ARIES Project Conference Call

9 February 1998

Documented by L. Waganer



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

Administrative

The possible dates for the next ARIES project meeting were discussed. It was decided to hold the next meeting in San Diego on Wednesday, 29 April, starting at 1:00 pm and continuing through 11:00 am on Friday, 1 May 1998.

The date for the next project conference call will be 2 March (Monday). The phone number will be 314-232-3502.

Ron Stambaugh and Steve Jardin are considering attending the Culham meeting in March. Other participants will be F. Najmabadi, M. Tillack, R. Miller, D-K Sze, L. Waganer, and TK Mau.

Mark Tillack reported that the FED papers associated with ARIES have been printed, and a limited number of copies have been distributed. Mark is trying to bundle the papers together for an ARIES mailing; but he needs any extra copies the principal authors might receive.

Plasma Physics

Plasma Stability - Steve Jardin reported that the baseline configurations, A=1.6, now seem to be vertically stable. The previously reported unstable conditions were due to an error in the code being used by PPPL. The passive walls were assumed to be 5-cm-thick tungsten and located at 0.5 times the plasma minor radius (a) from the plasma boundary. This suggests that the conducting walls are roughly 1.0 m from the first wall. Laila El-Guebaly encouraged Steve to evaluate a similar set of walls placed behind the blanket/manifolds approximately at 1.4 m from the first wall. The conducting wall system consists of two walls, approximately 1.6 times the minor radius poloidally high, separated by some vertical distance, and centered on the midplane. Steve will distribute a sketch documenting the geometry. Cases exhibit ideal stability on a reasonable time scale, but investigation of control requirements are just starting. Ron Stambaugh said that the results from the GA calculations supported a high sensitivity to triangularity for kink stability. Thus, a high triangularity of 0.6 is favored, while a triangularity as low as 0.5 would be marginal. Farrokh Najmabadi thought that 0.45 would represent too much of a technical risk and 0.5 would be a better choice.

Ron Stambaugh reported some spreadsheet analysis results that pointed to plasma geometry and operating regimes that might offer potential benefit to increase the overall plant Q.

Heating and Current Drive - TK Mau reported that he and Mark Tillack had conferred on the geometry and sizes of the lower frequency, fast wave (LFFW) systems being considered. The antenna array is located in a recessed box located toroidially around the plasma chamber. The box is recessed approximately 25 cm from the first wall surface. There is some question if a Faraday shield is required given that the antenna is recessed and may be constructed of the same material as other plasma facing components.

Neutral beams (NB) with an energy level of approximately 3 MeV have a nominal power density of 200-300 MW/m2, which would suggest only a few small penetrations would be required for the 40 MW power level required. The problem is that once the geometry of beams is established, the beams will only drive currents in one direction.

TK noted that although the LFFW may be good for on-axis CD, it may not be appropriate for initial heating and current drive during startup. High Harmonic Fast Wave (HHFW) may be required for startup, heating and off-axis current drive. One advantage of HHFW is its small antenna size.

Engineering

Blanket - Mark Tillack reported that D-K Sze had completed some additional thermal-hydraulic analyses. These analyses indicated improved power handling capabilities for the first wall, perhaps up to 0.9 MW/m2 peak. But not up to 1.0 MW/m2, since this would require a first wall that is too thin to serve as a high-pressure containing wall - id est, insufficient bending stiffness. The Engineering Group needs to seriously examine the power handling capability of the inboard first wall and shield.

Neutronic Analyses - Laila El-Guebaly noted that she had completed a 3-D neutron wall loading (NWL) analysis for the ARIES-ST with a straight centerpost case. The analysis indicated that the average NWL in the inboard divertor region (above the upper X-point or below the lower X-point) is a factor of 10 lower than the average NWL between the upper and lower X-points on the inboard first wall and shield. This means that the current inboard shield thickness of 20 cm could be thinned to approximately 10 cm in the divertor region if necessary. Wayne Reiersen suggested that the added area might be required for helium flow improvement. This area probably could not be used for flaring the centerpost because of maintenance and assembly complications.

Laila said she would distribute the radial build data on 13 February.

Maintenance and Configuration - Xueren Wang said that he has been working on the building configuration and the subsystem layout. Eight large power supplies are located immediately outside the biological shield near the power core midplane. The cryopumps are also located near the shield but on a different floor. These components were sized from the GA pilot plant drawings.

Xueren has also been evaluating the capability to support the gravity loads of the power core during operation. He has been assessing the ability of removable structure to support the entire weight of the core (~10,000 tonnes).

LOCA Analyses - Mark Tillack reported that E. Mogahed and Dai-Kai Sze have agreed on the time-dependent transport of LOCA heat along the long centerpost. E. Mogahed explained that the peak temperature remains similar to a short time analysis, but the time to reach the coil leads temperature is more than five days.

Magnet Design and Analysis - Wayne Reiersen affirmed the need for the clearance between the centerpost and the inboard shield. The area would also contain the components necessary for thermal conduction during LOCA.

Systems Studies

Ron Miller said that he is working on the list of changes requested by W. Reiersen. By the end of this week, Ron thought he would be able to input the radial build (from Laila?). He also has been working with Ron Stambaugh on benchmarking the code against the GA physics. He hoped to have a strawman data set soon.

Alternate Applications Studies

Les Waganer reported that he is in the process of reviewing prior fusion hydrogen and synfuel production concepts and reports to help establish a database of information in case the project decides to assess hydrogen production by fusion.