Long term oxidation tests below 150°C on dimethyl silicone (DMS) fluids with controlled iron content, in conjunction with previous work, have provided a broad concept of the processes of oxidation in DMS fluids between 70 and 370°C. A nonfree radical, iron‐catalyzed oxidation of DMS fluid occurs both below and above 150°C. A diverging, free radical chain reaction which is inhibited by iron is initiated by direct attack of oxygen on the methyl groups of DMS above 150°C. It is believed that a ferric iron complex is the key mechanistic species both in the catalyzed oxidation and in the free radical reaction inhibition. When temperature, iron dispersion, and aeration are held constant, the oxidation rate of a DMS fluid below 150°C varies directly with its iron level. Above 150°C the oxidation rate is still dependent on iron level, but an ‘optimum iron level’ for a minimum oxidation rate exists for each temperature of oxidation. This optimum iron level increases with the temperature. A conceptual diagram has been developed to unify and summarize these effects over the temperature range 70–370°C, providing a basis for the most effective use of iron to stabilize DMS fluids.

Disposal of trace amounts of Zn(65) is made in the Columbia River via Hanford reactor effluent water. The subsequent utilization of river water for irrigation permits the concentration of this radioisotope in farm produce and its eventual deposition in man. The Zn(65) in irrigation water, in farm produce, and in individuals utilizing these materials has been measured.

New spectrometric techniques for the multidimensional counting of gamma rays permit the direct measurement of twelve radionuclides collected on air filters. Observed concentrations of Be(7), Na(22), Mn(54), Co(60), Y(88), Zr(95)-Nb(25), Ru(166), Sb(124), Sb(125), Cs(134), Cs(137), and Ce(144) during the past 2(1/2) years help to explain the origin and fallout rates of the trace radionuclides in air.

Some radioisotopes introduced into the Columbia River via effluent water from reactors at Hanford, Wash., are found in crops irrigated with this water and in sea food harvested near the mouth of the river. Measurements of zinc-65 and chromium-Si in foods and in individuals consuming these foods are reported and are compared with zinc-65 concentrations resulting from fallout.

The 1978 Annual Report from Pacific Northwest Laboratory (PN~) to the DOE Assistant Secretary for Env ironment is the fi rst report cover i ng a fu 11 vear' s \'lOrk under the Department i)f Energy since it came into e(istence on October 1, 1977. Most of the research conducted during this period and described in this report was begun under the Energy Research and Development A~ninistration or its predecessor agency, the Atomic Energy Commission. However, several new projects have enhanced the PNL emphasis on environment, health and safety research in the area of synthetic fuels. Preliminary reports on these efforts are spread throughout the five parts of this annual report. The five parts of the report are oriented to partiCillar segments of our program. report on research performed for the DOE Office of Health and Environment31 Research. Parts 1-4 Part 5 reports progress on all other research performed for the Assistant Secretary for Environment including the Office of Technology Impacts and the Office of Environmental Compliance and Overv i evi. Each part consists of project reports authored hy scientists from several PNL research departments, reflecting the interdisciplinary nature of the research effort. Parts 1-4 are organized primarily by energy technology, although it is recognized that much of the research performed at PNL is applicable to more than one energy technology.