Date: 26 Sept 1994
Subject: Minutes of the 14-15 Sept 1994 Starlite Project Meeting
To: ARIES Project Members
CC: Visitors (see below)
From: F. Najmabadi, L. Waganer [Special thanks to many contributors to these minutes.}
Attendees: C. Bathke, M. Billone, L. Bromberg, S. Dean, B. Dove, L. E-Guebaly, D. Ehst, T. Flynn, B.J. Lee, S. Herring, G. Hofer, S. Jardin, C. Kessel, T.K. Mau, R. Miller, F. Najmabadi, D. Steiner, D-K Sze, L. Waganer, C. Wong
Visitors: R. Blanken, C. Bolton, D. Crandall, J. DeLooper, B. Ellis, N. Fisch, R. Goldston, R. Hawryluk, S. Kaye, D. Mikkelsen, H. Mynick, H. Neilson, B. Nevins, P. Politzer, W. Reiersen, S. Rossi, J. Schivell
Background - This Starlite (note the initial capitalization) meeting was hosted by Steve Jardin at PPPL to afford a technical interchange of physics, safety, and engineering knowledge and ideas between PPPL personnel and the project team. The first day, 14 Sept, was devoted to the exchange of physics data and ideas. At the morning session, new innovative physics ideas were presented with possible applicability to a future fusion power plant. In the afternoon session, each of the major tokamak experiments reported their status and plans. The status and results of the project tasks were reported the next day and the morning of the 16th. The afternoon of the 16th was set aside to formulate a coordinated plan for the Licensing and Safety group.
F. Najmabadi noted that as a part of the Starlite project we have begun to conduct a one-day meeting or seminar before each project meeting to brief and obtain feedback from different parts of the fusion community on the Starlite progress. F. Najmabadi started the meeting with a brief summary ofthe Starlite project and an overview of the Demo mission. The Demo must have the same systems and components as will be employed in the first commercial fusion power plant.
Dave Ehst initiated the physics discussion with a review of the physics figure-of-merit to be applied to the Demo. He described the Advanced Tokamak Power Plant Study that will be used to screen and evaluate the physics options for Demo.
Dave Mikkelsen assessed the prospects for off-axis fueling in reactors. He concluded that, while 100 keV beams could penetrate to the region of interest, the inherent recirculated power would be unacceptably high. Pellet injection may be suitable and deserves further study.
Harry Mynick described a frequency-sweeping technique for removing helium ash in reactors. His method is described in Mynick, et al. Phys.Fluids-B 5(1993) p 2460. The details need to be completed of how to create suitable structure perturbations in a real tokamak.
John Schivell described detached plasma modes in TFTR and TEXTOR. The idea is to inject a controlled amount of an impurity (both neon and silicon look promising, but silicon builds up on walls) to the plasma edge where it will radiate up to 90% of the fusion energy. Some aspects of this idea may be adopted for ITER, with the fractions of radiation coming from the main plasma, divertor chamber, and x-point region (i.e., a Marfe) still being determined. Possible problems with a radiating mantle plasma include the effect on the ICRF coupling and the fuel dilution requirement that neon be kept below 1% in the center of the plasma. The concern on silicon build upon walls was not clear.
Nat Fisch described his concept of alpha-channeling. The idea is to excite an RF wave to serve as a medium to absorb the energy generated from the alpha particles and give it to a population of high energy ions. This will increase the effective fusion reactivity and allow the electrons to be at a lower temperature than the ions, since their only heat source would be electron-ion coupling. The maximum benefit of the alpha-channeling would be realized if the electrons had a much poorer energy confinement time than the ions (a factor of 6 worse was used in the example). Preliminary planning of TFTR experiments using IBW to test aspects of this concept are in work.
Peter Politzer (DIII-D) discussed progress in increasing H (normalized energy confinement time) and beta-n (normalized energy density) simultaneously. They also try to maximize the product beta*tau and have achieved a maximum of 1800%-ms at q=4. He also discussed the wall stabilization experiments, which seemed to require plasma rotation frequencies of 5-10 kHz, and the plans for modifying the divertor inDIII-D. He also mentioned helium injection experiments to measure Tau*-He /TauE.
Rich Hawryluk discussed TFTR achievements in obtaining high values of fusion power density in the center and in generating 9 MW of DT power. Recorded parameters include H, beta-N*, (n_i)(tau_E*)(T_i(0)),n_alpha(0)/ne(0) = 0.3%, P_alpha / Ploss =.04, (R)(grad[beta_alpha])=.02. They also have some evidence of increased confinement due to reversed shear. They have measured Tau*_He/TauE = 5. The TAE mode stability continues to be studied.
Rob Goldston's talk covered the measures of advanced tokamak performance. He found that the n*T*tau measure can be expressed as beta*tau/a**2 and represents the machine's requirement for high Q. Using the expression for beta and an approximate scaling for toroidal field, he found that the requirement for high power density can be represented by beta**2/epsilon**2(where epsilon is inverse aspect ratio). From experimental data on JET, JT-60, PBX-M, D-IIID and designs like TPX and ITER, that these axes make it clear that plasma shaping and only relatively high edge q (about 4) are critical to maximizing these figures of merit. He also indicated that a bootstrap figure of merit is also necessary that penalizes under and overdrive. He qualified these figures of merit by saying that they do not include the "costs" of high plasma current (disruption), high elongation (vertical stability), and high triangularity (inboard divertor/shielding). In addition, he said that the betas could be replaced by beta-star to bemore reactor relevant.
Stan Kaye (PBX-M) discussed an experimental program that emphasized LHCD, IBW, and wall stabilization. Slides depicting the wall stabilization experiments showed toroidal velocities of up to 3 x 10**5 m/sec. They find that, with high triangularity, they can get both high H and high beta_N simultaneously. Other parameter spaces they find useful are beta*tau/a**2 vs (beta/epsilon)**2 (this was suggested by Goldston) and beta/epsilon vs. epsilon*beta poloidal.
Hutch Neilson described the experimental program of TPX, emphasizing noninductive current drive, divertors, and disruption control. Their figures of merit include f_BS,H,and beta_N, all achieved simultaneously.
Bill Nevins described the advanced tokamak program planned for ITER, as described in the TAC-4 report. It emphasized the reversed shear mode.
D. Crandall of OFE stressed the importance of the Starlite project to DOE. This project to define the US Demo will help shape the future direction and emphasis of the US fusion program. This project will have high visibility and will cut across many existing fusion programs. It will be difficult to get started but we need to establish a credible mission and set of goals for an attractive power plant.
B. Dove expressed his vision of an outreach program to the fusion research community to gain support and consensus for our evolving Demo. He emphasized that the mission and goals are the initial steps, followed by a design definition stage, and then the conduct of a developmental pathway analysis.
F. Najmabadi reviewed his preliminary U.S. Demo Mission and Goals document. The team provided feedback with recommended changes. The document will be revised and reissued to the team by 23 Sept. A list of assumptions should be documented as a part of the mission and goals development, such as market penetration, funding sources, regulatory environment, and anticipated public acceptance. The next step is to develop more detailed goals and requirements for the Demo. The primary end product will be electrical energy but the energy products of synthetic fuel, process heat,and hydrogen may be considered.
S. Dean of Fusion Power Associates described several possible alternative developmental paths for a tokamak Demo and reviewed mission statements from a number of previous studies. He expressed concern that the present DOE reference strategy was too expensive. He suggested combining the DOE's "Blanket Test Facility" with a mini-Demo Plant and combining ITER and Demo as one facility. He advised the team to build upon previous Demo study missions. He offered a Demo mission statement, based on previous studies. He felt that some reference to capital cost of the Demo was important and we should include a list of "market assumptions" on which our Demo parameters were based. He also noted that the Argonne-led TPA study had a detailed list of power plant Demo objectives in which both economics andsafety/environment/licensing were essential elements with quantitative goals for each objective.
As a historical perspective, L. Waganer reviewed the developmental pathways followed by the Canadian CANDU power plants. The chief observation was that a single design approach was selected early in the design process. Following this decision, a rapid development plan was affected from a Demo reactor to multiple commercial power plant facilities. Designs of succeeding generations were initiated prior to completion of the previous design.
Ron Blanken of ER-OFE compared high aspect ratio devices (ARIES and TPX) to low aspect ratio systems. The latter class of devices feature much higher loads and higher poloidal field coil currents. He suggested the StarliteTeam consider evaluating a low aspect ratio tokamak for the Demo. Wong questioned whether the normal TF coil resistivity used for the power balance calculation included the effect from radiation damage.
W. Reiersen of PPPL presented a perspective of the Demo for the Starlite team. The PPPL engineering experience in designing and building TFTR and designing TPX would lend credibility to the Demo design approach. To that end, Wayne offered the services of the PPPL Engineering staff to support the Demo team. He stressed that the Demo must become much more attractive to be a viable energy source.
R. Miller reviewed his status on the economic figure of merit used to judge the competitiveness of the forthcoming Demo design to the contemporary energy sources. C. Bathke presented his "preliminary" analysis results to stimulate the needed data to adequately evaluate the potential of advanced physics options. Supportive to this, certain actions were agreed upon. T.K. Mau is to provide immediate current-drive analysis for the reversed-shear mode, and Ehst and Kessel are to work on adding alpha-pressure effects to bootstrap current.
Tom Flynn discussed his RAMI approach for the Demo. He will be using the INFO and NERC databases for relevant reliability data. He intends to use the generated WBS listing to tailor the reliability and maintainability model to the Starlite design approach.
L. El-Gubaly reviewed neutronic and engineering issues relating to the blanket, shield, and vacuum vessel. Advantages and disadvantages of candidate materials were reviewed. Parametric effects of wall loading onthe waste volume were given. Recycling of fusion waste should seriously be considered in all designs to reduce the volume of fusion waste. Design of the vacuum vessel should be included in the early design assessment. It was recommended to divide the shield into high temperature and low temperature regions to minimize the shield capital cost .
D-K Sze presented the results of the allowable neutron wall loading for the ARIES-IV-type blanket. The limiting heat transfer term in the blanket with a Be zone is the conduction within the Li20. Any improvement in the Li2O conduction has a major impact on the blanket design. As the neutron wall load exceeds 5-6 MW/m2, the breeding zone thickness becomes small, the design is complex, and the structural fraction increases (higher costs). Additionally, beryllium may have to be added which will increase the heating rate and thus may further thin the breeding zone. The calculated breeding ratio for a Li2O blanket is marginal based on the available neutron cross-section data. However, the breeding ratio will not be sufficient if we add on the uncertainties due to the data, the geometry, and the calculation procedure. The heating rate in the breeding material will be much reduced if Be is not required, which reduces the problem associated with conduction. Thus, it is important to assess the whether Be will be required for Li2O. D-K Sze will lead the Engineering Team to investigate this problem.
C. Wong highlighted the use of the WBS listing he developed for the Starlite project. There was much discussion as to the value of the WBS, but the consensus was that the WBS was useful to determine the extent of the plant systems and as a tool to track the characteristics and needs of the various systems. He requested comments from the team before a WBS format is selected for the project.
L. Waganer reviewed the project Action Item List and recorded the completed and revised actions. The revised action item list will be faxed to the active team members (format incompatible for transmission).
[Due to communication errors, the magnet design and maintenance presentation was not given.]
D. Steiner summarized the coupling of the OFE and the Demo tasks on the safety and licensing activities relating to the future fusion facilities following TPX. All the regulations are to be met to adequately safeguard the public, the workers, and the environment while not unduly restricting the development of commercial fusion.
B. Dove reviewed the status of the OFE Strategy Paper on Licensing of fusion facilities which will likely be done by NRC. The paper will recommend a streamlined licensing process that was strongly urged by the Starlite Utility Advisory Committee (UAC). All the basic safety requirements must be met but the process would not prescribe the methods of how to meet those requirements. DOE is assuming there will be latitude in design approaches. NRC would be approached at the commissioner level to obtain agreement in principle to this approach. Whether ITER would be suitable for this approach is yet to be determined.
John DeLooper of PPPL described the evolving Fusion Safety Standard being developed and funded through INEL with support from many organizations. The standard is being developed with three parts: (1) safety REQUIREMENTS that are traceable directly to the applicable CFRs, (2) GUIDANCE to designers and operators on how to meet the requirements, and (3) RECOMMENDATIONS from prior experiences. This committee is incorporating many of the UAC's recommendations. ITER will again be the first user of this standard. The standard is anticipated to be issued in March 1996. If ITER is to be built in the U.S. and is to be licensed by DOE, DeLooper would like DOE to follow more of the NRC approach.
S. Herring outlined the purpose and progress toward developing the Fusion Safety Design Criteria for accident conditions and routine operation. In addition to radiation and hazardous material considerations, effects of magnetic fields are being assessed and included.
G. Hofer reviewed the history of the NRC and the regulations which may apply to fusion. Definition of source materials and special nuclear materials were presented and the applicability to fusion materials were discussed. A draft bill (H.R. 3920) in undergoing hearings. This bill will require all new DOE nuclear facilities to be licensed by NRC. Examples of laws, federal regulations, and regulatory guides that may be applicable were presented. Outlines of the environmental review and the licensing review processes were shown and discussed.
C. Wong summarized the clean sheet approach safety tasks suggested by F. Silady.
L. Waganer conducted the final meeting wrap-up with some guidance to areas of concentration over the next few months. The physics group should catalog the current and planned physics database for tokamaks and to postulate credible physics operating regimes for Demo. They should coordinate with C. Bathke for incorporation into the ARIES System Code. The Engineering Group should continue to investigate high leverage issues. L. Waganer will concentrate on improving machine constructability and maintainabilty. L. Sas and T. Flynn should concentrate on quantifying high impact RAMI issues that will provide guidance to the Engineering Group and help achieve the desired higher availability. All team leaders are to provide input to C. Wong on identification of perceived Critical Items. M. Billone and J. Davis are to formulate a plan of action to provide fusion materials expertise to the project and to communicate material needs to the community. Steiner should continue to coordinate the safety and licensing activities with the goal of achieving timely licensing of a safe plant.
The next conference call will be 28 Sept at the usual time and phone number (agenda to follow).
Lester M. Waganer, McDonnell Douglas Aerospace
Mail Stop 3064204, PO Box 516, St. Louis, MO 63166