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2024 ANS Winter Conference and Expo
November 17–21, 2024
Orlando, FL|Renaissance Orlando at SeaWorld
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NRC okays construction permits for Hermes 2 test facility
The Nuclear Regulatory Commission announced yesterday that it has directed staff to issue construction permits to Kairos Power for the company's proposed Hermes 2 nonpower test reactor facility to be built at the Heritage Center Industrial Park in Oak Ridge, Tenn. The permits authorize Kairos to build a facility with two 35-MWt test reactors that would use molten salt to cool the reactor cores.
Ben C. Yee, Brendan Kochunas, Edward W. Larsen
Nuclear Science and Engineering | Volume 193 | Number 7 | July 2019 | Pages 722-745
Technical Paper | doi.org/10.1080/00295639.2018.1562777
Articles are hosted by Taylor and Francis Online.
The Multilevel in Space and Energy Diffusion (MSED) method accelerates the iterative convergence of multigroup diffusion eigenvalue problems by performing work on lower-order equations with only one group and/or coarser spatial grids. It consists of two primary components: (1) a grey (one-group) diffusion eigenvalue problem that is solved via Wielandt-shifted power iteration (PI) and (2) a multigrid-in-space linear solver. In previous work, the efficiency of MSED was verified using Fourier analysis and numerical results from a one-dimensional multigroup diffusion code. Since that work, MSED has been implemented as a solver for the coarse-mesh finite difference (CMFD) system in the three-dimensional Michigan Parallel Characteristics Transport (MPACT) code. In this paper, the results from the implementation of MSED in MPACT are presented, and the changes needed to make MSED more suitable for MPACT are described. For problems without feedback, the results in this paper show that MSED can reduce the CMFD run time by an order of magnitude and the overall run time by a factor of 2 to 3 compared to the default CMFD solver in MPACT [PI with the generalized minimal residual (GMRES) method]. For problems with feedback, the convergence of the outer Picard iteration scheme is worsened by the well-converged CMFD solutions produced by the standard MSED method. To overcome this unintuitive deficiency, MSED may be run with looser convergence criteria (a modified version of the MSED method called MSED-L) to circumvent the issue until the multiphysics iteration in MPACT is improved. Results show that MSED-L can reduce the CMFD run time in MPACT by an order of magnitude, without negatively impacting the outer Picard iteration scheme.
