ARIES-Pathways Project Meeting Minutes
21-22 January 2009
University of California, San Diego, San Diego, CA
Documented by L. Waganer
Ref: Agenda and Presentation Links: Meeting Agenda
Welcome/Agenda - Rene Raffray welcomed the ARIES team to UCSD, advised the team of the available facilities, and provided refreshments. Les Waganer summarized the meeting agenda to update the ARIES-Pathways status, debrief the recent FESAC meeting, discuss the ReNeW engagement, summarize the HHFC workshop results, present the Pathways technical results, display the systems code status, decide the Advisory Committee involvement, discuss the ARIES long-term planning, and mention the future conference/symposium/publication actions.
Next meeting and call - The next meeting will be hosted by Laila El-Guebaly at the University of Wisconsin, Madison, on 23-24 April 2009. The meeting arrangements will be forthcoming. The next call will be on Tuesday, 17 February 2009.
Project Plans and General Scope
Farrokh Najmabadi explained the scope and execution of ARIES-Pathways has changed from the original plan as a result of recent OFES response to the Congressional request for a bold strategic plan for fusion research and the engagement of the ReNeW themes and subpanels. What can ARIES-Pathways now bring to the table? As an independent team, OFES may ask ARIES for an objective assessment of research proposals. Our improved systems code and our experience with TRLs may provide quantitative tools and guidance for the fusion community. Farrokh is striving to develop a lasting framework to help guide and formulate future technology assessments. He suggested taking a single important Greenwald theme as an illustrative example. He mentioned the ReNeW themes are to identify and define the necessary R&D and the associated time phasing. Farrokh recommended targeted involvement of the ARIES team members in the ReNeW panels to help inject the roll-back requirements thinking.
Summary of January 09 FESAC Meeting/ReNeW
General Debrief of FESAC Meeting - Dale Meade summarized the key points of the Jan 09 FESAC meeting. ARIES team members on the FESAC panel are Farrokh Najmabadi, Dale Meade, and Mike Zarnstorff. TRL presentations were made by Mark Tillack and Daniel Whelan, Chief Scientist for the Boeing IDS business unit and expert in TRL utilization. Rene Raffray and Les Waganer were in the audience.
Pat Dehmer, Deputy Director for Science Programs, presented some slides she had just briefed the DOE transition team. She affirmed that fusion is not ready to pursue technology development. She realizes short term energy needs trump long term energy solutions. Fusion must manage its technology roadmap to plan its future R&D.
Dale said that Steve Eckstrand, acting Associate Director for Fusion Energy Science, outlined the ongoing OFES projects and the new activities leading to the strategic plan of fusion with the support from ReNeW theme teams. He mentioned the recent ITER design review and upcoming technical and cost benchmarking.
Riccardo Betti, FESAC Vice-Chair, presented the High Energy Density Laboratory Plasma (HEDLP) workshop results and provided insight into the HEDLP technology and visions.
Debrief of M. Tillack's TRL Presentation - Mark Tillack explained splitting his general and fusion-specific TRL presentations so that David Whelan could inject his discussion of Boeing's TRL usage. Mark mentioned that he had briefed several fusion seminars, conferences, workshops, and the OFES staff on the TRL methodology and illustrative examples and these briefings received a broad acceptance of the methodology. Mark informed FESAC about the TRL purpose, methodology, and utilization by branches of our federal government and many industrial areas. He presented the definition of the nine TRL levels.
After David Whelan's presentation, Mark continued with an illustration of fusion-specific TRL applications. He presented several TRL definition examples (blanket and plasma controls) to illustrate usage and benefit of this methodology.
Debrief of D. Whelan's TRL Presentation - Les Waganer attended the FESAC meeting and debriefed David Whelan's presentation. The intent of the Boeing briefing was to show pre- and post-TRL approaches to measure and mature technologies for military and commercial aerospace products. David Whelan showed examples of failures and successes along with current and future TRL utilization. From the audience engagement and questions and answers, it was evident that he was viewed as an expert in TRL utilization.
Debrief of R. Raffray's HHFC Workshop Results Presentation - Rene Raffray outlined the purposes and breadth of the participants, the depth of the technical discussions and the plan to publish the technical results in a referred journal. The technical presentations from the HHFC Workshop are available on the ARIES web site. One significant consensus result of the workshop was that the Demo/Commercial divertor must be significantly different from the ITER water-cooled divertor. Rene presented a slide illustrating that the Demo/Commercial divertor effectively mandates the use of helium-cooled tungsten as the plasma facing material. Said Abdel-Khalik mentioned that this is a critical material need that must be resolved. The issue is the increase of the ductile-to-brittle transition temperature (DBTT) of tungsten when irradiated at temperatures below ~ 800° C.
Another critical need is the inability for the plasma facing components to withstand multiple high energy ELMs and/or VDEs. This mandates redesigning the plasma control systems to eliminate or significantly mitigate the frequency and/or energy level of the ELM, VDE, and disruption events. The plasma control system seems to be the more promising solution in the double-null plasma configuration.
Plans for Harnessing the Fusion Power ReNeW Theme - Rene Raffray, as vice chair for this theme, mentioned that this HFP team will identify and define the technology gaps and the R&D necessary to close those gaps over the next 20 years during the ITER-era. Approximately 15 research thrusts will be identified to address the identified needs and help form the OFES strategic plan for the next 20 years. A Harnessing Fusion Power workshop meeting is planned for 2-4 March 2009 at UCLA with most subpanel members participating. Other themes will have similar workshops on other dates. White papers are encouraged to promote and discuss research thrusts.
ARIES-Pathways Task Results
ARIES-AT Radial Build Definition: DCLL Blanket with Thin SiC Inserts - Laila El-Guebaly explained her progress to redesign the ARIES-AT power core with the DCLL blanket with thin SiC inserts. The intent is to make the minimal configuration changes to the ARIES-AT design while accommodating the unique DCLL features. She compared the blanket designs and the radial build/material composition differences. One change was the replacement of the SiC-composite structure of the blanket and high temperature shield by ferritic steel with the inclusion of He coolant and SiC insulating inserts in the heat transfer channels of the blanket to mitigate the parasitic MHD fluid drag. S. Sharafat, UCLA, has recommended a sandwich composite (by Ultramet) of SiC foam and dense CVD SiC face and end sheets to seal the foam from infusion of the lithium-lead. The 0.5-cm Ultramet SiC design has similar thicknesses to the fully dense SiC insert of the referent ARIES-AT design, but due the decreased density, the TBR is better for the composite Ultramet insulating layer. Laila showed the recommended radial builds for the ARIES-AT DCLL power core. The placement of the conducting shells is to be determined. Laila examined the engineering impacts that eventually lead to a higher cost of electricity, namely, larger radial stand-offs, inboard manifolds are not reweldable near the power core midplane, decreased blanket lifetime, much lower blanket structure cost, significantly higher pumping power, and much lower thermal to electricity conversion efficiency. Zoran Dragojlovic has investigated the economic impact of the DCLL design changes in a following presentation.
He-Cooled Divertor Options and Analysis - Xueren Wang illustrated the current plate-type divertor design concepts for ARIES-CS and AT including a description of the construction and flow routing. The lower neutron wall load in ARIES-AT (1 MW/m2) compared to ARIES-CS (1.7 MW/m2) in the area of the divertor plates required some design modifications in order to avoid excessive thermal stresses. Based on his thermal and stress analysis, Xueren has developed some design variations. He also analyzed the transient heat load conditions based upon startup timeline from ARIES-I and found that the stress levels are within the design limits. Compared to other design concepts such as the T-tube and the modular finger design, the plate-type divertor has an advantage due to the lower part count, but is limited to heat loads around 8 MW/m2.
An alternate divertor configuration is the combined plate (for lower heat load areas) and the finger design (for higher heat load conditions). The original finger concept is based on the HEMJ (FZK) design concept. It has the advantage for higher heat loads, but the parts count goes way up. A combined plate/finger design can accommodate both moderate and high heat loads and the parts count is much reduced from the pure finger design. Xueren showed a CFD thermal analysis of the integrated finger/plate design that showed acceptable thermal and stress results.
Xueren also showed the T-Tube divertor design that had been proposed for the ARIES-CS design that handles 10 MW/m2. No analysis has been done with the ARIES-AT thermal loads.
Recent Analysis and Results for Helium-Cooled Divertor Module Experiments - Said Abdel-Khalik reported on the recent Georgia Tech analysis and results to validate the leading gas-cooled divertor module conceptual designs and analyses. These designs rely on jet impingement of high pressure gases to greatly enhance the turbulent heat transfer coefficient (HTC). The experimental purpose is to validate the analytical methods to enable design optimization and sensitivities to manufacturing tolerances. Test models were fabricated to closely duplicate the mechanical and hydraulic conditions of the divertor design. Instrumentation was provided to achieve the accuracy for CFD code validation. The FZK helium-cooled multi-jet, the ARIES-CS T-tube, and the ARIES-TNS plate designs were modeled, including foam HTC enhancements. The details of these designs were shown and how the experimental setup duplicated the design features. The tests were run with room temperature air and the hydraulic parameters were corrected to match the high pressure helium coolant. Extremely high turbulent heat transfer coefficients and related pressure drops were measured, which validated the predicted results. Some design concepts and design variations performed better, but all did very well. The results were compared to different CFD analytical models - the k-? turbulence model over-predicted the HTC by ~15-20% whereas the simpler Spalart-Allmaras model over-predicted the HTC by only ~2-5%. The latter model is recommended for use in this geometry, flow, and pressure regime.
ARIES-Pathways System Code Development
An Advanced Computational Algorithm for Systems Analysis of Tokamak Power Plants - Zoran Dragojlovic summarized the purpose of the code improvement is to provide a comprehensive analytical tool to represent and analyze the performance and economics of a wide design space of tokamak physics and engineering parameters. State-of-the-art physics models and engineering design approaches and modeling are included in the new systems code. A large physics space is generated and the results are filtered to provide a viable input set of data to the engineering model. In this engineering model, filters are employed to bound the plant electrical output to the desired range and to limit the design solutions to those deemed feasible and viable. In addition to analyzing the performance parameters, the power core geometry and physical features are determined. The power core geometry is based on the ARIES-AT configuration. After filtering the engineering parameters, the data sets are transferred to the costing module to generate economic data for post-processing analyses.
A very large physics database was input into the code to generate engineering and economic data related to the major plant parameters. The results were displayed in 3-D plots. The plots were a bit granular due to the use of a limited number of optimal solutions at the specified parameters, but were useful to illustrate general trends. Some plots were useful to engineers whereas others were of value to physicists. The ARIES-AT data point was added to several plots, but it should be clearly noted that this point does not have the same plasma radiation characteristics as the plotted data.
Another set of analyses compared the original ARIES-AT SiC/LiPb blanket with the proposed DCLL blanket. The normalization was chosen to hold most of the reactor core design parameters, including fusion power, constant and let the radial build geometry, recirculating power, net power, and COE vary. It was suggested that a better approach might be to hold the net electric power constant. It was observed that the coil and cryostat geometry did not see to be correct (too elongated vertically) and the pumping power was way too high (greater than 1 GWe). These errors propagated into the costing data. Laila suggested keeping a distance of only one meter between the VV and coil in the vertical build. Action item - Zoran and Rene should investigate the power modeling and make appropriate corrections.
Status of Advisory Committee Involvement
Ken Schultz wanted to resolve the utilization of the ARIES-Pathways Industrial Advisory Committee, which has been on hold for well over a year. It was concluded this advisory committee had fulfilled its obligation and has provided the ARIES team with valuable program direction. Action Item - Ken Schultz should contact the Committee and thank the committee members for their contributions.
The next topic was to consider if the ARIES program needs a Program Advisory Committee consisting of senior people familiar with fusion to help guide the program. It was thought to be useful, as it has been on other programs. However, it was envisioned to be difficult to maintain a continued interest and participation of senior people over an extended time period. No feasible solution was found to maintain interest. The use of infrequent workshops of program technical results and planned activities was thought to be useful and feasible for continued interest. Action Item - This approach, key questions for outside experts and possible participation will be investigated by Dale Meade.
ARIES Planning, Near and Long Term
The ongoing, near-term tasks of refining the systems code, designing and analyzing the helium-cooled divertor, and the incorporation of the DCLL blanket into a prior ARIES design should continue. Mark Tillack, with the help of other co-authors, should prepare the interim TRL report to be published in the FED journal (Action Item).
Several of the ARIES team members have already volunteered to serve on the ReNeW teams and others were interested. All team members should examine the ReNeW goals and theme organization to determine if they could contribute to the subpanel results or white paper submission (Action Item). After the June 09 ReNeW community workshop results are known, the near-term FY09 ARIES goals should be reassessed.
The utilization of the TRL methodology on several of the ReNeW themes was noted, especially those with ARIES team member involvement. Dale Meade volunteered to see if a wider utilization of the TRL methodology might be beneficial on the ReNeW teams in general (Action Item).
The longer-term project goals were discussed. A few ideas will be developed by Farrokh Najmabadi in the near future (Action Item).
ARIES Future Technical Submissions
Rene Raffray discussed the upcoming US/Japan Reactor Design Workshop to be held in Tokyo, Japan in March. He knew of a few people who planned to attend and present papers and inquired if others wished to participate. The team also discussed this year's SOFE conference at San Diego in June 2009, ICFRM (September 2009, Japan), and ISFNT (October, 2009, China). If you are interested in attending/presenting at any of these conferences, note abstract submission dates (Action Item).