Starlite Conference Call Minutes

10 July 1996

Participants: Sze, Dove, Dean, Wong, Bathke, Waganer, Bromberg, Jardin, Miller, Najmabadi, Mau, Malang, Tillack, Sviatoslavsky, Blanchard, Petrie, Mogahad, Khater

Administrative

Minutes of the 20-21 June Starlite Meeting at the Reno ANS conference have been reviewed, distributed, and posted on the Starlite Home Page.

Mark Tillack has been collecting inputs for the 6th Quarterly report. [P.S. He published a DRAFT on 12 July.]

Mark is also collecting the outline for the ARIES-RS final report - the most recent version is posted on the Home Page.

Laila El-Guebaly has secured a meeting room for the next Starlite meeting to be held in Madison on 20-21 August. It was felt that the design status is not firm enough to warrant a review meeting at that time. Moreover, Bill Dove stressed that DOE would like to take an active role in setting up and managing the peer review process. Thus, the Madison meeting will be limited to two days. But do not try to sneak out early, as I am sure we will need two full days.

Bill Dove gave some insight as to the fusion budget markups by the House and Senate, with the Senate being slightly higher.

- D. Ehst should send all Starlite institutions copies of his Reno presentation for their reference.

Safety and Licensing

Ron Miller reported the highlights of the recent conference call with Don Steiner, Clement Wong, and himself. The main topic was how to deal with the LSA ratings and their influence on the economics as relating to the preliminary safety analysis. The Starlite safety design goal is a no-evacuation plan. RPI will continue to evaluate our potential accidental releases and compare the accidental dose with this goal. In the meantime, we will retain the LSA rating description in the system evauations.

Bill Dove mentioned that the DOE Fusion Safety Standard has now been approved and is to be applied on all future DOE fusion facilities. Based upon suggestions and input from the Starlite and EPRI Utility Advisory Committees, the standard allows more freedom to meet the overall requirement and does not have the proscriptive logic associated with the fission safety standards. The top level requirements are specified, but the method to achieve these requirements is left to the project. ITER is trying to meet this standard to the maximum extent.

Physics

Steve Jardin summarized the difficulty to increase the amount of power radiated by the core plasma while keeping the plasma parameters relatively correct and the current drive efficiency (power) within reasonable bounds. The total power to be dissipated, to the first wall and the divertor, is of the order of 540 MW. As reported in the Reno meeting, Steve had looked at xenon impurities and concluded that there are no advantages for using a lower Z material. Instead, he would suggest analysis of vanadium as an injected impurity. [Later in the call this was reversed.] T.K. Mau looked at the efficiency of edge-driven current drive and found that it was very sensitive and inversely proportional to the edge density. Steve and T.K. looked at Z = 1.5, 2.0, and 2.5 cases with an edge density of 20% of the central core density. They provided their data to C. Bathke to run the systems code to determine the sensitivity of the integrated system performance and cost to the Zeff data. Chuck found that there was no solution at Zeff = 2.5. At Zeff = 2.3, the line radiation was around 90 MW. Chuck mentioned a radiation fraction value, but the group questioned the value and Chuck will verify the result.

There was a discussion regarding if a flat profile can be expected for reversed shear operation. Has there been experimental evidence observed to justify the relatively flat profiles that would likely be needed for radiating significant amounts of power from the plasma edge? Around 100 MW of Bremstraughlung power could be radiated from the central core if the central core temperature is relatively high. If the scrape-off region could handle up to 100-120 MW, the divertor should be able to handle the remaining 310 MW on the divertor surface area. Farrokh Najmabadi suggested the use of neon to radiate only in the scrape-off layer and in the divertor. Tom Petrie had been performing calculations to predict the power balance. Farrokh suggested rerunning Tom's code to confirm the final numbers. The amount of neon is to be adjusted for an additional Zeff of 0.7. There should be a minimal amount of neon in the core plasma. The peak-to-average density would be limited to 0.2 as opposed to 0.3 in the previous runs. The scrape-off region should be assumed as 2 cm thick as opposed to 1 cm. These results are to be available by 17 July.

System Studies

In the discussion of other areas, C. Bathke summarized his accomplishments since the last meeting. He had been working with the Physics Group to run the ASC code to better understand and map out the viable plasma parameter ranges. He also reported obtaining and incorporating the revised engineering data. Some engineering data obtained during this conference call will be added. When the power division question has been settled, he will then complete the next strawmen code run.

Engineering

Inputs to the ASC code - Revised radial build data were provided by L. El-Guebaly to be consistent with the new segmentation scheme. Laila also provided revised nuclear heating data for the entire blanket and shield.

Divertor - C. Wong explained that UCSD is using 2 MW/m2, average, and 5 MW/m2, peak, as the divertor surface heat load. With the current approach to distribute the radiation power, most of the power will be concentrated at the divertor throat and less so in the divertor slots. This may help in radiating nearly half the power back to the plasma chamber. C. Wong reported that (in discussions with Steve Jardin) during startup, the plasma would rest on the outboard first wall only for a short time and would deposit approximately 10 MW of heat. Therefore, no additional limiter will be needed. Siegfried Malang proposed a design approach that allows pumping on both the inboard and outboard slots. J. Blanchard discussed his attempts to model a VDE plasma by using ANSYS. He is hoping to have a student to run and complete the simplified model by the end of the summer. If results are reasonable (and consistent with the ITER prediction?), these data can be used as structural requirements for the divertor. Igor Sviatoslavsky mentioned that his new divertor structural design should have plenty of capacity to handle the anticipated VDE loads. Meanwhile, Igor is looking at techniques which would minimize the induced toroidal currents. He also discussed the toroidal vacuum manifolds above the upper shield to aid the vacuum pumping and use a discrete duct for each sector. The ducts then vent into the common vacuum vessel area.

Magnets - C. Bathke reported working with L. Bromberg to define the minimum PF coil necessary that required the use of NbSn superconductor. The mass of the coils is the most important parameter. This trade study is continuing, but it is not likely to yield a case that will allow the use of NbTi. Waganer has reported in the recent meeting minutes that the outboard TF coil cross-section could be either the rectangular or the inverted trapezoid cold cross-section, but the group thought this was incorrect. L. Bromberg and others clarified that the TF current carrying cross-section was rectangular in both the inboard and outboard areas, while the extra material on the inboard area is now used for structure. On the outboard area, this extra material can be removed and replaced with other strengthening material outboard of the TF coils. The inverted trapezoid arrangements should not be used on the outboard leg.

Blanket and Shield - D-K Sze reiterated that the first wall and blanket would be designed for a 1.0 MW/m2 average heat load. Thanh Hua will finish the thermal-hydraulic analyses by the end of July 1996. There was a question of who would do the thermal-mechanical stress analysis (Blanchard, or...?) No resolution.

E. Mogahed said he would rerun the LOCA analysis without any conduction terms between the blanket and shield elements. Emissivity values would be raised to 0.8 on all surfaces to help radiation heat transfer (~ 45 degC improvement, but not enough by itself). It was suggested he modify his afterheat input to reflect the increased use of vanadium. There was also a lot of discussion about the use of passive convection loops. A common design and fault condition are needed. (Action? Who?) Mogahed said he would have results using the prior assumptions (from the meeting) available by 12 July. Results from the new inputs are TBD.

Design Integration and Configuration Development - A conference call is planned during the week of 15 July to help define the baseline configuration to be used by the Engineering Group. Focus areas will be the vacuum door design and placement, TF coil configuration and clearance, vacuum duct routing, piping and manifolding, and maintenance provisions.