Project Conference Call

7 May 1997



Participants:

(DOE) -
(UCSD) Mau, Miller, Najmabadi, Tillack, Wang, Malang
(PPPL) Dahlgren, Heitzenroeder, Jardin, Reiersen
(GA) Stambaugh
(UW) El-Guebaly, Khater
(FPA) -
(RPI) -
(ANL) Sze
(MDA) Waganer

Administrative

Les Waganer took the roll call and reviewed the conference call (CC) agenda. L. Waganer completed the 7th ARIES Progress Report and M. Tillack installed it on the ARIES public and private web sites. Mark stressed the importance of these reports to DOE and the fusion community. Therefore the team should make a serious effort to prepare materials for the reports and review the drafts in a timely fashion.

The group affirmed the Madison meeting dates to be 17-18 June (full days on Tuesday and Wednesday). It has been suggested that Monday, 16 June be devoted to a town meeting, highlighting guidelines and rules for designing reactor components with brittle materials. Tillack, Sze, and El-Guebaly will coordinate the town meeting agenda and presenters (e.g., Zinkle, Klueh, Billone (or alternate), Majumdar, et al. Coordinate with Wiffen?). There is no separate physics group meeting planned, but TK Mau (and Bob Miller of GA?) wanted to meet with Prof. Ray Fonck to discuss the Pegasus design and systems - others are welcome to join them during Monday afternoon.

Highlights of the recent ISFNT-4 at Tokyo were noted by L. Waganer in the CC agenda. M. Tillack volunteered to install all ARIES-related ISFNT-4 technical pre-print papers on the ARIES Web site and to print the collection as a UCSD report, as with previous collections. Please send him your most current version.

M. Tillack also mentioned he is trying to alter the TBWG meeting date or location to enable ARIES members to attend the October IEEE/SOFE symposium.

Plasma Physics

TK Mau presented a paper on RF current drive in ST tokamaks including power plant results at a recent RF topical conference in Savannah. In this conference, he saw latest papers on electron-cyclotron wave current drive for use in the spherical tokamak devices, but it remains speculative at this stage. TK has also looked at coaxial helicity injection (CHI) for startup and CD, but it has poor profile control which is not good for steady state operation; hence, it may only be appropriate for startup operation. He also mentioned a paper which documented JET results on RF-induced plasma rotation in H-mode plasmas. TK is also investigating bootstrap overdrive for startup in the ARIES-ST machine. He will discuss his conclusions at the next meeting. Ron Miller asked about the effect of finite edge density on the current drive power requirements. TK answered that he would look into this issue after updating his ray tracing code to look at the latest A=1.4 strawman data.

Ron Stambaugh said that Bob Miller of GA will be handling the GA plasma modeling. He will specifically look at the finite edge pressure gradient (p') and radiating mantle. Ron Stambaugh noted a general trend of the physics models to prefer the higher aspect ratios (A), up to 1.6 and higher. He noted that this trend may impose engineering limits involving the tritium breeding ratio (TBR) and the power loss associated with the center column (when will it be necessary to add a functional blanket to the center column?) The code should be able to generate the blanket surface area for any aspect ratio. F. Najmabadi noted that the relationship of the TBR to the aspect ratio is not monotonic, but rather depends on the blanket concept. (The inherently higher TBR of a liquid lithium blanket is more forgiving regarding blanket coverage.) Also, we should be careful to note that CHI is not necessarily required. The group also noted there is no consensus for the required level of TBR for a commercial plant - many factors remain to be quantified and verified including the relationship between the 1-D and 3-D modeling. L. El-Guebaly, with support from Ron Miller, will try to do an aspect ratio trade study for the overall TBR and energy multiplication for the outboard and inboard regions.

Steve Jardin said that most of the ARIES physics group are working toward the documentation of the FED paper. They are also working on the figure of merit paper, being led by TK Mau. There is new data from the START experiment which will be added to the paper. On the new tasks, the ST plasma data is to be examined with plasmas having elongations of 3 to 3.5 and aspect ratios of 1.4 to 1.6. These will be examined with various divertor geometries and scrape off thicknesses. Steve noted that in the last TFTR runs krypton impurities were used with higher radiated power in the mantle without affecting the energy confinement time.

It was reported by Dai-Kai Sze that Martin Peng said that no (vertical) stability shell is needed in a LAR or ST plasma. Steve Jardin said that this was true below certain beta values; but, in plasmas of interest, the shells would be needed. Steve will confer with Martin to resolve this issue. M. Tillack subsequently noted that the Engineering Group is waiting for the Physics Group to define the engineering requirements for stability (location and conductance of the LAR/ST active and passive stability systems) for incorporation into the blanket design and overall configuration.

Engineering

Centerpost Design - Wayne Reiersen said the centerpost design optimization code continues to be developed. He intends to compare the IBC, water-cooled copper, cryo-resistive aluminum, and high-temperature superconductor centerposts. He has been developing the power flow diagrams for all options so they can be fairly compared (modifying the toroidal field values to achieve a nominal 1000 MWe.) Additionally, two different blankets (with different operating temperatures) and different divertors and coolants would be incorporated into the model. The end result is to weed out the poor performers. The group thought the analysis had too many options (blankets and divertors), and the modeling did not adequately consider other interrelated factors. The systems code could do a better job of analyzing the interactions of the various systems and the plasma if the engineering systems are properly modeled for inclusion into the systems code. It was recommended that only the CP performance and power balance requirements be defined for all options. These data would be input into the systems code for a global comparison. M. Tillack will coordinate the establishment of the remaining inputs to enable R. Miller so he can do integrated system studies of the CP options (for the next meeting)]

IBC Centerpost - Wayne Reiersen said that most of the IBC information was contained in the prior discussion. It was noted that the larger IBC power supplies would be a significant cost item that would warrant some scrutiny in the cost accounting.

Nuclear Aspects - Laila El-Guebaly said that the 3-D modeling is currently based on the 2-year-old ST design. She needs a new definition of the blanket design from D-K Sze (breeding material and coolant). She noted that there is a new ORNL-developed ferritic steel (ORNL 9Cr-2WVTa) that is more radiation resistant than the Japanese F82H ferritic steel, per R. Klueh. The ORNL steel will be used for the ST design as the main structural material.

First Wall/Blanket and Thermal Conversion - Dai-Kai Sze noted that the LAR has a severe FW limitation, which eliminates most "conventional" first wall and blanket designs. He and S. Malang have been working to define two blanket options that may offer a solution.

* The first is a helium-cooled, ferritic steel first wall. The blanket also uses FS as the structure, lithium-lead as the static or slowly circulated breeder, and a SiC insulator/separator material (non-structural). The helium first cools the first wall and then the blanket system. The thermal conversion system is a high temperature (700-750 C), closed gas cycle.
* The second option is a free surface first wall (and blanket) of lithium oxide pellets. This approach also might be used for the divertor systems. The next step is to propose a viable method to shape the free surfaces and examine the pumping power and heat transfer issues.

Safety Analyses - H. Khater reported he is updating their code to use FENDL-2 in place of the older FENDL-1. They still need the INEL volatility data to determine the release data from the CP LOCA analyses; Tillack volunteered to intercede, if needed.

High Heat Flux Components - UCSD is looking at a liquid metal HHF system to determine if various configurations would be applicable in the ST application.

Configuration and Maintenance - Mark Tillack mentioned that they are comparing several configuration options, especially trying to make a relative comparison between horizontal and vertical maintenance. One interesting option is to rotate the machine axis to a horizontal plane so that the (previous) vertical maintenance could be done cheaper and more efficiently in a horizontal plane.

Alternate Applications

Les Waganer summarized his efforts to develop an evaluation weighting scheme. Hopefully, this weighted set of criteria would allow the use of application attributes to provide a relative basis to judge the merits of the identified applications. As a preliminary test, several large public projects were used as a benchmark set to determine if the evaluation criteria would predict winners and losers. The first set of comparisons yielded results which reasonably matched history. This set of evaluation criteria will next be issued to the Alternate Applications group for further scrutiny.

Systems Studies

Ron Miller stated that his most recent work was documented in his ISFNT-4 paper. The cost goals of the competition continue to be lowered. Fission and other major electrical energy suppliers seem to be moving to larger plant sizes to help achieve economies of scale. New plants are now being considered in the range of 1500-1700 MWe.