During Fukushima Daiichi nuclear reactor accident, several hundred tons of fuel debris (the mixture generated by the reactor core melting and its interaction with structural materials) have been formed. Japanese government plans to dismantle with 30 to 40 years Fukushima Daiichi nuclear power station, which implies recovering these fuel debris.

CEA is participating with French partners to several projects funded by the Japanese government aiming at developing fuel debris cutting. Mastering the risks due to radioactive aerosols generated during these operations is one important aspect of this R&D. In this framework, CEA has fabricated fuel debris prototypes corresponding to chemical compositions that have been estimated for these severe accidents. The French consortium has collected and analysed the aerosols produced during mechanical cutting as well as during high temperature heating simulating thermal cutting.

For thermal cutting, an important source of aerosol seems to be partial evaporation/condensation of many chemical species that are present in the fuel debris. A thermodynamic modelling shall be proposed, using the NUCLEA or TAF-ID thermodynamic databases, coupled with some kinetic effects.

For mechanical cutting, relations between the phases observed on the bulk samples and the observed aerosols will be considered in view of determining a phenomenological understand and in a second stage modelling it. Then, the observed of the cutting atmosphere (humidity, air vs. nitrogen) should be explained and its mechanisms could be quantified.

Your missions would be:

—     a bibliographical study in which, in addition to the state of the art on aerosols produced by mechanical and thermal cutting, there shall be a comparison with the literature dedicated to radioactive aerosol release during severe accidents.

—     a critical synthesis of the experimental results achieved by this French consortium that encompass several fuel debris simulant block compositions.

—     chemical or crystallographic analyses of some samples already in the laboratory but not yet analysed.

—     model development for fuel debris aerosols generation and transformation phenomena, in particular, evaporation/condensation during thermal processes and/or agglomeration of aerosol particles.

PhD or equivalent in material engineering, aerosol science, chemical thermodynamics and/or nuclear engineering.