TO: Starlite Study Team DRAFT DATE:1 June 1995 FROM: L. Waganer
SUBJECT: Starlite Conference Call Minutes, Wed 31 May 1995
PARTICIPANTS (by organization): Billone, Ehst, Wong, Sager, Schleicher, Herring, Bathke, Waganer, Bromberg, Jardin, Kessel, Hofer, Flynn, Steiner, Miller, Najmabadi, El-Guebaly, Dove
The minutes for the 5 April Conference Call have been distributed. The next project meeting is to be held at UCSD on 2-4 August in conjunction with the Utility Advisory Committee meeting on July 31-Aug 1. Najmabadi is to investigate the possibility of commencing the Starlite project meeting to immediately follow the UAC meeting on the afternoon of Aug 1. The Starlite meeting is to conclude on Aug 4 at 11:00 for the convenience of the east bound travelers. The next conference call will be on Monday June 12 @ 11:30 CDT (for the convenience of L. Waganer who is moving into his new house on the 14th. Thanks for the change!) Farrokh, now it is your turn to move!
L. Waganer and F. Najmabadi summarized the purpose and objective of the phone call. In the last project meeting, the group adopted a tentative set of design approaches and plasma operating regime. The group agreed to reconvene on this phone call to reassess and validate the decision, hopefully reaching a consensus opinion on the approach for Demo-I to be pursued for the next year. F. Najmabadi stated two bounding criteria; (1) a self-consistent (and complete) design must be concluded by July 1996 and (2) it must be accepted as the reference US Demo design. Thus we must make timely decisions and be careful of our choices we make. To expedite the process we should make as much of the definition of Demo-I today as possible. Any remaining problem areas must be decided before the Aug meeting. Between now and then, we have to conclude (and document) any outstanding assessments (ferritic steel, vanadium, coolant, magnet approach, etc.).
There was a question that the espoused decision-making process was abandoned, but Farrokh noted that we are just trying to speed up the decisions where possible, but still retain the process and supporting documentation (concluded during the next two months).
Should we adopt the Reverse Shear plasma mode? Steve Jardin expressed the opinion that adopting RS is still somewhat a leap of faith as there is minimal supporting experimental evidence for RS. TPX is planning to use RS but also it also uses a ARIES-I mode (and it is an experimental device). Steve would feel more comfortable with the ARIES-I mode, but realized the potential benefits at an increased risk. Bathke emphasized that the economics would clearly favor the RS mode.
There was much discussion amongst the entire group about the degree of technical risk with adopting a RS plasma operating mode versus the economic benefits vs. the political benefits/risks. In general, the group felt it was better to adopt the more “attractive” RS plasma mode for Demo-I assuming that it would be validated by TPX or some other experimental machine. To provide a fall-back position, a minimum level of effort system-code assessment of an ARIES-I type of plasma embodiment would be carried along to scope the consequences of the more conservative plasma assumptions.
Vanadium as the structural material for Demo-I? The group still supported the logic of favoring vanadium over ferritic steel and silicon carbide composite. The ferritic steel is still generally viewed as not having a high enough temperature to provide sufficient thermal efficiency for the Demo application. The DBTT problem still is unresolved. The database for SiC is not sufficiently well developed to recommend using SiC as the baseline structural material. Vanadium has some relevant material property data, but more is needed for a detailed design, especially in coatings for MHD and impurity protection. Nevertheless, vanadium was picked as the most attractive structural material.
Coolant for use with vanadium? The coolant tentatively chosen at the meeting was the self-cooled lithium for use with vanadium. C. Wong supported the minority opinion that a helium-cooled design with near-stagnant lithium for a breeder and thermal transfer agent would be a better design. The main advantages are potentially a higher coolant temperature (and higher efficiency), safer by virtue of less flowing lithium, and a better documented technical design basis. The disadvantages are that the coating for impurity control needs to be more complete as compared to a less complete coating for MHD purposes with flowing lithium. The ability to maintain and utilize a reducing (coolant) atmosphere has not been adequately documented to the project’s satisfaction. The high pressure helium (18 MPa) must be accommodated with design features to assure leak before burst philosophy and passive, fast-acting valves may be required. Other disadvantages of the helium-cooled design include the difficulty of detecting He leaks, larger machine size, more complex blanket modules and likely higher capital cost. [This may not be a complete list of advantages and disadvantages, but that is to be developed and validated.]
The coolant decision could not be made at this time. Instead, the Engineering Group is to evaluate the pros and cons of these two coolants over the next two months. In a month, they will meet and exchange viewpoints. C. Wong will be the advocate for the helium-cooled design and D. K. Sze will represent the lithium-self cooled design (if he accepts). S. Herring will quantitatively assess the relative safety risks of both design approaches. T. Flynn and G. Hofer will provide A&E expertise (advice) on both designs. Bob Schleicher will assess if there is any significant thermal conversion efficiency differences between the two approaches, both near term and long term. By Aug 1(see July 15 date below), the Engineering Group will reach a consensus decision to support a single coolant /structural material design for Demo-I.
The divertor and the shield designs are thought to be adaptable to either a self-cooled lithium or a helium-cooled approach, compatible with the coolant for the blanket. The design approach for the magnets are in work by L. Bromberg along with advice from T. Flynn.
C. Bathke agreed to provide a RS strawman for the August meeting. But to do so, he needs inputs (models, algorithms, data, etc. ) by July 15 to meet this deadline. If you remember, this was the problem with PULSAR not meeting the deadlines. So do not shirk this deadline!
The Low Aspect Ratio assessment will continue as time permits without interfering with the reverse-shear analysis and assessment.