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Query: UMLS:C0231807 (exertional dyspnea)
 3,402 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The U.S. EPA has approved Alternate Reference Methodologies for sampling radionuclide aerosol particles from stacks and ducts of U.S. DOE facilities. The approach allows use of single point sampling with shrouded probes from locations where both fluid momentum and contaminant concentration are well mixed across the flow cross section. For existing stacks and ducts that do not have locations where there is adequate mixing, we have developed a generic mixing system that will generate conditions suitable for single point sampling. The coefficients of variation of the velocity, tracer gas, and 10 microm aerodynamic diameter aerosol particles profiles are all less than 10%, which are well within the EPA limit of 20%. Mixing is affected neither by size of the system nor by flow rate, provided the flow is turbulent.
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PMID:A generic mixing system for achieving conditions suitable for single point representative effluent air sampling. 988 43

Environmental releases of tritium oxide at a number of Department of Energy nuclear weapons facilities contribute to a significant portion of environmental dose. Several conversion factors are utilized in the estimation of human impact from these releases, e.g., dispersion coefficients, consumption rates, uptake factors, transport factors, dose conversion factors, and risk coefficients. A probabilistic determination of the tritium dose conversion factor was generated in this work to assess the uncertainty of the internal dosimetry required to estimate dose equivalent given an intake of tritium oxide. The tritium dose conversion factor was found to vary by a factor of about 15 with a median value of 2.2 x 10(-11) Sv Bq(-1) when considering orthovoltage x rays as the standard for estimating the relative biological effectiveness of tritium. The median dose conversion factor increases by about 50%; however, when gamma radiation is considered as the standard. The current deterministic estimate of the tritium dose conversion factor published by the DOE and the EPA is 1.7 x 10(-11) Sv Bq(-1), 25-50% lower than the median probabilistic values. The tritium oxide dose conversion factor model was found to be most sensitive to biological half-life and quality factor and is highly dependent on the standardizing radiation for RBE assessments.
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PMID:Uncertainty of the tritium dose conversion factor. 1045

An integrated soil remediation technology called Lasagna has been developed that combines electrokinetics with treatment zones for use in low permeability soils where the rates of hydraulic and electrokinetic transport are too low to be useful for remediation of contaminants. The technology was developed by two groups, one involving industrial partners and the DOE and another involving US EPA and the University of Cincinnati, who pursued different electrode geometries. The Industry/DOE group has demonstrated the technology using electrodes and treatment zones installed vertically from the soil surface. We have demonstrated the feasibility of installing horizontal electrodes and treatment zones in subsurface soils by hydraulic fracturing, a process that we adapted from petroleum industry practices. When horizontal electrodes were connected to a dc power supply, uniform electrical potential gradients of 10-40 V/m were created in soil between the electrodes, inducing electroosmotic flow that facilitated movement of water and contaminants into treatment zones between the electrodes.
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PMID:Feasibility of electrokinetic soil remediation in horizontal Lasagna cells. 1094 26

This exploratory study compares two approaches for involving nonexpert stakeholders in difficult policy choices. Both approaches have as their goal informing members of the public about contaminated sites and involving them in decisions regarding their cleanup. The first approach focuses on technical information and seeks to improve the available knowledge base so that participants can make choices informed by detailed scientific data. This approach is similar in intent to many of the science-based initiatives in public involvement now being undertaken by EPA, DOE, and other federal or state agencies. The second approach, in contrast, focuses on values-oriented information and seeks to improve stakeholders' ability to make difficult choices in light of required tradeoffs across a variety of technical and nontechnical concerns. The results demonstrate that although both approaches help to increase participants' knowledge level, a values-based approach is more successful in terms of helping nonexpert participants to make decisions aboutwhat have historically been viewed as primarily technical problems.
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PMID:Testing alternative decision approaches for identifying cleanup priorities at contaminated sites. 1273 26

The Yucca Mountain high-level radioactive waste repository is designed to contain spent nuclear fuel and vitrified fission products. Due to the fact that it will be the first such facility constructed anywhere in the world, it has proved to be one in which multiple organizations, most prominently the U.S. Congress, are exercising a role. In addition to selecting a site for the facility, Congress specified that the U.S. Environmental Protection Agency (U.S. EPA) promulgate the associated Standards, the U.S. Nuclear Regulatory Commission establish applicable Regulations to implement the Standards, and the U.S. Department of Energy (U.S. DOE) design, construct, and operate the repository. Congress also specified that U.S. EPA request that the National Academy of Sciences (NAS) provide them guidance on the form and nature of the Standards. In so doing, Congress also stipulated that the Standards be expressed in terms of an "equivalent dose rate." As will be noted, this subsequently introduced serious complications. Due to the inputs of so many groups, and the fact that the NAS recommendations conflicted with the Congressional stipulation that the limits be expressed in terms of a dose rate, the outcome is a set of Standards that not only does not comply with the NAS recommendations, but also is neither integrated, nor consistent. The initial goals of this paper are to provide an independent risk/dose analysis for each of the eight radionuclides that are to be regulated, and to evaluate them in terms of the Standards. These efforts reveal that the Standards are neither workable nor capable of being implemented. The concluding portions of the paper provide guidance that, if successfully implemented, would enable U.S. DOE to complete the construction of the repository and operate it in accordance with the recommendations of NAS while, at the same time, provide a better, more accurate, understanding of its potential risks to the public. This facility is too important to the U.S. nuclear energy program to be impeded by inappropriate Standards and unnecessary regulatory restrictions. As will be noted, the sources of essentially all of the recommendations suggested in this paper were derived through applications of the principles of good science, and the benefits of "thinking outside the box."
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PMID:Lauriston S. Taylor Lecture: Yucca mountain radiation standards, dose/risk assessments, thinking outside the box, evaluations, and recommendations. 2038 5

Computer software packages approved by the U.S. Environmental Protection Agency (U.S. EPA), including CAP88-PC, are used by U.S. Department of Energy (U.S. DOE) sites to demonstrate compliance with the radionuclide air emission standard under the Clean Air Act. CAP88-PC version 3, was approved by the U.S. EPA in February 2006 for use by U.S. DOE facilities. Version 3 incorporates several major changes that have the potential to affect calculated doses relative to calculations using earlier versions. This analysis examined the types and magnitudes of changes to dose estimates for specific radionuclides calculated using the version 3 software compared with the previous versions. For parent radionuclides and for the total dose from radionuclide chains, total effective dose calculated with version 3 was compared to effective dose equivalent calculated with previous versions. Various comparisons were also performed to determine which of the updates in version 3 accounted for changes in overall dose estimates. CAP88-PC version 3 would produce substantially different results relative to previous versions of the code for a number of radionuclides, including some isotopes that may be present at U.S. DOE facilities, as well as those used for industrial and medical applications. In general, doses for many radionuclides were lower using version 3 but doses for a few key radionuclides increased relative to the previous versions.
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PMID:A comparison of dose results from the Clean Air Act Assessment Package-1988, personal computer (CAP88-PC), version 3 to previous versions. 2380 66

Arsenic (As) leaching from coal fly ash stockpiled at waste disposal sites is a source of environmental concern. An array of techniques including batch extraction and column leaching tests, in combination with speciation analysis of chemically specific As species, was employed to evaluate the mobility of As in fly ashes collected from the U.S. DOE Savannah River Site. The results obtained using the U.S. EPA Toxicity Characteristic Leaching Procedure (TCLP), a two-step sequential extraction technique, and continuous column leaching experiments suggest that only a small portion of total As in the fly ashes was mobile, but mobilizable As could be a considerable fraction (3.1-43%), varying inversely with alkalinity of fly ash. Speciation analysis by using phosphate extraction suggests that arsenate (As(V)) was the major extractable species in the fly ash samples. During the column leaching experiment, however, it was observed that arsenite (As(III)) was an important species leached out of the fly ashes, indicating species conversion during the leaching process. The matrix-bound As(V) within the fly ash, once being released from the solid matrix, could be converted to As(III) during its transport inside the column. The pHs of leachates and fly ashes (both acidic in column leaching experiments here) could be related to the dominance of As(III) in the effluents.
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PMID:Mobility and speciation of arsenic in the coal fly ashes collected from the Savannah River Site (SRS). 2693 5