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ARIES-Pathways Project Meeting Minutes

3-4 March 2008

University of California, San Diego, CA

Documented by L. Waganer

Organization ARIES Pathways Project
Boeing Waganer, Weaver
General Atomics Schultz, Turnbull
Georgia Tech Abdel-Khalik
MIT Bromberg
PPPL Meade
RPI Steiner
UCSD Dragojlovic, Malang, Mau, Najmabadi, Raffray, Tillack, Wang
UW-Mad El-Guebaly

Ref: Agenda and Presentation Links: Meeting Agenda


Welcome Rene Raffray welcomed the ARIES team to UCSD. The University provided snacks and refreshments for the group. Les Waganer reviewed the meeting agenda.

Plans and General Scope (of ARIES Pathways Study)

Farrokh Najmabadi described a new planning process implemented by the new associate director for the Office of Fusion Energy Sciences, Ray Fonck. In addition to the Greenwald panel that identified and prioritized broad scientific and technical questions to be answered, DOE is contemplating some upcoming workshops to help plan R&D efforts spanning ITER and Demo. Potentially, the ARIES Pathway project may be able to be of some assistance in this area. The Technology Readiness Level (TRL) metrics may help quantify the planning needs and ability of the proposed facilities and programs.

ARIES Pathways Technical Working Groups

Overview of Technical Working Group Issues, TRL Definitions, and Interim Report - Mark Tillack described the Technical Working Groups' progress to develop an evaluation methodology for R&D bridging the gap between ITER and the US demo. Mark reiterated the basic TRL definitions as a means to quantify the maturities of technologies to be implemented in solutions. GAO has encouraged DOE to employ TRLs to develop a common language, stakeholder communication, identify maturation gaps, expose risks and clarify the decision making process. Mark has organized the TWGs along the lines of the previous advisory committee recommendations. The intent is to identify technologies based on their functional characteristics as opposed to hardware disciplines. However, an end goal is needed to tailor the technologies to be employed in a viable product. Dale Meade asked about how to model and decide between moderate technology and high technology solutions for both physics and engineering.

It was evident that the Pathways program has something to offer to DOE and a meeting between the ARIES leaders and OFES is recommended to be held in the immediate future.

Technical Readiness Level for Control of Plasma Power Flux Distribution - Alan Turnbull stated that an attractive (viable) power plant will require all energy release pathways to be adequately controlled. The described TRLs are intended to identify the technologies to control these energy release pathways. The radiative divertor is the most promising solution for controlling radiation and localized energy fluxes, however there are three major sources of uncertainty: small parameter window for proper detachment, accelerated runaway electrons, and ELM and Sawtooth power fluctuations. The TRL methodology will help define an incremental pathway to an acceptable solution. Alan illustrated his vision of the TRL definitions. After discussion, he should probably downgrade his metrics one level.

Alan did not speak on Plasma Control technology.

TRL for Heat and Particle Flux Handling - Rene Raffray described the scope of the heat flux and particle handling technology for magnetic fusion facilities. He outlined the key scientific and engineering challenges both for theory and experiments. He identified both existing and future facilities that would further the maturation of the related technologies. He presented a clear TRL definition of this specific technology for each level of maturity along with the corresponding facilities to achieve that level of maturity. Rene recommended that this technology would be highly appropriate for the first wall and divertor components, but the blanket and tritium breeding components would be better suited to the power handling technology function.

Power Conversion and Component Lifetime (two topics) - Mark Tillack discussed the technology for high temperature operation and related power conversion. There are many key science and engineering challenges, such as mass transfer at high temperature, surface chemistry changes, and degradation of material properties via chemical changes, irradiation, and continued high temperature exposure. He elaborated on the existing and potential test facilities. TRL definitions for high temperature power conversion were shown.

It is a very important issue to extend the lifetime of the power core components. Their lifetime is determined both by normal operation as well as off-normal events. It is imperative to identify and quantify the component lifetime, reliability, and failure rates. Key challenges include neutron damage, particle erosion, corrosion, damage from plasma disruptions and ELMs, and fatigue from thermal cycling. Categories of testing facilities were identified. Related TRL definitions were provided.

Economic Power Production and Reliable Plant Operations - Les Waganer had four topic areas to present. Power core fabrication was functionally under economic power production TWG, whereas reliable plant operations TWG included plasma diagnosis and control, plant integrated control, fuel cycle control and maintenance.

The technology related to power core fabrication is the development and maturation of the technology to fabricate low cost, high efficiency, and long lived power core components. Existing fabrication techniques are either too expensive or may not be able to fabricate the complex parts. Les described a detailed (actually too detailed) set of advanced fabrication TRL definitions. He also presented a vision of advanced fabrication later in the meeting.

Under the Reliable and Stable Plant Operations, one TRL definition can describe the control functions for the plasma diagnostics, integrated plant control, and fuel cycle. All these control systems have separate and unique technologies but they can be measured with a common set of TRL definitions that Les described. Les also described the control issues, the key parameters, the components considered, and the desired end states.

The remaining operations technology is maintenance and that technology must offer reliable and efficient maintenance of the power core, hot cell, fuel handling, and other remote-access plant systems. Les again described the maintenance issues, the key parameters, the components considered, and the desired end states. Related TRL definitions were described. It was suggested that all his TRLs be simplified.

Tritium Inventory and Control; Activation Inventory and Release; Waste Management - Don Steiner addressed tritium control and containment and thought a lot of technology can be garnered from fission experience. However the ITER tritium systems would not be sufficient to serve as a proof of principle for a reactor scale technology. Fusion must keep the release of tritium <1 rem at the site boundary. There is also a great concern about the technology necessary to have adequate tritium accountability with a power plant scale operation.

Topics About Pathways Project Approach and Vision

Licensing Options for the First US Demonstration Fusion Power Plant - Said Abdel-Khalik described how the NRC might engage in the development and licensing of fusion facilities including Demo and future power plants. A good evolving example is the NGNP (Next Generation Nuclear Project) authorized by the Energy Policy Act of 2005 whose construction is to be completed by the end of FY2021. Said mentioned they have a tentative schedule for plant design and construction. He also discussed the differences between the older 10 CFR Part 50 and the new 10 CFR Part 52, which will enable a more timely and less risky licensing procedure with standardized design approvals. Said was sure the NRC will take an independent role in evaluating the license application of fusion facilities. The licensing strategy will likely be based on the 10 CFR Part 52 approach and asking for a combined construction and operating license. It would be wise to engage the NRC early to make sure that we and they will obtain the necessary data.

Risk and Opportunity Management - Tom Weaver first defined the terms: Issue, Opportunity, and Risk. He then described the orderly, systematic continuous practice of identifying, analyzing, handling, communicating, and tracking risks, issues, and opportunities. Creating and executing related plans is essential to achieving the desired results, both for the program as well as the customer. Tom then showed the risk and opportunity graphics that illustrate how these metrics are identified and tracked as they improve. He also described the probabilities, consequences for both risk and opportunities. He described several examples of each type.

Approach for High Performance Plasma Development Pathway - Dale Meade pointed out the principle issues for commercial fusion is the list of the issues identified by Mark Tillack in his TWG list, namely, power management, safety and environmental, and reliable and stable plant operations. Dale listed the issues and metrics for the fusion power source, including graphics to show progress. He pointed out four of the major source control metrics and the current gap to achieve viable commercial operation. Certainly, the fusion power source must have high gain, sufficient power density and be sustainable, which infers control and compatible interface with the PFC and other power core elements. Dale then showed his TRL definition for the fusion power source.

Top Level Requirements for Future Fusion Facilities - Don Steiner showed his strawman top level requirements for the Component Certification Facility (CCF), the Materials Certification Facility (MCF), Demonstration Plant (Demo), and Commercial Power Plant. As the facilities progressed from the near term to the commercial plant, the requirements increased in degree, complexity, and level of integration. It was noted this is a good start, but we really need to refine this table after all the separate issues and facilities have been defined.

Advanced Fabrication - A Future Vision for Fusion? - Les Waganer showed that the advanced fabrication he has been advocating for some time has moved into the consumer "novelty" product realm. He illustrated that the additive/subtractive manufacturing research development in Europe has progressed quite a bit in the past few years with some innovative processes and products. Even the form of the basic material can influence the final material properties. Ceramics can be formed using this additive process. But there remain challenges in surface finish, very small scale fabrication, novel microstructures, and commercialization of multiple materials (graded materials). Sciaky, Inc has been making larger structures with a wide range of materials. Les then provided a few possibilities that might be advantageous for fusion applications.

ARIES-Pathways Systems Code Development

LSA Factors and External Costs for ARIES System Code - Laila El-Guebaly summarized the history of the need, origin, and use of the Level of Safety Assurance (LSA) methodology to provide cost credits for safety and environmental improvements. Laila provided the definitions for the four LSA levels. Cost factors are provided for most fusion subsystems, systems, and major cost accounts during plant construction. She recommended continue using the LSA factors in the new ARIES system code and update them when the GEN-IV cost credits become available.

External cost assessments are another area that fusion and other "green" power sources are interested in. It is a method to define some social cost for these attractive safety or environmental attributes after plant operation. EU is a big proponent of this approach, but the US has not yet embraced this concept. These costs are difficult to quantify and justify. In the future, there may be a carbon tax or other environmental assessment levied on or granted to certain types of power producers. Laila recommended the addition of 1-2 mills/kWhr be added to account to fusion external costs. This implies that this type of external cost would be added to other competing power sources. Fusion will compete favorably when external costs are added to all energy sources.

Preliminary ARIES-AT-DCLL Radial Build for ASC - Laila El-Guebaly has been defining the preliminary radial builds for the DCLL blanket option for inclusion into the ARIES-AT design. She has been highlighting the impact of using the DCLL systems with stabilizing shells. She presented the ARIES-AT radial builds with the DCLL blanket system and noted the primary changes, design updates, and underlying assumptions. Tentatively, she located the manifolds behind the shield pending recommendations from Rene, Siegfried, and Xueren. Stabilizing shells also need to be added and Chuck Kessel has defined them. A ferritic steel kink shell would require a very high voltage and power. Placing the stabilizing shell outside the sizable outboard blanket/shield/manifolds is unacceptable as it results in a major hit to the plasma operating point. The group concluded it would be very difficult to modify ARIES-AT to accommodate the DCLL system. It would be better to adapt the DCLL to the ARIES-RS design. Laila agreed to begin to assess the adaptation to the ARIES-RS concept and will contact C. Kessel to assess the impact on ARIES-RS physics.

Costing of the Magnets (or How can the ARIES coils cost less than ITER?) - Leslie Bromberg stressed that the performance of superconducting magnets after ITER must be increased - masses decrease by a factor of 2 and costs decrease by > 2.5. Leslie showed some resistive performance and cost data from several different sources including FIRE estimates. He also provided cost data on MRI/SMES and ITER magnets and the CS model coil for comparison. He provided some bottoms up data for estimating magnet costs and compared that to the ARIES-ST and ARIES-AT magnet costing. There is some data extrapolating the costs for High Temperature Superconducting performance and costing. Leslie summarized that today's experimental magnets are about 6-10 times more expensive than the commercial plant magnets, however today's magnets are very conservative (costly) and increased quantities and manufacturing innovations will continue to lower the future costs.

Status of the Helium-Cooled Plate-Type Divertor Design, CFD, and Stress Analysis - Xueren Wang described the old and new physical designs of the helium-cooled plate divertor with the thick tungsten tiles attached to the top of the divertor. He then described the cooling arrangements to direct the helium from the inner chamber to the outer chamber with the hot exterior wall. Cooling arrangements are the solid jet, slot jet with micro channels, and multiple impinging jets. He provided analysis results for these approaches. Further, he provided results from a parametric study for design variations. Xueren said the plate divertor has significantly fewer parts (suggesting higher reliability) and the heat transfer and pumping power are acceptable, but so far the thermal stress is higher. Further design options are needed and will be evaluated.

Pathways Project Systems Code Developments

Analysis of Technical and Programmatic Tradeoffs with the Systems Code - Zoran Dragojlovic described the functions (algorithms), the sources of information and when modified. He also provided information about all recent code updates and validations. The TF coil shape and the power flow module are now validated with ARIES-AT. Zoran also validated all the primary component volumes and plant parameters with ARIES-AT. There remain a few plasma and economic parameters to reconcile. Zoran noted the tradeoff parameters to be input or evaluated. As an example, he showed a 3-D COE plot as a function of 4 parameters, but Farrokh noticed that there was an error in the data generation or plotting as the graphics were incorrect. Zoran will recheck the code for the error.

Restructuring Systems Cost Accounts and Algorithms - Les Waganer reviewed the results he reported in the December 2007 meeting. He noted the difficulties in documenting, re-evaluating, and documenting the direct cost accounts. He said that all of Account 22 has never been fully documented - algorithms or cost data. Leslie Bromberg is working on the coil costs. TK Mau and Les are currently working on the heating and current drive. There was some disparity with the prior ARIES reporting of the vacuum system structure and support equipment. Les recommended ARIES use the vacuum structure database from the ARIES-AT study. The divertor costing should be revised to reflect used materials, volumes, and design approach consistent with the thermal and particle loads. Farrokh had previously requested Les compare ARIES-AT with the ITER systems costs. The reported costs seemed to be comparable considering first of a kind to commercial, size, materials, and performance differences. Les suggested Cost Account Managers for ARIES. His next actions relate to finishing up the cost documentation (hopefully by next meeting).

Industrial Advisory Committee Involvement

Status of the ARIES Industrial Advisory Committee - Ken Schultz reminded the group that the Industrial Advisory Committee (IAC) has met only one time on June 2007. At that time, they affirmed the earlier advisory committee recommendations for commercial fusion power. When we consider asking the new IAC to meet again, we never seem to be ready with what we really want them to accomplish. Ken suggested this list:

  • Define non-fusion science R&D issues
  • Help sell attractiveness of fusion
  • Define what is needed to proceed with fusion as an energy source
  • Identify risks to be mitigated and what assurances are required
  • Help evaluate if the current ARIES options will meet their requirements

Ken and Farrokh will continue to draft and refine potential IAC involvement and help. Hopefully, the IAC can meet again in the June 2008 timeframe.