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PubMed2005

Retention and phytoavailability of radioniobium in soils.

Radioniobium is present in long-lived nuclear waste as a result of the activation of zirconium pellets associated with the nuclear fuel. The behaviour of niobium (Nb) in the environment and especially its fate in the soil-plant system has not been thoroughly investigated so far. In safety assessment of French long-lived nuclear waste disposal, data concerning the mobility and the bioavailability of Nb in soils are needed as well as general trends of its fate in the specific environment around the site of French underground research laboratory. Therefore, we investigated the mobility of 95Nb in three different soils typical of the area of north-eastern France and its uptake by two plants, rye grass (Lolium perenne L.) and winter wheat (Triticum aestivum L.). Soil:solution distribution of 95Nb was observed in 1:10 batch experiments with deionized water for a 3-day period. Results showed that K(d) values were high (in the order of 10(3) L kg(-1)) and were still significantly increasing after 3 days. A mathematical model, fitted to describe the decrease of the radioactivity after 3 days, is proposed to calculate sorption ratios--SR--(rather than K(d) values as equilibrium was not reached) over longer periods. Soil-to-plant concentration ratios (CR) were measured in shoots and roots of the two plants after cultivation on two soils spiked with (95)Nb (406kBqkg(-1)). Soil-to-root dry weight CR were high (0.30-1.52) and could probably be due to efficient uptake into the roots. However, no transfer of Nb to plant shoots was detected in any of the soils. Nb is thus a rather immobile element in soils and its transfer to plants seems limited to underground parts. It would therefore tend to accumulate in surface horizons of soils in case of long-term continuous surface release.

Biological Availability↗
PubMed1981

Areawide chemical contamination. Lessons from case histories.

Nine case histories illustrate the mounting problems owing to chemical contamination that often extends beyond the workplace into the community. The effects include not only carcinogenesis and teratogenesis, so much in the public's mind, but also severe neurological and gonadal disabilities immediately after exposure. Recognition of causal relationships is often made by astute clinicians. The experience of the Atomic Bomb Casualty Commission in studying Japanese survivors in Hiroshima and Nagasaki serves as a model for future studies of communities exposed to unusual environmental contamination.

Adult↗
PubMed2002

Element mobility during metasomatism of granitic rocks in the Saint-Chély d'Apcher area (Lozère, France).

This paper summarises the behaviour of major and trace elements during hydrothermal alteration processes in the Vareilles albite deposit, Saint-Chély d' Apcher area (Lozère, France). Sampling focused mainly on fine- to medium-grained two-mica granite facies surrounding albitite veins in two open pits. The primary chemical variability inherent in sampling parent rock and analytical uncertainties can seriously affect element mobility calculations. Here we present a simple model that allows to discriminate between magmatic and alteration effects and to make a proper evaluation of the chemical changes that have caused the alteration. For this reason, a range of unaltered granites and albitites were sampled to evaluate the degree of parent rock heterogeneity. Duplicate measurements were performed by epithermal neutron activation analysis (ENAA) to obtain a reliable mean concentration for trace elements and to evaluate results reproducibility. ENAA measurements are completed by analysis of major elements by inductively coupled plasma-mass spectrometry (ICP-MS). The enrichment or depletion of an element during alteration, relative to its concentration in fresh parent rock, can be calculated on the basis of the assumed immobility of some elements during the process. In this study, we have assumed Ta as immobile element on the basis for his inert behaviour. The distinct differences in chemical change between altered and unaltered granite suggest the need to consider alteration event as an important parameter in evaluating granitic rocks for nuclear waste disposal.

Environmental Monitoring↗
PubMed2000

Characterization of subterranean bacteria in the Hungarian Upper Permian Siltstone (Aleurolite) Formation.

The main purpose of this work was to study the microbiology of the Hungarian Upper Permian Siltstone (Aleurolite) Formation, to assess the safety of future underground repositories for nuclear waste. Sixty-seven air, groundwater, technical water, rock, and surface samples were collected aseptically from different depths. The number of aerobic and anaerobic isolates was 277. The mesophilic minimum and maximum CFU counts of the air samples were 1.07-5.84 x 10(2).mL-1 (aerobic) and 0.22-1.04 x 10(2).mL-1 (anaerobic), respectively; those of the water samples were 0.39-1.25 x 10(5).mL-1 (aerobic) and 0.36-3.9 x 10(3).mL-1 (anaerobic); those of the technical water samples were 0.27-5.03 x 10(6).mL-1 (aerobic) and 4 x 10(5)-->10(6).mL-1 (anaerobic); and those of the aleurolite samples were 2.32 x 10(2)-2.47 x 10(5).g-1 (aerobic) and 0.45-9.5 x 10(2).g-1 (anaerobic). In the groundwater, the thermophilic aerobic bacteria count was 0-2.4 x 10(2).mL-1 and the thermophilic anaerobic bacteria count was 0.43-4.6 x 10(4).mL-1. The gases produced by the 16 gas-forming isolates were CO2 (aerobic isolates), and CO2 and H2 (anaerobic isolates). About 20% of the aerobic isolates produced siderophores. The proportions of organic acid producers were lowest in aerobic and anaerobic isolates from the aleurolite, 13% and 14%, respectively. The highest proportions of acid producers in the aerobic and anaerobic isolates from the air samples were 63% and 54%. Altogether 160 of the aerobic isolates and 52 of the anaerobic isolates were spore formers. The radiosensitivity of the aerobic isolates was also determined; the D10 values of the sporeformers ranged between 0.8-2.44 kGy. Our results indicate that the sulfate-reducing bacteria and the production of complexing agents (siderophores) may contribute to the mobilization of radionuclides from underground repositories. As well, microbial gas production can influence the environmental conditions. The variability in bacterial radiotolerance indicates the biodiversity at this potential disposal site. These facts must be considered during the planning of a nuclear waste repository.

Air Microbiology↗
PubMed2005

The use of a high-FeO olivine rock as a redox buffer in a nuclear waste repository.

Due to the higher stability of the spent nuclear fuel (mainly composed of UO2) under reducing conditions, and in order to enhance the retention/retardation of some key radionuclides, the olivine rock from the Lovasjärvi intrusion has been proposed as a potential redox-active backfill-additive in deep high-level nuclear waste (HLNW) repositories. In this work, two different approaches have been undertaken in order to establish the redox buffer capacity of olivine rock: (1) The capacity of the rock to respond to changes in pH or pe has been demonstrated and the final (pH, pe) coordinates agree with the control exerted by the system Fe(II)/Fe(III). (2) The rate of consumption of oxygen has been determined at different pH values. These rates are higher than the ones reported in the literature for other solids, what would point to the possibility of using this rock as an additive to the backfill material in a HLNW.

Buffers↗
PubMed2004

Spectroscopic and diffraction study of uranium speciation in contaminated vadose zone sediments from the Hanford site, Washington state.

Contamination of vadose zone sediments under tank BX-102 at the Hanford site, Washington, resulted from the accidental release of 7-8 metric tons of uranium dissolved in caustic aqueous sludge in 1951. We have applied synchrotron-based X-ray spectroscopic and diffraction techniques to characterize the speciation of uranium in samples of these contaminated sediments. UIII-edge X-ray absorption fine structure (XAFS) spectroscopic studies demonstrate that uranium occurs predominantly as a uranium(VI) silicate from the uranophane group of minerals. XAFS cannot distinguish between the members of this mineral group due to the near identical local coordination environments of uranium in these phases. However, these phases differ crystallographically, and can be distinguished using X-ray diffraction (XRD) methods. As the concentration of uranium was too low for conventional XRD to detect these phases, X-ray microdiffraction (microXRD) was used to collect diffraction patterns on approximately 20 microm diameter areas of localized high uranium concentration found using microscanning X-ray fluorescence (microSXRF). Only sodium boltwoodite, Na(UO2)(SiO3OH) x 1.5H20, was observed; no other uranophane group minerals were present. Sodium boltwoodite formation has effectively sequestered uranium in these sediments under the current geochemical and hydrologic conditions. Attempts to remediate the uranium contamination will likely face significant difficulties because of the speciation and distribution of uranium in the sediments.

Environmental Pollutants↗
PubMed2004

Creating a baseline radiological standard for the waste isolation pilot plant underground.

The Waste Isolation Pilot Plant (WIPP) is a deep underground geological repository for defense transuranic wastes. The creation of a full baseline radiological standard for the WIPP underground is essential in order to evaluate and account for the influence of the naturally occurring radioactive materials, and to prepare for any suspected contamination or the very unlikely event of a real accident scenario. In this report, we describe the establishment of the baseline information using the gamma background dose rate measurements and the salt rib smears of surface removable alpha and beta activities throughout the WIPP underground. The average background gamma dose rate in the WIPP underground is 8.27 x 10(-9) +/- 1.65 x 10(-9) Gy/h while the gamma dose rate on the WIPP surface is 3.46 x 10(-8) +/- 1.65 x 10(-9) Gy/h. The overall surface average alpha activity in the underground is 8.52 x 10(-5) +/- 1.22 x 10(-4) Bq/cm2 (at 1sigma level) with the minimum detectable activity (MDA) of 4.81 x 10(-4) Bq/cm2. The overall surface average beta activity is 8.25 x 10(-4) +/- 8.17 x 10(-4) Bq/cm2 (at 1sigma level) with the MDA of 3.19 x 10(-3) Bq/cm2. This baseline standard will be beneficial to the overall WIPP operational facility, ensuring the worker safety and adding to public confidence in the operation of the WIPP.

Beta Particles↗
PubMed1998

The effect of growth conditions on the biodegradation of tributyl phosphate and potential for the remediation of acid mine drainage waters by a naturally-occurring mixed microbial culture.

The biodegradation of tributyl phosphate (Bu3-P, TBP), releasing phosphate at a high enough concentration locally to precipitate uranium from solution, was demonstrated by a mixed culture consisting primarily of pseudomonads. The effect of various parameters on Bu3-P biodegradation by growing cells is described. Growth at the expense of Bu3-P as the carbon and phosphorus source occurred over a pH range from 6.5 to 8, and optimally at pH 7. Bu3-P biodegradation was optimal at 30 degrees C, reduced at 20 degrees C and negligible at 4 degrees C and 37 degrees C. Incorporation of Cu or Cd inhibited, and Ni, Co and Mn reduced its degradation. Inorganic phosphate (above 10 mM) and kerosene (up to 1 g/l) reduced Bu3-P biodegradation significantly, but nitrate had no effect. Sulphate (10-100 mM) was inhibitory. When pregrown biomass was used the fastest rates of tributyl and dibutyl phosphate biodegradation were 25 mumol h-1 mg protein-1 and 37 mumol h-1 mg protein-1 respectively. Microcarrier-immobilised biomass decontaminated uranium-bearing acid mine waste water by uranium phosphate precipitation at the expense of Bu3-P hydrolysis in the presence of 35 mM SO(4)2-. At pH 4.5, 79% of the UO2(2)+ was removed at a flow rate of 1.4 ml/h on a 7-ml.test column.

Anions↗
PubMed2001

Bacterial diversity in soil samples from two uranium waste piles as determined by rep-APD, RISA and 16S rDNA retrieval.

The bacterial diversity in two uranium waste piles was studied. Total DNA was recovered from a large number of soil samples collected from different sites and depths in the piles using two procedures for direct lysis. Significant differences in the bacterial composition of the samples were revealed by the use of rep-APD, RISA and 16S ARDREA. The 16S rDNA analyses showed that the uranium wastes were dominated by Acidithiobacillusferrooxidans and by several Pseudomonas species classified in the gamma-subdivision of the Proteobacteria. The three kinds of A. ferrooxidans 16S and IGS rDNA specific fragments that were found corresponded to the three phylogenetic groups recognised in this species. This microdiversity probably reflects the genetic adaptation of the uranium waste strains to different concentrations of heavy metals.

Base Sequence↗
PubMed1997

Potential effects of climatic change on radiological doses from disposal of Canadian nuclear fuel waste.

The environmental assessment of deep geologic disposal of Canadian nuclear fuel waste considers many processes that could affect radionuclide transport to humans over thousands of years. Climatic change is an important feature that will occur over these long times. Glaciation will likely occur within the next 100,000 years over much of Canada, and its impact on radiological doses has been assessed previously. In the present study, we investigate the potential effect of short-term climatic change, usually associated with global warming caused by increases in atmospheric trace gases. We study the main biosphere transport pathways causing a radiological dose to humans from 129I, which is the most important radionuclide in disposal of Canadian used nuclear fuel. Irrigation of a garden with contaminated well water is the main pathway and it can be affected by changes in temperature and precipitation. A cold, wet climate decreases the need for irrigation, and this decreases the radiological dose. A drastic climatic change, such as an increase in temperature from 10 to 20 degrees C and decrease in precipitation from 0.3 to 0.2 m during the growing season, is estimated to increase the dose by a factor of four. This is a relatively small change compared to the range of doses that arise from the variability and uncertainty in many of the parameters used in the environmental assessment models. Therefore, it is likely that the results of probabilistic dose assessment models can include the consequences of short-term climatic change.

Agriculture↗
PubMed2005

Assessment of actinide mass embedded in large concrete waste packages by photon interrogation and photofission.

This paper describes a method based on photofission developed in our laboratory to characterize in depth large waste packages. The method consists in using photons of high-energy (Bremsstrahlung radiation) in order to induce reactions of photofission on the heavy nuclei present in the wastes. The measurement of the delayed neutrons allows quantifying the actinides in the wastes. We present the first results of measurement performed with a concrete mock-up of 870l and two real waste packages.

Actinoid Series Elements↗
PubMedDate not supplied

The plutonium problem: the Royal Society sits on the fence.

A recent Royal Society report, Management of Separated Plutonium, considers the production and disposal of plutonium from the spent fuel from civil and nuclear power reactors. It accepts the need for dealing with plutonium stocks because of the toxicity of the element and as it can be used to fabricate nuclear weapons, and expresses concern that it might be illicitly acquired by terrorists. It recommends an independent Government commission on the management of plutonium, and considers the various options for this. However, it does not analyse the arguments against plutonium as a reactor fuel, and underestimates the risks of diversion to nuclear weapons and nuclear terrorism. This paper reviews the options, and concludes that separated plutonium should be added to high-level waste, vitrified, and eventually buried in a deep geological repository.

Facility Regulation and Control↗