Evaluation of cobalt mobility in soils from the Nevada Test Site

Nuclear testing at and around the Nevada Test Site (NTS) resulted in widespread contamination from transuranic and other radionuclides, as well as from other toxic inorganic and organic contaminants. The type of contamination, including spatial distribution and type of radionuclides present, depends on the type of testing performed. Remediation of the contaminated areas is currently under way. The optimum in situ or ex situ remediation technology depends on the degree of interaction between the particular radionuclide, or contaminant in general, and the soil matrix, among other factors. The objective of this project was to evaluate the sorption affinity of NTS soils for common non-transuranic radionuclides. The sorption of cobalt (Co) on soils from two different areas of the NTS, namely the Little Feller and Cabriolet event sites, was studied. Experiments were conducted as a function of pH, solid concentration, total Co concentration, ionic strength, and particle size fraction. Preliminary results indicate that both soils have a high sorption capacity for Co. The results suggest that Co uptake is controlled by sorption on either internal, permanent-charge, ion-exchange sites of clay minerals or on amphoteric, surface-hydroxyl sites of oxides. The results further indicate strong retardation of Co in these soils, under most conditions tested and expected to be found in the respective soil environments. These conclusions are applicable to transport of radionuclides which are expected to bind strongly on oxide surfaces (e.g., Co) but the results may not be representative of the behavior of weakly binding radionuclides. These studies clearly demonstrate the importance of evaluating the mobility of radionuclides and the degree of radionuclide-soil interaction before final selection of an in situ or ex situ remediation technology for a contaminated site

Effect of phosphorus on the attenuation of lead and chromium

This study analyses the adsorption of Pb(II) and Cr(III) in soils. These metals are commonly found together in nature in urban wastes or industrial spillages, and the theoretical approach of the work was to evaluate the response of the soil to continuous Cr and Pb spillages to soil in terms of several physicochemical parameters. The influence of an anthropogenic input of phosphorus was evaluated. Continuous flow experiments were run in duplicates in acrylic columns (25 cm × 3.2 cm). The influent Cr(III) and Pb(II) solutions of 10 mg l−1 and 25 mg l−1 at pH 5 were pumped upward through the bottom of the columns to ensure saturation flow conditions. Also, successive experiments were run with the above concentrations of Cr(III) and Pb(II) and NaH2PO4, keeping metal to phosphorus ratio of 1:0, 1:0.1 and 1:1. Modelling parameters included Freundlich and Langmuir equations, together with the Two-site adsorption model using CXTFIT code. Results obtained allowed concluding that Pb(II) adsorption presents a certain degree of irreversibility and the continued spillages over soil increment the fraction which is not easily desorbed. Cr(III) desorption was almost complete, evidencing its high mobility in nature. The presence of an anthropogenic input of phosphorus leads to a marked increase of both Pb(II) and Cr(III) adsorption in soils. Z-potential measurements allow to discard the electrostatic attraction of Cr(III) and Pb(II) with the surface charged soil as the dominant process of metal sorption. Instead, CheaqsPro simulation allows to identify PbH2PO4 +, PbHPO4 (aq) and CrHPO4 + as the dominant species which regulate Cr(III) and Pb(II) transport in soils.Fundação para a Ciência e a Tecnologi

Evaluation of technologies for volume reduction of plutonium-contaminated soils from the Nevada Test Site

Nuclear testing at and around the Nevada Test Site (NTS) resulted in plutonium (Pu) contamination of the soil over an area of several thousands of acres. The objective of this project was to evaluate the potential of five different processes to reduce the volume of Pu-contaminated soil from three different areas, namely Areas 11, 13, and 52. Volume reduction was to be accomplished by concentrating the Pu into a small but highly contaminated soil fraction, thereby greatly reducing the volume of soil requiring disposal. The processes tested were proposed by Paramag Corp. (PARAMAG), Advanced Processing Technologies Inc. (APT), Lockheed Environmental Systems and Technologies (LESAT), Nuclear Remediation Technologies (NRT), and Scientific Ecology Group (SEG). Because of time and budgetary restraints, the NRT and SEG processes were tested with soil from Area 11 only. These processes typically included a preliminary soil conditioning step (e.g., attrition scrubbing, wet sieving), followed by a more advanced process designed to separate Pu from the soil, based on physiochemical properties of Pu compounds (e.g., magnetic susceptibility, specific gravity). Analysis of the soil indicates that a substantial fraction of the total Pu contamination is typically confined in a relatively narrow and small particle size range. Processes which were able to separate this highly contaminated soil fraction (using physical methods, e.g., attrition scrubbing, wet sieving), from the rest of the soil achieved volume (mass) reductions on the order of 70%. The advanced, more complex processes tested did not enhance volume reduction. The primary reason why processes that rely on the dependence of settling velocity on density differences failed was the very fine grain size of the Pu-rich particles

Simulation-Based Environment for the Eye-Tracking Control of Tele-Operated Mobile Robots

Eye tracking has traditionally been used to measure the visual attention of users while performing a task or to aide disabled persons in performing hands-free interactions. The increased accuracy and reduced cost of eye-tracking equipment today makes it feasible to utilize this technology for explicit control tasks, especially in cases where there is confluence between the visual task and control. This paper describes the design of a virtual simulation environment in order to assess the feasibility of using eye-tracking to control the movement and payload of a ground robot during a visual search task. The resulting simulation-based test environment includes a kinematic model of a ground tele-operated robot within a virtual debris-filled, industrial environment with intact and damaged barrels. The operator can steer the robot while independently operating an onboard pan-tilt (PT) camera used to search for damaged containers. The environment supports three methods of control: manual, in which the operator utilizes two joysticks, one for speed/steering and one for camera control, hybrid in which the operator utilizes a joystick for speed/steering control and eye-tracking for camera control, and hands-free in which the operator utilizes gaze for both steering/speed control and camera operation

Evaluation of groundwater flow and transport at the Shoal underground nuclear test: An interim report

Since 1962, all United States nuclear tests have been conducted underground. A consequence of this testing has been the deposition of large amounts of radioactive materials in the subsurface, sometimes in direct contact with groundwater. The majority of this testing occurred on the Nevada Test Site, but a limited number of experiments were conducted in other locations. One of these is the subject of this report, the Project Shoal Area (PSA), located about 50 km southeast of Fallon, Nevada. The Shoal test consisted of a 12-kiloton-yield nuclear detonation which occurred on October 26, 1963. Project Shoal was part of studies to enhance seismic detection of underground nuclear tests, in particular, in active earthquake areas. Characterization of groundwater contamination at the Project Shoal Area is being conducted by the US Department of Energy (DOE) under the Federal Facility Agreement and Consent Order (FFACO) with the State of Nevada Department of Environmental Protection and the US Department of Defense (DOD). This order prescribes a Corrective Action Strategy (Appendix VI), which, as applied to underground nuclear tests, involves preparing a Corrective Action Investigation Plan (CAIP), Corrective Action Decision Document (CADD), Corrective Action Plan, and Closure Report. The scope of the CAIP is flow and transport modeling to establish contaminant boundaries that are protective of human health and the environment. This interim report describes the current status of the flow and transport modeling for the PSA

Design of Simulator Scenarios to Study Effectiveness of Electronic Stability Control Systems

The mission of the National Advanced Driving Simulator is to conduct highway safety research that will reduce annual loss of life on U.S. roadways. The simulator is well suited in its ability to replicate vehicle dynamics - and associated motion and visual cues - realistically to conduct complex experiments. It is unique in its ability to study vehicle control and loss-of-control situations in a safe and controlled environment. These capabilities make it an appropriate device to study the effectiveness of electronic stability control (ESC) systems, in which proper handling during loss of vehicle control is critical to assess system efficacy. The focus of the study is on challenges associated with creating repeatable yet unexpected scenario events in which loss of control is imminent for most drivers. Scenario events designed for a large-scale experiment to study ESC systems are detailed, data derived from these scenarios are discussed, and findings of scenario effectiveness are presented. A discussion of what constitutes loss of control and how to measure its effect effectively is provided

Measurement of specific fracture energy and surface tension of brittle materials in powder form

V článku uvedeno Libor M. Hlaváč.This article presents a method for the experimental measurement of specific fracture energy and surface tension of a brittle materials in a powder form. This work is focused on testing a method on the mineral, almandine. A hydraulic press was used in the experiment to crush powder particles, and statistical evaluation was used to analyze the change in the powder surface. The powder was subject to various conditions during crushing. The crushing was performed both in air and in water. It was done at three different compression speeds, namely 15.8 MPa/s, 3.95 MPa/s and 2.25 MPa/s. The experimental results showed measurable differences in the specific fracture energy values in the presented regimes