Reactive spark plasma synthesis of CaZrTi2O7 zirconolite ceramics for plutonium disposition

Near single phase zirconolite ceramics, prototypically CaZrTi 2 O 7 , were fabricated by reactive spark plasma sintering (RSPS), from commercially available CaTiO 3 , ZrO 2 and TiO 2 reagents, after processing at 1200 °C for only 1 h. Ceramics were of theoretical density and formed with a controlled mean grain size of 1.9 ± 0.6 μm. The reducing conditions of RSPS afforded the presence of paramagnetic Ti 3+ , as demonstrated by EPR spectroscopy. Overall, this study demonstrates the potential for RSPS to be a disruptive technology for disposition of surplus separated plutonium stockpiles in ceramic wasteforms, given its inherent advantage of near net shape products and rapid throughput

Compatibility of fossil fuel energy system for UK climate targets

The United Kingdom (UK) has an ambitious greenhouse gas (GHG) reduction target with legally binding commitment of 80% reduction by 2050 relative to 1990 levels. The Committee on Climate Change (CCC) sets carbon budgets to meet this goal, and suggested that electricity generation should be below 50 g CO2e per kWh(e) by 2030. At the same time, the UK is renewing gas distribution pipeline systems to decrease leakages and increase efficiency of gas delivery, all while pursuing a domestic shale gas industry to meet continued demand as traditional gas production decreases. Competing in the same market, the United States (US) became a net exporter of natural gas at the end of 2017, largely due to increased production of shale gas, and holds contracts for distribution in the UK. It is clear that the UK is continuing reliance on natural gas in the near term, despite climate targets, and will need advanced mitigation strategies. One such strategy is using Enhanced Oil Recovery (EOR) with CO2 and coupling it with Carbon Capture and Storage (CCS). This strategy can create of a large commercial market for EOR offshore of the UK, and maintain a 50% chance of keeping temperature rise below +2°C throughout the 21st century. The market has the potential to accelerate CO2 storage investment, and aid in meeting UK climate targets. A coupled CCS-EOR scenario might contribute to decarbonisation of UK grid electricity. Using UK data, progressive introduction from 2020 of 11 CCS-to-EOR gas-power plant projects is estimated to store 52 Mt CO2 yr-1 from 2030. These 11 projects also produce extra revenue of 1,100 MM bbls of taxable EOR-oil from 2020 to 2049. The total average electricity grid factor in the UK reduces from 490 to 90 – 142 kg CO2e MWh-1, with gas generating 132 TWh of clean electricity annually. This life cycle analysis (LCA) is unusual in linking oil production and combustion with CCS and gas fuelled electricity. With a full LCA, this aggressive CCS-EOR scenario provides a net carbon reduction, and progressively reduces net oil combustion emissions beyond 2040. A second strategy could be needed if the projected domestic gas supply gap for power generation (without CCS) were to be met by UK shale gas with low fugitive emissions (0.08%). In this case an additional 20.4 Mt CO2e would need to be accommodated during carbon budget periods 3 – 6. However, a modest fugitive emissions rate (1%) for UK shale gas would increase global emissions compared to importing an equal quantity of Qatari liquefied natural gas, and risk exceeding UK carbon budgets. Additionally, natural gas electricity generation would emit 420 – 466 Mt CO2e (460 central estimate) during the same time period within the traded EU emissions cap. In addition to electricity generation, shale gas supply chain emissions for heat are assessed. This thesis assesses the greenhouse gas emissions intensity of US and UK shale gas as determined by source, distribution and end use for heat. It assesses the merit order of shale gas imported to the UK from the US versus domestic production and use of shale gas in the US or UK, considering distribution network renewals and the total emissions intensity of shale gas used. The import and use of US-produced shale gas liquefied natural gas (LNG) in the UK would increase GHG emissions relative to domestic UK shale gas production and use by 178 Mt CO2e, yet only increasing UK carbon budgets 3-6 by 14.2 Mt CO2e (19.2%). It is found that losses in the distribution phase represent a highly uncertain, but potentially important component of shale gas GHG intensity. This thesis considers the implications for GHG emissions measurement and reporting, climate change mitigation via municipal pipeline renewal, and national carbon budgets to 2035. Most importantly, under the current production-based greenhouse gas accounting system, the UK is incentivized to import natural gas rather than produce it domestically throughout each of the cases studied. This thesis gives policy recommendations to mitigate the impact of perverse incentives in new GHG regulations

REQUESTED EVIDENCE TO BUSINESS, ENERGY AND INDUSTRIAL STRATEGY COMMITTEE INQUIRY: CARBON CAPTURE, USAGE AND STORAGE – GAS STANDARDS, HYDROGEN AND GSMR

Gas networks carry the majority of the UK’s energy supply. These can be readily converted from methane to hydrogen. In fact, pilot projects and other works are under way with safety as the primary criterion. However, a regulatory blockage is that the Gas Safety (Management) Regulations (GSMR) set in 1996 are extremely restrictive on the variation of UK gas supply. Less than 0.1% hydrogen can be incorporated into UK gas supply so that existing pilot tests can only be undertaken on limited, isolated networks. Coupled with this, customers are currently charged by calorific value of a gas based on a flow weighted average in a very small number of billing zones within the UK (specified within the Gas (Calculation of Thermal Energy) Regulations (CoTER)). There are only 13 zones and Scotland, for example, is just one zone, which requires all gas sources into that network to be enriched or deriched to the prevailing gas quality for the entire zone. This methodology has to change to allow blending of hydrogen into the network. Both these key pieces of outdated legislation will block demonstrations and roll-out of hydrogen blending or conversion. And this will block the UK’s decarbonisation progress. Funds for hydrogen blending and conversion should be included in the control period bids by gas networks, which will become settled in late 2019, for 2021-26 spending. GSMR and CoTER regulations can only be altered by Government, the Health and Safety Executive and Ofgem, respectively. That needs Government action. Guarantee of GSMR and CoTER changes will enable investment to be agreed by the boards of gas networks. Both GSMR and CoTER are on the decarbonisation critical path to adoption of hydrogen as an energy carrier through the existing gas infrastructure, be it through blending or full conversion

Solubility, speciation and local environment of chlorine in zirconolite glass–ceramics for the immobilisation of plutonium residues

The immobilisation and disposal of fissile materials from civil and defence nuclear programmes requires compatible, passively safe and proliferation resistant wasteforms. In this study, we demonstrate the application of an albite glass–zirconolite ceramic material for immobilisation of chloride contaminated plutonium oxide residues in the United Kingdom. The chlorine solubility limit in the albite glass phase was determined to be 1.0 ± 0.1 wt%, above the maximum envisaged chorine inventory of 0.5 wt%, attainable at a 20 wt% PuO2 incorporation rate within the ceramic. Cl K-edge of X-ray Absorption Near Edge Spectroscopy (XANES) was exploited to confirm partitioning of Cl to the glass phase, speciated as the chloride anion, with exsolution of crystalline NaCl above the chlorine solubility limit. Combinatorial fitting of Cl XANES data, utilising a library of chemically plausible reference spectra, demonstrated the association of Cl with Na and Ca modifier cations, with environments characteristic of the aluminosilicate chloride minerals eudialyte, sodalite, chlorellestadite and afghanite. Adventitious incorporation of Ca, Zr and Ti within the albite glass phase apparently assists chlorine solubility, by templating a local chemical environment characteristic of the mineral reference compounds. The partitioning of Ce, as a Pu analogue, within the glass–ceramic was not adversely impacted by incorporation of Cl. The significance of this research is in demonstrating the compatibility of the glass–ceramic wasteform toward Cl solubility at the expected incorporation rate, below the determined solubility limit. Thus, an upstream heat treatment facility to remove chloride contamination, as specified in the current conceptual flowsheet, would not be required from the perspective of wasteform compatibility, thus providing scope to de-risk the technology roadmap and reduce the projected capital and operational plant costs

The pore space scramble:challenges and opportunities for subsurface governance

There is a rich literature on environmental governance that provides critiques and conceptual tools on how various environmental 'arenas' or overlapping global systems should be governed eg. climate, energy, oceans (Cherp et al., 2011, Berkes, 2006, Underdal, 2010). In this paper we argue that the geological subsurface should be considered as a new arena for governance in its own right. The arguments for this are presented by considering current and future challenges the subsurface will face as its utilisation evolves and intensifies, particularly in the context of both energy security and low carbon energy. Three main challenges are highlighted; ownership, access and long term stewardship. These challenges are presented using the illustrative context of subsurface pore space for the long term storage of CO2 from Carbon Capture (CCS). This is presented in the UK context but ultimately has implication for global subsurface governance going forward

The role and value of inter-seasonal grid-scale energy storage in net zero electricity systems

Grid-scale inter-seasonal energy storage and its ability to balance power demand and the supply of renewable energy may prove vital to decarbonise the broader energy system. Whilst there is a focus on techno-economic analysis and battery storage, there is a relative paucity of work on grid-scale energy storage on the system level with the required temporal resolution. Here, we evaluate the potential of power-to-gas-to-power as inter-seasonal energy storage technology. Our results suggest that inter-seasonal energy storage can reduce curtailment of renewable energy, and overcapacity of intermittent renewable power. Importantly, grid scale energy storage assumes a critical role especially when the technology options for dispatchable power are limited. It appears that neither high CAPEX nor low round-trip efficiency preclude the value of the technology per se, however the rate of charge and discharge of the technology emerges as key technical characteristic. This study emphasises the rising importance of balancing seasonality in energy systems characterised by a high penetration of renewable energy, and prompts questions regarding sector integration and resilient decision-making toward a zero-carbon economy

Financing low-carbon generation in the UK: The hybrid RAB model

Decarbonising electricity is a critical first step in mitigating climate damage but low/zero-carbon generation is very capital intensive. Its cost depends critically on the weighted average cost of capital (WACC). Three factors combine to make a low WACC both desirable and feasible in the UK. First, the Stern Report argues for a low social discount rate (1.4% real) for investments in climate mitigation. Second, global and UK real interest rates have been falling steadily - UK gilt index-linked 20-year rates have fallen from +4% in 1995 to -2% (negative) in 2019. CCS and nuclear have long lifetimes over which to recover their capital cost, longer than commercial finance would accept without guarantees, in contrast to renewables where off-take contracts have proven sufficient. Nuclear power faces the additional investment challenge of lengthy uncertain construction. No nuclear plant has ever been built privately without substantial regulatory guarantees. The Regulated Asset Base (RAB) model can address these financing problems for long-lived low-carbon assets. The benefits of placing risk on developers to motivate cost control are small compared to the extra costs of a higher weighted average cost of capital (WACC). A hybrid RAB model (like that used for the Thames Tideway Tunnel)—with excess cost sharing and a cost cap—can reduce risk to deliver an adequately low WACC by accessing infrastructure funds that do not require extensive specialised project knowledge. If the risk of excess costs is spread over the 27 million households and other customers taking two-thirds of electricity, each would bear minimal risk and the cumulative cost would be significantly lower. The levelized cost at the WACC (3.5% real) is £53/MWh if on time and budget, which should be compared with a counterfactual in which all the risk is placed on the company requiring a contract-for-difference with a strike price of £96/MWh for the life of the project (equal to the levelized cost). The levelised cost to consumers if on time and budget would be £50/MWh and in the worst case with a 48% cost over-run, £64/MWh