Aker Solutions conceptually designed the accelerator-driven thorium reactor 600 MWe power station, an acceleratordriven, thorium-fuelled, lead-cooled fast reactor. Project objectives were to demonstrate the technical feasibility of the design to ensure a viable product. Aims were to apply established technology where possible, minimising research and development requirements, develop and protect intellectual property and align with Generation IV strategy. A business case demonstrates economic and market potential to stakeholders, and partners are being pursued to take the project through to successful completion. Thorium is an attractive alternative to uranium fuel, being more abundant and avoiding the need for enrichment. Additionally the accelerator-driven thorium reactor can burn waste actinides generated in uranium-fuelled reactors, providing sustainable energy for future civilisation.Choosing a sub-critical accelerator-driven system provides safe operating margins for the thorium fuel cycle. The proposed reactivity coefficient of 0 . 995 allows selection of an industrial-scale accelerator with commercial benefits which led to a novel solution for measurement and control of reactivity.

The worldwide need for energy, and particularly energy that does not generate carbon dioxide, has led to the possibility of nuclear reactors being installed in countries that previously have not used them. In many of these countries the electrical grid system is limited and would not be robust enough for the large power reactors currently under construction. The result has been the development of what have been termed ‘small modular reactors’ or SMRs. Although there has been no formal definition of such reactors, they are generally assumed to be less than 300 Mw. Various international companies have begun the process of developing SMRs, some being merely at the concept stage whereas others have gone beyond that having initiated related research projects. This paper briefly outlines the most significant of these designs under the three broad headings of light water reactors, high-temperature gas-cooled reactors and liquid metal and gas-fast reactors, highlighting their key features and providing references for anyone wishing to follow up any of them in more detail. It also draws some general conclusions about the potential deployment of these reactor systems in the future.

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Independent Nuclear Consultant, UKAs a member of the ICE Energy journal editorial board I have been asked to write the editorial for this issue. As a prestigious publication dealing with this very diverse topic 'energy', the scope for papers is wide ranging, from matters of policy through to detailed technical papers; both ends of this spectrum are represented in this issue. Irrespective of the nature of the paper the same rigorous review process operates and all papers have extensive reference lists which would be of great value to anyone wishing to develop further the topics discussed.The first item in this issue is a policy paper, which presents a briefing on the very important issue of a possible North Sea electricity grid established to accommodate the potential growth in the use of offshore wind turbines (Adeuyi and Wu, 2015). Quoting the potential North Sea wind turbine output by 2020 as 33 GW and 83 GW by 2030, the paper investigates the concept of a North Sea electricity grid designed to link all of the wind farms together and by so doing interconnect with the established electricity grids of adjacent countries, thus facilitating the creation of a European electricity trading market. The briefing then investigates at high level the use of submarine cables with an optimum balance of both AC and DC systems with strategically positioned converter systems. The briefing concludes that for such a North Sea interconnecting grid to happen there would be a number of challenges to tackle -not just technical but economic, financial, environmental and socio-economic -and notes that an agency has been established to investigate this.The first full paper in this issue comes under the category of policy and relates to the management of spent nuclear fuel (Al Bloushi et al., 2015). The United Arab Emirates (UAE) is the first of the Middle Eastern Arab countries to embrace nuclear generation of electricity to offset its use of fossil fuels and thereby reduce its impact on climate change. The state is building a four-reactor site using Korean-designed pressurised water reactors. It is therefore almost unique in being able to 'start from a blank sheet of paper' and take a dispassionate and independent view on the optimum ways of handling spent nuclear fuel which, although not strictly nuclear waste, shares some of the same characteristics (in that it is highly radioactive). The paper addresses this matter and considers a suitable assessment methodology and presents a preliminary assessment of four options all of which have pros and cons. It concludes that for the UAE the option of using deep geological boreholes for the disposal of the spent fuel is the appropriate way forward.The second paper is probably at the opposite end of the policy/technical detail spectrum as it focusses on a detailed analysis of the energy and exergy efficiencies of a diesel engine running on sunflower oil, or more specifically sunflower methyl ester biofuel (Yamık et al., 2015). The thermodynamic performance of the singlecylinder engine is evalu...