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To fulfill needs in oncological research a new Micromegas detector has been developed to follow radiolabelled drugs in living organisms at the single cell level. This article describes the proof-of-concept of such a detector and compares its ability to detect and assess sub-becquerel \tritium~activities with a commercial $\beta$-imager, Comment: 14 pages, to be submitted to NIMA

International audience; Fuel debris have a distinct neutron signature that can be detected to locate the said debris in a damaged nuclear power plant. Neutron measurement in a damaged PCV environment is however submitted to severe deployments constraints, including a high-dose-rate gamma background and limited available space. The study was therefore oriented towards small fission chambers (FC), with U-235-enriched active substrates. To investigate the expected performance of the FC in various irradiation conditions, a numerical model of the detector head was built. We describe the elaboration and experimental calibration of the numerical model and the Monte Carlo study of the fission rate inside U-235 coatings per generated neutron. The evaluation of a representative calibration coefficient then allowed us to carry out a multi-parameter performance study of a FC underwater, aiming at computing an explicit response function linking, on the one hand, the activity and spatial distribution of neutron emitters in a water container, with, one the other hand, the expected count rates measured by a fission chamber as a function of its radial and axial position inside the water volume. The FC underwater behavior was subsequently corroborated by a measurement campaign on a FC response, set at different positions inside a water drum, as a function of its axial and radial distance to a Cf-252 neutron source attached near the center of the container. We finally present an approach in which fuel debris localization is defined as an Inverse Problem, solvable with a Maximum-Likelihood Expectation Maximization (ML-EM) iterative algorithm. The projector matrix is built by capitalization on the results of the previously consolidated numerical studies. The ML-EM was tested on simulated data sets with a varying number of active voxels. Our first results indicate that, for a thermal neutron flux in the order of 10 n.cm−2.s−1 at the detector, originating voxels are identified with a spatial resolution in the radial plane in the order of 10 to 100 cm2.

International audience; This work aims at assessing the performance of a 235U enriched fission chamber in order to localize fuel debris, prior to dismantling operations, in a flooded primary containment vessel of a damaged nuclear reactor such as Fukushima Daiichi. Based on both a comprehensive scan of the environment and the detection of neutrons emitted by the melted core, fuel debris can be localized. In this paper, we carry out a simulation study using the MCNP6 code to investigate fission chamber response in the frame of fuel debris localization measurements in a damaged nuclear reactor. The CFUF34 fission chamber (manufactured by PHOTONIS) and the primary containment vessel of Fukushima Daiichi Unit 1 were chosen to conduct this work. Impact of different parameters were investigated with MCNP6, such as: neutron energy, water temperature, fission chamber position (altitude, lateral shift, and rotation), and sensitivity loss due to sediments potentially covering fuel debris. In summary, we show that fuel debris should be sought by their thermal neutron signature at a distance of a few centimeters and that potential rotational movements of the fission chamber up to 60° have a limited impact on signals measured. We also show that sensitivity loss due to sediments potentially covering fuel debris has been evaluated on the order of a factor 10 considering a 30 cm-thick sediment layer. On the other hand, experiments were performed to assess the impact of a strong gamma dose rate on fission chamber measurements. These irradiation trials involved a CFUE32 fission chamber (also manufactured by PHOTONIS) available in our laboratory and three different irradiation means: an X-ray tube, an 192Ir source, and a linear electron accelerator. These experiments enable to draw the conclusion that the fission chamber is not impacted by the gamma dose rate up to 104 Gy h−1, which is in good agreement with specifications provided by the manufacturer (PHOTONIS). In addition, no performance degradation was observed after an integrated gamma dose of 2200 Gy on the fission chamber in a 10 min irradiation. However, when the fission chamber is irradiated by gamma dose rates above 104 Gy h−1 (upper limit of the operating domain specified by PHOTONIS), a significant gamma background is observed. Nevertheless, as the gamma dose rates at Fukushima Daiichi should not exceed 103 Gy h−1, fission chamber measurements performed towards fuel debris localization in the primary containment vessels of the units would not be affected by the severe gamma-ray irradiation.

International audience; For many years 3H and 14C labelling of molecules of pharmaceutical interest has been performed to study their in vivo biodistribution on animal tissue sections through β-particles detection. Film autoradiography has progressively been replaced by digital β-imagers capable of high sensitivity, real-time imaging and activity counting for absolute quantification of radioactive compounds in tissue sections. After the discovery of the tumor heterogeneity phenomenon, research efforts for characterizing cell heterogeneity have been at the heart of oncology research, aiming at a better understanding of the causes and progression of the disease. This new perspective has also allowed for cell-targeting drugs, and radically changed both sample sizes and radiotracer activities. In this context, Medica-Plus, a transversal project gathering biologists, microfluidics specialists and detector developers, intends to perform quantification of low dose 3H- or 14C-labelled drugs inside single cells. This article reports preliminary results obtained with a prototype detector measuring tritium-generated signal.

241 Am-Be source abstract A measurement campaign has been carried out recently to provide the source intensity and the reference spectra around a neutron irradiation facility based on 241 Am-Be radionuclide source, using the UAB Bonner Sphere Spectrometer. This facility, which consists of a bunker, a container/shielding for the source and an irradiation device that uses an automated remote-controlled system for the source positioning and rotating during the dosimeter irradiation, is intended to be routinely used to check the response of passive dosimeters, namely those based on photo-stimulated imaging plates and solid-state nuclear track detectors. The measurement results, in terms of neutron spectra and global dosimetric quantities (i.e., fluence and ambient dose equivalent rates) at different distances with respect to the 241 Am-Be source, were compared with Monte Carlo simulations using the MCNPX code and a good agreement was observed. An estimation of the un-scattered neutron spectrum directly emitted from the 241 Am-Be source is given as well.

The RaMsEs group (Radioprotection et Mesures Environnementales) is working on a new compact device for operational neutron dosimetry. The electronic part of the detector is made of an integrated active pixel sensor, originally designed for tracking in particle physics. This device has useful features, including a high detection efficiency for charged particles, a good radiation resistance, a high readout speed and a low power consumption. Moreover, because of the thinness of the active layer, these CMOS sensors have low sensitivity to γ - rays , which is an attractive feature for neutron issues. In order to determine the γ response of the sensor, measurements have been carried out with a γ source of 60Co (1.17 MeV and 1.33 MeV). Other experiments have been performed with a fast neutron source of AmBe. We demonstrate the good discrimination between recoil protons from fast neutrons and from γ - background . Our results show that with an appropriate threshold, most γ - rays that generate photoelectrons can be removed from detection.

International audience; Polyallyl diglycol carbonate can be polymerized to make solid-state nuclear track detectors, type PN3, that are widely used for neutron dosimetry. Neutrons are detected by the damage trails created by recoil nuclei of the PN3 constituent atoms that are subsequently revealed by either a suitable chemical etching (CE) or electrochemical etching (ECE) process. On the basis of calibration exposures, track density can be related to neutron dose equivalent. The dose equivalent response and the detection level depend on detector material, nature and thickness of the radiator, energy and angle of incidence of the neutron, and the etching process. An automated ECE and reading system has been developed in RaMsEs laboratory. We compare the PN3 neutron dose equivalent response to 241Am–Be neutrons without radiator for both CE and ECE

We describe a fully standalone compact electronic monitor for atmospheric 222 Rn, based on a new CMOS system-on-chip. The electronic board consists of three AlphaRad CMOS chips running in parallel, and it includes a numeric block for data treatment based on a Xilinx programmable gate array. In addition to classical tests (passive detection in a calibrated radon chamber), we present the first results with active collection of radon progeny present as aerosols.

International audience; A CMOS active pixel sensor, originally designed for the tracking of minimum ionising charged particles in high-energy physics, has been recently used for the detection of fast neutrons. Data were taken at the IRSN Cadarache facility with a 241Am–Be ISO source and a polyethylene radiator. A high-intrinsic efficiency (1.2 x 10–3) has been obtained. It is in good agreement with both calculations and a MCNPX Monte Carlo simulation. This experiment paves the way for a fully electronic personal neutron dosemeter

Dans ce travail sont presentees quelques activites des groupes SADVI (Service d’Application des Detecteurs Visuels), LAM (Laboratoire d’Analyses et de Mesures) et RaMsEs (Radioprotection et Mesures environnementales) qui se sont succedes a l’IPHC de Strasbourg ces dernieres annees. Les resultats concernent : la R&D en metrologie des rayonnements ionisants, les applications des detecteurs solides de traces, les emulsions nucleaires en biologie spatiale, la thermoluminescence pour la datation archeologique, la dosimetrie neutron et les mesures de la radioactivite dans l’environnement par spectrometrie α , β et γ .

A CMOS active pixel sensor, originally designed for the tracking of minimum ionizing particles in high energy physics, has been recently used for the detection of fast neutrons. Data were taken at the French neutron reference facility (IRSN, Cadarache) with an Am-Be source and a polyethylene radiator. A high intrinsic efficiency ( 1.6 × 10 - 3 ) has been obtained, which is compatible with results from calculations and Monte Carlo simulations. This experiment paves the way for a fully electronic personal neutron dosemeter.

The development of pixel CMOS sensors for particle tracking in high energy physics has led to promising applications for dosimetry. We present the last results in electronic monitoring of atmospheric radon with the new system-on-chip AlphaRad, as well as highly efficient detection of fast neutrons with a megapixel Active Pixel Sensor of the MIMOSA generation.

Matched controls are used to identify differences in facial morphology related to the severe crowding in patients treated with serial extraction or early extraction of bicuspids.

The persistence and biotoxicity of nonylphenol, a mixture of monoalkyl phenols that is found in relatively high concentrations in sewage sludge, were studied in an incubation experiment with a reconstituted soil system (compost + sandstone). The effect of nonylphenol (100 and 1000 ppm) on CO2 evolution and biomass ATP were monitored. Nonylphenol depressed CO2 production significantly only at high concentrations [1000 ppm 4-nonylphenol (4-NP)]. Biomass ATP declined progressively after the 5th day. At 100 ppm no toxic effects were detected. After a lag phase, nonylphenol disappeared readily upon incubation at the lower concentration (100 ppm), but persisted at high levels (1000 ppm). The persistence of 4-nonylphenol increased under aseptic conditions. The chromatogram profile of 4-NP changed over time, indicating that some of the isomers are more easily degraded than others.