Cementation in High Energy Mixer of ILW Surrogate Slurry. Demonstration of the Process at Semi-industrial Scale

Abstract

To optimize the control and reliability of the slurry cementation procedure and technologies to be implemented in the future Liquid Effluent Treatment Station (STEL) at Marcoule by 2015, the French Energy Commission (CEA) has undertaken an extensive development program on a semi-industrial scale cementation pilot platform. The technological lessons learned will provide a basis for the definition of the industrial process.

At the CEA, the Process Cycle Advanced Technology Laboratory (within DEN/MAR/DTEC/SDTC) is in charge of the technological choices implemented and the definition of this platform, as well as the procedure qualification tests. Given the variable rheological properties of the slurry, which can be very pasty, the mixer technology chosen concerned a high energy mixer in order to obtain a homogeneous cement mixture. In addition, the requirements of cement matrix drainage by the force of gravity and integrated automatic cleaning were expressed and taken into account as of the design stage of the platform which has now been built and comprises these very innovative specific features.

The first part of this publication is devoted to the description of the facility and specific apparatus. The experimental platform comprises three levels representing a surface area of approximately 200m². The layout is similar to that of the industrial workshop. The upper level is for batching and introducing the various components in the mixer installed on the intermediate level. The lower level is reserved for the docking and maintenance of the canisters. A characterization laboratory also forms part of the platform.

Section two gives a precise description of a cementation test performed that demonstrates the production of a full-scale container. The raw materials used are those that are taken into consideration for industrial operation; the slurry used on the platform is radiologically inactive and, in particular, is prepared following the same procedure as that used in the Liquid Effluent Treatment Station (STEL) at Marcoule. The flow and time charts of the various phases of the test are described in detail, as are the parameters of the procedure applied to control the mixer in particular but also the production of the liquid cement.

In the third chapter, we describe the R&D that was undertaken to ensure the quality of the container produced. Specifically, thermocouples were incorporated into the container, distributed at the core, peripherally and on the wall of the drum at various levels. These acquisitions made it possible to map the drum temperatures while the cement mix sets. The containers were core sampled in order to perform mechanical tests and appraisals. At the same time, characterizations on test specimens in the laboratory by Langavant calorimetry, Vicat setting indicator, and rheometer ensure coherence of all of the results.

In conclusion, all of the knowledge acquired on the basis of a test of this type opens up the prospect of new R&D described briefly with a view, eventually, to being able to ensure not only nominal operating conditions but also satisfactory management of transient and impaired conditions.