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In the field of radioactive waste management, particularly the geological disposal of higher activity radioactive waste, support for the longevity of engineering solutions in the repository is partly based on studies of natural systems, especially geological examples, often referred to as natural analogues (NA). Since the radioactive waste can be hazardous over hundreds of thousands of years, the long-term safety has to be assessed to very far future, e.g. up to 1 Ma from now. NA studies cover and exceed the time spans of interest. Despite of the long-acknowledged importance of NAs in the safety case for the geological disposal of radioactive waste, there is a lack of guidance and strategic planning to incorporate this information to the safety cases that assess the overall safety of the repositories – this leads to a certain lack of resilience. This paper presents the work undertaken to develop a strategy for utilising natural analogues (NAs) in Nuclear Waste Services (NWS), UK, geological disposal facility (GDF) programme. The work is largely based on the extensive review of the strategic use of NAs in the international context, lessons learnt from various past programmes and by considering how the strategy could look like in the current framework of the UK's GDF programme. The strategy presented aims to support this programme. The main message is that NA information and projects can and should be handled through the same procedures as any research utilising existing and upcoming NWS protocols. This means that NAs need to be a part of knowledge management, rather than, for example, a stagnant database. Including NAs as part of the data screening allows the knowledge base to be updated according to needs arising from the changes in the GDF programme when moving from generic stage towards more site and design specific phases. It is foreseen that key to the best utilisation of NA information is to include it in the NWS' digital safety case, making the information and the related methodology transparent. This paper refers to NWS' GDF siting programme as at September 2023. [ABSTRACT FROM AUTHOR]

Intrigued by the role of geographical location in public engagement with science we examine the West Cumbria Managing Radioactive Waste Safely (MRWS) Partnership's undertaking of one of the most extensive local public engagements with environmental risk science in the UK. The case study highlights this three-year long local engagement as a process that changed both science and the public. Differently from other invited public engagements controlled by scientists in spaces set aside from the everyday, the Partnership's lay members led a process unfolding in the place that was potentially at risk. In contrast to public participation as experiments staged by experts the Partnership had the authority to demand that scientists addressed issues of local importance. The analysis uses the framing notions 're-situating technoscience' and 're-assembling the public', to capture how scientific knowledge claims were modified and a new local public emerged, at the intersection of public engagement with science and public participation in environmental risk governance in a specific place. [ABSTRACT FROM AUTHOR]

A series of long-term laboratory experiments was started in 1995 to investigate longer-term dissolution/ precipitation reactions that may occur in the alkaline disturbed zone surrounding a cementitious repository for radioactive waste. They consist of samples of UK basement rock reacting with either Na-K-Ca-OH water ('young' cement porewater) or Ca-OH water ('evolved' cement porewater) at 70°C. This paper summarizes results of reactions occurring over the first 15 months. Experiments of both fluid types showed many similar features, though primary mineral dissolution and secondary mineral precipitation were more extensive in the experiments involving Na-K-Ca (younger) cement porefluids compared to more evolved (Ca-rich) cement porefluids. Dissolution of dolomite, and to a lesser extent silicates (probably K-feldspar, but also possibly mica) occurred relatively rapidly at 70°C. Dolomite dissolution may have been a key factor in reducing pH values, and may be a key mineral in controlling the extent of alkaline disturbed zones. Dissolution was followed by precipitation of brucite close to dolomite grains, at least two generations of C-S-H phases (which may have contained variable amounts of K, Al and Mg); overgrowths of calcite; small crystals of hydroxyapophyllite; and elongate crystals of celestite. Though hydroxyapophyllite was observed (a phase commonly associated with zeolites), there was no evidence for the formation of zeolites in the experiments. Fluid chemical changes track the mineralogical changes, with C-S-H phases being a major control on fluid chemistry. In the 'young' porewater experiments there were decreases in pH, and K, Ca and Mg concentrations, together with transitory increases in SiO2 concentrations. In the 'evolved' porewater experiments there were decreases in pH, Mg, Ca and Sr concentrations, together with small increases in K and SiO2 concentrations. A number of experiments are still running, and will be sampled in coming years. [ABSTRACT FROM AUTHOR]

Predictions of material activity in commercial fusion conditions predominantly rely on computational methods, due to a lack of data on long-term effects of high-energy neutron irradiation on structural steels. Consequently, this could result in a bias due to uncertainties in nuclear data used. This work focused on modelling neutron activation of four structural steels in a fusion reactor environment after 20 years of operation. Eurofer, F82H and G91, were assessed as candidate in-vessel materials, whereas SS316L(N)-IG was solely modelled in the vacuum vessel. Activation calculations were performed using the inventory code FISPACT-II using inputs from Monte-Carlo transport simulations performed with OpenMC. The study employed a one-dimensional reactor model with a Helium-Cooled Pebble Bed (HCPB) tritium-breeding blanket design. With the XSUN-2022 code package, a nuclear data sensitivity and uncertainty analysis on production cross-sections of relevant radio-nuclides was carried out. Eurofer and F82H steels exhibited significantly higher resistance to neutron activation than G91 and SS316L(N)-IG. At 100 years after shutdown, none of the steels reached UK low-level waste (LLW) activity levels in the first wall. In the rear of the back-support structure (BSS) of the reactor blanket, all assessed steels reached LLW levels within approximately 30 to 45 years of reactor shutdown. It was found that the vacuum vessel (SS316L(N)-IG) would not be classifiable as LLW for several centuries. Dominant radio-nuclides for each material were identified with FISPACT-II to carry out the uncertainty analyses. The calculated uncertainties were too small to affect the waste disposal options for the first wall within 100 years, but the time-to-reach LLW for BSS and vacuum vessel steel could be uncertain by up to approximately 3 and 6 years, respectively. • Nuclear fusion activation calculations were performed using FISPACT-II. • Sensitivity and uncertainty analysis carried out with XSUN-2022 code package. • Large parts of reactor exceeded UK low-level activity limits for centuries. • Uncertainties in nuclide production larger in rear of blanket than in first wall. • Nuclear data uncertainties affected decay time by several years. [ABSTRACT FROM AUTHOR]

Identifying and evaluating the factors that might impact on the long-term integrity of a deep Geological Disposal Facility (GDF) and its surrounding geological and surface environment is central to developing a safety case for underground disposal of radioactive waste. The geological environment should be relatively stable and its behaviour adequately predictable so that scientifically sound evaluations of the long-term radiological safety of a GDF can be made. In considering this, it is necessary to take into account natural processes that could affect a GDF or modify its geological environment up to 1 million years into the future. Key processes considered in this paper include those which result from plate tectonics, such as seismicity and volcanism, as well as climate-related processes, such as erosion, uplift and the effects of glaciation. Understanding the inherent variability of process rates, critical thresholds and likely potential influence of unpredictable perturbations represent significant challenges to predicting the natural environment. From a plate-tectonic perspective, a one million year time frame represents a very short segment of geological time and is largely below the current resolution of observation of past processes. Similarly, predicting climate system evolution on such time-scales, particularly beyond 200 ka AP is highly uncertain, relying on estimating the extremes within which climate and related processes may vary with reasonable confidence. The paper highlights some of the challenges facing a deep geological disposal program in the UK to review understanding of the natural changes that may affect siting and design of a GDF. [ABSTRACT FROM AUTHOR]

The implementation of a geological disposal facility requires the demonstration of confidence that such a facility would be safe during both the operational period and in the long-term after the closure of such a facility. The generic environmental safety case described in this paper is the vehicle used to demonstrate an understanding of environmental safety. It will be used to prepare a site-specific environmental safety case in due course. The approach taken will be consistent with a staged development and approval process, as advocated by the environmental regulators. [ABSTRACT FROM AUTHOR]

The international long-term cement studies (LCS) project aims to increase the understanding of the behaviour of cement within a radioactive waste disposal system and how hyper-alkaline leachates may interact with host rock. Such an understanding enables confident, robust and safety-relevant statements to be made concerning future system behaviour, irrespective of host rock, engineered barrier system, or waste type. The LCS project involves laboratory experiments, in situ tests and numerical modelling to address these issues. The agencies participating are Nagra (Switzerland), JAEA (Japan), the Nuclear Decommissioning Authority, Radioactive Waste Mangement Directorate (UK), Posiva (Finland) and SKB (Sweden). Project activities have included: the development of conceptual and theoretical models of cement-rock interaction; testing of numerical models against data from laboratory experiments and industrial and natural analogues of cement-rock reaction; and the synthesis and incorporation of performance assessment (PA) relevant data from analogue studies. Key threads running through these studies include an analysis of issues relating to upscaling of processes and data to the greater temporal and spatial scales relevant to PA, and investigations of modelling the changes in physical properties that accompany geochemical reaction. Here we present examples of the results from model test cases, highlighting the important issues that have arisen. [ABSTRACT FROM AUTHOR]

This article analyses the nature and role of recently established deliberative and participatory mechanisms of planning and decision-making on radioactive waste management in three countries that have recently committed to extending their nuclear capacity - Finland, France and the UK. The article introduces the micro and macro theories of deliberative democracy, and - by relying on the distinction between the normative, substantive and instrumental functions of participation - examines the degrees to which the different deliberative mechanisms succeeded in bridging the boundary between the micro and macro deliberation. The empirical analysis illustrates how the functions and the influence of these mechanisms have been conditioned by the broader macro discursive sphere, within which the mixed forms of deliberation take place. Elements of all three functions of participation could be identified to varying degrees in all cases, yet the direct impact of deliberation on policy outcomes was often modest and uncertain. In contrast, the analysis highlights, on the one hand, the indirect impacts of deliberation - notably through the creation of norms of deliberative democracy - and on the other hand, the need to consider the broader macro discursive sphere when designing processes and institutions of deliberation. The case studies suggest that the control over knowledge production as well as the trust in government institutions were pivotal in explaining the influence of deliberation in the three countries. [ABSTRACT FROM AUTHOR]

Abstract: Much of the work of the UK nuclear industry is now concerned with decommissioning many of the existing power stations and other facilities. An important aspect of this work is the accurate measurement of low levels of radioactivity in waste forms such as building materials in order that these materials can be assigned to the correct waste streams. This has led to a call for suitable standards and reference materials, and the specific needs of UK users were identified at an NPL workshop in 2005. One of the highest priorities was for ‘soft waste’ spiked with γ-emitters in a 200L drum format, with an activity concentration of just under 0.4Bqg−1. In response, NPL prepared a single reference drum meeting this specification. The low density was achieved by loading the drum with plastic bottles, each partially loaded with ion-exchange resin. The resin in each bottle had been previously spiked with a mixture of 241Am, 137Cs and 60Co, all traceable to national standards. The drum would be used primarily as the basis of a comparison exercise, but feedback on its usefulness as a calibration standard would also be sought. The drum was measured by 17 radioassay groups at 15 UK sites. The monitors used were mostly commercial γ-spectrometry systems designed to accommodate waste drums. Some groups measured the drum on more than one monitor and some used more than one efficiency calibration. Many of the groups used mathematical modelling to derive their efficiencies. The results of the exercise were discussed at a second NPL workshop (2007), after which the participants were allowed to submit supplementary or replacement results (with reasons for any changes clearly stated). In total, 88 results were submitted. A total of 51 results were in agreement with the NPL values; of the remaining results, 24 were explained by the participants concerned (or were revised to provide supplementary values), but the other 13 results were either clearly discrepant or questionable. The exercise demonstrated differences between laboratories who had used the same modelling software for their efficiency calibrations, and indeed facilitated an exchange of models between these laboratories. The importance of an accurate knowledge of the form and structure of the sample in efficiency modelling was clearly demonstrated. Uncertainty budgets were of variable quality. Some participants quoted MDA values for one or more of the radionuclides. A follow-up comparison was requested and this is now being planned. [Copyright &y& Elsevier]

While participatory forms of risk assessment and management have been the focus of much conceptualisation, experimentation, and evaluation, relatively less effort has gone into understanding how so called 'analytic-deliberative' processes are developing across policy-for-real decision contexts. This paper develops a novel typology of citizen-science interaction as a basis for analysing the nature and extent of recent participatory risk assessment practice in the UK. It draws on the reflections of professional actors operating across the UK environmental risk domain, focusing down on practice in the area of radioactive waste between 1998 and 2003. Compared with past science-centred approaches, analysis shows an 'opening up' of risk decision processes to extended actors, knowledges, and values, with particular importance placed on public involvement in front-end framing. This is being constrained by a failure to integrate engagement throughout decision processes, the exclusion of publics from assessing/evaluating environmental risks, and the upholding of a strict separation between citizens/science. These patterns of analytic-deliberative practice - determined by contextual influences, barriers and challenges operating across UK environmental risk issue-areas - highlight the need for further methodological development and systematic evaluation of relations between processes and outcomes. [ABSTRACT FROM AUTHOR]

The basic principles of incorporating high level radioactive waste into glasses, ceramics (Synroc type) and glass composites including glass ceramics are described. Current UK technology uses glass wasteforms for the products of reprocessing, although many countries are temporarily storing the ceramic spent fuel for eventual disposal. Some waste streams may be incorporated into ceramics, but difficult or legacy wastes will require the development of other wasteforms comprising composite systems of crystals and glass. The importance of processing–property–structure (especially durability) relations in such systems over size scales from the atomic to the geological and on timescales to hundreds of thousands of years is highlighted. [ABSTRACT FROM AUTHOR]

Reactions that occur between a radioactive waste and a cement matrix being used for encapsulation can compromise the integrity of the resulting wasteform. The present paper describes some of the interactions that can occur within Portland cement based systems. It highlights the fact that to achieve successful encapsulation of the wide range of waste types that make up the legacy or historic wastes present in the UK, a toolbox or formulary of different cement systems with differing chemistries is needed. Some potential alternative cement systems are discussed. [ABSTRACT FROM AUTHOR]

The roles of science, ethics and politics are identified in respect of the risks of exposure to low-dose radiation. Two case studies, the epidemiology of the United Kingdom nuclear test veterans and the risks to civilians associated with the military use of depleted uranium, are considered in the context of their ethical framing, scientific evaluation and political resolution. Two important issues for the present and future, the safe management of UK radioactive waste and the future of nuclear power, in which the science of low dose effects will be crucial and where the ethical issues are much more complex, are introduced. Specific consideration is given to the potential hereditary effects of ionising radiation in relation to the current state of radiobiological knowledge. It is concluded that for science to be useful in public health policy making there needs to be some reform from within the profession and the political imperative for freely independent scientific institutions. [ABSTRACT FROM AUTHOR]

Site selection for deep disposal of intermediate and high level radioactive waste in the UK to date has not taken full advantage of oil industry databases that cover offshore areas. The shallow water area of the UK continental shelf is twice that of the onshore area and due to variations in regional geology, many geological settings occur that are not found onshore. The geology and hydrogeology of the UK continental shelf contrast in many respects with that of onshore areas. The geology of the North Sea in particular is constrained by over 3000 deep (>2 km) exploration wells, 50,000 km2 of 3D seismic data and several million line kilometres of 2D seismic data—vastly more than the coverage of data constraining the deep geology onshore. Combined with detailed studies of oil and gas fields, this data has led to a greater technical understanding of many aspects of offshore geology relative to that onshore. These data represent an original investment of £20bn by oil and gas companies, but are now in the public domain. These databases are used here to compare onshore and offshore settings in terms of criteria such as structural geology, fault activity and uplift/subsidence. Clear differences emerge, such as risk of seismicity, exhumation and the variety of hydrogeological systems. The distribution and geometry of candidate repository sites throughout the North Sea (salt structures, shale basins, sealed sandstone reservoirs and basement highs) are illustrated. Several lines of petroleum-related research have yielded lessons that may be useful in assessing deep repository locations, such as migration of hydrocarbons through shale seals. The exceptional combination of seismic data and well control means that offshore areas on the continental shelf and the North Sea in particular can now be thoroughly explored in this context and contribute candidate sites into a nationwide portfolio of deep geological disposal options, in the event of site selection being pursued in the UK. An example framework for this process is presented here. [Copyright &y& Elsevier]

Magnesium aluminosilicate and magnesium borosilicate glass formulations were developed and evaluated for the immobilisation of the radioactive waste known as Magnox sludge. Glass compositions were synthesised using two simplified bounding waste simulants, including corroded and metallic uranium and magnesium at waste loadings of up to 50 wt.%. The glasses immobilising corroded simulant waste formed generally homogenous and fully amorphous glasses, while those immobilising metallic wastes contained crystallites of UO 2 and U 3 O 8. Uranium speciation within the glass was investigated by micro-focus X-ray absorption near edge spectroscopy and it was shown that the borosilicate glass compositions were characterised by a slightly lower mean uranium oxidation state than the aluminosilicate counterparts. This had an impact upon the durability, and uranium within glasses of higher mean oxidation states was dissolved more readily. All material showed dissolution rates that were comparable with simulant high level radioactive waste glasses, while the borosilicate-based formulations melted at a temperature suitable for modern vitrification technologies used in radioactive waste applications. These data highlight the potential for vitrification of hazardous radioactive Magnox sludge waste in borosilicate or aluminosilicate glass formulations, with the potential to achieve >95 % reduction in conditioned waste volume over the current baseline plan. • Magnesium aluminosilicate and magnesium borosilicate glass systems were synthesised to incorporate metallic uranium and magnesium, U 3 O 8 and Mg(OH) 2 • Uranium speciation within the glass was investigated by micro-focus X-ray absorption near edge spectroscopy • Borosilicate glasses possessed greater chemically durable than their aluminosilicate counterparts • All glass compositions demonstrated durability that is comparable to UK and French high level waste glass [ABSTRACT FROM AUTHOR]

The effective management of radioactive waste is a necessary prerequisite to the use of nuclear energy. The UK's policy for the long-term management of higher activity radioactive waste (HAW), and potentially spent nuclear fuel (SNF), is disposal in a deep underground geological disposal facility (GDF). A GDF will isolate HAW from mankind until the radioactivity has decayed to levels where any risk to future generations is acceptably low. It is likely, therefore, that a GDF will need to safely contain radioactive materials for hundreds of thousands of years. The necessary isolation will be provided by a combination of natural (geological) and engineered barriers. A multi-layered engineered barrier system will provide the defence-in-depth that is required to give the public confidence in the long-term performance of the GDF. This paper identifies the significant role each engineered barrier or "layer" plays in ensuring that long-lived radionuclides remain isolated from the biosphere and receptors within the vicinity of a GDF. Receptors include human and animal populations, and the natural environment. The paper also explores the characteristics and performance of a number of suitable candidate materials for use in the UK GDF engineered barriers. An indication of the lifetime of potential barriers under conditions pertinent to each of the UKs proposed geological settings is given. As the performance of the engineered barriers will be vital to the GDF post-closure safety case, several areas for further work are proposed. [Display omitted] • UK radioactive waste will be disposed of in a geological disposal facility (GDF). • Radionuclides may be contained for a period of up to 3 million years by a GDF. • The engineered barriers employed are highly dependent on the wasteform and geology. • Barriers may serve multiple roles e.g. backfill, redox control, pH buffering etc. • These roles are critical to ensuring radionuclide release is minimised. [ABSTRACT FROM AUTHOR]

Many concepts for the disposal of intermediate-level radioactive waste specify the emplacement of waste packages in underground vaults backfilled with cementitious material. The cementitious backfill performs a number of functions including maintaining alkaline conditions and providing a high sorption capacity for radionuclides. In the UK, the Nirex Reference Vault Backfill (NRVB) has been developed for such a role. To improve our understanding of its long-term performance, a detailed programme was undertaken to investigate interactions of the NRVB with selected groundwater components using sodium sulphate and magnesium chloride solutions. Experiments using the selected solutions were performed under conditions of constant flow, over timescales of up to 860 days. Elemental composition and pH of the egressing eluent were determined throughout the experiments. At the end of the experiments, detailed solid analyses were performed on samples from various locations in the NRVB using a wide range of techniques. In the sodium sulphate experiment, sulphate attack resulted in the formation of ettringite, thaumasite and gypsum. For the magnesium chloride case, the results were dependent on the concentration of the magnesium in the ingressing solution. At higher concentration, precipitation of brucite at the upstream surface of the NRVB led to clogging and termination of the experiment after about one month. At lower concentration, no such clogging occurred, despite almost all the ingressing magnesium being removed by the NRVB over timescales of more than two years. For both systems, high pH values of the eluent were maintained over the full periods studied; for the sodium sulphate experiment the final pH was 12.7 (after 180 sample volumes) and for the low concentration magnesium chloride case pH 11.5 (after 749 sample volumes). A "top-down" modelling approach was applied to interpret the results, involving solution equilibration with the NRVB represented by a simple set of mineral phases. Further processes were modelled only where they improved the overall fits. The resulting models were considered to be simple while maintaining consistency with the major features of the experimental data sets. This has helped to provide mechanistic interpretations of the evolution of NRVB, based on relatively simple sets of secondary mineral phases, early kinetic control of mineral dissolution and diffusion-restricted release of portlandite at longer times. • Flow-through experiments elucidate cementitious backfill–groundwater interactions. • Alkaline conditions are maintained across large volumes of cumulative flow. • Lower flow rates in latter stages of the experiments aid subsequent interpretation. • A "top down" modelling approach allows explanation of most experimental results. [ABSTRACT FROM AUTHOR]

Following the Secretary of State's March 1997 refusal of planning permission for a rock characterization facility at Longland's Farm, Cumbria, and a change of government less than two months later, the long-term management of the UK's radioactive waste remains unresolved. This paper sets out the current Radioactive Waste Management Advisory Committee's (RWMAC's) views on the best way forward, which it has input to the Select Committee enquiry. However, whatever the outcome of the Government's policy review, RWMAC sees its role to be that of helping to ensure that the chosen option is implemented in the optimum manner. [ABSTRACT FROM AUTHOR]

The UK nuclear industry uses seawater for both operational purposes and waste discharge. Atmospheric and direct radiation discharges alsoaffect the surrounding coastal environment. The regulation of these discharges has undergone great changes in the last decade. This article begins by quantifying the composition of the discharges that occur. It then introduces the current legislative controls over radioactive discharges, concentrating on the Radioactive Substances Act 1993 and analyses the authorization framework implemented by the EnvironmentAgency. Industry concerns with the current system are highlighted and their alternative analyzed. The Environment Agency's response to these proposals and future authorization issues are highlighted. [ABSTRACT FROM AUTHOR]

The physically based river catchment modelling system SHETRAN incorporates components representing water flow, sediment transport and radionuclide transport both in solution and bound to sediments. The system has been applied to simulate hypothetical future catchments in the context of post-closure radiological safety assessments of a potential site for a deep geological disposal facility for intermediate and certain low-level radioactive wastes at Sellafield, west Cumbria. In order to have confidence in the application of SHETRAN for this purpose, various blind validation studies have been undertaken. In earlier studies, the validation was undertaken against uncertainty bounds in model output predictions set by the modelling team on the basis of how well they expected the model to perform. However, validation can also be carried out with bounds set on the basis of how well the model is required to perform in order to constitute a useful assessment tool. Herein, such an assessment-based validation exercise is reported. This exercise related to a field plot experiment conducted at Calder Hollow, west Cumbria, in which the migration of strontium and lanthanum in subsurface Quaternary deposits was studied on a length scale of a few metres. Blind predictions of tracer migration were compared with experimental results using bounds set by a small group of assessment experts independent of the modelling team. Overall, the SHETRAN system performed well, failing only two out of seven of the imposed tests. Furthermore, of the five tests that were not failed, three were positively passed even when a pessimistic view was taken as to how measurement errors should be taken into account. It is concluded that the SHETRAN system, which is still being developed further, is a powerful tool for application in post-closure radiological safety assessments.