ML13260A161

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ANP-3243NP, Rev. 0, Seabrook Station Unit I Fixed Incore Detector System Analysis Supplement to YAEC-1855PA, Licensing Report
ML13260A161
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Site: Seabrook NextEra Energy icon.png
Issue date: 07/31/2013
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AREVA, AREVA NP
To:
Office of Nuclear Reactor Regulation
References
SBK-L-13121 ANP-3243NP, Rev 0
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ATTACHMENT 4 ANP-3243NP, "Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA

A AREVA Seabrook Station Unit I Fixed Incore ANP-3243NP Revision 0 Detector System Analysis Supplement to YAEC-1855PA Licensing Report July 2013 AREVA NP Inc.

(c) 2013 AREVA NP Inc.

Copyright © 2013 AREVA NP Inc.

All Rights Reserved

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Paqe Nature of Changes Section(s)

Item or Page(s) Description and Justification 1 All Initial Issue

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page ii Contents Pa.e 1.0 TECHNICAL EVALULATION................................................................................ 1 1.1 Background........................................................................I 2.0 NEUTRON CONVERSION FACTOR .............................................................. 4 2.1 Current Licensing Basis ......................................................................... 4 2.2 P roposed Method ................................................................................... 6 3.0 REPLACEMENT DETECTORS ....................................................................... 8 3 .1 G e n e ra l ................................................................................................ . .8 3.2 Current Licensing Basis ......................................................................... 9 3.3 Proposed Modification .......................................................................... 9 4.0 DEPLETION CORRECTION FACTOR ......................................................... 11 4.1 Current Licensing Basis ....................................................................... 11 4.2 Proposed Modification ........................................................................ 11 5.0 COMPARISON OF FINC RESULTS .............................................................. 12 5 .1 G e ne ra l .............................................................................................. . . 12 5.2 Surveillance Parameter Comparisons ................................................. 12 5.3 S tatistical Results ................................................................................. 26 6.0 UNCERTAINTY ANALYSIS ........................................................................... 28 6.1 Current Licensing Basis ....................................................................... 28 6.2 Proposed Uncertainty Modifications ..................................................... 31 6.2.1 Detector Signal Reproducibility ................................................. 31 6.2.2 Physics Analytical Methods Uncertainty .................................... 32 6.2.3 Axial Power Shape Uncertainty ................................................. 32 6.2.4 Detector Processing Uncertainty (2D and 3D) .......................... 32 6.2.5 Fixed Incore Detector Uncertainty ............................................. 35 7.0 C O NC LU S IO NS .............................................................................................. 38 8.0 R E FE R E NC E S .............................................................................................. 39 A P P ENDIXA ................................................................................................................. 40

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page iii List of Tables Table 1 Uncertainty Components and Confidence Multipliers from YAEC-18 5 5 P A ............................................................................................. . . 30 Table 2 Average 2D and 3D RMS by Cycle .............................................................. 34 Table 3 Uncertainty Components and Confidence Multipliers ................................... 37

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensing Report Page iv List of Figures Figure 1 Comparison of Heat Flux Hot Channel Factor FQ for Cycle 1 .................... 14 Figure 2 Comparison of Heat Flux Hot Channel Factor FQ for Cycle 2 .................... 14 Figure 3 Comparison of Heat Flux Hot Channel Factor FQ for Cycle 3 .................... 15 Figure 4 Comparison of Heat Flux Hot Channel Factor Fa for Cycle 4 .................... 15 Figure 5 Comparison of Heat Flux Hot Channel Factor FQ for Cycle 5 .................... 16 Figure 6 Comparison of Heat Flux Hot Channel Factor FQ for Cycle 6 .................... 16 Figure 7 Comparison of Heat Flux Hot Channel Factor FQ for Cycle 7 .................... 17 Figure 8 Comparison of Heat Flux Hot Channel Factor FQ for Cycle 8 .................... 17 Figure 9 Comparison of Enthalpy Rise Hot Channel Factor FAH for Cycle 1 ............ 18 Figure 10 Comparison of Enthalpy Rise Hot Channel Factor FAH for Cycle 2 .......... 18 Figure 11 Comparison of Enthalpy Rise Hot Channel Factor FAH for Cycle 3 .......... 19 Figure 12 Comparison of Enthalpy Rise Hot Channel Factor FAH for Cycle 4 .......... 19 Figure 13 Comparison of Enthalpy Rise Hot Channel Factor FAH for Cycle 5 .......... 20 Figure 14 Comparison of Enthalpy Rise Hot Channel Factor FAH for Cycle 6 ...... 20 Figure 15 Comparison of Enthalpy Rise Hot Channel Factor FAH for Cycle 7 .......... 21 Figure 16 Comparison of Enthalpy Rise Hot Channel Factor FAH for Cycle 8 .......... 21 Figure 17 Comparison of Axial Offset for Cycle 1 .................................................... 22 Figure 18 Comparison of Axial Offset for Cycle 2 .................................................... 22 Figure 19 Comparison of Axial Offset for Cycle 3 .................................................... 23 Figure 20 Comparison of Axial Offset for Cycle 4 .................................................... 23 Figure 21 Comparison of Axial Offset for Cycle 5 .................................................... 24 Figure 22 Comparison of Axial Offset for Cycle 6 ...................................................... 24 Figure 23 Comparison of Axial Offset for Cycle 7 .................................................... 25 Figure 24 Comparison of Axial Offset for Cycle 8 .................................................... 25 Figure A- 1 Measured Signal Divided by Detector Power versus Detector Exposure, O riginal Detectors .............................................................. 47 Figure A- 2 Measured Signal Divided by Detector Power versus Detector Exposure, Replacement Detectors ..................................................... 48 Figure A- 3 Calculated Gamma Signal Divided by Detector Power versus Detector Exposure, Original Detectors ................................................. 49

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensing Report Page v Figure A- 4 Calculated Gamma Signal Divided by Detector Power versus Detector Exposure, Replacement Detectors ....................................... 50 Figure A- 5 Inferred Neutron Signal Divided by Detector Power versus Detector Exposure, Original Detectors .............................................................. 51 Figure A- 6 Inferred Neutron Signal Divided by Detector Power versus Detector Exposure, Replacement Detectors ..................................................... 52 Figure A- 7 Neutron Conversion Factor versus Detector Exposure, Original Dete cto rs .......................................................................................... . . 53 Figure A- 8 Neutron Conversion Factor versus Detector Exposure, Replacement Dete cto rs .......................................................................................... . . 54 Figure A- 9 Calculated Gamma Divided by Measured Signal versus Detector Exposure, Original Detectors .............................................................. 55 Figure A- 10 Calculated Gamma Divided by Measured Signal versus Detector Exposure, Replacement Detectors .................................................... 56 Figure A- 11 Depletion Correction Factor ................................................................. 57 Figure A- 12 Difference between Predicted and Measured Signals, Original Detectors, Proposed Model ................................................................ 58 Figure A- 13 Difference between Predicted and Measured Signals, Replacement Detectors, Proposed Model ................................................................ 59 Figure A- 14 Ratio of Measured Signals for Original to Replacement Detectors, B atch 1, C ycle 14 ............................................................................... . . 60 Figure A- 15 Ratio of Measured Signals for Original to Replacement Detectors, Batch 1, C ycle 15 ............................................................................... . . 61 Figure A- 16 Ratio of Measured Signals for Original to Replacement Detectors, Batch 2, C ycle 15 ............................................................................... . . 62

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page vi Nomenclature Acronym Definition FAH Enthalpy rise hot channel factor Fdh Same as FAH; nomenclature used in YAEC-1855PA FQ Heat flux hot channel factor FIDS Fixed Incore Detector System NCF Neutron Conversion Factor GCF Gamma Correction Factor DPC Depletion Correction Factor ST Total calculated detector signal SG Calculated detector signal due to gamma SM Measured signal Cy Unit conversion factor for calculated detector gamma signal (DTh Thermal neutron flux (FTh avg Average thermal neutron flux Rn Neutron reaction rate for Pt-1 95 Cn Same as NCF Cd Coefficient of DPC versus detector exposure E Detector exposure RMS Root Mean Square 2D Two-dimensional 3D Three-dimensional Standard deviation for signal reproducibility (Yb Standard deviation for analytical methods oc Standard deviation for axial power shape ad Standard deviation for detector processing at Standard deviation for total system (3D) kr Standard deviation for integral processing (2D) k Confidence interval multiplier

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensing Report Page vii ABSTRACT This 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 are predominantly gamma sensitive and have a contribution from neutron capture. The FIDS have operated successfully for over 20 years of operation. In 2007, Seabrook undertook a phased detector replacement project. The specification for the replacement detectors were designed to be a like-for-like replacement. However, changes in manufacturing techniques required changes to the FIDS Analysis methodology to incorporate correction factors to normalize the replacement 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 of operation to determine appropriate modifications to Fixed Incore Detector Code (FINC).

Based on the trending analysis, revisions were made to the FIDS Analysis methodology. The modifications include a more precise method to determine the detector neutron conversion factor to better predict the neutron portion of the fixed detector signal based on the predicted neutron reaction rate. Modifications were also made to track detector exposure and to make a depletion correction to the measured signal based on the detector exposure. To normalize the replacement and original detectors, correction factors were quantified and incorporated as a multiplier on the measured signal of the replacement detectors.

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensing Report Page viii The FINC code was modified to incorporate the revised FIDS Analysis methodology and the proposed modifications were used to rerun all 15 cycles of flux maps. Following the uncertainty analysis methodology described in YAEC-1855PA, the results from the rerun of the 15 cycles of flux maps were used to determine the accuracy of the system.

From the analysis, changes were made to the integral and total detector processing components of the uncertainty. In addition the detector reproducibility was analyzed over Cycles 14 to 16 and changes were made to the reproducibility component of the uncertainty analysis, This report describes the detector performance trending analysis of the 15 cycles, documents the proposed modifications to the FIDS Analysis methodology and provides a new determination of the resulting measurement uncertainty for the FQ and FAH Technical Specifications (Tech Specs) surveillance parameters.

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 1 1.0 TECHNICAL EVALULATION 1.1 Background Seabrook Station started Cycle 1 with a combination fixed/movable detector system in 58 locations within the reactor core. The Detector Assemblies at that time accommodated the movable incore detector path, the qualified core exit thermocouple, and the five fixed platinum incore detectors. The movable detector system was used during the first four cycles of operation and was also used to benchmark the fixed platinum incore detectors. The fixed detector system was licensed by the NRC during Cycle 3 using the methodology described in YAEC-1855PA (Reference 1). The fixed platinum incore detectors and the methodology described in YAEC-1855PA have been used exclusively to monitor the core since Cycle 5.

YAEC-1855PA describes the methodology and uncertainty analysis used to determine core power distribution using the fixed incore detectors and the associated uncertainty.

The fixed incore detectors are self-powered platinum detectors which are predominantly gamma sensitive and produce a signal proportional to the local gamma flux in the reactor core. Although the majority of the signal from the platinum detectors is derived from the gamma flux, a portion of the signal is due to the neutron flux from an n,y reaction. There are 58 incore detector assemblies distributed radially throughout 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 are providing continuous core power distribution information. The detector signals are scanned once per minute and stored such that they may be retrieved and analyzed to determine the three dimensional power distribution and associated Tech Spec surveillance parameters. The computer software package used to analyze the fixed incore detector signals to determine the power distribution parameters is referred to as S3FINC and is described in YAEC-1855PA.

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensinq Report Page 2 S3FINC 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 detector responses. The second is the Fixed Incore Detector Code (FINC) which uses the SIMULATE-3 output and measured fixed incore detector signals to determine the measured core power distribution.

Included in YAEC-1855PA is a discussion on how the detector signals are treated as inputs 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 replaced due 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 starting with the OR13 (Cycle 14) refueling outage. Two detectors were replaced during OR13 and three were replaced during OR14 (Cycle 15). Seabrook has also embarked on a program to analyze data from the first 15 cycles of operation to quantify trends in the detector performance data and to validate the uncertainty analysis presented in YAEC-1855PA. This topical report serves as a supplement to YAEC-1855PA. The changes proposed are:

  • An improved prediction of the neutron component of the detector signal - Neutron Conversion Factor (NCF),

" Applying correction factors to the measured detector signal of the replacement detectors to better assure normalizatiQ.,-to a staiard detector performance -

Gamma Correction Factor (GCF), and

  • Accounting and correcting the measured detector signal for detector depletion to

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensing Report Page 3 better assure normalization to a standard detector performance - Depletion Correction (DPC).

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 4 2.0 NEUTRON CONVERSION FACTOR 2.1 CurrentLicensing Basis The signal from a platinum fixed incore detector is predominantly from gamma interaction 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 the topical report YAEC-1855PA and in the associated NRC SER dated 12/23/1993 that the fraction of the total detector signal due to neutrons is approximate and not well known at the time. Section 3 of YAEC-1 855PA describes the assumptions used to determine an estimate for the fraction of total detector signal due to neutrons. At that time, public domain studies and a Seabrook specific sensitivity study based on operational data were used to determine the estimate of the fraction neutron component to be used as an input assumption in determining the predicted detector signal. Based on the literature and the sensitivity study a value of 25% of the total signal was attributed to neutrons.

To accommodate the platinum detectors, SIMULATE-3 was modified, to allow the user to input the fractional neutron component of the predicted detector signal. This fraction is given in terms of the total detector signal, and it can be distributed by either or both the fast and thermal neutron flux. The gamma portion of the detector's signal is determined through the total responses determined in CASMO-3 cases and local detector neutron flux calculations within SIMULATE-3. This is the standard method of detector calculations used within SIMULATE-3. The total neutron portion of detector signal 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. The individual detector's gamma and neutron portions are then summed to determine the detector's total signal.

As described in YAEC-1 855PA, a value of 0.25 was used for the thermal neutron component of the predicted detector signal. Thus the total gamma signal was calculated in SIMULATE-3 as:

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensina RePort Paae 5 I

The above value of ST was used in FINC starting in Cycle 1.

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 6 2.2 ProposedMethod To better cover a broader range of reactor core design and operating conditions, a new formulation for determining the neutron component of the predicted detector signal was developed. Rather than use the straight 25% of the gamma signal to represent the neutron portion, it was determined that a more accurate representation of the total signal could be accomplished by adding a neutron portion to the gamma signal based on 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 factor is shown in Equation 2.

AREVA NP Inc. AISIP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensino Renort Paae 7 Licensina Rer)ort Paoe 7 I

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 8 3.0 REPLACEMENT DETECTORS 3.1 General The Seabrook specification for replacement detectors was written to produce a like-for-like replacement of the original detectors. The replacement detectors were built to the original specification and within the as-built attributes of the original detectors including detector geometry, dielectric densities and component material impurities. The replacement detectors were also constrained to the characteristics assumed in the analysis software licensed for the system. These precautions served to preserve the like-for-like nature of the replacement detectors to the original detector. Nonetheless, the manufacturing enhancements developed in more than 20 years of detector service result in differences in detector performance as observed in gamma testing of the replacement detectors and archive original detectors.

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 9 3.2 CurrentLicensing Basis As described in YAEC-1855PA, the FINC code depends on the concept of a standard detector. In the standard detector approach, the raw measured detector signals must be corrected for individual detector differences. The signal from any individual detector is 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 signal given by a standard detector. The standard detector is one built to exact design dimensions. 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 the surface area of a standard detector. The data required for the calculation of the sensitivity factors is provided by the detector manufacturer's as-built data of detector length 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 and weight. 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 by using the manufacturers measured weight and length for each detector compared to the weight and length of a standard detector.

3.3 ProposedModification The replacement detector specification required that each individual replacement detector is tested for operation using a gamma source. In addition, to verify compatibility, original archive detectors are tested in the same gamma source environment. During the testing, it was noted that the replacement detectors produced a lower signal than the original detectors in the same gamma field and could not be corrected by application of the simple sensitivity factor based only on as-built detector length and weight.

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensing Report Page 10 The Gamma Correction Factor (GCF) was introduced in Cycle 14 to make the replacement detector signal compatible with the signal from the original detectors. The GCF 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 2 replacement detectors based on changes in the manufacturing process. As part of the trending analysis, the GCF was refined through the trending analysis of Appendix A as shown in Figure A- 14, Figure A- 15, and Figure A- 16. The trending analysis compared the difference in signal between the replacement detectors and their symmetric partners over Cycles 14 and 15 for the Batch 1 detectors and over Cycle 15 for the Batch 2 detectors. The GCF values reflect in-reactor measurements of symmetric partners in the Seabrook reactor environment. The value of Batch 1 GCF is 1.0577 and the Batch 2 GCF is 1.0849. The Batch 2 replacement detectors defined the future manufacturing process. It is the intent to use the Batch 2 GCF for future batches of replacement detectors. However, since the magnitude of the detector signal can be affected by the manufacturing process, future batches of detectors may require their own GCF determined through testing.

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensing Report Page 11 4.0 DEPLETION CORRECTION FACTOR 4.1 CurrentLicensing Basis The current licensing basis does not include a depletion correction factor. The modeling of the effects of elemental platinum depletion is not required as described in YAEC-1 855PA in response to RAI Question 4. The response showed that the rate of depletion would be less than 1% in ten years. Thus, no provisions were provided in the current licensing basis for a depletion correction.

4.2 ProposedModification

] This effect is primarily due to the consumption of the Pt-195 isotope which is the predominant contributor to the neutron 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- 11.

Detector exposure is the accumulated fuel exposure of the assembly containing the detector, averaged over the detector length. With the proposed modification of FINC, the DPC will be calculated for each detector based on detector exposures using the derived curve. The DPC will be applied to each individual detector and will vary with detector exposure. The DPC as included in FINC is given as:

Equation 3 DPC = 1 + Cd

  • E Where Cd is the depletion constant and E is the detector exposure in GWD/MTU.

From Equation 3, the depletion correction factor utilizes the detector exposure to obtain a multiplier to be applied to the measured signal for each detector.

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 12 5.0 COMPARISON OF FINC RESULTS 5.1 General With the completion of the trending analysis in Appendix A, the proposed modifications to FINC were established. To determine the effect of these modifications on the surveillance parameters, all 15 cycles of flux maps were rerun with the revised version of FINC incorporating the proposed modifications. The 15 cycles provides a good test of the proposed modifications to FINC under an array of operating conditions that involved 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 for flux maps that were run under equilibrium conditions as would be the case for normal surveillance.

5.2 Surveillance ParameterComparisons This section shows the comparison of the original FINC version to the modified FINC version for the Tech Spec surveillance parameters. Although all 15 cycles of flux maps were rerun with the modified version of FINC, comparisons are provided here for the first eight cycles. During these cycles the licensing model used a fixed 25% of the gamma signal as the neutron portion of the signal and did not include a correction for detector exposure. The proposed modifications to FINC utilize a neutron conversion factor and the neutron reaction rate to determine the neutron portion of the signal. The proposed model also includes a correction for depletion based on the exposure of each individual detector. The comparisons for the heat flux hot channel factor FQ are provided in Figure 1 through Figure 8. The value of FQ includes the current measurement 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 9 through Figure 16 and the comparisons for axial offset are provided in Figure 17 through Figure 24.

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensing Report Page 13 The results provided in Figure 1 through Figure 24 show that performance of the proposed model compares well to the current licensing basis model. In these figures the proposed model contains the neutron conversion factor, detector exposure tracking and the depletion correction. The NCF was introduced in Cycle 9 in 2002 so that a comparison to the original FINC version, consistent with the current licensing basis methodology could not be made after Cycle 8.

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Paae 14 Figure 1 Comparison of Heat Flux Hot Channel Factor FQ for Cycle I 2.20 2.00 1.80 E i*

E1.60 1.40 1.20

    • Licensing Model nOProposed Model 1.00 0 2000 4000 6000 5000 10ODD 12000 14000 Cyde Exposure (MWD/MTU)

Figure 2 Comparison of Heat Flux Hot Channel Factor FQ for Cycle 2 1.95 1.90 1.85 E

1L.80 0 9 0 o 00 1.75

  • 0
  • 0]

1.70 0

  • Licensing Model OProposed Model 1.65 0 2000 4000 6000 8000 10000 12000 Cyde Exposure (MWD/MTU)

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensing Report Page 15 Figure 3 Comparison of Heat Flux Hot Channel Factor FQ for Cycle 3 2.00 40 1.95 00 1.90 0

1.85

+0 1.80

  • 000 1.75 *, o.
  • Licensing Model OProposed Model 1.70 0 2000 4000 6000 800 10000 12000 140D 16000 Cycle Exposure (MWD/MTU)

Figure 4 Comparison of Heat Flux Hot Channel Factor FQ for Cycle 4 1.90 ,

1.85 1.80 L2.75 Efo 0 170O0 1.65

  • 000 1.60 1 Licensing Model OProposed Model 1.551 0 5000 10000 15000 20000 Cyde Exposure (MWD/MTU)

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit I Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Paqe 16 Figure 5 Comparison of Heat Flux Hot Channel Factor FQ for Cycle 5 2.00 1.90I o__ 0 (

1 1.75 -

1.70

  • Licensing Model

, 0-IProposed Model 1.65 0 5000 10000 15000 20000 Cyde Exposure (MWD/MTU)

Figure 6 Comparison of Heat Flux Hot Channel Factor FQ for Cycle 6 2.05 2.00 1.95 E 1.90

.185 1.80 1.75 1.70 0 5000 10000 15000 20000 25000 Cycle Exposure (MWD/MTU)

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensing Report Paqe 17 Figure 7 Comparison of Heat Flux Hot Channel Factor FQ for Cycle 7 1.90 1.85 1.80 E1.75 1.70 1.65 1.60 0 5000 10000 15000 20000 Cyde Exposure (MWD/MTU)

Figure 8 Comparison of Heat Flux Hot Channel Factor FQ for Cycle 8 1.90*

1.88A 1.86 1.84 .

1.82 S1.78 1.76 1.74 1.72

  • Licensing Model I-Proposed Model 1.70 - I I 0 5000 10000 15Oo0 20000 Cyde Exposure (MWD/MTU)

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit I Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensing Report Page 18 Figure 9 Comparison of Enthalpy Rise Hot Channel Factor FAH for Cycle 1 1.40 1.38 -

1.36 p 1.34 E

E 1.32 0 91.30- t 7F  ;

1.28 [ +

1.26

  • Licensing Model n Proposed Model 1.24 1....

0 2000 4000 6000 8000 10000 12000 14000 Cyde Exposure (MWD/MTU)

Figure 10 Comparison of Enthalpy Rise Hot Channel Factor FAH for Cycle 2 1.49 0

1.48 1.47

  • ° 0 1.46
  • [0 0 1.45 E
  • n

-1.44 E nn 1.43 1.42 0

1.41 1.40

  • Licensing Model OProposed Model 1.39 0 2000 400D 600D 800D 10000 12000 Cyde Exposure (MWD/M'U)

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensing Report Paqe 19 Figure 11 Comparison of Enthalpy Rise Hot Channel Factor FAH for Cycle 3 1.46 4bjth0 00 1.45 o-1.44 - n 0 0 E

1.4 1.42 1.41

  • Licensing Model OProposed Model 1.40 0 2000 4000 6000 8000 10000 12000 14000 16000 C/de Exposure (MWD/MTU)

Figure 12 Comparison of Enthalpy Rise Hot Channel Factor FAH for Cycle 4 1.46 1.420 -

+ 40 1.38 1.36

  1. Licensing Model 0 Proposed Model 1.34 1 0 5000 10000 15000 20000 Cycle Exposure (MWD/MTU)

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensina Reoort Paae 20 Figure 13 Comparison of Enthalpy Rise Hot Channel Factor FAH for Cycle 5 1.49 1.48 1.47 1.46 X

U-oo~

1.45 E

E2 1.44 1.43 0*

1.42 1.41

  • Licensing Model OProposed Model 1.40 0 5000 10000 15000 20000 Cyde Exposure (MWD/MTU)

Figure 14 Comparison of Enthalpy Rise Hot Channel Factor FAH for Cycle 6 1.56 1.54 1.52 E1.50 E

1.48 1.46 1.44 1.42 0 5000 10000 15000 20000 25000 Cyde Exposure (MWD/MTU)

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensing Report Page 21 Figure 15 Comparison of Enthalpy Rise Hot Channel Factor FAH for Cycle 7 1.45 1.44 1.43

  • ~1.421 1.39 1.38 1.37
  1. Licensing Model 0-Proposed Model 1.36 ,I I 0 5000 10000 15000 20000 Cycle Exposure (MWD/MTU)

Figure 16 Comparison of Enthalpy Rise Hot Channel Factor FAH for Cycle 8 1.44 1.44 1.43 1.43 1.42 E 1.42 '4 E14 1.41 1.41 1.40 1.40 0

1.39 1.39

  1. Licensing Model 0-Proposed Model 0 5000 10OO 15000 20000 Cyde Exposure (MWD/MTU)

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 22 Figure 17 Comparison of Axial Offset for Cycle 1 0.0

-1.0

-2.0

  • 00

-3.0 a -4.0 0 M Md

! -5.0 A

-6.0

-7.0

-8.0

  • Lcnsing Modell nProposwed Modell

-9.0 T iceii 0 2000 4000 6000 8000 2000 12000 144000 Cyde Exposure (MWD/MTU)

Figure 18 Comparison of Axial Offset for Cycle 2 6.0 5.0 -

4.0-3.0 -

2.0 -

1.0o [71*

0.0 .B *

-1.

n

-2.0 0 Li

-3.0 []

  • Licensing Model 0lProposed Model

-4.0-0 2000 4000 6000 8000 10000 12000 Cyde Exposure (MWD/MWU)

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 23 Figure 19 Comparison of Axial Offset for Cycle 3 0.0

-0.5

-1.0 El 0 +

o 9-2.0 0 00

-2.5

-3.0 0 *0 M00

-3.5

  • Lic,,nsing Model O Proposed Model

-4.0 0 2000 4000 6000 5000 10000 12000 14000 16000 Cyde Exposure (MWD/MTU)

Figure 20 Comparison of Axial Offset for Cycle 4 1.46 -

1.44 - 0 0 1.42 - O 40 1.36 I

  • Licensing Model OProposed ModelI 1.34 ,

0 5000 10000 15000 20000 Cyde Exposure (MWD/MTU)

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensing Report Page 24 Figure 21 Comparison of Axial Offset for Cycle 5 2.0 1.0 0.0

-1.0 9-2.0 S-3.0

-4.0

-5.0

-6.0 0 5000 10000 15000 20000 Cvde Exposure (MWD/MTU)

Figure 22 Comparison of Axial Offset for Cycle 6 4.0 3.0 2.0 1.0 i 0.0

-1.0

-2.0

-3.0

-4.0

-5.0

-6.0 0 5040 10000 15000 20000 25000 Cyde Exposure (MWD/MTU)

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensing Report Page 25 Figure 23 Comparison of Axial Offset for Cycle 7 4.0 3.0 2.0 1.0 0.0

-- 1.0

-2.0

-3.0

-4.0

-5.0 0 5000 10000 15000 20000 Cvde Exposure (MWD/MTU)

Figure 24 Comparison of Axial Offset for Cycle 8 0.0

-0.5

-1.0

-1.5 9 -2.0 c -2.5

-3.0

-3.5

-4.0 0 5000 10000 15000 20000 Cyde Exposure (MWD/MTU)

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensing Report Page 26 5.3 StatisticalResults As noted in YAEC-1855PA, the uncertainty for detector processing accuracy is calculated by comparing detector signals measured at various core conditions to predictions of the detector signals at these same core conditions. During the rerun of 15 cycles of flux maps both the 2D and 3D RMS values were calculated. The total detector processing, 3D RMS, uses all 290 individual detectors and the integral detector processing, 2D RMS, represents the radial power in the 58 instrumented core locations.

To get the full complement of 290 detector and 58 detector locations, the 2D and 3D RMS includes detectors that were replaced using the signal replacement strategy of YAEC-1 855PA. The rerun of the 15 cycles with the proposed modifications included replacing individual detectors that failed and complete detector strings that failed. The signals were replaced by a simple weighting algorithm. For the replacement, if symmetric detector strings are available, a weighting factor is applied to the symmetric detector signal and this new value replaces the failed detector signal. The weighting factor is simply a ratio of the sum of operable detector signals in the string containing the failed detector to the sum of the same set of signals in the symmetric string. This ratio thus preserves the magnitude and shape of operable detectors in the failed detector's string. Once the ratio is calculated, the symmetric detector signal is multiplied by the ratio and a replacement signal is created. The replacement method yields a replacement signal with the relative magnitude of its symmetric partner(s) and the absolute magnitude consistent with the other detectors within the string. Alternatively, if no ratio can be determined due to inoperable detectors in the string, or the symmetric string is inoperable or the failed detector has no symmetric partners, then the signal from the predicted set is used in the replacement process described above.

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 27 The determination of the 2D and 3D RMS by comparing measured signals to predicted signals assures that the failed detectors are covered by the total detector processing and integral detector processing uncertainty. The comparison also assures that the methodology accurately provides for individual detector replacement as well as complete string replacement. Consistent with the conclusions of YAEC-1 855PA, the fixed incore detector system provides power distribution surveillance compliance, including detector failure allowance, which is comparable in accuracy and functionality with that performed by the movable detector system.

With the proposed modifications, the 15 cycles were rerun to determine the statistical results. From the rerun, 819 individual flux maps were analyzed. From those flux maps, 39 flux maps were excluded as being non-equilibrium cases resulting in 780 flux maps for statistical analysis. From the 780 maps, the total detector processing consisted of 226,200 data points for the 3D RMS and the integral detector processing consisted of 45,240 data points for the 2D RMS. The resulting 3D RMS was [ ]

and the 2D RMS was [ I compared to the licensing analysis of[ ] and [

] The 3D RMS showed a slight increase while the 2D RMS remained constant.

Details on an individual cycle basis are provided in Section 6.2.4. The accuracy and functionality remains comparable to the original YAEC-1855PA analysis and the Moveable Incore Detector System.

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 28 6.0 UNCERTAINTY ANALYSIS 6.1 CurrentLicensing Basis As noted in YAEC-1855PA, the uncertainty of the fixed incore detector system is addressed in four individual parts. Each of these parts are quantified and then statistically combined to arrive at a total system uncertainty to a 95% confidence level with a one-sided tolerance limit. The uncertainties associated with FAH and FQ have traditionally 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 does not 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:

I

AREVA NP Inc. ANIP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensina Reoort Paae 29 The 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 the four uncertainty components. The axial power shape uncertainty does not apply to the integrated radial parameters and the radial detector processing uncertainty contains only the axially integrated processing component. The system two-dimensional uncertainty, as applied to FAH, is defined as:

The 95% confidence level with a one-sided tolerance limit can be calculated from the standard 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 and was determined from Reference 4. For reference, the components and confidence factors from YAEC-1855PA are provided in Table 1 below.

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensing Report Page 30 Table I Uncertainty Components and Confidence Multipliers from YAEC-1855PA

[

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 31 6.2 ProposedUncertaintyModifications 6.2.1 Detector Signal Reproducibility The YAEC-1855PA analysis for detector reproducibility involved determining the standard deviation in each of the 290 detector signals over a one hundred minute time interval. The analysis was performed at four times in Cycle 1 and three times in Cycle 2.

The one hundred minute intervals were chosen during stable reactor conditions. From the seven time intervals analyzed in YAEC-1855PA, the maximum standard deviation, in any detector was less than [ ] and the average of all data collected was [

To address the detector signal reproducibility component of the uncertainty, an evaluation of the signal reproducibility in Cycles 14-16 was performed. The method used in the evaluation is the same as that used in YAEC-1855PA. To be consistent with the YAEC-1855PA evaluation, the 100-minute data sets to calculate the detector signal reproducibility for all detectors were chosen at the period of time where reactor coolant system boron concentration has peaked and remained relatively stable (-3 GWD/MTU). The 100 minute reproducibility data was determined for Cycles 14, 15, and 16 so that it includes both the original and replacement detectors. The peak boron concentration represents a period in the cycle where few makeup additions to the RCS are made to maintain power thereby making reactor power most stable. The total detector reproducibility determined for Cycle 14 is [ ] for Cycle 15 is [ I and for Cycle 16 is [ ] The average total signal reproducibility from these three cycles is [ ] which is less than the YAEC-1866PA value of [ ] To allow for additional margin in the total signal reproducibility, the value of ca will be conservatively increased to [ I

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensing Report Page 32 6.2.2 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 initial licensing analysis in YAEC-1855PA. Since the physics analysis methods have not changed, the analytical methods uncertainty, Ub, has not changed.

6.2.3 Axial Power Shape Uncertainty As noted in YAEC-1855PA, the axial profiles calculated by SIMULATE-3 are the basis for determining the measured axial power shapes from the fixed detector data within the core. Measured axial power distributions are determined from the fixed incore detector signals and from the detailed axial power shapes generated by the SIMULATE-3 analytical model. Since the SIMULATE-3 methodology has not changed, the axial power shape uncertainty, ac, has not changed.

6.2.4 Detector Processing Uncertainty (2D and 3D)

The detector processing uncertainty in YAEC-1855PA provides for both the three-dimensional (3D) total detector processing (Od) and the two-dimensional (2D) integral detector processing (Oe). The values were determined from measured data collected through the first cycle and a portion of Cycle 2. The results from the licensing basis has a three-dimensional total detector processing one sigma value of [ ] based on a total sample population of 6670 data points, and the two-dimensional integral detector processing one sigma value of [ ] with a total sample population of 1334 data points. The confidence multipliers (k) from Reference 4 are 1.68 for the total detector processing and 1.73 for the integral detector processing. It should be noted that YAEC-1855PA used conservative values for the confidence multipliers assuming a sample population of 5000 for the total detector processing and a sample population of 1000 for the integral detector processing.

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit I Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensing Report Page 33 As mentioned above, the 15 cycles were rerun with the proposed modifications to determine the statistical results. From the rerun, 819 individual flux maps were analyzed. From those flux maps, 39 were excluded as being non-equilibrium cases resulting in 780 flux maps for the statistical analysis. From the 780 maps, the total detector processing consisted of 226,200 data points for the 3D RMS and the integral detector processing consisted of 45,240 data points. The resulting 3D RMS is [ I and the 2D RMS was [ ] These values are based on the average of all 780 flux maps. The use of the 2D and 3D RMS compares the measured signal to the predicted signal providing assurance that that the prediction and measurement are accurate and that the methodology adequately provides for missing detectors and detector strings within the limits of the Tech Specs. In addition, the use of the extensive data set covers a wide range of reactor operating conditions including axial offset anomalies and core tilt as well as changes in fuel management strategy and fuel assembly design.

Furthermore, the integral and total detector processing uncertainty includes any uncertainty on the proposed modifications of the neutron conversion factor, detector exposure and depletion correction factor as well as the gamma correction factors used for the replacement detectors.

Table 2 shows the total number of flux maps used in the cycle and the average RMS values by cycle.

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Paae 34 Table 2 Average 2D and 3D RMS by Cycle I

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Paae 35 6.2.5 Fixed Incore Detector Uncertainty The table below shows the original uncertainty from YAEC-1855PA and the uncertainty based on the analysis described above. The confidence multipliers for total detector processing and integral detector processing have changed due to the increase in the number of data points (sample size). Although the sample size for these two parameters is greater than 10,000 points, the confidence multiplier for 10,000 points was used for conservatism.

Using the approach of YAEC-1 855PA, the uncertainty applied to the three-dimensional quantity of Fa will include the four terms from the original analysis. The total detector processing uncertainty, from Equation 4 above is:

[

I

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 36 Similarly, the uncertainty applied to the two-dimensional quantity of FAH will include the three terms from the original analysis. The integral detector processing uncertainty, from Equation 5 above is:

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensing Report Page 37 Table 3 Uncertainty Components and Confidence Multipliers

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensing Report Page 38

7.0 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 an extensive trending program to analyze the first 15 cycles of operation of Seabrook. The rerun of 15 cycles of flux maps showed detector performance data which provides confidence in the proposed method of analysis. The uncertainty analysis using the 15 cycles of operation show that the three-dimensional uncertainty applied to FQ is [

I and the two-dimensional uncertainty applied to FAH is [ ]. These uncertainties 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 platinum fixed detectors for Seabrook Station.

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 39

8.0 REFERENCES

1. Joseph P. Gorski,"Seabrook Station Unit 1 Fixed Incore Detector System Analysis," YAEC-1855PA, October 1992.
2. M. Edenius and Bengt-Herman Forssen, "CASMO-3: A Fuel Assembly Burnup Program, User's Manual," STUDSVIK/NFA-89/3, January 1991.
3. K.S. Smith, K.R. Rempe and D.M. VerPlanck, "SIMULATE-3: Advanced Three-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.

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensing Report Page 40 APPENDIX A The trending analysis processed the measured signal data for 15 cycles of Seabrook operation. The trending analysis used the calculation sequence of cross section generation by CASMO-3, power prediction generation by SIMULATE-3 and measured data processed by FINC. The CASMO-3 and SIMULATE-3 codes are the same versions used in YAEC-1855PA and have not changed. The trending analysis contained the use of the Neutron Conversion Factor (NCF) that was introduced in Cycle 9.

CASMO-3 provides the cross section input and gamma response to SIMULATE-3. The power distribution predictions, predicted gamma signal, and neutron reaction rate are produced by SIMULATE-3. For the trending analysis, the data extracted from SIMULATE-3 was the three dimensional power distributions, the detector gamma signal and the nodal neutron reaction rate for platinum. FINC processed the measured signals correcting for the surface area to obtain results for a standard detector.

Post processing software and Excel spreadsheets were used to analyze the data. The following pieces of data were used in the trending analysis:

  • The measured signal, SM, from FINC corrected for surface area to correct to a standard 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 neutron reaction rate for platinum from SIMULATE-3 and collapsed by the post processing software over the detector length and axial location to obtain Rn.

  • Detector power was generated by the post processing software from the 3D nodal assembly power fraction from SIMULATE-3. The nodal assembly power fraction was collapsed over the detector length and axial location to generate a detector power in megawatts.

AREVA NP Inc. AI JP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensina Report Paae 41

  • Detector exposure was generated by the post processing software from the 3D nodal assembly exposure from SIMULATE-3. The nodal assembly exposure was collapsed over the detector length and axial location to generate a detector exposure in GWD/MTU. The detector exposure was accumulated to be current for each flux map.
  • A power independent measured detector signal was generated by the post processing software by dividing the measured signal, SM, by the detector power.
  • [

The 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.

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensing Report Paqe 42

" Failed detectors or detector strings were removed, i.e., no signal produced.

  • The analysis considered only original detectors for the determination of the NCF and DPC. Replacement detectors were incorporated into the figures to show consistency.
  • This resulted in 221,226 unique data points.

" A total of 145 anomalous flux maps were removed. Non-equilibrium flux maps and flux maps with an axial offset anomaly were removed in order to obtain a good estimate 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 trending for 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, the figures 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 versus detector exposure for the original detectors. Figure A- 2 shows the measured signal divided 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 both the original and replacement detectors. The trend shows changes due to changes in neutron and gamma spectrum during cycle burnup; changes from cycle to cycle due to core design and operating conditions; and changes due detector depletion.

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 43 Figure A- 3 shows the calculated gamma signal (ClY*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 versus detector exposure for the for the replacement detectors. The overall trend shows a decrease in the calculated gamma signal as a function of detector exposure for both the original and replacement detectors. The trend shows that the predictive model captures the effect of changes during the cycle, changes in core design and fuel management strategy and changes in operation conditions. The predictive model does not account for detector depletion.

Figure A- 5 shows the inferred neutron signal [ I divided by the detector power versus detector exposure for the original detectors. The overall trend shows a decrease in the inferred neutron signal as a function of detector exposure. Figure A- 6 shows the inferred neutron signal divided by the detector power versus detector exposure for the replacement detectors. Due to the short exposure time and the small number of replacement detectors, the overall trend shows no discernible decrease in the inferred neutron signal as a function of detector exposure.

To isolate the effect of detector depletion, the Neutron Conversion Factor (NCF) calculated from Equation 8 is used. Figure A- 7 shows the NCF versus detector exposure for the original detectors. The overall trend shows very slight decrease in the NCF as a function of detector exposure. From this data a linear relationship for the NCF was determined as NCF = A*E + B where E is the detector exposure in GWD/MTU and A and B are the constants of the linear equation. For comparison, Figure A- 8 shows 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 overall trend shows no discernible decrease or increase in the NCF as a function of detector exposure. It should be noted that the NCF for all detectors is derived from the original detectors only. Figure A-8 is intended to show the similarity in NCF between original and replacement detectors.

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 44 Figure A- 9 shows the calculated gamma signal divided by the measured signal as a function of detector exposure for the original detectors. From this figure it is clear that the gamma portion of the signal has been approximately 75% of the total signal. The refinement made in Cycle 9 to use the NCF rather than a straight 25% of the gamma portion of the signal more accurately represents the change in the neutron portion of the signal with changing core conditions. Figure A- 10 shows the calculated gamma signal divided 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 of the original detectors.

From the 15 cycles of trend data, there are observed trends in the measured signal, the calculated gamma signal, and the inferred neutron signal. [

I

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensing Report Paae 45

[

Figure A- 12 shows the difference between the predicted and measured signals for the original detectors using the proposed model. This figure shows there is no trend in the data with exposure and provides a basis for the proposed model.

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensing Report Page 46 Replacement detector strings were installed in Cycle 14 (Batch 1) and Cycle 15 (Batch 2). The replacement detectors were constructed to be similar to the original detectors, but are slightly less sensitive than the original detectors due primarily to changes in the manufacturing process. The change in sensitivity was noted and the FINC code was modified to introduce a batch dependent Gamma Correction Factor. As part of the trending analysis, the change in the Batch 1 and Batch 2 sensitivity was refined by comparing the measured signal from the replacement detectors to their symmetric partners of original detectors. The detector signals were corrected for depletion effects using the DPC from above. The comparisons are shown graphically in Figure A- 14 and Figure A- 15 for the Batch 1 detectors and in Figure A- 16 for the Batch 2 detectors.

Figure A- 13 shows the difference between the predicted and measured signals for the replacement 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 the bias 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 13 GCF = signal from Original Detector

  • DPC Signal from Replacement Detector
  • DPC Gamma Correction Factor for the replacement detectors is provided by detector batch and the GCF for Batch 1 is 1.0577 and the GCF for Batch 2 is 1.0849. These values with be input to FINC as constants to be applied to the Batch 1 and Batch 2 measured signals as simple multipliers.

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensinq Report Page 47 Figure A- I Measured Signal Divided by Detector Power versus Detector Exposure, Original Detectors

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 48 Figure A- 2 Measured Signal Divided by Detector Power versus Detector Exposure, Replacement Detectors I

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 49 Figure A- 3 Calculated Gamma Signal Divided by Detector Power versus Detector Exposure, Original Detectors I

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Paqe 50 Figure A- 4 Calculated Gamma Signal Divided by Detector Power versus Detector Exposure, Replacement Detectors I

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensing Report Page 51 Figure A- 5 Inferred Neutron Signal Divided by Detector Power versus Detector Exposure, Original Detectors I

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Pagqe 52 Figure A- 6 Inferred Neutron Signal Divided by Detector Power versus Detector Exposure, Replacement Detectors

[

I

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensing Report Page 53 Figure A- 7 Neutron Conversion Factor versus Detector Exposure, Original Detectors I

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensing Report Page 54 Figure A- 8 Neutron Conversion Factor versus Detector Exposure, Replacement Detectors I

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 55 Figure A- 9 Calculated Gamma Divided by Measured Signal versus Detector Exposure, Original Detectors I

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensing Report Page 56 Figure A- 10 Calculated Gamma Divided by Measured Signal versus Detector Exposure, Replacement Detectors I

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 57 Figure A- 11 Depletion Correction Factor

[

I

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensina Reoort Paae 58 Figure A- 12 Difference between Predicted and Measured Signals, Original Detectors, Proposed Model I

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensing Report Page 59 Figure A- 13 Difference between Predicted and Measured Signals, Replacement Detectors, Proposed Model I

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 60 Figure A- 14 Ratio of Measured Signals for Original to Replacement Detectors, Batch 1, Cycle 14 I

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1 855PA Licensing Report Page 61 Figure A- 15 Ratio of Measured Signals for Original to Replacement Detectors, Batch 1, Cycle 15 I

AREVA NP Inc. ANP-3243NP Revision 0 Seabrook Station Unit 1 Fixed Incore Detector System Analysis Supplement to YAEC-1855PA Licensing Report Page 62 Figure A- 16 Ratio of Measured Signals for Original to Replacement Detectors, Batch 2, Cycle 15

ATTACHMENT 5 Marked-up Technical Specification Bases Page (Provided for information only)

POWER DISTRIBUTION LIMITS BASES 3/4.2.2 and. 3/4.2;3 HEAT FLUX HOT CHANNEL FACTOR and NUCLEAR ENTHALPY RISE HOT CHANNEL FACTOR (Continued)

FA will be maintained within Its limits provided Conditions a. through d. above are maintained. Margin is maintained between the safety analysis limit DNBR and the design limit plant DNBR.

design There Is additional margin.avallabie to offset any other DNBR penalties and for flexibility. (

When an FQ (Z) measurement is taken, an allowance for both measurement error and manufacturing tolerance must be made. An allowanc.of 5% Is appropriate for a full-core map taken with the movable Incore detectors, whil .% Is appropriate for surveillance results determined with the fixed Incore detectors. A 3A/, allowance Is appropriate for manufacturing tolerance.

The hot channel factor F.(Z) Is measured periodically and Increased by a cycle and height dependent power factor appropriate to Relaxed Axial Offset Control (RAOC) operation, W(Z), to provide assurance that the limit on the hot channel factor FQ(Z) is met.

W(Z) accounts for the effects of n6rmal operation transients and was determined from expected power control maneuvers over the full range of burnup conditions Inthe core. The W(Z) function for normal operation Is specified in the CORE OPERATING LIMITS REPORT per Specification 6.8.1.6.

When RCS FA, Is measured, no additional allowances are necessary prior to comparison with.the established limit. Appropriate Fmeasurement uncertainties are already Incorporated Into the limits FAI established in the CORE OPERATING LIMITS REPORT for each measurement system, and a bounding F*t measurement uncertainty has been applied Indetermination of the design DNBR value. The appropriate FXf measurement uncertalinties are.  % for the fixed Incore detector system and 4% for the movable Incore detector system-M,42.4 QUADRANT POWER TILT RATIO The purpose of this specification Is to detect gross changes in core power dis(ribullon between monthly Incore Detector System-surveillances. During normal operation the QUADRANT POWER TILT RATIO Is set equal to 1.0once acceptability of core.peaking factors has been established by review of Incore surveillances. The limit of 1.02 Is established as an Indioatlon that the power distribution has changed enough to warrant further investigation.

SEABROOK - UNIT I B 3/4 2-3 Amendment No. a ,2, 27, 33, 70, 76,

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