Fission product decontamination

Major limitations in fission product decontamination will require tests with mixer-settlers. However, we anticipate from the distribution ratio measurements that Tc, Ru, and Pd will limit the overall decontamination from beta activity (other than from lanthanides). ... 

Fission product decontamination fiactosu o faction 252Crf, 2kl Cm and 21t3Am. 

Fission-product decontamination is restricted by the requirement that gamma-emitting nuclides must remain with uranium-plutonium to provide nuclear deterrence. Various nuclides have been considered, including Co-60, which would be added to... 

Fluoride and aluminum were also included in the feed because they would be needed in an actual dissolution step for ThC (fluoride catalyzes the dissolution, and aluminum counteracts the corrosiveness of the fluoride). For efficient Th extraction, the acidity of the feed solution should be in the range of 2 to 3 mol/L in HNO3. This is a significant departure from the acid Thorex process which uses an acid-deficient feed solution and is reported to. achieve improved decontamination from fission products (8). However, acid-deficient feed solutions were considered undesirable in our flow sheet because Pu hydrolyzes and tends to polymerize at low acidity (9). The effect of the higher feed acidity used here on fission product decontamination has not yet been established but will be assessed in later experiments. 

Plutonium purification proceeds by reducing the aqueous phase pH that oxidizes the plutonium to Pu" +, which then extracts into the TBP phase. Impurities stay in the aqueous phase. The TBP phase strip-ping/extraction cycle is repeated to complete the plutonium purification. The uranium is purified using the same TBP/nitric acid extraction/stripping cycle. Careful control of the each element s oxidation state in the extraction cascade produces the plant-scale separations of uranium from plutonium of 10 . Fission product decontamination factor was 10. The plutonium and uranium recovery is about 99.9% with 95% of the nitric acid values and 99.7 /o of the organic solvent recycled. ... 

The decay of 6.75- y U eliminates the need for remote handling of the purified uranium recovered by fuel reprocessing. Also, presence of high activities of would interfere with monitoring for fission-product decontamination of the recovered uranium. 

Protactinium can be recovered from irradiated thorium, after fission-product decontamination, by exchange onto Dowex 1-X8 anion-exchange resin from i9 M HCl solution. Thorium is then eluted with 9 M HCl, followed by elution of Pa(V) with 9 M HC1-0.2S M HF. Uranium is eluted with 0.25 M HF [Kl, K4]. 

Seaborg s team developed two separation processes to take advantage of the different chemistries of plutonium s several different valence states. One process used bismuth phosphate as a carrier the other used lanthanum fiuoride. Bismuth phosphate, scaled up directly from Met Lab experiments, served the primary purpose of uranium and fission-product decontamination. Lanthanum fiuoride, applied at pilot scale at Oak Ridge, then concentrated the plutonium from the large volume of solution in which it was suspended. 

Overall fission product decontamination is greater than 1 X 10 U carry-through is less than 0.05%. 

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