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Fusion Energy
This division promotes the development and timely introduction of fusion energy as a sustainable energy source with favorable economic, environmental, and safety attributes. The division cooperates with other organizations on common issues of multidisciplinary fusion science and technology, conducts professional meetings, and disseminates technical information in support of these goals. Members focus on the assessment and resolution of critical developmental issues for practical fusion energy applications.
Meeting Spotlight
Conference on Nuclear Training and Education: A Biennial International Forum (CONTE 2025)
February 3–6, 2025
Amelia Island, FL|Omni Amelia Island Resort
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The Standards Committee is responsible for the development and maintenance of voluntary consensus standards that address the design, analysis, and operation of components, systems, and facilities related to the application of nuclear science and technology. Find out What’s New, check out the Standards Store, or Get Involved today!
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Latest News
Senate committee hears from energy secretary nominee Chris Wright
Chris Wright, president-elect Trump’s pick to lead the U.S. Department of Energy, spent hours today fielding questions from members of the U.S. Senate’s committee on Energy and Natural Resources.
During the hearing, Wright—who’s spent most of his career in fossil fuels—made comments in support of nuclear energy and efforts to expand domestic generation in the near future. Asked what actions he would take as energy secretary to improve the development and deployment of SMRs, Wright said: “It’s a big challenge, and I’m new to government, so I can’t list off the five levers I can pull. But (I’ve been in discussions) about how to make it easier to research, to invest, to build things. The DOE has land at some of its facilities that can be helpful in this regard.”
M. M. R. Williams
Nuclear Science and Engineering | Volume 146 | Number 2 | February 2004 | Pages 152-175
Technical Paper | doi.org/10.13182/NSE04-A2400
Articles are hosted by Taylor and Francis Online.
The classic minimum critical mass problem, posed and solved by Goertzel using multigroup diffusion theory, is revisited and reformulated in terms of the two-group transport equation with isotropic scattering. A new variational principle is constructed from which it is possible to derive the conditions necessary for a minimum critical mass. This condition is that the angular thermal flux t([bold]r, [bold]) and a quantity t([bold]r, [bold]) related to the adjoint flux, must obey the constraint[integral]dt([bold]r, [bold])t([bold]r, [bold]) = constant.Contrary to the behavior noted in diffusion theory, this condition does not correspond to a flat thermal flux in the core. This is a major conclusion of the present work.To find the associated solutions, we develop a coupled set of integral equations for the components of the angular flux in the core. We then show that, for weakly absorbing moderators, the lowest order approximation to this set provides an accurate representation of the minimum mass conditions. It also emerges that the flat flux is a very good representation of the true flux. With the above assumptions, the problem reduces to that of solving a Fredholm equation of the first kind for the fuel mass distribution across the core. We solve this equation numerically for the case of an infinitely reflected, infinite slab and compare the results with those from diffusion theory. The transport theory results show one very interesting and important feature, namely, a steep rise in fuel concentration as the boundary is approached which goes to infinity at the boundary. This is in contrast to the diffusion theory result which requires an ad hoc addition of surface delta functions for a solution to exist. Thus we come to the conclusion that the increased surface concentration of fuel is a natural consequence of transport theory but not of diffusion theory. This is the second major conclusion of this work. Detailed numerical results are presented for 235U-graphite and 235U-water mixtures.
