Ph.D. Fellowship on ‘Redox reactivity of Selenium in environmental geomedia’ - Grenoble (France) and Dresden (Germany).

Research supervisors

– Dr. Alejandro Fernandez-Martinez (ISTerre, CNRS & Univ. Grenoble Alpes, France)
– Dr. Norbert Jordan (Helmholtz-Zentrum Dresden -Rossendorf (HZDR), Germany)
– Prof. Laurent Charlet (ISTerre, CNRS & Univ. Grenoble Alpes, France)
– ANDRA Engineers (Paris, France)

Context

Production of electricity by nuclear power plants inevitably generates radioactive waste. Concerning the high-level and long-lived radioactive waste, a solution considered by the French and German nuclear waste management agencies is to store them into deep underground repositories. The principle of such a concept is to provide a multi-barrier system with several matrixes to avoid the release of the radioactive waste through the biosphere for very long time scales (up to hundred thousand of years). Long-term safety assessments require a characterization at both macroscopic and molecularlevel of the different processes (retention, reduction, surface precipitation,etc.) that can take place onto the involved solid surfaces and the considered radioactive pollutants. Among them, the 79Se isotope (∼3.27 × 105a) is considered as one of the main radionuclides contributing to the dose-to-man after final disposal.

Selenium can have different oxidation states (-II, -I, 0, +IV, and +VI). The -II, -I and 0 states arecommonly predominant in “reducing” anoxic environments, while the +IV and +VI statespredominate in “oxidizing” environments. In the reducing geochemical environment of the Callovo-Oxfordian (deep clay formation selected for the location of the French deep geological repository Cigeo), selenium is thus expected to be thermodynamically stable in solution in redox states ranging from0 to -II. The solubility of selenium depends on the oxidation state: (a) Se(+VI) and Se(+IV) highlysoluble (solubility not controlled by a mineral phase); (b) Se(0), extremely poorly soluble nativeselenium; and (c) Se(-I) and Se(-II): poorly soluble but significantly more soluble thanSe(0). The transition from one oxidation state to another may therefore be accompanied by changes insolubility.

The thesis research will focus on the redox reactions and coupled precipitation of selenium (VI) and selenium (-II) under the conditions of the Callovo-Oxfordian pore waterand, namely, in the presence of steel corrosion products such as magnetite, which are also widespread environmental minerals. These reactions will be characterized by means of batch sorptionexperiments, and lab-based and synchrotron-based scattering and spectroscopicmethods.

BenefitsThe student is expected to spend periods of time both in Grenoble (France) and Dresden (Germany). At the end of the Ph.D. period, the candidate will acquire a detailed experience on the environmental molecular geochemistry of selenium, on detailed studies of mineral/fluid interfaces as well as a strong ability to work alone in the laboratory. She/He will increase her/his knowledge on analytical chemistry, inorganic chemistry, and spectroscopy. The candidate will participate to several national and international conferences, and is expected to publish its results in peer-reviewed international scientific journals.

Requirements

The candidate must have a degree in Engineering or have a Master or Diploma of Chemistry, Physical-chemistry or Geochemistry obtained before the beginning of the Ph.D. thesis ( April 2022). She/He must come from a country member of the European Union. The candidate will be offered a competitive salary. The duration of the Ph.D. thesis is 3 years. Candidates must have experimental capabilities for laboratory experiments, and must be able to work within an international and multidisciplinary team. She/He must have good communication skills and speak English fluently. Applications including curriculum vitae, statement of interest, and marks of the master will be evaluated until filling of the position.

Position open until filled.

– Dr. Alejandro Fernandez-Martinez
ISTerre, CNRS & Université Grenoble Alpes
1381 ruede la Piscine | 38041 Grenoble Cedex 9 | France
Phone: +33 4 76 63 51 97
E-mail: alex.fernandez-martinez univ-grenoble-alpes.fr

– Dr. Norbert Jordan
Institute of Resource Ecology
Helmholtz-Zentrum Dresden -Rossendorf (HZDR)
Bautzner Landstr. 400 | 01328 Dresden | Germany
Phone: +49 351 260 2148
E-mail: n.jordan hzdr.de

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