Radioactive Waste Sites Research Articles

Evaluating the long‐term hydrology of an evapotranspiration‐capillary barrier with a 1000 year design life

AbstractA surface barrier is a commonly used technology for isolation of subsurface contaminants. Surface barriers for isolating radioactive waste are expected to perform for centuries to millennia, yet there are very few data for field‐scale surface barriers for periods approaching a decade or longer. The Prototype Hanford Barrier (PHB) with a design life of 1000 years was constructed over an existing radioactive waste site in 1994 to demonstrate its long‐term performance. The primary element of the PHB is an evapotranspiration‐capillary (ETC) barrier in which precipitation water is stored in a fine‐textured soil layer and later released to the atmosphere via evapotranspiration. To address the barrier performance under extreme conditions, this study included an enhanced precipitation stress test from 1995 to 1997 to determine barrier response to extreme precipitation events. During this period a 1000 year 24 h return rainstorm was simulated in March every year. The loss of vegetation on barrier hydrology was tested with a controlled fire test in 2008. The 19 year monitoring record shows that the store‐and‐release mechanism worked as well as or better than the design criterion. Average drainage from the ETC barrier amounted to an average of 0.005 mm yr−1, which is well below the design criterion of 0.5 mm yr−1. After a simulated wildfire, the naturally reestablished vegetation and increased evaporation combined to release the stored water and summer precipitation to the atmosphere such that drainage did not occur in the 5 years subsequent to the fire.

Bioaccumulation characterization of uranium by a novel Streptomyces sporoverrucosus dwc-3

The biosorption mechanisms of uranium on an aerobic bacterial strain Streptomyces sporoverrucosus dwc-3, isolated from a potential disposal site for (ultra-)low uraniferous radioactive waste in Southwest China, were evaluated by using transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), proton induced X-ray emission (PIXE) and enhanced proton backscattering spectrometry (EPBS). Approximately 60% of total uranium at an initial concentration of 10mg/L uranium nitrate solution could be absorbed on 100mg S. sporoverrucosus dwc-3 with an adsorption capacity of more than 3.0mg/g (wet weight) after 12hr at room temperature at pH3.0. The dynamic biosorption process of S. sporoverrucosus dwc-3 for uranyl ions was well described by a pseudo second-order model. S. sporoverrucosus dwc-3 could accumulate uranium on cell walls and within the cell, as revealed by SEM and TEM analysis as well as EDX spectra. XPS and FT-IR analysis further suggested that the absorbed uranium was bound to amino, phosphate and carboxyl groups of the cells. Additionally, PIXE and EPBS results confirmed that ion exchange also contributed to the adsorption process of uranium.

Identification of sources and processes in a low-level radioactive waste site adjacent to landfills: groundwater hydrogeochemistry and isotopes

Multiple tracer-element and isotope approaches were applied at a 1960s-era low-level radioactive waste burial site located in the Lucas Heights area on the southwest urban fringe of Sydney, Australia. The site is situated among other municipal and industrial (solid and liquid) waste disposal sites causing potential mixing of leachates. Local rainfall contains marine-derived major ion ratios that are modified during infiltration depending on waste interactions. The local geology favours the retention of contaminants by ion-exchange processes within the clay-rich soils and the shale layer underlying the burial site. Local soils experience periodic infiltration and wetting fronts that can fully saturate the waste trenches (bathtub effect) while surrounding soils are mostly unsaturated with discontinuous perched lenses. Within the trenches, the degradation of organic matter results in localised methanogenesis, as suggested by enriched δ2H and δ13CDIC values in adjacent subsurface water. Movement of contaminants from the trenches is indicated by Na+, Br− and I− concentrations, variations in 87Sr/86Sr, enriched δ13CDIC values and evolution of δ34S of dissolved sulfate in perched water bodies above the shale. Although transport is limited by the low transmissivity of the clay-rich soils, migration and mixing processes are indicated by the variation of concentrations with distance from the trenches, disappearance of δ2H enrichments, mixing with other sources of Sr and sulfate isotope fractionations. The depth distribution of waste-derived contaminants (specifically 3H and Be) between the perched water surrounding the trenches, and the underlying shale and sandstone layers, indicates limited downward transport of contaminants. Past removal of the shale layer in an adjacent site, Harrington's Quarry, has facilitated the mixing of some municipal waste leachates (characterised by circum-neutral pH, high alkalinity, low sulfate, high 3H, high Be, enriched δ2H and δ13CDIC) into the underlying groundwater system as suggested by high TDS, Cl−/Br− ratios, Be and 3H found in deeper wells. This study demonstrates the applicability of using trace elements, stable- and radio-isotopes to document the existing geochemistry and the contaminant transport from the waste trenches. The multiple tracer approach addresses the complexities of transport at the site and differentiates various municipal, industrial and radioactive waste sources.

Radiation protection, radioactive waste management and site monitoring at the nuclear scientific experimental and educational centre IRT-Sofia at INRNE-BAS.

This article identifies important components and describes the safe practices in implementing radiation protection and radioactive waste management programmes, and in their optimisation at the Nuclear Scientific Experimental and Educational Centre with research reactor IRT at INRNE-BAS. It covers the instrumentation and personal protective equipment and organisational issues related to the continuous site monitoring. The reactor is under major reconstruction and the measures applied to radiation monitoring of environment and working area focused on restricting the radiation exposure of the staff as well as compliance with international good practices related to the environmental and public radiation safety requirements are also addressed.

Biosorption of uranium on Bacillus sp. dwc-2: preliminary investigation on mechanism

In this paper, the biosorption mechanisms of uranium on an aerobic Bacillus sp. dwc-2, isolated from a potential disposal site for (ultra-) low uraniferous radioactive waste in Southwest China, was explored by transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis, FT-IR spectroscopy, proton induced X-ray emission (PIXE) and enhanced proton backscattering spectrometry (EPBS). The biosorption experiments for uranium were carried out at a low pH (pH 3.0), where the uranium solution speciation is dominated by highly mobile uranyl ions. The bioaccumulation was found to be the potential mechanism involved in uranium biosorption by Bacillus sp. dwc-2, and the bioaccumulated uranium was deposited in the cell interior as needle shaped particles at pH 3.0, as revealed by TEM analysis as well as EDX spectra. FTIR analysis further suggested that the absorbed uranium was bound to amino, phosphate and carboxyl groups of bacterial cells. Additionally, PIXE and EPBS results confirmed that ion-exchange also contributed to the adsorption process of uranium. All the results implied that the biosorption mechanism of uranium on Bacillus sp. is complicated and at least involves bioaccumulation, ion exchange and complexation process.

Indian Program for Vitrification of High Level Radioactive Liquid Waste

Nuclear Power Programme in India is based on “closed fuel cycle”. Closed fuel cycle involves reprocessing and recycling of Spent Nuclear Fuel (SNF) coming out of nuclear reactors. During reprocessing, uranium &plutonium, constituting bulk of the SNF are separated and subsequently recycled. The remaining small portion constitutes high level radioactive waste containing most of the fission products and minor actinides. A three-step strategy involving immobilization, interim storage followed by ultimate disposal has been adopted in India for management of High Level Waste (HLW). Borosilicate glass matrix has been identified for immobilization of HLW owing to optimal waste loading, adequate leach resistance and long term stability of the product. Glass formulations are developed by suitable addition of modifiers to accommodate compositional variation in the waste. Detailed characterization studies are carried out to understand the structural modifications in the three dimensional network of incorporation of waste constituents followed by product characterization to ascertain the properties of the conditioned vitrified waste product (VWP). On the strength of these indigenous developments, Indian vitrification facilities are in operation at Trombay, Tarapur and Kalpakkam. Different types of melters like metallic, Joule Heated Ceramic Melter (JHCM) have been successfully deployed on industrial scale for vitrification of HLW. A Cold Crucible Induction Melter (CCIM) has also been developed. An interim storage facility is in operation for storage and surveillance of VWP. A site selection programme has been initiated to identify a few suitable geological domains for identifying a candidate disposal site for high level and long lived radioactive wastes. Presently granites have been studied extensively as a host rock & as a natural barrier. Long term evaluation of vitrified high level waste under geological conditions and its comparison with natural analogues (basaltic & obsidian) is being pursued in India.

Trench ‘Bathtubbing’ and Surface Plutonium Contamination at a Legacy Radioactive Waste Site

Radioactive waste containing a few grams of plutonium (Pu) was disposed between 1960 and 1968 in trenches at the Little Forest Burial Ground (LFBG), near Sydney, Australia. A water sampling point installed in a former trench has enabled the radionuclide content of trench water and the response of the water level to rainfall to be studied. The trench water contains readily measurable Pu activity (∼12 Bq/L of 239+240Pu in 0.45 μm-filtered water), and there is an associated contamination of Pu in surface soils. The highest 239+240Pu soil activity was 829 Bq/kg in a shallow sample (0–1 cm depth) near the trench sampling point. Away from the trenches, the elevated concentrations of Pu in surface soils extend for tens of meters down-slope. The broader contamination may be partly attributable to dispersion events in the first decade after disposal, after which a layer of soil was added above the trenched area. Since this time, further Pu contamination has occurred near the trench-sampler within this added layer. The water level in the trench-sampler responds quickly to rainfall and intermittently reaches the surface, hence the Pu dispersion is attributed to saturation and overflow of the trenches during extreme rainfall events, referred to as the ‘bathtub’ effect.

Study of degenerate parabolic system modeling the hydrogen displacement in a nuclear waste repository

Our goal is the mathematical analysis of a two phase (liquid and gas) two components (water and hydrogen) system modeling the hydrogen displacement in a storage site for radioactive waste. We suppose that the water is only in the liquid phase and is incompressible. The hydrogen in the gas phase is supposed compressible and could be dissolved into the water with the Henry law. The flow is described by the conservation of the mass of each components. The model is treated without simplified assumptions on the gas density. This model is degenerated due to vanishing terms. We establish an existence result for the nonlinear degenerate parabolic system based on new energy estimate on pressures.

Geophysical Evidence through a CSAMT Survey of the Deep Geological Structure at a Potential Radioactive Waste Site at Beishan, Gansu, China

This paper describes a controlled-source audio-frequency magnetotellurics (CSAMT) survey conducted in August 2009 over a potential high-level radioactive waste (HLRW) disposal site in northwestern China. The site is primarily covered with well-developed metamorphic rocks. The purpose of the CSAMT survey was to map the outcropped faults to depth and identify any hidden faults or weakened zone in the subsurface. The site is located in the arid Beishan area, Gansu Province. Substantial challenges were encountered in acquiring quality electrical field data because of the highly resistive ground. Satisfactory electrode contact conditions were generally maintained by applying salt-saturated water to both the transmitting electrodes and the receiving electrodes. The excitation frequency ranges from 9,600 Hz to 1 Hz with a target depth of investigation of 1,000 m. The CSAMT data were processed in several steps. Low-pass filtering was applied to remove the static effect caused by the local electrical inhomogeneities near the ground surface. An optimum filter length was found through experiment to yield the maximum static effect reduction. The pre-processed data are inverted for geoelectrical cross sections using a 2-D inversion method. Inversion artifacts were suppressed by imposing a model smoothness constraint. The inversion reveals several important results. First, the inversion cross sections correctly recognized the fractures and deformation bands mapped at the surface. The cross sections also identified four new faults that were not observed in the geological survey. The inversion profiles suggested that the narrow factures and deformation bands observed along survey line 1 extend to a great depth. The profile helped identify a possible weak mineralization zone along survey line 2. Considering the regional tectonic stress direction, the lower resistivity zone suggests that the faults parallel to survey line 2 are subject to an extensional or transtensional force that produces a broad and broken alteration zone. Although subject to further drilling confirmation, these interpretation results greatly enhance the understanding of the deep geological hazards at the Beishan site.

Transportation of radioactive wastes to the site «Vector» and site «Buryakovka» for radioactive wastes

В статті представлено вивчення альтернативних маршрутів безпечного та надійного транспортування радіоактивних відходів на комплекс «Вектор» та ПЗРВ «Буряківка».

The Diffusion of Tc-99 in Beishan Granite-Temperature Effect

In the safety assessment of a potential site for high-level radioactive wastes (HLW) disposal, the investigation on the geochemical behaviors of key radionuclides with the possibility for releasing from the potential repository is an important aspect. Due to the high mobility of technetium under most repository conditions, lots of research works were performed to investigate the diffusion of technetium in different potential rocks. In spite of these studies, there remains a lack of data addressing temperature effects. In this paper, the diffusion of 99Tc in Beishan granite at temperatures from 25℃ to 55℃ was studied with laboratory small scale diffusion devices. The experimental data were fitted with a finite difference scheme to get the effective diffusion coefficient (De) of . The results indicated that the relationship of De with temperatures could be described as the modified Stokes-Einstein equation, and the formation factor of Beishan granite was constant in the temperature range of 25℃ - 55℃ with the value of (3.91 ± 1.77) × 10-4.

Modeling the hazard levels of stress-strain state in structural blocks in Nizhnekanskii granitoid massif for selecting nuclear waste disposal sites

The results of studies aimed to develop a method for predicting the destruction hazard of structural-tectonic blocks based on the energy analysis of stress fields are considered. The analysis took into account the strength-related hazard criteria reflecting the rock tendency to destruction in structural blocks. The criteria were used to identify the relevant hazard levels in the stress-strain state for Nizhnekanskii granitoid massif as the most likely disposal site for high-level radioactive wastes. For active faults, in addition to estimates based on the concentration of potential energy of shape change, which plays a dominating role in the case of inactive faults, it is proposed to make additional estimates based on the concentration of potential energy of deformation and the rate of maximal energy decrease. An example of ranging the structural blocks by decreasing hazard of the stress-strain state is given.

Analysis of 36Cl in Savannah River Site radioactive waste

Radioactive waste cleanup and subsequent closure of waste storage tanks is currently underway at the Savannah River Site, prompting the need to characterize the residual contents (heels) of the tanks. Each tank heel has variable chemical constituents and radiological distributions that pose unique analyte characterization and quantification challenges. For example, similar target detection limits for each tank heel are often difficult to meet as a result of complex matrices and methods must be tailored to characterize each new tank heel to the level of detection required. Furthermore, continuous programmatic evaluations of allowable closed-tank radiological inventories result in steadily decreasing detection limit targets for many of the isotopes required for characterization. Some of the target isotopes required for characterization need to be quantified to levels approaching 10 orders of magnitude below the radioactive concentrations of interfering isotopes. One particularly troublesome target analyte is 36Cl. As a pure beta-emitting radionuclide, 36Cl (T1/2 = 3.01 × 105 ± 3,000 years) must be isolated from interfering beta-emitting radionuclides such as 90Sr, 90Y, 137Cs, 99Tc, and 14C, as well as actinides and lanthanides prior to quantification. Due to its half-life, the target detection limit for 36Cl is extremely low compared to the concentrations of other beta-emitting radionuclides typically present in residual tank solids. A method of analysis for 36Cl was developed which utilizes a combination of traced acid digestion of radioactive waste tank samples followed by aggressive decontamination of interfering beta-emitting radionuclides via repeated resin-strikes, distillation, precipitation as AgCl, and analysis by gas flow proportional counting for the 36Cl—containing precipitate. The separation is traced by neutron activation analysis of stable chloride imparted during the initial digestion, and results are corrected for the separation yield. Recent campaigns have successfully achieved interference-free AgCl precipitates and, ultimately, detection limits of 0.37 Bq/g from matrices containing ~1E7 Bq/g of other beta-emitting radionuclides.

Migration of transuranic elements in groundwater from the near-surface radioactive waste site

► Plutonium isotopes spatial distribution in unconfined aquifer near shallow waste dump. ► We found that plutonium in aquifer was originated from the dump. ► Pu mobility in waste and aquifer is characterized by in situ partition coefficients. ► Pu in groundwater is associated mainly with low molecular weight species (<1 kDa). Field experiments and laboratory studies were performed to investigate migration processes of plutonium isotopes from a near-surface radioactive waste trench to the underlying sandy aquifer at the Red Forest waste dump in the Chernobyl zone. The objectives of these experiments were to characterize the spatial distribution and possible migration mechanisms of plutonium in the aquifer. During 2002–2007 experimental investigations were carried out and spatial distributions of plutonium isotopes ( 239 , 240 Pu, 238 Pu), 90 Sr and major ions in the aquifer in the direction of the groundwater flow were obtained. Specific activities of radionuclides in groundwater depended on the location of the piezometer and varied in the range of 1–360 mBq kg −1 for 239 , 240 Pu, 0.5–180 mBq kg −1 for 238 Pu and n–n·10 4 Bq kg −1 for 90 Sr. It was found that the spatial features of the distributions of plutonium and strontium specific activities in the upper eolian aquifer were similar, i.e. there was a correlation between the positions of the activity maxima of the radionuclides. The Pu isotopes plume in the aquifer spreads about 15 m downstream of the radionuclides source. Characterization of the initial radionuclide composition of the waste showed that all plutonium in the aquifer originated from the trench. The ratio of plutonium isotopes ( 239 , 240 Pu/ 238 Pu) at the sampling time was the same in waste material and in groundwater samples. In situ ultrafiltration of several groundwater samples was carried out. The size fractionation data obtained suggest that a significant part of plutonium (50–98%) in the groundwater sampled close to the source from the upper part of the aquifer is associated with a very low molecular weight fraction (<1 kDa).

Modelling of a Generic Near-Surface Disposal System

ABSTRACTDevelopment of numerical tools for performance assessment studies of radioactive waste disposal facilities, must address the management of the wide-ranging uncertainties associated with the long-term behaviour of these complex systems. Different approaches and assumptions are made in order to identify and describe relationships between the disposal system and its environment. They take into account, among other factors, the uncertainties associated with temporal evolution of the system within a proposed scenario; the landscape changes arising from future human actions, climate and geological events and processes; the relationships between components of the disposal system and its immediate environment; the behaviour and characteristics of radionuclides within the system and their role in contributing to radiation exposure. In all cases, the different scenario-based models are typically used to determine the radiological significance of potential future discharges from waste disposal facilities. However, it is important to keep always in mind that in any specific case, the purpose of developing and/or applying a model may vary from a simple calculation (e.g. to support concept development) to detailed site-specific performance assessment in support of a disposal license application. The assumptions and modelling simplifications that are appropriate to one type of calculation may not be so easily justified in different circumstances. In order to develop the capability of modelling different long-term scenarios for a generic disposal site for low and intermediate level radioactive wastes, implementation of models of both the near-field/geosphere and biosphere were performed using general approaches for geosphere-biosphere interface, with sub-models for the whole system.

Critical Mechanisms for Critical Masses: Exploring Variation in Opposition to Low-Level Radioactive Waste Site Proposals

Between 1986 and 1993, local activists in the U.S. organized more than 900 collective acts of public opposition to low-level radioactive waste site proposals across twenty-one counties. Yet, the number of such acts varied significantly across the counties. Both waste-siting professionals and social movement scholars have sought to identify factors of mobilization to explain such variation. An analysis of these cases reveals that a focus limited to pre-existing factors of mobilization—whether the demographic and economic factors favored by siting professionals, or the mobilization and political opportunity structures of the "classic social movement agenda"—badly misjudges mobilization. A paired comparison of two counties that differed dramatically in the number of acts of collective opposition mustered over the course of the siting process demonstrates the importance of social mechanisms that shape just how a community interacts with its political resources. The key differences between the two counties lie in the setting, sequence, and in the combination of the following social mechanisms: social appropriation, identify shift, and the attribution of threat and opportunity. To understand the assertion of local political power in an implementation process such as siting efforts, we need to understand not only the political resources available in a community context, but also the way in which human relationships shape the perception and application of that context.

Microbiological processes in the Severnyi deep disposal site for liquid radioactive wastes

Local monitoring of physicochemical, radiochemical, and microbiological parameters was performed in the deep horizons of the Severnyi site used for disposal of liquid radioactive waste (LRW). Analysis of the chemical and radiochemical composition of the wastes and formation fluid revealed that the boundary for migration of radionuclides lagged behind that for nonradioactive waste components (sodium nitrate) and tritium. The physicochemical and radiochemical conditions in deep horizons did not prevent microbial growth. The numbers of microorganisms (aerobic organotrophs, denitrifying, fermentative, sulfate-reducing, and methanogenic) were low, as were the rates of sulfate reduction and methanogenesis; they increased in the waste dispersion zone. The microorganisms from deep horizons were able to produce gases (CH4, CO2, N2, and H2S) from possible waste components. Denitrifying bacteria belonged to different Pseudomonas species and reduced nitrate to dinitrogen under the conditions of pH, salinity, temperature, and radioactivity found in the disposal site. These results suggest the need for control of microbiological processes in deep disposal site for liquid RW.

Concerned public and the paralysis of decision‐making: nuclear waste management policy in Germany

Efforts to site a high level nuclear waste repository in Germany date back to the 1960s. Ten years later the site Gorleben was officially selected and designated as a host for nuclear waste. However, public opposition and maneuvering by the major political actors prevented the completion of the site selection process, resulting in decades of political paralysis. The main reasons for this failure were the polarization in advocates and opponents of nuclear energy, the neglect for due process and participatory procedures, the inability to integrate technical, political, and social rationales in designing a viable nuclear waste policy, and the confusing mix of responsibilities between and among political actors. In spite of the apparent failure to find a solution for high level waste, the German government succeeded in designating a site for radioactive waste with negligible heat generation (Konrad mine). It is assumed that further progress in waste management can be accomplished only if more deliberative elements are introduced into the policy arena.

High cell density production of Deinococcus radiodurans under optimized conditions

Deinococcus radiodurans is a bacterium being investigated for mechanisms of extreme radiation resistance and for bioremediation of environmental radioactive waste sites. In both fundamental and applied research settings, methods for large-scale production of D. radiodurans are needed. In this study, a systematic investigation was carried out to optimize D. radiodurans production at the 20-L fermentor scale. In defined medium, the phosphate buffer typically used was found to be inhibitory to D. radiodurans growth, and caused cell aggregation. Substitution of HEPES and MOPS buffers for phosphate buffer improved D. radiodurans growth characteristics. Several antifoaming agents were investigated to support large-scale production with submerged aeration, and the defoamer KFO 673 was chosen based on its ability to prevent foaming without affecting D. radiodurans growth. The conventional undefined rich medium tryptone/glucose/yeast extract (TGY) maximally supported D. radiodurans growth to an OD(600) of 10. Using a 'design of experiments' approach, we found glucose, Mg and Mn to be critical in supporting high-density growth of D. radiodurans. The optimal pH and temperature for D. radiodurans growth in large-scale preparations were 7.0 and 37 degrees C, respectively. Growth was carried out in a 20-L fermentor using the newly developed media under the optimal conditions. With addition of 10 g/L glucose, 0.5 g/L MgSO(4) . 7H(2)O, 5 microM MnCl(2) into TGY media, an OD(600) of 40 was achieved.

Disruption or Convention? A Process-based Explanation of Divergent Repertoires of Contention Among Opponents to Low-level Radioactive Waste Disposal Sites

Violence, disruption and convention constitute three well established categories of collective action repertoires available to contemporary social movements. What factors shape differences in repertoire selection across social movement groups? I take a process-based approach to answer this question, examining two grassroots opposition movements to the disposal of low-level radioactive waste in the United States. The two rural New York State counties I consider each faced a state-imposed low-level radioactive waste site proposal in 1988. Activists in each county mounted vigorous collective opposition to the proposed facility, while exhibiting distinct repertoires of collective action. Activists in Allegany County pursued disruptive civil disobedience, while activists in Cortland County pursued a conventional repertoire of citizen lobbying and litigation efforts. Similarities across a variety of demographic, political, and social characteristics in these two counties leave the standard explanations for repertoire selection put forth in the social movement literature wanting. I argue that the relationship developed between the respective county governments and citizen activists during the waste-site proposal dispute had a dramatic effect on the dominant repertoire of collective action adopted by each community. More specifically, identifying the presence or absence of the social mechanism of brokerage between local government and activists is crucial to understanding the different trajectories of these movement groups. This article highlights the utility of fine-grained process-based analysis as a complement to variable-based approaches for explaining social movement activity, and the importance of the mechanism of brokerage among local government and activists for understanding bottom-up movements responding to proximate grievances, such as the environmental justice movement.