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Beaumont J.S.,Lancaster University | Mellor M.P.,Createc Ltd. | Villa M.,Vienna University of Technology | Joyce M.J.,Lancaster University | Joyce M.J.,Hybrid Instruments Ltd
Nature Communications | Year: 2015

Knowledge of the neutron distribution in a nuclear reactor is necessary to ensure the safe and efficient burnup of reactor fuel. Currently these measurements are performed by in-core systems in what are extremely hostile environments and in most reactor accident scenarios it is likely that these systems would be damaged. Here we present a compact and portable radiation imaging system with the ability to image high-intensity fast-neutron and gamma-ray fields simultaneously. This system has been deployed to image radiation fields emitted during the operation of a TRIGA test reactor allowing a spatial visualization of the internal reactor conditions to be obtained. The imaged flux in each case is found to scale linearly with reactor power indicating that this method may be used for power-resolved reactor monitoring and for the assay of ongoing nuclear criticalities in damaged nuclear reactors. © 2015 Macmillan Publishers Limited.


Lavietes A.,International Atomic Energy Agency | Plenteda R.,International Atomic Energy Agency | Mascarenhas N.,International Atomic Energy Agency | Cronholm L.M.,International Atomic Energy Agency | And 4 more authors.
IEEE Nuclear Science Symposium Conference Record | Year: 2012

The IAEA, in collaboration with the Joint Research Center (Ispra, IT) and Hybrid Instruments (UK), is developing a liquid scintillator-based neutron coincidence counting system to address a number of safeguards applications. Interest in this technology is increasing with the advent of high-flashpoint, nonhazardous scintillating fluids coupled with significant advances in signal processing electronics. Together, these developments have provided the enabling technologies to allow liquid scintillators to be implemented outside of a laboratory environment. Another important aspect of this detector technology is that it can be used with the current installed infrastructure of safeguards assay instruments and data acquisition electronics. It is also an excellent candidate for the replacement of 3He-based systems in many applications. As such, a comparison to an existing 3He-based system will be presented to contrast the differences and benefits for several applications. This paper will describe the experiments and associated modeling activities engaged to carefully characterize the detection system and refine the models. The latest version of MCNPX-PoliMi Monte Carlo modeling code was used to address the specific requirements of liquid scintillators. Additionally, this development activity has driven the collaborative development with Hybrid Instruments of a high-performance pulse shape discriminator (PSD) unit. Specific applications will be described with particular emphasis on those in which liquid scintillators provide immediate benefit over traditional detection methods. © 2012 IEEE.


Joyce M.J.,Lancaster University | Aspinall M.D.,Hybrid Instruments Ltd | Cave F.D.,Hybrid Instruments Ltd | Lavietes A.,International Atomic Energy Agency | Lavietes A.,Lawrence Livermore National Laboratory
IEEE Transactions on Nuclear Science | Year: 2014

In recent years, real-time neutron/γ-ray pulse-shape discrimination has become feasible for use with scintillator-based detectors that respond extremely quickly, on the order of 25 ns in terms of pulse width, and their application to a variety of nuclear material assays has been reported. For the in-situ analysis of nuclear materials, measurements are often based on the multiplicity assessment of spontaneous fission events. An example of this is the 240Pueff assessment stemming from long-established techniques developed for 3He-based neutron coincidence counters when 3He was abundant and cheap. However, such measurements when using scintillator detectors can be plagued by low detection efficiencies and low orders of coincidence (often limited to triples) if the number of detectors in use is similarly limited to 3 or 4. Conversely, an array of > 10 detector modules arranged to optimize efficiency and multiplicity sensitivity, shifts the emphasis in terms of performance requirement to the real-time digital analyzer and, critically, to the scope remaining in the temporal processing window of the firmware in these systems. In this paper we report on the design, development and commissioning of a custom-built, 16-channel real-time pulse-shape discrimination analyzer specified for the materials assay challenge summarized above. The analyzer incorporates 16 dedicated and independent high-voltage supplies along with 16 independent digital processing channels offering pulse-shape discrimination at a rate of 3 × 106 events per second. These functions are configured from a dedicated graphical user interface, and all settings can be adjusted on-the-fly with the analyzer effectively configured one-time-only (where desired) for subsequent plug-and-play connection, for example to a fuel bundle organic scintillation detector array. © 2014 IEEE.


Joyce M.J.,Lancaster University | Aspinall M.D.,Hybrid Instruments Ltd | Cave F.D.,Hybrid Instruments Ltd | Lavietes A.D.,International Atomic Energy Agency
IEEE Transactions on Nuclear Science | Year: 2012

Pulse-shape discrimination (PSD) in fast, organic scintillation detectors is a long-established technique used to separate neutrons and γ rays in mixed radiation fields. In the analogue domain the method can achieve separation in real time, but all knowledge of the pulses themselves is lost thereby preventing the possibility of any post- or repeated analysis. Also, it is typically reliant on electronic systems that are largely obsolete and which require significant experience to set up. In the digital domain, PSD is often more flexible but significant post-processing has usually been necessary to obtain neutron/γ-ray separation. Moreover, the scintillation media on which the technique relies usually have a low flashpoint and are thus deemed hazardous. This complicates the ease with which they are used in industrial applications. In this paper, results obtained with a new portable digital pulse-shape discrimination instrument are described. This instrument provides real-time, digital neutron/γ-ray separation whilst preserving the synchronization with the time-of-arrival for each event, and realizing throughputs of 3 × 10 6 events per second. Furthermore, this system has been tested with a scintillation medium that is non-flammable and not hazardous. © 2012 IEEE.


Joyce M.J.,Lancaster University | Aspinall M.D.,Hybrid Instruments Ltd | Cave F.D.,Hybrid Instruments Ltd | Lavietes A.,International Atomic Energy Agency
2013 3rd International Conference on Advancements in Nuclear Instrumentation, Measurement Methods and Their Applications, ANIMMA 2013 | Year: 2013

In recent years, real-time neutron/γ-ray pulse-shape discrimination has become feasible for use with scintillator-based detectors that respond extremely quickly, on the order of 25 ns in terms of pulse width, and their application to a variety of nuclear material assays has been reported. For the in-situ analysis of nuclear materials, measurements are often based on the multiplicity assessment of spontaneous fission events. An example of this is the 240Pueff assessment stemming from long-established techniques developed for 3He-based neutron coincidence counters when 3He was abundant and cheap. However, such measurements when using scintillator detectors can be plagued by low detection efficiencies and low orders of coincidence (often limited to triples) if the number of detectors in use is similarly limited to 3-4 detectors. Conversely, an array of >10 detector modules arranged to optimize efficiency and multiplicity sensitivity, shifts the emphasis in terms of performance requirement to the real-time digital analyzer and, critically, to the scope remaining in the temporal processing window of these systems. In this paper we report on the design, development and commissioning of a bespoke, 16-channel real-time pulse-shape discrimination analyzer specified for the materials assay challenge summarized above. The analyzer incorporates 16 dedicated and independent high-voltage supplies along with 16 independent digital processing channels offering pulse-shape discrimination at a rate of 3 × 106 events per second. These functions are configured from a dedicated graphical user interface, and all settings can be adjusted on-the-fly with the analyzer effectively configured one-time-only (where desired) for subsequent plug-and-play connection, for example to a fuel bundle organic scintillation detector array. © 2013 IEEE.

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