1. X-ray microcomputed tomography can be used to produce rapid, fully analysable, three-dimensional images of biological and other materials without the need for complex or tedious sample preparation and sectioning. We describe the use of this technique to visualise and analyse the microstructure of fragments of shell taken from three regions of chicken eggs (sharp pole, blunt pole and equatorial region).2. Two- and three-dimensional images and data were obtained at a resolution of 1.5 microns. The images were analysed to provide measurements of shell thickness, the spacial density of mammillary bodies, the frequency, shape, volume and effective diameter of individual pore spaces, and the intrinsic sponginess (proportion of non-X-ray dense material formed by vesicles) of the shell matrix. Measurements of these parameters were comparable with those derived by traditional methods and reported in the literature.3. The advantages of using this technology for the quantification of eggshell microstructural parameters and its potential application for commercial, research and other purposes are discussed.

In the UK, blended high level nuclear waste (HLW) streams from the Magnox and THORP reprocessing plants are currently vitrified using a lithium sodium borosilicate base glass frit. Laboratory and full size non-radioactive simulations (produced on the Vitrification Test Rig at Sellafield [1]) of these compositions have shown that these glasses need to be melted at circa 1050°C to obtain a reasonable viscosity for pouring. Also, at high waste loadings an alkali molybdate phase (termed “yellow phase”) can form in these glasses [e.g. 2, 3]. Vitrification flowsheets are set to avoid yellow phase formation as this phase is highly corrosive to the inconel melter in the molten state and is partially water soluble at ambient temperature and so may challenge product quality.Ca and Zn additions to the base glass frit have been found to reduce viscosity and allow melt homogeneity and pouring at lower temperatures. It was also theorised that Ca additions could increase the solubility of Mo and thus reduce the likelihood of yellow phase formation. The composition of the phase separated material in as-cast and heat treated specimens of Ca and Zn HLW glasses produced at both laboratory and full scale is examined in this work

Sellafield Ltd operates a Waste Vitrification Plant (WVP) to immobilise the arisings from the reprocessing of spent nuclear fuel. Washout of solids from the base of waste storage tanks in preparation for decommissioning is likely to produce feeds enriched in molybdenum to the WVP. Vitrification of such feeds in the borosilicate glass formulation currently used by the WVP for vitrification of reprocessing waste has been investigated to determine the maximum achievable loading of MoO3.The vitrification of molybdenum in the absence and presence of reprocessing waste was studied. A number of glasses were manufactured in the laboratory containing various waste loadings. The resultant glasses were examined both visually and under the scanning electron microscope for the presence of any phase separation. Additional aluminium was added to the glasses manufactured in the absence of reprocessing waste to improve the durability of the glass. In borosilicate glass containing 3.5 wt% Al2O3 the onset of a molybdenum phase separation was observed in glasses containing 2.6 wt% MoO3. In the presence of Magnox reprocessing waste, phase separation was observed when the product contained >3.8 wt% MoO3. Soxhlet durability testing of a selection of the glasses manufactured was carried out. The Soxhlet durability of glasses in the absence of phase separation was good.

This paper describes the results from static leach tests using the ASTM International standard Materials Characterisation Centre (MCC-1) and Product Consistency Test (PCT) protocols for inactive High Level Waste (HLW) glasses fabricated at full scale on the Sellafield Vitrification Test Rig. The samples comprised monoliths and powders of a 75:25 Oxide:Magnox Blend glass with 31 wt% waste incorporation and a Magnox-only glass with 35 wt% waste incorporation. The tests were carried out in de-ionized water at 90 °C for durations up to 42 days and normalized mass losses calculated.The results of MCC-1 and PCT tests on both 31 wt% Blend and 35 wt% Magnox glasses, showing measurable differences to the corresponding standard 25 wt% waste incorporation glasses, are presented. A series of Scanning Electron Microscopy (SEM) investigations were also undertaken. The variation in composition and thickness of the alteration layer with sample type and duration is reported.

The Sellafield Waste Vitrification Plant (WVP) immobilises highly active liquors produced during reprocessing of spent nuclear fuel by bonding the fission products as metal oxides into a borosilicate glass matrix. This provides a stable and durable waste form suitable for safe long term storage and ultimate disposal.WVP was commissioned with feed from reprocessing of Magnox reactor fuel. This material is relatively low in fission product content per tonne of fuel, but contains significant Al and Mg from fuel cladding. WVP also routinely treats a blended feed made from a mixture of Magnox and Oxide reprocessing products. The Oxide fuel from Light Water Reactor (LWR) and Advanced Gas Cooled (AGR) power stations is of higher burnup and contains more fission products per tonne of fuel, also Gd and other process additives. Blending allows 25% incorporation of waste oxides by weight in glass to be achieved routinely.Recent programmes of development work in WVP have been aimed at increasing incorporation rates for these feeds, to reduce the number of waste containers produced for disposal. Work has also focussed on increasing the throughput of WVP, to more rapidly treat current stocks of liquid reprocessing waste, both by increasing the feed rate and by improving the lifetime of key components to improve plant availability.Future challenges for WVP include flowsheet changes to treat historic stocks of reprocessing wastes containing high U, Fe and Cr. Washout of solids from the base of waste storage tanks in preparation for decommissioning is also likely to give high Mo feeds. Development of flowsheet and glass formulation to accept these changes in feed composition will be a key objective of future work.