[en] Within the British nuclear inventory, metallic Intermediate Level Waste (ILW) is encapsulated in grout and stored in stainless steel drums. Based on recent inspections held in the relevant storage facilities (Sellafield, Cumbria), a proportion of these drums have exhibited considerable distortion, raising concerns about the long-term safety of the packages. Distortion may be caused by the generation of voluminous and potentially flammable substances resulting from metallic corrosion occurring within the drums' core. Potential oxygen influx in the event of steel fracture and consequently drum's failure could potentially cause release or even ignition of the encapsulated radioactive material. The mechanical degradation of the encapsulants (stainless steel and grout) induced from the progressive corrosion of the encapsulated metallic components (and the associated volume expansion) was investigated using both Finite Element Modelling (FEM) techniques as well as experimental trials. A parametric study using simplified 3D FE models was performed to determine their structural integrity under different scenarios. Synchrotron X-Ray tomography (XRT) was used to monitor the behaviour of miniaturized ILW drum-simulants, whilst the latter were subjected to controlled accelerated corrosion in situ. (authors)

[en] Whereas the increasing influence of technology within the nuclear industry can be seen by many as providing significant advancements and solutions across many areas of the sector - it can also be seen to conversely represent a considerable number of challenges. Unlike the well-publicised technological advancements that have accelerated both operations and decommissioning at nuclear facilities around the world, the challenges that technology have brought to the nuclear industry are either not fully understood or have yet to be entirely assessed. One of the greatest technological benefits to the nuclear industry exists from the increased use of robotic technologies - specifically unmanned aerial vehicle (UAV) systems and other autonomous platforms, as part of routine and emergency site monitoring. The use of this technology by other (unauthorised) parties, however, represents a significant challenge, and one that has yet to be fully un-assessed. Other technologies, their advantages and challenges within the nuclear industry, discussed in this work include the potential / growing use of Small Modular Reactor (SMR) systems and the 'Internet of Things' (IoT). (authors)

[en] Large quantities of irradiated graphite containing C-14 will arise from the decommissioning of the UK's Magnox power stations. Magnetic sector secondary ion mass spectrometry (MS-SIMS) has been used to investigate the distribution of this radioisotope within a number of trepanned graphite samples from a variety of radial and axial positions within reactor one at Oldbury, a Magnox nuclear reactor. The methodology used for these determinations ensured that possible mass interferences between C-14 species and oxygen-bearing species were eliminated from the analysis. This work indicates that a carbonaceous deposit found on exposed channel wall face samples has a relative C-14 enrichment compared to the underlying graphite, with concentrations calculated between approximately 5 and 55 ppm. Samples without this deposit gave C-14 concentrations below the limits of detection of the instrument, verifying that the enrichment is due to the deposit. Variations in C-14 concentration with sample height have been shown, with samples lower in the core having an increased C-14 concentration compared with those higher up. (authors)

[en] Unmanned aerial vehicles (UAVs) are now widely employed as part of numerous applications including defence, search and rescue as well as within scientific fields such as high-altitude atmospheric sampling and remote sensing, to name but a few. However, their application to the high-resolution detection of radiation anomalies (specifically as part of the routine monitoring on nuclear sites) has been less well explored. In this work, we present the results of the radiation monitoring via a lightweight aerial platform on an active nuclear site (Sellafield Ltd.); having already deployed the device in the Fukushima-contaminated region. The system employed was able to detect regions of elevated radiation at the sub-meter scale as well as attributing the species responsible. Such a system presents an extremely powerful tool where it is not desirable, nor practical, to send human operators. Results presented show that the platform is easily capable of operating within the challenging and confined settings of a site such as Sellafield (or other similar sites worldwide). (authors)

[en] Zero-valent iron nanoparticles are effective remediators of uranium from solution. It is postulated that the improved core crystallinity and the migration of impurity phases to the nanoparticle surfaces induced by annealing may improve their corrosion resistance and reactive lifespan. The ability of annealed and non-annealed Fe and FeNi nanoparticles to remediate a U-contaminated effluent from AWE, Aldermaston was investigated. Nanoparticles (of diameter typically between 0 and 100 nm) were introduced to the effluent and allowed to react for 7 days during which the liquid and nanoparticulate solids were periodically sampled. In all the systems, the maximum U-uptake occurred within 1 h of introduction, with variable efficiency. The Fe nanoparticles removed 98% of the total U from solution, resulting in a final U-concentration of <4 μg/L. A rapid release of Fe into solution was recorded early in the reaction period: attributed to limited partial dissolution of the nanoparticles. Annealing the Fe nanoparticles did not affect their efficiency but the dissolution of Fe was significantly reduced and X-ray Photoelectron Spectroscopy indicated slower progressive oxidation. The performance of the FeNi nanoparticles was significantly improved by annealing, with U-uptake increasing from 50 to 94%. Although the dissolution of Ni was completely inhibited by annealing, the Fe dissolution increased compared to that observed for the non-annealed FeNi nanoparticles, in contrast to behaviour exhibited by Fe-annealed nanoparticles. In all the systems, U was reduced to U(IV) and retained on the surfaces of the nanoparticulate solids for up to 48 h; the U-stability was not affected by annealing the Fe or the FeNi nanoparticles before use.

[en] One of the current primary concerns within the British nuclear community is the decommissioning of legacy storage ponds in Sellafield Cumbria, where nuclear fuel cladding material (a Mg-Al alloy) resides along with fuel metallic swarf. Corrosion of the immersed metallic elements, which has been occurring over the storage period, has resulted in the formation of what is commonly known as Corroded Magnox Sludge. The behaviour of uranium metal within this particular environment and, more significantly, the identity of the corrosion products that may have formed is currently unknown. The present study attempts to shed some light on these aspects by investigating simplified surrogate systems, mimicking storage ponds. (authors)

[en] The volume of nuclear waste from operating nuclear reactors, decommissioning and military activity is ever-increasing worldwide. In 2018, the IAEA reported there existed some 6,317,000 m³ of legacy waste awaiting long-term storage. A method is required to categorize this waste ahead of this storage. Sort and Segregation could hold the answer to solving the problem of long-term waste disposal. Sort and Segregation enables the chemical and radiometric characterization of waste articles destined for long term nuclear waste storage, enabling nuclear waste management teams to subsequently store waste with confidence. Currently, Sort and Segregation is labor-intensive, delivers high worker dose rates and requires extensive user time input. An autonomous solution could, therefore, reduce the time and costs of the procedure, allowing for a high throughput. It could also increase the precision of the task, as it does not incur the excessive conservatisms that are introduced by human operators, as precautionary measures. Most importantly worker safety would be increased. A prototype autonomous sort and segregation system is demonstrated. It uses sensors and a robotic arm to facilitate the sorting and segregation of nuclear waste autonomously, using commercial off the shelf technology. This is an important proof of concept system which aims to demonstrate a solution to the problem of sorting and segregating nuclear waste for long term storage. A radiation sensor is used to characterize objects radiometrically. This collects full spectral data which can be used to identify the radioactive emitter present, alongside its radioactivity in dose rate and activity. Object mass is measured using a grasping arm. The robotic arm is fitted with a gripper which is used to grasp the objects. Given the classification of nuclear waste as a function of activity per unit mass, the grasping arm must weigh the object to make an estimation as to the correct waste stream in which the object should be placed. This is possible using the force torque sensors located in the robot's joints. The process for in-situ weighing on the robotic arm is explained and tested. (authors)

[en] The global nuclear industry has a growing volume of nuclear waste which needs to be scanned, sorted according to its activity and material type, then processed into the correct waste packages for long term storage and disposal. It is vital that there is a detailed understanding of the waste inventory stored in long term waste containers, as knowledge of their contents could predict or prevent any adverse effects in storage. The numerous 'scan and sort' tables which are currently used at many different facilities around the world to sort waste into their correct containers are human operated and require very slow gamma scanning procedures combined with educated guesswork to manually sort the waste. This often leads to excessive conservatisms, with placement of lower activity wastes in higher activity containers, which in turn costs significantly more to store. In the United Kingdom it costs UK Pounds 46 k per cubic meter to store intermediate level waste compared to just UK Pound 2.9 k per cubic meter to store low level waste according to a 2008 Department of Energy and Climate Change report in the UK. A proposed solution to this problem, is the use of a robotic manipulator to automatically inspect the 'scan and sort table' in order to produce an accurate 3D model of the table's waste contents and attach an overlaid radiation map. The radiation map contains spectrometry data and can in consequence be used to distinguish and locate specific radioisotopes. The 3D model should be as accurate as possible in order to allow for a second robot arm with an attached gripper to grasp the objects and place them into their designated long-term storage container. Various scanning procedures are explored in this study including basic raster scanning, adaptive raster scanning and point sampling. The optimal solution will in practice be defined by the required application and activity level of the wastes being inspected. The results presented in this study indicate that it is possible to produce a centimeter accurate 3D model of a mixed assortment of components on a nuclear waste 'scan and sort' table. In addition, it was shown that the waste objects emitting radiation could be accurately identified and located, with an overlaid radiation map. This study is applicable across the nuclear waste management sector. Many of the ideas and concepts developed in this study are applicable in other decommissioning settings for example, dismantling of legacy gloveboxes or routine inspection of nuclear waste packages in storage. (authors)

[en] Decommissioning legacy spent fuel ponds within nuclear facilities can be a complicated process, largely in part due to the unknown state of materials deposited into such storage ponds during the operational lifetime of the facility. Materials may have corroded, and their condition deteriorated. Due to the nature of the materials deposited in such storage sites, minimising disturbance is desirable, and as such non-destructive techniques such as optical analysis methods are preferred over destructive techniques. In this work, we demonstrate three such optical techniques (Raman spectroscopy, photogrammetry, and hyperspectral imaging) capable of ascertaining useful characteristics of objects such as material type, surface corrosion, degradation, and 3D structure. A pool environment was used to capture data and demonstrate the techniques suitability for use in nuclear waste characterization in active spent fuel ponds. The optical techniques used enabled material characteristics to be obtained. (authors)

[en] There is a growing global demand for a safe, environmentally conscious, and long-term radioactive waste disposal solution. Owing to the potentially deleterious effects of waste evolution during containment, there are strict guidelines and waste packaging specifications which must be adhered to, including rigorous documentation of waste inventories. This mandates a detailed characterization of waste materials prior to packaging. In development, is a robotic waste sorting system, which analyses assorted waste objects, situated on a sorting table, based on their radiometric and material properties. This system uses a robotic manipulator with attached sensing technologies, and a gripper to fulfill waste characterization and sorting procedures. Initial waste surface scanning has previously been demonstrated, providing an overview of the material, chemical and radiometric characteristics of the sorting table. Hence, it has been shown that it is possible to determine the radiometric and material composition of waste components from a top-down perspective using the system. From a radiometric perspective this is insufficient, as radiation readings from an individual waste object may become skewed by other sources present within the mixed waste. This makes it difficult to accurately determine the activity of the object. One solution to this problem is the application of 'post-grasp assay'. Post-grasp assay may be defined as the process of presenting the grasped objects to a fixed sensor suite, located away from the waste table. The grasped object will be able to be radiometrically scanned in isolation of other radioactive emitters. The method works by first presenting the grasped object to a 3D depth camera. Depth camera feedback subsequently informs the system of an appropriate scan location for making a radiometric assessment. In addition, the object can be safely oriented in front of a sensor, without risk of collision. Radiation measurements taken can then be used to determine the activity in becquerels (Bq). Radiation 'counts' recorded by detector technologies do not directly translate into activity in Bq. This is because radiation is emitted stochastically and isotropically and the radioisotopes responsible may be heterogeneously distributed within the volume of the contaminated object. Hence, geometric effects must be considered to understand the expected gamma-photon flux at the detector. In addition, the intrinsic efficiency of the detector varies with gamma photon energy. Therefore, it is important to quantify intrinsic efficiency as a function of energy before analysis of activity. The geometric efficiency can be determined through analysis of the objects shape and size, knowledge of which will be understood from depth camera feedback. An intrinsic detector efficiency can be calculated using a Monte Carlo based simulation model; achieved by comparing results from an object of known activity and geometry, with the simulated model. By evaluating the intrinsic efficiency, and scaling the geometric efficiency appropriately, radiometric data may be processed to evaluate an estimate of the object activity in Bq. According to the UK nuclear waste classification guidelines, objects are classified in terms of activity per unit mass. Therefore, the weight of the object can be combined with the derived activity and then suitably classified into a particular threshold or 'class' of waste. (authors)