No abstract

Optically high quality coatings of fluoride materials are required in deep ultraviolet (DUV) lithography. We have applied ion-beam sputtering (IBS) to obtain fluoride films with smooth surfaces. The extinction coefficients were of the order of 10(-4) at the wavelength of 193 nm due to the reduction of their absorption loss. The transmittance of the MgF2/GdF3 antireflection coating was as high as 99.7% at the wavelength of 193 nm. The surfaces of the IBS deposited films were so smooth that the surface roughness of the A1F3/GdF3 film was comparable with that of the CaF2 substrate. The MgF2/GdF3 coating fulfilled the temperature and humidity requirements of military specification. Thus, the IBS deposited fluoride films are promising candidate for use in the DUV lithography optics.

Groundwater geochemistry at the Koongarra uranium ore deposit was investigated in order to gain a detailed understanding of the migration of uranium in a highly weathered water-rock system . Koongarra groundwaters are quite dilute with the total dissolved solids usually below 200 mg/1. The pH is slightly acidic or neutral, and the major chemical characteristics are dominated by magnesium and bicarbonate . Partial pressures of CO2 in the deeper groundwaters are substantially elevated relative to those of surface waters. Groundwater in the mineralized zones exhibits elevated levels of uranium up to three orders of magnitude above background levels. Total organic carbon levels are generally low , suggesting that uranium complexation by organic species plays a minor role. Due to the high bicarbonate concentration , uranium appears to be mobile in the weathered zone as uranyl carbonate complexes . Other inorganic uranium complexants are not present at levels sufficient to influence uranium speciation , with the possible exception of phosphate.On the basis of chemical and isotopic evidence, there are two major inputs of groundwater to the system. The first of these is flows from the vicinity of the Koongarra fault into the Cahill formation , which hosts the uranium mineralization. A second major source is infiltrating waters which permeate downward from the surface, and cause a gradual mixing and dilution of the characteristics of groundwaters from the mineralized zone. The migration of uranium in groundwater is not only perpendicular to the fault, but includes a component at an angle to it . In the vicinity of borehole C 1 (due south of the ore zone), uranium concentrations are comparatively high , given the distance from the orebody. Moving away from the ore zone to the south-east, there is a gradual decrease of groundwater uranium concentrations t o b ackground levels over approximately 200 meters , which coincides. with the uranium distribution in the solid phase. Therefore, at Koongarra, uranium seems to have migrated over distances of approximat ely 200 m toward the south-east over a time period estimated to be 1 to 1 .5 million years.

The solubility of neptunium(IV) hydrous oxide in water and NaC10 4 solutions was measured from over-and undersaturation directions at 25.0±0.2°C over a pH range of 5.30 to 13.7, in the presence of reducing agents (Na 2 S 2 04, metallic Fe or metallic Cu). Equilibration periods ranged from 1 to 119 days. All procedures were performed in a controlled atmosphere in a chamber containing high purity Ar (<1 ppm 0 2 ). Steady concentrations appeared to be reached within 28 days from the over-and undersaturation directions in dilute solutions (water and 0.1 M NaC10 4 ), with the Np(IV) concentrations reaching approximately the same value (10~7-10~8M) from both directions. However, the concentrations decreased slowly to less than 10" 9 M over subsequent periods of tens of days.

Sorption behavior of uranium (VI) during crystallization of amorphous iron (A.Fe) minerals to crystalline iron (C.Fe) minerals have been investigated. Two different sorption conditions are applied for the experiments. One is the condition in which uranium is sorbed on A.Fe minerals before the crystallization (dynamic condition). The other is the condition in which uranium is sorbed on the A.Fe minerals and C.Fe minerals of goethite (static condition). Associations of uranium with the iron minerals are examined by a selective extraction test using a 1 M CH3COOK solution at pH 7, 1 M CH3COONa solution at pH 5 (WIorgan's solution), and TAO solution (10.9 gl-' oxalic acidS16.1 g.Z-' ammonium oxalate).Under the static condition, the fraction of uranium desorbed by a 1 M CH3COOK solution at pH 7 from A.Fe minerals is lower than that from goethite. And all of uranium are desorbed by the TAO solution from both A.Fe minerals and goethite. Contrary, under the dynamic condition, fractional uranium is remained after the TAO solution extraction. The hactional uranium remained after the TAO solution extraction from the iron minerals increases with increase in the crystallinity of the iron minerals. The concentrations of uranium in the solutions are less than 1%. These show that during the crystallization of amorphous to crystalline iron minerals most of uranium associated with the amorphous iron minerals is not released into the solution, and some fractional uranium move to be fixed to crystalline iron minerals.