ML101410262
| ML101410262 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 05/12/2010 |
| From: | Hesser J Arizona Public Service Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 102-06191-JHH/RKR | |
| Download: ML101410262 (13) | |
Text
LA PS A
subsidiary of Pinnacle West Capital Corporation John H. Hesser Mail Station 7605 Palo Verde Nuclear Vice President Tel: 623-393-5553 PO Box 52034 Generating Station Nuclear Engineering Fax: 623-393-6077 Phoenix, Arizona 85072-2034 102-06191-JHH/RKR May 12, 2010 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001
Dear Sirs:
Subject:
Palo Verde Nuclear Generating Station (PVNGS)
Unit 3 Docket No. STN 50-530 Response to Request for Additional Information Regarding the Request for Temporary Exemption from the Provisions of 10 CFR 50.46 and 10 CFR 50, Appendix K for Lead Fuel Assemblies By letter no..102-06089, dated November 02, 2009, Arizona Public Service Company, (APS) submitted a request for a temporary exemption from the requirements of 10 CFR 50.46 "Acceptance criteria for emergency core cooling systems for light-water nuclear power reactors," and 10 CFR 50, Appendix K, "ECCS Evaluation Models," in order to use Lead Fuel Assemblies (LFAs) in PVNGS Unit 3, Cycles 16, 17, and 18. By e-mail dated February 24, 2010, the Nuclear Regulatory Commission (NRC) staff requested additional information to support their review of the exemption request. The request for additional information was clarified in an April 1, 2010, phone call between the APS and NRC staffs. The enclosure contains the APS response to the request for additional information.
No commitments are being made to the NRC by this letter. Should you need further information regarding this submittal, please contact Russell A. Stroud, Licensing Section Leader, at (623): 393-5111.
Sincerely, DCM/RAS/RKR/gat A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway
- Comanche Peak
- Diablo Canyon
- Palo Verde
- San Onofre
- South Texas
- Wolf Creek
ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Response to Request for Additional Information Regarding the Request for Temporary Exemption from the Provisions of 10 CFR 50.46 and 10 CFR 50, Appendix K for Lead Fuel Assemblies Page 2
Enclosure:
APS Response to NRC Request for Additional Information cc:
E. E. Collins Jr.
J. R. Hall L. K. Gibson R. I. Treadway
'NRC Region IV Regional Administrator NRC NRR Project Manager NRC NRR Project Manager NRC Senior Resident Inspector for PVNGS
ENCLOSURE APS Response to NRC Request for Additional Information
Enclosure APS Response to NRC Request Additional Information NRC Request 1 Specify clearly and explicitly the type of current (resident) fuel in PVNGS Unit 3 core.
Also specify the topical report (TR) related to this fuel. If there has been any modification of the fuel assembly from the specifications described in the TR, provide the new information.
Response
The PVNGS Unit 3 reactor incorporates a Combustion Engineering (CE) 16x16 standard (CE16STD) fuel assembly design with five guide tubes. Each guide tube displaces four fuel rod positions. Therefore, by design, a 16x1 6 fuel assembly would have 236 fuel rods per assembly that could be clad with Zircaloy or ZIRLOTM. This standard fuel assembly design is described in the PVNGS Updated Final Safety Analysis Report (UFSAR), Section 4.1. The majority of the PVNGS Unit 3 Cycle 16 resident fuel assemblies incorporate the Inconel 625 Top Grid with a few (< 10) reinserted assemblies with a Zircaloy-4 Top Grid.
There is no single topical report that provides the licensing basis for evaluating the CE 16x16 standard fuel assembly design. The standard fuel assembly licensing methodologies are described throughout the PVNGS UFSAR with the appropriate NRC approved topical reports referenced. The licensing approach used for the CE fuel design was to make evolutionary changes to the basic fuel design described (and approved) in the UFSAR. These evolutionary changes were addressed under the 10 CFR 50.59 process.
In WCAP-16500-P-A (Reference 1), the NRC reviewed and approved the CE 16X16 next generation fuel (CE16NGF) design. The work performed to develop the PVNGS Lead Fuel Assemblies (LFAs) for implementation into PVNGS Unit 3 is based on the CE16NGF fuel design contained in WCAP-16500-P-A. WCAP-16500-P-A references the standard fuel topical reports and provides the basis for the new design.
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Enclosure APS Response to NRC Request Additional Information NRC Request 2 Specify clearly and explicitly the details of the Lead Fuel Assemblies (LFAs) PVNGS has requested to be inserted in to the PVNGS Unit 3 core during the Fall 2010 refueling outage.
Response
The goals of the PVNGS LFA program are:
Improve fuel performance to eliminate crud failures and oxide spallation occurring at high duty operation.
Improve fuel reliability by increasing grid to rod fretting margin.
The design features a full complement of innovative components defined below to improve fuel reliability, fuel cycle economics, fuel duty, higher burnup capability and thermal performance for PVNGS.
" Advanced mid grids with "1" spring rod supports and side supported mixing vanes at selected elevations.
" Replace CE top Inconel grid with Westinghouse style top Inconel grid.
Use of Stress Relief Annealed (SRA) ZIRLO TM material for guide tubes and Optimized ZIRLO TM material for cladding and grid straps.
The addition of 2 Intermediate Flow Mixing (IFM) Grids.
The Westinghouse advanced 0.374" outside diameter (OD) rod.
ZrB2 integrated burnable absorber.
Anti-rotation joint between guide thimbles and the top nozzle.
Continued use of GuardianTM grid with solid lower end cap.
Thimble screw redesigned to eliminate the welding of a locking disk.
Bottom nozzle revised to add crimp pockets for receiving the thimble screw.
Adapter threaded and tack welded to the bottom nozzle to guide/restrain the center Instrument tube.
The work performed to develop the PVNGS LFAs for implementation into PVNGS Unit 3 is based extensively on the CE16NGF fuel design recently developed and operating in full batch at Waterford 3 and Arkansas Nuclear One Unit 2. The details of the PVNGS LFAs for implementation into PVNGS Unit 3 are based on the CE16NGF fuel design contained in WCAP-1 6500-P-A (Reference 1).
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Enclosure APS Response to NRC Request Additional Information NRC Request 3 Please provide details such as type of assembly (generic names), types of grids for each assembly (Top grid, mid grids (vaned or not), whether there are any IFM grids, bottom grids), material of grids, fuel rod dimensions (specifically fuel rod diameter) for both the LFAs and co-resident fuel in PVNGS Unit 3 core. A table similar to Table 2-1 of WCAP-1 6500-P-A comparing/contrasting the above details for the LFAs and the co-resident fuel would enable the staff to fully understand the make-up of the core for a complete review of the application.
Response
The work performed to develop the PVNGS LFAs for implementation into PVNGS Unit 3 is based on the CE16NGF design recently developed and operating in Waterford 3 and Arkansas One Unit 2. WCAP-1 6500-P-A (Reference 1) provides the basis for the CE16NGF design and was reviewed and approved by the NRC.
The PVNGS LFA is consistent with the Plant D design defined in Figure 1-1 of WCAP-16500-P-A (Page 8 of 95, Reference 1).
The Plant D design documented in the response to RAI No. 2 of Reference 2 is applicable to PVNGS.
The Plant D column of Table 2-1 (Page 6 of 20) in the response to RAI No. 2 of Reference 2 is applicable to PVNGS. Table 1 provides more specific details.
A dimensional and material comparison between the PVNGS standard design (PVSTD) and PVNGS LFA design (PVLFA) is shown in Table 2.
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Enclosure APS Response to NRC Request Additional Information Table I Differences for Plant B (CE16NGF* and Plant D (PVNGS LFA = PVLFA*
COMPONENT
]
PLANT B PLANT D COMMENTS
_(CE1 6NGF)
ýPVLFA)
(For PVLFA)
Fuel Rod Fuel Rod Design and Dimensional Reference Same Configuration Grids Inconel Top Grid Reference Same Mid Grids Reference Same IFM Grids Reference Same Guardian Grid Reference Same Guide Thimbles Outer Guide Thimbles Reference Same Center Instrumentation Thimble Reference Different PVNGS design Center Instrumentation Thimble: 1) is bulged to the Inconel Top Grid only; 2) is guided/restrained by an adapter at the bottom.
PVNGS In-Core Instrumentation centering dimples are retained.
Top Nozzle Outer Guide Posts Reference Similar PVNGS design Outer Guide Posts are slightly shorter and have CE16NGF threads.
Center Guide Post Reference Different PVNGS design Center Guide Post is modified to accommodate the Core Exit thermocouple.
Holddown Plate Reference Different PVNGS design Holddown Plate has slightly deeper counter-bores for the outer Holddown Springs.
Flow Plate Reference Similar CE16NGF design Flow Plate with slight modification to accommodate PVNGS design I Center Guide Post.
Holddown Springs Reference Different PVNGS design Holddown I Springs are slightly shorter.
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Enclosure APS Response to NRC Request Additional Information Table 1 (continued)
Differences for Plant B (CE16NGF) and Plant D (PVNGS LFA = PVLFA)
COMPONENT PLANT B PLANT D COMMENTS (CE16NGF)
(PVLFA) I (For PVLFA)
Bottom Nozzle Bottom Nozzle Reference Different PVNGS design Bottom Nozzle with slight modifications that include: 1) addition of raised bosses on the underside of the plate to house the CE16NGF design Thimble Screw crimp pockets; 2) a new adapter to guide/restrain the center Instrumentation Thimble that replaces the old restraint feature.
Adapter N/A New PVNGS design Adapter to guide/restrain the center Instrumentation Thimble.
Thimble Screws Reference Same Threaded Joint Connections Reference Same Skeleton - Thimble Bulge Tooling Reference Same 5
Enclosure APS Response to NRC Request Additional Information Table 2 Comparison of PVNGS LFA Design and the PVNGS Standard Design PVLFA 1
PVSTD FUEL ASSEMBLY Rod array in assembly 16x16 Same Rods per assembly 236 Same Fuel assembly pitch, inches Table 3-1 of WCAP-16500 Same Fuel rod pitch, inches 0.506 Same Overall assembly height, inches Taller by 0.143 inches Reference Design*
GUIDE THIMBLE/INSTRUMENT TUBES Number of guide thimble tubes 4
Same (GT)
GT Material ZIRLOTM Zircaloy-4 GT O.D. above dashpot, inches Table 2-1 of WCAP-16500 Same GT I.D. above dashpot, inches Table 2-1 of WCAP-16500 Same Number of instrument tubes 1
Same Instrument tube material ZIRLOTM Zircaloy-4 Instrument tube O.D., inches Table 2-1 of WCAP-16500 Same Instrument tube I.D., inches Table 2-1 of WCAP-16500 Same GRIDS Total number of grids 13 11 Number of Inconel top/bottom 2 (1 Each)
Same grids Top grid material type Inconel 718 Inconel 625 Top grid inner strap height, Taller by 0.014 inches Table 2-1 of WCAP-1 6500 inches Bottom grid material type Inconel 625 Same Bottom grid inner strap height, Table 2-1 of WCAP-16500 Same inches Number of mid grids 9 (6 vaned, 3 unvaned) 9 (unvaned)
Mid grid material type Optimized ZIRLOTM Zircaloy-4 Unvaned mid grid strap height, Table 2-1 of WCAP-1 6500 Table 2-1 of WCAP-16500 inches Vaned mid grid strap height, Table 2-1 of WCAP-16500 N/A inches I
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Enclosure APS Response to NRC Request Additional Information Table 2 (continued)
Comparison of PVNGS LFA Design and the PVNGS Standard Design PVLFA PVSTD Number of IFM grids 2
N/A IFM grid material type Optimized ZIRLOTM N/A IFM grid inner strap height, inches Table 2-1 of WCAP-16500 N/A TOP NOZZLE (TN)
Cast 304 SS &
TN material type Same 304 SS (Posts)
TN envelope (Flow Plate), inches Table 2-1 of WCAP-1 6500 Same OUTER GUIDE POST.
Guide post material type 304 SS Same Guide post O.D, inches Same Reference Design*
FUEL ASSEMBLY HOLDDOWN SPRING Material type Inconel 750 Same Free length, inches Shorter by 0.299 inches Reference Design*
Wire diameter, inches Same Reference Design*
Total number of turns Same Reference Design*
Max. solid height, inches Same Reference Design*
BOTTOM NOZZLE (BN)
Low Cobalt 304 Cast 304 BN material type SS.
SS SS BN envelope, inches Table 2-1 of WCAP-16500 Same FUEL ROD Cladding O.D., inches 0.374 0.382 Fuel rod length, inches Table 2-1 of WCAP-16500 Table 2-1 of WCAP-16500 Pellet diameter, inches 0.3225 0.3255 Active pellet stack length, inches 150.0 Same Cladding material type Optimized ZIRLOTM ZIRLOTM
- Reference Design reters to proprietary intormation tor current -'VNGS tuel cdesign 7
Enclosure APS Response to NRC Request Additional Information NRC Request 4 Specify what fraction of the total number of fuel rods of the LFAs will be clad in Optimized ZIRLO TM.
Response
The PVNGS Unit 3 Cycle 16 reactor core shall contain eight LFAs with each fuel assembly containing 100% (i.e., all 236 fuel rods per assembly) of the fuel rods clad with Optimized ZIRLO TM.
NRC Request 5 Provide the details regarding the critical heat flux (CHF) correlations recommended by the fuel vendor(s) for the LFAs and the resident fuel in PVNGS Unit 3 core for the proposed upcoming cycle.
Response
The LFAs will be introduced in PVNGS Unit 3 Cycle 16 core. PVNGS Unit 3 Cycle 16 will be a mixed core containing the current CE16STD fuel assemblies and eight LFAs.
While, the CE16STD fuel bundle design contains no mixing vane mid grids and no Intermediate Flow Mixing (IFM) grids, the PVNGS LFA bundle design includes six mixing vane mid grids with two IFMs in addition to three non-mixing vane mid grids at the lower portion of the bundle. The mixing vane grids and IFMs have been shown to improve DNBR margin due to turbulent mixing.
A mixed core Departure from Nucleate Boiling (DNB) analysis was performed to verify that the LFAs are not leading the core at the proposed locations using NRC approved WSSV-T (Reference 3) and ABB-NV (Reference 4) CHF correlations. The WSSV-T CHF correlation was applied in the mixing vane and IFM grid spans and ABB-NV CHF correlation was applied in the non-mixing vane grid spans. Calculations of heat flux for LFAs in a mixed core environment were compared to heat fluxes of a core with uniform CE16STD fuel over a wide range of operating conditions. The results of these comparisons show that the LFAs have 6% available power margin for the limiting combination of pressure, temperature, and flow conditions without taking advantage of the 5% power reduction credit available for the LFAs due to their non-limiting location in the PVNGS Unit 3 Cycle 16 core design.
Thus, since there is adequate heat flux margin available to support LFAs at the proposed locations of the core, it is conservative to treat the LFAs as CE1 6STD fuel with the CE16STD CE-1 CHF correlation (References 5 and 6). The use of the CE-1 CHF correlation with our current CE16STD fuel is consistent with the PVNGS Reload Methodology.
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Enclosure APS Response to NRC Request Additional Information NRC Request from February 24, 2010 E-Mail:
Separate from the attached RAIs, the staff noted that TS 4.2.1, "Fuel Assemblies," does not contain an explicit provision to allow the use of advanced zirconium alloy in assembly structural materials other than cladding, such as spacer grids. Thus, if Optimized ZIRLO TM is used in non-cladding components of the LFAs, a license amendment to revise TS 4.2.1 may also be needed.
Response
The intention of technical specification (TS) 4.2.1 is to allow the placement of a limited number of LFAs that have not completed representative testing into the PVNGS Cores in non-limiting core regions. The TS authorizes the use of cladding material other than Zircaloy or ZIRLO with an approved exemption.
Optimized ZIRLO TM material will be used for the fuel rod cladding. Optimized ZIRLO TM will also be used for mid grids, IFM grids, and grid straps. The use of Optimized ZIRLO TM material for structural materials other than cladding is consistent with the current CE16NGF Waterford and Arkansas fuel batches.
The PVNGS request for a Temporary Exemption from the provisions of 10CFR 50.46 and 10CFR 50 Appendix K is specifically to allow the use of Optimized ZIRLO TM alloy as the fuel rod cladding material at PVNGS. PVNGS will evaluate all other differences (physics, thermal hydraulics, mechanical design, and safety analysis) associated with the LFAs as a change to the Plant in accordance with 10 CFR 50.59. The 10 CFR 50.59 review is expected to conclude that a license amendment request is not required.
References:
Reference 1: WCAP-16500-P-A, "CE 16x16 Next Generation Fuel Core Reference Report," August 2007.
Reference 2: Westinghouse Letter to the NRC, "Response to NRC's Request for Additional Information By the Office Nuclear Reactor Regulation Topical Report WCAP-1 6500-P, CE 16x16 Next Generation Fuel Core Reference Report (TAC No.
MD0560, Proprietary/Nonproprietary),"LTR-NRC-06-66, November 29, 2006.
Reference 3: WCAP-16523-P-A, "Westinghouse Correlations WSSV and WSSV-T for Predicting Critical Heat Flux in Rod Bundles with Side-Supported Mixing Vanes,"
August 2007.
Reference 4: CEN-387-P-A, "ABB Critical Heat Flux Correlations for PWR Fuel,"
May 2000.
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Enclosure APS Response to NRC Request Additional Information Reference 5: CENPD-1 62-P-A, "Critical Heat Flux Correlation for C-E Fuel Assemblies with Standard Spacer Grids, Part 1, Uniform Axial Power Distribution,"
September 1976.
Reference 6: CENPD-207-P-A, "Critical Heat Flux Correlation for C-E Fuel Assemblies with Standard Spacer Grids, Part 2, Non-Uniform Axial Power Distribution," December 1984.
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