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PubMed1997

Issues in establishing an aerosol radiological baseline for the waste isolation pilot plant near Carlsbad, New Mexico.

The Department of Energy has constructed a deep geologic repository for defense transuranic waste disposal. The Waste Isolation Pilot Plant, located in Southeastern New Mexico, is slated to receive transuranic waste by truck delivery beginning in 1998. The Environmental Evaluation Group (EEG) provides an independent evaluation of the impact on the health and environment in New Mexico of the WIPP project. Since 1985, the EEG has operated a network of air monitoring sites around WIPP and in nearby communities. The radionuclide concentration data from these air samples have been assembled into a useful baseline data base after resolution of a number of methodological and quality assurance issues. Investigation thresholds for the principal radionuclides have been calculated from combined data collected from several sites. These action levels will provide a critical quantitative basis for decisions of whether future airborne radionuclide measurements are attributable to accidental releases.

Air Pollutants, Radioactive↗
PubMedDate not supplied

Analysis of thermohydrologic behavior for above-boiling and below-boiling thermal-operating modes for a repository at Yucca Mountain.

We report results from a multi-scale thermohydrologic modeling study for two alternative thermal-operating modes for the potential repository system recently analyzed by the Yucca Mountain Project. These include a Higher-Temperature Operating Mode (HTOM), which results in a localized boiling zone around each emplacement drift, and a Lower-Temperature Operating Mode (LTOM), which always maintains sub-boiling temperatures throughout the repository. The HTOM places all waste packages nearly end to end, making the lineal power density greater than in the LTOM. The lower lineal power density in the LTOM was achieved by placing some waste packages farther apart (which results in a larger repository footprint), and through an increased reliance on pre-closure ventilation to remove the waste-package-generated heat. We focus on temperature T and relative humidity RH at the waste-package and drift-wall surfaces, and on in-drift evaporation. In general, HTOM temperatures are greater than corresponding LTOM temperatures, exhibit similar spatial variability and have a stronger dependence on infiltration flux. The duration of RH reduction on waste packages is similar for the LTOM and HTOM. A major difference between the LTOM and HTOM is the lower waste-package temperature at any given value of waste-package RH for the LTOM. Waste-package temperatures in the LTOM, by design, remain below approximately 85 degrees C; the absence of RH reduction arising from host-rock dryout causes waste-package RH to remain above about 40%. The HTOM waste packages experience higher temperatures and correspondingly lower RH conditions as a result of RH reduction arising from host-rock dryout. For most of the repository area, the HTOM delays the potential onset of gravity-driven seepage compared to the LTOM (as indicated by the duration of boiling at the drift wall). Boiling conditions in the HTOM also delays the onset of capillary-driven seepage into the granular invert, causing the HTOM to have less evaporation in the invert during the first 800-1500 years than the LTOM; subsequent evaporation rates are higher in the HTOM, due to the higher power density.

Forecasting↗
PubMed1994

Socioeconomic studies of high-level nuclear waste disposal.

The socioeconomic investigations of possible impacts of the proposed repository for high-level nuclear waste at Yucca Mountain, Nevada, have been unprecedented in several respects. They bear on the public decision that sooner or later will be made as to where and how to dispose permanently of the waste presently at military weapons installations and that continues to accumulate at nuclear power stations. No final decision has yet been made. There is no clear precedent from other countries. The organization of state and federal studies is unique. The state studies involve more disciplines than any previous efforts. They have been carried out in parallel to federal studies and have pioneered in defining some problems and appropriate research methods. A recent annotated bibliography provides interested scientists with a compact guide to the 178 published reports, as well as to relevant journal articles and related documents.

Government Agencies↗
PubMed2000

Impact of measurement uncertainty in chemical quantities on environmental prognosis by geochemical transport modelling.

In Germany, geochemical modelling takes a strong position in two aspects of broader public interest. The first aspect is the safety assessment of a nuclear waste repository, the second is remediation of uranium mining areas. In both aspects, the application of geochemical modelling is stipulated by authorities. This situation results from the possibility to model highly complex situations by computers. The increase in computing power experienced in recent times now offers techniques to assess the sensitivity of modelling results to uncertain input data both in the thermodynamic data base and the site-specific field data. Both aspects are investigated by using Monte Carlo methods in combination with non-parametric statistics. A probabilistic geochemical modelling of uranium mill tailings leaching is demonstrated by application of TReaC modelling code using a simplified site model.

Environmental Monitoring↗
PubMed1980

Environmental Protection Agency--Hazardous waste and consolidated permit regulations, Parts II-IX. Revisions to final rule and interim final rule and requests for comments.

Subtitle C of the Solid Waste Disposal Act, as amended by the Resource Conservation and Recovery Act of 1976, as amended (RCRA), directs the Environmental Protection Agency (EPA) to promulgate regulations to protect human health and the environment from the improper management of hazardous waste. The first phase of EPA's regulations implementing this directive are contained in Parts 262 and 263 of this chapter (which were promulgated on February 26, 1980) and Parts 261, 264, 265, 122, 123, and 124 of this chapter (which are being promulgated today). This regulation (Part 260) sets forth definitions of words and phrases which appear in Parts 261 through 265 and contains provisions which are generally applicable to all those regulations. It was originally published on February 26, 1980, concurrent with the promulgation of EPA's Part 262 and 263 regulations. It is now being amended to add new provisions required by today's publication of Parts 261, 264 and 265 and to revise one of the definitions published in February.

Government Agencies↗
PubMedDate not supplied

Thermally induced natural convection effects in Yucca Mountain drifts.

Thermally induced natural convection from the heat produced by emplaced waste packages is an important heat and mass transfer mechanism within the Yucca Mountain Project (YMP) drifts. Various models for analyzing natural convection have been employed. The equivalent porous medium approach using Darcy's law has been used in many YMP applications. However, this approach has questionable fidelity, especially for turbulent flow conditions. Computational fluid dynamics (CFD), which is based on the fundamental Navier-Stokes equations, is currently being evaluated as a technique to calculate thermally induced natural convection in YMP. Data-model comparisons for turbulent flow conditions show good agreement of CFD predictions with existing experiments including YMP-specific data.

Convection↗
PubMed1980

Environmental Protection Agency--Hazardous waste and consolidated permit regulations, Parts X-XI. Final rule.

This rule establishes consolidated permit program requirements governing the Hazardous Waste Management program under the Resource Conservation and Recovery Act (RCRA), the Underground Injection Control (UIC) program under the Safe Drinking Water Act (SDWA), the National Pollutant Discharge Elimination System (NPDES) program and State Dredge on Fill ("404") programs under the Clean Water Act (CWA), and the Prevention of Significant Deterioration (PSD) program under the Clean Air Act, for three primary purposes: (1) To consolidate program requirements for the RCRA and UIC programs with those already established for the NPDES program. (2) To establish requirements for State programs under the RCRA, UIC, and Section 404 programs. (3) To consolidate permit issuance procedures for EPA-issued Prevention of Significant Deterioration permits under the Clean Air Act with those for the RCRA, UIC, and NPDES programs.

Government Agencies↗
PubMed1990

Current status of nuclear power in the United States and around the world.

Nuclear energy's share of the world electricity market has been growing over the past 35 years. In 1989, eight generating units entered commercial operation abroad and three new units were licensed in the U.S. In early 1990, Mexico became the 26th country to produce electricity from nuclear power. Currently the 426 operating reactors supply one sixth of the world's total electrical capacity. Fourteen countries have now operated nuclear plants for 20 or more years. Since 1980, France has been the leader in the use of nuclear power and currently generates three quarters of its electricity from 54 nuclear plants. The U.S. has 112 nuclear plants, the largest number of any country in the world. These plants satisfy almost 20 percent of U.S. electrical energy requirements. Last year Three Mile Island, the would-be icon for everything that is wrong with the nuclear industry was rated as the most efficient nuclear plant in the world. The worldwide trend toward acceptance of nuclear is improving slightly, but many political and societal issues need to be resolved. Whereas recent polls indicate that a majority of the people realize nuclear must be a major contributor to the energy mix of the future, many are reluctant to support the technology until the issue of waste disposal has been resolved. Fears of another Chernobyl, lack of capital, and a new anti-nuclear campaign by Greenpeace will keep the nuclear debate alive in many countries. Additional stumbling blocks in the U.S. include the need to develop a new generation of improved reactor designs which emphasize passive safety features, standardized designs and a stream-lined federal licensing process. Nuclear power is really not dead. Even environmentalists are starting to give it another look. A nuclear renaissance will occur in the U.S. How soon or under what conditions remain to be seen. The next crisis in the U.S. will not be a shortage of energy, rather a shortage of electricity.(ABSTRACT TRUNCATED AT 250 WORDS)

Asia↗
PubMed2003

Modeling diffusion and adsorption in compacted bentonite: a critical review.

The current way of describing diffusive transport through compacted clays is a simple diffusion model coupled to a linear adsorption coefficient (K(d)). To fit the observed results of cation diffusion, this model is usually extended with an adjustable "surface diffusion" coefficient. Description of the negative adsorption of anions calls for a further adjustment through the use of an "effective porosity". The final model thus includes many fitting parameters. This is inconvenient where predictive modeling is called for (e.g., for waste confinement using compacted clay liners). The diffusion/adsorption models in current use have been derived from the common hydrogeological equation of advection/dispersion/adsorption. However, certain simplifications were also borrowed without questioning their applicability to the case of compacted clays. Among these simplifications, the assumption that the volume of the adsorbed phase is negligible should be discussed. We propose a modified diffusion/adsorption model that accounts for the volume of the adsorbed phase. It suggests that diffusion through highly compacted clay takes place through the interlayers (i.e., in the adsorbed phase). Quantitative prediction of the diffusive flux will necessitate more detailed descriptions of surface reactivity and of the mobility of interlayer species.

Adsorption↗
PubMed2003

Uranium(VL) interactions with OPC/PFA grout.

The sorption of uranium on to Ordinary Portland Cement (OPC)/Pulverized Fuel Ash (PFA, fly ash) grout material has been investigated with respect to time, pH, grout:uranium ratio and the chemical composition of the supporting solution. The information obtained is of relevance to the disposal of low-level nuclear waste. The grout material has been chemically characterised and is negatively charged above pH 2.3. At the uranium concentrations studied (2 microM) all uranyl hydroxide aqueous species are expected to be monomeric, rather than polymeric. Uranium(VI) sorption on to the grout material has been explained in terms of inner sphere complexation binding by means of hydroxide bridge formation between the uranium and grout surface. It is also proposed that oligomeric uranyl species are formed across the grout surface, perhaps stabilising the repulsive effects of the negatively charged grout surface and anionic uranyl hydroxide species. Thermodynamic modelling has been used to explain the sorption variation versus solution pH and identifies potential binding mechanisms.

Adsorption↗
PubMed1995

The delayed respiratory consequences of inhaled radionuclides in population exposed to nuclear catastrophe.

Cytological analysis of bronchoalveolar lavage (BAL) and x-ray energy dispersive spectrometry of intercellular compounds were evaluated in 19 workers ("liquidators") commissioned to clean and contain the nuclear waste after the Chernobyl catastrophe in comparison with ten control subjects. Results showed a significant increase of neutrophils, small monocyte-like alveolar macrophages (AM) and AM with large black cytoplasmic inclusions. In addition, such mineral elements as Zr, Ce, Pr, Sm, Pa, PU and Cs were detected in AM phagosomes in liquidators. These elements were reported as markers of Chernobyl-type nuclear fuel. It is recognized that BAL gives access to particulate matter present in lung parenchyma. Thus, spectrometric analysis of AM inclusions can provide reliable information about the exposure to inhaled radionuclides seven years after the catastrophe.

Administration, Inhalation↗
PubMed2004

A triple-continuum approach for modeling flow and transport processes in fractured rock.

This paper presents a triple-continuum conceptual model for simulating flow and transport processes in fractured rock. Field data collected from the unsaturated zone of Yucca Mountain, a repository site of high-level nuclear waste, show a large number of small-scale fractures. The effect of these small fractures has not been considered in previous modeling investigations within the context of a continuum approach. A new triple-continuum model (consisting of matrix, small-fracture, and large-fracture continua) has been developed to investigate the effect of these small fractures. This paper derives the model formulation and discusses the basic triple-continuum behavior of flow and transport processes under different conditions, using both analytical solutions and numerical approaches. The simulation results from the site-scale model of the unsaturated zone of Yucca Mountain indicate that these small fractures may have an important effect on radionuclide transport within the mountain.

Geological Phenomena↗
PubMed2003

Disposal of spent tributylphosphate by gliding arc plasma.

The gliding arc in humid air is a relevant source of free radicals and strongly oxidising species such as HO* (shown by emission spectroscopy), which are able to degrade organic wastes. This feature was used in a new process for mineralising spent tributylphosphate (TBP) which is an important waste from nuclear industry. The degradation kinetics is examined by monitoring the conversion of TBP into phosphoric acid in a batch reactor. The kinetics exhibits three steps and especially an overall zero-order linear step with a rate of 10 mmol h(-1) at the beginning of the treatment. This zero-order step agrees with a surface oxidation process. After a 13.7h treatment, about 45% of the TBP is converted into inorganic phosphorus compounds, with phosphoric acid as the major product (63% of inorganic phosphorus compounds), and at least 19.5% is not degraded. Dibutylphosphoric acid (HDBP) was identified as the main by-product by a nuclear magnetic resonance technique, infrared spectroscopy and gas chromatography.

Free Radicals↗
PubMed2001

Rock matrix diffusivity determinations by in-situ electrical conductivity measurements.

A fast method to determine rock matrix diffusion properties directly in the bedrock would be valuable in the investigation of a possible site for disposal of nuclear waste. An "effective diffusivity borehole log" would provide important information on the variability of this entity over the area studied. As opposed to traditional matrix diffusion laboratory experiments, electrical conductivity measurements are fast, inexpensive and also easy to carry out in-situ. In this study, electrical resistivity data from borehole logging, as well as from measurements on the actual core, is evaluated with the purpose of extracting matrix diffusivity data. The influence of migration of ions in the electrical double layer, which can be of great importance in low ionic strength pore water, is also considered in evaluating the in-situ data to accurately determine the effective pore diffusivity. The in-situ data compare fairly well to those measured in the rock core.

Diffusion↗
PubMed2005

High level waste tank closure project: ALARA applications at the Idaho National Engineering and Environmental Laboratory.

Bechtel BWXT Idaho, Maintenance and Operating Contractor for the Department of Energy at the Idaho National Engineering and Environmental Laboratory, has emptied, cleaned, and sampled six of the eleven 1.135 x 10(6) L high level waste underground storage tanks at the Idaho Nuclear Technology and Engineering Center, well ahead of the State of Idaho Consent Order cleaning schedule. Cleaning of a seventh tank is expected to be complete by the end of calendar year 2004. The tanks, with associated vaults, valve boxes, and distribution systems, are being closed to meet Resource Conservation and Recovery Act regulations and Department of Energy orders. The use of remotely operated equipment placed in the tanks through existing tank riser access points, sampling methods and application of as-low-as-reasonably-achievable (ALARA) principles have proven effective in keeping personnel dose low during equipment removal, tank, vault, and valve box cleaning, and sampling activities, currently at 0.03 Sv.

Decontamination↗
PubMed1986

Microbial release of 226Ra2+ from (Ba,Ra)SO4 sludges from uranium mine wastes.

226Ra2+ is removed from uranium mine effluents by coprecipitation with BaSO4. (Ba,Ra)SO4 sludge samples from two Canadian mine sites were found to contain active heterotrophic populations of aerobic, anaerobic, denitrifying, and sulfate-reducing bacteria. Under laboratory conditions, sulfate reduction occurred in batch cultures when carbon sources such as acetate, glucose, glycollate, lactate, or pyruvate were added to samples of (Ba,Ra)SO4 sludge. No external sources of nitrogen or phosphate were required for this activity. Further studies with lactate supplementation showed that once the soluble SO4(2-) in the overlying water was depleted, Ba2+ and 226Ra2+ were dissolved from the (Ba,Ra)SO4 sludge, with the concurrent production of S2-. Levels of dissolved 226Ra2+ reached approximately 400 Bq/liter after 10 weeks of incubation. Results suggest that the ultimate disposal of these sludges must maintain conditions to minimize the activity of the indigenous sulfate-reducing bacteria to ensure that unacceptably high levels of 226Ra2+ are not released to the environment.

Bacteria↗
PubMed1993

Childhood leukemia incidence in the vicinity of La Hague nuclear-waste reprocessing facility (France).

The incidence of leukemia is examined in young people (aged under 25 years) living within a 35 km radius of the French nuclear-waste reprocessing plant operating in La Hague, Normandy. During the period 1978-90, a total of 23 cases was diagnosed, giving an incidence rate of 2.99 per 100,000 which is close to the expected rate. In the 'canton' in which the nuclear plant is located, three cases of leukemia were observed compared with 1.2 expected, giving a standardized incidence ratio of 2.5. This nonsignificant finding is compatible with no increased risk and also with a sevenfold excess risk. Therefore, it reinforces the necessity of conducting a case-control survey, which is now planned, to assess the part played by occupational radiation exposure in leukemia incidence for this French area.

Acute Disease↗
PubMed2001

A study of the corrosion products of mild steel in high ionic strength brines.

The corrosion layer on steel surfaces that formed after exposure to waste isolation pilot plant (WIPP) brines under anoxic conditions was characterized for chemical composition, thickness and phase composition. The chemical composition of the corrosion layer was determined both by X-ray photoelectron spectroscopy (XPS) and by chemical analysis of acid solutions used to remove the corrosion layer. Atomic force microscopic (AFM) images indicated that the brine-corroded surface layer shows extensive granulation along the contours of the steel surface that is characteristic of sharp polishing marks. The corrosion layer seemed to be porous and could be dissolved and detached in dilute hydrochloric acid. The corrosion layer appears to be composed of iron oxides with some ionic substitutions from the brines. The 77 K Mössbauer spectrum recorded for iron powder leached under similar conditions indicated the corrosion layer was comprised principally of green rust.

Corrosion↗