ARIES Documents -- Meetings ArchiveARIES Conference Call, 8 February 2011
Documented by L. Waganer
Les Waganer mentioned that the next ARIES conference call would be on March 3rd, 2011 at the usual time and phone number. The Doodle results for preferred dates for the next meeting were discussed and it was decided to hold the meeting on April 4 and 5 (Monday and Tuesday) pending agreement by Al Opdenaker [affirmed on 2/9/11]. Les just finalized the July meeting minutes and Mark Tillack posted them on line. Due to some technical changes in Xueren Wang's discussion on the FW design, the December 7th conference call minutes were revised and reposted.
ARIES Technical Efforts
Laila El-Guebaly has been concentrating on answering the January 2011 meeting action items. The first area addressed was the auxiliary power. In the January meeting, it was thought that we should adopt a value of 50 MWe pending a more thorough assessment. Laila found out that the cryo power would be on the order of 35 MWe and the miscellaneous power would be around 30 MWe based on ITER. She suggested keeping the total auxiliary power in the ASC at 65 MWe until she updates the magnet nuclear heating and corresponding cryogenic heat load.
The second action item involved the local NWL at the transition between the outer blanket and the outer divertor. These surfaces were aligned at slightly different angles that yielded differing NWL values. The UW-Madison researchers rechecked the data and artificially set the angles equal to confirm the analysis. The reported results were deemed to be correct as stated at the January 2011 project meeting.
Laila asked Xueren Wang for the modified FW and divertor skeleton to update the NWL calculations. He needs the flux surface configuration from C. Kessel to redefine the divertor surfaces.. Laila said that she was working on the definition of the SiC/LiPb and DCLL blankets. Siegfried, Mark and Xueren should send Laila the most current design definition of these two blankets. The FW of the DCLL blanket may have two configurations, advanced one with W pins and standard one without W pins. The team should develop enough data on these FW configurations and present this data at the April meeting to enable selection of the better approach at a future date.
There was a discussion, prompted by Laila, of the need for a LN2 thermal shield in front of the superconducting TF coils to help remove deposited heat at a higher temperature (77 K) instead of at the lower 4 K temperature of LHe-cooled coils. This was not representative of the prior ARIES practice, but the current community thinking is that this approach requires lower cryo power. However, this additional thermal shielding (in place of, or supplementing MLI) will add a few centimeters to the radial build but the cryogenic heat load will be lower. Leslie Bromberg was quoted as now being in favor of the LN2 thermal shield. Farrokh suggested using the ARIES-RS magnet as a baseline configuration for neutronic analysis.
Mark Tillack thought ARIES should proceed to use an advanced first wall design with W-pins that may have much higher performance than current technologies would permit. ARIES has a goal to push the performance envelope to assess the advantages, benefits and issues of new technologies to stimulate or help direct R&D initiatives. We are proposing advanced tungsten materials and alloys that are just being introduced with minimal test data, but we should continue to assess these materials for new first wall designs. Arthur Rowcliffe is now on board as a materials expert and he will help us understand the current and planned materials developments.
Laila asked about the FW coverage for these enhanced performance first walls. It was suggested we use 25% coverage as a starting point pending more definition from the edge physics modeling of Tom Rognlien and energetic particle modeling from Alan Turnbull. Farrokh noted that he had received the new heat flux modeling results from Chuck Kessel.
Alan Turnbull stated he received the ARIES-AT equilibrium data from the 2000 time period as a starting point (H-Mode edge).
Lane Carlson reported he is continuing to resolve the action items noted in the January action item list. He has corrected the PF coil number, volume and cost of the PF coils. He adopted the suggested auxiliary power requirements (65 MW) and set the SOL at 10 cm. He also has been working on formatting the output file and on implementing the changes suggested by Laila at the ARIES January meeting.
Xueren Wang reported he corrected the previously presented stress calculations on the tantalum transition section. He has been working on the first wall and blanket thermal stress analysis and creep modeling. He hopes to complete his analysis in time for the US/JA Power Plant Design Workshop.
Minami Yoda said that they were trying to resolve the large discrepancy in pumping powers between the experiments and the system code noted at the January meeting. Based on the discussion at the January meeting between Said Abdel-Khalik and Xueren, some of this discrepancy is probably due to the different areas (pressure boundary vs. tile) used to determine the heat flux. They are rescaling the experimental results to make them consistent with the system code, based on dimensions sent by Xueren. Other potential sources of discrepancy are differences in the inlet and outlet temperatures, so the GT group is also working with Xueren to obtain a common basis for comparison. Xueren said that the prior analysis of both the plate and finger designs used an inlet of 600°C and an outlet of 700°C, but he is planning on increasing the outlet temperature for the plate design to 750°C consistent with the use of "advanced ODS". Xueren explained this advanced ODS uses nano particles. Arthur Rowcliffe mentioned that this material is being investigated as a candidate fusion material. The creep issue can be handled, but the other issues are high temperature and corrosive (lithium) environments. Everybody acknowledged that when ARIES uses or assumes an advanced material (or process or subsystem) it should be clearly noted that this is not a current standard material or practice.
Tom Rognlien acknowledged that he has been working with Mark and Chuck on the conditions for the edge modeling with the U-Edge code. The main issue is how to scale for the local heat flux. He is hoping to have some results by the next project meeting. He is also concerned about the distribution of the impurity radiation (fRad) that can be up to 0.95, which is very high. He is using the ARIES-AT assumptions in the code. He is also assuming our traditional double null divertor configuration. Tom will send the Fundamenski scaling to Rob Goldston.
Rob Goldston has been modeling the SOL data from several recent larger fusion plasmas to predict the SOL for future machines. It was suggested he present his findings at our next project meeting.
Jake Blanchard reported he is investigating fracture failure modes on simple geometric models of tungsten tubes before proceeding to the more complex divertor designs. The two approaches are to either have data suggesting the critical flaw size or to determine detectable flaw sizes and extrapolate that to necessary material properties. He will pursue both analysis avenues.
Siegfried Malang and Mark Tillack were discussing the design issues of the high temperature heat transfer tubes, specifically the heat transfer across the boundaries in concentric delivery tubes. They will resolve the issue via a phone call next week.
Mark Tillack noted he was working on the FNS Pathways study and is preparing a table of requirements and justifications for the next machine. He solicited help from the ARIES Team in completing the table that is available on the ARIES web page, January 2011 ARIES meeting agenda.