Joshua T Radford
<jtradford1@sheffield.ac.uk>

Josh completed a Bachelor’s degree in Aerospace Engineering at the University of Sheffield in 2016. His dissertation project investigated the use of glass fibre composites for self-sensing aerospace components. The project sparked an interest glass science leading Josh to apply for a PhD in nuclear waste immobilisation. Now in the 2nd year of his PhD, Josh’s research has concentrated on the modification of glass compositions to assess the effect on caesium volatility.


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Investigating The Effect Of Glass Chemistry On The Volatility Of Caesium
Josh Radford1, Charlie Scales2, Claire L. Corkhill1, Russell J. Hand1
1Immobilisation Science Laboratory, Department of Material Science and Engineering, University
of Sheffield, Sir Robert Hadfield Building, Mappin Street, S1 3JD

2National Nuclear Laboratory 5th Floor, Chadwick House, Warrington Road,
Birchwood Park, Warrington, WA3 6AE

As the world’s energy demand is predicted to continually rise, the need for cleaner energy has seen a rise in profile. Nuclear energy has the potential to fill the void in the energy market left by the phasing out of traditional fossil fuel burning power stations. However, a major concern for nuclear power is the long-lived radioactive waste produced. High level waste (HLW) from fuel reprocessing has taken priority and the process of vitrifying the UK’s HLW stockpile is already underway. The preferred treatment option for intermediate level waste (ILW) is currently cementation, but not all ILWs are suitable for cementation. Another treatment option for ILW is thermal treatment, such as a vitrification process similar to the process currently used for HLW. The challenge for ILW arises from the diversity of the chemical makeup of ILW, in particular, the range of volatile elements poorly suited to the traditional borosilicate glasses used for vitrifying HLW [1]–[3]. In light of this, a large amount of research is being conducted investigating the effects of different processing conditions on the retention of various volatile components [4]–[6]. Of particular interest are 137Cs and 90Sr as the total radioactivity of these two radionuclides accounts for almost half of the total radioactivity produced by ILW [7]. To investigate the effect of glass chemistry on the volatility of caesium, a series of iron phosphate glasses (IPGs) have been produced using the standard melt quench method. The target compositions for these glasses are (1– x)40Fe2O3.60P2O5.xRyOz. where 0<x<10 and R= Mn, Zn and B. All samples were characterised using a standard suite of techniques including DTA, Raman spectroscopy, Mössbauer spectroscopy, XRF, SEM-EDX and XRD. Following characterisation, 75g of each sample was crushed and passed through a 150µm aperture sieve. The powders were then re-melted with a 1-2g addition of caesium carbonate in the experimental set-up shown in Figure 1 and Figure 2. Upon completion, the complete apparatus was washed through with a small quantity of 0.1M HNO3. The elemental caesium concentration of this solution was then analysed using ICP-MS and combined with XRF analysis of the bulk glass composition to give complete mass balance of the caesium distribution.

Figure 1: Experimental Set-up for caesium doped glass melts

Figure 2: A sealed stainless steel ‘HIP’ canister used in volatility experiments

References:

[1]         J. S. McCloy, ‘Rhenium solubility in borosilicate nuclear waste glass’, Lawrence Berkeley National Laboratory, Berkeley, CA, LBNL-6497E, 2012.
[2]         D. S. Kim et al., ‘Development and Testing of ICV Glasses for Hanford LAW’, PNNL, Richland, WA, PNNL-14351, 2003.
[3]         A. A. Kruger, K. A. Matlack, I. L. Pegg, and W. Gong, ‘Final Report – Glass Formulation Testing to Increase Sulfate Volatilization from Melter’, ORP, Richland, WA, VSL-04R4970-1, 2013.
[4]         D. Banerjee, A. Joseph, V. K. Sudarsan, P. K. Wattal, and D. Das, ‘Effect of composition and temperature on volatilization of Cs from borosilicate glasses’, J. Am. Ceram. Soc., vol. 95, no. 4, pp. 1284–1289, 2012.
[5]         B. G. Parkinson, D. Holland, M. E. Smith, A. P. Howes, and C. R. Scales, ‘Effect of minor additions on structure and volatilization loss in simulated nuclear borosilicate glasses’, J. Non. Cryst. Solids, vol. 353, no. 44–46, pp. 4076–4083, 2007.
[6]         A. Vegiri, C. E. Varsamis, and E. I. Kamitsos, ‘Composition and temperature dependence of cesium-borate glasses by molecular dynamics’, J. Chem. Phys., vol. 123, no. 1, pp. 14508, Jul. 2005.
[7]         Nuclear Decommissioning Authority, ‘Radioactive Wastes in the UK : UK Radioactive Waste Inventory Report.’, NDA, 2017.