High Z discs have been irradiated with 1.06 ..mu.. laser light at intensities between 7 x 10/sup 13/ and 3 x 10/sup 15/ W/cm, and pulse lengths between 200 and 1000 ps. Due to the high Z, inverse bremsstrahlung becomes an important absorption effect and competes strongly with resonance absorption and stimulated scattering. We find that inhibited electron thermal conduction and non-LTE ionization physics are important. Their inclusion in the LASNEX modeling results in steepened temperature and density profiles near critical, thus producing a several keV underdense corona. These conditions bring what would otherwise be 100% inverse bremsstrahlung absorption down to the experimentally observed values (50% at 10/sup 14/ W/cm). The non-LTE physics is essential to correctly compute the level populations of the high Z atoms moving rapidly through a steep density gradient into the corona. This modeling also shows that x-rays are emitted in a thin overdense region, and on a time scale 50% longer than the laser pulse. Both of these effects are seen in the experiments.

The effects of D. C. electric fields on high lying Rydberg and valence states in atomic uranium have been studied. Results of measurements of Stark shifts, lifetime lengthening via l-mixing, critical fields for ionization, barrier tunneling, and the appearance of zero-field parity forbidden transitions are presented for atomic uranium along with the observation of field induced autoionization of valence states. 3 figs. (GHT)

Extraction, or reverse-phase partition chromatography, as used mostly for analytical separations, employs an organic solvent extractant as a stationary phase on an inert support material. This technique has the advantage of utilizing the versatility of solvent extraction systems with the less expensive operation of ion exchange equipment. Bayer AG Lewatit OC-1023, a tributyl phosphate impregnated sorbent developed for extraction chromatography, was evaluated for the separation of uranium and plutonium from mixed actinide residues at Rocky Flats. Uranium breakthrough capacity and eluion behavior were determined for the OC-1023. Uranium breakthrough capacity results show that the support has a high capacity for uranium from 10 g/l uranium and 25 g/l plutonium-2.5 g/l uranium feeds. The total uranium capacity of the support under these conditions was determined to range from about 53 to 65% of the theoretical TBP capacity. The uranium elution results show that the uranium can be eluted with a minimum of eluant.

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