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.
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.
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.
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
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).