ML063400456
| ML063400456 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 11/20/2006 |
| From: | Hamer M Entergy Corp |
| To: | Rowley J NRC/NRR/ADRO/DLR |
| References | |
| GE-NE-0000-0007-2342-R1, TAC MD2297 | |
| Download: ML063400456 (42) | |
Text
Richard Emch - GE Analysis Page 1
.PA-Li _
From:
"Hamer, Mike" <mhamer@entergy.com>
To:
"Jonathan Rowley" <JGR@nrc.gov>
Date:
Mon, Nov 20, 2006 4:53 PM
Subject:
GE Analysis
- Jonathan, The analysis [GE-NE-000-0007-2342-R1] that was cited in an RAI response and requested during a teleconference was previously submitted to the NRC in 2003 as BVY 03-066 for TS Proposed Change No. 258. Please see attached.
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Docket No. 50-271 BVY 03-66 Vermont Yankee Nuclear Power Station Technical Specification Proposed Change No. 258 Additional Information Entergy Northeast Vermont Yankee Neutron Flux Evaluation (NON-PROPRIETARY INFORMATION)
GE Nuclear Energy General FJectric Company 175 Curtner Avenue. San Jose CA 95125 GE-NE-0000-0007-2342-R1-NP DRF 0000-0007-2342 Revision 1 Class I July 2003 Final Report Entergy Northeast Vermont Yankee Neutron Flux Evaluation Principal Contributor:
Tang Wu Principal Verifiers:
S. S. Wang, H. A Careway Technical Projects Manager:
David J. Robare
GE-NE-0000-0007-2342-RI-NP IMPORTANT NOTICE REGARDING THE CONTENTS OF THIS REPORT Please Read Carefully A. Disclaimer The only undertakings of the General Electric Company (GE) respecting information in this document are contained in the contract between the company receiving this document and GE. Nothing contained in this document shall be construed as changing the applicable contract. The use of this information by anyone other than a customer authorized by GE to have this document, or for any purpose other than that for which it is intended, is not authorized. With respect to any unauthorized use, GE makes no representation or warranty, and assumes no liability as to the completeness, accuracy or usefulness of the information contained in this document, or that its use may not infringe privately owned rights.
R Information Notice This is a non-proprietary version of the document GE-NE-0000-0007-2342-R1-P, which has the proprietary information removed. Portions of the document that have been removed are indicated by an open and closed bracket as shown here B.
i
GE-NE-OOOO-0007-2342-R1-NP TABLE OF CONTENTS Page ACRONYMS AND ABBREVIATIONS... ---
1.0 1
2.0
SUMMARY
AND CONCLUSIONS.
2.1 M ETHODOLOGY...................................................................................................
2 2.2 NEtRoN FLUX FOR CYCLES 9 AND 8...........................................................
2 2.3 NEMURON FLUX FOR MODERN CORES............................................................
3 2.4 NEM ON FLUENCE.......................................................................................
3 3.1 SV LUTONPE.....................
4 3.1 SCOPE.................................
4 3.2 INPuTs AND AssuwnoNs...........................................................................
4 3.3 METHOD OF EVALUATiON..............................................................................
4 3.3.1 Core Loading.........................................................................................
5 3.3.2 (R, ) M odel...........................................
.................................................... 6 3.3.3 (R,Z) M odel...................................................................................................
7 3.3.4 Material Composition and Coolant Density..............................................
7 3.3.5 Neutron Source Distribution....................................................................
8 3.4 BiAs A MN UNCERTAINTY...............................................................................
9 4.0 FLUX RESULTS FOR CYCLES 9 AND 8.................................
4,1 NEUTRON FLUX AT RPV INSIDE SURFACE....................................................
17 4.2 NEUTRON FLUX AT SURVEILLANCE CAPSULE LOCATION............................ 17 4.3 NEUTRON FLUX AT SHROUD INSmE SURFACE............................................
17 4.4 NEUTRON FLUX
SUMMARY
18 5.0 FLUX RESULTS FOR MODERN CORES......
........................... 24 5.1 NEUTRON FLUX AT RPV INSIDE SURFACE...............................
24 5.2 NEUTRON FLUX AT SURVEILLANCE CAPSULE LOCATION............................ 24 5.3 NEUTRON FLux AT SHROUD INSIDE SURFACE...........................................
24 5.4 NEUTRON FLUX
SUMMARY
25 5.5 AssEssMm T OF CYCLE 23..........................................................................
26 6.0 NEUTRON FLUENCF
.... 33
7.0 REFERENCES
35 11
GE-NE-O00-0007-2342-R I-NP LIST OF TABLES Table Title Page Table 3-1 Design Input Data for Flux Calculation (Entergy Verified).............................
10 Table 4-1 Comparison of RPV Flux and Shroud Flux - Cycles 9 and 8...........................
19 Table 4-2 Comparison of 30* Capsule Flux.....................................
19 Table 5-1 Summary of Flux Results-Cycle 21.....................................
25 LIST OF FIGURES Title Page Figure 3-1.
Figure 3-2.
Figure 3-2.
Figure 3-3.
Figure 3-4.
Figure 3-5.
Figure 4-1.
Figure 4-2.
Figure 4-3.
Figure 4-4.
Figure 5-1.
Figure 5-2.
Figure 5-3.
Figure 5-4.
Figure 5-5.
Figure 5-6.
Figure 6-1.
Core Layout and Vessel Internal Components....................
12 Schematic of (RZ) M odel............................................................................
12 Schematic of (RZ) M odel.............................................................................
13 Relative Energy by Bundle at Core Midplane - Cycle 21..............................
14 Relative Energy by Bundle at Core Midplane - Cycle 9...............................
15 Relative Energy by Bundle at Core Midplane - Cycle 8..............
16 Azimuthal Distribution of Fast Neutron Flux at RPV Inside Surface at Peak Elevation - Cycles 9 and 8........................................................................
20 Axial Distribution of Fast Neutron Flux at RPV Inside Surface - Cycles 9 and 8................................................................................................................
21 Azimuthal Distribution of Fast Neutron Flux at Shroud Inside Surface at Peak Elevation - Cycles 9 and 8..............................................................
22 Axial Distribution of Fast Neutron Flux at Shroud Inside Surface - Cycles 9 and 8.................................................................................................................
23 Azimuthal Distribution of Fast Neutron Flux at RPV Inside Surface at Peak Elevation - Cycle 21..................................................................................
27 Axial Distribution of Fast Neutron Flux at RPV Inside Surface - Cycle 21....... 28 Azimuthal Distribution of Fast Neutron Flux at Shroud Inside Surface at Peak Elevation - Cycle 21........................................................................
29 Axial Distribution of Fast Neutron Flux at Shroud Inside Surface - Cycle 21...30 Axial Power Profiles of the Dominant Bundles....................
31 Relative Energy by Bundle at Core Midplane - Cycle 23.............................
32 Axial Distribution of 32-EFPY Fast Neutron Fluence at RPV Inside Surface....34 iii
GE-NE-0000-0007-2342-R 1-NP ACRONYMS AND ABBREVIATIONS BAF Bottom of Active Fuel BOC Beginning of Cycle ECP Engineering Computer Program EFPY Effective Full-Power Years ENDF Evaluated Nuclear Data File ENVY Entergy Northeast Vermont Yankee EOC End of Cycle GE General Electric GE-NE General Electric Nuclear Energy GNF Global Nuclear Fuel IASCC Irradiation Assisted. Stress Corrosion Cracking II)
Inside Diameter LTR Licensing Topical Report MOC Middle of Cycle MWt Megawatt Thermal NRC Nuclear Regulatory Commission OD Outside Diameter ORNL Oak Ridge National Laboratory RG Regulatory Guide RPV Reactor Pressure Vessel iv
GE-NE-0000-0007-2342-R I-NP
1.0 INTRODUCTION
Neutron irradiation of the reactor pressure vessel (RPV) causes reduction in material ductility and creates structural embrittlement at higher operating temperatures. The effect is particularly significant when impurities such as nickel, copper, or phosphorus are present in noticeable levels, as is commonly true for the RPV steel. Therefore determination of neutron fluence level is one of the first steps toward RPV fracture toughness evaluations.
Irradiation by fast neutrons (with energies greater than I MeV) can also be a concern with respect to irradiation assisted stress corrosion cracking (IASCC) for reactor internal components such as core shroud, top guide, core plate, etc. Crack growth evaluation for these components also requires adequate determination of neutron fluence level.
Neutron flux, or fluence rate, can be determined through radiochemical analysis of the surveillance flux wire samples; which are made of iron, copper, or nickel, sealed inside a capsule and held in place by a holder near the RPV inside surface. The calculated ratio of surveillance sample flux to the RPV peak flux defines a lead factor. This lead factor can be applied to the sample dosimetry data to determine the RPV peak flux.
Neutron flux can also be determined by solving the Boltzmann neutron transport equation with the discrete ordinates method or Monte Carlo simulation. When appropriate bias is applied to the calculation results, these numerical methods can be used to obtain the best-estimate flux distribution.
The first objective (Task 1) of this work is to evaluate the capsule flux and neutron flux distributions at the RPV and at the shroud for the period during which the last removed capsule was resident in the Entergy Northeast Vermont Yankee (ENVY) plant. The second objective (Task 2) is to evaluate the flux distributions at the RPV"and at the shroud for a representative modern core to determine the impact of core and fuel design changes that have occurred since the capsule removal.
Once the neutron flux is determined, the lifetime fluence can be determined by integrating the fluxes over the total irradiation period.
I
GE-NE-0000-0007-2342-R1-NP 2.0
SUMMARY
AND CONCLUSIONS 2.1 Methodology The methodology used for the neutron flux calculation is documented in the GE's Licensing Topical Report (LTR) NEDC-32983P-A [1], which was approved by the U.S.
NRC for licensing applications in the Safety Evaluation Report [2].
In general, GE's methodology described in the LTR adheres to the guidance in Regulatory Guide (RG) 1.190 [3] for neutron flux evaluation. In this evaluation, the fast neutron flux distribution is calculated based on the three-dimensional flux synthesis of two separate two-dimensional flux solution calculations performed in an (rz) and an (r",)
model._ These flux solution calculations are performed using the two-dimensional discrete ordinates code DORTG01V, which is a controlled version of DORT in the GE Engineering Computation Program (ECP) library [4].
2.2 Neutron Flux for Cycles 9 and 8 Task I of this evaluation is based on the core data from Cycles 8 and 9, at the end of which the surveillance capsule was removed from the plant. The analysis inputs and core data have been provided by Entergy through concurrence and transmittals [5, 6]. The core power used is 1593 MWt.
The calculated peak fast flux (E>1 MeV) at the RPV inside surface is 2.97E8 n/cm2-s for Cycle 9 and 2.70E8 n/cm2-s for Cycle 8. The peak flux for the first quadrant is located at the azimuth of 0° and at the elevation of 92 and 96 inches above the bottom of the active fuel (BAF), respectively for Cycle 9 and Cycle 8. Fluxes for other quadrants are expected to be similar due to quadrant symmetry of the core design as well as the arrangement of vessel internal components.
I]
The peak fast flux-for the shroud inside surface (nominal ID) is 8.38E10 n/cm2-s for Cycle 9 and 7.78E10 n/cm2-s for Cycle 8. The peak flux for the first quadrant is located at the azimuth of 90' for Cycle 9 and 830 for Cycle 8. The peak elevation is 98 and 102 inches above the BAF, respectively for Cycle 9 and Cycle 8.
2
GE-NE-0000-0007-2342-RI-NP 2.3 Neutron Flux for Modern Cores Neutron flux for the ENVY modem core is evaluated based on Cycle 21 core data.
The calculated peak fast flux at the RPV inside surface is 2.96E8 r/cm2-s. The peak flux for the first quadrant is located at the azimuth of 00 and at the elevation of 84 inches above the BAF.
((
]
The peak fast flux for the shroud inside surface (nominal ID) is 8.17E10 n/cm2-s.
The peak flux is located -at the azimuth of 83°and the peak elevation is 89 inches above the BAF.
It is concluded that flux levels from Cycle 21 are comparable to the average values of Cycles 9 and 8. Thus, Cycle 21 fluxes can be used to provide a conservative estimate of the time-integrated neutron fluences over the plant life.
Assessment of impact on flux levels for Cycle 23, which contains fuel bundles with part-length rods in the core periphery, is also performed. Comparison of power density of the governing peripheral bundles between Cycle 23 and Cycle 21 indicates that Cycle 23 fluxes will be bounded by Cycle 21.
2.4 Neutron Fluence Cycle 21 fluxes are used to provide a conservative estimate of the neutron fluences at the end of plant life of 32 and 54 EFPY. The peak 32-EFPY fluence is 2.99E17 n/cm2 at the RPV inside surface and 8.25E19 n/cm2 at the shroud inside surface. The peak 54-EFPY fluence is 5.04E17 n/cm2 at the RPV inside surface and 1.39E20 n/cm2 at the shroud inside surface. The axial distribution of the RPV fast neutron fluences indicates that the 32-EFPY fluence greater than 1.0E17 n/cm2 is confined to the active fuel zone.
GE-NFO000-0007-2342-R 1-NP 3.0 EVALUATION 3.1 Scope Fast neutron fluxes in the beltline region extending from the core through the RPV are calculated in this analysis. Task I of this work is to evaluate the capsule flux and neutron flux distributions at the RPV and at the shroud for the period during which the last removed capsule was resident in the ENVY plant Since the capsule was removed after shutdown on March 1983 (End of Cycle 9) [7], the core data that are important for this calculation are those of Cycle 9 and Cycle 8.
Task 2 of this work is to evaluate the flux distributions at the RPV and at the shroud for a representative modem core to determine the impact of core and fuel design changes that have occurred since the capsule removal. This flux evaluation will be based on the Cycle 21 core data, based on the agreement between GE and Entergy as part of the Design Input Request [5].
Once the neutron flux is determined, the neutron fluence at the end of plant life can be determined by integrating the fluxes over the irradiation time.
3.2 Inputs and Assumptions The operating condition assumed for this analysis is based on the specific core design data of the cycles of interest. For the older cycles, core data have been provided by Entergy [6].
For the modem core, core data were retrieved and processed from GE's Engineering Data Bank. Core data that are pertinent to the flux calculations include core loading, bundle types, bundle heavy metal mass, and void fraction (or water density) and fuel exposure data. The currently licensed power is 1593 MWt The RPV and shroud dimensions, together with the configuration and location of surveillance capsule holder, are provided in Reference 6 and shown in Table 3-1.
3.3 Method of Evaluation The methodology used for the neutron flux calculation is documented in a Licensing Topical Report (LTR) NEDC-32983P-A [1], which was approved by the U.S. NRC in the Safety Evaluation Report for referencing in licensing actions [2].
In general, GE's methodology described in the LTR adheres to the guidance in Regulatory Guide 1.190 [3] for neutron flux evaluation.
4
GE-NE-0000-0007-2342-R I-NP This synthesis approach is consistent with the GE approved methodology.
The flux calculations are performed with DORTG01V, which is a controlled version of DORT in the GE Engineering Computation Program (ECP) library [4]. The NRC has approved the use of DORT as part of the GE methodology [2].
The cross-section data used in the DORT calculation are processed with the nuclear cross-section processing package [Ref. 9] in the GE ECP. ((
))
A P3 truncation of the Legendre polynomial expansion, which meets Regulatory Position 1.1.2 in RG 1.190, is used to approximate the anisotropy in the differential scattering cross sections.
The approach discussed here is consistent with the approved LTR methodology.
The cross section library used in the GE ECP is based on Version V of the Evaluated Nuclear Data File (ENDF/B-V). However, cross sections for the important components of BWR neutron flux calculation - oxygen, hydrogen, and individual iron isotopes - have been upgraded to ENDF/B-VI to meet the guidelines of Regulatory Guide 1.190.
3.3.1 Core Loading Cycle 21 is a modem core. The core load contained 220 bundles of GEI3 and 148 bundles of GE9B. GE13 contains both full-length and part-length fuel rods. GE9B contains only full-length fuel rods. Fuel bundles in the outermost row contained only GE9B fuel bundles.
5
GE-NE-0000-0007-2342-R 1-NP Cycle 9 core load contained 356 bundles of GE6 and 12 bundles of GE4.
Fuel bundles in the outermost row were GE6 and GE4 [Ref. 6].
Cycle 8 core load contained 236 bundles of GE6 and 132 bundles of GE4 at various enrichment. Fuel bundles in the outermost row were all GE4 [Ref. 6].
3.3.2 (R,0) Model Figure 3-1 shows a quadrant of the core and the vessel internal components that are relevant to the flux calculation. ((
I]
The (r,0) analysis used the polar coordinates to define the calculation model as a planar sector between reactor azimuths 00 and 90'. ((
I]
ENVY installed the shroud restraint tie rods during the 1996 Refueling Outage [Ref.
5]. These tie rods have been present since the beginning of Cycle 19. These rods have an outer diameter of 4 inches and were placed at the radial location of 3.625 inches from the inner vessel wall in each of the 450, 1350, 2250, and 3150 azimuths. These tie rods were modeled as homogenized cylinder, with a steel area fraction of 93%.
In the angular coordinate 0, the mesh size is 1/2 degree per mesh interval, except for the two boundary nodes, which is 1/4 degree. For a core quadrant, a total of 181 fine meshes are used in the 0-direction. This model is more detailed than the minimum requirement of 40 intervals per octant stipulated in Section 1.3.1. of RG 1.190.
Radial meshes vary in sizes. Generally, a fine mesh is provided near material interfaces, where significant flux gradients are expected. Fine meshes are also applied near the shroud and the capsule. Sufficient fine mesh steps are provided to simulate the outer boundary profiles of the core. The mesh step is fine enough such that the actual core boundary can be approximated to the nearest 0.8 cm. ((
6
GE-NE-0000-0007-2342-R I-NP
))
The (r,0) calculation is performed for the first quadrant of the reactor. The model includes three sets ofjet-pump/hiser, which are centered at 30*, 600, and 900. It also includes the 300 capsule, which is completely shadowed by the jet-pump riser, and the shroud restraint tie rod at 450 for the modern cores. The azimuthal distribution of RPV flux in the first quadrant is expected to be representative of other quadrants because of the quadrant symmetry in the power distribution. The RPV flux at 0 and 180 degrees is expected to be higher than that at 90 and 270 degrees, due to the absence ofjet pumps.
3.3.3 (RZ) Model II 1]
3.3.4 Material Composition and Coolant Density Material compositions in each calculation model are treated as homogeneous mixtures. The volume fractions of solid material in the three core regions are calculated based on specific fuel bundle design data. [
))
GE-NE-0000-0007-2342-R 1-NP
[II 11 3.3.5 Neutron Source Distribution The energy produced per fission and the neutron yield data that are representative of the cycle were obtained from TGBLA calculations. These data are then used to generate the total neutron source in the core.
Spatial distribution of the neutron source density is simulated based on relative cycle-integrated energy production.
((
1))
Figures 3-3, 3-4, and 3-5 show the bundle-dependent relative cycle energy (normalized to the core average) at core midplane elevation (axial node 13) for Cycles 21, 9, and 8, respectively. These discrete data in the (xy) plane are processed to form the neutron source distribution in the (rO) meshes for the (rO) calculation. The power densities of the peripheral bundles near the azimuth of the peak RPV or shroud fluxes have a direct impact on the shroud and RPV flux levels.
((
8
GE-NE-0000-0007-2342-RI-NP 3.4 Bias and Uncertainty These values are included in Section 4.4 and 5.4 for comparison purpose only. The bias and uncertainty associated with these values have not been assessed.
9
GE-NE-0000-0007-2342-RI-NP Table 3-1 Design Input Data for Flux Calculation (Entergy Verified)
(A) Surveillance CapsuleBasket Thickness 0.895 117C4335P1 Width 7.06 max 117C4335P 1 Length 13.275 117C4335P1, 129B3157P1 Azimuths, degrees 30, 120,300 921D514 Radial Position of Basket Center, from RPV 0.875 919D294, 129B3157P1 Clad Elevation of Basket Center, above BAF 73.6975 919D294, 117C4335P1.
(B) RPV (Beltline)
RPV Base Metal ID 205.25 104R940 RPV Thickness 5.064 Figure 7 of Battelle Report BCL-585-84-3, May 15, 1984.
RPV Clad Thickness 0.125 UFSARRev.17 Section 4.2.4.1 (C) Shroud (Active Fuel Region)
Shroud ID 163.75 nom 729E956 Shroud Thickness 1.75 729E956 (D) Jet Pump Components Recire. Inlet Nozzles Azimuths, degrees 30, 60, 90, 120, 150, 919D294 Sh 2 (VPF1842) 210, 240, 270, 300, 330 Jet Pump Riser Pipe 10" Sch 40 719E1 13 Jet Pump Inlet Mixer OD 6.625 719E113 Jet Pump Inlet Mixer ID 6.07 920D278 Radial Location of Riser from Core Center 91.844 919D294 Sh 3 10
GE-NE-0OOO-007-2342-Rl-NP Radial Offset, Mixer to Riser 0.32 719EI'13 Radial Location of Mixer from Core Center 92.382 Derived Distance between Mixers, centerline to 25.125 919D294 Sh 3 centerline (E) Top Guide Beam Upper Elevation 370.25 104R940 Lower Elevation 358.75 104R940 (F) Core Plate Upper Elevation 198.56 104R940 Thickness 2
729E957 Elevation of top of core plate support flange 184.56 104R940 (G) Other Core Data Thermal Power 1593 MWt UFSAR Rev. 17 Table 317.1 Elevation of Bottom of Active Fuel (BAF) 207.5 104R940 Density of Bypass Water between Shroud and 0.738 g/cm3 Saturated water at PL1=1025 psia, Tgt=547.560F Fuel Bundles Density of Downcomer Water 0.760 g/cm3 Subcooled (201F) water 11
GE-NE-0000-0007-2342-R 1-NP Figure 3-1. Core Layout and Vessel Internal Components 00 J
2 3
4 5
6 7
8 9
10 11 I
90P 12 13 14 15 16 17 18 19 20 21 22
,-1 12
GE-NE-0000-0007-2342-RI-NP Figure 3-2. Schematic of (RZ) Model
- [F I]
13
GE-NE-0000-0007-23342-RI-NP Figure 3-3. Relative Energy by Bundle at Core Midplane - Cycle 21 J=
1 2
3 4
5 6
7 8
10 11 I=
12I[0-6426 13 0.5524 14 0.47-57 15 16 17 18 19 20 21 22 1.2613 1.1466 1.0266 0.6314 1.3561 1.4504 1,2836 1.1501 0.7873 0.5657 0.4749 1.5451 1.1986 1.5154 1.3346 1.2106 1.0834 0.9354 0.5655 1.2038 1.5989 1.4743 11.5755 1.3679 1.0210 1.1912 0.9381 0.4851 1.4851 1.2213 1.5996 1.2363 1.5448 1.3293 1.0250 1.0878 0.5703 1.1089 1.3433 1.1594 1.5079 1.1591 1.5525 1,3742 1.2161 0.8036
-4.
-44.
~
I 4-...-4
-4.-I 1.4337 1.1034 1.4656 1.3562 1,5263 1.2452 1.5811 1.3395 1.1524 0.6222 1.1222 1.4330 1.1354 1.5151 1,2211 1.6216 1.4828 1.5188 1.2810 1.0254 0.5175 1.3532 1.1214 1.4522 1.1601 1.4033 1.2307 1,6013 1.1948 1.4466 1.1412 0.5471 1.1563 1.3571 1.1257 1.4710 1.1425 1.4773 1.1833 1.5352 1.3500 1.2553 0.6285 14
GE-NE-0000-0007-2342-RI-NP Figure 3-4. Relative Energy by Bundle at Core Midplane - Cycle 9 J=
1 2
3 4
5 6
7 8
9 10 11 I=
12 13 0.5300 14 0.4590 15 16 17 18 19 20 21 22 1.0230 0.9586 0.8842 0.5987 4.-
I -
I -
I ~3~
1.1234 12056 1.0573 1.0488 0.8784 0.621610.4947 12946 1.2116 1.3003 1.2216 1.1657 1.0251 0.8785 0.5810 1.1433 1.3655 12543 1.3806 1.2271 1.2508 1.0286 0.8784 0.5005 1.3100 12464 1.3974 1.3081 1.3921 12571 12519 1.0276 0.6204 1.1117 1.3287 12444 1.4173 1.3214 1.3897 12264 1.1714 0.8825 1.2795 1.2129 1.3449 1.2976 1.4331 1.3215 1.3912 1.2337 1.0580 0.6008 1.0992 1.2855 1.2149 1.3855 1.2950 1.4599 1.3022 1.3211 1.0658 0.8916 0.4661 1.2416 1.1151 1.2971 1.2563 1.3949 1.3121 1.4272 1.2295 1.2181 0.9630 0.5311 1.0608 12323 1.0996 1.3118 1.1530 1.3632 1.1793 1.3171 1.1215 1.0286 0.6848 15
GE-NE-O00O-0007-2'342-R 1-NP Figure 3-5. Relative Energy by Bundle at Core Midplane - Cycle 8 I=
12 13 14 15 16 17 18 19 20 21 22 0.552210.499210.4695 1.0021 0.9568 0.8858 0.5942 I
I II
-II V
1.0513 1.2197 1.1594 1.0169 0.715110.5584 1 0A364 I
J I 1.3715 1.2677 1.3355 1.1509 1.1 147 0.9061 0.8292 0.4728 12968 1.5019 12777 1.3904 1.1216 1.2040 1.0027 0.8304 0.4441 1.5073 1.4201 1.5356 1.3419 1.4193 1.2044 12066 0.9100 0.5561 1.4755 1.3241 1.5551 1.3167 1.4279 1.1302 1.1211 0.7144 1.3724 1.3422 1.4895 1.4338 1.5792 1.3611 1.4079 1,1620 1.0272 0.5960 12138 1.4005 12386 1.5970 1.4492 1.5772 1.3281 1.3577 1.1766 0.8999 0.4779 1.3978 1.3069 1.4393 1.4812 1.6482 1.4817 1.5427 1.2988 12456 0.9741 0.5130 1.1135 1.3840 12353 1.5868 1.4585 1.6097 1.3698 1.4148 1.0801 1.0218 0.5671 16
GE-NE-0000-0007-2342-R 1-NP 4.0 FLUX RESULTS FOR CYCLES 9 AND 8 4.1 Neutron Flux at RPV Inside Surface The calculated peak fast flux (E>1 MeV) at the RPV inside surface is 2.97ES n/cm2-s for Cycle 9 and 2.70E8 n/cm2-s for Cycle 8. The azimuthal flux profile for the RPV is illustrated in Figure 4-1. The averaged flux values are based on the weighting of cycle specific EFPY - 1.14 EFPY for Cycle 9 and 0.76 EFPY for Cycle 8. The peak flux-for the first quadrant is located at the azimuth of 00. The effects of inelastic scattering by steel in the jet-pump components are clearly displayed in Figure 4-1, where the flux depression occurs in regions shadowed by metal components. The flux level at 900 is slightly lower than its mirror image at 0° due to the shadowing effect of the jet-pump riser at 900. Fluxes for other quadrants are expected to be similar due to quadrant symmetry of the core design as well as the arrangement of vessel internal components.
Axial flux variation at the RPV inside surface is shown in Figure 4-2. The elevation of peak flux occurs at 92 and 96 inches above the BAF for Cycle 9 and Cycle 8, respectively.
The ratio of peak flux to midplane (75 inches above the BAF) flux is 1.016 and 1.036, respectively.
4.2 Neutron Flux at Surveillance Capsule Location 4.3 Neutron Flux at Shroud Inside Surface The calculated peak fast flux (E>1 MeV) at the shroud inside surface (nominal ID of 163.75 inches) is 8.38E10 n/cm2-s for Cycle 9 and 7.78E10 n/cm2-s for Cycle 8. The azimuthal flux profile for the first quadrant of the shroud is illustrated in Figure 4-3. The peak flux is located at the azimuth of 90' for Cycle 9 and 830 for Cycle 8. The variation of the peak azimuth is due to the core layout for the ENVY plant and the relative bundle power for the governing peripheral bundles. In fact, peak azimuth for the shroud is not distinctly defined as the flux variation in the range of 00 - 10' and 80' - 900 is less than 4%. Flux distributions for the other three quadrants are expected to be similar due to quadrant symmetry of the core design.
17
GE-NE-0000-0007-2342-RI-NP Axial flux variation at the shroud inside surface is shown in Figure 4-4.
The elevation of peak flux occurs at 98 and 102 inches above the BAF for Cycle 9 and Cycle 8, respectively. The ratio of peak flux to midplane flux is 1.028 and 1.055, respectively.
4.4 Neutron Flux Summary A summary of fast fluxes, including the peak flux at the l/4T and 3/4T of the RPV, is shown in Tables 4-1 and 4-2. Also included is a comparison with the previous results from the Battelle calculation [7]. The 1/4T and 3/4T fluxes are results from flux calculations and not derived values based on Reg Guide 1.99 and are presented for comparison purpose only.
The calculation uncertainty and bias of the 1/4T and 3/4T fluxes have not been assessed.
((
))
the measured flux of 1.80ES+/-0.14E8 n/m 2-s (2a uncertainty),
with a
[] The peak RPV flux of2.86E8 n/cm 2-s is significantly higher than the Battelle calculation of 2.18E8 n/oa 2-s. The following are possible explanations for this difference:
- 1. The mesh size used in the GE calculation is significantly finer than the Battelle model.
- 2. Battelle calculation was based on the integrated power of Cycle I through Cycle 9, while GE calculation was based on Cycles 8 and 9 only.
- 3. (GR uses ENDF/B-VI cross sections, while Battelle calculation was based on the cross section data from the early 1980s.
18
GE-NE-0OOO-0007-2342-RI-NP Table 4-1 Comparison of RPV Flux and Shroud Flux - Cycles 9 and 8 Battelle Calculation Cycle 9 Cycle 8 C8-C9 Avg.
Peak RPV Flux (>1 Mey).
Inside Surface 2.18E8 2.97E8 2.70E8 2.86E8 1/4T 1.59E8 2.05E8 1.87E8 1.98E8 3/4T 6.23E7 8.57E7 7.80E7 8.26E7 Peak Shroud Flux 8.38E+10 7.78E+10 8.11E+10 Table 4-2 Comparison of 30* Capsule Flux Battelle Measured GE*
GE-Battelle Flux (+2g)..
Difference Fast Flux 1 Me) 1.80E8+/-0.14E8 19
GE.-NE-0000-0007-2342-RI-NP Figure 4-1. Azimuthal Distribution of Fast Neutron Flux at RPV Inside Surface at Peak Elevation - Cycles 9 and 8 Azimuthal Distribution of Fast Flux (E>IMeV) at Peak Elevation - Vermont Yankee X
U-0LL Z
3.5E+08 3.OE+08 2.5E+08 2.OE408 1.5E+08 I.OE+08 5.OE+07 O.OE+00 0
10 20 30 40 50 60 Azimuth (degrees past Quadrant Reference) 70 80 90 20
GYE-NE-0000-0007-2342-Rl-NP Figure 4-2. Axial Distribution of Fast Neutron Flux at RPV Inside Surface - Cycles 9 and 8 Axial Distribution of Relative Fast Flux (EMt MeV) - Vermont Yankee 1.1 1.0o 0.9 0.7
§ 0.6 E
0.5 0.4
..... RPV ID, C9, PeakiMidplane=1.016 0.2-RPV ID, C8, Peak/Mldplane=1.036 0.1 RPV ID, C8-C9 Avg., Peak/Midplane=1.023 0.0-
-25 0
25 50 75 100 125 150 175 Elevation Above BAF (inches) 21
GE-NE-0000-0007-2342-Rl-NP Figure 4-3. Azimuthal Distribution of Fast Neutron Flux at Shroud Inside Surface at Peak Elevation - Cycles 9 and 8 Azimuthal Distribution of Fast Flux (E>1 MeV) at Peak Elevation -Vermont Yankee 9.OE+ 0 C
0 t:.;5 0
10 20 30 40 s0 60 Azimuth (degrees past Quadrant Reference) 70 8Q 90 22
GE-NE-0OOO-0007-2342-Rl-NP Figure 4-4. Axial Distribution of Fast Neutron Flux at Shroud Inside Surface - Cycles 9 and 8 Axial Distribution of Relative Fast Flux (E>M MeV) - Vermont Yankee 1.1 1.0 J
0.9 0.8 0.7 X
0.6 0.5 0.4 0.3 Shroud ID, 09, PealRMIdplane=l.028 0.2 Shroud ID, 08, PeaiWMIdplane=1.055j 0.1
-Shroud ID, CB-C9 Avg., PeakIMIdplane=1.038 0.0
--'----'--I---
-25 0
25 50 75 100 125 150 175 Elevation Above BAF (Inches) 23
GE-NE-000-0007-2342-R 1-NP 5.0 FLUX RESULTS FOR MODERN CORES Cycle 21 has been selected as a representative cycle for the modem core design. The selection of Cycle 21 to represent the modem cores, as agreed by ENVY as part of the Design Input Request, was based on a review of the core design data of a number of recent cycles, which concluded that Cycle 21 flux would bound the average of the modem cores.
Flux results for Cycle 21 are documented in this section. The flux results for the average of Cycles 9 and 8 are also shown for a one-on-one comparison. An assessment of Cycle 23, which contains fuel bundles with part-length rods in the core periphery, is also presented here.
5.1 Neutron Flux at RPV Inside Surface The calculated peak fast flux (E>1 MeV) at the RPV inside surface is 2.96E8 n/cm2-s
-for Cycle 21. This flux value is nearly identical to that of Cycle 9. The azimuthal flux profile for the RPV is illustrated in Figure 5-1 for the cases with and without the tie rods included in the model. The peak flux for the first quadrant is located at the azimuth of 00.
The flux level at 900 is slightly lower than that at 00 due to the shadowing effect of the jet-pump riser at 900.
The effect of the shroud restraint tie rods at the 450 azimuth in this quadrant, which were installed during 1996, is clearly shown in Figure 5-1.
The flux depression is maximized at about 25% at 450 and then gradually reduced to insignificant amount beyond the range of 401 - 600.
Axial flux variation at the RPV inside surface is shown in Figure 5-2. The elevation of peak flux occurs at 84 inches above the BAF. The ratio of peak flux to midplane (75 inches above BAF) flux is 1.008.
5.2 Neutron Flux at Surveillance Capsule Location I((
5.3 Neutron Flux at Shroud Inside Surface The calculated peak fast flux (E>1 MeV) at the shroud inside surface is 8.17E10 n/cm2-s for Cycle 21. The azimuthal flux profile for the first quadrant of the shroud is illustrated in Figure 5-3. Thepeak flux for the first quadrant is located at the azimuth of 830.
24
GE-NE-0000-0007-2342-R 1-NP Flux distributions for the other three quadrants are expected to be similar due to quadrant symmetry of the core design.
Axial flux variation at the shroud inside surface is shown in Figure 5-4.
The elevation of peak flux occurs at 89 inches above the BAF. The ratio of peak flux to midplane flux is 1.014.
5.4 Neutron Flux Summary A summary of fast fluxes, including the peak flux at the 1/4T and 3/4T of the RPV, is shown in Table 5-1.
Also included is a comparison with the previous results from the Battelle calculation and the averaged values of Cycles 9 and 8. As stated in Section 4.4, the l/4T and 3/4T fluxes are results from flux calculations and not derived based on Reg Guide 1.99 and are presented for comparison purpose only. The calculation uncertainty and bias of these data have not been assessed. These results show that Cycle 21 fluxes are comparable to those of the averaged values of Cycles 9 and 8, ((
)) This implies that Cycle 21 fluxes can be used to represent older cycles for the purpose of estimating the life-time neutron fluences. The results imply that the Cycle 21 peak flux is acceptable for representing older cycles.
Table 5-1 Summary of Flux.Results - Cycle 21 Battelle C8-C9 Avg.
Cycle 21 Calculation Peak RPV Flux (>I MeV)
Inside Surface 2.18E8 2.86E8 2.96E8 1/4T 1.59E8 L.98E8 2.05E8 314T 6.23E7 8.26E7 8.56E7 Capsule Fast Flux 1.80E8
((L J E J L Calculated/Measured*
((
))
((JK]
Lead Factor 0.83
[
jj 1((
J 11 Peak Shroud Flux 8.IIE+1 0 8.17E+10
- Measured flux is 1.80E8 25
GE-NE-OOOG-0007-2342-R1-NP Figure 5-1. Azimuthal Distribution of Fast Neutron Flux at RPV Inside Surface at'Peak Elevation - Cycle 21 Azimuthal Distribution of Fast Flux (E>1 MeV) at Peak Elevation - Vermont Yankee 3.5E+08 U-Z I
0 10 20 30 40 0
6D Azimuth (degrees past Quadrant Reference) 70 80 90 27
GE-NE-000M-007-2342-RI-NP Figure 5-2. Axial Distribution of Fast Neutron Flux at RPV Inside Surface - Cycle 21 Axial Distribution of Relative Fast Flux (E>1 MeV) - Vermont Yankee 1.0 1.0 0.9 f4' 0.81I 0.7
,= 0.6\\
0.5 0.4 0.3
RPV ID, C21, PeakdMidplane=1.008
/
- - - RPV ID, 8CO-9 Avg., Peak/Mldplane=i.023 0.2
/
\\\\
0.1 0.0 0
0 175
-25 025 50 75
-100 125 150 175 Elevation Above BAP (Inches) 28
GE-NB-0000-0007-2342-R1-NP Figure 5-3. Azimuthal Distribution of Fast Neutron Flux at Shroud Inside Surface at Peak Elevation - Cycle 21 Azimuthal Distribution of Fast Flux (E>1 MeV) at Peak Elevation -Vermont Yankee X
,v Z
U.-
C 0
10 2D 30 40 50 80 Azimuth (degrees past Quadrant Reference) 70 80 90 29
(WE-NE-0000-0007-2342-R1-NP Figure 5-4. Axial Distribution of Fast Neutron Flux at Shroud Inside Surface - Cycle 21 Axial Distribution of Relative Fast Flux (E>1 MeV) - Vermont Yankee 1.1 0.9__
0.8
\\ I \\
0.7-\\
0 0.6 0.5-0.4
/-
\\
0.3
/-
Shroud ID, C21, Peak/Mldplane=1.014 0.2
- - -Shroud ID, C8-C9 Avg., Peak/MIdplane=1.038 0.11 0.0
-25 0
25 50 75 100 125 150 175 Elevation Above BAF (inches) 30
GE-NE-0000-0007-2342-R1-NP Figure 5-5. Axial Power Profiles of the Dominant Bundles Axial Power Profiles -Vermont Yankee 0.60 40 9
0 25 50 75 100 Elevation (inches above BAF) 125 150 31
GE-NE-0000-0007-23'42-R I-NP Figure 5-6. Relative Energy by Bundle at Core Midplane - Cycle 23 12 13 14 15 16 17 18 19 20 21 1.980.452810.3921 22 1
2 3
4 5
6 7
8 9
10 11
-I-I-,-
1.0690 1.0152 0.6705 0.4512 1.3543 12456 1.2567 0.7872 0.65261 0.5115 0.3367 1.0259 1.5231 1.3691 1.4171 1.1939 1.0509 0.6270 0.4038 1.5750 1.4965 1.6358 1.4476 1.4812 1.2252 1.1390 0.6374 0.3375 1.1147 1.6821 1.1773 1.6662 1.1081 1.4499 1.2208 1.0496 0.5123 1.7377 1.5666 1.7179 1.5703 1.6797 1.1050 1.4793 1.1864 0.6524 4-4-4.-I I" 4-I 1.4692 1.7118 1.1767 1.7148 1.5575 1.6604 1.4509 1.4202 0.7902 0.4535 1.6589 1.1418 1.6063 1.1275 1.6604 1.1675 1.6434 1.3800 1.2666 0.6753 0.3428 1.3284 1.5939 1.1253 1.6474 1.5077 1.6894 1.5199 1.5481 1.2611 1.0254 0.4579 1.0113 1.3177 1.6382 1.4461 1.7330 1.1772 1.6654 1.0602 1.3803 1.0845 0.5014 32
GE-NE-0000-0007-2342-RI-NP 6.0 NEUTRON FLUENCE A conservative estimation of fast neutron fluences at the end of plant life of 32 and 54 EFPY can, be obtained by multiplying the neutron fluxes with the EFPY. For Entergy Northeast Vermont Yankee, the bounding peak RPV flux is 2.96E8 n/cm2-s. The bounding peak shroud flux is 8.17E10 n/em2-s. ((
Based on these flux values, the 32-EFPY and 54-EFPY fluences are calculated, as summarized below:
Peak RPV Capsule Peak Shroud Fast Flux, n/cm -s 2.96ES 8.17E10 32-EFPY Fluence, n/cm2 2.99E17
[]
8.25E19 54-EFPY Fluence, n/cm 2 5.04E17 1.39E20 Figure 6-1 shows the axial distribution of 32-EFPY fast neutron fluence at the peak azimuth of the RPV inside surface. The results of the analysis demonstrate the fast fluence outside the active axial fuel zone at the RPV is less than 1.0E17 n/cm2. This conclusion is depicted in Figure 6-1.
33
9 GE-NE-0000-0007-2342-RI-NP Figure 6-1. Axial Distribution of 32-EPPY Fast Neutron Fluence at P.PV Inside Surface Axial Distribution of Fast Fluence (E>1 MeV) at Peak Azimuth 3.5E+17 3.0E+17 2.5E+17 2.OE+17 u.
0 1,5E+17 z
1.OE+17 RPV ID, C21, Peak=2.99E+17 5.02+16
- - - RPV ID, C8-C9 Avg., Peak=2.89E+17
_._E+00_
-25 0
25 50 75 100 125 150 175 Elevation Above BAF (Inches) 34
GE-NE-0000-0007-2342-R 1-NP
7.0 REFERENCES
- 1. NEDC-32983P-A, Rev. I, '"Licensing Topical Report, General Electric Methodology for Reactor Pressure Vessel Fast Neutron Flux Evaluations," December 2001.
- 2. Letter, S. A. Richards (USNRC) to J. F. Klapproth, "Safety Evaluation for NEDC-32983P, General Electric Methodology for Reactor Pressure Vessel Fast Neutron Flux Evaluation (TAC No. MA9891)," MFN 01-050, September 14,2001.
- 3. Regulatory Guide 1.190, "Calculational and Dosimetry Methods for Determining Pressure Vessel Neutron Fluence," U.S. NRC, March 2001.
- 4. CCC-543, "TORT-DORT Two-and Three-Dimensional Discrete Ordinates Transport Version 2.8.14," Radiation Shielding Information Center (R.SIC), January 1994.
- 5. "VY Fluence Evaluation Input Request from GE," Technical Evaluation No. TE-2002-031, Rev. 2, dated 10/2/2002.
- 6. R. J. Weader 11 to P. Perez and T. Wu, "VY Cycles 8 and 9 Fluence Calculation Data," Entergy Memo NEA-02-246, January 8, 2003.
- 7. BCL-585-84-3, "Examination, Testing and Evaluation of Irradiated Pressure Vessel Surveillance Specimens from the Vermont Yankee Nuclear Power Station," Battelle Columbus Laboratories, May 15, 1984.
8' Letter, S. A. Richards (USNRC) to G. A-Watford, "Amendment 26 to GE Licensing Topical Report NEDE-2401 1-P-A, GESTAR II - Implementing Improved GE Steady-State Methods (TAC No. MA6481)," November 10, 1999.
- 9. T Wu and H. A. Careway, "Discrete Ordinates Code Package User's Manual,"
November, 2001.
35