Magnetic Fusion Energy Development Research Articles

A Strategic Opportunity for Magnetic Fusion Energy Development

The realities of energy development and the perception of and support for magnetic fusion in the US are briefly summarized as background for proposing a strategic opportunity for magnet fusion energy development as fusion neutron sources for subcritical advanced burner (transmutation) reactors for the destruction of long-lived transuranics in spent nuclear fuel.

The relation between upstream density and temperature widths in the scrape-off layer and the power width in an attached divertor

The target power width is one of the most critical practical quantities in the development of magnetic fusion energy. It is essential to know how to scale this quantity to future devices. At present the controlling physics is not adequately understood, making reliable prediction difficult. It seems likely that two important processes effecting are (a) cross-field transport, e.g. D⊥, and (b) volumetric power loss processes in the edge plasma, with the latter tending to occur mainly in the divertor for attached divertor conditions. It is hypothesized that a simple relation exists between the ‘upstream’ radial profiles of ne and Te in the main scrape-off layer, , , and the parallel power flux density at the divertor entrance, . Such a simple relation is found here in 2D SOLPS edge code simulations of attached divertor conditions, which contain a wide range of more or less complex edge physics effects. It is found that , as can be expected on the basis of flux-limited parallel heat conduction, rather than Spitzer–Harm conduction for which is expected. For the relatively open divertor configuration considered, and for attached divertor conditions, it is found that the flux-limited relationship also holds for the SOLPS power flux density deposited on the target , even including the radiation load; this despite the fact that up to half the power into the SOL is dissipated radiatively. Comparing with experimentally measured target power widths for H-mode discharges, better agreement is found assuming flux limited rather than Spitzer–Harm transport although definitive conclusions will require analysis of specific discharges in specific tokamaks. This study is a necessary preliminary work to an equivalent treatment of the case where volumetric losses in the divertor are stronger, including the detached, strongly radiating divertor case with momentum loss.

DIII-D research program

The DIII-D tokamak is uniquely positioned to contribute to the development of Magnetic Fusion Energy over the next decade. Recent stability and confinement improvements resulting from current profile control and the discovery of the VH-mode stress the importance of non-inductive current drive. The DIII-D program plan calls for the implementation of high rf systems for such profile control; localized heating and current drive for improved to tokamak performance and advancing divertor research under current drive conditions. Funding levels will determine the potential impact of this $400 M research facility by determining the pace for implementation of rf and divertor upgrades as well as determining the amount of experimental operating time. A strong DIII-D program can effectively address the R&D issues of next generation tokamaks and allow the large number of DIII-D collaborators to explore new ideas to advance the tokamak to a commercially attractive energy option.

U.S. Strategy for International Collaboration on Magnetic Fusion Energy Development—A Technological and Scientific View

The opportunities for international collaboration in fusion are discussed within the context of the present status of fusion development and international research and development activities. A spe...

Decision Analysis of Program Choices in Magnetic Fusion Energy Development

This paper describes a methodology based on decision analysis for addressing major program decisions in the development of magnetic fusion energy. The development of this complex technology involves a sequence of funding choices over time among multiple technical approaches and under considerable performance uncertainty. The methodology focuses on the next major facility decision in the U.S magnetic fusion energy program. The decision alternatives include the construction and testing of a major experimental facility based on one of two leading technical approaches (reactor designs), an accelerated program where both approaches are pursued, or delaying another facility until more information is available. Subsequent decisions depend on the first decision and its outcome and involve either further development of the best technical approach or abandonment of the entire research and development program. Analysis of a particular sequence of program decisions takes account of the uncertainties in the ultimate economic performance (cents per kilowatt-hour) of the resulting commercial reactor, the time of commercial availability, and market penetration. Reactor performance is analyzed at a component level and explicitly considers the dependence of component performances based on one technical approach on the respective component performances of alternative approaches. The net benefits of magnetic fusion R&D are assessed by computing the discounted expected cost savings attributable to commercial magnetic fusion energy minus the discounted costs of the R&D program.