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Improved understanding of the structure/activity relationship of inhaled anaesthetics has resulted in the synthesis of fluorinated compounds which are more potent and less toxic than their unfluorinated antecedents. The toxic effects of inhaled anaesthetics on the liver and kidney are complex but, in general, are related to the extent to which individual inhaled agents are metabolised. Halothane hepatotoxicity is a rare, idiosyncratic reaction which typically occurs in obese women having more than one exposure to the drug within a short time interval. All currently available volatile anaesthetic drugs have depressant effects on the cardiovascular and respiratory systems; arrhythmias are more likely with halothane than with the fluorinated ethers. Cerebral blood flow tends to increase during inhalation anaesthesia, especially with halothane and in the presence of hypercarbia; isoflurane may be given sparingly during neurosurgical procedures whilst monitoring its end-tidal concentration. Although the volatile agents tend to cause uterine relaxation they may be given safely in low concentration to avoid awareness during Caesarean section. In general, young children require rather higher concentrations of volatile agents than adults and seem to be less susceptible to organ toxicity. Two relatively new volatile agents, sevoflurane and desflurane, offer some advantages over isoflurane but neither is an "ideal drug'. Sevoflurane interacts with soda-lime to produce a series of degradation products, the most important of which is compound A. Production is greatest during low-flow, closed circuit anaesthesia using high inspired concentrations of the drug. Compound A has nephrotoxic potential in rats but the clinical significance of the interaction between sevoflurane and soda-lime is unclear. Nitrous oxide when given for prolonged periods may cause irreversible bone marrow depression.

The US Department of Energy awarded Oak Ridge National Laboratory a program to develop a cost-risk-benefit analysis of partitioning long-lived nuclides from waste and transmuting them to shorter lived or stable nuclides. Two subtasks of this program were investigated at Rocky Flats. In the first subtask, methods for solubilizing actinides in incinerator ash were tested. Two methods appear to be preferable: reaction with ceric ion in nitric acid or carbonate-nitrate fusion. The ceric-nitric acid system solubilizes 95% of the actinides in ash; this can be increased by 2 to 4% by pretreating ash with sodium hydroxide to solubilize silica. The carbonate-nitrate fusion method solubilizes greater than or equal to 98% of the actinides, but requires sodium hydroxide pretreatment. Two additional disadvantages are that it is a high-temperature process, and that it generates a lot of salt waste. The second subtask comprises removing actinides from salt wastes likely to be produced during reactor fuel fabrication and reprocessing. A preliminary feasibility study of solvent extraction methods has been completed. The use of a two-step solvent extraction system - tributyl phosphate (TBP) followed by extraction with a bidentate organophosphorous extractant (DHDECMP) - appears to be the most efficient for removing actinides from saltmore » waste. The TBP step would remove most of the plutonium and > 99.99% of the uranium. The second step using DHDECMP would remove > 99.91% of the americium and the remaining plutonium (> 99.98%) and other actinides from the acidified salt waste. 8 figures, 11 tables.« less

Field-flow fractionation (FFF) is a proposed separation method in which some kind of lateral field is coupled with nonuniform axial flow to induce differential migration (1). Fractionation is here illustrated by applying a temperature drop laterally across a narrow tube within which a mixture is flowing. In this case thermal diffusion is responsible for lateral enrichment. This variation of the general concept may be termed thermal field-flow fractionation.