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- Ekeroth, Ella, et al.
(författare)
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The effect of temperature and fuel surface area on spent nuclear fuel dissolution kinetics under H2 atmosphere
- 2020
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Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115. ; 531
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Tidskriftsartikel (refereegranskat)abstract
- In this work we present the results of two spent nuclear fuel leaching experiments in simulated granitic groundwater, saturated with hydrogen under various pressures. The results show a large impact of the dissolved hydrogen already at 1 bar H2 and room temperature on the release of both the uranium and of the fission products contained in the fuel matrix. Based on the results of this study and on published data with fuel from the same rod, the importance of the oxidative dissolution of spent fuel under repository conditions as compared to its non-oxidative dissolution is discussed. The XPS-spectra of the fuel surface before the tests and after long-term leaching under hydrogen are reported and compared to reduced UO2 and SIMFUEL surfaces. The overall conclusion is that in spite of the unavoidable air contamination, hydrogen pressures of 1 bar or higher counteract successfully the oxidative dissolution of the spent nuclear fuel. The stability of the 4d-element metallic particles during fuel leaching under such conditions is also discussed, based on data for their dissolution. The metallic particles are also stable under such conditions and are not expected to release their component metals during long-term fuel leaching. © 2020 The Authors
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| 2. |
- Kienzler, Bernhard, et al.
(författare)
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ACTINIDE MIGRATION IN FRACTURES OF GRANITE HOST ROCK : LABORATORY AND IN SITU INVESTIGATIONS
- 2009
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Ingår i: Nuclear Technology. - 0029-5450 .- 1943-7471. ; 165:2, s. 223-240
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Tidskriftsartikel (refereegranskat)abstract
- Within the scope of a cooperation between Svensk Karnbranslehantering AB and Forschungszentrum Karlsruhe, Institut fur Nukleare Entsorgung, a series of actinide migration experiments were performed both in the laboratory and at the Aspo Hard Rock Laboratory in Sweden. The objectives of these experiments were to quantify, the sorption of different actinide elements in single fractures of a granite host rock and to investigate the sorption mechanisms. To guarantee the most realistic conditions-as close to nature as possible-in situ experiments were performed in the Chemlab 2 borehole probe. These migration experiments were complemented by laboratory sorption and migration studies. The latter included batch experiments with flat chips of natural material extracted from fracture surfaces to identify the mineral phases relevant to radionuclide sorption by means of autoradiography. Scanning electron microscopy analyses provided information on the composition of sorption-relevant phases and X-ray photoelectron spectroscopy of Np, Tc, and Fe distribution revealed the redox states of these elements. Important mineral phases retaining all actinides and Tc were Fe-bearing phases. From the migration experiments, elution curves of the inert tracer (HTO), Np(V), U(VI), and to a small extent of Tc(VII) were obtained. Americium (III) and plutonium(IV) were not eluted. The mechanisms influencing the migration of the elements Np, U, and Tc depended on redox reactions. It was shown by various independent methods that Np(V) was reduced to the tetravalent state on the fracture surfaces, thus resulting in a pronounced dependence of the recovery on the residence time. Technetium was also retained in the tetravalent state. Elution of natural uranium from the granite drill cores was significant and is discussed in detail.
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