Argonne National Laboratory
Monte Carlo Neutron/Photon Transport Code
Nuclear Engineering is a Division of Argonne National Laboratory (Argonne), a U.S. Department of Energy laboratory managed by UChicago Argonne, LLC

.:: ANL Nuclear Criticality Safety Program ::.

Welcome to the VIM Computer Code web site

General Description

VIM is a continuous-energy criticality, reactor physics, and shielding code developed and maintained in the Nuclear Engineering Division of Argonne National Laboratory with the support of the U. S. Department of Energy. It solves the transport problem for neutrons or photons, includes thermal neutron scattering effects, either in the eigenvalue mode or for photon or neutron fixed source. VIM features flexible geometricy and neutron physics data carefully constructed from ENDF/B and JEF data Special neutron physics capabilities in VIM include unresolved resonance probability tables, and direct treatment of resolved resonances described with Reich-Moore parameters. It has been extensively benchmarked, using both experiments and other accurate codes.

VIM is available through the Radiation Safety Information Computational Center at Oak Ridge National Laboratory.

VIM in the DOE Nuclear Criticality Safety Program

VIM is one of the three general purpose Monte Carlo criticality codes used for analyzing the criticality state of fissile systems in the Department of Energy nuclear complex. The Department relies on three distinct codes in order to avoid common mode failures in analysis, thereby permitting more robust analysis of nuclear systems through code diversity and inter-code comparisons. See the US DOE Nuclear Criticality Safety Program or the DOE HQ Nuclear Criticality Safety Web Site.

VIM is also a testbed for DOE's studies of Monte Carlo source convergence problems that can arise with loosely coupled systems. Slow convergence (or non-convergence) can be insidious because the analyst might see no evidence of a convergence problem, and the apparently precise eigenvalue is non-conservative. A stratified sampling method that improves the robustness of Monte Carlo source convergence has undergone preliminary testing in a developmental version of VIM. VIM is being applied to the convergence benchmarks under study by the OECD/NEA Expert Group on Source Convergence in Criticality Safety Analysis.

VIM has been used in a variety of ICSBEP criticality safety benchmarks, e.g., the U/Fe Benchmark Assembly (a high-leakage core very sensitive to the treatment of scattering in iron, HEU-MET-FAST-035), the U9 Benchmark Assembly (an intermediate-enriched uranium core reflected with DU, sensitive to the U-235 and U-238 data, IEU-MET-FAST-010), a Be-reflected HEU system (HEU-MET-FAST-041), U233-SOL-THERM-005, and PU-MIXED-COMP-012. In addition, direct, point-by-energy-point comparisons between the MCNP libraries and the independently processed VIM libraries are made to detect processing errors and algorithm issues.

Roger N. Blomquist
Criticality Safety Section
Nuclear Engineering Division
Argonne National Laboratory
9700 South Cass Avenue
Argonne, Illinois 60439

Fax:  +1 630-252-4500

VIM Site Index

ARGONNE NATIONAL LABORATORY, Nuclear Engineering Division
9700 South Cass Ave., Argonne, IL 60439-4814
A U.S. Department of Energy laboratory managed by UChicago Argonne, LLC

Last modified on March 03, 2009 15:11 +0100