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Active neutron interrogation is a nondestructive active method that consists in inducing fission reactions on actinides (e.g., 235U and 239Pu) and then in detecting prompt and delayed particles emitted further to these reactions. This method is required in various application fields such as radiological characterization of nuclear waste packages and homeland security. Neutron sources traditionally used in neutron interrogation facilities are deuterium–tritium neutron generators. However, a linear electron accelerator (LINAC) can also be used as a photoneutron generator. When accelerating electrons with energy lower than 10 MeV, the use of a secondary target such as heavy water is of interest to convert bremsstrahlung photons to neutrons and to improve neutron production. In this paper, we characterize the photoneutron flux emitted by a Linatron-M9 VARIAN LINAC and the photoneutron flux emitted by a secondary target made of heavy water. We show that operating the LINAC at 9 MeV, the average emission intensity reaches $1.08 \times 10^{10}$ neutrons per second, which is on the order of $10{\times}$ higher than the maximum average emission intensity delivered by a traditional deuterium–tritium neutron generator. Then, we carry out neutron interrogation measurements on uranium samples using the Linatron-M9 LINAC and a secondary target made of different volumes of heavy water. We show that prompt neutron signals were enhanced when using 16 kg of heavy water and operating the LINAC at 9 MeV. Performances of the setup were then assessed by carrying out measurements on a mockup of nuclear waste drum containing different types of matrices. Considering a 0.22-g/cm3 iron matrix and a uranium sample at the center of the drum, 44 mg of 235U can be detected in 5 min of irradiation time using a single detection block housing five 150NH100 3He detectors. [ABSTRACT FROM AUTHOR]

A new, nonresonant approach to photon accumulation in a system of two spherical mirrors is demonstrated experimentally. A high accumulation coefficient is obtained experimentally, and sufficient efficiency of this technique for application in such areas as spectroscopy, photochemistry, and photon neutralization of negative-ion beams is demonstrated. The photon accumulation efficiency is determined mainly by mirror reflectivity. It is nearly independent of the quality of the coupled-in radiation and does not require very high precision in aligning optical elements. The experimentally obtained data agree with theoretical calculations. [ABSTRACT FROM AUTHOR]

The radioisotope production has a crucial role in medical diagnosis and therapy. In this work, we investigated the possibility of obtaining radioisotopes of medical interest through photo-neutron reactions using the highintensity γ beams at the Extreme Light Infrastructure - Nuclear Physics (ELI-NP) facility. The specific activity for three benchmark radioisotopes, 99Mo/99mTc, 186Re and 225Ra/225Ac, was obtained as a function of γ-beam energy, target geometry and irradiation time. Optimization for the generation of these radioisotopes at ELI-NP was investigated. We estimated that a saturation specific activity of the order of 1-2 mCi/g could be obtained for a thin target (radius 1-2 mm, thickness 1 cm) and for a conservative γ-beam flux of 1011 s-1. The ELI-NP, based on these estimations, could provide the possibility for the production of certain radioisotopes in sufficient quantities for nuclear medicine research. [ABSTRACT FROM AUTHOR]

The theoretical photo-neutron cross sections for ( γ, n) reaction have been calculated on Nd rare-earth isotopes at photon energies of 8-23 MeV using the PCROSS, TALYS 1.2, and EMPIRE 3.1 computer codes. TALYS 1.2 two-component exciton model and EMPIRE 3.1 exciton model has been used to calculate the pre-equilibrium photo-neutron cross sections. PCROSS Weisskopf-Ewing model has been used for the reaction equilibrium cross-section calculations. The obtained cross sections have been compared with each other and against the experimental values existing in the EXFOR database. Generally, pre-equilibrium model cross-section calculations are in good agreement with the experimental data for all reactions along the incident photon energy in this study. [ABSTRACT FROM AUTHOR]

Abstract: A fully detailed Monte Carlo geometrical model of an 18MV Varian Clinac 2100C medical linear accelerator, lodged at Blida Anti-Cancer Centre in Algeria, was developed during this study to estimate the photoneutrons spectra and doses at the patient table in a radiotherapy treatment room, for radiation protection purposes. Subsequently, thanks to this model, extensive M.C. calculations of neutron fluences and ambient dose equivalent were carried out at three selected locations on the patient table in the medical facility for a reference field size of 10×10cm2 and a Source to Surface Distance (SDD) of 100cm. At the patient table, the calculated neutron ambient doses equivalent were 3.50, 0.89 and 0.62 mSvGy−1 at isocenter, 40cm and 100cm from the isocenter. Thereafter, a sensitivity analysis was performed to investigate the effect of variation of some pertinent parameters (source term model, Multi-Leaf Collimators and the shielding walls of the treatment room) on the production of the photoneutrons doses at the patient table. Finally, a full comparative study has been performed, in order, to estimate the consistency of the author's results. Therefore, the obtained M.C. results were compared, firstly, to a few measurements acquired, for the same irradiation facility using CR-39 Nuclear Track Detectors (NTDs), at the isocenter assuming different field sizes, and secondly, to both theoretical and experimental results available in the literature for the same medical facility and for different irradiation conditions. From these comparisons, a mean difference (for all the locations and field sizes considered) of about 15% was found. Despite, the possible differences in the accelerator modeling, including variations in the accelerator head and room geometries and differences in the computational tools and photoneutrons cross-sections data used in the literature, the results obtained through this investigation are encouraging, highlighting thereby the consistency of the geometrical M.C. model assumed in this work. [Copyright &y& Elsevier]

Photoneutrons induced by two high energies range from the Elekta medical linear accelerator (10 and 18 MV) were measured by nuclear track detectors (NTDs). CR-39 NTD in contact with converter screen slide films, natural boron of thickness 40 μm coated on the polyester film (BN1). Detectors were exposed at 100 cm SSD with field size 20×20 on the patient table, with chest phantom and with build-up Perspex used for high-energy exposure. CR-39 registers the thermal neutron by the (n–α) reaction with the thin layer of boron and the fast neutron was measured through the (n–p) elastic scattering with the H2molecules in the CR-39 constituents.It was found that the total neutron dose (thermal and fast) from the 18 MV X-ray is higher than that of 10 MV. The measured thermal neutron dose is relatively smaller than the fast neutron dose in the case of direct exposure at the two X-ray energies. On the other hand, in the case of measurements on phantom and upon the use of build-up Perspex sheets, the ratio of fast to that of thermal is less than that of direct exposure. [ABSTRACT FROM AUTHOR]

Abstract: In contrast to conventional bremsstrahlung photon beam sources, laser backscatter photon sources at electron synchrotrons provide the capability to selectively tune photons to energies of interest. This feature, coupled with the ubiquitous giant dipole resonance excitations of atomic nuclei, promises a fertile method of nuclear isotope production. In this article, we present the results of simulations of production of the medical/industrial isotopes 196Au, 192Ir and 99Mo by (γ,n) reactions. We employ FLUKA Monte Carlo code along with the simulated photon flux for a beamline at the Canadian Light Source in conjunction with a CO2 laser system. [Copyright &y& Elsevier]

The U( γ, n)U reaction cross-section at the end point bremsstrahlung energies of 8 and 10 MeV was measured by using an activation technique. Induced gamma ray activities were measured by high resolution gamma-ray spectrometer with high-purity germanium detector. The photo neutron cross section on U is also calculated theoretically using TALYS 1.2 computer code. The experimentally obtained reaction cross sections were compared with the flux weighted average values from the literature data based on mono-energetic photon as well as the value from TALYS. It was found that the cross section of U( γ, n)U reaction increases with increase of bremsstrahlung energy and were closer to the flux-weighted experimental data from literature and the values from TALYS based on mono-energetic photons. [ABSTRACT FROM AUTHOR]