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Abstract  

An analytical procedure for rapidly screening large numbers of oils for polychlorinated biphenyl (PCB) content has been developed and is now in routine use. Pontential levels of PCBs are inferred from chlorine concentrations as determined using the automated neutron activation analysis (NAA) facility at the Los Alamos National Laboratory Omega West Reactor. The technique is designed to screen up to 200 oil samples per eight hour working day, using a sample volume of approximately 1 milliliter. Because of the automated nature of the analysis, elements in addition to chlorine are determined, when present. These include fluorine, bromine, iodine and sulfur. U.S. National Bureau of Standards (NBS) and U. S. Environmental Protection Agency (EPA) Standard Reference Materials are routinely analyzed for quality assurance purposes. The results of our analyses of these materials for certified elements is discussed as well as results for other non-certified elements observed in the standard materials.

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Abstract  

The RAYGUN gamma-ray analysis code (a descendant of GAMANAL and GRPANL) has been converted from FORTRAN IV to RATFOR and ported to the IBM PC environment. The history of the code and some of the problems encountered during the conversion are discussed. The converted code was then used to analyze the IAEA G-1 Intercomparison Spectra as one measure of the codes performance. The results of the analyses showed that although the intrinsic peak finding and multiplet resolution capabilities of the code are a bit weak, the UPPER-LIMIT and LIBRARY-SEARCH options work quite well. When appropriate gamma-ray libraries are created, the overall performance of the code is quite satisfactory. The RAYGUN code runs on an IBM PC or clone with 256 Kbytes of RAM.

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Abstract  

Pacific Northwest National Laboratory, with guidance and support from the U.S. Department of Energy's NN-20 Comprehensive Test Ban Treaty (CTBT) Research and Development program, has developed and demonstrated a fully automatic sampler-analyzer (ARSA) for the collection and quantitative measurement of the four xenon radionuclides,131mXe (11.9 d),133mXe (2.19 d),133Xe (5.24 d), and135Xe (9.10 h), in the atmosphere. These radionuclides are important signatures in monitoring for compliance to a CTBT, and may have applications in stack monitoring and other areas where xenon radionuclides are present. The activity ratios between certain of these radionuclides permit discrimination between radioxenon originating from nuclear detonations and that from nuclear reactor operations, nuclear fuel reprocessing, or from medical isotope production and usage. With the ARSA system, xenon is continuously and automatically separated from the atmosphere at flow rates of about 100 lpm by sorption-bed techniques. Samples collected in 8 hours are automatically analyzed by electron-photon coincidence spectrometry to provide detection sensitivities as low as 100 μBq/m3 of air. This sensitivity is about 10-fold better than achieved with reported laboratory-based procedures1 for the short time collection intervals of interest. Gamma-ray energy spectra and gas analysis data are automatically collected.

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Abstract  

A large area beta scintillation detector has been developed which is currently capable of determining Sr-90/Y-90 contamination in surficial soils. The detector system employs scintillating fiber optic arrays, with active dimensions approximately 15 cm wide by 100 cm long, both ends of which are coupled to multiple photomultiplier tubes (PMTs). Electronic processing includes coincidence requirements to optimize sensitivity and selectivity for the 2.28 MeV (maximum) beta particle from Y-90. Low energy beta particles and gamma rays are discriminated against using double ended and multi-layer coincidence requirements. The detector system is personal-computer-software controlled and data restored in a format compatible with standard database software for ease of final data reduction. Experimental calibration studies have shown a linear response for Sr-90/Y-90 soil concentrations from 12 to over 500 pCi/g and a discrimination factor of 50 to 1 versus Cs-137.

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Abstract  

A novel scintillating-fiber sensor for detecting high-energy beta particles has been designed and built at the Pacific Northwest Laboratory to characterize238U and90Sr in surface soils. High-energy betas generate unique signals as they pass through multiple layers of scintillating fibers that make up the active region of the detector. Lower-energy beta particles, gamma rays, and cosmic-ray-generated particles comprise the majority of the background interferences. The resulting signals produced by these latter phenomena are effectively discriminated against due to the combination of the sensor's multi-layer configuration and its interlayer coincidence/anti-coincidence circuitry.

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Abstract  

The Pacific Northwest National Laboratory has developed an Automated Radioxenon Sampler/Analyzer (ARSA) in support of the Comprehensive Nuclear-Test-Ban-Treaty (CTBT) to measure four radioxenon isotopes: 131mXe, 133mXe, 133gXe, and 135gXe. This system uses a beta-gamma coincidence counting detector to produce two-dimensional plots of gamma-energy versus beta-energy. Betas and conversion electrons (CE) are detected in a cylindrical plastic scintillation cell and gamma and X-rays are detected in a surrounding NaI(Tl) scintillation detector. The ARSA has been field tested at several locations to measure the radioxenon concentrations. Most recently it has been deployed at the Institut für Atmosphärische Radioaktivität in Freiburg, Germany. During the first 4 months of 2000 the measured 133Xe oncentrations have varied between 0.0±0.1 and 110±10 mBq/m3 air. The longer lived 131mXe (T 1/2 = 11.9 d) and short lived 135Xe (T 1/2 = 9.1 h) have also been detected in small quantities, while 133mXe concentrations have been consistent with zero. Minimum detectable concentration (MDC) calculations for 133gXe fell well below the 1 mBq per standard-cubic-meter of air requirement adopted by the CTBT Preparatory Commission.1 A description of the radioxenon detector, the concentration and MDC calculations and preliminary results of the field test in Germany are presented.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: T. Bowyer, K. Abel, C. Hubbard, A. McKinnon, M. Panisko, R. Perkins, P. Reeder, R. Thompson, and R. Warner

Abstract  

A fully automatic radioxenon sampler/analyzer (ARSA) has been developed and demonstrated for the collection and quantitative measurement of the four xenon radionuclides,131mXe(11.9 d),133mXe(2.2 d),133Xe(5.2 d), and135Xe(9.1 hr), in the atmosphere. These radionuclides are important signatures in monitoring for compliance to a Comprehensive Test Ban Treaty (CTBT). Activity ratios of these radionuclides permit source attribution. Xenon, continuously and automatically separated from the atmosphere, is automatically analyzed by electron-photon coincidence spectrometry providing a lower limit of detection of about 100 μBq/m3. The demonstrated detection limit is about 100 times better than achievable with reported laboratory-based procedures for the short-time collection intervals of interest.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: D. Robertson, A. Schilk, K. Abel, E. Lepel, C. Thomas, S. Pratt, E. Cooper, P. Hartwig, and R. Killey

Abstract  

In order to more accurately predict the rates and mechanisms of radionuclide migration from lowlevel waste disposal facilities via groundwater transport, ongoing studies are being conducted at field sites at Chalk River Laboratories to identify and characterize the chemical speciation of mobile, long-lived radionuclides migrating in groundwaters. Large-volume water sampling techniques are being utilized to separate and concentrate radionuclides into particulate, cationic, anionic, and nonionic chemical forms. Most radionuclides are migrating as soluble, anionic species which appear to be predominately organoradionuclide complexes. Laboratory studies utilizing anion exchange chromatography have separated several anionically complexed radionuclides, e.g.,60Co and106Ru, into a number of specific compounds or groups of compounds. Large-volume ultra-filtration experiments have shown that significant fractions of the radionuclides are being transported in these groundwaters in the form of macromolecules having molecular weights ranging from less than 3,000 to 100,000.

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