NSTX Supported by Design and Requalification Efforts to
NSTX Supported by Design and Requalification Efforts to Support the Upgrade of the NSTX College W&M Colorado Sch Mines Columbia U Comp. X General Atomics INEL Johns Hopkins U LANL LLNL Lodestar MIT Nova Photonics New York U Old Dominion U ORNL PPPL PSI Princeton U Purdue U SNL Think Tank, Inc. UC Davis UC Irvine UCLA UCSD U Colorado U Illinois U Maryland U Rochester U Washington U Wisconsin NSTX L. Dudek and NSTX CSU Team Presented at 26 th SOFT September 27 - October 1, 2010 26 th SOFT, September 27 - October 1, 2010 Culham Sci Ctr U St. Andrews York U Chubu U Fukui U Hiroshima U Hyogo U Kyoto U Kyushu Tokai U NIFS Niigata U U Tokyo JAEA Hebrew U Ioffe Inst RRC Kurchatov Inst TRINITI KBSI KAIST POSTECH ASIPP ENEA, Fracati CEA, Cadarache IPP, Jülich IPP, Garching ASCR, Czech Rep U Quebec 1
Outline • • Introduction Requirements Scope Component Designs – TF Bundle – OH Coil – Flex Joint – Coil Support Structure • R&D • Schedule Timeline • Conclusion NSTX 26 th SOFT, September 27 - October 1, 2010 2
Introduction • The National Spherical Torus e. Xperiment (NSTX) is a high performance ST research facility • Since starting operation in 1999, NSTX has established the attractiveness of the low-aspect-ratio tokamak ST concept characterized by strong intrinsic plasma shaping and enhanced stabilizing magnetic field line curvature • In early 2009 the US Department of Energy approved the initiation of a project to upgrade the NSTX for improved performance NSTX 26 th SOFT, September 27 - October 1, 2010 3
Introduction • Purpose – To expand the NSTX operational space and thereby the physics basis for the next-step ST facilities – To achieve higher levels of performance and pulse duration • Requirements Summary Plasma Major Radius [m] Aspect Ratio Plasma Current, IP [MA] Toroidal Field Bt [T] Pulse Length, Tpulse [s] Rep Rate Trepetition [s] Center Stack Radius Rcenterstack [m] Antenna Rad, Rantenna [m] NSTX 0. 8540 1. 266 1. 0 0. 55 1. 0 600 0. 1849 1. 5740 26 th SOFT, September 27 - October 1, 2010 NSTX-CSU 0. 9344 1. 500 2. 0 1. 0 5. 0 2400 0. 3148 1. 5740 4
Modifications Required to the NSTX device • Completely replace center stack – New TF inner leg assembly, same height and number of turns as existing – New TF joints and radial extensions – New OH solenoid, same height as original – New inner PF coils PF 1 a, 1 b, 1 c – New center stack diagnostics (including Ip Rogowski) – New center stack casing and PFC tiles • Retain existing outer PF coils but with enhanced supports • Retain existing TF outer legs but with enhanced supports • Structural upgrades to vacuum vessel, umbrella, legs, and center stack support pedestal NSTX 26 th SOFT, September 27 - October 1, 2010 5
Modifications Required to the NSTX device • Upgraded TF power supply rated for 1 k. V/130 k. A • In a parallel effort, a second neutral beam will be added by relocating an existing mothballed TFTR Neutral Beam (NB) from the adjacent room • Whether or not additional items such as internal hardware will require modification due to higher Ip and disruption forces is still under assessment – P 4 -135 “NSTX Disruption Simulations of Detailed Divertor and Passive Plate Models by Vector Potential Transfer from Opera Global Model Results” Peter Titus NSTX 26 th SOFT, September 27 - October 1, 2010 6
The Existing Test Cell 2 nd NBI to be located here (5 MW @ 5 sec) Removals and re-installations required NSTX 26 th SOFT, September 27 - October 1, 2010 7
Center Stack Upgrade - Scope NSTX 26 th SOFT, September 27 - October 1, 2010 8
TF Bundle to Outer TF Connections • Early in the upgrade design a decision was made to locate the joint further outboard to reduce the EM loads (and trapping the OH solenoid) • A Friction Stir Welding (FSW) extension allows the joint to be located several inches outward in a lower EM field region • The new electrical joint has approximately 5 times the liftoff margin of the existing design at 2 times the field NSTX 26 th SOFT, September 27 - October 1, 2010 9 9
ANSYS Static Structural Results: TF Joint Tresca Stress Current Scenario #82, 31 Laminations/ Strap • Flat Top Current: 129. 8 k. A • Max Stress (lamination): 130 MPa • Copper threads stress: 240 MPa • Joint contact pressure of 18 MPa maintained under loads • Meets NSTX 60, 000 cycle design criteria for fatigue • Safety factor of 5 in buckling NSTX 26 th SOFT, September 27 - October 1, 2010 10
Inner TF Conductor Design / Fabrication • The FSW lead extensions are provided with 5/8” threaded inserts for studs and Torque Nuts for attachment to the flex connector • The upper coil extension is shorter in height than the lower to allow for installation of the PF 1 A coils and center stack casing • Lead extensions will be fabricated using high strength copper [Cu-Cr-Zr] • Lower Lead • Upper Lead NSTX 26 th SOFT, September 27 - October 1, 2010 6 11
Ohmic Heating Solenoid- Design parameters Upgrade Design Operating Voltage 6077 volts Number of turns 884 Number of layers 4 Cooling hole diameter Operating current 5. 7 mm 24, 000 amps Groundwall insulation 2. 74 mm Turn insulation 1. 21 mm Turn-Turn Voltage Stress 57 Volt/mil Outside diameter 561. 3 mm Copper mass 2805 kg Cooling paths 8 NSTX 26 th SOFT, September 27 - October 1, 2010 Fro nt V iew 1212
OH Manufacturing Plan • Manufacturing Steps: – The TF bundle will have 2. 5 mm “Aquapour” layer molded onto the outer surface to create the temporary winding surface. – The TF bundle mandrel will be mounted into a turning fixture – The OH conductor will be wound under tension – Install mold around coil assembly – VPI OH coil- full cure cycle both coils Mid Supports • Discussions with Composite Technical Development has verified that this process [double epoxy full cure- TF and OH] would work. – The “Aquapour” will be washed out with water – Perform final electrical and pressure tests on both OH and TF bundles – Apply outer ground plane – Mount surface diagnostics – Install “Micro-Therm” insulation NSTX 26 th SOFT, September 27 - October 1, 2010 13 13
Tile Material: Carbon Fiber Composite • Two zones to cover: – Vertical CS • Use low-k CFC (2 D) – Limit heat load to CS casing – Tiles 19 mm thick – Diagnostic Tiles – Inboard Diverter • • • Use high-k CFC (3 D) – Conduct heat to active cooling system – Tiles 25 mm, 50 mm thick – 3 D conduction relieves thermal stresses and allows active cooling NSTX 26 th SOFT, September 27 - October 1, 2010 Rogowski Langmuir Thermocouple Mirnov 14
Coil Support Design • The conservative initial analysis of the existing machine attempted to qualify the existing vacuum vessel, TF and PF coil support structure to the full power supply limits (worst case combinations) • The resulting structure design concepts were large and expensive and required significant field modifications to the existing vacuum vessel, structural mounting points and existing PF coil support ribs. • The modifications were judged to be costly, risky and difficult to implement on an operating experiment which was cluttered with external diagnostics and auxiliary equipment. • To prevent mis-operations where the power supplies deliver current combinations and consequential forces/stresses beyond the design-basis envelope a Digital Coil Protection System (DCPS) is being implemented to constrain the operating envelope. • The design described is based on analysis using the operating conditions described earlier, and qualified for 96 coil current scenarios, or roughly a factor of four. NSTX 26 th SOFT, September 27 - October 1, 2010 15
PF 2 & PF 3 Supports Require Minimal Change • The existing rib to VV welds were qualified by analysis using the asbuilt condition with gaps and splice plates • All PF 2 and PF 3 hardware to be replaced with Inconel 718 • PF 3 welds size will increase from 1/8 to 5/16” Additional (new) PF 2 Coil: Support & Clamp PF 2 Coil PF 3 Coil: Support Clamp PF 3 Coil: Support Mount NSTX PF 3 Support PF 2 Coil: Support Clamp PF 2 Coil: Support Mount VV Chamber: Dome 26 th SOFT, September 27 - October 1, 2010 NEW WELDMENT Size increase from 1/8 to 5/16 16 16
PF 4 & 5 Supports • For the PF 4 and PF 5 support upgrade, six new supports will be added while utilizing the six existing supports • The new supports are positioned in the shadow of the TF outer legs to avoid interferences with existing equipment • To accommodate thermal growth only two clamps 180º apart (one being nearest the electrical leads) provide radial restraint • The maximum allowable slip due to thermal growth for both coils is 3 mm PF 4 Upper Coil PF 5 Lower Coil PF 4 Coil: Support Clamp New PF 4/5 Support PF 4 Lower Coil Existing PF 4/5 Support NSTX PF 5 Coil: Support Clamp PF 4/5 Support Column 26 th SOFT, September 27 - October 1, 2010 17
TF Outer Leg Support Structure • The support structure must minimize the stress within the TF outer legs, specifically the epoxy, and copper-epoxy interface • The support must constrain the TF outer legs to a maximum deflection, 19 mm, between the top and bottom of the existing TF outer leg clamps • A finite portion of load is coupled to the VV via a compliant member (i. e. a spring) and through an existing clevis – Maximum load at the clevis 22. 2 k. N – Spring rate: 17. 5 k. N/cm • Additional constraint: – No direct modifications to the existing TF outer leg clamps NSTX 26 th SOFT, September 27 - October 1, 2010 18 18 14
TF Outer Leg Support Detail TF Coil Outer Legs Spring Link Existing Clevis Dielectric Breaks New Support Structure • Designed to be bolted in place using the existing space of the outer TF supports to minimize interferences • Utilizes the existing clevis without field welding or cutting • Provision included for adjustments at time of installation (match drilling) NSTX 26 th SOFT, September 27 - October 1, 2010 Encapsulates Clamp Main Weldment 1919 15
R & D Activities in Support of the Design TF Flex strap assembly Full size mock up of the umbrella TF and flexes Friction Stir Welding In-line braze joint tests [OH] NSTX C 107 – C 185 (Cu-Cr-Zr) (Edison Welding Inst. ) 26 th SOFT, September 27 - October 1, 2010 OH Layer to layer TIGBraze joint 20
Schedule Timeline • Preliminary Design Review: April 2010 • Early Procurements: Fall 2010 – Tiles and Conductors Early Procurement to ensure deliver without impact to critical path NSTX • Final Design Review: April 2011 • Coil Fabrication: May 2011 - Mar 2013 • Installation: April 2012 thru July 2014 26 th SOFT, September 27 - October 1, 2010 21
Conclusion • The upgrade requirements are challenging but a conservative preliminary design has been generated • The upgraded TF joint, which was problematic with the original design, has evolved into a robust design with major improvement in margin • With careful attention to design details the upgrade can be installed on an operating experiment with minimum impact to the auxiliary equipment NSTX 26 th SOFT, September 27 - October 1, 2010 22
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