Participants: Herring, Billone, Waganer, D. Lee, Bromberg, Hofer,
Steiner, Mau, Tillack, ElGuebaly, Sviatoslavsky
- 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.
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
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 Zeff 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.
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.
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 Although this design has been superseded by the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%
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
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