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In this paper we propose a method of fast neutron flux estimation from a pulsed D-T neutron generator with application of single CaF2 scintillation crystal. The analysis method relies on 19F(n, α)16N threshold activation reaction having neutron energy threshold at 1.6 MeV. As a result, the 16N undergo β− decay with half-life of 7.1 s, emitting β particles with endpoint up to 10.4 MeV in the scintillator medium. Integration of the β distribution curve, preceded by calculation of (n, α) rate on F with Monte Carlo N-Particle Transport Code v6 (MCNP6) for fixed geometry, allows to estimate the neutron flux in 4π per second within few minutes.

In this paper we present the prompt photofission neutron detection performance of undoped CaF2 scintillator using Threshold Activation Detection (TAD). The study is carried out in the frame of C-BORD Horizon 2020 project, during which an efficient toolbox for high volume freight non-intrusive inspection (NII) is under development. Technologies for radiation monitoring are the part of the project. Particularly, detection of various radiological threats on country borders plays an important significant role in Homeland Security applications. Detection of illegal transfer of Special Nuclear Material (SNM) - 235U, 233U and 239Pu - is particular due to the potential use for production of nuclear weapon as well as radiological dispersal device (RDD) V known also as a “dirty bomb”. This technique relies on activation of 19F nuclei in the scintillator medium by fast neutrons and registration of high-energy β particles and γ-rays from the decay of reaction products. The radiation from SNM is detected after irradiation in order to avoid detector blinding. Despite the low 19F(n,α)16N or 19F(n,p)19O reaction cross-section, the method could be a good solution for detection of shielded nuclear material. Results obtained with the CaF2 detector were compared with the previous study done for BaF2 and 3He detector. These experimental results were obtained using 252Cf source and 9 MeV Varian Linatron M9 linear accelerator (LINAC). Finally, performance of the prompt neutron detection system based on CaF2 will be validated at Rotterdam Seaport during field trails in 2018.

Conference of 2016 IEEE Nuclear Science Symposium, Medical Imaging Conference and Room-Temperature Semiconductor Detector Workshop, NSS/MIC/RTSD 2016 ; Conference Date: 29 October 2016 Through 6 November 2016; Conference Code:131365; International audience; For several years, detection of various threats on country borders plays a significant role in the frame of Homeland Security applications. One of this threat is the illicit trafficking of nuclear materials (especially including Special Nuclear Material - SNM - 235U, 233U or 239Pu), which can be potentially used for production of nuclear weapon as well as radiological dispersal device (RDD) - known also as a "dirty bomb". In order to detect the potentially hidden nuclear material, systems using linear accelerators and a group of detectors are developed by several scientific groups around the world. Besides solutions focusing on detection of delayed γ-rays or neutrons, also the systems dedicated for prompt neutron detection were proposed. One of the possible prompt neutron detection technique is known as Threshold Activation Detection (TAD). This technique relies on activation of 19F nuclei in the scintillator medium by fast neutrons and registration of high-energy particles and γ-rays from the decay of reaction products (for example, 19F(n,α)16N or 19F(n,p)19O). Recent studies in the frame of the European Horizon 2020 C-BORD project showed that, despite the low 19F(n,α)16N or 19F(n,p)19O reaction cross-section, the method could be a good solution for detection of shielded nuclear material. A benchmark of the TAD technique based on fluorine detectors with reference method focused on delayed neutron detection with 3He detectors will be presented in this paper. These experimental results were obtained using 9 MeV Varian Linatron M9 linear accelerator (LINAC).