Original scientific paper
Monte Carlo Codes for Neutron Buildup Factors
Krešimir Trontl
; University of Zagreb, Faculty of Electrical Engineering and Computing Unska 3, 10000 Zagreb, Croatia
Dubravko Pevec
; University of Zagreb, Faculty of Electrical Engineering and Computing Unska 3, 10000 Zagreb, Croatia
Mario Matijević Matijević
; University of Zagreb, Faculty of Electrical Engineering and Computing Unska 3, 10000 Zagreb, Croatia
Abstract
The point-kernel method is a widely used practical tool for gamma-ray shielding calculations.
However, application of that method for neutron transport simulations is very limited. The accuracy
of the method strongly depends on the accuracy of buildup factors used in the calculations. Buildup
factors are usually obtained using appropriate computer codes, either based on discrete ordinates
transport method or Monte Carlo approach. Since these codes put strong demands on computer
resources, they are applied on a limited number of shielding configurations and an attempt is made
to use these results and formulate an empirical expression for buildup factors estimation. Due to
high physical complexity of neutron transport through shielding material it is very hard to perform
parameterisation in order to establish adequate empirical formula. Existing formulas are very
limited and are usually applicable to a narrow neutron energy range for few commonly used
shielding materials, mostly in monolayer configuration.
Recently, a new approach has been proposed for determination of gamma ray buildup factors
for mono-layer, as well as multi-layer shielding configurations covering a wide gamma ray energy
range. The new regression model is based on support vector machines learning technique, which
has theoretical background in statistical learning theory. Development of named regression model
required a large number of experimental data obtained by Monte Carlo computer code. More than
7000 Monte Carlo runs were required. Due to physical complexity neutron transport is likely to
require even more experimental data in order to generate a model of reasonable accuracy.
Therefore, the choice of appropriate Monte Carlo code is a very important question. One has to take
into account the accuracy as well as the time required for input preparation and running the code.
What also has to be considered is the possibility of the code to be incorporated in an algorithm for
automated generation of experimental data.
In this paper three Monte Carlo codes are analysed, namely SCALE4.4 code package (SAS3
sequence), SCALE6.0 code package (MAVRIC sequence), and MCNP5. Two simple experimental
setups based on a point isotropic source in spherical and slab-like shield are modelled, and the
codes are examined on previously mentioned issues.
The comparison results show that each one of the examined codes has potential to be used for
neutron buildup factor model generation. However, some aspects of their utilization require further
analysis prior to final selection.
Keywords
Hrčak ID:
199055
URI
Publication date:
31.7.2017.
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