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June 14–16, 2021
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Federal subsidies for nuclear plants?
The Biden administration has indicated to lawmakers that it supports federal subsidies for struggling nuclear power plants, Reuters reported this morning, citing sources familiar with the discussions.
The subsidies would be in the form of production tax credits, according to the report, and would likely become part of the president’s $2.3 trillion infrastructure plan.
B. S. Southworth, Milan Holec, T. S. Haut
Nuclear Science and Engineering | Volume 195 | Number 2 | February 2021 | Pages 119-136
Technical Paper | dx.doi.org/10.1080/00295639.2020.1799603
Articles are hosted by Taylor and Francis Online.
A standard approach to solving the S transport equations is to use source iteration with diffusion synthetic acceleration (DSA). Although this approach is widely used and effective on many problems, there remain some practical issues with DSA preconditioning, particularly on highly heterogeneous domains. For large-scale parallel simulation, it is critical that both (a) preconditioned source iteration converges rapidly and (b) the action of the DSA preconditioner can be applied using fast, scalable solvers, such as algebraic multigrid (AMG). For heterogeneous domains, these two interests can be at odds. In particular, there exist DSA diffusion discretizations that can be solved rapidly using AMG, but they do not always yield robust/fast convergence of the larger source iteration. Conversely, there exist robust DSA discretizations where source iteration converges rapidly on difficult heterogeneous problems, but fast parallel solvers like AMG tend to struggle applying the action of such operators. Moreover, very few current methods for the solution of deterministic transport are compatible with voids. This paper develops a new heterogeneous DSA preconditioner based on only preconditioning the optically thick subdomains. The resulting method proves robust on a variety of heterogeneous transport problems, including a linearized hohlraum mesh related to inertial confinement fusion. Moreover, the action of the preconditioner is easily computed using AMG iterations, convergence of the transport iteration typically requires 2 to 5× fewer iterations than current state-of-the-art “full” DSA, and the proposed method is trivially compatible with voids. On the hohlraum problem, rapid convergence is obtained by preconditioning less than 3% of the mesh elements with five to ten AMG iterations.