ARIES-Pathways Project Meeting Minutes
23-24 April 2009
University of Wisconsin-Madison, Madison, WI
Documented by L. Waganer
Ref: Agenda and Presentation Links: Meeting Agenda
Welcome/Agenda - Professor Gerald Kulcinski welcomed the ARIES team to the University of Wisconsin- Madison with a brief description of the new activities around campus, including new building construction, increased student enrollment, and new stimulus initiatives. He also discussed the current status and new directions for both magnetic and inertial fusion energy with the advent of the new administration.
Next meeting and call - The next meeting will be hosted by Said Abdel-Khalik and Minami Yoda at Georgia Tech in Atlanta on August 26-27 (all day Wednesday and 1/2 day on Thursday). The next project conference call will be on Thursday, 14 May 2009 to finalize the 3-year project integrated proposed scope of work for FY 2010 and beyond. If there is sufficient time, technical discussions will also be included in the call.
Renew Project Results and Interaction
ReNeW Progress and Future ARIES Involvement - Dr. Hutch Neilson explained that the current Renew process is intended to provide community inputs on the scientific and technology issues and gaps that will exist between the ITER results and the commencement of the Demo, also known as the "ITER Era". There was a question about the definition of Demo so that the end point could be clearly defined. Hutch said the intent was to keep Demo definition somewhat flexible, but some theme areas may need added definition to quantify the issues and gaps. These issues and gaps must be identified, quantified and resolved with targeted research and development thrusts. The Renew results will provide inputs to DOE-OFES to prepare a strategic plan for magnetic fusion. Dale Meade suggested following the High Energy Physics plan as a model. Hutch said that OFES has developed such plans in the past and will formulate an appropriate plan. Don Steiner asked if the thrusts were really facilities - Hutch said the thrusts were an organized, multi-faceted attack on technical issues that are critical to the success of magnetic fusion. There will entail certain necessary existing or new facilities associated with one or more thrusts.
A series of Renew community workshops on five different theme areas were held during March 2009, which were very productive. A higher level Renew workshop will be held in June 2009 to consolidate the prior results into a concise final report to be provided to OFES.
Hutch commended the ARIES team involvement in the DOE Renew process, certainly in critical technical areas with many ARIES team members involved, many white papers written, and valued participation in the workshops. ARIES also provided the Technical Readiness Level assessment tool that helped quantify the current technology state.
Hutch mentioned that risk management is an essential element to the planning process so that the recommended approach would have an acceptable level of programmatic risk. Each identified risk should have a plan to mitigate the identified risk.
Debriefing of Themes I (Burning Plasma Physics in ITER) and II (High Performance, Steady State Burning Plasmas) Workshops - Dale Meade said that these two themes shared a week-long workshop with several ARIES team members attending and contributing with white papers and presentations. The theme areas were subdivided into panels that addressed elements of the overall themes. Nine research thrusts were identified, which will be consolidated for the final report. Dale discussed the identified potential thrusts for these two themes. A table of integration issue gaps was shown that quantified the gaps between present capabilities, those needed for ITER, and those required for power plant facilities.
Upcoming tasks in Theme 1 are to define the ITER baseline and determine if performance upgrades are realistic. In Theme II, the tasks involve quantifying issues and integration needs as well as understanding the hardware proposals.
High Performance, Steady-State, Burning Plasma Theme, Integration Panel - In the Integration panel area, Chuck Kessel summarized three main issues: core dynamics, core-edge coupling, and full integration. The core plasma dynamics involved transport, MHD effects, wave effects, and plasma control. DD and DT experimental facilities may be necessary to resolve these concerns. The plasma core-edge coupling involves heat and particle loads and PFC materials effects. Related thrusts involve understanding tungsten properties and interaction with the plasma, materials testing, long-term PFC testing in an integrated test facility, and controls development for normal and off-normal situations.
Debriefing of Themes III (Plasma Materials Interface) and IV (Harnessing Fusion Power) Workshops - Rene Raffray is the Vice Chair for Theme IV and also participated in Theme III. Both themes shared a week-long workshop. Taming the PMI workshop produced six thrust areas that covered the plasma SOL, PMI research in a dedicated facility, innovative power and plasma handing technologies, next generation divertor, reliable robust plasma edge conditions, and understanding normal and off normal (edge) events.
The Harnessing Fusion Power theme developed three thrusts aligned with fusion nuclear science, fusion materials science, and science-based modeling. One of the recommendations mentioned a need for a more detailed definition of the Demo facility to establish the end goal for the "ITER Era" gap analysis.
Debriefing of Themes V (Other Magnetic Configurations) Workshop - John Sarff explained that this theme was structured differently around magnetic configurations rather than issues, with panels consisting of five magnetic configurations, each of them having the same issue categories as the main line tokamak. Although there are significant differences, there are also a lot of similarities with the tokamak approach. The magnetic configurations considered are the stellarator, spherical torus, reversed field pinch, field reversed configuration, and the spheromak. The latter two were combined as compact toroids. Each configuration defined an issue list of tier 1 (high priority), tier 2 (moderate priority), and tier 3 (low priority) issues. Similar issues were identified for all the configurations. For the final report, these lists may be consolidated to identify common and unique issues. It was felt that issue solutions for these configurations might have some applicability to the tokamak issues at some increased cost.
ARIES Project Planning
Farrokh Najmabadi discussed some ARIES study topic areas that might be appropriate for FY 2010 and beyond. The Renew process has offered some worthwhile topics that need some in-depth analysis to help provide guidance for the fusion community. The combined expertise of the ARIES team can help address and provide integrated point design solutions to the identified issues. The revised ARIES Systems Code will be ready to analyze the proposed solutions and display parametric results on the relevant parameter spaces.
It was recommended each group of the ARIES team provide their input to an integrated statement of work (SOW). This integrated SOW would be presented to OFES so they will have a better understanding of the combined team effort. However, each organization will submit their own proposal, budget, and SOW to OFES.
ARIES-Pathways Task Results
Neutronic Evaluation and Update of the ARIES-DB - Laila El-Guebaly has been redefining a new power core variation of ARIES-AT (ARIES-DB) to compare the SiC/LiPb and the DCLL blanket concepts in a common, adaptable configuration. Some geometry and configuration elements will have to be modified to accommodate the DCLL blanket configurations. Changes she is considering are the location of the manifolds, survivability of shield and re-weldability of the vacuum vessel, magnet structural material, divertor target, and blanket material systems. The design parameters and radial builds for the DCLL blanket system were provided for consideration. Space is very limited in the inboard region so a radial build was provided without inboard manifolds. Laila also provided outboard and divertor regions radial builds without manifolds. With these data, she calculated a 1-D estimate for radiation damage with a safety factor of 3.
Laila El-Guebaly has been redefining a new power core variation of ARIES-AT (ARIES-DB) to compare the SiC/LiPb and the DCLL blanket concepts in a common, adaptable configuration. Some geometry and configuration elements will have to be modified to accommodate the DCLL blanket configurations. Changes she is considering are the location of the manifolds, survivability of shield and re-weldability of the vacuum vessel, magnet structural material, divertor target, and blanket material systems. The design parameters and radial builds for the DCLL blanket system were provided for consideration. Space is very limited in the inboard region so a radial build was provided without inboard manifolds. Laila also provided outboard and divertor regions radial builds without manifolds. With these data, she calculated a 1-D estimate for radiation damage with a safety factor of 3.
Laila analyzed the TBR, but it needs to be reassessed later with the stabilizing shells. She compared the JK2LB and the Incoloy-908 materials for the magnet structures. It was clear that the JK2LB had superior environmental and economic features. She mentioned that the new tungsten alloys are being developed in Europe for first wall and divertor surfaces.
Laila showed a preliminary comparison of the SiC/LiPb and DCLL blanket options with some early observations. She asked the question about the location of the kink shell. She also showed Xueren's isometric view of the outboard blanket with manifolds.
3-D Assessment of Neutron Streaming through Inboard Assembly Gaps - Tim Bohm, UW-Madison, described the gaps that are necessary for assembly and disassembly of the blanket and divertor modules. An identified issue was to determine if additional protection is needed to adequately protect the underlying components, especially on the inboard regions of the power core. Nominally, these gaps are around 2-cm wide, but during operation, these gaps will close, or nearly close, due to thermal and neutronic-induced swelling.
A 3-D analysis was conducted on the ARIES blanket design with gaps ranging from zero width up to 2 cm. A wall load of 3.4 MW/m2 was considered as the nominal neutron wall load. Sidewalls and manifolds were included in the 3-D model. Laila proposed the idea of introducing a WC (or W) shielding block to maximize the attenuation of streaming neutrons. In addition to the straight radial gap, a stepped WC (or W) shielding block was analyzed (with 5-cm offsets). With a zero width straight gap, there was a 6 order-of-magnitude attenuation from the first wall to the vacuum wall. The sidewalls did allow a slightly higher level of neutrons at the vacuum vessel in a local region. The 200-dpa limit was exceeded at the shield and manifold for the zero, 1-cm and 2-cm gaps. The vacuum vessel (VV) and the winding pack were adequately protected with no gap or a stepped gap, but not with a finite straight gap. As expected, finite straight gaps allow too much radiation to the inboard components. Stepped gaps with shielding blocks are needed to protect the VV and magnet. [Siegfried Malang commented later via email that the stepped gaps on the sides of the shielding block could be half the width of the nominal gap. This seems feasible if the increase in the shielding block width (due to neutron-induced swelling at end-of-life and thermal expansion at > 1000oC) does not exceed a few mm (TBD)]
Per conversations with S. Malang, radiative cooling of the WC shielding block is feasible if the average heating is below 15 W/cm3. The 3-D calculations show an average was shown as 3 W/cm3. The choice of W or WC is not yet decided.
Work Plan for ARIES-DB-DCLL - Rene Raffray described the proposed work plan for evaluating the DCLL blanket concept in context of the previously documented ARIES-AT design concept. He thought it was a three-part effort to arrive at an integrated design (ala, ARIES-AT) with sector maintenance for the attractive DCLL blanket concept. The steps are:
Rene foresaw two distinct design cases - with and without manifolds on the space-constrained inboard regions as Laila considered in her analyses. This design would be a new design concept, separate from ARIES-AT, but comparable to that design.
Improved Design of a Helium Cooled Divertor Target Plate - Xueren Wang identified critical design issues for the helium-cooled finger divertor concepts. Several finger designs have been proposed, but these designs may be limited by their cooling capacity and/or number of joined elements that allude to leak failures and lack of reliability. Several ARIES design improvements have reduced these concerns and these improvements were discussed. Xueren showed his thermo-fluid analyses of the modified finger module. A double-wall finger design provides double containment without a significant impact on temperature or stress. An integrated finger/plate divertor concept was shown that is tailored the configuration to the heat load with fewer modules.
The T-Tube divertor concept accommodates a heat flux up to 10 MW/m2 with fewer individual parts and coolant flow paths. Thermo-mechanical analyses were also done on this configuration.
Xueren compared all the divertor module concepts for a power plant application. Xueren thinks the T-tube or the integrated finger/plate concept is best for the DCLL application. Next, he will begin the integration of these two concepts into the ARIES-DB-DCLL design.
Improved Design of a Helium Cooled Divertor Target Plate - Minami Yoda and Said Abdel-Khalik offered a new divertor design approach that can effectively double the heat transfer coefficient. Their design is not optimized yet, however, they tested their first prototype and it met the performance objectives of 20 MW/m2, which doubles the best currently proposed helium-cooled divertors at 10 MW/m2. The heat transfer coefficient (HTC) of these prior designs can be improved with added metal foam (50% improvement) at the expense of much higher pressure losses. The improved design uses arrays of small cantilevered, closely spaced pins in the narrow flow region with only slightly increased pressure losses. Design variations have not been optimized yet and parameterized tests will be conducted to confirm predicted results.
Adapting from Aerospace Controls to Fusion Energy Controls - Tom Weaver presented a talk he gave at the Renew Joint Theme I and II workshop meetings on 23-27 March 2009. He asserted that the reliability, maintainability, and testability (RM&T) aspects of a fusion power plant is quite similar to that of aerospace products. Boeing has a history of maturing aerospace products in both a commercial and governmental environment. Boeing has a rich environment in reliability, maintainability, and testability processes, tools, and specialists. Tom identified a host of RM&T tasks that typically are required on an aerospace program, highlighting a few that might be used on a fusion plant project.
Opportunities for Reliability Studies in ARIES - Mark Tillack examined the limited approaches to design and reliability improvements accomplished on prior ARIES design studies. These included design improvements, maintenance techniques, and specifications. Testing was considered the current modus operandi although it would be time and cost extensive. Mark discussed the theory of confidence levels for test data. Modern Reliability Engineering offers to quantify and improve reliability of new products. The 'physics of failure" proactively incorporates reliability upfront into the design process by establishing the scientific basis for evaluating new materials, structures, and technologies. Can ARIES help define the R&D needs and approaches for fusion? It is vitally needed and we should prepare ourselves to deliver better products. Mark believes ARIES has the team and the vision to help advance this approach.
Completion of (ARIES) Cost Account Documentation - Les Waganer said Farrokh commissioned him to research, analyze, recommend and document the cost database and algorithms for the ARIES systems studies. Last year in June and July, Les presented much of the direct cost accounts and all the indirect and annual cost account documentation. The ARIES team members were assigned as cost account managers, responsible for the definition and accuracy of the accounts. Ron Miller has been helping understand the early history of the ARIES cost estimates and the content of system code algorithms. Laila and Farrokh have been assisting assembling these data. There is some uncertainty and errors in the prior data and algorithms. Some accounts have changed with the evolving technologies. The intent is to establish a new set of algorithms, with supporting documentation, that are reasonably correct and consistent with prior studies and will enable parametric estimates for future studies.
Les used the leading prior fusion power plant studies including all the MFE ARIES studies. Some cost data were well documented and others are not. The cost data for each system and subsystem were examined and compared against its peers and the available costing algorithms. Then, based on the data obtained, he recommended a cost algorithm for each system or subsystem. Space in these minutes precludes mentioning each system and subsystem analyzed, but they can be examined in the meeting agenda link to the ARIES web. There were some specific recommendations that Les agreed to follow up on:
Les also recommended specific changes to the costing methodology which are a contrast to prior methodologies. He recognized that the new algorithms and methodology changes would generate new cost implications; therefore he said that he would develop a new spreadsheet program that would incorporate all the new changes. Then he would exercise the code to incrementally examine the new features and compare it to the existing ARIES-AT cost basis. This will enable the team to review and comment on the impact of the new changes. The direct costs will likely be somewhat higher than previous estimates, but the adoption of the GEN-IV discount rate (which affects the fixed charge rate) will significantly lower the COE.
US/Japan Workshop on Fusion Power Plant Studies
Fusion Power Plants and Related Advanced Technologies with participation from China - Laila El-Guebaly reported on the presentations at the US/Japan Workshop held at the University of Tokyo - Kashiwa, Japan on March 16-18, 2009. Attending and participating from the ARIES team were Laila El-Guebaly, Farrokh Najmabadi, and Rene Raffray. Japanese and Chinese colleagues also attended, but the EU did not have any participation at this meeting. The total attendance was 26 with 26 presentations plus laboratory tours. The presentations were largely aligned with MFE with two IFE presentations. Laila presented the agenda of the presentations. This agenda and presentations are available on the ARIES web site.