DuringFukushima Daiichinuclear 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.

CEAis participating with French partners to several projects funded by the Japanese government aiming at developing fuel debris cutting. Mastering the risks due to radioactiveaerosolsgenerated 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 partialevaporation/condensationof many chemical species that are present in the fuel debris. A thermodynamic modelling shall be proposed, using the NUCLEA or TAF-IDthermodynamicdatabases, 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:

— abibliographical studyin 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.

— acritical synthesis of the experimental resultsachieved by this French consortium that encompass several fuel debris simulant block compositions.

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

—model developmentfor fuel debrisaerosols generation and transformationphenomena, in particular, evaporation/condensation during thermal processes and/or agglomeration of aerosol particles.