Solids loading evaluation for HB-line scrap recovery filters

The HB-Line Scrap Recovery facility uses wire screen filters to remove solids from plutonium-containing solutions transferred from the slab tank dissolvers. At times, the accumulation of solids is large enough to cause blinding (i.e., pluggage) of the filters. If the solids contain undissolved plutonium, significant accumulation of fissile material could impact operations. To address this potential issue, experiments were performed to define the minimum solids required to completely blind a filter. The solids loading experiments were performed by arranging 25- and 10-microm HB-Line filters in series to simulate the equipment in the scrap recovery process. Separate tests were performed using coarse and fine glass frit and cerium oxide powder suspended in 35 wt% sodium nitrate solution using a small turbine mixer. The solution and solids were transferred from a reservoir through the filter housings by vacuum. In each case, the 25-microm filter blinded first and was full of wet cake. After drying and accounting for the sodium nitrate in the filter cake, the following results were obtained. The results of the solids loading tests demonstrated that at least 800 g of solids accumulated in the filter housing before flow stopped. The actual amount of collected material was dependent upon the physical properties of the solids such as density and particle size. The mass of solids collected by the blinded 25-microm filter increased when successively finer solids were used in the experiments. Based on these results, one should anticipate that filters in the HB-Line Scrap Recovery Facility have the potential to collect similar quantities of material before transfer of solution from the dissolvers is severely impacted