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Mass transport by aqueous fluids is a dynamic process in shallow crustal systems, redistributing nutrients as well as contaminants. Rock matrix diffusion into fractures (void space) within crystalline rock has been postulated to play an important role in the transient storage of solutes. The reacted volume of host rock involved, however, will be controlled by fluid-rock reactions. Here we present the results of a study which focusses on defining the length scale over which rock matrix diffusion operates within crystalline rock over timescales that are relevant to safety assessment of radioactive and other long-lived wastes. Through detailed chemical and structural analysis of natural specimens sampled at depth from an active system (Toki Granite, Japan), we show that, contrary to commonly proposed models, the length scale of rock matrix diffusion may be extremely small, on the order of centimetres, even over timescales of millions of years. This implies that in many cases the importance of rock matrix diffusion will be minimal. Additional analyses of a contrasting crystalline rock system (Carnmenellis Granite, UK) corroborate these results.

Large-scale compressed air energy storage facilities offer one solution to the UK's energy demands, using solution-mined caverns in salt lithologies. For optimum gas storage efficiency, cavern geometry should ideally be smooth: spherical to cylindrical with a circular cross-section. However, such caverns are often irregular with marked asymmetry or ellipticity, and although the reasons for non-circular cross-sections developing during solution mining in some caverns can be related to, for example, the presence of interbedded lithologies, in other instances they are not fully understood. Cavities from dissolution experiments using five main end-member salt facies fabrics from the Triassic Preesall and Northwich Halite formations have been assessed to determine factors affecting cavity geometry, formation and variability in dissolution behaviour. Identical sets of experiments were performed on each fabric type, using two solution concentration strengths: brine and synthetic seawater. Comparison of experimental results using a combination of analytical and imaging techniques shows the extent to which the salt fabric and enhancement of features within the salt influence the resulting dissolution cavity. Observations show a visible increase in micropores within the adjacent halite matrix following dissolution. Smaller-scale features provide further insights into the dissolution processes, and salt fabric behaviour under different dissolution conditions. Supplementary material: A detailed description of methods is available at https://doi.org/10.6084/m9.figshare.c.4282454

This report is the published product of one of a series of studies covering England, Wales and Northern Ireland commissioned by Radioactive Waste Management (RWM) Ltd. The report provides geological information about the London and the Thames Valley region to underpin the process of national geological screening set out in the UK Government’s White Paper Implementing geological disposal: a framework for the long-term management of higher activity radioactive waste (DECC, 2014). The report describes geological features relevant to the safety requirements of a geological disposal facility (GDF) for radioactive waste emplaced onshore and up to 20 km offshore at depths between 200 and 1000 m from surface. It is written for a technical audience but is intended to inform RWM in its discussions with communities interested in finding out about the potential for their area to host a GDF.

This report is the published product of one of a series of studies covering England, Wales and Northern Ireland commissioned by Radioactive Waste Management (RWM) Ltd. The report provides geological information about the East Anglia region to underpin the process of national geological screening set out in the UK’s government White Paper Implementing geological disposal: a framework for the long-term management of higher activity radioactive waste (DECC, 2014). The report describes geological features relevant to the safety requirements of a geological disposal facility (GDF) for radioactive waste emplaced onshore and up to 20 km offshore at depths between 200 and 1000 m from surface. It is written for a technical audience but is intended to inform RWM in its discussions with communities interested in finding out about the potential for their area to host a GDF.

This report is the published product of one of a series of studies covering England, Wales and Northern Ireland commissioned by Radioactive Waste Management (RWM) Ltd. The report provides geological information about the Wealden district region to underpin the process of national geological screening set out in the UK’s government White Paper Implementing geological disposal: a framework for the long-term management of higher activity radioactive waste (DECC, 2014). The report describes geological features relevant to the safety requirements of a geological disposal facility (GDF) for radioactive waste emplaced onshore and up to 20 km offshore at depths between 200 and 1000 m from surface. It is written for a technical audience but is intended to inform RWM in its discussions with communities interested in finding out about the potential for their area to host a GDF.

This report is the published product of one of a series of studies covering England, Wales and Northern Ireland commissioned by Radioactive Waste Management (RWM) Ltd. The report provides geological information about the Northern England region to underpin the process of national geological screening set out in the UK’s government White Paper Implementing geological disposal: a framework for the long-term management of higher activity radioactive waste (DECC, 2014). The report describes geological features relevant to the safety requirements of a geological disposal facility (GDF) for radioactive waste emplaced onshore and up to 20 km offshore at depths between 200 and 1000 m from surface. It is written for a technical audience but is intended to inform RWM in its discussions with communities interested in finding out about the potential for their area to host a GDF.

This report is the published product of one of a series of studies covering England, Wales and Northern Ireland commissioned by Radioactive Waste Management (RWM) Ltd. The report provides geological information about the Pennines and adjacent areas region to underpin the process of national geological screening set out in the UK’s government White Paper Implementing geological disposal: a framework for the long-term management of higher activity radioactive waste (DECC, 2014). The report describes geological features relevant to the safety requirements of a geological disposal facility (GDF) for radioactive waste emplaced onshore and up to 20 km offshore at depths between 200 and 1000 m from surface. It is written for a technical audience but is intended to inform RWM in its discussions with communities interested in finding out about the potential for their area to host a GDF.

This report is the published product of one of a series of studies covering England, Wales and Northern Ireland commissioned by Radioactive Waste Management (RWM) Ltd. The report provides geological information about the Hampshire Basin and adjoining areas region to underpin the process of national geological screening set out in the UK’s government White Paper Implementing geological disposal: a framework for the long-term management of higher activity radioactive waste (DECC, 2014). The report describes geological features relevant to the safety requirements of a geological disposal facility (GDF) for radioactive waste emplaced onshore and up to 20 km offshore at depths between 200 and 1000 m from surface. It is written for a technical audience but is intended to inform RWM in its discussions with communities interested in finding out about the potential for their area to host a GDF.

This report is the published product of one of a series of studies covering England, Wales and Northern Ireland commissioned by Radioactive Waste Management (RWM) Ltd. The report provides geological information about the South-west England region to underpin the process of national geological screening set out in the UK Government’s White Paper Implementing geological disposal: a framework for the long-term management of higher activity radioactive waste (DECC, 2014). The report describes geological features relevant to the safety requirements of a geological disposal facility (GDF) for radioactive waste emplaced onshore and up to 20 km offshore at depths between 200 and 1000 m from surface. It is written for a technical audience but is intended to inform RWM in its discussions with communities interested in finding out about the potential for their area to host a GDF.

This report is the published product of one of a series of studies covering England, Wales and Northern Ireland commissioned by Radioactive Waste Management (RWM) Ltd. The report provides geological information about Northern Ireland to underpin its process of national geological screening set out in the UK’s government White Paper Implementing geological disposal: a framework for the long-term management of higher activity radioactive waste (DECC, 2014). The report describes geological features relevant to the safety requirements of a geological disposal facility (GDF) for radioactive waste emplaced onshore and up to 20 km offshore at depths between 200 and 1000 m from surface. It is written for a technical audience but is intended to inform RWM in its discussions with communities interested in finding out about the potential for their area to host a GDF.

This report is the published product of one of a series of studies covering England, Wales and Northern Ireland commissioned by Radioactive Waste Management (RWM) Ltd. The report provides geological information about the Central England region to underpin the process of national geological screening set out in the UK Government’s White Paper Implementing geological disposal: a framework for the long-term management of higher activity radioactive waste (DECC, 2014). The report describes geological features relevant to the safety requirements of a geological disposal facility (GDF) for radioactive waste emplaced onshore and up to 20 km offshore at depths between 200 and 1000 m from surface. It is written for a technical audience but is intended to inform RWM in its discussions with communities interested in finding out about the potential for their area to host a GDF.

This report is the published product of one of a series of studies covering England, Wales and Northern Ireland commissioned by Radioactive Waste Management (RWM) Ltd. The report provides geological information about the Welsh Borderland region to underpin the process of national geological screening set out in the UK’s government White Paper Implementing geological disposal: a framework for the long-term management of higher activity radioactive waste (DECC, 2014). The report describes geological features relevant to the safety requirements of a geological disposal facility (GDF) for radioactive waste emplaced onshore and up to 20 km offshore at depths between 200 and 1000 m from surface. It is written for a technical audience but is intended to inform RWM in its discussions with communities interested in finding out about the potential for their area to host a GDF.

This report is the published product of one of a series of studies covering England, Wales and Northern Ireland commissioned by Radioactive Waste Management (RWM) Ltd. The report provides geological information about Wales to underpin the process of national geological screening set out in the UK’s government White Paper Implementing geological disposal: A framework for the long-term management of higher activity radioactive waste (DECC, 2014). The report describes geological features relevant to the safety requirements of a geological disposal facility (GDF) for radioactive waste emplaced onshore and up to 20 km offshore at depths between 200 and 1000 m from surface. It is written for a technical audience but is intended to inform RWM in its discussions with communities interested in finding out about the potential for their area to host a GDF.

This report is the published product of one of a series of studies covering England, Wales and Northern Ireland commissioned by Radioactive Waste Management (RWM) Ltd. The report provides geological information about the Eastern England region to underpin the process of national geological screening set out in the UK’s government White Paper Implementing geological disposal: a framework for the long-term management of higher activity radioactive waste (DECC, 2014). The report describes geological features relevant to the safety requirements of a geological disposal facility (GDF) for radioactive waste emplaced onshore and up to 20 km offshore at depths between 200 m and 1000 m from surface. It is written for a technical audience but is intended to inform RWM in its discussions with communities interested in finding out about the potential for their area to host a GDF.

This report is the published product of one of a series of studies covering England, Wales and Northern Ireland commissioned by Radioactive Waste Management (RWM) Ltd. The report provides geological information about the Bristol and Gloucester region to underpin the process of national geological screening set out in the UK’s government White Paper Implementing geological disposal: a framework for the longterm management of higher activity radioactive waste (DECC, 2014). The report describes geological features relevant to the safety requirements of a geological disposal facility (GDF) for radioactive waste emplaced onshore and up to 20 km offshore at depths between 200 and 1000 m from surface. It is written for a technical audience but is intended to inform RWM in its discussions with communities interested in finding out about the potential for their area to host a GDF.

Unusual speleothem, associated with hyperalkaline (pH>12) groundwaters have formed within a shallow, abandoned railway tunnel at Peak Dale, Derbyshire, UK. The hyperalkaline groundwaters are produced by the leaching of a thin layer (<2 m) of old lime kiln waste above the soil-bedrock surface above the tunnel by rainwater. This results in a different reaction and chemical process to that more commonly associated with the formation of calcium carbonate speleothems from Ca-HCO3-type groundwaters and degassing of CO2. Stalagmites within the Peak Dale tunnel have grown rapidly (averaging 33 mm y-1), following the closure of the tunnel 70 years ago. They have an unusual morphology comprising a central sub-horizontally-laminated column of micro- to nano-crystalline calcium carbonate encompassed by an outer sub-vertical assymetric ripple laminated layer. The stalagmites are largely composed of secondary calcite forming pseudomorphs (<1 mm) which we believe to be predominantly after the ‘cold climate’ calcium carbonate polymorph, ikaite (calcium carbonate hexahydrate: CaCO3•6H2O), with minor volumes of small (<5 μm) pseudomorphs after vaterite. The tunnel has a near constant temperature of 8-9°C which is slightly above the previously published crystallisation temperatures for ikaite (<6°C). Analysis of a stalagmite actively growing at the time of sampling, and preserved immediately within a dry nitrogen cryogenic vessel, indicates that following crystallisation of ikaite, decomposition to calcite occurs rapidly, if not instantaneously. We believe this is the first occurrence of this calcium carbonate polymorph observed within speleothem.

The solubility of uranium and thorium has been measured under the conditions anticipated in a cementitious, geological disposal facility for low and intermediate level radioactive waste. Similar solubilities were obtained for thorium in all media, comprising NaOH, Ca(OH)2 and water equilibrated with a cement designed as repository backfill (NRVB, Nirex Reference Vault Backfill). In contrast, the solubility of U(VI) was one order of magnitude higher in NaOH than in the remaining solutions. The presence of cellulose degradation products (CDP) results in a comparable solubility increase for both elements. Extended X-ray Absorption Fine Structure (EXAFS) data suggest that the solubility-limiting phase for uranium corresponds to a becquerelite-type solid whereas thermodynamic modelling predicts a poorly crystalline, hydrated calcium uranate phase. The solubility-limiting phase for thorium was ThO2 of intermediate crystallinity. No breakthrough of either uranium or thorium was observed in diffusion experiments involving NRVB after three years. Nevertheless, backscattering electron microscopy and microfocus X-ray fluorescence confirmed that uranium had penetrated about 40 μm into the cement, implying active diffusion governed by slow dissolution-precipitation kinetics. Precise identification of the uranium solid proved difficult, displaying characteristics of both calcium uranate and becquerelite.

Particulate matter sampling was conducted at Ballidon Quarry, Ballidon, Derbyshire. The quarry is owned and managed by Tarmac Trading Ltd. (Tarmac). The monitoring station deployed comprised two DS500X gravimetric samplers fitted with PM2.5 impactors, that were placed side by side in the primary crusher shed during February 2016. Monitoring was conducted over three, seven day periods. Particulate matter from six filters and oversize particulate matter collected from the impactor plates were analysed by BGS on behalf of DustScan using Scanning Transmission Electron Microscopy and Laser Diffraction granulometry. The results of the work show that the DS500X fitted with a PM2.5 size selective impactor is capable of separating particles with a projected area diameter of ≤ 2.5 μm from ambient air, retaining themon filter media for subsequent quantification. The overall median particle size recorded on the filters was 0.46 μm, the mean was 0.74 μm and the 95th percentile was 2.15 μm (n = 6343). A number of observations were made during this study and included in the full report which should be considered when interpreting the results.

There is an increasing need for underground storage of natural gas (and potentially hydrogen) to meet the UK’s energy demands and ensure its energy security. In addition, the growth of renewable energy technologies, such as wind power, will be facilitated by the development of grid-scale energy storage facilities to balance grid demand. One solution lies in creating large-scale compressed-air energy storage (CAES) facilities underground. Whilst a number of lithologies offer storage potential, only three operational CAES facilities exist in the UK. They are constructed in specifically designed solution-mined salt (halite) caverns, similar to those currently used for natural gas storage. The influences exerted on salt dissolution by petrology, structure and fabric during cavern construction are not fully understood, with some occurences of caverns with noncircular cross-sections being less than optimum for gas storage and especially CAES.

Radial diffusion experiments have been carried out to assess the migration of 36Cl, as chloride, through a cementitious backfill material. Further experiments in the presence of cellulose degradation products were performed to assess the effect of organic ligands on the extent and rate of chloride diffusion. Results show that breakthrough of 36Cl is dependent on chloride concentration: as the carrier concentration increases, both breakthrough time and the quantity retained by the cement matrix decreases. Experiments in the presence of cellulose degradation products also show a decrease in time to initial breakthrough. However, uptake at various carrier concentrations in the presence of organic ligands converges at 45% of the initial concentration as equilibrium is reached. The results are consistent with organic ligands blocking sites on the cement that would otherwise be available for chloride binding, though further work is required to confirm that this is the case. Post-experimental digital autoradiographs of the cement cylinders, and elemental mapping showed evidence of increased 36Cl activity associated with black ash-like particles in the matrix, believed to correspond to partially hydrated glassy calcium-silicate-sulfate-rich clinker.

A period of one million years following closure has been used by RWMD when considering the post-closure safety case for a geological disposal facility (GDF). It is during this period that evolution of the near-field and local geosphere as a result of GDF construction and operation will be at its most rapid and radioactivity of the emplaced waste will be at their highest levels. Significant effort has been spent internationally on identifying the many natural processes that may affect the evolution of the geosphere over this timescale and the contribution of those processes to GDF performance. The purpose of this report is to identify which processes are relevant to geosphere evolution in this time period around a generic GDF in the UK. Previous work has identified tectonic effects, climate change effects, uplift, subsidence, volcanism and diagenesis as key concerns. The potential impact of each of these processes on a generic UK GDF, constructed according to a multiple barrier concept and sited at a depth of between 200 and 1000 m in a suitable host rock, is outlined in the following sections: tectonic related uplift and subsidence; seismicity, tectonic history and volcanism; climate change and glaciation and weathering and erosion.

Large-scale compressed air energy storage facilities using solution-mined caverns in salt lithologies could be a solution to the UK's energy demands. For optimum gas storage efficiency, caverns should ideally be spherical to cylindrical with a circular cross-section but in reality are often irregular with marked asymmetry or ellipticity. Non-circular cross-sections developing during solution mining in some caverns can be related to factors such as the presence of interbedded lithologies, but they are often not fully understood. Cavities from dissolution experiments using five main end-member salt facies fabrics from the Triassic Preesall and Northwich halite formations have been assessed to determine factors affecting cavity geometry, formation, and variability in dissolution behaviour. Identical sets of experiments were performed on each fabric type, using two solution concentration strengths: brine and synthetic seawater. Comparison of experimental results using a combination of analytical and imaging techniques shows the extent to which the salt fabric and enhancement of features within the salt influence the resulting dissolution cavity. Observations show a visible increase in micropores within the adjacent halite matrix following dissolution. Smaller-scale features provide further insights into the dissolution processes and salt fabric behaviour under different dissolution conditions., Large-scale compressed air energy storage facilities using solution-mined caverns in salt lithologies could be a solution to the UK's energy demands. For optimum gas storage efficiency, caverns should ideally be spherical to cylindrical with a circular cross-section but in reality are often irregular with marked asymmetry or ellipticity. Non-circular cross-sections developing during solution mining in some caverns can be related to factors such as the presence of interbedded lithologies, but they are often not fully understood. Cavities from dissolution experiments using five main end-member salt facies fabrics from the Triassic Preesall and Northwich halite formations have been assessed to determine factors affecting cavity geometry, formation, and variability in dissolution behaviour. Identical sets of experiments were performed on each fabric type, using two solution concentration strengths: brine and synthetic seawater. Comparison of experimental results using a combination of analytical and imaging techniques shows the extent to which the salt fabric and enhancement of features within the salt influence the resulting dissolution cavity. Observations show a visible increase in micropores within the adjacent halite matrix following dissolution. Smaller-scale features provide further insights into the dissolution processes and salt fabric behaviour under different dissolution conditions.