Monte Carlo calculations and neutron spectrometry in quantitative prompt gamma neutron activation analysis (PGNAA) of bulk samples using an isotopic neutron source |
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Authors: | N M Spyrou J B Awotwi-Pratt A M Williams |
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Institution: | (1) Centre for Nuclear and Radiation Physics, Department of Physics, University of Surrey Guildford, Surrey, GU2 7XH, UK |
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Abstract: | An activation analysis facility based on an isotopic neutron source (185 GBq 241Am/Be) which can perform both prompt and cyclic activation analysis on bulk samples, has been used for more than 20 years
in many applications including 'in vivo' activation analysis and the determination of the composition of bio-environmental
samples, such as, landfill waste and coal. Although the comparator method is often employed, because of the variety in shape,
size and elemental composition of these bulk samples, it is often difficult and time consuming to construct appropriate comparator
samples for reference. One of the obvious problems is the distribution and energy of the neutron flux in these bulk and comparator
samples. In recent years, we have attempted to adopt the absolute method based on a monostandard and to make calculations
using a Monte Carlo code (MCNP4C2) to explore this further. In particular, a model of the irradiation facility has been made
using the MCNP4C2 code in order to investigate the factors contributing to the quantitative determination of the elemental
concentrations through prompt gamma neutron activation analysis (PGNAA) and most importantly, to estimate how the neutron
energy spectrum and neutron dose vary with penetration depth into the sample. This simulation is compared against the scattered
and transmitted neutron energy spectra that are experimentally and empirically determined using a portable neutron spectrometry
system.
This revised version was published online in August 2006 with corrections to the Cover Date. |
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