Development of partitioning method

The filterability of slurry prepared by heating under reflux condition and denitration of simulated high level liquid waste (HLLW) was examined, using a preliminary test apparatus for assessment of partitioning process. This apparatus can be treated maximum 10L of simulated HLLW at one operation, and a filterability of the slurry can be examined on an engineering-scale. Two kinds of simulated HLLW were prepared for the filtration test. One had no solid particles, and the other contained solids particles, which were formed in the solution by aging for 2 years and 5 months at ambient temperature. In the case of the simulated HLLW without solid particle, 'easy-to-filter' slurry was obtained by refluxing the simulated HLLW before denitration until the total heat input exceeded 5.7 x 106 [J/L]. The experimental results agreed with those of our small-scale tests. On the other hand, 'difficult-to-filter' slurry was formed when the simulated HLLW containing solid particles was refluxed and denitrated under the similar conditions to above mentioned ones. In this case, separation of solid particles was attained by a 'filter-aid filtration'. Decreasing of the filtration rate was due to the fine particles of about 0.5 μm diameter suspended in the slurry. These fine particles would be formed by longtime aging of the simulated HLLW at ambient temperature. (author)