Decommissioning, Immobilisation and Storage
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DISTINCTIVE is a multi-disciplinary collaboration of 10 universities and 3 key industry partners from across the UK’s civil nuclear sector.

4th ARF Round

Date: February 14, 2017

Five sub-projects were awarded funding. Here the successful candidates summarise the proposed work:

Round 4

A Lab-scale Fixed Bed Reactor to Investigate Gas Phase Kinetics for Long Term PuO2 Storage

Dr Luke Jones and Thomas Donoclift – University of Manchester

The aim of this project is to build and commission a bench scale fixed bed reactor which will allow investigation of catalytic and thermal reactions between the gas phase and a bed of oxide powder such as PuO2 and appropriate surrogates. This project will help to obtain a better kinetic understanding of thermal and catalytic mechanisms occurring inside storage canisters. The ultimate objective of the project is to install this equipment inside a glovebox at the NNL’s Central Lab to carry out experiments to simulate the chemistry inside PuOstorage canisters.

Study of Physico-Chemical Interactions Between PuO2 and H2O

Dr. Dominic Laventine – University of Lancaster

More than 100 tonnes of Pu are stored in the UK, typically as plutonium dioxide (PuO2) powder contained within nested stainless steel cans. Under some conditions, these cans pressurise due to production of gas within the can. This makes the cans difficult to store and handle and must be avoided in practise.

A number of chemical and radiological processes that involve trapped water in the cans have been suggested as the cause of this gas production. We aim to precisely measure absorption / release of gases including water vapour from PuO2 surfaces using highly accurate piezoelectric crystal balances. This will allow prediction of PuO2 behaviour during long term storage, allowing it to be safely stored.

Developing ERT Equipment for the Detection of Colloidal Silica Grout

Dr Matteo Pedrotti– University of Strathclyde

The proposed project aims to facilitate detection of colloidal silica-based grouts during creation of hydraulic ground barriers, with a particular emphasis on applications within the challenging environment of the Sellafield site. Potential grout applications at Sellafield include: the injection of horizontal and vertical barriers to form a second skin for unlined waste disposal trenches; and saturation injection for complete ground sealing beneath high hazard facilities, as a risk mitigation strategy during waste retrieval.

Sellafield site, as with most of the nuclear sites, is a highly contaminated and congested area. Many parts of the site are not directly accessible either because other buildings prevent access, or because of site contamination and radiological hazard.

Consequently, the strategic aim of the proposed project is to acquire, develop and test a non-invasive imaging system that can reliably detect the location (and shape) of a grouted soil volume within a radiological environment, whilst also requiring limited site access.

In many applications, the boreholes used for grout injection will be a long distance from some sections of the final barrier. This is particularly true for horizontal containment, in which injection and extraction boreholes may be 10s of meters apart. To ensure reliable barrier formation over such distances, it will be particularly important to image the real-time grout injection so that both the grout properties and the hydraulic engineering design strategy can be adjusted in situ to account for heterogeneous flow conditions. Further, since colloidal silica injection is intended to be a durable intervention technique even under long-term exposure to radiation, the possibility of being able to routinely monitoring barrier condition, years after the injection, is the sine qua non for its future asset management.

Investigation of Radiation Damage by Mossbauer Nuclear Spectroscopy

Dr. Shi Kuan Sun – University of Sheffield

This project aims to exploit Mossbauer spectroscopy to understand radiation damage in ceramic materials for actinide wastes. The DISTINCTIVE active equipment fund has allowed us to procure two radioactive sealed sources, and ancillary items, for our existing Mossbauer spectrometer to allow element specific investigation of the average atomic scale structure of ion bean amorphised ceramic materials. Within DISTINCTIVE, we will utilise this enhanced capability to build on our proof of concept studies to understand the mechanisms of the crystalline to amorphous phase transition in ceramic wasteforms, which will contribute to the disposal system safety case. In doing so, we have created a unique national facility for research of this type, placing the UK at the forefront of the application of Mossbauer spectroscopy to waste immobilisation applications.

In Situ High Resolution Neutron Diffraction Studies of Glass-Ceramic Crystallisation

Dr. Shi  Kuan Sun –  University  of  Sheffield

The aim of this project is to characterize and understand the sequence of crystallization reactions which occur during the processing of zirconolite glass-ceramics, by kinetic neutron diffraction. Fundamentally, the primary mechanism of zirconolite formation in this glass-ceramic system is unknown. The bounding hypothetical models involve i) a template mechanism with dissolution of some batch components and diffusion to reaction sites, or ii) dissolution of all batch components and precipitation of solubility limited target phases. This experiment will resolve our hypothesis using neutron diffraction to characterize the evolving phase assemblage during material processing, which is the only method of interrogating samples of cm3 volume. Knowledge of the fundamental mechanism of zirconolite formation in this glass-ceramic system is important for development of a safety case to support a full scale process facility. 



Dr Jones’ PDRA project is titled “Understanding the Interfacial interactions of Plutonium Dioxide with Water”. His lead supervisor is Dr Simon Pimblott (Simon.Pimblott@manchester.

Dr Shi Kuan Sun’s PDRA project is titled “Ceramic Materials for Actinide Disposition”. His lead supervisor is Professor Neil Hyatt (

Dr Laventine’s PDRA project is titled “Understanding the Interfacial Interactions of Plutonium Dioxide with Water”. His lead supervisor is Professor Colin Boxall (

Dr. Pedrotti’s PDRA project is titled ” In-situ Ground Contaminant Containment (Physical Barrier)”. His lead supervisor is Dr. Grainne El Mountassir (



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