Characterization method of dielectric properties of free falling drops in a microwave processing cavity and its application in microwave internal gelation

[EN] Microwave internal gelation (MIG) is a chemical process proposed for the production of nuclear particle fuel. The internal gelation reaction is triggered by a temperature increase of aqueous droplets falling by gravity by means of non-contact microwave heating. Due to the short residence time of a solution droplet in a microwave heating cavity, a detailed knowledge of the interaction between microwaves and chemical solution (shaped in small drops) is required. This paper describes a procedure that enables the measurement of the dielectric properties of aqueous droplets that freely fall through a microwave cavity. These measurements provide the information to determine the optimal values of the parameters (such as frequency and power) that dictate the heating of such a material under microwaves.This work is a part of the PINE (Platform for Innovative Nuclear FuEls) project which targets the development of an advanced production method for Sphere-Pac fuel and is financed by the Swiss Competence Center for Energy and Mobility. The work has been also financed by the European Commission through contract no 295664 regarding the FP7 PELGRIMM Project, as well as contract no 295825 regarding the FP7-ASGARD Project. MC-S would like to thank the ITACA research team (UPV Valencia, Spain) and the EMPA Thun (Switzerland) for their support in the measurements and Carl Beard (PSI, Switzerland) for the help provided in respect with CST simulations. The work of FLP-F was supported by the Conselleria d'Educacio of the Generalitat Valenciana for economic support (BEST/2012/010).Cabanes Sempere, M.; Catalá Civera, JM.; Penaranda-Foix, FL.; Cozzo, C.; Vaucher, S.; Pouchon, MA. (2013). Characterization method of dielectric properties of free falling drops in a microwave processing cavity and its application in microwave internal gelation. Measurement Science and Technology. 24(9). https://doi.org/10.1088/0957-0233/24/9/095009S24

Microwave Assisted Internal Gelation of Droplets - A Case Study

A microwave unit for internal gelation of metal nitride solutions at 2.45 GHz microwave radiation is presented. In the majority of cases previous investigations examined the use of frequencies in the x-band range (6 to 12 GHz). The challenge of the recent work is to apply 2.45 GHz ISM frequency instead. A microwave unit was selected and designed with the final goal of its implantation in a "glovebox", where radio-active materials are handled. Microwave radiation is supplied by a 2 kW coaxial line, which eventually can be fed through the glovebox wall, thereby permitting the microwave source to be located outside of the glovebox. Droplets of the metal nitride solution are allowed to fall by gravity through the resonator while being heated by microwave energy. Due to the very short residence times of the droplets in the resonator, the drop generating nozzle is introduced directly into the microwave field. By this means the residence time is increased due to the time of droplet formation at the nozzle tip.JRC.E.4-Nuclear fuel

Microwave ponderomotive forces in solid-state ionic plasmas

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