ARIES Engineering Conference Call

17 November 1998

Documented by L. Waganer



Participants:
(DOE) *
(UCSD)Miller, Najmabadi, Tillack, Wang
(PPPL) Jardin, Reiersen
(GA) *
(UW) El-Guebaly, Khater, Mogahed, Sviatoslavsky
(FPA) *
(RPI) *
(ANL) *
(Boeing) Waganer
(INEEL) Petti

Administrative

The date of the next ARIES meeting is in question as several people have conflicts with the proposed date of 2-4 December and the suggested date of 7-9 December. We need a good exchange of technical information at this meeting in order to finalize the ARIES-ST design. Farrokh wants the group to start writing FED papers immediately, with a January 31, 1999, due date for the final papers. The main conflict for several key people was the NSTX Forum planned for 8-10 December. After much discussion, no suitable date was possible in December, and January was deemed too late.

Mark Tillack proposed the use of an electronic "virtual" meeting in lieu of the actual meeting, with a formal meeting to be held in January 1999. The meeting is scheduled for 4 December 1998. Les Waganer will distribute an agenda. All participants will prepare their viewgraphs in electronic form and forward them to Mark Tillack for installation on the ARIES Web Site. L. Waganer will provide a phone number for the audio portion of the call (the number is 314-232-3502). The virtual meeting will last from 8:00 PST to 12:15 PST.

Farrokh discussed writing journal papers to be included in the Fusion Engineering Design Journal. These papers would document the major elements of the ARIES ST physics and design concept. Final papers are to be submitted at the next meeting in late January 1999 in LATEX format.

Rene Raffray will be returning from the EU ITER Home Site and will be joining the UCSD group.

Systems Studies

Ron Miller noted that the "H" or later strawman would supercede the 8/25/98 strawman, which had been the ARIES-ST design basis. The low cost fabrication approaches have not been included in the current strawman. The systems code has almost all of the revised physics results and most of the new engineering designs. The PF coils have been moved closer to the physics inputs, but they are not fully consistent with the physics and engineering recommendations. Ron will try to incorporate changes to bring the code closer to the design point by the 4 December meeting.

Plasma Physics

Steve Jardin reported that the stability calculations are being finalized, and Chuck Kessel is continuing to work on the equilibrium solutions. It is difficult to get the codes to give definitive results on the required free boundary conditions. Most of the effort is directed toward defining the PF coil design to produce the higher shape harmonics that would enable the higher beta plasma. Steve hopes to have something definitive to discuss by the 4 December meeting.

Ron Miller mentioned that he has been interacting with Chuck Kessel to obtain a common geometry for the PF coil locations. The placement of the inner PF coils 1 and 2 are especially important, as they determine the location of the X-point and the nearby flux surfaces.

TK Mau discussed the plasma startup systems and modeling. He is incorporating Pete Politzer's startup approach in the baseline design.

Engineering

Laila El-Guebaly has been working with the thinner outboard first wall proposed during the last project meeting. This thin first wall has resulted in a 5% higher breeding ratio, which is now acceptable. Overall, the tritium breeding is 1.15 based on a 1-D neutronics code and confirmed with 3-D modeling. She also suggested lowering the lithium enrichment to 60%, which would reduce the lithium cost by 30% and translate into a 1.5-mill/kWh COE reduction. Laila noted that there was a lot of nuclear heating in the tungsten passive conducting shells - on the order of 35 MW each for a total of 70 MW. There was discussion that this amount of power would be difficult to radiate, but the blanket designers thought the tungsten shells would be actively cooled.

Ron asked if he could get the estimated pumping power for the outboard and inboard (first walls?). (Who?) told him it would be on the order of 40 MWe inboard and 40 MWe outboard. Mark Tillack has increased the divertor pumping requirement. Global powers will be sent (by Jardin?) to Laila.

Mark Tillack noted that the power core configuration is still based on the 8/25/86 strawman. A new configuration is in work. Xueren has been working to layout the neutral beam ports as defined by TK Mau.

Dave Petti reported that a white paper on fusion reactor safety issues would be distributed to the team shortly for review. It stresses research and development needs for both MCF and ICF reactor designs. He discussed the radioactive waste issue relating to lower level wastes to be stored or recycled. Recycling the waste remains an economic issue.

Hesham Khater mentioned that Ahmed Hassanein has examined the ARIES-ST disruption assumptions based upon ITER groundrules. No calculations have been done; rather he has estimated the results based upon his experience with ITER conditions. He estimated that, with a 2.1 GJ thermal quench energy, 10% of the tungsten melt layer would form dust particles. Hassanein was concerned that the V-shaped divertor region would result in a vapor cloud forming in the divertor region, and the energy from photons would be concentrated on the divertor surfaces. He suggested a more open configuration. Hesham suggested a barrier leak rate of 1% per barrier. Given that rate, the radioactive doses at the site boundary would be acceptably low.

Mark Tillack noted that Dai-Kai Sze has not reported any power conversion system efficiency results. We had been using a value of 40% or more, but at the last meeting Dai-Kai suggested the overall thermal conversion efficiency should be reduced below 40%.

Wayne Reiersen reported minimal progress on the magnet systems. There have been a lot of ideas exchanged for the centerpost cooling system. Les Waganer offered several centerpost cooling system options to Wayne and Dai-Kai. Elsayed Mogahed mentioned that he is working on a heat pipe coolant option to control the LOCA condition of the centerpost. It was confirmed that there should be 15% water in both the copper centerpost and the aluminum outer TF shell. The thickness of the outer TF shell at the midplane is 50 cm with borated water coolant. Laila suggested a 70-cm-thick shell, which would only need regular water coolant. The tradeoffs between the thinner and thicker shell are an increased shell capital cost and lower recirculating power in the shell.

Les Waganer has been working on the improved estimate for the laser (or plasma arc) formed centerpost and the spray cast aluminum TF shell. These estimates must be provided to Ron Miller so he can incorporate the costing algorithms in the systems code.

Mark Tillack told the group that he had been refining the porous metal heat exchanger approach for the divertor surfaces. He has increased the pumping power to 5%. The tubes will be constructed of tungsten with Ultramet tungsten foam inside the tubes to enhance the overall heat transfer coefficient. He is trying to develop a design that will accommodate the tungsten ductile-to-brittle transition. He noted Japan's report of tungsten alloys that improve fracture toughness by nano-dispersioned grains. Fabrication of the tubes and attachment to the structure and manifolds remain problem areas. He is assuming a surface heat load of 1 MW/m2. He would like to have a self-consistent power flow diagram (action: Jardin).