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This engineering status report outlines the accomplishments, challenges, and milestones of the National FIRE Design Team's efforts in developing the fusion reactor design. Key topics include TF coils, solenoid structure, field coils, plasma components, safety considerations, and more.
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Engineering Status Richard J. Thome for the National FIRE Design Team NSO PAC3 Meeting U. Of Wisconsin, Madison July 10-11, 2001
TF Coils & Global Structure Central Solenoid & Poloidal Field Coils Vacuum Vessel Plasma Facing Components Thermal Shield Ion Cyclotron Heating Fueling & Pumping Tritium Systems Neutronics & Shielding Activation, Decay Heat & Radiation Exposure Remote Maintenance Magnet Power Systems Cryoplant Facilities & Siting Safety The FIREDesign effort has addressed all major subsystems & issues: -Design goals have been met or exceeded for the baseline. -Several options & issues have been identified. -Initial cost estimates have been prepared. -Peer reviews have been done on some major systems.
June 5-7, 01 Review Committee Membership Note: Committee review report to C. Baker is on web.
FIREWedged Baseline Operation Summaryc-June 5-7, 01 Note: a) BeCu for TF coil inner leg; OFHC for balance of TF coils, CS and PF coils b) AT mode pulse length with DT may be limited by VV or PFC thermal limits c) meets or exceeds engineering requirements
Bucked and Wedged TF Coil Study • An all OFHC, Bucked and Wedged, TF configuration is an option • Max Field is <12T to remain within the OFHC copper allowable stress limit • Longer pulses are possible at a given field level • Lower power requirements may increase number of possible sites • TF material & processing costs will be reduced • R&D for a BeCu to OFHC joint in TF plates will not be required • TF fabrication & assembly will be more complex to assure proper bucking & wedging
POWER REQUIREMENTS FOR FIRE, June 5-7, 01 BeCu TF Inner Legs All Cu TF Coils Significantly lower power for all Cu TF coils reduces capital & operating costs and expands the list of candidate sites.
FIREDesign Review Variations-June 5-7, 01 Questions: • What is a suitable margin for Pre-conceptual design? • What can the machines do at comparable stress margins?
External Review of FIRE Design Point-- Conclusion Summary for Magnet Systems • Critical Design Issues • Focus on 2 designs near Q=10 that have, at the Pre-conceptual Design level, an Engineering Margin of 1.2-1.3 • Then focus on 1 device, either wedged or bucked and wedged (to be selected by the design team) • Incorporate design attention to the details of leads, both TF and CS, associated cooling systems & design of all other critical systems that are lacking detail at the Pre-conceptual level • Critical R&D Issues • Qualification of the properties of BeCu for the wedged design and OFHC copper for the bucked and wedged design in sizes and thicknesses needed for fabrication • Qualification of materials for the insulation systems
Estimated Machine Variations at Margins of 1.0-1.3 Question: What is an appropriate margin at this stage? June Review recommends: 1.2 to 1.3
Preliminary B & W Risk Assessment • Can a B&W machine be assembled?…..yes • Is it robust wrt assembly tolerances?……yes • Issues to be resolved: • Need for a bucking cylinder • Cooling of the Central Solenoid • Material properties for TF conductor
Two B & W Assembly Options That Work • High Tolerance Machining • Machine wedge faces and nose of TF coils • Machine the CS to a known OD • Assemble TF array; apply ring preload • Machine TF bore • Back-off TF coils; insert CS; reset TF coils • Epoxy filled bladders and shims • Assemble TF coils and CS with radial gap • Use machined wedge faces or epoxy filled bladders at TF wedge faces • Use epoxy filled bladders in radial gap • (as in ITER CS Model Coil) • Remove a shim if a gap is desired
B&W Assembly is Robust wrt Tolerances • Elastic/Plastic Analysis Summary for 11.5 T: • Fractional mm fit-up tolerances are OK • Off-normal fit, up to ~2.5 mm, produces small plastic strains within the capacity of the conductor and insulation materials
External Review of FIRE Design Point-- Conclusion Summary for VV, PFC’s, Fueling & Pumping • Critical Design Issues • The design divertor heat load of 25 MW/m2 for the outer divertor is at the limit of engineering feasibility • Develop a complete description of disruption/loads/stresses • Consider active cooling for the inner divertor • Determine diagnostic design & R&D required • Critical R&D Issues • Determine behavior of W rods in divertor plates under disruption conditions (loss of melt layer, effects on neighboring rods, etc.) • Optimization Issues • Adopt the ITER Design Criteria & expand as needed • Require 104 l/s pumping speed • Determine Cu-ss bonding method for in vessel use
FIRE Engineering R&D • State-of-the-art materials and manufacturing processes will allow the highest performance to be achieved cost effectively. • Several R&D areas have been identified to: -complete the material property data base to assure consistency with design criteria for materials procured in the size required for the device, -test design concepts for component manufacture or assembly to assure processes are sufficiently developed and specified, or -validate the design of prototype components through fabrication and test to assure that performance, cost or remote handling features have been adequately considered.
Engineering R&D Lists & Initial Cost Estimates • TF Conductor and Design Criteria • TF Conductor Joints • Radiation Resistant Electrical Insulation • High and Low Friction Materials • High Force, High Reliability Jacking System for TF coils • First Wall and Divertor Components • Vacuum Vessel • Remote Handling • Fueling and Pumping • ICRH Antenna • Power Supply System-tbd Note: red specifically mentioned in June reviewers report
1.Copper Conductor and Design Criteria Background: • The data base requires assessment and extension for plates of the size to be procured for the full scale TF and CS conductor. The properties assumed require validation for both designs. Inner Leg of the Wedged TF baseline design- • C17510 BeCu (68% IACS) in thick plate (36mm) form is used in the inner leg. The principal stresses are primarily axial tension and azimuthal compression. Required: UTS 800 MPa; min. yield: 724 MPa. Bucked and Wedged TF alternate design- • Design uses OFHC copper in thick plate form. Required: ~60% cold work for ~300 MPa Central Solenoid Coil: Both Wedged and Bucked and Wedged Alternate Design • Both concepts use C10200 copper in thick plate (38mm) form. Rolled or forged copper discs are required to meet strength requirements. (350 MPa UTS; 300 MPa min. yield) R&D Task: • Obtain samples from full size plate stock and carry out a mechanical testing program to assure that static and crack growth properties at room and LN2 temperatures are adequate.
2. Conductor Joint Development Background:Both the baseline and alternate TF coil designs require a high strength joining process which does not result in an annealed zone. Baseline wedged design: • The baseline design uses C17510 BeCu for the inboard leg of the TF coils and C10200 copper for the balance of the coils. A cost effective, reliable high strength joining method for the material transition is essential. Bucked and wedged alternate design: • The bucked and wedged alternate TF design uses OFHC copper throughout the TF coil. In principal the turns for the latter could be cut from large thick plates, from which, the centers would be scrap. A cost effective joining method for joining plate segments would allow the TF legs to be fabricated from readily available plate sizes and eliminate the need to procure specially sized plates. R&D Task: • Develop manufacturing processes and carry out a mechanical testing program to assure adequate mechanical properties and to validate design criteria for the joints. Potential candidate processes include friction stir welding and e-beam welding.
3. Radiation Resistant Insulating Materials Background: • Data from the BPX insulation test program indicates that there are several glass/epoxy formulations (CTD-101; Shikazima) which can meet FIRE’s requirement for radiation exposure capability of 1.5 x 1010 rads. • This is a high leverage R&D item, since it has the potential to permit more full power D-T shots and may permit the experimental program to be expanded with possibly only a minor impact on costs. R&D Task: • Develop high radiation resistant insulating materials with good processing characteristics for coil fabrication. (note: several SBIRs are underway in this area)
Conclusions • A FIRE Wedged baseline is a reasonable choice • A FIRE Bucked &Wedged machine is a suitable back-up: • It can be assembled with adequate tolerances • It is robust wrt assembly tolerances • B&W Design Issues to be resolved: • Need for a bucking cylinder • Cooling for the CS • R&D items have been identified • Critical Items as per review: • Material properties for conductor and insulation • Behavior of W rods in divertor • R&D tasks require a budget and time frame!
4a. Low Friction Insulation Characterization Background: The design of the TF and CS coil systems require that selected interface areas retain a desired level of either low or high friction during operation. Segmented Central Solenoid in both Wedged and Bucked & Wedged Designs- • FIRE employs a segmented CS with a variation of currents among the 5 coils in the stack during a pulse. • Adjacent coils in the CS operate with different temperature and electromagnetic load profiles during a pulse. • Adjacent coils will strain differently and relative radial motion between coils in the CS will occur. • Interface must lock the coils azimuthally, maintain the coils co-axial, and allow relative radial motion with low friction. R&D Tasks: • Prototypes of the interface areas will be fabricated and tested under simulated operating conditions to verify operation and adequate life. .
4b. Low Friction Insulating Material for the TF/CS Interface in Bucked Designs • Background: The CS tends to expand radially and compress axially during operation. The inboard legs of the TF coils tend to stretch vertically due to their in-plane loads and shift azimuthally due to their out-of-plane loads. In a bucked design a low friction interface between the TF and CS is desirable to limit: • the CS vertical tension imposed by the TF, • transmission of torsional shear into the CS, and • radial-vertical traction shear imposed on the CS by the TF. R&D Task: • Select candidate materials and processes for application to the identified interfaces in the FIRE design. • Apply low friction materials to substrates on a scale consistent with fabrication methods for FIRE. • Perform mechanical tests to assure that expected surface friction performance is consistent with design criteria and reliable for the lifetime of the machine.
4c. High Friction Insulation Characterization Background: TF Coils in both Wedged and Bucked & Wedged Designs- • Overturning moments on the TF coils are reacted by wedging action at the inboard legs and by shear between interfaces of the outer intercoil structures on the TF cases. • A friction coefficient of ~0.3 is needed between TF inboard legs to limit torsional motions and between cases on the outboard side to reduce shear pin and bolting requirements R&D Task: • Testing is required to verify friction coefficients and adequate life.
5. Ring Preload Jacking System Background:Both the Wedged and the Bucked and Wedged TF coil designs use large steel rings outboard of the TF coils. The rings are pre-loaded at assembly using radial jacks to augment the wedge compression at the inboard faces of the TF coils and provide compression between the faces of the outboard intercoil structures during operation. The space available is very limited. Three jack concepts have been identified: • A mechanical system (proposed for IGNITOR) consisting of opposing wedges • Stainless steel bladders with hydraulic fluid • Commercial “Enerpac” jacks R&D Task:Select one primary concept plus one back-up. Mock-up and test under expected operating conditions simulating assembly, cooldown, operational pressures, and temperatures.
9.Remote Handling R&D Background: Remote handling of components is a key issue because of activation. Verification of designs and component maintenance tasks should be completed prior to final design completion, or at least prior to fabrication of components. The goal is to reduce cost and times for replacement, repair and maintenance tasks. R&D tasks: 1. In-vessel transporter (articulated boom) & component handling end effectors 2. In-vessel inspection systems (laser metrology and video systems and deployment mechanisms) 3. Midplane and auxiliary port handling vehicles and dexterous manipulator 4. YAG laser based divertor pipe & port lip seal cutting, welding, and inspection tools, and power fastener wrench 5. Midplane port cask and air cushion transport vehicle 6. Hot cell remote repair stations & fixtures for midplane port assembly, divertor modules, and cryopump
9.Fueling and Pumping Background: A new, twin screw, extruder concept has the potential to run steady state with reduced hydrogen ice inventories compared to existing linear piston extruders. In parallel, a cooling concept based on a Gifford-McMahon cryocooler could be developed to simplify operation of the pellet injector by removing the need for liquid helium. The design of cryopumps for the divertor relies on helium compression in the pump entrance region to allow a compact, in-vessel system. R&D Tasks: Design, build and test a prototype twin screw extruder with the goal of minimizing tritium inventory for safety and siting flexibility. Demonstrate extruder cooling without LHe by using a G-M cryocooler. Design, build and test a single cryopump module to validate the expected inlet He compression which permits a compact in-vessel pumping system.
ICRH Antenna Mockup R&DBackground: Calculations for the two current strap antenna show good performance, but the model requires validation with an electrical mock-up of the antenna.R&D Task: Build and test a mock-up that uses a sheet metal antenna cavity & current straps, an uncooled Faraday shield, and is not vacuum compatible. Measure electrical characteristics at operating frequencies, refine electrical models, and modify the design as results indicate to improve performance.
