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The busyness of the nuclear fuel supply chain
Ken Petersenpresident@ans.org
With all that is happening in the industry these days, the nuclear fuel supply chain is still a hot topic. The Russian assault in Ukraine continues to upend the “where” and “how” of attaining nuclear fuel—and it has also motivated U.S. legislators to act.
Two years into the Russian war with Ukraine, things are different. The Inflation Reduction Act was passed in 2022, authorizing $700 million in funding to support production of high-assay low-enriched uranium in the United States. Meanwhile, the Department of Energy this January issued a $500 million request for proposals to stimulate new HALEU production. The Emergency National Security Supplemental Appropriations Act of 2024 includes $2.7 billion in funding for new uranium enrichment production. This funding was diverted from the Civil Nuclear Credits program and will only be released if there is a ban on importing Russian uranium into the United States—which could happen by the time this column is published, as legislation that bans Russian uranium has passed the House as of this writing and is headed for the Senate. Also being considered is legislation that would sanction Russian uranium. Alternatively, the Biden-Harris administration may choose to ban Russian uranium without legislation in order to obtain access to the $2.7 billion in funding.
Marvin L. Adams, Todd A. Wareing, Wallace F. Walters
Nuclear Science and Engineering | Volume 130 | Number 1 | September 1998 | Pages 18-46
Technical Paper | doi.org/10.13182/NSE98-A1987
Articles are hosted by Taylor and Francis Online.
The performance of characteristic methods (CMs) on problems that contain optically thick diffusive regions is analyzed and tested. The asymptotic analysis holds for moment-based characteristics methods that are algebraically linear; for one-, two-, and three-dimensional Cartesian coordinate systems; and for arbitrary spatial grids composed of polygons (two dimensions) or polyhedra (three dimensions). The analysis produces a theory that predicts and explains how CMs behave when applied to thick diffusive problems. The theory predicts that as spatial cells become optically thick and highly scattering, CMs behave almost exactly like discontinuous finite element methods (DFEMs). This means that there are two classes of CMs: those that fail dramatically on thick diffusive problems and those whose solutions satisfy discretizations of the correct diffusion equation. Most CMs in the latter set behave poorly in general, sometimes producing oscillatory and negative solutions in thick diffusive regions. However, the analysis suggests that certain reduced-order CMs, which use less information on cell surfaces than is readily available, will behave more robustly in thick diffusive regions. The predictions regarding standard CMs are tested by using the linear and bilinear characteristics methods on several test problems with rectangular grids in x-y geometry. The predictions regarding reduced-order CMs are tested by solving x-y test problems on triangular grids using a CM that employs linear functions for cell-interior sources but constants for cell-surface fluxes. In every case the numerical results agree precisely with the predictions of the theory.