Cleaning radioactive spills

Sediments in the Mississippi River were accidentally contaminated with a low-level radioactive waste material that leaked from a nuclear power plant on the river. Pore water concentrations of radioactive compounds were measured following the spill and found to be 10 g/m over a 2-mm depth. The water contamination was 30% radioactive cesium ( Cs), with a half-life of 30 years, and 70% radioactive cobalt ( °Co), with a half-life of 6 years. Objections by the local residents are preventing clean-up efforts because some professor at the local state university convinced them that dredging the sediments and placing them in a disposal facility downstream would expose the residents to still more radioactivity. The state has decided that the sediments should be capped with 10 cm of clay and needs a quick estimate of the diffusion of radioactive material through the clay cap (Figure E2.8.1). If the drinking water limit (10 g/m ) is reached at mid-depth in the cap, the state will increase its thickness. Will this occur ... 

Minor spills must be cleaned first with absorbent blotter paper and then thoroughly rinsed with water. Always wear gloves during cleanup. Dispose of the blotter paper in the Solid Radioactive Waste container. The spill area should then be checked with a portable G-M counter. 

Harmful chemical spills can often be cleaned up by treatment with another chemical. A spill of H2SO4, for example, can be neutralized by adding NaHC03. Why can t harmful radioactive wastes from nuclear power plants be cleaned up just as easily ... 

Confine your work with radioisotopes to a small area in the laboratory. A convenient plan is to use a stainless steel tray lined with absorbent blotter paper coated on the bottom side with polyethylene. The paper must be replaced every day. If the radioactive matenals are volatile, the work should be done in a fume hood. If spills occur, a small work area such as a tray is much easier to clean than a large lab bench. If or other strong j8 emitter is used, it is necessary to work at all times with shielding between yourself and the radioactive samples. The most cost-effective and convenient shielding material is Plexiglas. The thicknesses of shielding required for various materials are given in Table 6.3. 

For radio-tracer work in common non-nuclear research laboratories, some g ieral rules can be recommraded (see also next section). Spills may result in increase in the radiation background. They may not constitute a hazard to the workers, but may ruin the scientific experiments if not cleaned up immediately. In all work with radionuclides, radioactive waste is produced. It is common practice to collect all such waste in special containers, and to dispose of it according to national rules. For short lived radionuclides of low hazard and low levels of radioactivity (e.g. as in C-work), it is common practice to dispose of such waste by normal flushing to the sewer with several liters of tap water if such procedures are permitted by the national radiation protection organizations. 

Research projects in sanitary engineering include seeking processes and equipment for improved purification efficiency. One example is the development of large, portable water-treatment systems that are suitable for providing clean water to survivors of natural disasters and the bivouac medical units that treat them. Another example is a nanofiltration system that desalinates ocean water for use on naval ships, especially during times of conflict, and extended private offshore operations such as oil drilling. A related nanofiltration system is necessary for oil-spill cleanup. A third example is the specialized absorbent removal of microcontaminants that may be present in small yet detrimental amounts. These may include elements such as arsenic and lead, industrial solvents, and radioactive particles. 

Commercially available spill-control products are stocked by major scientific supply vendors and by safety product supply companies. Assortments of different sizes of the spill-control pillows, together with a selection of related products, should be kept in locations convenient to the laboratories and should be replaced when used. These products can be useful for cleaning up a biological agent spill after decontamination or spills of radioactive liquids. One kit may serve several laboratories. Thus a small investment may prove to be a wise step. 

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