10.2172/814127

The conversion of the uranium hexafluoride (UF{sub 6}) which is removed from the Molten Salt Reactor Experiment (MSRE), into a stable oxide for long-term storage will produce a significant amount of slightly contaminated, concentrated aqueous hydrofluoric acid (HF). Sin&the handling of this HF is complicated and dangerous, it was decided to transform it into a stable solid fluoride (e.g., CaF{sub 2}, AlF{sub 3}, and MgF{sub 2}). Tests have been performed to identify the best media to use for trapping the HF. These tests are described in this report. The first series of tests evaluated 37 trapping materials using a 6 wt % solution of HF. The solution was pumped through a 3.8-cm-diam column at a slow rate, and samples were taken in 100-mL batches until it was determined that the media could no longer neutralize the solution. Each bed volume of media was evaluated for its retention of fluoride and for its plugging problems. Mixtures of calcium hydroxide and blast furnace slag (BFS) with high Surface areas (18-30 mesh) performed the best. A mixture of 80 wt % calcium hydroxide and 20 wt % BFS was capable of loading 0.134 g HF per cubic centimeter (cm{sup 3}) of media. Other media that performed well were (a) mixtures of calcium hydroxide and portland cement and (b) pure calcium hydroxide. The second series of tests evaluated media using a 33 wt % HF solution. The best performing media from the first series and some new ones were tested. A 2.54-cm-diam, clear, polyvinyl chloride pipe was used as the column, and solution was introduced to different types or sizes of media using slugs from a pipette or constant flow of {approx}10.7 mL/min from a metering pump. The transparent PVC allowed for observation of acid-media interaction and provided a glimpse into how the media and cartridge were performing in this highly corrosive environment. Results from the second series of tests showed that many of the best performing media from the first series of tests would not do well under the more concentrated solutions of HF. Plugging and vigorous reactions were common in the second series, and calcium hydroxide-based media was ruled out due to its disintegration at any size (1.25-cm diam to 30 mesh). The best performing media was mid-sized (4-18 mesh) soda and lime (soda lime). This media not only stood up well in the HF solution, but it also had great neutralization capability, effectively neutralizing up to {approx}0.5 g HF/cm{sup 3} of media. It is expected that a cartridge of this sorbent will be capable of handling approximately seven batches of HF from the uranium conversion.

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