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The paper introduces original Bayesian algorithm developed by the CEA LIST for the measurement of low-activity uranium contaminations using high-resolution gamma-ray spectrometry based on a high purity germanium diode detector. Such measurement indeed provides access to an indirect estimation of surface activity, assuming that the ratio between the number of alpha particles to be quantified and the number of gamma-rays that are detected is known. The Bayesian approach allows to lower detection limits in low count rates and exploit a richer time-energy information structure than the algorithms used in conventional detection procedures. The performance evaluation and characterization of Bayesian statistical tests is performed using classical receiver operating characteristic curves by comparison to frequentist hypothesis tests. The results indicate that the Bayesian approach, in conjunction with HPGe detector has a superior detection performance of the low-activity uranium contamination up to 50% than that achieved within the frequentist tests. Furthermore, it ensure a significant compromise between the true detection rate, the false alarm rate and the response time.

Special Nuclear Material (SNM) such as uranium and plutonium isotopes could be potentially used to make a nuclear bomb involved in a terrorist attack. To prevent illicit trafficking of SNM in Europe, inspection of cargo containers at borders is required. X-ray scanning is widely used by customs to control suspect containers. However, this technology is not the most adapted to bring to light SNM signature. Therefore, a second line technology based on the photofission reaction could enable to detect SNM in a non-destructive manner. In the frame of the C-BORD European project, several teams specialized in photofission have joined forces to design an active photon interrogation system enabling to detect SNM hidden in cargo containers. The system is based on the use of a linear electron accelerator (linac). First, high-energy photons generated by Bremsstrahlung in the conversion target of the linac irradiate a suspect area of the cargo container. Secondly, prompt and delayed particles emitted following photofission reactions are detected if SNM is present. The largest seaport in Europe (Maasvlakte, in the suburbs of Rotterdam, Netherlands), where 9 MeV linacs are used by Dutch customs for X-ray scanning, has been chosen as test site. In order to deploy a full system taking advantage of all photofission signatures, different subsystems have been developed. In this paper, first, we give an overview of the photofission system. Then, we show how the system has been deployed at the Rotterdam seaport in September and October 2018 and tested on mock-ups of cargo containers. Finally, we show that setting up a photon interrogation system on an industrial facility initially designed for X-ray scanning is a challenge which has been successfully met in the frame of the C-BORD project to deploy the first photofission measurement system on an industrial site in Europe. The outcomes of this first deployment will be exposed and the future challenges to be addressed will be discussed.

The principle of the proposed method is based on a simple and efficient way to estimate the muon energy deposition in a cylindrical sensor. Muon initial energy is randomly sampled from experimental distributions and the traveled distance through the scintillator volume is assessed from a Monte-Carlo model in cylindrical coordinates. Energy deposition is estimated by solving Bethe-Block formula thanks to digital Euler approximation. This model has been experimentally tested in our laboratory using NaI(Tl) scintillator apparatus. Results from this comparison show good agreement and confirm the potential of the model. Sources of discrepancy are emphasized, while explaining peak shift between experimental results and theoretical calculations.

The approach of the scheme is to pile-up X-ray photons on the scintillator to generate a high energy peak in the spectrum. The system includes a miniature X-ray generator, a brass disk with a thin slit rotated by a motor and placed in front of the X-ray window, and a collimator placed in front of the scintillation detector to reduce the time of alignment between the scintillation detector and the X-ray generator. The rotating brass disk placed between the X-ray source and the collimator is deployed as a high-frequency obturator. If, during a time duration lower than the integration time of the scintillation detector, a large number of photons interact with the scintillator, the energy is added and the spectrometer records this energy as the contribution of a high energy single photon. Experimental results underlines a tangible proof of concept for a selfcalibration device, which will be valuable for the correction of the temperature drift in the scintillator-photomultiplier pair.

Conference of 4th International Conference on Advancements in Nuclear Instrumentation Measurement Methods and their Applications, ANIMMA 2015 ; Conference Code:121554; International audience; Recent developments of plastic scintillators are reviewed, from January 2000 to June 2015. All examples are distributed into the main application, i.e. how the plastic scintillator was modified to enhance the detection towards a given radiation particle. The main characteristics of these newly created scintillators and their detection properties are given.

International audience; In the context of failed fuel detection in Sodium-cooled Fast Reactors (SFR), Delayed Neutrons Detection (DND) systems are implemented. This study deals with the design optimization of such a system by Monte-Carlo particle transport simulation (MCNP). During a clad failure, neutron precursor fission products (mainly halogen ones: 137 I, 87 Br, 88 Br) escape into the primary coolant. The detection of these precursors through their delayed neutrons ensures a diagnosis on clad failures events. In DND systems, 3 He proportional counters are chosen as the best available technology for neutron detection purposes. Associated with 3 He counters, polyethylene blankets are required in order to thermalize neutrons. Feedbacks from past SFR have shown an important noise coming from photoneutrons mitigating the signal-to-noise ratio. These photoneutrons originate from the 2 D(γ,n) reaction in polyethylene (in natural abundance) and is due to the 24 Na activity. Another material avoiding photoneutrons production is considered in this paper as moderator. Indeed, the graphite appears as a good candidate, sufficiently light for neutron thermalization and with a C(γ,n) reaction threshold higher than energies considered here. The first simulations run with MCNPX code provide satisfactory results for a low-noise DND system based on graphite thermalizing.

Localization of radioactive sources is a major issue for many applications in the nuclear industry. Gamma imaging is a powerful non-destructive technique, enabling to locate radioactive hot spots contained in a given area and well-adapted to this topic. Industrial gamma cameras have been commercialized by various companies for several years but present some limitations in terms of sensitivity, weight and ease of use in comparison with the requirements of end-users.

The tracking of radiation contamination and distribution has become a high priority in the nuclear cycle industry in order to respect the ALARA principle which is a main challenge during decontamination and dismantling activities. To support this need, AREVA/CANBERRA and CEA LIST have been actively carrying out research and development on a gamma-radiation imager. In this paper we will present the new generation of gamma camera, called GAMPIX. This system is based on the Timepix chip, hybridized with a CdTe substrate. A coded mask could be used in order to increase the sensitivity of the camera. Moreover, due to the USB connection with a standard computer, this gamma camera is immediately operational and user-friendly. The final system is a very compact gamma camera (global weight is less than 1 kg without any shielding) which could be used as a handheld device for radioprotection purposes. In this article, we present the main characteristics of this new generation of gamma camera and we expose experimental results obtained during in situ measurements. Even though we present preliminary results the final product is under industrialization phase to address various applications specifications.

The MOBISIC project, funded by the System@tic Paris-Region cluster, is being developed in the context of local crisis (attack bombing in urban environment, in confined space such as an underground train tunnel etc.) or specific event securing (soccer world cup, political meeting etc.). It consists in conceiving, developing and experimenting a mobile, modular ('plug and play') and multi-sensors securing system. In this project, CEA LIST has suggested different solutions for nuclear risks detection and identification. It results in embedding a CZT sensor and a gamma camera in an indoor drone. This article first presents the different modifications carried out on the UAV and different sensors, and focuses then on the experimental performances.

CEA is developing a method to prevent illegal traffic of special nuclear material (SNM) at borders, especially sea ports where millions of containers are transiting every day. This nondestructive method is based on the interrogation of the container by high-energy photon and the subsequent detection of particles emitted after the fission. This technique requires the knowledge of nuclear parameters that have been rarely measured for fission induced by photons. Therefore, we present fundamental measurements of these parameters for uramium-238 and uranium-235. Numerical simulations to assess the SNM detection performances are also reported.

Being able to characterize and classify nuclear waste packages is crucial for an appropriate mode of storage. The alpha-activity due to the presence of actinides inside the packages can be determined using non-destructive active (NDA) methods. CEA-LIST is developing one of those, based on fission induced by photons that allows us to quantify the global mass of actinides in large concrete packages and localize it by the means of a tomography using delayed particles emitted after the fission process.

A characterization of the alpha-activity due to the presence of actinides inside nuclear waste packages is necessary to select the best mode of storage. Non-destructive active methods, based on fission process, allow to quantify the global mass of actinides. However, these measurements give no information on the nature of isotopes in most cases. We are currently developing a method to identify actinides (235U, 238U, 239Pu), based on the detection of delayed gammas emitted by fission products. The delayed gamma spectrum can be regarded as a "fingerprint" of the irradiated sample. Qualitative and quantitative analysis of peaks allow an identification of actinides. The main purpose of this paper is twofold. First, basis of this method of differentiation are described. Then, experimental results obtained in fission and photofission are presented, in particular in the case of mixtures containing several actinides.