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PubMed2005

The on-line characterization of a radium slurry by gamma-ray spectrometry.

We have developed an in-line monitor to directly measure the (226)Ra concentration in a nuclear waste stream using quantitative gamma-ray spectrometry applied to the 186keV emission. The waste stream is in the form of a slurry composed of the solid waste material mixed with water. The concentration measurement includes a self-attenuation correction factor determined from a transmission measurement using the 122keV gamma from (57)Co. Presented here is the model for the measurement system and results from some initial tests.

Industrial Waste↗
PubMed1986

Radionuclide uptake by trees at a radwaste pond in Washington State.

This paper presents work conducted in the summer of 1980 by Rockwell Hanford Operations, Hanford, WA, in support of a proposed effort to decommission and decontaminate a Hanford radwaste pond (216-U-10 Pond). The radionuclide values presented here are in addition to the U-Pond work that was recently published (La83) and are below any levels of environmental concern and within state and federal guidelines. U-Pond was constructed in 1944 for the surface disposal of industrial waste waters from nuclear separation processes and is one of the longest used aquatic, low-level, radioactive waste-disposal sites in the world. Tree leaf/twig, root, core and soil samples were collected and analyzed for 137Cs, 90Sr and 239Pu/240Pu. Strontium-90 was more readily taken up by trees than 137Cs or 239Pu/240Pu. Soil concentration values for 137Cs and 239Pu/240Pu were significantly greater (p less than or equal to 0.05) than all tree component parts. Radionuclide concentration ratios were higher for 90Sr (0.01-1355.0) than for 137Cs and 239Pu/240Pu for all tree components examined. Concentration ratios for 239Pu/240Pu ranged from 10(-6) to 10(-2) and are comparable to other studies conducted at the U.S. Department of Energy's Oak Ridge and Savannah River laboratories. These data represent the first quantitative information with respect to radionuclide uptake by trees on the Hanford Site.

Cesium Radioisotopes↗
PubMedDate not supplied

Upscaling of hydraulic conductivity and telescopic mesh refinement.

Performance assessments of repositories for the underground disposal of nuclear fuel and waste include models of ground water flow and transport in the host rocks. Estimates of hydraulic conductivity, K, based on field measurements may require adjustment (upscaling) for use in numerical models, but the choice of upscaling approach can be complicated by the use of nested modeling, large-scale fracture zones, and a high degree of heterogeneity. Four approaches to upscaling K are examined using a reference case based on exhaustive site data and an application of nested modeling to evaluate performance assessment of a waste repository. The upscaling approaches are evaluated for their effects on the flow balance between nested modeling domains and on simple measures of repository performance. Of the upscaling approaches examined in this study, the greatest consistency of boundary flows was achieved using the observed scale dependence for the rock domains, measured values from the large-scale interference test for the conductor domain, and a semivariogram regularization based on the Moye model for packer test interpretation. Making the assumption that large fracture zones are two-dimensional media results in the greatest changes to the median of travel time and improves the flow balance between the nested models. The uncertainty of upscaling methods apparently has a small impact on median performance measures, but a significant impact on the variances and earliest arrival times.

Models, Theoretical↗