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We have measured with a LaCl 3 detector the γ -ray spectrum emitted by a 235 U enriched UO 2 fuel rod 10 s after being irradiated with thermal neutrons. The experimental results are compared with simulations performed with the fission product yield and radioactive decay data libraries present in the most recent releases of ENDF/B, JEFF and JENDL. [ABSTRACT FROM AUTHOR]

The accurate determination of the response function of organic scintillation neutron detectors complements their experimental characterization. Monte Carlo simulations with GEANT4 can reduce the effort and cost implied, especially for complex detection systems for which the characterization is more challenging. Previous studies have reported on the inaccuracy of GEANT4 in the calculation of the neutron response of organic scintillation detectors above 6 MeV, due to an incomplete description of the neutron-induced alpha production reactions on carbon. We have improved GEANT4 in this direction by incorporating models and data from NRESP, an excellent Monte Carlo simulation tool developed at the Physikalisch-Technische Bundesanstalt (PTB), Germany, for the specific purpose of calculating the neutron response function of organic scintillation detectors. The results have been verified against simulations with NRESP and validated against Time-Of-Flight measurements with an NE213 detector at PTB. This work has potential applications beyond organic scintillation detectors, to other types of detectors where reactions induced by fast neutrons on carbon require an accurate description. [ABSTRACT FROM AUTHOR]

Neutron production induced by (α ,xn) reactions is important in various fields, such as nuclear power technologies or the search for rare events carried out in underground laboratories. One of the most relevant scenarios is related to underground dark matter experiments, where the neutrons produced by the α -decay from radioactive contaminants in the detector materials can generate an irreducible background, limiting the sensitivity of the experiment. A precise estimate of the background due to these neutrons is crucial for the experiments currently taking data and for the design of the next generation detectors. In this work, we prove that Geant4 can be used to calculate neutron yields and energy spectra induced by α -decay. Additionally, we provide a Geant4 tool for performing these calculations at http://win.ciemat.es/SaG4n/. These neutrons are produced according to the information compiled in data libraries originally written in the ENDF-6 format. In this article we also review the different databases available, showing the differences and similarities among them. Finally, we compare several Geant4 neutron production yields and spectra with experimental data and other codes. [ABSTRACT FROM AUTHOR]

Abstract: The n_TOF Total Absorption Calorimeter (TAC) is a BaF2 segmented detector used at CERN for measuring neutron capture cross-sections of importance for the design of advanced nuclear reactors. This work presents the simulation code that has been developed in GEANT4 for the accurate determination of the detection efficiency of the TAC for neutron capture events. The code allows to calculate the efficiency of the TAC for every neutron capture state, as a function of energy, crystal multiplicity, and counting rate. The code includes all instrumental effects such as the single crystal detection threshold and energy resolution, finite size of the coincidence time window, and signal pile-up. The results from the simulation have been validated with experimental data for a large set of electromagnetic de-excitation patterns: of well known calibration sources, neutron capture reactions in light nuclei with well known level schemes like natTi, reference samples used in () measurements like 197Au and experimental data from an actinide sample like 240Pu. The systematic uncertainty in the determination of the detection efficiency has been estimated for all the cases. As a representative example, the accuracy reached for the case of 197Au() ranges between 0.5% and 2%, depending on the experimental and analysis conditions. Such a value matches the high accuracy required for the nuclear cross-section data needed in advanced reactor design. [Copyright &y& Elsevier]

Abstract Large size detectors based on Cs 2 LiYCl 6 :Ce (CLYC) are capable of performing a combined γ -ray and neutron spectrometry and constitute a promising technology for a wide range of applications in nuclear and high energy physics. Due to their novelty, the comprehensive characterization of the performance of individual CLYC detectors is of great importance for determining their range of applicability. In this work we report on a wide series of measurements performed with a commercial 2” × 2” CLYC crystal. Good energy and timing resolution values, of 4.7% (@ 662 keV) and 1340 ps (FWHM) respectively, were achieved, and a neutron/ γ separation figure of merit value of 4.2 was obtained. A dedicated measurement for investigating the intrinsic background of the detector was performed at the Laboratorio Subterráneo de Canfranc (Spain). It evidenced a sizeable contamination in the detector materials which poses limits in the use of CLYC in low background experiments. In addition, detailed Monte Carlo simulations with the GEANT4 toolkit were performed for modelling the response function of the CLYC detector to γ -rays. An excellent agreement with the experimental data has been achieved. [ABSTRACT FROM AUTHOR]