Authors:O. B. Egorov, M. J. O’Hara, and J. W. Grate
A fully automated analysis procedure and instrument for the measurement of total 99Tc in aged nuclear waste has been developed. The overall analysis approach is based on a fully automated wet radiochemical analysis method. Microwave-assisted sample oxidation is used prior to a chemical separation step in order to oxidize all of the non-pertechnetate species to pertechnetate. Separation of the pertechnetate from interfering radioactive and stable matrix species is carried out using an anion-exchange column. The separated 99Tc is quantified using a flow-through solid cell scintillation detector. The instrument is capable of an analysis time of <13 minute per sample with a detection limit of 2000 dpm/ml. Nuclear waste samples from the Hanford site with a high content of non-pertechnetate species were successfully analyzed using this method.
Authors:R. S. Addleman, M. J. O’Hara, J. W. Grate, and O. B. Egorov
Direct alpha-energy spectroscopy in liquids is possible by placing a chemically selective polymer thin film upon the surface of passivated silicon diodes. By utilizing polymer thin films with high affinity for actinides, we have been able to selectively concentrate actinides of interest upon the diode surface, resulting in a substantial increase in sensitivity relative to a direct measurement. With this film coated diodes, we were able to obtain in-situ alpha spectra with energy resolution comparable to that of conventional alpha-spectroscopy. The response of the thin film coated diode was found to be linear over 104. The sensitivity and reversibility is a function of the membrane complexation chemistry.
Authors:R. S. Addleman, M. J. O’Hara, T. Marks, J. W. Grate, and O. B. Egorov
The determination of transuranic (TRU) content in nuclear wastes, reactor materials, process solutions, and various other matrices is required in support of material assessment, environmental restoration, and waste processing activities. We have found that direct measurement of TRU is possible using surface passivated ion implanted planar silicon diode detectors. The performance and durability of modern silicon diodes enables direct detection of alpha-particles, with retention of some spectral information, through small air gaps or under direct contact with liquid or solid samples. We will present results on the performance of silicon diode detectors for the determination of TRU in liquids.
Authors:R. S. Addleman, O. B. Egorov, M. J. O'Hara, B. Busche, T. S. Zemanian, and G. Fryxell
An analytical system is suggested to separate a number of elements of the Periodic Table in a hydrogen or oxygen stream at temperatures up to 1400 °C. High temperature chemical filters are used to separate volatile products. The approach has demonstrated its efficiency in a number of examples of carrier-free isotope production from targets irradiated at an accelerator: 109Cd from In; 22Na from Al; 72Se from GaAs; 188Pt, 183Re, 185Os and 201Tl from Pb or Bi; separation of Po from Pb and Bi, etc. Another application of high temperature chemical sublimation of elements and oxides was realized in activation analysis of noble metals in various ores and samples.