The Decontamination of 137Cs Contaminated Concrete Using Electrokinetic Phenomena and Ionic Salt Washes in Nuclear Energy Contexts

his work describes the first known use of electrokinetic treatments and ionic salt washes to remediate concrete contaminated with 137Cs. A series of experiments were performed on concrete samples, contaminated with K+ and 137Cs, using a bespoke migration cell and an applied electric field (60 V potential gradient and current limit of 35 mA). Additionally, two samples were treated with an ionic salt wash (≤ 400 mol m-3 of KCl) alongside the electrokinetic treatment. The results show that the combined treatment produces removal efficiencies three times higher (>60%) than the electrokinetic treatment alone and that the decontamination efficiency appears to be proportional to the initial degree of contamination. Furthermore, the decontamination efficiencies are equivalent to previous electrokinetic studies that utilised hazardous chemical enhancement agents demonstrating the potential of the technique for use on nuclear licensed site. The results highlight the relationship between the initial contamination concentration within the concrete and achievable removal efficiency of electrokinetic treatment and other treatments. This information would be useful when selecting the most appropriate decontamination techniques for particular contamination scenarios

Radiometric detection of non-radioactive caesium flux using displaced naturally abundant potassium

We report on a method that allows for the radiometric detection of non-radioactive caesium by the measurement of potassium ions displaced from an ion exchange barrier. Electrokinetic transport of K+ and Cs+ through concrete samples was measured using a bespoke scintillation detector to monitor electrolyte concentrations. Results show experimental ionic flux and diffusion parameters of non-active caesium (~1 × 10−5 mol m−3) were consistent with those recorded for potassium and also with values reported in relevant literature. This work demonstrates a novel concept that can be applied to proof-of-concept studies that help develop the next generation of nuclear decommissioning technologies

Finding the depth of radioactivity in construction materials

A key challenge in disposing of nuclear legacy facilities and planning a new nuclear plant is how to assess the extent or likelihood of radioactive contamination in construction materials and the ground. This paper summarises the status of two techniques based on the analysis of emitted radiation from materials that comprise such structures, and describes how this analysis can be used to infer the depth of contamination without the need to penetrate the structure or to destroy it in the process. Two experimental facilities have been developed to test the efficacy of these techniques, and data are provided for the most widespread contaminant experienced in the sector: caesium-137. Finally, the influence on the technique of the likely variety of silica-based media to be encountered in the nuclear industry is described, together with a summary of challenges to be addressed in future research

Imaging of Fast Neutrons and Gamma Rays from 252Cf in a Heavily Shielded Environment

A 75 MBq 252Cf neutron source stored inside a steel water tank was characterised using a compact fast-neutron and gamma-ray imaging system based on a passive slot modulation imaging technique. Radiation fields were imaged from a variety of positions with the source in the stored position (located in the center of the water tank: high shielding) and in the exposed position (located at the edge of the water tank: low shielding). It was possible to locate the 252Cf source in each image and gain additional information of the neutron and gamma-ray fields in the local environment including scatter contributions from the steel shield, floor and walls in proximity to the source. A long exposure image of the stored source, taken over thirty days, identified the location of the radiation source from the low dose ( < 1 μ Sv / h ) field penetrating through 46 cm of water in the storage tank

Time-of-Flight Spectroscopy of 252 Cf Spontaneous Fission Neutrons:Influences of Detector Voltage, Pulse-Shape Discrimination and Shielding

Experimental measurements to explore the effect of detector voltage, pulse-shape discrimination (PSD) threshold and detector shielding on time-of-flight measurements of the 252Cf neutron spectrum made with organic scintillation detectors are described. It is found that detector voltage has a major effect, whilst changing the PSD threshold and shielding the detectors to optimize sensitivity to the desired gamma-neutron correlation results in a small effect

Point-spread Analysis of γ-ray/depth Spectra for Borehole Monitoring Applications

An approach to the analysis of γ-ray spectra that might arise as depth profiles from the characterization of radioactivity in boreholes is described. A borehole logging probe, ‘ABACUS’, has been designed and constructed which comprises a cerium bromide detector and a built-in multichannel analyzer. This has been tested in a bespoke, laboratory-based testbed built to replicate the borehole environment. An established, semi-empirical model has been applied data arising from the cerium bromide scintillation detector to extract the number of counts under the photopeak from each of the resulting γ-ray spectra (in this case the 662 keV line from 137 Cs) associated with each depth position, and which also enables this information to be isolated from other contributions such as background and the Compton continuum. A complementary approach has been adopted to process the asymmetric and non-Gaussian trend that concerns the photopeak count as a function of depth in the borehole testbed for a given depth profile, when the testbed is subject to the activity provided by a sealed, 137 Cs source. This comprises a modified, Moffat point-spread function. The Moffat function is a continuous probability distribution based upon the Lorentzian distribution. Its particular importance is due to its ability to reconstruct point spread functions that comprise wings that cannot be reproduced accurately by either a Gaussian or Lorentzian function. This application of the Moffat formalism to radioactive contamination assessment profiles enables an effective and accurate assessment to be made of the position of localized radioactivity in the testbed wall

Enrichment measurement by passive γ-ray spectrometry of uranium dioxide fuel pellets using a europium-doped, strontium iodide scintillator

The performance of a europium-doped strontium iodide scintillator for uranium enrichment measurement of a variety of sintered uranium dioxide fuel pellets is described and compared to that of caesium iodide and sodium iodide. Enrichment has been determined via passive γ-ray spectrometry of the 186 keV line from uranium-235 using gross count, net count, and peak ratio analyses. The 38 mm Ø x 38 mm strontium iodide crystal demonstrates superior energy resolution (3.43 ± 0.03% at 662 keV) and competitive detection efficiency for its size in the energy range of interest for uranium enrichment analysis (<250 keV). It demonstrates better χ v 2 and coefficient of determination values than caesium iodide and sodium iodide when measuring uranium enrichment using the gross- and net-count from the 186 keV emission. It is shown to have the least measurement variance of the three scintillators studied in determining the uranium enrichment of pellets in a blind test, with a relative error comparative to sodium iodide and smaller than caesium iodide. This research heralds the potential of strontium iodide in passive γ-ray uranium enrichment applications

Digital twin challenges and opportunities for nuclear fuel manufacturing applications

There have been a number of digital twin (DT) frameworks proposed for multiple disciplines in recent years. However, there is a need to develop systematic methodologies to improve our ability to produce DT solutions for the nuclear fuel industry considering specific requirements and conditions exclusive to the nuclear fuel manufacturing cycle. A methodology tailored for nuclear fuel production is presented in this paper. Due to the nature of the chemical processes involved in fuel manufacturing, we highlight the importance of using a combination of physics-based and data-driven modelling. We introduce key technologies for DT construction and the technical challenges for DT are discussed. Furthermore, we depict typical application scenarios, such as key stages of the nuclear manufacturing cycle. Finally, a number of technology issues and research questions related to DT and nuclear fuel manufacturing are identified

What factors in rural and remote extended clinical placements may contribute to preparedness for practice, from the perspective of students and clinicians?

What factors in rural and remote extended clinical placements may contribute to preparedness for practice, from the perspective of students and clinicians? Michele Daly, David Perkins, Koshila Kumar, Chris Roberts and Malcolm Moore Background: Community based rural education opportunities have expanded in Australia, attracting more medical students to placements in rural and remote settings. Aim: To identify the factors in an integrated, community engaged rural placement that may contribute to preparedness for practice (P4P), from the perspective of students and clinicians Methods: Forty two semi-structured interviews with medical students, supervisors and clinicians analysed thematically. Results: Opportunities for clinical learning, personal and professional development and cultural awareness were reported by students and clinicians as key factors that contribute to preparedness for practice. Potential barriers in rural and remote settings included geographical and academic isolation, perceived educational risk and differing degrees of program engagement. Conclusions: A longitudinal clinical placement in a rural setting may enable development of enhanced competencies leading to P4P. A rural setting can help provide a unique experience through hands-on learning, enhanced personal and professional development opportunities and observation of the cultural and contextual impact on health

Sea-breeze dynamics and convection initiation: the influence of convective parameterization in weather and climate model biases

There are some long-established biases in atmospheric models that originate from the representation of tropical convection. Previously, it has been difficult to separate cause and effect because errors are often the result of a number of interacting biases. Recently, researchers have gained the ability to run multiyear global climate model simulations with grid spacings small enough to switch the convective parameterization off, which permits the convection to develop explicitly. There are clear improvements to the initiation of convective storms and the diurnal cycle of rainfall in the convection-permitting simulations, which enables a new process-study approach to model bias identification. In this study, multiyear global atmosphere-only climate simulations with and without convective parameterization are undertaken with the Met Office Unified Model and are analyzed over the Maritime Continent region, where convergence from sea-breeze circulations is key for convection initiation. The analysis shows that, although the simulation with parameterized convection is able to reproduce the key rain-forming sea-breeze circulation, the parameterization is not able to respond realistically to the circulation. A feedback of errors also occurs: the convective parameterization causes rain to fall in the early morning, which cools and wets the boundary layer, reducing the land–sea temperature contrast and weakening the sea breeze. This is, however, an effect of the convective bias, rather than a cause of it. Improvements to how and when convection schemes trigger convection will improve both the timing and location of tropical rainfall and representation of sea-breeze circulations