Group Members
Post-doctoral researchers
Dr Jia-Li Chen
For more than 50 years, nuclear power has been a key part of the UK’s energy mix. Unlike many countries, the UK has reprocessed its spent nuclear fuel, recovering still-viable components which can be reused in new fuel. One product of this recycling is plutonium, and the UK has about half of the World’s civil inventory of this element, stored safely in an interim facility at Sellafield as plutonium dioxide powder. The long-term fate of this material is yet to be decided, the most likely options being re-use in mixed oxide nuclear fuel or burial deep underground in a geological disposal facility. Although it has been estimated that the UK’s plutonium inventory could generate c. £100 Bn of electricity, we do not currently have the capability to manufacture mixed oxide fuel on a commercial scale. And, while much work is being carried out to prepare for a geological disposal facility, the UK has not yet identified a site for its location. Hence, we must continue to store our plutonium above ground for several decades. Together with colleagues from Manchester, Imperial College London, the National Nuclear Laboratory and Sellafield Limited, Jia-Li is working to understand more about the aging of plutonium dioxide, to aid future decisions concerning its ongoing safe storage.
Dr Song Yu
Radicals are highly reactive and ideal for building complex compounds. Samarium(II) diiodide, SmI2, also known as Kagan’s reagent, is a classic single electron transfer (SET) reagent that can efficiently produce radical species and mediate chemical processes that no other reagent can. It is a crucial catalyst in organic synthesis and one of the most significant SET reagents. However, a well-known drawback of SmI2, i.e., it must always be used in stoichiometric excess, raises issues of cost and waste and impedes its application in industry. Recently, the group of Prof. David J. Procter developed SmI2-catalysed reactions through radical relays that only need a catalytic amount of reagent. In these reactions, SET from SmI2 converts the substrate to a radical, which then undergoes radical relocation, bond-formation, new radical generation, and radical back-donation to regenerate the catalyst. Song uses density functional theory calculations and quantum chemical analyses to better understand the mechanisms driving these catalytic coupling reactions and radical relays.
PhD students
Nic Greaves
In 2005 it was shown that aqueous actinyls in the presence of peroxide and alkali metal ions are able to spontaneously form stable and water soluble cage structures. These cages are thought to occur in places where actinides are in direct contact with alkali metal containing water, such as the contaminated sea water from the Fukushima power plant. Additionally these cages have been linked to enhanced rates of fuel rod corrosion in aqueous environments. As such, understanding these molecules could prove useful in nuclear clean up and decommissioning.
Nic’s project involves studying the geometric and electronic properties of these cages, looking at uranyl peroxide dimers all the way to progressively larger and more complicated cage clusters.
Emma Pye
Emma’s research focuses on the integration of biocatalysis and metal-mediated radical cyclizations for diversity oriented synthesis. Synthetic chemists have struggled to generate molecular complexity from simple starting materials whilst still achieving a precise control of 3D shape. Biocatalysis — the use of enzymes to catalyse chemical transformations — is a rapidly developing field for the synthesis of complex, biologically- relevant structures. Biocatalysis has made it possible to access complex architectures with exquisite selectivity that can be difficult (or impossible) to achieve using traditional chemical methods. The benign nature of enzymes makes them suitable alternatives to traditional chemocatalysis; enzymes are biodegradable, non-toxic, often reusable and are derived from renewable resources. In addition, reactions are mostly carried out in aqueous solution and at moderate temperatures, making them more favourable than conventional chemically-mediated processes. Recent advances in the field — thanks to recent Chemistry nobel prize winner, Frances Arnold — such as directed evolution, enables enzymes to be genetically modified in order to tailor their properties. So far this has allowed operation of the enzymes in new reaction conditions, optimisation of their catalytic activity towards new substrates and the generation of new biocatalysts which catalyse chemical transformations unknown to nature. The future of molecular manufacture will see the integration of biocatalytic and chemocatalytic processes become more prominent. Emma’s current studies look at combining an experimental and computational approach in order to integrate biocatalytic processes with SmI2-mediated radical cyclisations.
Ryan Dempsey
The Enhanced Actinide Removal Plant (EARP) at Sellafield has been the UK’s most crucial radioactive effluent treatment plant since its operation began in 1994. The EARP removes actinides and other fission products by association with ferrous mineral phases during a base-induced precipitation process. The same process was also used to aid the clean-up operations after the 2011 Fukushima Daiichi disaster. Unfortunately, the mechanism by which the actinides associate with the iron-bearing minerals is unknown. It has been observed that during the process Pu(IV) may bind to a Keggin type Fe(III) nanocluster with further evidence that the Keggin unit is a prenucleation cluster during ferrihydrite formation. Ryan will use molecular quantum chemical techniques based on open-shell Density Functional Theory to investigate the bonding interactions and redox chemistry between actinides and this Keggin cluster. Starting with Pu(IV), and exploring other actinides found at the EARP, Ryan aims to provide a better understanding of the processes underpinning nuclear waste clean-up to inform future efforts.
Corinne Hatton
The long-term storage of high level spent nuclear fuel is a problem in the UK and worldwide, and one potential solution is to design and employ geological disposal facilities (GDFs). In these facilities it is crucial that the uranium and other actinide species are unable to migrate into the geosphere. To design GDFs, the interactions between actinide species and minerals surfaces at an atomic scale need to be understood and a comprehensive model developed. Iron (II) minerals are being researched specifically due to their abundance and ability to react with uranium species. Corinne’s research will be studying the interaction, chemical bonding and REDOX transformations of aqueous uranium species with iron minerals. This research will use hybrid DFT within the Periodic Electrostatic Embedded Cluster Method (PEECM) with accompanying experimental studies with the Natrajan group here in Manchester.
Josef Tomecek
Metal-metal bonding between actinide elements was a rather rare phenomenon limited to a small number of species stable in the gas phase at very low temperatures. This was recently changed by Liddle and Kaltsoyannis’s report of a tri-thorium cluster [{Th(η8‑C8H8)(μ3‑Cl)2}3{K(THF)2}2]∞ (Nature 598 (2021) 72). In his PhD project, Josef uses both DFT and ab initio methods to shed light on actinide-actinide bonding. Starting with the parent tri-thorium cluster, the next steps will lead to the exploration of other systems that may be eventually prepared and/or to the study of other compounds synthesised by Liddle’s group.
Anlu (Tara) Wei
Nuclear fuel is typically uranium dioxide. During its lifetime in reactors, some of the uranium converts to plutonium by radioactive decay. After the spent fuel is removed from UK reactors, the plutonium is separated out, and is currently placed in interim storage pending a Government decision as to its long-term fate, which may well be burial in a geological disposal facility (GDF). A prospective GDF wasteform material for hosting plutonium is zirconolite. To evaluate the long-term performance of potential wasteforms, it is crucial to understand the effects of the radioactive decay of the plutonium. This decay produces helium, the release of which inside the wasteform can lead to the formation of bubbles and cracking, and hence to decreased durability. Tara’s PhD project is therefore a comprehensive computational study of the behaviour of helium in zirconolite. Density functional theory and molecular dynamics simulation will be employed to investigate the migration of helium in zirconolite as well as the thermodynamics and kinetics of helium bubble formation.
Celina Hjort Buhl
SmI2 is a versatile resultant in organic chemistry, and its use in organic radical catalysis is a new area worthy of deeper exploration. The SmI2 is typically modelled computationally with THF ligands making up its primary coordination shell, but it is not yet known how accurate that model is – other ligands such as water or HMPA may well displace one or more THF in catalytic reactions. The initial purpose of Celina’s MPhil project is to take previously modelled, and possibly new, reactions and explore the effects of replacing one or more THF ligands with water or HMPA.