Maqarin Phase IV report

Cement and concrete are extensively used in the construction of repositories for low- and intermediate-level radioactive wastes (L/ILW). In underground silos, like those in Sweden and Finland for example, much of the waste is conditioned with concrete (e.g. spent ionexchange resins) and is packed in concrete containers (e.g. Figure 1.1)1. Even in many high-level radioactive waste (HLW) repositories, cement and concrete may be widely used. Instances include the paving of tunnels, shotcreting of tunnel walls, and injection and grouting of fractures. Consequently, in many repository designs, cement-based materials are expected to dominate the repository. In the Swiss L/ILW concept, for example, current designs envisage the use of up to 1.5 million tonnes of cement, approximately 85-90% by weight of the total repository. This will ensure the long-term maintenance of hyperalkaline conditions, predicted to suppress the solubility of key radionuclides in the waste (e.g. Hodgkinson and Robinson, 1987) and to enhance their sorption on the cement (e.g. Stumpf et al., 2004)

Geothermal Energy: Delivering on the Global Potential

After decades of being largely the preserve of countries in volcanic regions, the use of geothermal energy—for both heat and power applications—is now expanding worldwide. This reflects its excellent low-carbon credentials and its ability to offer baseload and dispatchable output - rare amongst the mainstream renewables. Yet uptake of geothermal still lags behind that of solar and wind, principally because of (i) uncertainties over resource availability in poorly-explored reservoirs and (ii) the concentration of full-lifetime costs into early-stage capital expenditure (capex). Recent advances in reservoir characterization techniques are beginning to narrow the bounds of exploration uncertainty, both by improving estimates of reservoir geometry and properties, and by providing pre-drilling estimates of temperature at depth. Advances in drilling technologies and management have potential to significantly lower initial capex, while operating expenditure is being further reduced by more effective reservoir management — supported by robust mathematical models — and increasingly efficient energy conversion systems (flash, binary and combined-heat-and-power). Advances in characterization and modelling are also improving management of shallow low-enthalpy resources that can only be exploited using heat-pump technology. Taken together with increased public appreciation of the benefits of geothermal, the technology is finally ready to take its place as a mainstream renewable technology, This book draws together some of the latest developments in concepts and technology that are enabling the growing realisation of the global potential of geothermal energy in all its manifestations.After decades of being largely the preserve of countries in volcanic regions, the use of geothermal energy—for both heat and power applications—is now expanding worldwide. This reflects its excellent low-carbon credentials and its ability to offer baseload and dispatchable output - rare amongst the mainstream renewables. Yet uptake of geothermal still lags behind that of solar and wind, principally because of (i) uncertainties over resource availability in poorly-explored reservoirs and (ii) the concentration of full-lifetime costs into early-stage capital expenditure (capex). Recent advances in reservoir characterization techniques are beginning to narrow the bounds of exploration uncertainty, both by improving estimates of reservoir geometry and properties, and by providing pre-drilling estimates of temperature at depth. Advances in drilling technologies and management have potential to significantly lower initial capex, while operating expenditure is being further reduced by more effective reservoir management — supported by robust mathematical models — and increasingly efficient energy conversion systems (flash, binary and combined-heat-and-power). Advances in characterization and modelling are also improving management of shallow low-enthalpy resources that can only be exploited using heat-pump technology. Taken together with increased public appreciation of the benefits of geothermal, the technology is finally ready to take its place as a mainstream renewable technology