Browsing by Author "Panias, Dimitrios"

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Distribution of uranium, thorium and potassium in the Bayer process
(2nd Bauxite Residue Valorisation and Best Practices Conference, 2018) Goronovski, Andrei; Vind, Johannes; Vassiliadou, Vicky; Panias, Dimitrios; Tkaczyk, Alan Henry
Uranium, thorium, potassium and their decay product mass flows were analysed in the Bayer process. Gamma-ray spectroscopy was used to measure the radionuclide content in samples provided by Aluminium of Greece and to model their mass flows. We observed that at any analysed stage, the radionuclide content does not exceed the allowed safety limits set in the European Basic Safety Standard. Another important observation is that a minor portion of uranium from bauxites (3%) ends up in alumina, while the rest is accumulated in the bauxite residue (BR). All of the 226Ra (long-lived decay product of uranium), as well as all decay products of thorium accumulated in the BR. We observed accumulation of 40K in the process liquors, while this radionuclide was not found in the alumina.
Radiological assessment of the Bayer process
(Minerals Engineering, 2019-04-13) Goronovski, Andrei; Vind, Johannes; Vassiliadou, Vicky; Panias, Dimitrios; Tkaczyk, Alan Henry
Naturally occurring radionuclides were studied through the Bayer process by calculating their mass flows. Aluminium of Greece (AoG) provided sample materials and plant data from several process stages. Measurements of radionuclide concentrations were carried out by gamma-ray spectroscopy. The performed measurements show that in the specific case of the AoG plant, the majority of the natural radionuclides were introduced with karst bauxites, which showed higher activity concentrations for nuclides compared to lateritic bauxites. Most of these nuclides accumulated in the bauxite residue, while only a minor portion of uranium isotope 238U was found in alumina, corresponding to 3% of its input value. Uranium was observed to partially dissolve in the process liquors similarly to 40K, whereas the latter was not associated with aluminium hydroxide. All the materials studied in the current research work had radionuclide concentrations well below the exemption limits set by EURATOM Basic Safety Standard, indicating that these naturally occurring radionuclides do not pose a radiological hazard for workers of the AoG plant or the public.