Spallation

A simulation for the study of cosmic-ray muon spallation backgrounds in the
Super-Kamiokande water Cherenkov detector was developed with the help of the
Geant4 toolkit. The simulation was validated against results from a 2014 article
of S. W. Li and J. F. Beacom [1]. Though, the validation showed an overall
agreement, discrepancies were found in the isotopes yield predictions and in the
neutrons behavior. These two facts are linked, as neutrons are the most important
particles for isotopes production. A final work was carried out to study the
different results from different choices of physics list and from simplifications on
the initial muons conditions. The isotopes yields also show significant variations
in the case of the different physics lists comparison. In particular, these deviations
can be used to evaluate systematic error coming from the physics models used
in the simulation. Finally, the simplifications did not have serious implications
in the general physics results, only 7 large differences, out of 59 isotopes, were
found for the yield predictions. These differences are for very rare events, which
still have significant statistical fluctuations for the numbers of events simulated.

Neutron production and transport in spallation targets made of uranium and americium are studied with a Geant4-based code MCADS (Monte Carlo model for Accelerator Driven Systems). A good agreement of MCADS results with experimental data on neutron- and proton-induced reactions on ^241Am and ^243Am nuclei allows to use this model for simulations with extended Am targets. It was demonstrated that MCADS model can be used for calculating the values of critical mass for ^233,235U, ^237Np, ^239Pu and ^241Am. Several geometry options and material compositions (U, U+Am, Am, Am_2O_3) are considered for spallation targets to be used in Accelerator Driven Systems. All considered options operate as deep subcritical targets having neutron multiplication factor of k ∼ 0.5. It is found that more than 4 kg of Am can be burned in one spallation target during the first year of operation.

Abstract: This report results from a contract tasking University of Cassino as follows: The contractor shall investigate the issue of advanced failure prediction and design by means of innovative material failure modeling and computational techniques. The specific tasks include: - the ...

High power pulsed laser (above 1GW/cm) interaction with matter yields to very high amplitude pressure loadings with very short durations, initiating into solids a strong short shock wave. Compared to the conventional generators of shock (launchers of projectiles, explosives), these particular characteristics offer the possibility to study the behaviour of matter under extreme dynamic conditions, with a possible recovery of the shocked samples presenting the effects of the passage of the shock in most cases. This article introduces the principle of laser shock generation, the characterization of these shocks, principal mechanisms and some effects associated with their propagation in the solids (spallation, Laser Adhesion Test, geological applications).

: This empirical study is designed to quantify mining explosions as sources of seismic and infrasound signals. The study focuses on the Western US, where a variety of different types of mining operations exist, ranging from surface coal cast blasting to hard rock fragmentation blasting in porphyry copper mines. The study is extended to the taconite mines of the Mesabi Range of Minnesota. Newly installed instrumentation, including in-mine equipment for ground truth as well as regional seismo-acoustic deployments to complement existing resources in the region, is a key component of the study. In-mine monitoring is ongoing at the Morenci Mine in Arizona and the Tyrone Mine in New Mexico. The seismo-acoustic station at Ft. Hancock, Texas, and the infrasound upgrade to Tucson, Arizona, and WUAZ will also be illustrated. Data from this study have been used to address coupling and source characterization issues for both seismic and infrasound signals. The seismic coupling of large-scale ca...

System design engineers must translate permitted overall facility downtime into detailed design and operating specifications for numerous systems and subsystems that make up the facility. The process of assigning reliability and maintainability requirements to individual equipment systems to attain a desired overall availability is known as availability apportionment. Apportionment is normally required early in conceptual design, when little or no hardware information is available. Apportionment, when coupled with availability prediction, enables the selection of viable alternative configurations, identified problem areas, and provides redirection of the program into more productive areas as necessary. A method for apportioning, or budgeting, overall facility availability requirements among systems and subsystems is presented in this paper. An example of applying this methodology to the Spallation Neutron Source (SNS) facility is given.

In this paper we introduce an idea for improving the broader pulse width and the long-time tail of cold neutrons from a coupled composite moderator system, by decoupling the premoderator from the reflector. We confirmed experimentally that the pulse width from a decoupled system, a 5 cm thick liquid-hydrogen moderator with 3 cm thick light-water premoderator decoupled from a graphite reflector, can be reduced considerably almost at no cost of the peak height and the decay time of the pulse can also be improved significantly, when compared to those from a coupled composite moderator of the same material and dimensions. The present results are compared to those obtained with an alternative method by heterogeneously poisoning the reflector.