Attachment: Action Item List
The definition of the TF coil elements within the coil boundaries used by the ASC code were unclear and need to be clearly defined by L. Bromberg. Definition of thickness of the vacuum vessel (VV) (5 cm local), multi-layer insulation (5 cm), and clearances (5 cm) were adopted as recommended, but more specific engineering definition and trade studies are needed on non-constant tension, D-shaped TF coils, modifying the coil cross-section inboard and outboard, and rounding corners of the coil pack. [Note that each 15 cm of improvement represents a cost savings of $300M and a COE improvement of 5 mill/kWh.]
D. Lee displayed a configuration associated with a modified 1/29/96 strawman. The 1/29/96 strawman geometry would not accommodate removal of a complete sector; therefore, Dennis modified the TF coils to meet the geometry constraints. This new configuration illustrated the possible power core design features and the areas where more work is needed to satisfy the developing geometry. The current size and location of the divertor, vacuum ducts, and piping were included. Dennis incorporated several ideas from S. Malang into the design. The outboard region of the vacuum vessel has moved from near the outer TF coil legs to closer to the back of the shield. It was recommended that the low temperature shield and the VV door be combined structures. S. Malang is to investigate how to accommodate the differential movement between the blanket/high-temperature shield and the low-temperature shield/vacuum door.
S. Malang presented a module structural concept to integrate all blanket, shield, and divertor elements together. He also recommended the use of a sealed container to transport the power core modules without contaminating the power core or building. There was a discussion regarding the use of a sealed transport container and a transport tunnel around the FPC Ð a final selection is TBD pending assessment of a building layout. A technique of supporting the power core sectors from the bottom of the sectors during operation and maintenance was presented and generally accepted. This support approach would work in conjunction with D. Lee's key alignment feature on the central column.
L. El-Guebaly presented results from her 3-D neutronics wall loading (NWL) analysis showing a range of NWL values ranging from 5.3 MW/m2 to 2.9 MW/m2 over the outboard First Wall (FW) and down to 0.5 MW/m2 in the inner divertor slot. A more detailed 3-D analysis is in work for the blanket and shield and will use the results of the next strawman. The 1-D results to date have shown adequate shielding of the VV and the TF coils with some local shielding necessary. More local shielding will be required behind the newly defined RF folded waveguides. Laila presented Khater's activation analysis for the blanket and shield evaluated with the new FENDL Xn data library. The stainless steel filler and vanadium structure will meet the NRC 10CFR61 requirements for Class C low level waste but will exceed the Fetter Class C requirements due to trace amounts of iridium. The Ir cross sections were not present in the ACTL library used to evaluate the ARIES-II design. Solutions for the iridium impurity are possible but costly. The cost of reducing the Nb impurity in V4Cr4Ti alloy from 4 wppm to 0.5 wppm needs to be assessed.
Mark Tillack gave the presentation on magnet systems for Leslie Bromberg. Three main topics were discussed: (1) Segmentation of the crown. Structural analysis indicates that the crown will require inter-coil structures. This appears feasible; but more detailed analysis is required. (2) PF coil design. Difficulties have arisen with the recently enlarged TF coils. The PF coils are enormous, and the required coil currents are too high for NbTi. Mark indicated that design changes should not be analyzed any further because the core design must be modified away from this obviously undesirable design point. (3) TF coil geometries. Two approaches to reduce the size of the coils were examined. First, since the coils are not purely bending-free with the cap structure, some additional forces may be acceptable to allow a more circular shape thus reducing the vertical height of the TF coils. Second, variation in the TF coil cross section from inboard to outboard legs was examined. Two possible approaches were proposed, both of which appear feasible and credible. These proposals will be considered in developing the final proposal for the TF coil detailed design, which is expected within 1 week of the project meeting.
D. Ehst explained his analysis results concerning plasma equilibrium, rotation, and ignition. Previous analyses had used less rigorous methodology and criteria, whereas the current analysis used a more rigorous, self- consistent solution. The results indicate that the plasma elongation should be reduced to 1.7 and that the RF current drive systems would provide adequate plasma rotation for kink stability (in conjunction with the kink stabilizing shell.) The ELM discharge frequency is estimated to be around 2 kHz. D. Ehst and T.K. Mau have differing analysis models and assumptions on the RF systems' efficiency (gamma) with results being described as conservative (for two systems) and optimistic (for three systems). By the end of the meeting, it was decided that the Starlite design should employ three RF systems with the exact definition of the type, frequency, and efficiency due in a week.
T.K. Mau described his current drive (CD), rotation and startup work. T.K. is using a low-frequency (or ICRF) fast wave subsystem to drive the central current, together with high-frequency fast waves and lower hybrid waves for off-axis drive. He showed that higher Zeff for improving the radiative mantle operation will reduce the CD efficiency. He also presented TFTR data on ICRF- induced plasma rotation. Then he discussed the startup requirements and some possible capabilities. It was recommended that T.K., together with Kessel, formulate a complete and consistent startup scenario and subsystem definition.
Clement Wong outlined the necessary work to complete the divertor design to meet the systems requirements and the project schedule. Tom Petrie of GA noted that relying on pure divertor radiation is not a good approach as it would be very risky and not robust, based upon his analysis and experience. A radiating mantle has been successfully demonstrated on DIII-D. In order to reduce the mantle thickness, Tom would like to raise the Zeff from 1.7 to 2.1. Further, he would recommend the added impurity to be argon, and he would also evaluate vanadium as it is already present in the FPC. The plasma edge density should be raised to reduce the mantle thickness further. Tom acknowledged that SOL radiation has not been included in the analysis, he will. rerun his analysis and then make the recommended changes. Clement illustrated the tailoring of the divertor surfaces to intercept the surface heat flux. Tungsten continues to be recommended as the divertor surface material.
Igor Sviatoslavsky presented a design for the vertical stabilizer coil connections. Details are to be coordinated with Malang's support structure. Igor also discussed support approaches associated with attachments to the vacuum vessel. Cooling system designs and data were also presented.
D-K Sze was concerned about the impact of the increase of the surface heat load from 0.5 MW/m2 to the range of 0.7-0.9 MW/m2. The area where problems occur is near the exit of the FW coolant passage where the coolant temperature is to be 610 deg-C and the wall temperature must not exceed 700 deg-C. D-K presented two corrective changes, and others were offered during the meeting. D-K will investigate a design solution. The liquid metal insulator recommended is CaO with AlN as a backup. The use of the insulating coating results in a low system pressure drop and low internal coolant pressures. The low-pressure coolant yields a low-membrane stress level in the first wall and blanket that infers a much longer in-vessel lifetime. C. Wong is to provide D-K Sze the final FW heating level. The narrowing of the passages near the inlet and outlet should help to minimize the temperature excursions.
T.K. Mau presented his design approach for the current drive subsystem. The ICRF CD subsystem uses twelve folded waveguides occupying a volume 1.83 m wide by 1.02 m high by 0.9 m deep. The depth will require additional shielding. It was suggested that the width should be narrowed with the height increased accordingly. Cooling of all waveguide components must be provided for surface, nuclear, and resistive heating. Details on the other two heating and current drive subsystems are to be finalized with scoping values to be provided in one week.
B.J. Lee presented his analysis and scoping activity on the 'fake' rotating shell. From the physics point of view, this system seemed to be effective and required little power. However, there did not seem to be a possible engineering solution to implement the system in such a severe nuclear environment.
Igor Sviatoslavsky presented the vacuum system design parameters. The conductance and throughput values seemed reasonable. The time to accomplish the rough pumping was the dominant time. It was recommended that Igor also assess the use of turbomoleculear pumps. Clement is to supply Igor the throughput requirements in order to better define the system.
D-K Sze reviewed the Mike Billone data for the vanadium design guideline. The main criteria developed was that the lifetime of the vanadium structure is determined by the primary membrane stress. The group expressed concern about a curve that showed the vanadium exhibited radiation-induced swelling at moderate dpa values, but the swelling reversed and approached zero at higher dpa levels. The group tentatively adopted a vanadium structure lifetime based on a more conservative 200 dpa limit as a reference case pending more analysis by M. Billone and feedback from the materials community. The value is important as it effects the power core replacement costs and the plant availability. Mike is also to provide a hydrogen limit for loss in ductility.
Jake Blanchard presented several design curves to relate primary membrane stress to lifetime for the first wall coolant channel. The results are related to the temperature of the backplate and the thermal heat transfer coefficient. D-K is to provide Blanchard the relevant vanadium heat transfer coefficient. Jake is working on a 2-E ANSYS model to generate the EM loads for the blanket and divertor within a week.
L. El-Guebaly presented the lifetime of the power core components. With the vanadium dpa limit increasing from 150 to 200, the life is increasing proportionally. The divertor radiation-influenced life is around 7 years, whereas the erosion limit may be around 2 years.
L. Waganer presented the current status of the Design Parameter List which was prepared by Waganer and Tillack. The team should update the list to current values so this list will be the official data source (along with the ASC Code).
C. Wong updated the group on the preliminary safety assessment for Starlite. The safety assessment was initially to be accomplished on ARIES-II but this has been eliminated in order to concentrate on the Starlite safety assessment. Bob Thayer is to complete the Starlite RS preliminary Safety Assessment in time for presentation at the June project meeting.
Igor Sviatoslavsky presented E. Mogahed's data on the loss of coolant accident (LOCA). It was noted that the modeling was not complete and several design features could easily be added to reduce the high temperature excursions.
Ron Miller discussed his latest inputs and data regarding the Starlite economic database.
C. Bathke reviewed his final LAR systems code results. [Ref, Interim Starlite Report, Section 9.2]. The betaN of the case is higher than the one presented at the LAR town meeting. Chuck had generated COE sensitivities on most of the important parameters. The group thought the result of removing the centerpost shield was not correct because the effect would drastically increase the changeout frequency; hence this option would infer more operational costs and lower availability. The case should be rerun with the revised cost and availability assumptions.
Person Responsible Action Item Description Status All Complete all major action items by 12 April 1996 (except as noted) All System Leaders Complete Design Data Book Table for FW/B, rf, individual systems. divertor, shield Bromberg/Bathke Determine if code correctly models TF coil system code models cross-section. Distribute drawing of inboard winding pack plus 2 mm and outboard TF coil cross section including insulation, plus winding pack, electrical insulation, protective coil case. shell, superinsulation and other elements. Memo in process. Bromberg Define best non-constant tension D-shaped TF DONE coil design, conduct trade study, and work with C. Bathke and D. Lee on configuration. Bromberg Determine cost, technical difficulty, and benefit Not needed - can do later to modify TF coil cross-section and round coil if space is tight pack corners. Bromberg Determine material for superinsulation and thickness. Will come in memo: Place only on hot structure, cold structure, or both 2 cm Al/fiberglas D. Lee Give Bathke Cryostat configuration. DONE D. Lee Thicken divertor upper and lower regions to 20-cm shield accommodate 15 cm pipes. (due next meeting) 9x20 cm pipes C. Wong Update Divertor power balance and design C. Wong Refine rationale for Divertor surfaces and define shapes by working with the Physics Group on the startup scenario. (due next meeting) Wong/Sviatoslavsky Develop Divertor structural design In progress C. Wong Recommend FW surface heat flux 1 MW/m2 still: with new flow paths, prob. OK C. Wong Determine Divertor gas throughputs, impurity species, and provide inputs for vacuum pumping and activation products calculations. I. Sviatoslavsky/D.Lee Determine capability to vacuum pump top and bottom. (due to Lee early enough so he can complete configuration by next meeting) I. Sviatoslavsky Assess turbomolecular pump option. doesn't look practical Mau/Kessel Define complete and consistent startup scenario and system definition. (due next meeting) Mau Define remaining RF system first wall penetration. DONE Mau Determine Zeff scaling of CD efficiency for ASC Code. Ehst/Mau Determine usage, efficiency, and power division of RF heating and CD system. Mau/Ehst Complete benchmark between CURRAY and RIP codes (due next meeting) Wong/Petrie Revise Divertor analysis including scrape-off layer radiation. Calculate mantle thickness as a function of Zeff with alphaN=0.44 or use Ehst's density profile. B.J. Lee Complete self-consistent analysis of high-recycling (due next mtg) divertor design with radiating mantle using new FMS code. Sze Recommend solution to excessive First Wall temps. currently with higher surface heating. Changes could include designing new flow narrowing of coolant channel at top and bottom, paths thinning channel, and counter-flow of coolant. Blanchard Recalculate design curve of FW coolant channel span DONE using appropriate coolant backplate temperature. Obtain heat transfer coefficient from Sze. (due next mtg) Blanchard Calculate disruption loads forces by 5/15 Billone Provide a hydrogen limit to avoid loss in Sent request to matl. ductility in vanadium. (due next meeting) group. Waiting. 1000 appm? Billone Affirm 200 dpa limit or suggest rationale to adopt DONE higher limit. Bathke Complete new strawman run by 19 April 1996 DONE May 7 Steiner Must have a completed Preliminary Safety Assessment of Starlite RS by next project meeting. Mogahed/Sviatoslavsky Refine LOCA model to include additional heat transfer DONE /Sze mechanisms and paths. Affirm heat source terms. Conduct analyses for both inboard and outboard blanket and shield. Coordinate with Sze and provide results to Steiner and Wong for safety evaluation. Sze/El-Guebaly Optimize radial segmentation to maximize lifetime of ongoing blanket parts. D. Lee/El-Guebaly Develop RF design and shielding approach S. Malang Develop flexible support concept for in-vessel components Malang/El-Guebaly/Lee Assess location of biological shield Malang/Waganer/Lee Develop scheme for transfer of sectors to hot cell