetector exposure for the for the replacement detectors. The overall trend shows adecrease in the calculated gamma signal as a function of detector exposure for both theoriginal and replacement detectors. The trend shows that the predictive model capturesthe effect of changes during the cycle, changes in core design and fuel management strategy and changes in operation conditions. The predictive model does not accountfor detector depletion. Figure A-5 shows the inferred neutron signal [] divided by the detectorpower versus detector exposure for the original detectors. The overall trend shows adecrease in the inferred neutron signal as a function of detector exposure. Figure A-6shows the inferred neutron signal divided by the detector power versus detectorexposure for the replacement detectors. Due to the short exposure time and the smallnumber of replacement detectors, the overall trend shows no discernible decrease inthe inferred neutron signal as a function of detector exposure. To isolate the effect of detector depletion, the Neutron Conversion Factor (NCF)calculated from Equation 6 is used. Figure A-7 shows the NCF versus detectorexposure for the original detectors. The overall trend shows very slight decrease in theNCF as a function of detector exposure. From this data a linear relationship for theNCF was determined as NCF = A + B*E where E is the detector exposure in GWD/MTUand A and B are the constants of the linear equation. For comparison, Figure A-8shows the NCF versus detector exposure for the for the replacement detectors. Again,due to the short exposure and the small number of replacement detectors, the overalltrend shows no discernible decrease or increase in the NCF as a function of detectorexposure. It should be noted that the NCF for all detectors is derived from the originaldetectors only. Figure A-8 is intended to show the similarity in NCF between originaland replacement detectors. AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensinq Report Paqe 52Figure A-9 shows the calculated gamma signal divided by the measured signal as afunction of detector exposure for the original detectors. From this figure it is clear thatthe gamma portion of the signal has been approximately 75% of the total signal. Therefinement made in Cycle 9 to use the NCF rather than a straight 25% of the gammaportion of the signal more accurately represents the change in the neutron portion of thesignal with changing core conditions. Figure A-10 shows the calculated gamma signaldivided by the measured signal as a function of detector exposure for the replacement detectors. The trend of the replacement detectors appears to be consistent with that ofthe original detectors. From the 15 cycles of trend data, there are observed trends in the measured signal, thecalculated gamma signal, and the inferred neutron signal. [I AREVA Inc. AISeabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PALicensina RenortNP-3243NP Revision 1Paqe 53Figure A-12 shows the difference between the predicted and measured signals for theoriginal detectors using the proposed model. This figure shows there is no trend in thedata with exposure and provides a basis for the proposed model. AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 54Replacement detector strings were installed in Cycle 14 (Batch 1) and Cycle 15(Batch 2). The replacement detectors were constructed to be similar to the originaldetectors, but are slightly less sensitive than the original detectors due primarily tochanges in the manufacturing process. The change in sensitivity was noted and theFINC code was modified to introduce a batch dependent Gamma Correction Factor. Aspart of the trending

analysis, the change in the Batch 1 and Batch 2 sensitivity wasrefined by comparing the measured signal from the replacement detectors to theirsymmetric partners of original detectors.

The detector signals were corrected fordepletion effects using the DPC from above. The comparisons are shown graphically inFigure A-14 and Figure A-15 for the Batch 1 detectors and in Figure A-16 for the Batch2 detectors. Figure A-1 3 shows the difference between the predicted and measured signals for thereplacement detectors using the proposed model with the Gamma Correction Factor.This figure shows there is no trend in the data with exposure but a small bias. Since thebias is small, this provides a basis for the proposed model with the replacement detectors. Using the approach of comparing to symmetric

partners, the Gamma Correction Factor(GCF) is computed as:Equation 11 GCF = Signal from Original Detector
  • DPCSignal from Replacement Detector
  • DPCGamma Correction Factor for the replacement detectors is provided by detector batchand the GCF for Batch 1 is 1.0577 and the GCF for Batch 2 is 1.0849. These valueswith be input to FINC as constants to be applied to the Batch 1 and Batch 2 measuredsignals as simple multipliers.

AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 55Figure A-1 Measured Signal Divided by Detector Power versus Detector

Exposure, Original Detectors AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 56Figure A-2 Measured Signal Divided by Detector Power versus Detector
Exposure, Replacement Detectors

- AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 57Figure A-3 Calculated Gamma Signal Divided by Detector Power versus Detector

Exposure, Original Detectors AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 58-Figure A-4 Calculated Gamma Signal Divided by Detector Power versus Detector
Exposure, Replacement Detectqor AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 59Figure A-5 Inferred Neutron Signal Divided by Detector Power versus Detector
Exposure, Original Detectors AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensinq Report Page 60-Figure A-6 Inferred Neutron Signal Divided by Detector Power versus Detector
Exposure, Replacement Detectors AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 61Figure A-7 Neutron Conversion Factor versus Detector
Exposure, Original Detectors AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 62Figure A-8 Neutron Conversion Factor versus Detector
Exposure, Replacement Detectors AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 63Figure A-9 Calculated Gamma Divided by Measured Signal versus Detector
Exposure, Original Detectors AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 64Figure A-10 Calculated Gamma Divided by Measured Signal versus Detector
Exposure, Replacement Detectors AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 65Figure A-11 Depletion Correction Factor AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 66Figure A-12 Difference between Predicted and Measured
Signals, Original Detectors, Proposed Model AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 67Figure A-1 3 Difference between Predicted and Measured
Signals, Replacement Detectors, Proposed Model AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 68Figure A-14 Ratio of Measured Signals for Original to Replacement Detectors, Batch 1, Cycle 14 AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 69Figure A-15 Ratio of Measured Signals for Original to Replacement Detectors, Batch 1, Cycle 15 -

AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 70-Figure A-16 Ratio of Measured Signals for Original to Replacement Detectors, Batch 2, Cycle 15 AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensinq Report Page 71APPENDIX B AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 72 AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Paqe 73 AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensingq Report Page 74 AREVA Inc. ASeabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PALicensing Report4P-3243NP Revision 1Paqe 75Table B-1 Conservative Trend Slope of FAH UL(95/95) and FQUL(95/95) for a Maximum of 8 Failed Detector Strings AREVA Inc. ANP-3243NP Revision 1Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensinq Report Paqe 76Figure B-1 Example Linear Least Square Fits of FAH (UL 95/95) and FQ(UL 95/95)}}

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