[en] Work designed to assess the potential of using a single material to sorb highly charged metal ions from aqueous solution and then microencapsulate and chemical fix those sorbed metal ions in vitreous silica is described. The basis for these studies is a chemically functionalized porous silica that is termed Diphosil. Diphosil was created by Chiarizia and coworkers (Solv. Extr. Ion Exch. 1996, 14(6), 1977-1100) as an ion exchange resin that strongly sorbs actinide and other highly charged metal ions from acid solutions. We have determined the maximum metal ion loading for Diphosil and shown that it sorbs trivalent ions from concentrated phosphoric acid. Using FT-IR analysis, we have shown that heating metal ion-loaded Diphosil in air converts its organic content primarily into carbon dioxide and water vapor. We have carried out studies on luminescence dynamics and spectroscopy, powder x-ray diffraction, and optical microscopy of metal ion-loaded Diphosil prior to and following heating in air. All of the results of our investigations are consistent with microencapsulation and chemical fixation of metal ions sorbed into Diphosil when that material is heated to 1273 K. In consequence, Diphosil is a promising basis for a single material approach to reducing nuclear waste volume by removing longlived alpha emitters from high level liquid radioactive waste and generating a vitreous silica nuclear waste form for the removed radionuclides that is suitable for geologic disposal.

[en] A novel photochemical method of removing reactive fluorides from UF₆ gas has been discovered. This method reduces generated waste to little more than the volume of the removed impurities, minimizes loss of UF₆, and can produce a recyclable by-product, fluorine gas. In our new method, impure UF₆, is exposed to ultraviolet light which dissociates the UF₆ to UF₅ and fluorine atom. Impurities which chemically react with UF₅ are reduced and form solid compounds easily removed from the gas while UF₅ is converted back to UF₆. Proof-of-concept testing involved UF₆ containing NpF₆ and PuF₆ with CO added as a fluorine atom scavenger. In a single photolysis step, greater than 5000-fold reduction of PuF₆ was demonstrated while reducing NpF₆ by more than 40-fold. This process is likely to remove corrosion and fission product fluorides that are more reactive than UF₆ and has been demonstrated without an added fluorine atom scavenger by periodically removing photogenerated fluorine gas. 44 refs., 3 figs., 2 tabs

[en] This paper describes control of gyrotron microwave energy output by modulation of gyrotron anode voltage. At present, Electron Cyclotron Resonant Heating (ECRH) uses five gyrotrons on the Tandem Mirror Experiment-Upgrade (TMX-U) for plasma heating. One is in the 10 kG region of each end plug, one at the 5 kG region of each end plug, and one is used for central-cell heating. Also described are the design and operation of the anode modulation system. The operating advantages of gyrotron anode modulation include power balance, independent control of each gyrotron, an ability to modulate microwave output power up to 50 kHz, and gyrotron tuning. The performance results of anode modulation will be discussed. 9 figs

[en] The interaction between 5f electron states of einsteinium 3+ ion and coordinated ligands in solution has been probed using laser-induced fluorescence. Aquo einsteinium 3+ ion was observed to fluoresce from its first excited J = 5 state in a broad-band peaking at 9260 wavenumbers. The observed fluorescence lifetimes were 1.05 microseconds and 2.78 microseconds in H²O and D²O (99+ % D atom), respectively. The non-radiative decay rates derived from the lifetime data are compared with previously reported data for Cm, Sm, Eu, Tb, and Dy aquo 3+ ions. The 5f actinide states exhibit substantially greater non-radiative decay rates than do lanthanide 4f states of similar energy gap. This provides evidence that actinide 5f electrons interact more strongly with their inner coordination sphere than do lanthanide ion 4f electrons. The fluorescence lifetime of einsteinium 3+ ion complexed with 1 formal di(2-ethylhexyl)orthophosphoric acid in h-heptane was 2.34 microseconds. 3 figures, 1 table

[en] The gas complexation reactions between LnCl₃ and Al₂Cl₆ to yield molecular species of the form LnCl₃ (Al₂Cl₆)/sub x/ have been studied for a number of years. The spectrophotometric technique has been used to deduce the thermodynamic properties of the molecular species. We have studied the HoCl₃ (Al₂Cl₆)/sub x/ system from 600 to 900⁰K and at Al₂Cl₆ pressures between 1 and 7 atm. The Ho³⁺ hypersensitive transition between ⁵I₈ and ⁵G₆ at 456 nm has been used to measure the complex vapor densities as a function of pressure and temperature. A temperature-dependence of the optical absorption spectrum was observed in samples with a constant Ho³⁺ ion density. These data cannot be understood in terms of the generally used treatment of molar absorptivity, but requires the introduction of an effective oscillator strength. A temperature-dependent oscillator effect is also observed and this is interpeted as evidence for the presence of multiple species with differing oscillator strengths. The consequence of these observations for the determination of equilibrium constants for the different species will be discussed

[en] This paper reports the first determination of the enthalpy of formation of a complex actinide(IV) oxide: ΔH⁰/sub f/ (BaUO₃, s, 298 K) = -1690 +- 10 kJ mol^-1. The preparation and properties of this and other actinide(IV) complex oxides are described and are compared with other perovskites BaMO₃. The relative stabilities of tetravalent and hexavalent uranium in various environments are compared in terms of the oxidation-reduction behavior of uranium in geological nuclear waste storage media; in perovskite, uranium(IV) is very unstable in comparison with uranium(VI)

[en] This invention relates in a general way to positron emission tacography (computer controlled axial tomography), and more exactly, to a data acquisition system enabling the number of background noise signals due to random coincidences to be very accurately determined. The extraction of this background noise from the total number of coincidences is assured by this invention. This operation is either carried out practically instantaneously or later on. The input circuits used enable the equipment to function with an almost zero dead time

[en] In the present invention a positron emission tomographic system is provided in which the random photon coincidence background is determined for the lines of sight along which the positron annihiliations are located. The circuitry is arranged so that this background may be subtracted almost simultaneously from the total photon coincidence measurement, or may be stored in a temporary memory for latter subtraction. In this system, an appropriate coincidence resolution time is selected and coincidences of photons detected at 180 degree opposed detectors within the time resolution are recorded as the overall coincidence count. This total count includes a source(true events) count plus a background(random coincidences) count. The background count is determined by measuring photons detected at these same sets of photon detectors and employing the same coincidence resolution period, where the signals from one set of detectors are passed through a delay longer in time than this resolution period

[en] The Eu-encrypted Preyssler anion, [EuP₅W₃₀O₁₁₀]^n-, demonstrates unusual electronic properties as a function of applied potenial. The Preyssler anion itself, when exchanged with a nonredox active trivalent ion such as La³⁺, is electroactive in acidic solution, reversibly accepting up to 10 electrons under reducing conditions. Encrypted Eu, which is trivalent at rest potential, is reduced concomitantly with the framework. The details of this reduction are probed with Eu L₃-XANES, coulometry, and magnetic susceptibility. The results are interpreted in terms of a bonding interaction between the Eu f-states and the W-O framework band, facilitated by the crossing of the framework Fermi level with the localized states. Such behavior has been previously observed in intermediate-valent and correlated-electron systems. The observation of such behavior in an isolated cluster opens the door for new avenues of research into correlated-electron behavior.

[en] The ECRH Control System was installed on the Tandem Mirror Experiment-Upgrade (TMX-U) in 1980. The system provides approximately 1 MW of 28 GHz microwave power to the TMX-U plasma. The subsystems of ECRH that must be controlled include high-voltage charging supplies, series pass tubes, and magnet supplies. In addition to the devices that must be controlled, many interlocks must be continuously monitored. The previous control system used relay logic and analog controls to operate the system. This approach has many drawbacks such as lack of system flexibility and maintainability. In order to address these problems, it was decided to go with a CAMAC and Modicon based system that uses a Hewlett-Packard 9836C personal computer to replace the previous analog controls. 2 figs