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Advanced Variance Reduction for Global k-Eigenvalue Simulations in MCNP

Description: The "criticality" or k-eigenvalue of a nuclear system determines whether the system is critical (k=1), or the extent to which it is subcritical (k<1) or supercritical (k>1). Calculations of k are frequently performed at nuclear facilities to determine the criticality of nuclear reactor cores, spent nuclear fuel storage casks, and other fissile systems. These calculations can be expensive, and current Monte Carlo methods have certain well-known deficiencies. In this project, we have developed an… more
Date: June 1, 2008
Creator: Larsen, Edward W.
Partner: UNT Libraries Government Documents Department
open access

A New 2D-Transport, 1D-Diffusion Approximation of the Boltzmann Transport equation

Description: The work performed in this project consisted of the derivation, implementation, and testing of a new, computationally advantageous approximation to the 3D Boltz- mann transport equation. The solution of the Boltzmann equation is the neutron flux in nuclear reactor cores and shields, but solving this equation is difficult and costly. The new “2D/1D” approximation takes advantage of a special geometric feature of typical 3D reactors to approximate the neutron transport physics in a specific (ax- … more
Date: June 17, 2013
Creator: Larsen, Edward
Partner: UNT Libraries Government Documents Department
open access

The Suppression of Energy Discretization Errors in Multigroup Transport Calculations

Description: The Objective of this project is to develop, implement, and test new deterministric methods to solve, as efficiently as possible, multigroup neutron transport problems having an extremely large number of groups. Our approach was to (i) use the standard CMFD method to "coarsen" the space-angle grid, yielding a multigroup diffusion equation, and (ii) use a new multigrid-in-space-and-energy technique to efficiently solve the multigroup diffusion problem. The overall strategy of (i) how to coarsen … more
Date: June 17, 2013
Creator: Larsen, Edward
Partner: UNT Libraries Government Documents Department
open access

Radial Moment Calculations of Coupled Electron-Photon Beams

Description: The authors consider the steady-state transport of normally incident pencil beams of radiation in slabs of material. A method has been developed for determining the exact radial moments of 3-D beams of radiation as a function of depth into the slab, by solving systems of 1-D transport equations. They implement these radial moment equations in the ONEBFP discrete ordinates code and simulate energy-dependent, coupled electron-photon beams using CEPXS-generated cross sections. Modified P{sub N} sy… more
Date: July 19, 2000
Creator: Franke, Brian C. & Larsen, Edward W.
Partner: UNT Libraries Government Documents Department
open access

Stretched and Filtered Transport Synthetic Acceleration of Sn Problems: Part 1: Homogeneous Media

Description: The authors present a new method for fast transport synthetic acceleration (TSA) of source iterations for S{sub N} problems, using a pure absorber problem stretched to have a mean free path comparable to a diffusion length. The resulting scheme is at first glance unstable, with a large negative eigenvalue at high spatial frequencies, but it can be made effective using (i) a low-pass filter, (ii) a Krylov method, or both. The stretched error correction and the filter are implemented with the sam… more
Date: November 16, 2003
Creator: Hanshaw, Heath L; Nowak, Paul & Larsen, Edward W
Partner: UNT Libraries Government Documents Department
open access

Asymptotic derivation of the simplified P[sub n] equations

Description: The diffusion and simplified P[sub N] equations are derived from the transport equation by means of an asymptotic expansion in which the diffusion equation is the leading order approximation and the simplified P[sub N] equations are higher-order approximations. In addition, the simplified P[sub N] equations are reformulated in a canonical'' form that greatly facilitates the formulation of boundary conditions and the implementation of the resulting problem in a conventional multigroup diffusion … more
Date: January 1, 1993
Creator: Larsen, Edward W.; Morel, Jim E. & McGhee, John M.
Partner: UNT Libraries Government Documents Department
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