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In transition: Commercializing fusion power
Commercial fusion power is closer than ever. There are now around 30 U.S. fusion companies, several of which claim to be on track to connect to the grid as early as the 2030s.
Tokamak and laser inertial confinement approaches benefit from decades of research at facilities such as the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory and ITER, with alternative concepts including stellarator, magnetic mirror, and Z-pinch confinement also making notable progress as private and government funding for fusion increases.
L. L. Briggs, W. F. Miller, Jr., E. E. Lewis
Nuclear Science and Engineering | Volume 57 | Number 3 | July 1975 | Pages 205-217
Technical Paper | doi.org/10.13182/NSE75-A26752
Articles are hosted by Taylor and Francis Online.
A generalization is made of a previous phase-space finite element approximation of the second-order form of the one-group, two-dimensional neutron transport equation in x-y geometry. Three angular approximations are formulated and compared: continuous piecewise bilinear finite element, piecewise constant finite element, and discrete ordinate. These are incorporated into a unified formalism of discrete ordinate-like equations, enabling the spatial variables to be treated identically using piecewise linear or bilinear finite elements. The resulting equations are solved iteratively by a weighted conjugate gradient method in an improved version of the computer code FENT. Numerical and analytical comparisons of the angular approximations are made, and it is found that both piecewise bilinear and piecewise constant approximations in angle substantially mitigate ray effects. The mitigation is shown to be associated closely with transformation of the hyperbolic discrete ordinate equations to the elliptic operators of the discrete ordinatelike finite element approximations. This transformation is accompanied by the disappearance of the characteristics along the discrete lines of neutron travel, and, hence, by the appearance of physically artificial derivative terms normal to the lines of neutron streaming. These terms grow with the subdomains of the angular finite elements.