Contamination, radioactive limits

These systems have been operated in extremely low quality (and radioactivity contaminated) industrial environments for the past several years without any major equipment or component failures. Utilizing specialized operating/warm-up procedures, they have operated in low grade, out-of-doors, dust ridden, rain-soaked, industrial environments at temperature ranges which greatly exceed the original equipment manufacturers (OEM) specified limits. The systems have been successfully operated at ambient temperatures of minus 10 to plus 103 degrees Fahrenheit without any pre-mature or un-anticipated equipment failures. 

Nuclear utiUties have sharply reduced the volume of low level radioactive waste over the years. In addition to treating wastes, utiUties avoid contamination of bulk material by limiting the contact with radioactive materials. Decontamination of used equipment and materials is also carried out. For example, lead used for shielding can be successfully decontaminated and recycled using an abrasive mixture of low pressure air, water, and alumina. 

Isolation of radioactive wastes for long periods to allow adequate decay is sought by the use of multiple barriers. These include the waste form itself, the primary containers made of resistant materials, overpacks as secondary layers, buffer materials, concrete vaults, and finally the host rock or sod. Barriers limit water access to the waste and minimize contamination of water suppHes. The length of time wastes must remain secure is dependent on the regulatory limit of the maximum radiation exposure of individuals in the vicinity of the disposal site. 

Sorption can significantly diminish the mobility of certain dissolved components in solution, especially those present in minor amounts. Sorption, for example, may retard the spread of radionuclides near a radioactive waste repository or the migration of contaminants away from a polluting landfill (see Chapters 21 and 32). In acid mine drainages, ferric oxide sorbs heavy metals from surface water, helping limit their downstream movement (see Chapter 31). A geochemical model useful in investigating such cases must provide an accurate assessment of the effects of surface reactions. 

Radiolysis of water is, at least for today, inherently limited due to the use of radioactive materials by which the product stream could be contaminated by radioactive species. Consequently while... 

High concentration of nontargeted ionic contaminants may reduce the efficiency of the 3M Empore extraction disk. Due to the high loading capabilities of the Empore membranes, the radionuclide concentration on the filters must be monitored to ensure that the membranes do not exceed the limits for low-level radioactive waste. 

There are several limitations to the ACT DE CON process. The technology does not destroy or stabilize radioactive materials or heavy metals. An additional treatment step is required to stabilize the removed contaminants. 

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 ... 

Low-Level Waste Low-level waste (LLW) consists of contaminated dry trash, paper, plastics, protective clothing, organic liquids such as liquid scintillation samples, and the like. LLW is produced by any facility that handles radioactive materials such as nuclear power plants, medical facilities, colleges, and so forth. In the United States, commercial LLW is sent to one of three disposal sites (Barnwell, South Carolina, Richland, Washington, and Clive, Utah). Due to the limited size of these sites (and similar disposal sites through the world) and steeply escalating costs for waste disposal, the primary goal of LLW treatment prior to disposal is volume reduction, either by incineration or compaction, followed... 

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