High-intensity power-resolved radiation imaging of an operational nuclear reactor

Abstract

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.

Real-Time Capabilities of a Digital Analyzer for Mixed-Field Assay Using Scintillation Detectors

“…In some cases, this is the difference between days of acquisition, terabytes of data, and many more hours of post-processing compared to a few hours of measurements and instantaneous results (e.g. [13]). …”

“…The controller includes an FPGA-based data acquisition card and custom-built analysis software developed in LabVIEW [7], [14]. 2) custommade de-randomizing electronics (Los Alamos National Laboratory, NM) connected to a JSR-15 multiplicity shift register (Canberra Industries Inc., CT) for the measurement of Uranium-235 enrichment in small samples of low-enriched triuranium octoxide [15], and 3) a bespoke 32-bit, 64-channel, binary counter with a serial PC interface (Lancaster University, UK) for reactor imaging [13] and neutron tomography using an isotropic source [16]. In addition, the commercially available multichannel Pulse Train Recorder (model: PTR-32) by the Institute of Isotopes (Hungarian Academy of Sciences or Energia, Budapest) is also fully compatible with the MFAx technology and offers an embedded de-randomizing function.…”

“…The technology has been used with a fast, organic liquid scintillator for imaging an operational TRIGA mark II nuclear reactor [13]. This study utilized a lightweight and portable system comprising of a single channel MFA, detector, collimator and equatorial mount [17], [18].…”

Stand-off nuclear reactor monitoring with neutron detectors for safeguards and non-proliferation applications

“…In the following, the feasibility of neutron detection for monitoring reactor fuel cycle activities is examined, at significant stand-off distances from a nuclear reactor. To date, there has been published work about using neutron detectors outside of reactor shielding for determining power density distribution within reactors, from escaping fast neutrons 8 . Although the preceding publication may anticipate this work, this work explicitly demonstrates how escaping fast neutrons detected as thermalized neutrons can be related to monitoring the fissile isotope inventory of a reactor core, for safeguards purposes; in particular, the stand-off neutron count rate per unit reactor power is proportional to a weighted sum of the fissile isotope inventory.…”

Imaging of fast neutrons and gamma rays from 252 Cf in a heavily shielded environment

“…Current methods of fuel debris assay include muon tomography, a method which has been used recently at Fukushima Daiichi [7], though, unlike a neutron imaging approach, there is no information about any stimulated fission re-40 actions occurring within the core containment. Fastneutron imaging has been used in high-dose fields to characterise the fission reaction within a nuclear reactor [8], making steps towards using this technology for re-actor decommissioning. The ability to confirm localised absence of neutron emitting materials is also practical for decommissioning purposes and may be applicable to some nuclear safeguards applications.…”