Project Conference Call

6 February 1997


Participants:
(DOE) -
(UCSD) Mau, Miller, Najmabadi, Tillack, Wang
(PPPL) Dahlgren, Heitzenroeder, Jardin, Kessel, Reiersen
(GA) -
(UW) Blanchard, El-Guebaly, Khater, Sviatoslavsky
(FPA) -
(RPI) Steiner
(ANL) Sze
(MDA) Waganer

Administrative

Les Waganer took the roll call and reviewed the conference call agenda. Farrokh Najmabadi mentioned that the project goals remain essentially as noted in the December PPPL meeting. The investigation of special issues associated with the spherical tokamak is the main focus of the project, with a status update in the March meeting and a summary of results at mid year. We are using a non-optimized design point for comparative purposes. Main issues to be assessed are the MHD stability, startup requirements, centerpost engineering, and self-consistent design requirements/analyses. There is a small effort to define and categorize alternate fusion applications. Indications are that all groups are on track and on schedule. F. Najmabadi and M. Tillack are working on a more detailed project schedule to be posted on the project web site.

The planning for several related meetings scheduled for the first week of March 1997 were discussed:
-- Ron Miller noted that most of the submissions for the Japan/U.S. Reactor Workshop have been received. He will soon issue an agenda for the meeting which will take place at UCSD on 3-5 March. Any ARIES (LAR and RS) presentations will be scheduled on Wednesday to eliminate duplication. Any people interested in hearing those talks should plan on attending Wednesday. Ron solicited ARIES involvement to help beef up the ARIES session and the US participation.
-- Steve Jardin summarized the Innovative Concept Workshop to be held 3-6 March in Los Angeles. Both magnetic and inertial concepts are being discussed in oral and poster sessions. A session on advanced reactor concepts will be held on Wednesday.
-- F. Najmabadi mentioned that the ARIES meeting will be officially run Thursday through noon on Friday, with the aforementioned overlap with the Japan/US workshop on Wednesday. Jardin and Tillack will formulate sub-agendas for their areas, and Waganer will combine them into a project agenda. Meeting arrangements have already been started. (New project members should consult the ARIES Web site for the map and hotel facilities).
-- Don Steiner mentioned that the ISCUS meeting will be held on Tuesday in the San Diego area, but he has a conflict and will not be able to attend the project meeting. In his stead, Wayne Reiersen will make the presentation on the IBC engineering analyses.

Plasma Physics

Steve Jardin reported completion of a FE&D paper describing the recent ARIES-RS physics assessment. Chuck Kessel was largely responsible for assembling the paper, with support from TK Mau. There also was a meeting at PPPL discussing the LAR/ST physics analyses and results. The emphasis of the ARIES LAR/ST physics effort is to extend the equilibrium and vertical stability knowledge over an expanded range of aspect ratios and elongations. The reported contributions to date are largely those from PPPL - there has been no data or interaction with GA since the December meeting and they did not participate in the conference call. S. Jardin suggested increasing the use of technical papers to document the physics results in lieu of waiting for the publishing of project reports. Dave Ehst has two papers in work.

Engineering

FED papers - Mark Tillack stated that he has 7 of the 9 planned FE&D papers. He is on a fast track to publish the papers. All reviewers for the papers are lined up. Don Steiner agreed to help with an internal review prior to releasing to external reviewers.

General Engineering Comments - Mark Tillack mentioned the current intent is to examine engineering options for the LAR/ST and conduct investigations to determine limitations and possible solutions to high impact problems. Generally these areas are the centerpost, high heat flux components, and maintenance/configuration options.

Centerpost - Wayne Reiersen said that the centerpost design optimization code is being developed. He then highlighted some of the main features of the model. The engineering assumptions are the copper/water ratio, the layering of the centerpost components, the distribution from top to bottom, the cooling parameters, current densities, and resistivity assumptions. Fred Dahlgren discussed the thermohydraulic modeling, based upon a PPPL finite difference thermal code. The coolant conditions assume no boiling in the coolant passages. The dominant heating term is the ohmic heating (F. Dahlgren subsequently estimated around 2600-2900 MW for a 45 MA/m2 current density) with minimal nuclear heating. The March 1996 design point shall be used for system requirements. For the initial investigation, the centerpost should be considered as a constant cross-section from bottom to top. Don Steiner suggested obtaining a paper presented in Knoxville that had an intensive evaluation of a copper centerpost - those results could be used for comparison with the current results. This week UW will provide the radial distribution of the nuclear heating and the transmutation products in the CP to the PPPL group.

IBC Centerpost - Don Steiner noted that he and Wayne Reiersen are continuing to look at the design parameter space allowed by the IBC approach. The resistive losses are in the range of 300 MW, with 10% of that being in the outer return legs. The general configuration is an aspect ratio of 1.5, elongation of 2-2.5, and an on-axis field of 1.5-1.7 T. The next question is if the LAR/ST physics would be able to achieve 3000 MW with the IBC configuration? Don is hoping to be able to design a multiple-turn centerpost. He is also looking at a renewable insulating coating similar to the lithium/vanadium system.

Nuclear Aspects - Laila El-Guebaly and Hesham Khater has been working on the inboard shield, varying the constituents and the thickness to obtain a variable lifetime of the centerpost. The assumed wall load is in the range of 2-3 MW/m2, but for first order, the results are a function of the NWL. Laila is working with PPPL to help refine the nuclear parameters in their design code.

First Wall/Blanket and Thermal Conversion - Dai-Kai Sze is working on the FWB design approach presented at the December PPPL project meeting. This design uses high temperature helium in the blanket to achieve thermal conversion efficiencies in the range of 60% (excluding centerpost, shielding, and divertor heat recovery systems). The preferred divertor concept is not yet established, which complicates the definition of the heat recovery system. Liquid lithium divertors were proposed, but Dai-Kai said that they were effective hydrogen getters, which would significantly decrease the tritium burnup fraction and increase the throughput. The proposed water cooling solutions of the centerpost are not conducive to high efficiency thermal conversion processes.

High Heat Flux Components - Mark Tillack mentioned that they are using a goal requirement of 5 MW/m2 surface heat removal for steady-state, energy-producing thermal conditions There have been helium systems reported that obtained 10 MW/m2, but they are using small components and low temperature coolants. Copper/water systems can do even better but they are not amenable to power producing conditions. Vanadium is being considered as the structural material of choice at this point. The vanadium structure can be cooled by high pressure helium.

Alternate Applications

Les Waganer reviewed the project plan to survey and examine alternate fusion applications. The level of effort is minimal during the first part of the year as the alternate applications are assessed. Waganer will concentrate on the collection and organization of the material while the volunteers (El-Guebaly, Miller, Najmabadi, Steiner, Sviatoslavsky, Tillack, and Wong) collect alternate applications. Waganer has prepared a study plan to determine the attribute parameter set, survey the applications, establish a parameter weighting scheme, and catalog the application attributes. An initial status will be presented at the March meeting.

Systems Studies

Ron Miller confirmed that the systems code has been transferred to UCSD under his tutorship. Chuck Bathke is assisting in the transfer, but he has minimal effort remaining. Ron did provide to Laila an inboard and outboard average NWL distribution for the 1.25 LAR. He noted that a prior version of the IBC centerpost is still in the model, but it has not been updated or verified recently.