Colombelles, ZAC Lazzaro 3

International audienc

Colombelles, ZAC Lazzaro 3

International audienc

Colombelles, ZAC Lazzaro 3

International audienc

Development of a new method for the detection of illicit materials based on the active interrogation method and photoneutron spectrometry

The 8th International Conference on Advancements in Nuclear Instrumentation Measurement Methods and their Applications; (ANIMMA 2023) , Lucca, Italy, June 12-16 2023International audienceThis work investigates the development of a novel method for the detection of illicit materials based on active photon interrogation associated to photoneutron spectrometry. It is an original attempt to explore the principle of inducing photonuclear reactions on samples to determine the presence of light elements such as nitrogen, oxygen and carbon and therefore to extend the use of active photon interrogation for the detection of conventional explosives, narcotics and chemical weapons

Development of a new method for neutron spectra analysis based on a deep learning algorithm for the detection of illicit materials

International audienceThe global context and the growth in international trade is widely recognized as a boon for the trafficking of illicit materials. In the area of homeland security, the approaches used have failed to provide an up and running technique for non-intrusive on-site inspections. Neutron-induced reactions rely on precise measurement of gamma spectra, which is generally very complex due to high level of background noise. Active photon interrogation methods have also been overlooked but only in the context of actinide detection using photofission reactions (γ,f). This work describes the design of a novel method for the detection of illicit materials based on active photon interrogation associated to photoneutron spectrometry. It is the first attempt to explore the principle of inducing photonuclear reactions on samples to determine the composition of light elements such as nitrogen, oxygen and carbon and therefore to extend the use of active photon interrogation for the detection of conventional explosives, narcotics and chemical weapons. The approach is based on a source of photons produced by electron linear accelerator to induce photonuclear reactions on different materials, on the spectrometry of the photoneutrons created, and on the implementation of a new digital analysis method based on a convolutional neural network for extracting the neutron contribution for each photon energy of the bremsstrahlung spectrum in the total neutron spectra measured. The results of this study suggest that the use of neural networks trained with Monte Carlo simulated spectra can be a digital alternative to the "tagged photon" experimental method. Our study, therefore, provides the foundation of a new way of extracting neutron contributions for discrete photon energy of the continuous bremsstrahlung spectrum

Evaluation of neutron-induced activation gamma-rays creation and transport in a LaBr3 inorganic scintillator with PHITS

Conference ANIMMA 2023 - 8th conference on Advancements in Nuclear Instrumentation Measurement Methods and their Applications, Lucca (Italy) 12-16 June 2023International audienceIn the framework of its R&D activities to support the metal industry, the Laboratory for Integration of Systems and Technology of CEA Paris-Saclay started studies with the aim of characterizing scrap metal by means of neutron activation analysis. This involves irradiating samples of scrap metal with a pulsed-neutron source in order to determine the copper composition (mainly Cu-65 and Cu-63). In this scope, the use of a LaBr3 detector with an energy resolution of 14.6 keV at 661 keV is hereby investigated to carry out acquisitions during and between the irradiation pulses. As pointed out in literature, the LaBr3 inorganic scintillator might suffer some damage in a neutron-rich environment. Understanding the degradation of the energy resolution of such detector due to a high dose environment is essential to analyse the recorded signal. In this context, the work described in the present paper explores the coherent creation of neutron induced activation products as well as their respective delayed gamma rays in the quite well established LaBr3 inorganic scintillator by the mean of two steps Monte Carlo simulations performed first with the DCHAIN code, and secondly with the PHITS general purpose Monte Carlo particle transport code. Coherence was shown between neutron-induced activation gamma rays and the isotopes created in the crystal, and between the isotopes created and their decay through time. Thus, this study validate the two-step calculation scheme with PHITS and DCHAIN for both the time and energy aspects

Neutron spectra from photonuclear reactions: performance testing of Monte-Carlo particle transport simulation codes

International audienceThe production of neutrons in photon-induced nuclear reactions in the giant-dipole-resonance energy domain remains a topic of high interest for various applications, including the activation and decommissioning of electron accelerator facilities, the detection of illicit materials for homeland security, and the evaluation of neutron dose received by patients in radiotherapy treatments. General purpose Monte-Carlo (MC) simulation codes for particle transport are intensively used to account for photoneutron production in these applications. However, due to the current scarcity of measured photoneutron energy spectra in the literature, an experimental validation of MC-simulated photoneutron energy distributions is not always feasible. Therefore, a critical benchmark among simulation results from various MC codes presently appears as the only option to systematically assess their capabilities in accurately simulating photoneutron production for nuclear reactions of interest. In this work, neutron energy spectra from several targets under irradiation by 20 MeV photons are simulated, employing various state-of-the-art MC codes (FLUKA, Geant4, MCNP6, and PHITS) in their default settings. A detailed analysis of the simulated neutron spectra allows one not only to assess the performance of various MC codes in applications such as those mentioned above, but also to partially gauge the incurred systematic uncertainty, and to highlight the present need for further evaluated nuclear data in this domain, ultimately suggesting precautions on the use of MC codes for applications where photonuclear reactions play a dominant role and where not only the production rate but also the energy spectrum of the emitted neutrons matters