Participants: Sze, Wong, Bathke, Waganer, D. Lee, Bromberg, Jardin, Steiner, Miller, Malang, Mau, Tillack, El-Guebaly, Sviatoslavsky
Summary of US/Japan Workshop of 13-15 March
Ron Miller said UCSD will prepare a copy of the workshop handouts for all attendees plus a set for each Starlite organization. There were several updates of the status of the DREAM reactor and its systems. There was some interest in costing of reactor components.
Safety and Licensing Summary
D. Steiner noted that Bob Thayer is continuing to work on the safety assessment. Bob still needs inputs from the team for his preliminary safety analyses framework. He hopes to have results for presentation at the next project meeting. Clement Wong is trying to get inputs from Siliday into the assessment process. Mark Tillack reported that Culham is interested in investigating a lithium/vanadium design. If the work is approved from Brussels, then we should plan to supply them with any information needed to describe our designs.
S. Jardin stated that most of the reverse shear physics work has been completed. But TK. Mau said he and Dave Ehst are still working on analyses of the self-consistent equilibrium cases, trying to narrow down (isolate) the factors that contributed to differing results. Hopefully, these results will be available for presentation at the meeting. TK is working on the design of the current drive system. BJ. Lee is working on a fake rotating shell to help the plasma stabilization.
C. Wong discussed the divertor physics issues. Tom Petrie and Phil West of GA are continuing to work on a radiative divertor approach to dissipate the heat over the first wall surface and lower the local heating in the divertor. They are trying to evolve the pressure at the inside of the plasma profiles and determine the thickness of the radiating mantle. BJ. Lee is also working with the group to determine the thermal stability of the mantle layer. The amount of power radiated from the mantle is in the range of 200-300 MW. Clement is working on a short memo to document the assumptions used and the tentative findings. The Zeff is estimated to be in the range of 1.7 to 2.2.
Systems Analyses Summary
C. Bathke completed the system code run and posted the new 3/26/96 reverse shear strawman on his WWW home page. Several changes have been incorporated:
Dennis Lee noted that he does not have sufficient time to incorporate the new code data in his configuration model, but the values are not too different. C. Wong noted that his divertor design has not progressed to the point of being able to include a model in the systems code.
Status of Engineering Design
Laila El-Guebaly reported that she has been working with the generated wall loading distribution to determine the adequacy of the shielding behind the divertor slots. The values she is using seem to be adequate (HT Shield is 70 cm and LT shield is 23 cm), but the values in the system code are lower (HT Shield is 60 cm and LT shield is 3 cm) and probably are inadequate. The activation of 2-mm tungsten on the divertor surface is being evaluated and data may be presented at the meeting.
L. Bromberg said he was in the process of defining the magnets and structures. The new strawman has resulted in the currents in the coils being very large (40 MA in PF5), hence the coils have become very difficult to design within the imposed constraints. He may have to change PF coils from NbTi to NbSn. He thinks he has a solution to modify the aspect ratio of the outer TF coil legs to ease the clearance, but cost will increase. He will also investigate the possibility of deviating from the classical "D-shaped" TF coils to decrease the currents and size of the upper and outer PF coils, but this results in higher coil stresses. These data will be provided for the meeting.
Dennis Lee noted that he has been working on the development of the design concepts for the power core components. These include his plus those of S. Malang and I. Sviatoslavsky. The general plasma and FWBS are similar to that of the 1/26/96 strawman, but the TF coils have been moved out to accommodate the new configuration. The new data from the system code strawman are different from that assumed by D. Lee, but not radically so. Before the meeting, Dennis will summarize the differences. Hopefully, X. Wang will be able to map the new geometry onto a 2-D cross-sectional view that will aid in the comparison. Dennis will present at the meeting the desired features, the constraints imposed by the geometry, and hopefully, some solutions. Then we have to decide which way the project wants to proceed and if we can accommodate the systems code geometry or if we have to make some adjustments. Laila is worried about the radiation resistance of the organic materials in the thermal insulators - L. Bromberg offered to define the materials to be used and the radiation limits.
TK. Mau has been working on the RF heating system design. His design was informally reviewed by UCSD. The design uses a folded waveguide array of approximately 2 m by 2 m and occupies all of one sector just above midplane. The waveguide must be concentrated in one sector and cannot be distributed around the torus. The depth of the waveguide was quite deep, but based upon feedback at the UCSD meeting, TK reduced the depth to approximately 80 cm. This depth of waveguide will require some additional shielding locally around the back of this section. The waveguides will be constructed of vanadium and coated with a thin layer (20 microns) of copper for a high conductivity surface. The coax tubes should be bent to minimize neutron streaming.
D-K Sze mentioned Mike Billone's issuing the vanadium design properties note for review. The design lifetime is dependent upon the primary stress level. D-K is modifying the blanket design to minimize the primary stress to lengthen the in-core lifetime of the blanket. Jake Blanchard is refining the stress analysis to support Sze's design. M. Khater is working on the afterheat calculations. T. Hua is analyzing the lithium thermal hydraulics. D-K also mentioned the vacuum pumping design approach and was asking the species of injected gasses so he could properly design the pumping system. Argon seemed to be acceptable and maybe neon.