Journal of Fusion Energy, Vol. 17, No. 2, 1998

U.S. Industry's Perspective on Fusion's Next Step

John Davis1 and William R. Ellis2

A perspective is offered on the perspective of U.S. industry on the need for a next step facility forfusion energy development.

KEY WORDS: fusion, industry.

INTRODUCTION

History provides an opportunity to learn from ourpast. CIT/BPX, TPX, and now ITER were found to costmore than the funding agencies were willing to endorsefor the benefits received. Since the international partnershave approved a three-year transition period to explorecost reduction strategies, the fusion community must mar-shal all its resources to provide an improved ITER-likedevice that is affordable and acceptable to the interna-tional parties. We must resist the temptation to merelyreduce the scope of the machine because that severelylimits the return on the investment, particularly in theinformation it provides on fusion technology develop-ment, which is what makes it attractive to our interna-tional partners. U.S. industry believes that the major nextstep for fusion experiments can and should address criticalengineering technology problems as well as plasma phys-ics issues. We must seek to define a machine that advancesfusion toward the goal as a commercial energy source,not simply a device to study advanced plasma physics.Industry can, and is willing to, help define an affordable,useful experimental test facility.

U.S. industry has been actively supporting fusiondevelopment in a variety of roles since the late 1970's.Initially industry was viewed strictly as a parts or compo-nent supplier. Drawings were provided and industry was

1 The Boeing Company.2 Raytheon Engineers and Constructions.

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asked to essentially build-to-print. A change to thisapproach began in the TFTR bumper/limiter program.On this program, industry introduced a relatively newintegrated design/manufacturing tool called computer-aided-design/computer-aidedmanufacturing (CAD/CAM). In this process the graphite tiles were modeledon a computer and the drawing information was electroni-cally sent to a numerically-controlled milling machine toproduce the parts. The net result was that, of 550 differentdesigns and 2500 parts machined, the number of tilesrequiring rejection or rework was less than 1%. Anotherexample of how industry helped to change the manufac-turing approach was in the TFTR inner support structure.Diffusion bonding was used to produce the titanium struc-ture, resulting in considerable cost savings over a formingand welding approach.

Over the years, industry has learned that the build-to-print approach is expensive and frequently requiresrework when suppliers cannot meet the design tolerancesor scale up the fabrication processes specified. It alsoremoves the ability of industry to contribute its experienceto improve the design. Industry has found that 80% ofthe cost of a system/component is locked in at the comple-tion of the design. Thus, design innovation to improvemanufacturability or simplify assembly needs to be incor-porated early. Increased worldwide competition hasforced U.S. industry to adopt a better approach of bringingsuppliers into the design process. This approach has anumber of different names, such as concurrent engi-neering (CE) or integrated product teams (IPTs). The key

0164-0313/98/0600-00133$15.00/0 C 1998 Plenum Publishing Corporation

134 Davis and Ellis

point is that the component manufacturers need to be anintegral part of the design process. While this conceptwas begun with CIT/BPX, it was with TPX and ITERthat industry was brought in as a full partner to participatein the design phase of experimental facilities.

INDUSTRIAL SUPPORT FOR FUSION'SNEXT STEP

Industry's survival today requires that products notonly meet the customer's performance expectations, butalso are affordable, whether that product is commercialaviation, an automobile, or a fusion device. In the 1990's,industry reexamined itself and looked for ways to reducecosts while delivering an improved product. Implement-ing commercial practice is a phrase frequently used bythe defense industry to eliminate elaborate procurementpractices and specifications that increase cost. In additionto CE and IPTs, another practice that can be applied isdesigning for manufacturing and assembly (DFMA). Allthese skills need to be brought into the design of the NextStep fusion experiment. Since the design phase largelydetermines the final cost, continued industrial involve-ment is essential to assure affordable concepts evolve.Industry has the tools and knowledge base to accom-plish this.

Regardless of the next type of machine proposed,the attainment of cost goals will be a challenge. Forexample, CIT/BPX (a D-T machine with a 5-second burn,inertially-cooled chamber, with normally conductingmagnets, no nuclear technology mission, and no addi-tional facilities) was estimated to cost $1.8B. The TPX(a D-D advanced physics machine with a 1000-secondburn, actively-cooled chamber, superconducting magnets,minimal shielding, no nuclear mission, no tritium han-dling system, and no additional facilities) was estimatedto cost $0.8B. Creating a D-T burning plasma machinewith a 1000-second burn, superconducting magnets,actively cooled components, large-scale tritium handlingsystem, full shielding system, and a meaningful technol-ogy mission at a cost goal of $5-6B is a formidablechallenge requiring the combined ingenuity of industry,national laboratories, and universities.

An ITER-like, long-pulse machine is preferred overa short-pulse copper-coil machine for several reasons.First, it provides a better opportunity to develop, integrate,and evaluate key first-generation technologies needed toengineer future magnetic fusion reactor systems. Itinvolves the fabrication, integration, and operation oflarge-scale magnet, blanket, and divertor components.Second, it will develop critical nuclear effects data along

with reliability, availability and maintainability informa-tion for these components and systems that can be usedto improve future designs. Third, the size of plasmaneeded to achieve energy gain ratios (Q-values) in excessof 10 must be large enough and have sufficient plasmatemperature to have plasma profile equilibration times ofa few hundred seconds. Similarly, the plasma exposuretime required to reach an equilibrium particle balancebetween the plasma and the first wall or divertor is alsoseveral hundred seconds (Tore Supra has shown thismost clearly).

The development of reliable blanket and divertorcomponents for fusion reactors will require extensive,evolutionary testing of these components in the combinedneutron, heat flux, and structural loads expected in areactor-like environment. It is only through the integratedtesting of components that the potential failure mecha-nisms can be found and corrected. The data provided byan ITER-like, long-pulse machine is much more relevantthan that provided by a short-pulse copper machinebecause it forces the incorporation of steady-state heatremoval systems and significantly reduces (factor of 10or more) the number of thermal-fatigue cycles requiredto reach a given fluence level. Thus the fusion-nucleartechnology database and component design experiencecoupled with the burning plasma physics data more thanjustify the added expense of a superconducting, long-pulse machine.

During the EDA transition period (over the next 2-3years), there are a number of tasks where industry canmake meaningful contributions. In the design area, indus-try can provide inputs into the lower cost option (LCO)studies. These inputs to explore the lower cost optionscan be to:

1. Provide individuals or teams to brainstorm thebroad issue of reducing ITER costs and determinechanges that can be incorporated to reduce manufactur-ing costs.

2. Develop "level-playing-field" methodology forcomparing various design options, e.g. superconductingversus normal coils.

3. Use cost estimation techniques to benchmark theSupercode cost predictions.

4. Work with the Physics community to develop andreview design concepts and cost estimates for advanced-physics machines.

In the technology area, it is important to continue"dual-use" technology development activities that canbenefit the domestic program as well as internationalcollaborations. As an example, reliable, actively-cooled,

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high-heat-flux plasma facing components will be neededin any Next Step device. Hence, the U.S. should:

1. Continue the manufacturing development andenvironmental testing begun during the EDA to establisha sound basis for component cost, performance, and relia-bility projections.

2. Continue to explore advanced manufacturingoptions that can leverage significant cost savings if suc-cessfully demonstrated.

In summary, the ITER design process that hasevolved over the course of the EDA period providesimportant avenues for input from industry. The JCT hasworked with industries from all parties to improve the

baseline ITER design concepts. The parties have beenencouraged to explore alternative manufacturing solu-tions that improve producibility and/or lower cost. Thiswill be even more important during the EDA transitionperiod. Industry has been a source of creativity on ITERand can contribute with new design tools and ideas, com-puter modeling codes, and fabrication approaches. Themajor next step for fusion experiments can and shouldaddress critical fusion technology issues as well as plasmaphysics. We must seek a machine that advances fusiontoward the goal as a commercial energy source. Industrycan, and is willing to, work with national laboratoriesand universities to define an affordable Next-Step facilitythat provides meaningful fusion technology informationand remains attractive to our international partners.