ARIES Documents -- Meetings ArchiveARIES E Meeting 6 June 2000
Documented by L. Waganer
Farrokh Najmabadi emphasized that the June meeting is very important to the success of both the concluding and commencing studies. The team should be prepared with final design details for the ARIES-AT. No final report drafts are expected at this point since some technical changes may arise during the meeting. All ARIES-IFE team leaders should be prepared with a one-page viewgraph of task activities and expected results. The draft agenda is full, but time should be allotted at the end of the AT and IFE presentations to focus the team toward identified goals.
Farrokh summarized that the intent of the conference call was to assure that the AT project will come to closure on the final design at the June meeting and the IFE project will commence toward a common goal.
Les outlined the conference call agenda to assure that all salient technical details were addressed or resolved toward Farrokh’s goals. He also reviewed the draft meeting agenda. Any presentation changes should be sent to L. Waganer.
Laila El-Guebaly said that all meeting preparations have been completed. She has some campus parking permits for sale. Twenty-five people have confirmed attending the meeting. With the 10 or so participants from UW, this would bring the attendees to roughly 35. Laila said she is planning a group dinner on Tuesday night. Details will be provided at the meeting.
Vertical Stability - Chuck Kessel said he is concluding his vertical stability and control analysis. He has been assessing the plasma stability conditions with a range of tungsten shell thicknesses and positions within the blanket and shield. The tungsten shells are passively cooled and located directly behind the inboard and outboard blankets. He found that 4-cm-thick shells (both inboard and outboard) are the minimum allowable thickness with reasonable system power levels (~40 MVA [updated value]). He is now investigating the modification of the startup plasma conditions (the operating plasma conditions are unaffected) to raise the pressure to obtain a more stable plasma.
Coils - Chuck transmitted the PF coil sizes, currents, and locations to Fred Dahlgren for analysis. Mark asked about the issue of the magnitude of the magnetic field perpendicular to the TF high temperature superconductors (HTS). Fred Dahlgren noted that the field has been determined to be in the range of 3 to 4 Tesla, which would be acceptable. Above 4.5 T would be a concern.
Kink Stability - There seems to be a difficulty with the plasma kink stability given the present blanket configuration of the toroidally discrete liquid metal coolant, insulating layers, and the SiC structural elements. A more conductive path is needed to improve the kink stability. Possible solutions might involve a major redesign of the blanket configuration. Action - This topic will be resolved off line with a solution to be presented at Madison. Lang Lao also confirmed that he is concerned that the kink stability of the existing design may be marginal. He will do additional calculations and confer with Kessel.
Heat Flux on Divertor – Lang Lao noted that GA is working on assessing the heat load on the divertor using the proposed plasma profiles. Data will be presented at the Madison meeting.
Current Drive – T.K. Mau received the latest EQDISK files from Chuck Kessel and has assessed various RF CD systems to achieve the required current drive conditions across the plasma profile. The on-axis CD requirements can be achieved with fast wave (FW) at 68 MHz and a power (input?) of 5 MW. Off-axis CD requirements are proving to be difficult on this particular plasma condition represented on the current EQDISK file, probably related to magnet field and plasma density gradient levels. A lower hybrid system at 4 MHz would require 30-35 MW of power, but it does not adequately penetrate beyond the reverse shear region. A third RF system, perhaps high harmonic fast wave, might be required. Action - Chuck requested TK’s data to determine if field or density gradient adjustments might improve the matching of the RF system parameters to the plasma conditions.
Ron Miller said he had incorporated Kessel’s latest EQDISK plasma equilibrium file including the beta margin. The new file sufficiently replicated the prior strawman data; thus the strawman results remain valid and will serve as the nominal case for upcoming parametric assessments. The PF and TF coil sets are nearly optimized with only slight changes envisioned. The CD and plasma rotation power algorithms are to be updated with expected increases in power levels. Vertical and radial build data sets from El-Guebaly have been incorporated in the code. Action - The divertor heat load from Petrie needs to be obtained and put into the code. The plant factor or availability will be handled parametrically in the near term. Waganer is working on power core scheduled outage data. The impact of higher net power plant output will be assessed. The effect of BetaN will be evaluated parametrically. High temperature superconductors have been incorporated in the code with minimal impact on the technical baseline or plant economics.
Configuration and Maintenance
Xueren Wang told the group that he had been finalizing the ARIES-AT CAD model and has incorporated the design features of the vacuum vessel provided by Les Waganer. At Laila’s request, he added 15-cm thick local shield behind the divertor pumping duct to protect the magnet. Laila proposed to attach the local shield to the magnet and cool it with LN to act as a heat sink during LOCA/LOFA. Xueren reviewed the latest design approach of the power core. Tom Brown noted that his models have indicated interference between the vacuum doors and removable power core sectors and the TF coils at a level corresponding to the top of the vacuum vessel. Action - Xueren Wang and Tom Brown should exchange CAD files to resolve the interference issue and update their models with the latest data. Xueren said that he expected to finalize the TF and PF coil locations and TF coil geometry, structure, and support system.
Les Waganer described his design for the vacuum vessel. It incorporates the 16 large maintenance doors. These doors are held in place with large locking jacks and sealed with welded bellows. The design has been defined sufficiently to accomplish a preliminary costing estimate. Action – Waganer to get vessel costing to Miller. Les pointed out the new high temperature wedge design with SiC structure, cooled with LiPb. The LiPb plumbing connection probably will need to be routed through the upper portion of the vacuum vessel as routing through the narrow, water-filled doorframe would be nearly impossible. Laila stressed on the need to carefully design the wedges to assure adequate protection for the magnets. Action – Raffray to add plumbing for high temperature wedge and El-Guebaly to determine nuclear heating deposited in the wedge and assess the shielding of the magnet.
TF and PF Magnet Design
Tom Brown is using Xueren Wang’s CAD model and the strawman data as the basis for his TF and PF designs. He questioned the added shielding above (and below) the vacuum vessel to protect the TF coils from neutrons streaming through the added vacuum ducts. Tom intended to use that space for TF coil structural supports, so perhaps these functions could be combined. Action – Exchange CAD drawings and refine the structure. Transmit design details to Laila to assess the effectiveness of the structure as shielding.
Fred Dahlgren said he is building a composite structural model of the ARIES-AT that he is using to conduct preliminary stress analyses of the coils. He had been assuming Inconel as the structural material and questioned if ferritic steel should be considered as the coil supporting structure. Elsayed inquired about the operating temperature of that structure – it was affirmed the structure would be at liquid nitrogen temperatures. Ron was concerned about the added refrigeration systems and cost associated with this region. Laila mentioned that the total nuclear heat load to both the shield and magnet is the same as for the magnet without a local shield.
Leslie Bromberg said he has finished the FED paper on HTS coil design. He will be presenting the ARIES-AT HTS coil design at the upcoming ARIES meeting.
Blanket, Divertor and Related Materials
Rene Raffray is finishing his pressure and thermohydraulic analysis for the blanket, divertor and associated plumbing subsystems. He and Igor Sviatoslavsky have been refining the plumbing routing. The tungsten-plated SiC divertor design is also being completed.
Rich Mattas and Yousry Gohar noted that an alternate liquid metal divertor approach for ARIES-AT would be presented at Madison. They are evaluating the use of SnLi, Flibe, and lithium as possible surface/coolant materials. The concern is the compatibility with the higher operating temperatures of the first wall surface material.
Mike Billone said that he is struggling to obtain material recommendations on several issues. He can support a ferritic steel vacuum vessel operating in the region of 100 deg C and with low pressure water. Other material limits and recommended processes will be presented at the meeting.
Vertical Stability Shells
Igor Sviatoslavsky reiterated the design philosophy to run the 4-cm tungsten shells at high temperature with passive cooling. He is currently assessing methods of mounting the shells between the blanket and the hot shield. He is also analyzing methods of passively connecting adjacent shells for toroidal electrical conductivity.
Neutronics and Activation
Laila El-Guebaly discussed two approaches to incorporate the discrete tungsten shells into the neutronic model. She is selecting the better approach to present at the meeting. The outboard radial build will change slightly. The activation analyses of the shells and divertor are in work.
Elsayed Mogahed is refining the thermodynamic analysis model to assess the LOCA and LOFA conditions. The data for the vertical stability shells and the divertor are being added. Action – Mogahed requested additional information on the temperature of the structure above the vacuum vessel. He is currently using the 100 deg C conditions relating to the vacuum vessel.
Target Physics – John Sethian discussed the general principles and recent progress relating to laser direct drive targets. To achieve high gain, the fuel must be kept cold and retained at proper density. The current thinking is to separate the ablator from the fuel so the ablator can be heated, to mitigate the instability, but keep the fuel can be kept cold to maximize gain. There are several ways to achieve this "tailored adiabat" target. One is to put a high Z material, such as gold, on the outside. The gold may be dispersed or applied as a single layer. Another approach is to use shock waves to preheat the ablator. In any event, the target design must be compatible with the techniques used to "layer" or smooth the inner surface of the DT ice. One method of creating a smooth the layer is to cool the DT to about 1 degree below the triple point and then apply infrared heating through a laser to preferentially (slightly) warm up and redistribute the rougher (thicker) areas. Note the target temperature stays constant during this process. Target gains of 124 have been calculated in 1D for the direct drive tailored adiabat target. It is highly desirable to focus the laser beam spot size and to follow the diameter of the imploding target. With KrF lasers, this can be achieved.
Chamber Physics - Bob Peterson generally discussed the X-ray and blast effects of the direct drive targets. When asked about indirect targets, he said they generated a different spectrum of X-rays and debris as influenced by the hohlraum. Velocity of the DT after explosion is in the range of 108 cm/s, thus the kinetic energy imparted to the wall is significant. Higher Z materials may have lower velocities, but they would still have significant kinetic energy.
Don Haynes noted that the chamber gas, nominally thought to be xenon or krypton, would help attenuate the blast effects. The opacity of the chamber gas is important to the transmission of the laser beams through the chamber. Jeff Latkowski mentioned xenon is usually considered as the chamber gas, but it will become activated over time. UW is currently assessing the activation of the Xe gas and results will be presented at the meeting. With a dry wall concept, the chamber pressure would remain rather constant. With liquid walls or protected walls, the pressure would peak as the protection material is vaporized and decrease as the material is recondensed. Don will address the merits of several gas protection approaches in the meeting.
Ron Miller mentioned that he, Wayne Meier, and Les Waganer have conferred on approaches, models, codes, and data that might be applied to this study. Ron noted that the codes were in various states of disrepair and neglect. It might be best to start from a clean sheet. Les noted he scanned the two final reports of the IFE studies conducted in the early 1990’s and converted them to PDF files. Mark Tillack posted them for reference on the ARIES web site. Likewise, presentations from the recent Inertial Fusion Energy Direct Drive Target Workshop have been installed on the web.
Target Selection and Design - Ken Schultz said he was planning on presenting in Madison a set of target classes with similar spectra, behavior, and performance. Target gain and energy level also might be discriminators. Target gain curves would be determined at a later date. An example of classes might be:
Target Fabrication and Injection - Ron Petzoldt discussed fabrication and injection methods for both direct and indirect target designs. He also noted that tracking the target would be investigated, as it is a critical technology. Jeff Latkowski said he had a description and comparison of several targets that he would forward to post on the ARIES web.
Driver and Driver/Chamber Interface
Driver Selection and Design – John Sethian said that he would present at the meeting a summary of candidate drivers, such as the KrF and DPSL lasers (and heavy ions?). Driver and chamber interface issues will also be covered.
Chamber Assessment – [Time was running out on the call. The task leaders in this section said they had material relating to this subject, but it was not necessary to discuss these issues during the present call. Presentations at the meeting would suffice.]
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