ARIES Documents -- Meetings ArchiveARIES E Meeting, 3 May 2000
Documented by L. Waganer
The next ARIES meeting is scheduled for June 19-21 at the University of Wisconsin, Madison. It will cover both the final design efforts on the ARIES-AT (the first day and a half) and the IFE kickoff effort with an expanded ARIES team (during the day and a half). Les Waganer will issue a draft agenda shortly to help establish travel plans. Laila El-Guebaly issued a travel recommendation e-mail that noted two hotels with special UW rates within walking distance of the meeting location. She will revise the meeting room reservations to accommodate plenary sessions all three days.
Farrokh Najmabadi recommended the ARIES-AT presentations at the June meeting should reflect a final design position. We do not want to have any more iterations (physics or engineering) as we must converge on a reference design solution at this meeting.
The due date for the ANS abstracts has been extended to June 1. Farrokh requested that all ARIES abstracts be forwarded to him for coordination.
Neutron Source Study
Don Steiner has received all revised sections of the final report for incorporation. Due to other commitments, he has not completed the collection of the sections, but plans to do so next week and transmit the electronic version to the ARIES Executive Committee for comment.
Leslie Bromberg noted that he and his colleagues thought the fusion reactor configuration (ARIES-NT) required an inordinate amount of current drive power. This excessive recirculating power cast the fusion application in a poor light compared to the ATW. The response to that comment was that the referenced fusion plant design point was chosen somewhat because of the available physics database. Perhaps the reactor could be better optimized for this application. The estimate of the current drive power represents a significant extrapolation from known data; thus the current drive power requirements might not be accurate and certainly are not optimized. It was also noted that the fusion system was deliberately designed to use a blanket system that would not be close to criticality. This discussion highlights the need for clarity regarding the groundrules for the design and highlights the basis and the findings of the comparison between fusion and other alternative neutron sources.
Steve Jardin said that Chuck Kessel had completed the new EQDISK files for the fixed plasma boundary conditions and forwarded the data to T.K. Mau and Lang Lao for incorporation in their analyses. GA and PPPL are working to obtain an agreement on the equilibrium conditions for the ARIES-AT plasma parameters. T.K. Mau thought he would have the current drive data within a week. Steve noted a growing consensus that an active feedback control system is required to effectively control kink modes.
Steve also mentioned that in a recent FIRE meeting it was proposed (by Ming Chu?) that an ICRF system might produce a localized rotation and might provide adequate rotation for an ARIES-AT type of plasma. T.K. Mau said that he would assess this possible application and report estimated system requirements at the next meeting. It might be within the parameter space of the currently proposed ICRF system. Lang Lao also has an action item to investigate the effectiveness of non-NBI plasma rotation systems.
Farrokh said that UCSD really needed the plasma free boundary conditions ASAP for divertor definition. Chuck Kessel joined the call later and reported that he had already completed these calculations and would send them shortly. Chuck noted the PF coil data is similar to that predicted and used in the ARIES System Code, hence there is validation of prior results.
Farrokh Najmabadi wanted PPPL to determine if a passively cooled tungsten shell might adequately control the plasma vertical stability. At the last project meeting, it was decided to use a cooled, solid copper shell clad with a thin shell of tungsten. But the plumbing to this component is very complicated. If the shell were on the order of 2 cm thick, a passively cooled tungsten shell could be used, simplifying the design. Rene Raffray’s analysis indicated that a 2-cm-thick tungsten shell would operationally reach 1088°C, steady state. In addition to the outer shells, the inner shell and a thin tungsten surface layer on the divertor plates would enhance the plasma stability. Chuck Kessel will assess if the thinner tungsten shell is feasible with adequate response times and power levels.
Ron Miller affirmed that the 10 March 2000 strawmen (R=5.2m) are still the most current data. He used the new EQDISK data from Kessel to confirm that the prior extrapolations were reasonable. However, the self-consistent current drive data has not been incorporated yet. Ron did a sensitivity analysis on the physical size of the core. He determined that the PF coils were restricting the core size, but the COE gains for a smaller size core (R~5.0 m), higher fields, and higher power loading only yielded a modest COE reduction on the order of 1 mill/kWh (2%). Thus Ron recommended retention of the current baseline definition.
Ron also incorporated the high temperature superconductor material in place of the Nb3Sn superconductors. They are both about the same size and field strength, but the cost should be lower. The coil structure will be Inconel.
Mark Tillack mentioned that the plant availability would be included as a variable based upon data generated by Mark Tillack and Les Waganer. It is hoped that the plant availability would be in the range of 80-85% (similar to fission plants).
Configuration and Maintenance
Xueren Wang said that he had been updating the CAD files. An updated cross-section view has been posted on the Web page, but the remainder of the CAD update has not been completed or posted. Les Waganer said that his viewgraphs show an updated vacuum vessel design and recommended Xueren examine the preliminary dimensions and revise as necessary.
Mark Tillack said that he would be working with Lee Cadwallader, INEEL, to estimate the plant unscheduled unavailability data. He mentioned some SiC heat exchanger data was available.
Neutronics and Shielding
Laila El-Guebaly mentioned the collaboration with Les Waganer on the combination of the vacuum vessel and the low temperature shield functions into a single component. They agreed on a common composition and thickness of the vacuum vessel for the inboard and the upper and lower divertor regions. Laila reviewed her electronic viewgraphs (see the ARIES web agenda for link) that addressed revised radial builds for the inboard, outboard, and vertical regions. Thicknesses and compositions of several components have been altered (as shown in red text in her presentation). The copper shell with tungsten cladding is included in her analysis. The tritium breeding ratio is at the required limit of 1.1 for the case of a 5 cm thick Cu shell with 0.3 mm W cladding and 10% He coolant. A few cm thick W shell will drop the breeding level below 1.1.
She mentioned that the replaceable sections of the first wall and blanket have been increased to a lifetime of 4 full power years, which will help reduce the annual replacement costs. The inner layers of the vacuum vessel would exceed the project-assumed reweldability limit of 1 appm He, however the EU has reported data suggesting a limit might be as high as 5 – 30 appm He. Laila is working to confirm these data. The predicted end-of-life conditions are 15 helium appm and 30 dpa neutron damage.
Laila expected to send out a new nuclear heating load definition by the end of the week.
Laila requested additional definition of the headers and plumbing in the divertor region from Xueren and Rene to help her estimate the damage to the magnet above/below the X point where the IB shield recesses to accommodate the inner divertor plates.
TF and PF Magnets
The group noted minimal work on the high temperature superconductor (HTS) magnets being used. Tom Brown and Fred Dahlgren requested the latest CAD drawings from Xueren so they can begin definition of the coil systems. Laila had some preliminary magnet composition and requested that Leslie Bromberg update/validate the coil data.
During the discussion of sector maintenance approach and design of the sectors and vacuum vessel door frames, Laila suggested the team consider altering the TF coil cross-section from the inside region (small radial dimension) to the outside region (reduced toroidal dimension.) Changing the aspect ratio of the coil would allow a smaller bore magnet for removal of the same core sector or removal of a larger core sector for the same coil bore size. The use of the HTS might facilitate this design modification. Leslie Bromberg should evaluate this option.
Blanket and Divertor
Rene Raffray reported that the coolant routing from all blankets and divertors have been finalized, achieving the goals of flow balancing and passive drainage. More detail will be shown at the upcoming meeting. Due to sizable flow restrictions in the divertor channels, electro-magnetic pumps might be used to locally boost pressure and flow within the divertor.
Rene discussed the difficulty of in-situ maintenance of the blanket and divertor modules – many fluid connections and mechanical joints to disconnect and connect. Thus the baseline maintenance approach is the sector removal.
Rene said the thermal blanket analysis indicated the highest interface temperature of SiC/LiPb to be 940°C (as opposed to the 950°C data reported earlier). Substantiating details will be presented at the upcoming meeting. Rene has begun more detailed stress and thermal analyses of the divertor components. The group noted that an ALPS liquid metal divertor design is being investigated as an optional design for the ARIES-AT power core.
Les Waganer presented an updated, preliminary design for the vacuum vessel and welcomed comment on a few critical issues (see agenda for presentation link). The basic structure is a double-walled vessel with constant cross-section on the top, inner, and bottom elements, forming a cylindrical structure with two large flanges, all with internal, top to bottom ribs. The design is consistent with the CAD elevation views provided by Wang. Double curvature doors are attached to frames, which are anchored to the basic vacuum structure. These frames are not yet defined or shown. The doors also have internal ribs, running top to bottom, just like the basic vacuum structure. Les examined the high temperature wedge (just inboard of the vacuum doorframe) that extends into the high temperature Blanket II and Shield zone. Construction options were either high temperature SiC/SiC structure with flowing LiPb or an insulated, low temperature ferritic steel structure cooled with water. Both approaches had design difficulties and no consensus recommendation was reached. Laila mentioned that the FS structure will not survive the high radiation environment behind the blanket-I and will require frequent replacement during the plant life. The wedge provides protection for the coil and its composition should match the optimized composition reported for the OB radial build. Waganer will propose more design approaches and try to achieve a recommended solution. Xueren should refine dimensions as required.
Vertical Stability Coils
As noted earlier, Najmabadi recommended an assessment of a thinner, passively-cooled tungsten shell to determine the power levels anticipated and the response time for a range of thicknesses and conductor options (action: Kessel). (See last paragraph in the Physics discussion.)
Laila said that they are continuing to update the activation and the LOCA/LOFA analyses with new materials and compositions. She provided preliminary data to D. Petti for his Waste Management Analyses.
Dave Petti noted receipt of the materials, quantities, and activation levels from Laila and the geometry from UCSD. Without any cleanup system, the polonium 210 isotope will continue to build up to approximately 40,00 Ci, 25 Ci, whereas the release limit is 25 Ci. Obviously, a coolant cleanup system is necessary for the polonium. Dave needs a definition on the main heat transfer system to better understand and analyze the possible fault conditions. For instance, how many separate coolant subsystems are planned? Are there multiple, separate coolant manifolds and heat exchangers? Are there multiple or one drain tanks? We need a good definition of the entire heat transfer and transport system (Sze). We also need a good definition of the coolant cleanup system for bismuth and plonium (Sze).
Dave also mentioned a possible interaction between the LiPb coolant and the water in the vacuum vessel. Waganer should define the water and temperature design limits. Waganer noted that Mike Billone should define the recommended temperature limits (maximum and minimum) for the ferritic steel used in the vacuum vessel, which will establish the coolant operating limits. Mark volunteered to contact Mike Billone to recommend ferritic steel operating temperature limits for the vacuum vessels.
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