Participants: Herring, Billone, Waganer, D. Lee, Bromberg, Hofer, Steiner, Mau, Tillack, El­Guebaly, Sviatoslavsky

Administrative

• The following items have been reviewed, distributed, and posted on the Starlite Home Page:

  - The Fifth Quarterly Report .

  - Minutes of the Physics Group conference call of 1 April.

  - Minutes of the Starlite project meeting of 3-5 April along with the related Action Item List.

  - Minutes of the Engineering Group conference call of 17 April.

• The next Engineering conference call will be 8 May, and the next project conference call will be 22 May.

• The group discussed the name to be applied to the conceptual design. The options discussed were: ARIES-V, ARIES-RS, ARIES-V(RS), and Starlite. There were more favorable votes for the Starlite name so it was tentatively adopted. However, Bill Dove later relayed several strong reasons why the name ARIES-RS should be adopted. Therefore, we will use ARIES­RS as the name of the conceptual design for the commercial power plant.

• TK Mau reported that Dave Ehst has been working on the ARIES-RS Physics Data Book. The conference call participants suggested incorporating that data within the project Design Data Book. TK said he would add this topic to the upcoming Physics conference call, Wed, 1 May.

Physics

TK Mau mentioned that only a general outline of the startup scenario has been postulated. He relayed that Dave Ehst thinks that a low density, high temperature path is the more promising route. C. Kessel will begin to address this (with input from TK Mau and Dave Ehst) using the 1-D transport TSC code after his return from Japan.

TK noted that the details of the RF system are posted on the Home Page. He looked at a tungsten coating, but he needs irradiated conductivity data, which M. Billone agreed to supply.

TK will finish up the Z_eff scaling of CD efficiency by COB 21 April and forward the data to C. Bathke for inclusion in the ASC code. TK said he would suggest that the Physics Group address and affirm the scrape-off radiation power balance.

System Studies

M. Tillack informed the group that C. Bathke still did not have the definition of the TF coil shape. L. Bromberg said he would forward the information immediately to C. Bathke. With that input, Chuck can complete the strawman by 26 April. TK will confirm the radiative mantle physics assumptions by 25 April.

Engineering

Magnets - L. Bromberg reiterated that a reduction in the height of the TF coils by 1 m was acceptable. The stress is still less than 200 MPa. He will continue to investigate further height reductions. There was some question as to the technical feasibility of using layered, edge welded TF coils, especially the use of structural welds in high stress areas and significant length of welds. Leslie noted that this approach was endorsed by ITER in the Rebut era. Although this design has been superseded by the present ITER design, these concerns were not the reason for changing the design approach in ITER. Leslie noted that the Russians had affirmed that this prior approach is technically feasible. Leslie further stated that, if we went to the more conventional style of coil construction, the radial thickness would increase from 0.8 m to 1.3 m. With the radial pancake design, the strands are wedged into grooves that are closed with welded individual cover plates over strands; hence the weld lengths are also quite long, although these are not structural welds. The main reason for the change from this design to the more conventional is the stress in the keys associated with a pulsed, ohmically-driven machine. Leslie also affirmed that the systems code has the correct formulation for the coil pack (70% structure, 20% conductor/copper, and 10% coolant/void).

Divertor - C. Wong was not available to discuss the divertor design, but M. Tillack reported that X. Wang has been working on a thermo-hydraulic analysis of the divertor plate. This analysis is mainly on a cross-section transverse to the plate. The surface heating is up to 5 MW/m² over a short length (~1 cm) and falling off to a fraction of that (1 MW/m²) nearby. Igor is continuing to work on defining the internal structure.

Blanket and Shield - E. Mogahed and H. Khater re continuing to investigate the LOCA on the inboard blanket shield. The temperature of the inboard region area is still unacceptably high. Laila is replacing the bulk stainless steel with bulk vanadium shielding material. This will increase the radial build by 3-5 cm. The next step is to integrate the analysis of the inboard and the outboard regions.

Siegfried and Laila have segmented the blankets and shield according to the power and dpa levels to better apportion power and component lifetimes. They are drafting a memo to DK Sze, M. Billone, and T. Hua regarding this new division of elements. Laila noted that the change from 30 FPY to 40 FPY increased the shield thickness by 3 cm and increased the radial build accordingly. J. Blanchard is continuing to direct the disruption analysis - results are expected in 2-3 weeks.

Maintenance - The prior week L. Waganer contacted S. Herring to comment on the advisability of open replacement of modules as opposed to keeping modules within closed containers or limited access corridors. Steve joined the call to explain it is usually better to eliminate the spread of airborne contaminated waste. Greg Hofer noted that special paints would help collection of such surface contamination, but it is better to contain it in a small volume rather than gather it up after dispersal. Steve noted that some airborne contaminants never settle.

Materials - [Additional material has been added.] M. Billone is looking into the issue of hydrogen isotope limits in vanadium. The limits are based on hydrogen embrittlement and tritium inventory. He is contacting the materials experts to get their consensus input on the hydrogen limit on the V­4Cr-4Ti material, based on low-temperature embrittlement (e.g., cool-down to room temperature for maintenance, repair, replacement, etc.). He is also contacting experts within the plasma-facing components field to obtain an estimate of the implantation rate from the ARIES-RS plasma to the first wall. These data, along with the transmutation rate already provided by Laila, determine the source term for the problem. Finally, Mike is reviewing the data on solubility, diffusion, desorption, and adsorption of hydrogen isotopes in vanadium. Such information will allow simple, one-dimensional, upper-bound calculations, as well as more detailed calculations, for determining the hydrogen isotope concentration in the ARIES-RS V-4Cr-4Ti first wall.