FIAS Scientific Report 2011 - Frankfurt Institute for Advanced Studies ...

Monte Carlo modeling of neutron production and transport in spallation targets
Collaborators: Yury Malyshkin, Igor Pshenichnov, Igor Mishustin, Walter Greiner
We study neutron production by energetic protons in extended targets made of non-fissile (e.g. tungsten) and
fissile materials (e.g. uranium). Produced neutrons can be used to maintain nuclear fission reactions in a subcritical
assembly of an accelerator-driven system (ADS) designed for nuclear waste incineration. A dedicated
software called MCADS (Monte Carlo for Accelerator-Driven Systems) was created in FIAS. MCADS is based
on the Geant4 toolkit, which is widely employed in basic research to model propagation of particles and nuclei
in extended media. The spatial distributions of neutron flux and energy deposition in the spallation target
are calculated with MCADS. The even-by-event MC simulations are very useful to account for a large veriety
of processes induced in the target. A history of a single 600 MeV beam proton and all secondary particles
produced in a monolithic uranium target of a cylindrical shape is shown in Fig. 1 as an example.
The detailed spatial distribution of neutron flux is crucial for an ADS design process. In Fig. 2 the spatial
distribution of neutron flux from 10 mA 600 MeV proton beam is shown for the uranium target . The average
value of neutron flux over the whole target volume is 6.2 · 10 15 n/(cm 2 s), while the highest flux value of
2.5 · 10 16 n/(cm 2 s) is found on the beam axis at 5 cm depth.
proton
beam
Figure 1: History of a single 600 MeV
proton which hits a uranium target. Green
– neutrons, yellow – gammas.
R (cm)
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n/s/cm
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Z (cm)
Figure 2: Spatial distribution of neutron flux inside the uranium target.
Our alculations show that by using uranium target one can obtain the same neutron yield with only 38% of the
beam current needed for a non-fissile target made of tungsten. In this case the total heat deposition in fissile
and non-fissile targets are similar too.
Related publications and talks in 2011:
1) Y. Malyshkin, I. Pshenichnov, I. Mishustin, W. Greiner, Modeling spallation reactions in tungsten and
uranium targets with the Geant4 toolkit, Poster at 3rd International Workshop on Compound Nuclear Reactions
and Related Topics, published on-line: EPJ Web of Conferences 21, 10006 (2012).
2) Yury Malyshkin, Igor Pshenichnov, Igor Mishustin, Timothy Hughes, Oliver Heid, Walter Greiner, Monte
Carlo modeling of neutron production and energy deposition in fissile spallation targets, to be published in
NIMB.
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