On the use of pixelated plastic scintillator and silicon photomultipliers array for coded aperture gamma-neutron imaging

International audienceWe report the investigations made on the use of pixelated plastic scintillator (PS) and silicon photomultipliers (SiPMs) array applied to coded aperture gamma-neutron imaging. Specifically, verification of the ability of a multiplexing readout to discriminate and localize neutron interactions was studied. In its intended configuration, the gamma-neutron imager design consists of a coded aperture aligned with a matrix of 12 × 12 PS each coupled to a SiPM. The coded aperture is a rank 7 modified uniformly redundant array (MURA), composed of 1.2 cm of tungsten, with a surface area of 100.4 mm × 100.4 mm and placed at 5 cm from the detector. The pixelated PS is composed of polystyrene and standard fluorophores (20 wt% PPO, 0.03 wt% POPOP) loaded with a lithium carboxylate (Li α -valerate), which allows the triple discrimination between thermal neutrons, fast neutrons, and photons. Each pixel of PS has a dimension of 3.6 mm × 3.6 mm × 3.6 mm and they are separated from each other by 0.6 mm of polytetrafluoroethylene (PTFE). The photonic and electronic readout consists of the ArrayC-30035-144P SiPM from SensL, Cork, Ireland, connected to the diode coupled charge division readout from AiT. First, this neutron imager design was modeled and simulated using the MCNP6 Monte Carlo code. The encoding capability, field of view, and spatial resolution of the neutron imager were therefore evaluated by simulation. Then, we detailed the experimental setups implemented to demonstrate the feasibility of coupling pixelated PS to SiPM to localize radioactive sources and showed the results obtained. Finally, based on this position-sensitive gamma-neutron detector, a gamma-neutron imager was prototyped and tested

Neutron/gamma discrimination and localization with pixelated plastic scintillators and SiPM dedicated multiplexing readout

International audienceThe development of instruments for measuring radioactivity and more particularly systems for characterizing and locating particles is an important issue in many fields, such as nuclear industry (gamma-neutron imaging and radiography) and medicine (scintigraphy, SPECT and PET), high-energy physics (tracking and calorimetry) and astrophysics (space observatory). These areas are not exempt from the need of technologies to reduce size and energy consumption along with the increase of durability. In this context, the use of silicon photomultipliers (SiPM), instead of a photomultiplier tube, addresses to these issues thanks to its compactness, modularity, low cost and robustness. Moreover, their assembly in a matrix form allows the position of interactions to be measured.The aim of this work is to develop a compact, scalable and position-sensitive neutron detector with high sensitivity based on a pixelated plastic scintillator (PS) and a SiPM array coupled with a multiplexing readout. The chemical composition of manufactured PS was chosen for its gamma/neutron discrimination abilities. The SiPM array used in these experiments is from SensL, the ArrayC-30035-16P . In order to minimize the number of channels to be digitized, we employed the multiplexing readout fro

Advancements in Gd-based neutron detection: γ−γ\gamma - \gamma coincidence approach

International audienceCEA LIST is working on the development of a high-sensitivity thermal neutron counter, based on the insertion of gadolinium in spherical plastic scintillators. As the radiation sensor comprises one or several volumes of scintillating polymers, it is, by nature, sensitive to both neutron and gamma radiations. This property allows the development of a versatile detector, provided that it is possible to algorithmically separate the signature of both types of radiations. The technologically building brick is, moreover, to be implemented in a transportable (<15 kg) system, handled by a first intervention task force in an exposed area. The aim of this paper is to study, both through Monte Carlo simulation and experimentally, an algorithmic architecture of the measurement chain discriminating neutron and gamma events. The presentation is subdivided in three main sections. First, we detail a comparative study between the outputs of a numerical modeling tool, developed to simulate the total response of the sensor to varying radiation sources and the results of a series of experiments carried out in a controlled environment. Second, we describe the building and numerical pre-validation of a simulation code dedicated to the study of consolidated algorithmic architecture, namely γ–γ quasi-coincidence on two adjacent plastic scintillators. Third, we comment on an experimental study of γ–γ quasi-coincidence, Gd-based neutron detection and a comparison between the results and the estimated of the numerical study. We conclude with the presentation of first estimates of neutron sensitivity), gamma-background vulnerability, and n/γ discrimination ratio for the scaled and assessed, material and algorithmic architectures

The use of alpha particle tagged neutrons for the inspection of objects on the sea floor for the presence of explosives

International audienceA system using a neutron sensor installed within a Remotely Operated Vehicle (ROV) for underwater inspection has been developed. The system can inspect objects for the presence of threat materials, such as explosives and chemical agents, by using alpha particle tagged neutrons from a sealed tube d + t neutron generator to produce characteristic gamma rays within the interrogated object. Here we show that the measured gamma spectra for commonly found ammunition charged with TNT explosives are dominated by C, O and Fe peaks enabling the underwater determination of explosives inside an ammunition shell

Development of a synthetic single crystal diamond dosimeter for dose measurement of clinical proton beams

International audienceThe scope of this work was to develop a synthetic single crystal diamond dosimeter (SCDD-Pro) for accurate relative dose measurements of clinical proton beams in water. Monte Carlo simulations were carried out based on the MCNPX code in order to investigate and reduce the dose curve perturbation caused by the SCDD-Pro. In particular, various diamond thicknesses were simulated to evaluate the influence of the active volume thickness (e(AV)) as well as the influence of the addition of a front silver resin (250 µm in thickness in front of the diamond crystal) on depth-dose curves. The simulations indicated that the diamond crystal alone, with a small eAV of just 5 µm, already affects the dose at Bragg peak position (Bragg peak dose) by more than 2% with respect to the Bragg peak dose deposited in water. The optimal design that resulted from the Monte Carlo simulations consists of a diamond crystal of 1 mm in width and 150 µm in thickness with the front silver resin, enclosed by a water-equivalent packaging. This design leads to a deviation between the Bragg peak dose from the full detector modeling and the Bragg peak dose deposited in water of less than 1.2%. Based on those optimizations, an SCDD-Pro prototype was built and evaluated in broad passive scattering proton beams. The experimental evaluation led to probed SCDD-Pro repeatability, dose rate dependence and linearity, that were better than 0.2%, 0.4% ( in the 1.0-5.5 Gy min(-1) range) and 0.4% ( for dose higher than 0.05 Gy), respectively. The depth-dose curves in the 90-160 MeV energy range, measured with the SCDD-Pro without applying any correction, were in good agreement with those measured using a commercial IBA PPC05 plane-parallel ionization chamber, differing by less than 1.6%. The experimental results confirmed that this SCDD-Pro is suitable for measurements with standard electrometers and that the depth-dose curve perturbation is negligible, with no energy dependence and no significant dose rate dependence

Long length SPNDs and Distributed Optical Fiber Sensors for Severe Accident remote monitoring & their contribution to Nuclear Safety in the post-Fukushima context

International audienceThe Fukushima-Daiichi nuclear accident of March 2011, and the subsequent loss of internal power supplies after the NPP (Nuclear Power Plant) water flooding caused by the tsunami, leaving the operator TEPCO with almost no information from the reactor pits, demonstrates that safety must always prevail.Accordingly, the French public authorities initiated the RSNR research program, to stimulate and fund new R&D projects to improve the safety of nuclear reactors in service and those of future NPPs.The DISCOMS project (Distributed Sensing for Corium Monitoring and Safety) aimed at developing and testing innovative and passive sensors dedicated to Nuclear Safety, namely an instrumented pole equipped with long length SPNDs (Self-Powered Neutron Detectors)-Thermocouple poles, and Distributed Optical Fiber Sensors, to be installed ex-core in both the reactor pit and concrete floor. The sensors, remotely operated from a safe place, will not only provide additional information during the Severe Accident, but also in post-accidental situation, even in case of loss of all power supplies.The modelling of a 60 year normal operation followed by a Severe Accident for two generations of reactors (Gen II, Gen III) permitted to demonstrate that ex-core long length SPNDs can identify different scenarios: reactor shut down, Normal Operation, Severe Accident without corium relocation, and Severe Accident with corium pouring on the concrete floor.Long length SPNDs were designed and manufactured, along with their electronics, to measure low currents ranging from 1 pA to 100 nA collected under radiations, and qualified in a research reactor with fluxes compliant with modelled scenarios.Optical Fibers Sensor cables are devoted to monitor the Molten Core - Concrete Interaction (MCCI): temperature and strain profiles can be provided in the concrete depth by embedded cables, as a result of using the Raman DTS, Brillouin and Rayleigh OFDR reflectometry techniques, based on the analysis of the backscattered light in single-mode optical fibers, for distributed measurements potentially up to 1000°C with Brillouin instrumentations. Additionally, such sensor cables can be used as fuses with telecom or photon counting OTDRs to detect corium vicinity.Sensor cables and radiation resistant optical fibers have been selected and tested to comply with the radiation conditions in the reactor pits as depicted by the modelling.A final MCCI experiment with prototypical corium, performed at the VULCANO CEA facility, involving also two instrumented SPNDs-Thermocouple poles, has demonstrated the ability of both kinds of sensors and corresponding instrumentations to deliver useful information about the corium status and its progression through the concrete

Long length SPNDs and Distributed Optical Fiber Sensors for Severe Accident remote monitoring & their contribution to Nuclear Safety in the post-Fukushima context

International audienceThe Fukushima-Daiichi nuclear accident of March 2011, and the subsequent loss of internal power supplies after the NPP (Nuclear Power Plant) water flooding caused by the tsunami, leaving the operator TEPCO with almost no information from the reactor pits, demonstrates that safety must always prevail.Accordingly, the French public authorities initiated the RSNR research program, to stimulate and fund new R&D projects to improve the safety of nuclear reactors in service and those of future NPPs.The DISCOMS project (Distributed Sensing for Corium Monitoring and Safety) aimed at developing and testing innovative and passive sensors dedicated to Nuclear Safety, namely an instrumented pole equipped with long length SPNDs (Self-Powered Neutron Detectors)-Thermocouple poles, and Distributed Optical Fiber Sensors, to be installed ex-core in both the reactor pit and concrete floor. The sensors, remotely operated from a safe place, will not only provide additional information during the Severe Accident, but also in post-accidental situation, even in case of loss of all power supplies.The modelling of a 60 year normal operation followed by a Severe Accident for two generations of reactors (Gen II, Gen III) permitted to demonstrate that ex-core long length SPNDs can identify different scenarios: reactor shut down, Normal Operation, Severe Accident without corium relocation, and Severe Accident with corium pouring on the concrete floor.Long length SPNDs were designed and manufactured, along with their electronics, to measure low currents ranging from 1 pA to 100 nA collected under radiations, and qualified in a research reactor with fluxes compliant with modelled scenarios.Optical Fibers Sensor cables are devoted to monitor the Molten Core - Concrete Interaction (MCCI): temperature and strain profiles can be provided in the concrete depth by embedded cables, as a result of using the Raman DTS, Brillouin and Rayleigh OFDR reflectometry techniques, based on the analysis of the backscattered light in single-mode optical fibers, for distributed measurements potentially up to 1000°C with Brillouin instrumentations. Additionally, such sensor cables can be used as fuses with telecom or photon counting OTDRs to detect corium vicinity.Sensor cables and radiation resistant optical fibers have been selected and tested to comply with the radiation conditions in the reactor pits as depicted by the modelling.A final MCCI experiment with prototypical corium, performed at the VULCANO CEA facility, involving also two instrumented SPNDs-Thermocouple poles, has demonstrated the ability of both kinds of sensors and corresponding instrumentations to deliver useful information about the corium status and its progression through the concrete

Long length SPNDs and Distributed Optical Fiber Sensors for Severe Accident remote monitoring & their contribution to Nuclear Safety in the post-Fukushima context

International audienceThe Fukushima-Daiichi nuclear accident of March 2011, and the subsequent loss of internal power supplies after the NPP (Nuclear Power Plant) water flooding caused by the tsunami, leaving the operator TEPCO with almost no information from the reactor pits, demonstrates that safety must always prevail.Accordingly, the French public authorities initiated the RSNR research program, to stimulate and fund new R&D projects to improve the safety of nuclear reactors in service and those of future NPPs.The DISCOMS project (Distributed Sensing for Corium Monitoring and Safety) aimed at developing and testing innovative and passive sensors dedicated to Nuclear Safety, namely an instrumented pole equipped with long length SPNDs (Self-Powered Neutron Detectors)-Thermocouple poles, and Distributed Optical Fiber Sensors, to be installed ex-core in both the reactor pit and concrete floor. The sensors, remotely operated from a safe place, will not only provide additional information during the Severe Accident, but also in post-accidental situation, even in case of loss of all power supplies.The modelling of a 60 year normal operation followed by a Severe Accident for two generations of reactors (Gen II, Gen III) permitted to demonstrate that ex-core long length SPNDs can identify different scenarios: reactor shut down, Normal Operation, Severe Accident without corium relocation, and Severe Accident with corium pouring on the concrete floor.Long length SPNDs were designed and manufactured, along with their electronics, to measure low currents ranging from 1 pA to 100 nA collected under radiations, and qualified in a research reactor with fluxes compliant with modelled scenarios.Optical Fibers Sensor cables are devoted to monitor the Molten Core - Concrete Interaction (MCCI): temperature and strain profiles can be provided in the concrete depth by embedded cables, as a result of using the Raman DTS, Brillouin and Rayleigh OFDR reflectometry techniques, based on the analysis of the backscattered light in single-mode optical fibers, for distributed measurements potentially up to 1000°C with Brillouin instrumentations. Additionally, such sensor cables can be used as fuses with telecom or photon counting OTDRs to detect corium vicinity.Sensor cables and radiation resistant optical fibers have been selected and tested to comply with the radiation conditions in the reactor pits as depicted by the modelling.A final MCCI experiment with prototypical corium, performed at the VULCANO CEA facility, involving also two instrumented SPNDs-Thermocouple poles, has demonstrated the ability of both kinds of sensors and corresponding instrumentations to deliver useful information about the corium status and its progression through the concrete

Long length SPNDs and Distributed Optical Fiber Sensors for Severe Accident remote monitoring and their contribution to Nuclear Safety in the post-Fukushima context

International audienceThe Fukushima-Daiichi nuclear accident of March 2011, and the subsequent loss of internal power supplies after the NPP (Nuclear Power Plant) water flooding caused by the tsunami, leaving the operator TEPCO with almost no information from the reactor pits, demonstrates that safety must always prevail. Accordingly, the French public authorities initiated the RSNR research program, to stimulate and fund new R&D projects to improve the safety of nuclear reactors in service and those of future NPPs. The DISCOMS project (Distributed Sensing for Corium Monitoring and Safety) aimed at developing and testing innovative and passive sensors dedicated to Nuclear Safety, namely an instrumented pole equipped with long length SPNDs (Self-Powered Neutron Detectors)-Thermocouple poles, and Distributed Optical Fiber Sensors, to be installed ex-core in both the reactor pit and concrete floor. The sensors, remotely operated from a safe place, will not only provide additional information during the Severe Accident, but also in post-accidental situation, even in case of loss of all power supplies.The modelling of a 60 year normal operation followed by a Severe Accident for two generations of reactors (Gen II, Gen III) permitted to demonstrate that ex-core long length SPNDs can identify differentscenarios: reactor shut down, Normal Operation, Severe Accident without corium relocation, and Severe Accident with corium pouring on the concrete floor. Long length SPNDs were designed and manufactured, along with their electronics, to measure low currents ranging from 1 pA to 100 nA collected under radiations, and qualified in a research reactor with fluxes compliant with modelled scenarios. Optical Fibers Sensor cables are devoted to monitor the Molten Core – Concrete Interaction (MCCI): temperature and strain profiles can be provided in the concrete depth by embedded cables, as a result ofusing the Raman DTS, Brillouin and Rayleigh OFDR reflectometry techniques, based on the analysis of the backscattered light in single-mode optical fibers, for distributed measurements potentially up to1000°C with Brillouin instrumentations. Additionally, such sensor cables can be used as fuses with telecom or photon counting OTDRs to detect corium vicinity.Sensor cables and radiation resistant optical fibers have been selected and tested to comply with the radiation conditions in the reactor pits as depicted by the modelling.A final MCCI experiment with prototypical corium, performed at the VULCANO CEA facility, involving also two instrumented SPNDs-Thermocouple poles, has demonstrated the ability of both kinds of sensors and corresponding instrumentations to deliver useful information about the corium status and its progression through the concrete

Long length SPNDs and Distributed Optical Fiber Sensors for Severe Accident remote monitoring and their contribution to Nuclear Safety in the post-Fukushima context

International audienceThe Fukushima-Daiichi nuclear accident of March 2011, and the subsequent loss of internal power supplies after the NPP (Nuclear Power Plant) water flooding caused by the tsunami, leaving the operator TEPCO with almost no information from the reactor pits, demonstrates that safety must always prevail. Accordingly, the French public authorities initiated the RSNR research program, to stimulate and fund new R&D projects to improve the safety of nuclear reactors in service and those of future NPPs. The DISCOMS project (Distributed Sensing for Corium Monitoring and Safety) aimed at developing and testing innovative and passive sensors dedicated to Nuclear Safety, namely an instrumented pole equipped with long length SPNDs (Self-Powered Neutron Detectors)-Thermocouple poles, and Distributed Optical Fiber Sensors, to be installed ex-core in both the reactor pit and concrete floor. The sensors, remotely operated from a safe place, will not only provide additional information during the Severe Accident, but also in post-accidental situation, even in case of loss of all power supplies.The modelling of a 60 year normal operation followed by a Severe Accident for two generations of reactors (Gen II, Gen III) permitted to demonstrate that ex-core long length SPNDs can identify differentscenarios: reactor shut down, Normal Operation, Severe Accident without corium relocation, and Severe Accident with corium pouring on the concrete floor. Long length SPNDs were designed and manufactured, along with their electronics, to measure low currents ranging from 1 pA to 100 nA collected under radiations, and qualified in a research reactor with fluxes compliant with modelled scenarios. Optical Fibers Sensor cables are devoted to monitor the Molten Core – Concrete Interaction (MCCI): temperature and strain profiles can be provided in the concrete depth by embedded cables, as a result ofusing the Raman DTS, Brillouin and Rayleigh OFDR reflectometry techniques, based on the analysis of the backscattered light in single-mode optical fibers, for distributed measurements potentially up to1000°C with Brillouin instrumentations. Additionally, such sensor cables can be used as fuses with telecom or photon counting OTDRs to detect corium vicinity.Sensor cables and radiation resistant optical fibers have been selected and tested to comply with the radiation conditions in the reactor pits as depicted by the modelling.A final MCCI experiment with prototypical corium, performed at the VULCANO CEA facility, involving also two instrumented SPNDs-Thermocouple poles, has demonstrated the ability of both kinds of sensors and corresponding instrumentations to deliver useful information about the corium status and its progression through the concrete