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- Brown, Paul, et al.
(författare)
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Solubility of Radium and Strontium Sulfate across the Temperature Range of 0 to 300℃
- 2014
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Ingår i: Uranium Mining and Hydrogeology 2014. - 9783319110592 ; , s. 553-563
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Konferensbidrag (refereegranskat)abstract
- Solubility constant data for radium and strontium (celestite) sulfate has been determined across the temperature range of 0 to 300℃ based on the available literature data for these two phases as well as similar data for calcium (anhydrite) and barium (barite) sulfate for which solubility constant data is available acrossthe same temperature range. The thermodynamic data for the phases have been determined by assuming that the solubility constants are a function of the inverse ofabsolute temperature with a constant, but non-zero, heat capacity change. The solubility for all phases shows a peak with respect to temperature, with the temperature at which the peak occurs increasing as the alkaline earth metals become heavier. The heat capacity change is a function of the ionic radius of the alkaline earth metal ion whereas the enthalpy of reaction at 25℃ is related to the peak at which the maximum solubility occurs. The entropy of reaction at 25℃ is related to the solubility constant and the derived enthalpy of reaction at that temperature.
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| 6. |
- Hansson, Niklas, 1992, et al.
(författare)
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Geometrical aspects of alpha dose rates from UO2 based fuels
- 2022
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Ingår i: Radiation Physics and Chemistry. - : Elsevier BV. - 0969-806X .- 1879-0895. ; 199, s. 110336-
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Tidskriftsartikel (refereegranskat)abstract
- Models for calculating dose rates of spherical particles as well as in fuel cracks are important for radionuclide source term estimations. Dose rates from UO2 based fuels were calculated for planar, spherical, and crack geometries. The escape probability for a-particles in spherical UO2 particles was derived as a continuous equation. The dose rate increased with increasing spherical radius due to the decreasing relative volume of the surrounding water layer. The model produced escape probabilities that were closely predicted by the theoretical derivation. It was shown that the dose rate in water filled fuel cracks with width smaller than the range of an alpha-particle led to dissolution rates that were lower per unit surface area.
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| 8. |
- Hedström, Hanna, 1983, et al.
(författare)
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A study of the Arrhenius behavior of the co-precipitation of radium, barium and strontium sulfate
- 2013
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Ingår i: Journal of Radioanalytical and Nuclear Chemistry. - : Springer Science and Business Media LLC. - 0236-5731 .- 1588-2780. ; 298:2, s. 847-852
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Tidskriftsartikel (refereegranskat)abstract
- Co-precipitation of radium, barium and strontium is an important process in many contexts, such as uranium mining, oil extraction and in the safety assessment of a final repository for used nuclear fuel. Co-precipitation to a solid solution is possible since radium, barium and strontium act as chemical analogues. In this work the co-precipitation of radium, barium and strontium was studied and the kinetic behavior of the co-precipitation process was investigated. It was shown that radium, barium and strontium co-precipitate congruently and that the precipitation followed an Arrhenius behavior and the Arrhenius parameters for the systems was determined. When studying the differences of the Arrhenius constants by using a student t test (95 % confidence interval) it was observed that the only significant difference in the activation energy, E (a), is between radium and barium and between radium and strontium respectively, the pure strontium having the larger activation energy in comparison. This is most likely coupled to the metal ion size; since the hydration waters are more strongly bound, which leads to them having a slower exchange rate, which in turn effects the rate of co-precipitation to the metal these reactions will be slower.
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| 9. |
- Hedström, Hanna, 1983, et al.
(författare)
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Radon capture with silver exchanged zeolites
- 2012
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Ingår i: Radiochimica Acta. - : Walter de Gruyter GmbH. - 0033-8230 .- 2193-3405. ; 100:6, s. 395-399
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Tidskriftsartikel (refereegranskat)abstract
- To enable laboratory work with larger amounts of Ra-226 and its decay products, e.g., Rn-222 and its daughters, these need to be captured in order to avoid unnecessary alpha contamination of the laboratory work space and ventilation systems. In this study, radon gas was pumped through a column filled with the silver exchanged zeolite called "silver exchanged molecular sieves 13X" (Ag84Na2[(AlO2)(86)(SiO2)(106)]. xH(2)O). After exposure to radon, the radioactivity of the zeolite was measured repeatedly using high resolution gamma spectrometry. It was shown that radon was captured and retained in the silver exchanged zeolite. The zeolites' ability to retain radon was decreased by formation of metallic silver, caused by ionizing radiation. However, the zeolite was regenerated by heating and its radon capture ability was restored. The daughters of radon are not in gas phase and will hence stay on the column.
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