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Updated: Dec 26, 2025
10:24
Neutron Radiography and Computed Tomography of Biological Systems at the Oak Ridge National Laboratory's High Flux Isotope Reactor
Published on: May 7, 2021
2.7K
Nedis-Serpent simulation of a neutron source assembly with complex internal heterogeneous structure.
Sergey V Bedenko1, Gennady N Vlaskin2, Nima Ghal-Eh3
1School of Nuclear Science and Engineering, Tomsk Polytechnic University, Tomsk, Russia.
Summary
Grain size in americium-beryllium (Am-Be) neutron sources significantly impacts radiation characteristics. Fine grains reduce neutron yield and soften the spectrum, while AmBe13 offers higher yields.
Area of Science:
- Nuclear Engineering
- Materials Science
- Radiation Physics
Background:
- Neutron sources are critical for various applications, including material irradiation and diagnostics.
- Americium-beryllium (Am-Be) sources are widely used due to their relatively high neutron yield and long half-life.
- Understanding the influence of source material composition and structure on neutron emission is crucial for optimizing source performance and applications.
Purpose of the Study:
- To investigate the effect of grain size in Am-Be neutron sources on neutron yield and energy spectrum.
- To compare the performance of different Am-Be core materials, including americium dioxide (AmO2) and AmBe13.
- To propose and analyze a novel heterogeneous Am-Be source design for variable neutron yield and specific spectral characteristics.
Main Methods:
- Monte Carlo simulations using Nedis-2m and Serpent 2.1.30 codes.
- Modeling of Am-Be sources with varying core compositions (AmO2, AmBe13) and grain structures.
- Simulation of a heterogeneous Am-Be source with AmO2 rods embedded in beryllium.
- Analysis of neutron yield and energy spectrum for each simulated configuration.
Main Results:
- Fine-grained AmO2 cores result in reduced neutron yield and a softer neutron energy spectrum due to fewer alpha particle interactions.
- AmBe13 intermetallic alloy cores demonstrate a potential increase in neutron yield by up to 50% compared to AmO2 cores.
- The heterogeneous Am-Be source design exhibits a neutron energy spectrum similar to Deuterium-Tritium (D-T) neutrons and allows for variable neutron yield.
- The heterogeneous design offers simplified handling and operational procedures for irradiation facilities.
Conclusions:
- Source core microstructure significantly influences Am-Be neutron emission characteristics.
- AmBe13 offers superior neutron yield potential compared to AmO2.
- The proposed heterogeneous Am-Be source is a promising design for tunable neutron irradiation applications, mimicking D-T neutron spectra.
- This design facilitates the development of subcritical irradiation facilities for studying materials in epithermal and fast neutron environments.
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