5 research outputs found
Impact of crystallite size on the performance of a beryllium reflector
Beryllium reflectors are used at spallation neutron sources in order to
enhance the low-energy flux of neutrons emanating from the surface of a cold
and thermal moderator. The design of such a moderator/reflector system is
typically carried out using detailed Monte-Carlo simulations, where the
beryllium reflector is assumed to behave as a poly-crystalline material. In
reality, however, inhomogeneities in the beryllium could lead to discrepancies
between the performance of the actual system when compared to the modeled
system. The dependence of the total cross section in particular on crystallite
size, in the Bragg scattering region, could influence the reflector
performance, and if such effect is significant, it should be taken into account
in the design of the moderator/reflector system. In this paper, we report on
the preliminary results of using cross-section libraries, which include
corrections for the crystallite size effect, in spallation source neutronics
calculations.Comment: ICANS-XXII
Impact of crystallite size on the performance of a beryllium reflector
Beryllium reflectors are used at spallation neutron sources in order to enhance the low-energy flux of neutrons emanating from the surface of a cold and thermal moderator. The design of such a moderator/reflector system is typically carried out using detailed Monte-Carlo simulations, where the beryllium reflector is assumed to behave as a poly-crystalline material. In reality, however, inhomogeneities in the beryllium could lead to discrepancies between the performance of the actual system when compared to the modeled system. The dependence of the total cross-section in particular on crystallite size, in the Bragg scattering region, could influence the reflector performance, and if such an effect is significant, it should be taken into account in the design of the moderator/reflector system. In this paper, we report on the preliminary results of using cross-section libraries, which include corrections for the crystallite size effect, in spallation source neutronics calculations
Generation of thermal neutron scattering libraries for liquid para-hydrogen and ortho-deuterium using ring-polymer molecular dynamics
In this paper we present results of combining ring-polymer molecular dynamics with the LEAPR and THEMR modules of NJOY to generate thermal neutron scattering libraries for liquid para-hydrogen and ortho-deuterium. We present the methodology and show that it produces results that are in good agreement with data from both recent available measurements and previous theoretical studies. We also present some simple benchmark Monte-Carlo simulations compared with other available libraries
Radiation transport calculations for the European Spallation Source accelerator environment
A central component of the European Spallation Source is the high-power
proton accelerator. The accelerator aims in the future to provide 2 GeV protons
to a rotating tungsten target for the production of neutrons at 5 MW of average
beam power for neutron scattering studies. Extensive shielding surrounds the
accelerator, in order to provide sufficient safety for the public and workers
against radiation produced along it's length. This largely comprises several
meters of soil, called the berm, and concrete structures located around the
accelerator tunnel. However, due to the need for access to the accelerator,
during maintenance and connections for other utilities, the shielding contains
a number of penetrations which leads to weaknesses in localized areas. For
these reasons, shielding design of such a facility must take care to address
issues related to both the deep-penetration of the radiation through thick
shields, while at the same time accounting for the streaming nature of the
radiation through ducts and chicanes. In addition, radiation produced from
activated components of the accelerator also poses risks for workers and
public. For example, activated magnets will need maintenance and workers may
need to access areas where activated water circulates. Thus, activation
analyses are also needed in combination with the prompt-dose rate estimates for
a complete analysis. In this summary, we present the results of a series of
such studies carried out on various components around the ESS accelerator.Comment: 14th International Conference on Radiation Shielding and 21st Topical
Meeting of the Radiation Protection and Shielding Division (ICRS 14/RPSD
2022) meetin
Thermal scattering libraries for cold and very-cold neutron reflector materials
We present recent developments of improved modelling methods for simulating neutron transport in reflector materials of interest for neutron source applications. These include materials to be used as traditional reflectors around the neutron moderator, such as beryllium, and also novel materials, such as nanodiamond particles, to be used as a reflector for very-cold neutrons in the neutron beam extraction area of a neutron scattering instrument. Of particular interest is the inclusion of physical effects that are not modelled in standard thermal scattering libraries used for Monte-Carlo simulations, such as extinction in beryllium reflectors and effects of small-angle neutron scattering from nanodiamond particles