ARIES Project Conference Call

Administrative

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

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.

• There is a strong experimental basis for t_He* / t_E as low as 4 from JT-60U and ASDEX Upgrade. This lower value gives a 5% helium concentration in ARIES-ST instead of the present 15% in the strawman. This lower helium concentration would raise the fusion power output by about 30-50%. These results are obtained in ELMing H-mode or in L-mode. The assumptions made in constructing ARIES-ST equilibria essentially correspond to an L-mode edge, and so these low values of t_He* / t_E are consistent. Farrokh was concerned that the tritium inventory and the burnup fraction might be unacceptable with these conditions. It would also be difficult to control the position of the plasma flux lines on the inboard region without an inboard control coil.

• Ron Stambaugh suggested that the fusion power could be significantly increased if the elements of the inboard radial build that were not TF coil copper or plasma-related were lessened. For each 10 cm eliminated, the fusion power would triple. At the last meeting, the total thickness was about 49.5 cm. A 30-cm-thick shield was changed to 20 cm which would help. Perhaps the 5-cm-thick gap between the shield and centerpost could be eliminated, but Wayne Reiersen and Mark Tillack responded that a nominal gap is required to insure the ability to assemble the shield and allow for thermal expansion. The 5 cm is considered to be at operating temperature. Ron also thought the 10-cm-thick scrapeoff layer could be eliminated (see above). Inner wall limiter plasmas have been operated in both H-mode and in L-mode with internal transport barriers (for 5 seconds, DIII-D last week) with H factors as high as needed in the ARIES-ST strawman. .

• The final suggestion by Ron was to increase beta to help improve the power level. At A=1.4 to 1.6 and k=3, there is some incremental improvement in beta. But at k=3.4, there is significant improvement in beta. Ron volunteered to send some of his better cases to PPPL to compare the results with the two codes.

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

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

Alternate Applications Studies