A central feature of an Inertial Fusion Energy (IFE) power plant is a target that has been compressed and heated to fusion conditions by the energy input of the driver. The IFE target fabrication programs are focusing on methods that will scale to mass production, and working closely with target designers to make material selections that will satisfy a wide range of required and desirable characteristics. Targets produced for current inertial confinement fusion experiments are estimated to cost about $2500 each. Design studies of cost-effective power production from laser and heavy-ion driven IFE have found a cost requirement of about $0.25-0.30 each. While four orders of magnitude cost reduction may seem at first to be nearly impossible, there are many factors that suggest this is achievable. This paper summarizes the paradigm shifts in target fabrication methodologies that will be needed to economically supply targets and presents the results of ''nth-of-a-kind'' plant layouts and concepts for IFE power plant fueling. Our engineering studies estimate the cost of the target supply in a fusion economy, and show that costs are within the range of commercial feasibility for laser-driven and for heavy ion driven IFE

Goodin, D. T.

Maxwell, J. L.

Nobile, A.

Rickman, W. S.

Schroen, D. G.

UNT Digital Library

G A-A24429 COST-EFFECTIVE TARGET FABRICATION FOR INERTIAL FUSION ENERGY by D.T. GOODIN, A. NOBILE, D.G. SCHROEN, J.L. MAXWELL, and W.S. RICKMAN MARCH 2004 4 DISCLAIMER It This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. 11 GA-A24429 COST-EFFECTIVE TARGET FABRICATION FOR INERTIAL FUSION ENERGY by D.T. GOODIN, A. NOBILE,* D.G. SCHROEN,? J.L. MAXWELL,* and W.S. RICKMAN* *Los Alamos National Laboratory tSchafer Corporation STSD Management Associates This is a preprint of a paper presented at the 3rd International Conference on Inertial Fusion Sciences and Applications, Monterey, California, September 7-1 2, 2003 and to be published in Fusion Science and Technology. Work supported by the US. Department of Energy under Contract No. DE-AC03-98ER54411 , and Subcontract NO01 73-02-C-6007 GENERAL ATOMICS PROJECT 39083 MARCH 2004 W021.4 COST-EFFECTIVE TARGET FABRICATION FOR INERTIAL FUSION ENERGY D.T. Goodin,l A. Nobile,2 D.G. S ~ h r o e n , ~  J.L. MaxwelL2 and W.S. Rickman4 lGeneral Atomics, P.O. Box 8.5608, San Diego, California 92186-5608 USA email: dan.goodin@gat.com *Los Alamos National Laboratory, Los Alamos, New Mexico 87545 USA Schafer Corporation, Livermore, California USA 4TSD Management Associates, P.O. Box 23 1366, Encinitas, California 92023 USA A central feature of an Inertial Fusion Energy (IFE) power plant is a target that has been compressed and heated to ,fusion conditions by the energy input of the driver. The IFE target ,fabrication programs are ,focusing on methods that will scale to mass production, and working closely with target designers to make material selections that will satis& a wide range of required and desirable characteristics. Targets produced for  current inertial confinement fusion experiments are estimated to cost about $2500 each. Design studies of cost-effective power production from laser and heavy-ion driven IFE have found a cost requirement of about $0.25-0.30 each. While four orders of magnitude cost reduction may seem at first to he nearly impossible, there are many,factors that suggest this is achievable. This paper summarizes the parudigni shifts in target ,fabrication methodologies that will be needed to economically supply targets and presents the results of “nth-of-a-kind” plant layouts and concepts ,for IFE power plant ,fueling. Our engineering studies estimate the cost of the target supply in a,fusion economy, and show that costs are within the range of commercial feasibility for laser-driven and,for heavy ion driven IFE. I. INTRODUCTION AND REQUIREMENTS A central feature of an Inertial Fusion Energy (IFE) power plant is a target (Fig. 1) that has been compressed and heated to fusion conditions by the energy input of the driver beams. A target development program is underway to demonstrate successful target technologies for IFE app1ications.l For direct drive IFE, energy is applied directly to the surface of a spherical capsule2 containing the deuterium-tritium (DT) fusion fuel at approximately 18 K. For indirect drive,3 the target consists of a similar fuel capsule within a cylindrical metal container or “hohlraum” which converts the incident driver energy into x-rays to implode the capsule. The target must be accurately delivered to the target chamber center at a rate of about 5-10 Hz, with a precisely predicted target l ~ c a t i o n . ~  The relatively fragile cryogenic targets must survive injection into the target chamber without damage. The Target Fabrication Facility (TFF) of an IFE power plant must supply about 500,000 targets per day. The feasibility of developing successful fabrication and injection methodologies at the low cost required for energy production (about $0.25/target, about lo4 less than current costs) is a critical issue for inertial fusion. The top-level requirement is the ability to provide targets filled with DT ice at -18.5 K, and meeting the geometric requirements, and deliver them accurately and repeatedly to the center of a high-temperature target chamber at a high rate. 11. MANUFACTURING APPROACHES There are tremendous differences in the criteria and requirements for current-day experimental targets and those anticipated for high-volume manufacturing of IFE targets. Consequently, major new “paradigms” must be incorpo- rated into the manufacturing approaches for Inertial Fusion Energy. The first major step is to think i n  terms of continuing process improvement, but with a constant product line. This eliminates the highly significant development (first-of-a-kind) costs for experimental targets. Secondly, statistical process control will be employed along with rapid “quick-check” methods to ensure the validity of each target prior to injection. This eliminates the major costs due to individual characterization of current day targets. Thirdly, ongoing target technology development programs will result in GENERAL ATOMICS REPORT GA-A24429 1 COST-EFFECTIVE TARGRT FABRICATION FOR INERTIAL FUSION ENERGY D.T. GOODIN. et ul. 1 pm of CH t 0.03 pm Gold, Some Expected Direct Drive Specifications Capsule Material CH (DVB) foam Capsule Diameter -4 mm Capsule WallThickness 290 pm Foam shell density 20-120 mgkc Out of Round 4 %  of radius Non-Concentricity 4 %  of wall thichness Shell Surface Finish -20 nm RMS Ice Surface Finish < I  pm RMS Temperature at shot -16 - 18.5K Positioning in chamber k 5 mm Alignment with beams <20 pm Some Possible Indirect Drive Specifications Capsule Material CH Capsule Diameter -4.6 mm Capsule WallThickness 250 pm Out of Round Non-Concentricity 4% of wall thickness Shell Surface Finish Ice Surface Finish Temperature at shot Positioning in chamber Alignment with beams t200 pin 4% of radius 20-200 nm RMS 1-10 pm RMS -16 - 18.5K less than f 1-5 mm Fig. 1. Reference target designs have been identified. increased product yields and, finally, nth-of-a-kind plants will naturally operate with larger batch sizes. These factors will all contribute to major cost reductions for mass- production of targets. III. PROCESS DESCRIPTION There are many steps leading to a filled, layered target ready for injection. First, the highly spherical and concentric capsule must be manufactured. The direct drive target (foam capsule) is based on a divinyl benzene f 0 a m ~ 3 ~  with a density of about 100 mg/cc. These foam capsules are made with a dibutyl phthalate foam solvent and a 2,2’ azo- bis-iso-butyronitrile initiator for subsequent DVB cross- linking. Water is inside the foam capsules during a “microencapsulation” process utilizing a droplet generator, and water/polyvinyl alcohol is on the outside. The partially cross-linked capsules are heated for full polymerization, then isopropanol is transferred into the inner part (the alcohol is sufficiently miscible in both water and oil to facilitate a transtion from inner water to inner oil (parachlorotoluene). The inner oil provides a medium for dissolution of Monomer A (isophthaloyl dichloride); then watedsurfactant replaces the oil outside the targets to prevent sticking and provide an aqueous medium for Monomer B (poly 4-vinyl phenol). These two monomers form a thin (1-5 pm) “seal coat” at the oiVwater interface on the target surface. Isopropanol is sufficiently miscible in both oil (parachlorotoluene) and CO2 to facilitate the transition from inner oil/outer water to C02 both inside and outside the capsule. Liquid subcritical C 0 2  ( 10°C, 800 psig) replaces the inner isopropanol by countercurrent stagewise dilution contacting. The resulting liquid C02 filled capsules are heated beyond the C02 critical point (31”C, 1070psig) to reduce surface tension to zero and prevent fracturing during the final “drying” process. For direct drive targets, a thin gold and palladium coat is added to the capsule outer surface by a physical vapor deposition process. This Ag/Pd coating is about 30 to 100 nm thick; the addition of Pd to the coating has been shown to greatly increase its permeability (thus allowing rapid filling with DT). In addition, an outer “insulating” foam layer may be added to provide increased thermal robustness during the (later) injection into a target chamber. The capsule must be filled with a mixture of deuterium and tritium as the fusion fuel. The filling is done by permeating the DT through the capsule wall in a controlled manner (to prevent buckling) in a high pressure cell. Once the capsule internal density reaches the required value, the cell is cooled down to approximately 20 K to condense the fuel and reduce the internal pressure sufficient to allow removal of the excess DT outside the capsule. The filled capsules, which now must be handled cryogenically, are then placed in an extremely isothermal temperature environment to redistribute the DT into a highly uniform layer on the inner surface of the capsule (a process called “layering”). One method to achieve the required isothermal environment is a cryogenic fluidized bed? which provides a highly uniform time-averaged surface temperature for the capsule. Once layered, in the case of direct drive, the capsule is removed from the fluidized bed and quickly placed into a sabot to protect it during acceleration for injection into the target chamber. An electromagnetic accelerator or light gas gun is then used to bring the target up to injection velocity. The sabot is removed prior to entering the high temperature chamber. 2 GENERAL ATOMICS REPORT GA-A24429 D.T. GOODIN, et al. COST-EFFECTIVE TARGRT FABR~CATION FOR INERTIAL FUSION ENERGY In the case of indirect drive targets, the hohlraum components must also be provided and assembled.* After manufacture, the target is injected into the target chamber. The DT layer must survive the exposure to the rapidly increasing heat flux, remain highly symmetric, and have a smooth inner ice surface finish. The final target design (e.g., the surface reflectivity, the heat capacity, amount of insulation, etc.) and injection conditions (e.g., velocity, initial temperature, chamber environment) must facilitate target survival. Target placement must be within a specified “box” at the chamber center (i.e., within the reach of beam steering). In addition to the placement, target tracking must be accurate enough to enable precise alignment of the driver beams with the actual target position. The accuracy requirement for indirect drive targets is alignment of the driver beams and the target to within approximately +O. I mm perpendicular to the injection axis and about k0.3 mm along the injection axis. Direct drive targets will require alignment of the centerline of the driver beams with the centerline of the target to less than about ~ 0 . 0 2  mm. For indirect drive targets (Fig. l), the polystyrene capsule is fabricated by a similar microencapsulation process, then the hohlraum components are prepared from the “inside out” using a Laser-Assisted Chemical Vapor Deposition (LCVD) process (Fig. 2). This allows precise control of the hohlraum component density and geometry, and avoids precision machining and assembly steps. IV. TARGET FABRICATION FACILITY DESIGN AND COSTING ANALYSIS Long-term R&D programs will be needed to develop production processes that can manufacture targets at low Summary of Process Steps 1) Fabricating the spherical capsule 2) Fabricating the hohlraum case 3) Fabricating the radiators 4) Filling the capsule with fuel 5) Cooling the capsule to cry0 6) Layering the DT into shell 7) Assembling the cry0 components 8) Accelerating lor injeaion 9) Tracking the target’s position 10) Providing steeringltiming info Fig. 2. Heavy ion fusion target fabrication process. cost. Major paradigm shifts and evolution in manufacturing technology will continually reduce the costs of each target. Therefore, estimating the cost of targets requires one to select a single time frame in the evolution of target manufacturing. We define our “point of evolution” for cost estimating purposes to be the complete optimization (Le., nth-of-a-kind plant) for the current-day understanding of target manufacturing processes. To help identify major cost factors and technology development needs, we have utilized a classical chemical engineering approach to the TFF. We have identified potential manufacturing and handling processes for each step of production, and have evaluated the raw materials, labor force, cost of capital investment, and waste handling costs for providing 500,000 targets per day. We have prepared preliminary equipment layouts, and determined floor space and facility requirements. The purpose of this is not to provide a final plant design, rather to show that production of targets at the required throughput rates and at low cost is feasible. The analyses utilize standard industrial engineering cost factors. In these analyses, it is assumed that the power plant produces its own tritium which is extracted from the breeding material and purified - the cost of doing these steps is not included in the TFF cost and must be considered separately. The per-target cost basis is for current-year dollars; one can assume an escalation factor of 3% to 5% per year until plant construction takes place. 1V.A. Direct Drive Target Cost Analysis Results We have prepared preliminary equipment layouts (Fig. 3), and determined floor space and facility requirements for nth-of-a-kind production of high-gain laser-driven IFE targets. The results for a 1000MW(e) baseline plant indicate that the installed capital cost is about $100M and the annual operating costs will be about $19M (labor $9M; materials/utilities $4M; maintenance $6M), for a cost per target of slightly less than $0.17 each. IV.B. Indirect Drive Target Cost Analysis Results Compared to the direct drive target, the heavy ion driven, distributed radiator design has additional hohlraum components -but has a simpler capsule design. Changes to the original target design to reduce manufacturing costs are underway. Final choices for the hohlraum materials are still being evaluated, and individual target materials may or may not be recycled. Recycling reduces the radioactive waste streams from the facility, but requires a higher level of material purification and also requires remote (and/or contaminated) manufacturing process steps. Assuming a polystyrene capsule and use of a Pb/Hf mixture for the hohlraum components (and no near-term recycling of hohlraum materials), the estimated cost for target mass- production is about $0.41 each. While optimizing of the target design and fabrication processes will certainly continue, this is a very encouraging result with respect to meeting target supply cost goals. GENERAL ATOMICS REPORT GA-A24429 3 COST-EFFECTIVE TARCRT FABRICATION FOR INERTIAL FUSION ENERGY D.T. GOODIN, et al. 0 Chemical engineering approach to Target 0 Costing is done for an “nth-ofa-kind” plant 0 Results guide process development Fabrication Facility (TFF) Maior Parameters 0 500,000 targets per day 0 2-3 weeks on “assembly line” 0 Installed capital of $97M 0 Annual operating cost of $19M 0 Cost per injected target estimated at 16.6 cents Seal Coat Formation \ TFF layout for high gain target mass-production Fig. 3. Estimated cost of laser-driven high-gain target mass-production is less than $0.17 each. The Pb/Hf mixture entails an energy penalty in the gain of the target, and other materials may eventually be preferred.a Pb/Hf allows once-through use then disposal of the materials. Other materials, with higher procurement or disposal costs may necessitate recycling. Requiring near- term recycling of hohlraum materials adds significantly to the per-target cost, due to the need for remote handling and maintenance in the facility. V. CONCLUSIONS An initial estimate for capital and operating costs for a Target Fabrication Facility to support Inertial Fusion Energy, both laser-driven and heavy ion driven, has been “Tungsten is another potential hohlraum material that would reduce the chemical toxicity concerns of using Pb/Hf. However, tungsten will precipitate as a solid from the molten salt coolant and removal systerms must be provided in the primary coolant circuit. The energy penalty would also be greater for tungsten as compared to Pb/Hf. prepared. The results show that targets are within the range of commercial feasibility for fusion energy. ACKNOWLEDGMENT Work in the U.S. supported by NRL Contract N00173- 02-C-6007 and the U.S. Department of Energy under Contract DE-AC03-98ER54411. REFERENCES 1. D.T. GOODIN, A. NOBILE, J. HOFFER, A. NIKROO, G.E. BESENBRUCH, L.C. BROWN, J.L. MAXWELL, W. R. MEIER, T. NORIMATSU, J. PULSIFER, W.S. RICKMAN, W. STECKLE, E.H. STEPHENS, and M. TILLACK, “Addressing the Issues oj‘ Target Fabrication and Injection jbr Inertial Fusion Energy,” Proc. of the 22nd Synzp. on Fusion Technology, Helsinki, Finland, 2002, to be published in Fusion Engineering and Design. J.D. SETHIAN et al, “Fusion Energy with Lasers, Direct Drive Targets, and Dry Wall Chunzhers,” accepted for publication in Nucl. Fusion. 2. 4 GENERAL ATOMICS REPORT GA-A24429 D.T. GOODIN, et al. COST-EFFECTIVE TARCRT FABRlCATlON FOR INERTIAL FUSION ENERGY 3. D.A. CALLAHAN-MILLER, M .  TABAK, “Increasing the Coupling Efficiency in a Heavy Ion, lnertical Confinement Fusion Target,” Nucl. Fusion 39 1547 (1999). R.W. PETZOLDT, D.T. GOODIN, A. NIKROO, E. STEPHENS, N. SIEGEL, N.B. ALEXANDER, A.R. RAFFRAY, T.K. MAU, M. TILLACK, F. NAJMABADI, S.I. KRASHENINNIKOV, and R. GALLIX, “Direct Drive Target Survival During Injection in an Inertial Fusion Energy Power Plant,” Nucl. Fusion 42 135 1 (2002) . 5. J. STREIT and D. SCHROEN, “Development of Divinylbenzene Foam Shells ,for Use as Inertiul Fusion Energy Reactor Targets,” Fusion Science and Technology 43 32 1 (2003). 4. 6. W.S. RICKMAN and D.T. GOODIN, “Cost Modeling for Fabrication of Direct Drive Inertial Fusion Energy Targets,” Fusion Science and Technology 4 3  353 (2003). 7. D.T. GOODIN, et  al., “Progress Towards Demonstrating IFE Target Fabrication and Injection ,” Proc. of the 2nd International Conference on Inertiul Fusion Sciences and Applicutions, Kyoto, Japan (2001). D.T. GOODIN, et al., “A Credible Pathwayfor Heavy Ion Driven Target Fabrication and Injection,” Proc. of the 15th Internatrionul Symposium on Heavy Ion Fusion, Moscow, Russia (2002), Laser and Particle Beams Vol. 20, Issue 3 515 (2003). 8. GENERAL ATOMICS REPORT GA-A24429 5 

Cost-Effective Target Fabrication for Inertial Fusion Energy

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