Skip to main content
U.S. Department of Energy
Office of Scientific and Technical Information

Calculating Alpha Eigenvalues and Eigenfunctions with a Markov Transition Rate Matrix Monte Carlo Method

Journal Article · · Nuclear Science and Engineering
 [1];  [2];  [2];  [3]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Univ. of Michigan, Ann Arbor, MI (United States)
  3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
For a nuclear system in which the entire α-eigenvalue spectrum is known, eigenfunction expansion yields the time-dependent flux response to any arbitrary source. Applications in which this response is of interest include pulsed-neutron experiments, accelerator-driven subcritical systems, and fast burst reactors, where a steady-state assumption used in neutron transport is invalid for characterizing the time-dependent flux. To obtain the α-eigenvalue spectrum, the transition rate matrix method (TRMM) tallies transition rates describing neutron behavior in a discretized position-direction-energy phase space using Monte Carlo. Interpretation of the resulting Markov process transition rate matrix as the operator in the adjoint α-eigenvalue problem provides an avenue for determining a large finite set of α eigenvalues and eigenfunctions of a nuclear system. Results from the TRMM are verified using analytic solutions, time-dependent Monte Carlo simulations, and modal expansion from diffusion theory. For simplified infinite-medium and one-dimensional geometries, the TRMM accurately calculates eigenvalues, eigenfunctions, and eigenfunction expansion solutions. Applications and comparisons to measurements are made for the small fast burst reactor CALIBAN and the Fort St. Vrain high-temperature gas-cooled reactor. For large three-dimensional geometries, discretization of the large position-energy-direction phase space limits the accuracy of eigenfunction expansion solutions using the TRMM, but it can still generate a fair estimate of the fundamental eigenvalue and eigenfunction. These results show that the TRMM generates an accurate estimate of a large number of α eigenvalues. This is not possible with existing Monte Carlo–based methods.
Research Organization:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Organization:
USDOE
Grant/Contract Number:
AC05-00OR22725
OSTI ID:
1492187
Journal Information:
Nuclear Science and Engineering, Journal Name: Nuclear Science and Engineering Journal Issue: 2 Vol. 192; ISSN 0029-5639
Publisher:
American Nuclear Society - Taylor & FrancisCopyright Statement
Country of Publication:
United States
Language:
English

References (24)

On the spectrum of an unsymmetric operator arising in the transport theory of neutrons journal May 1955
An asymptotic expansion in the theory of neutron transport journal May 1958
Diffusion theory methods for spatial kinetics calculations journal January 1996
Asymptotic solutions of the transport equation for thermal neutrons journal April 1963
A simple scheme for the direct evaluation of time-eigenvalues of neutron transport equation journal January 2003
Iterative computation of time-eigenvalues of the neutron transport equation journal November 2003
Time–eigenvalue calculations in multi-region Cartesian geometry using Green’s functions journal June 2005
Pulsed neutron source measurements in the subcritical ADS experiment YALINA-Booster journal December 2008
Monte Carlo simulation and benchmarking of pulsed neutron experiments in variable buckling Beo systems journal May 2009
Iterative method for obtaining the prompt and delayed alpha-modes of the diffusion equation journal September 2011
Three-dimensional transport calculation of multiple alpha modes in subcritical systems journal December 2012
ENDF/B-VII.0: Next Generation Evaluated Nuclear Data Library for Nuclear Science and Technology journal December 2006
Calculating infinite-medium α-eigenvalue spectra with Monte Carlo using a transition rate matrix method journal December 2015
On the spectrum of the linear transport operator journal November 1974
Calculating α Eigenvalues of One-Dimensional Media with Monte Carlo journal July 2014
Numerical Linear Algebra book January 1997
LAPACK Users' Guide software January 1999
ARPACK Users' Guide book January 1998
the slab geometry journal March 1956
Time-Dependent, One-Speed Transport via Generalized Functions journal March 2001
Numerical Solution of the Time-Dependent Multigroup Diffusion Equations journal February 1968
On the Relation between Decay Constants and Critical Parameters in Monoenergetic Neutron Transport journal March 1983
Two Rossi- α Techniques for Measuring the Effective Delayed Neutron Fraction journal February 1993
Higher Order αMode Eigenvalue Calculation by Monte Carlo Power Iteration journal January 2011

Cited By (3)


Similar Records

α-weighted Transition Rate Matrix Method
Conference · Thu Aug 01 00:00:00 EDT 2019 · OSTI ID:1559649

Calculating infinite-medium α-eigenvalue spectra with Monte Carlo using a transition rate matrix method
Journal Article · Thu Aug 27 20:00:00 EDT 2015 · Nuclear Engineering and Design · OSTI ID:1223665

Calculating infinite-medium {alpha}-eigenvalue spectra with a transition rate matrix method
Conference · Mon Jul 01 00:00:00 EDT 2013 · OSTI ID:22212917