John C. Evans

Detection of organomercury, selenium and arsenic compounds by a capillary column gas chromatography-microwave plasma detector system

Abstract Low-pressure and atmospheric-pressure microwave-induced helium plasma detectors were interfaced with a capillary column gas chromatograph. A number of dialkyl mercury, diaryl mercury and monoalkyl mercury chlorides have been separated on both systems. The capillary column is well suited for the separation of organomercury compounds, but the selection of the appropriate scavenge gas is critical to achieve good peak shapes for these mercury compounds. The atmospheric pressure system exhibited better sensitivity and selectivity for organomercury compounds than the low-pressure system. In addition to the organomercury compounds, satisfactory separation has been achieved for trimethyl, triethyl and triphenylarsine on the gas chromatograph lowpressure microwave plasma detector system. Preliminary work using the atmospheric-pressure system for arsenic and selenium line selection is also presented.

A low-pressure Beenakker-type microwave-induced helium plasma source as a simultaneous multi-element gas chromatographic detector

Abstract A low-pressure version of a Beenakker-type microwave-induced helium plasma optical emission spectroscopy detector for gas chromatographic effluents is described. The plasma is sustained in a 1.3-rum i.d. quartz tube and is viewed axially through a quartz window. Operating characteristics of the source were studied for power levels of 15–115 W, for carrier-gas flows of 20–1000 mi min−1, and for pressures of 2–700 torr. A gas chromatographic system involving a fused-silica capillary column is used as the sample introduction system for compounds containing carbon, hydrogen, nitrogen, sulfur, and chlorine. Elemental response factors and the precision of elemental response ratios were studied. The use of this detector in evaluating empirical formulae is also discussed. Empirical formulae for a number of hydrocarbons and sulfur-containing aliphatic and heterocyclic compounds are presented, together with a discussion of the factors that affect accuracy and precision. It is concluded that this type of detector combines some of the best fearutes of the atmospheric-pressure Beenakker and the Evenson-type sources.

Detection of thiophenes in the offgas condensate of an oil shale retort by a GC-microwave induced helium plasma detector

SummaryA series of alkylthiophenes and dimethyl disulfide were tentatively identified in an oil shale retort gas condensate from a 6-kg bench-scale retort using gas chromatography with a microwave-induced helium plasma detector (GC-MIP). The sulfur species were present in concentrations ranging from 1.5 to 10.7 mol ppm in the undiluted offgas. The GC-MIP technique was successful in selectively detecting the sulfur components in the complex mixture. Quantitation was simplified relative to GC with flame-photometric detection because of the absence of quenching or other interference problems at the concentrations studied. Attempts to determine stoichiometry of the sulfur components by comparison of carbon, hydrogen, and sulfur ratios with those of standards were unsuccessful because of the complexity of the carbon and hydrogen chromatograms.

Evaluation of Elevated Tritium Levels in Groundwater Downgradient from the 618-11 Burial Ground Phase I Investigations

This report describes the results of the preliminary investigation of elevated tritium in groundwater discovered near the 618-11 burial ground, located in the eastern part of the Hanford Site.

The 76Ge double beta decay experiment at Homestake

An ultralow background intrinsic Ge detector has been developed over several generations of experiments. The radioactive background from construction materials has been reduced by more than two orders of magnitude. The sources of background in a standard commercial cryostat have been identified and eliminated. Data taken with this 135 cm3 prototype installed in the Homestake Gold Mine are presented. A large (1440 cm3) detector and data acquisition system now under construction are also described.

Summary of Hanford Subsurface Air Flow and Extraction (SAFE) Activities for Fiscal Year 2001

Potential leak detection, monitoring, and mitigation techniques are being developed to support Hanford single-shell tank waste retrieval operations. In July and August 2001, Pacific Northwest National Laboratory demonstrated several of these technologies for CH2M HILL Hanford Group, Inc., at the Mock Tank Site in the 200 East Area. These subsurface air flow and extraction (SAFE) technologies use air injection and extraction wells to create an advective air flowfield beneath a tank. SAFE includes the following technologies: 1) leak detection--in-tank tracers, flowfield disturbance, radon displacement, and tank waste vapors; 2) leak monitoring--partitioning tracer method and reactive tracers; 3) leak mitigation--soil desiccation before and after leakage and in situ gaseous reduction; and 4) subsurface characterization--interfacial tracers. This report provides an overview of these technologies and discusses the FY 2001 demonstration activities at the Mock Tank Site, their results, and implications for future work.

Double Beta Decay: Recent Developments and Projections

A report of recent events in both theoretical and experimental aspects of double beta decay is given. General theoretical considerations, recent developments in nuclear structure theory, geochronological determinations of half lives and ratios as well as laboratory experiments are discussed with emphasis on the past three years. Some projections are given.

Data Quality Issues Associated with the Presence of Chlorinated Hydrocarbons in Tank Vapor Samples

Characterization data for the gases and vapors in the Hanford Site high-level radioactive waste tank headspaces are compiled and available via the TWINS interface (TWINS 2006). A recent re-examination of selected data from TWINS has shown a number of anomalies with respect to compounds that are (1) not expected to be present in the tank based on operational knowledge and (2) not found consistently in the same tank by alternative analysis methods or repeat sampling. Numerous results for two chemicals in particular, cis- and trans-1,2-dichloropropane, are determined here to be suspect based on evidence that they were laboratory contaminants.

Representative Sampling of High-Level Radioactive Waste Tank Headspaces

Headspaces of the underground high-level radioactive waste-storage tanks at the U.S. Department of Energys Hanford Site have been sampled to resolve tank safety and industrial hygiene issues and to estimate regulated air pollutant emissions. Because sampling these tanks is difficult and expensive, samples have been collected from a single location of the headspaces, based on the supposition that this would provide representative samples. In most tanks, mixing of vapors occurs because of thermally driven convection from heat generated by radioactive decay of the waste. However, in some low-temperature tanks, the ground temperature above the tank may be warmer than the waste, minimizing thermally induced convection, and raising the concern that samples from a single location may not be representative. To resolve this issue, six samples at different vertical and horizontal locations were taken from each of three low-temperature tanks and analyzed for ammonia, water, permanent gases, total non-methane organic compound concentration, and selected organic vapors. Statistical analysis of the data indicated that the tanks did not exhibit significant horizontal or vertical concentration gradients.

Comparison of two soil gas methods used during a field investigation

Soil gas surveys were employed to help determine the nature and extent of contamination resulting from the past operation of source area ST58, the Old Quartermaster Service Station, at Eielson Air Force Base, Alaska. Two Intrusive methods were used for comparison, active conventional gas extraction and the passive Petrex method. Results were comparable, with gasoline identified as the main subsurface contaminant In both surveys. Close spatial correlation was also achieved among screening instruments and laboratory analyses. Contaminant concentrations corresponded very well with unsealed blueprints showing the locations of the above‐ground storage tanks and associated piping, subsequent test pit soil samples, and excavation results. The contamination probably occurred as a result of surface spills and leaks from discontinuities and/or breaks in the underground piping. A finer grid was employed in the Petrex method survey and produced better‐resolved contours. The use of conventional gas extraction provided...