Americium removal from nitric acid waste streams

Separations research at the Rocky Flats Plant /RFP/ has found ways to significantly improve americium removal from nitric acid/7M/ waste streams generated by plutonium purification operations. Partial neutralization of the acid waste followed by solid supported liquid membranes /SLM/ are useful in transferring and concentrating americium from nitrate solutions. Specifically, DHDECMP /dihexyl-N, N-diethylcarbamoylmethylphosphonate/ supported on Accurel polypropylene hollow fibers assembled in modular form transfers >95% of the americium from high nitrate /6.9M/, low acid /0.1M/ feeds into 0.25M oxalic acid stripping solution. Maximum permeabilities were observed to be 0.001 cm sec^–1, consistent with typical values for other systems. The feed:strip volume ratio shows an inverse relationship to the fraction of metal ion transferred. Cation exchangers may be used to concentrate americium from the strip solution. Furthermore, OØD/iB/CMPO /or CMPO/ /octylphenyl-N,N-diisobutylcarbamoylmethylphosphine oxide/ has been tested in an extraction chromatography mode. Preliminary results show CMPO to be effective in removing americium if the feed is neutralized to 1.OM acidity and iron/III/ is complexed with 0.20M oxalic acid.