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PubMed1991

Introduction: present knowledge on the effects of radioactive contamination on pregnancy outcome.

This introduction gives a brief review of the effects on pregnancy outcome that might follow radioactive contamination of the environment. These include miscarriages, congenital anomalies, damage to the central nervous system expressed through reduced intelligence and a risk of tumours late in life. Knowledge is fragmentary and field studies are difficult, which lends weight to the attempts at studying the effects of the Chernobyl accident in Europe which are the subject of the present symposium.

Accidents↗
PubMed1995

Reduced fertility after the crash of a U.S. bomber carrying nuclear weapons? A register-based study on male fertility.

A register-based study was performed to elucidate whether workers employed on the Thule air base in the clean-up period after the crash of a U.S. B-52 bomber carrying nuclear bombs had reduced fertility, as measured by the numbers of liveborn children. The highest birth rates were among 25-34-year olds with 1-3 years of employment on the base, but who had not worked at the base the year before, who already had one child, with a 2-5-year interval since the birth of the last child. No difference was seen between the group of men who had worked at the base during the clean-up period after the crash--the possibly exposed group--and those people who had worked at the base only outside the clean-up period. Because of the massive media coverage and possible claims for damages a register-based study is the only practicable way of elucidating statements about infertility. The main conclusion is that the accident has not reduced fertility.

Accidents, Aviation↗
PubMedDate not supplied

Reusability of plastic scintillators used in beta emitter activity determination.

The use of plastic scintillation in the measurement of beta emitter activity is a suitable alternative to classical detection techniques in spite of the high cost and potential memory effects. Reuse of the plastic scintillator beads after a cleanup procedure would overcome both drawbacks. In the present paper, we tested several cleaning solutions (water, HCl 0.1M, commercial soap, EDTA 0.01 M pH=3, citric acid 0.1 M pH=3). The recommended procedure consists of the immersion of the beads in three consecutive citric acid baths for 24 h. If this protocol is followed, plastic beads contaminated with 90Sr/90Y, 14C, and 3H recover their initial condition, and can be used in successive determinations.

Beta Particles↗
PubMedDate not supplied

Plutonium isotope ratios in the Yenisey and Ob estuaries.

Over the past 50 years, nuclear weapons' tests and releases from the nuclear industry have introduced anthropogenic plutonium into the environment. In the Arctic environment, the main source of plutonium is from the atmospheric weapons testing, but previous studies of plutonium in the Kara Sea have shown that, at certain sites, other releases can give rise to enhanced local concentrations. The present paper presents results from determination of plutonium concentrations and isotope ratios in the sediment samples collected during various expeditions to the Kara Sea, the Ob and Yenisey estuaries and their river systems. The data indicated a clear influence from a low 240Pu:239Pu source in surface sediments collected from the Yenisey estuary, whereas plutonium in Ob estuary sediments is dominated by global fallout. The results also show an increase in plutonium concentration (from 0.003 to 11Bq/kg) and a decrease in 240Pu:239Pu isotope ratio (from 0.16 to 0.05) going upstream from the Yenisey estuary towards the nuclear installation at Krashnoyarsk.

Arctic Regions↗
PubMed2006

Foam formation and mitigation in a three-phase gas-liquid-particulate system.

Foaming is of great concern in a number of industrial processes involving three-phase gas-liquid-finely divided solid systems such as those encountered in the vitrification of highly radioactive nuclear waste slurries and sludges. Recent work has clearly shown that the surface properties of the particles such as hydrophilicity, hydrophobicity or biphilicity (i.e. partially wetted by water) are the cause of foamability and foam stability. The literature data on particles causing foaminess and foam stability in the absence of any surfactant are rather scarce. This paper presents experimental observations on aqueous foams with polyhedral structures containing over 90% air generated due to the presence of irregularly-shaped fine crystalline particles of sodium chloride which were modified into amphiphilic particles by physical adsorption of a cationic surfactant. Cross-polarized light microscopy was used to visualize the physical adsorption of the surfactant on the crystal surface. It is shown that these biphilic or amphiphilic particles attach to the air bubble surface and prevent the coalescence of bubbles, thereby extending the life of the foam. The foaming power of solid particles increases with an increase in the concentration of amphiphilic particles, and a maximum in foaminess is observed which is due to two competing effects. Amphiphilic particles promote foamability by attachment to the bubble surfaces as individual particles and foam inhibition due to the clustering or flocculation of particles in the bulk at high particle concentrations. We studied the adsorption of amphiphilic particles at a planar air-water surface and found that the degree of foamability correlates well with the particle coverage (i.e. adsorption density) at the air-liquid surface. An exploratory study was also conducted using an antifoam recently developed by IIT researchers to mitigate foaming in particle-laden gas-liquid systems.

Colloids↗
PubMed2004

The uptake of uranium by Eleocharis dulcis (Chinese water chestnut) in the Ranger Uranium Mine constructed wetland filter.

Eleocharis dulcis has proliferated in a constructed wetland used to treat uranium mine runoff water, where it rapidly accumulates significant quantities of uranium (U) in its roots and relatively little in its stems. We investigated the mechanism of U uptake and accumulation by E. dulcis using field-sampling techniques and microcosm test work. Results from the microcosm trials and outcomes from statistical tests of field sampled macrophyte, water and sediment indicate that the primary source of U for E. dulcis is the water column. Basipetal translocation of U to the plant's roots was indicated by significant correlations between the U content of stems, taproots and rhizomes and XPS detection of U inside root segments. U sequestering from sediment interstitial water by Fe hydroxides on root surfaces was also evident. No basipetal translocation was evident following the 28-day duration of the microcosm experiments, indicating that it is a longer-term process.

Biodegradation, Environmental↗
PubMed2005

Radiation safety aspects of brachytherapy for prostate cancer using permanently implanted sources. A report of ICRP Publication 98.

The use of permanent radioactive implants (125I or 103Pd seeds) to treat selected localised prostate cancer patients has been increasing rapidly all over the world for the last 15 years. It is estimated that more than 50,000 patients are treated this way every year in the world, and this number is anticipated to increase in the near future. Although no accidents or adverse effects involving medical staff and/or members of the patient's family have been reported to date, this brachytherapy technique raises a number of radiation safety issues that need specific recommendations from the ICRP. All data concerning the dose received by people approaching patients after implantation have been reviewed. Those doses have been either been measured directly or calculated. The available data show that, in the vast majority of cases, the dose to comforters and carers remains well below the recommended limit of 1 mSv/year. Only the (rare) case where the patient's partner is pregnant at the time of implantation may need specific precautions. Expulsion of sources through urine, semen, or the gastro-intestinal tract is rare. Specific recommendations should be given to patients to allow them to deal adequately with this event. Of note, due to the low activity of an isolated seed and its low photon energy, no incident/accident linked to seed loss has ever been recorded. When performed in the first few months after implantation, cremation of bodies (frequent in some countries) raises several issues related to: (1) the activity that remains in the patient's ashes; and (2) the airborne dose, potentially inhaled by crematorium staff or members of the public. Review of available data shows that cremation can be allowed if 12 months have elapsed since implantation with 125I (3 months for 103Pd). If the patient dies before this delay has elapsed, specific measures must be undertaken. Specific recommendations have to be given to the patient to warn his surgeon in case of subsequent pelvic or abdominal surgery. A 'wallet card' with all relevant information about the implant is useful. In most cases, brachytherapy does make the patient infertile. However, although the therapy-related modifications of the semen reduce fertility, patients must be aware of the possibility of fathering children after such a permanent implantation, with a limited risk of genetic effects for the child. Patients with permanent implants must be aware of the possibility of triggering certain types of security radiation monitors. The 'wallet card' including the main information about the implant (see above) may prove to be helpful in such a case. Considering the available experience after brachytherapy and external irradiation of prostate cancer, the risk of radio-induced secondary tumours appears to be extremely low. The demonstrated benefit of brachytherapy clearly outweighs, by far, the very limited (mainly theoretical)increase in the radiation-induced cancer risk.

Brachytherapy↗
PubMed2005

High-salt stabilization of Laponite clay particles.

Colloidal radioactive transuranic wastes are currently buried in large tanks in the form of dense colloids in high salt, high pH aqueous media. These facilities are beginning to fail, so it is necessary to transport and "package" them for more permanent disposal, processes requiring understanding of the microstructure that develops under such conditions. Laponite RD clay is believed to be a good simulant for the colloids in the waste tanks, and the present study addresses their behavior under high salt conditions, where previous studies have frequently observed the phenomenon of "restabilization," i.e., the attainment of aggregation stability at high electrolyte conditions. Specifically, the aggregation kinetics and the resulting cluster structure (fractal dimension) of Laponite RD clay colloids at high concentrations of BaCl2 (an electrolyte previously shown to lead to restabilization) are investigated. At low-to-intermediate electrolyte concentrations, the clay is found to behave in accord with DLVO theory, i.e., low salt conditions yield slow aggregation into densely-packed aggregates, whereas intermediate salt concentrations, sufficient to cause double layer collapse, produce rapid aggregation into open aggregates. High salt concentrations, however, show slow rates of aggregation. The aggregate structure under these conditions is found to mimic that found for very low electrolyte concentrations, i.e., high fractal dimension. Further experiments show that a sudden increase in salt concentration in a system containing young open aggregates produced under intermediate salt concentrations causes them to reform into more compact structures.

Journal Article↗
PubMed2004

In situ tracer tests to determine retention properties of a block scale fracture network in granitic rock at the Aspö Hard Rock Laboratory, Sweden.

Experiments were conducted at the Aspö Hard Rock Laboratory in order to improve the understanding of radionuclide retention properties of fractured crystalline bedrock in the 10-100 m scale (TRUE Block Scale Project, jointly funded by ANDRA, ENRESA, Nirex, JNC, Posiva and SKB). A series of tracer experiments were performed using sorbing tracers in three different flow paths. The different flow paths had Euclidian lengths of 14, 17 and 33 m, respectively, and one to three water conducting structures. Four tests were performed using different cocktails made up of radioactive sorbing tracers (22,24Na+, 42K+, 47Ca2+, 85Sr2+, 83,86Rb+, 131,133Ba2+ and 134,137Cs+). For each tracer injection, the breakthrough of sorbing tracers was compared to the breakthrough of a conservative tracer, 82Br-, 131I-, HTO and 186ReO4-, respectively. In the two longer flow paths, no breakthrough of 83Rb+ and 137Cs+ was observed after 8 months of pumping. Selected tracer tests were subject to basic modelling in which a one-dimensional (1D) advection-dispersion model, including surface sorption, and an unlimited matrix diffusion were used for the interpretation of the results. The results of the modelling indicated that there is a slightly higher mass transfer into a highly porous material in the block-scale experiment compared with in situ experiments performed over shorter distances and significantly higher than what would have been expected from laboratory data obtained from studies of the interactions in nonaltered intact rock.

Geological Phenomena↗
PubMed2004

Field investigation into unsaturated flow and transport in a fault: model analyses.

Results of a fault test performed in the unsaturated zone of Yucca Mountain, Nevada, were analyzed using a three-dimensional numerical model. The fault was explicitly represented as a discrete feature and the surrounding rock was treated as a dual-continuum (fracture-matrix) system. Model calibration against seepage and water-travel-velocity data suggests that lithophysal cavities connected to fractures can considerably enhance the effective fracture porosity and therefore retard water flow in fractures. Comparisons between simulation results and tracer concentration data also indicate that matrix diffusion is an important mechanism for solute transport in unsaturated fractured rock. We found that an increased fault-matrix and fracture-matrix interface areas were needed to match the observed tracer data, which is consistent with previous studies. The study results suggest that the current site-scale model for the unsaturated zone of Yucca Mountain may underestimate radionuclide transport time within the unsaturated zone, because an increased fracture-matrix interface area and the increased effective fracture porosity arising from lithophysal cavities are not considered in the current site-scale model.

Biological Transport↗
PubMed2005

Commentary: assessment of past infiltration fluxes through Yucca Mountain on the basis of the secondary mineral record-is it a viable methodology?

Two papers recently published in the Journal of Contaminant Hydrology by Marshall et al. [Marshall, B.D., Neymark, L.A., Peterman, Z.E., 2003. Estimation of past seepage volumes from calcite distribution in the Topopah Spring Tuff, Yucca Mountain, Nevada. J. Contam. Hydrol. 62-63, 237-247] and Xu et al. [Xu, T., Sonnenthal, E., Bodvarsson, G., 2003. A reaction-transport model for calcite precipitation and evaluation of infiltration fluxes in unsaturated fractured rock. J. Contam. Hydrol. 64, 113-127] attempt to assess past volumes of seepage and infiltration fluxes through the vadose zone of Yucca Mountain, Nevada, on the basis of the modeling of the spatial distribution of secondary calcite. In this commentary, we argue that the employed methodology is not viable. In addition, the thermal boundary conditions used in simulations do not correspond to the temperatures of the mineral forming fluids established on the basis of the fluid inclusion studies.

Geological Phenomena↗
PubMed2005

Monitoring iodine-129 in air and milk samples collected near the Hanford Site: an investigation of historical iodine monitoring data.

While other research has reported on the concentrations of (129)I in the environment surrounding active nuclear fuel reprocessing facilities, there is a shortage of information regarding how the concentrations change once facilities close. At the Hanford Site, the Plutonium-Uranium Extraction (PUREX) chemical separation plant was operating between 1983 and 1990, during which time (129)I concentrations in air and milk were measured. After the cessation of chemical processing, plant emissions decreased 2.5 orders of magnitude over an 8-year period. An evaluation of (129)I and (127)I concentration data in air and milk spanning the PUREX operation and post-closure period was conducted to compare the changes in environmental levels. Measured concentrations over the monitoring period were below the levels that could result in a potential annual human dose greater than 1 mSv. There was a measurable difference in the measured air concentrations of (129)I at different distances from the source, indicating a distinct Hanford fingerprint. Correlations between stack emissions of (129)I and concentrations in air and milk indicate that atmospheric emissions were the major source of (129)I measured in environmental samples. The measured concentrations during PUREX operations were similar to observations made around a fuel reprocessing plant in Germany. After the PUREX Plant stopped operating, (129)I concentration measurements made upwind of Hanford were similar to the results from Seville, Spain.

Air Pollutants, Radioactive↗
PubMed2006

Anthropogenic radionuclides in sediment in the Japan Sea: distribution and transport processes of particulate radionuclides.

Distributions of anthropogenic radionuclides ((90)Sr, (137)Cs and (239+240)Pu) in seabed sediment in the Japan Sea were collected during the period 1998-2002. Concentration of (90)Sr, (137)Cs and (239+240)Pu in seabed sediment was 0.07-1.6 Bq kg(-1), 0.4-9.1 Bq kg(-1) and 0.002-1.9 Bq kg(-1), respectively. In the northern basin of the sea (Japan Basin), (239+240)Pu/(137)Cs ratios in seabed sediment were higher and their variation was smaller compared to that in the southeastern regions of the sea. The higher (239+240)Pu/(137)Cs ratios throughout the Japan Basin were considered to reflect production of Pu-enriched particles in the surface layer and substantial sinking of particulate materials in this region. In the southern regions of the Japan Sea (<38 degrees N), both inventories and (239+240)Pu/(137)Cs ratios in sediment were larger than those in the other regions. In the southern Japan Sea, observations suggested that supply of particulate radionuclides by the Tsushima Warm Current mainly enhanced accumulation of the radionuclides in this region.

Cesium Radioisotopes↗
PubMed2005

Preparation of TiO2-SiO2 mixed gel spheres for strontium adsorption.

A simple external gelation process, taking full advantage of the gelation features of titanium and silica, was developed to prepare TiO2-SiO2 mixed gel spheres suitable for strontium adsorption. The source solutions used for the process were prepared from different mixtures of 1M TiCl4 and 1M Na2SiO3 solutions and converted into droplets in a gelation column. The suitable spheres for strontium adsorption were obtained using a hexone (methyl isobutyl ketone) solution as the drop formation medium and ammonia as the gelling agent. The mixed oxide gels were identified and characterized by DTA/TGA, FTIR and XRD analysis. The parameters affecting the strontium adsorption, such as weight ratio of TiO2, pH, temperature, shaking time and selectivity towards competing ions were investigated. Sorption data have been interpreted in terms of Freundlich, Langmuir and Dubinin-Radushkevich equations. Thermodynamic parameters for the sorption system have been determined at four different temperatures. The value of DeltaH degrees =39.553 kJ/mol and DeltaG degrees =-16.687 kJ/mol at 296 K prove that the sorption of strontium on mixed oxide gel is an endothermic and a spontaneous process.

Adsorption↗
PubMed2005

Experimental determination of the minimum onset temperature of runaway reaction from a radioactive salt disposal in asphalt.

In order to clarify the reason for the most hazardous explosion in the history of the Japanese nuclear power development by a radioactive salt disposal in asphalt, an adiabatic process was developed using a Dewar vessel to minimize the temperature difference between the reactants and the surroundings. By this means, the heat evolution from a reaction which is readily lost can be detected at a lower temperature imitating the accidental condition. A series of ambient temperature-tracking Dewar experiments on asphalt salt mixtures were conducted under different initial ambient temperatures, such as 230, 210, 190, and 170 degrees C, respectively. As a result, it was observed that from 190 degrees C the sample's temperature rose until a runaway reaction occurred. The minimum onset temperature for the runaway reaction of the asphalt salt mixture was determined to be 190 degrees C, which is close to the initial temperature of approximately 180 degrees C, the same temperature as the real accident. This implies that at near this operational temperature, initial faint chemical reactions may occur and lead to further rapid reactions if heat is accumulated at this stage.

Explosions↗