As part of the reprocessing of uranium oxide spent fuel, the final high-level liquid waste is packaged in glass using a two-stage process, calcination followed by vitrification. Calcination gradually transforms the liquid waste into a dry residue, which is mixed with preformed glass in a melting furnace. The calciner consists of a rotating tube heated by a resistance furnace. The calcined solutions consist of nitric acid and compounds in their nitrate form or insolubles in the form of metal alloys. In order to improve control of the calciner, it is proposed to model it.
The modelling will consist of creating and then coupling three models:
- A thermodynamic model to represent the transformations undergone by the material. This part will almost certainly involve ATD and ATG measurements, coupled with a design of experiments type approach (1st year).
- A material flow model. The literature already contains very simplified principles for representing the flow in a rotating tube calciner, but we will have to be innovative, in particular by defining tests to characterise the flow of the material during the calcination process (2nd year).
A thermal model that will take into account exchanges between the furnace and the calciner tube as well as exchanges between the material and the tube. The exchange coefficients will have to be characterised (1st year).
Combining these three models (3rd year) will give rise to an initial simplified calcination model. This model will be used to help control the calcination stage and also to train operators to control this apparatus.
You will be working in the LDPV, a multidisciplinary team (process, chemistry, fluid mechanics, modelling, mechanics, induction) comprising 16 engineers and technicians. A team with 30 years' experience in vitrification processes, recognised both nationally and internationally.