The 12th International Conference on Environmental ... - Events

Session 34 Abstracts
G) HYDRAULIC BEHAVIOUR OF NUCLEAR WASTE FLOWS - 16376
Simon Biggs, Michael Fairweather, David Harbottle, Bo Lin,James Young, Jeff Peakall, University of Leeds (UK)
A great deal of existing nuclear waste is stored as a solid-liquid slurry, and the effective transportation of solid-liquid systems
is an essential element in the successful implementation of almost all waste treatment strategies involving particulate wastes within
the nuclear industry. A detailed knowledge of turbulent, particle-laden liquid flow behaviour is therefore obviously important.
However, systematic studies of solid-liquid flows by experimental investigation are still limited for pipe flows, contrary to the significant
amount of work available for channel flows. Research work is therefore required to understand the effects physical parameters,
such as particle shape, size and size distribution, and solids concentration, on the properties of solid-liquid systems, particularly
in horizontal pipe flows where particles may settle out of the flow and form solid beds which can potentially lead to pipe blockages.
<strong>The</strong> presence of particles in a turbulent pipe flow also modifies the characteristics of the flow, thereby changing its ability to
maintain particles in suspension
Work is currently underway to examine pipe flows over a Reynolds number range of 5,200-10,040, with varying levels of
solids concentration within the flow. Measurements of the flow and particle characteristics are being gathered using particle image
velocimetry (PIV) and, for high solids concentrations, ultrasound Doppler velocity profiling (UDVP) techniques. Work to date has
demonstrated that the intensity of turbulence with such flows can be significantly affected by the presence of solid particles, with
small particles generally attenuating turbulence levels, while large particles often augment turbulence levels from the pipe centreline
to the near-wall region. In addition, the coagulation of particles into larger agglomerates is also of importance, with data
demonstrating that whilst turbulence levels are influenced and augmented by such agglomerates at low Reynolds numbers, high
turbulence levels at high Reynolds numbers can destroy the agglomerates and reduce their effect on the carrier fluid.
H) ENGINEERING PROPERTIES OF NUCLEAR WASTE SLURRIES - 16378
Simon Biggs, Michael Fairweather, Tim Hunter, Qanita Omokanye, Jeff Peakall, James Young, University of Leeds (UK)
<strong>The</strong> types of particulate systems encountered in legacy nuclear waste slurries are highly complicated, with the aggregation and
flow behaviour being at times very variable. However, deconstructing the complex overall slurry activity to singular particle-particle
interactions can lead to a greater understanding of the mechanisms involved in particle aggregation, and so to predictions of
their settling and flow in nuclear systems. Of particular importance to legacy waste is the role of salts in controlling the attraction
of particles (and so in dictating the rheological properties of the system) as sludges may contain a variety of specific ions and generally
have high ionic conductivity. In this paper, work on the characterisation of particle-particle interactions using a number of
complimentary methods will be described, together with measurements of their influence on the resulting flow and solid bed compression.
<strong>The</strong> methods used to characterise the particle-particle interactions under various salt and pH conditions were firstly, atomic
force microscopy. This device allows quantitative measurement of particle attraction, and so the propensity of particles to aggregate
in different conditions. Particle-particle interactions were also related to zeta-potential measurements, which highlights the
changing surface-charge of particles under various conditions. Most importantly, the individual particle-surface properties were correlated
to the rheological behaviour of suspensions, in particular, the shear and compressional yield stresses, vital parameters in dictating
flow and dewatering performance, respectively. Interestingly, it was found that with certain di- and tri-valent salts there were
specific ion adsorption effects, which altered the expected yield stress relationships and could not be explained by classical valence
theories. Together, these techniques have enabled the characterisation of a range of particulate systems that may be encountered in
legacy wastes, with results pointing to a number of important factors that could help explain the observed variability in industrial
slurry behaviour.
I) RADIOACTIVE WASTE MANAGEMENT IN KENYA - 16366
Anthony Shadrack, Ministry of Health (Kenya)
Many countries have been firmly committed to the peaceful applications of ionizing radiations in medicine, industry, agriculture
and training and research in order to achieve socioeconomic development in diverse sectors. <strong>The</strong> objective of this project is to
highlight the current situation with the storage facilities for the radioactive wastes and disused sealed radioactive sources in Kenya.
In Kenya sealed radioactive sources are used in various socio-economic disciplines such as medicine, industry, research and agriculture.
At the end of their useful lives, these radioactive sources become ionizing radiations waste and can still be dangerous
because they can cause harmful effects to the public and the environment. “Borehole disposal design concept” is used for sitting
up a safe site for storage of radioactive waste for sealed radioactive sources in the country. <strong>The</strong> methodology to be used will involve
using borehole drilling technology that is readily available in the country. <strong>The</strong> design can accommodate disused sources of less than
100mm in length and 16 mm in diameter. It is assumed that the sources are disposed at least 40 m from the ground surface thereby
significantly reducing the probability of the waste being disturbed by human intrusion or other disruptive events and processes.
This document focuses safe management of spent radioactive sources generated from various applications in medicine, agriculture,
training and research and industry. <strong>The</strong> main research facility is situated at the material science branch Ministry of Public Works
(MOPW) which is situated 2 km north of the capital. <strong>The</strong>re are 4 nuclear medicine centers, 3 industrial radiotherapy facilities, 2
gamma irradiator facilities, one linear accelerator, 2 high dose radiation (HDR) Brachytherapy units, 5 industrial radiography units
and several training and research facilities (colleges, universities and secondary schools) in the country. Results are tabled in this
paper to show safe management of radioactive sources in Kenya.
J) THE COMPLEXATION OF TC(IV) WITH GLUCONIC ACID AT HIGH PH - 16381
Sneh Jain, Ricky Hallam, Peter Warwick, Nick Evans, Loughborough University (UK)
In the UK, a technetium containing floc may be disposed of in a high pH, low Eh cementitious repository, whereupon the floc
would degrade by alkaline hydrolysis and/or radiolysis releasing the Tc into the porewater. Its chemistry would then be dominated
by TcO4-, in aerobic waters and the sparingly soluble TcO2(s) in anaerobic. Repository heterogeneity could mean that both Tc(VII)
and Tc(IV) are present simultaneously. If TcO4- migrates into reducing conditions, organic ligands in the waste may complex with
Tc during reduction to form water-soluble complexes. Also possible, is increased Tc solubility when organic ligands react with
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