Water contaminated with radionuclides

Although the process requires the addition of a phosphate donor, such as glycerol-2-phosphate, it may be a valuable tool for cleaning water contaminated with radionuclides. An alternative mode of uranium precipitation is driven by sulfate-reducing bacteria such as Desulfovibrio desutfuricansy which reduce U(VI) to insoluble U(IV). When combined with bicarbonate extraction of contaminated soil, this may provide an effective treatment for removing uranium from contaminated soil (85). 

Cornish, J. E., Huddleston, G. J., and Levine, R. S., 1995, Ph)4oremediation of soils and water contaminated with toxic elements and radionuclides. In 7 ACS Special Symposium Energing Technologies in Hazardous Waste Management, ed D.W. Tedder, American Chemical Society, Washington, DC, pp. 1352-1414. 

According to the vendor, the technology can be used to (1) remediate water and sludges contaminated with radionuclides and heavy metals, (2) restore gronndwater from mining operations, (3) treat naturally occurring radioactive materials (NORMs) in water or scale from petroleum operations, and (4) remediate man-made radionuclides stored in tanks, pits, barrels, or other containers. 

Fig. 7-2. Summary of environmental pathways by which terrestrial plants may become contaminated with radionuclides. In the case of an input from atmosphere, or as a result of the process of resuspension , any external radionuclide burden may be reduced by field loss mechanisms conversely, an initially external radionuclide deposit (Rat) may become internalised (i int) following foliar absorption and translocation. Radioactive contaminants of soils may be derived either from atmospheric inputs or from seepage in ground waters. Partitioning of radionuclides in soil—soil water systems controls their availability for root absorption, which normally occurs exclusively from the liquid phase. The chemical speciation of the nuclide in this phase, however, provides a further control on bioavailability which is highly radionuclide specific.

Water samples come either from surface or underground water sources. Surface water can be contaminated with radionuclides either during atmospheric precipitations or in the course of the surface flow. Underground water can be contaminated with radionuclides from waste materials stored under the earth s surface however, they may also contain natural radioactive compounds from their deposits. Some radioactive compounds are removed when surface water is conditioned for supply water however, the most dangerous long-lived radionuclides, such as °Sr and Cs, remain in the conditioned water. 

All of the above discussed radioactive contaminated media and waste could also contain non-radioactive environmental pollutants, e.g., boron and other water treatment chemicals in reactor coolant effluents. The mitigation measures taken to prevent release of radioactive pollutants into the environment will also mitigate the release of some non-radioactive pollutants. With regard to the identification of non-radioactive pollutants that could result in a major environmental accident, this section only considers the storage/use of substances that does not involve exposure to (and possible contamination with) radionuclides. 

Moore JW, Sutherland DJ. 1981. Distribution of heavy metals and radionuclides in sediments, water, and fish in an area of Great Bear Lake contaminated with mine wastes. Arch Environ Contam Toxicol 10 329-338. 

Electrokinetics is an in situ remediation technology applicable to soil or soil-like material with low hydraulic conductivities (e.g., clay) contaminated with heavy metals, radionuclides, and selected organic pollutants. The technique has been used in the past in the oil recovery industry and to remove water from soils. 

The availability of pure water will certainly be one of the major environmental issues of the 21s1 Century. Water contamination can originate from domestic, agricultural, agroindustrial or industrial activities, and accidental damages. The major pollutants are heavy metals, radionuclides, ammonia, nitrates and organic compounds. Health problems are associated with each of them, such as leukaemia, saturnism..., as well as modifications of the eco-system, e.g. entrophication of lakes and rivers. The nature of water treatments obviously depends on the kind of contaminants, and zeolite-based processes are of great concern in this field. 

Pentreath, R.J. The roles of food and water in the accumulation of radionuclides by marine teleost and elasmobranch fish, p. 421-436, Symp. Interaction of Radioactive Contaminants with the Constituents of the Marine Environment, Seattle, Washington, July 10-14, 1972. IAEA, Vienna, 1973. 

The pathways of radionuclides in ecosystems are illustrated schematically in Fig. 21.2. Plants may take up radionuclides from the air by deposition on the leaves, or from the soil by the roots with water and minerals. In this step, the species of the radionuclides and their solubility are most important. Microorganisms incorporate radionuclides present in water or in the soil. Animals and man may be contaminated by radionuclides from the air (gases, aerosols, dust) by inhalation or deposition on the skin, or by uptake of water and via the food chain by digestion. Animals may also be contaminated by ingestion of contaminated soil particles. 

Bioturbation in the upper layers of a cap can lead to rapid chemical migration. The normal feeding and burrowing activities of benthic organisms result in the rapid movement of particles and the contaminants with which they are associated, as well as the movement of porewater. The layer that is effectively mixed by organisms, hbio, is relatively small. More than 90% of the 240 observations of bioturbation mixing depths in fresh and salt water reported by Thoms [5] were 15 cm or less, and more than 80% were 10 cm or less. In freshwater systems, most measurements of mixing depth are of the order of 3-5 cm. Most of these measurements were based upon particle-associated radionuclides and the observed effective particle diffusion coefficients,... 

The coolants that come into contact with the nuclear areas of the reactor plants, primarily the PWR primary coolant and the BWR reactor water, are contaminated even during plant normal operation with radionuclides formed by various nuclear reactions. However, the appearance of these radionuclides in the coolants does not cause any difficulties in plant operation since all the relevant circuits are designed for safe operation in the presence of radioactivity. 

In the BWR plants, the out-of-RPV surfaces which are subject to contamination during steady-state operation are mainly those wetted by high-temperature reactor water. These are, in the main, the pipes leading to the reactor water cleanup system and the recirculation lines (as far as the plant is equipped with an external recirculation system). In addition to these surfaces, the main steam lines and the turbine, as well as part of the feedwater system, may be contaminated by radionuclides carried with the steam. In the course of a shutdown of the plant, certain regions of the main steam lines and of the feedwater lines are also in contact with low-temperature reactor water containing radionuclides. 

Because of the highly complex mechanisms of the production of corrosion product radionuclides and of contamination buildup, it cannot be expected that a single measure will result in an effective reduction of radiation levels. Rather a whole series of measures is necessary, aiming primarily at a reduction of the production, transport and deposition of Co, but in the second in an analogous reduction of the other corrosion product radionuclides. As can be concluded from the results discussed in the preceding sections, the dominant parameters responsible for contamination buildup are the concentration of dissolved Co in the reactor water and the readiness of the out-of-core oxide layers to incorporate Co from the reactor water. As with the PWR, in the BWR there are two possible main sources of corrosion product radionuclides the cobalt content of the in-core materials and the cobalt content in the corrosion products that are temporarily deposited on the surfaces of the fuel rods. Since the relative significance of these two mechanisms has not yet been analyzed to the same extent as in the PWR, the different measures taken up now have aimed at reducing both possible sources. 

Supporting monitoring programmes for sites contaminated with long lived radionuclides should be focused both on the terrestrial environment and on the description and habits of the population. The local water cycle should be monitored precipitation and evaporation, local surface waters and groundwaters and their connections, and inputs and outputs by main rivers. Characteristics of soils should be studied. The descriptions and distributions of... 

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