Radioactive materials decontamination

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. 

Protective equipment goggles and gloves, acid-proof clothing, face masks and respirators, lifelines, eye-wash fountains, flooding showers. For hot labs and plants handling radioactive materials decontamination equipment, glove boxes, and remote-control devices. 

Countries and groups that lack access to nuclear weapons may still have opportunities to obtain radioactive materials such as spent nuclear fuel. A bomb in which a conventional explosive charge causes dispersal of radioactive material is known as a dirty bomb. Such a device could result in psychological effects exceeding the physical damage it caused. Once again, new techniques are needed for detection (of both the explosive and radioactive material), and decontamination procedures would be essential if such a device were used. 

The use of radiation dispersal devices, commonly referred to as dirty bombs, is particularly concerning for disaster planning and emergency preparedness personnel. An RDD is an explosive device designed to spread radioactive material without a nuclear explosion (Briggs Brinsfield, 2003). The initial blast from the explosion can kill or inflict mechanical trauma on those who are close in proximity to the explosion while the radioactive material is dispersed. Please refer to chapter 27, Radiological Incidents and Emergencies, for further information on decontamination, radiation sickness, and personal protective measures. 

It is important to distinguish between radiation and radioactive contamination. Radiation is energy emitted by atoms that are unstable. Radiation travels through space to some extent—some kinds of radiation can only travel a few millimeters, whereas other types can travel for many meters. Radioactive contamination is the presence of radiation-emitting substances (radioactive materials or RAM) in a place where it is not desired. A patient may be contaminated with radioactive materials, but that patient will not be inherently radioactive and can be decontaminated. Radioactive materials, by comparison, are inherently radioactive—it is a physical property of that material in the same manner as mass or size—and they remain radioactive until they decay to stability. 

After safely finding shelter, anyone who might have been exposed to the radioactive material should begin to decontaminate themselves immediately. As... 

External radiation (irradiation) because radioactive material is not deposited on or in the body, decontamination is not necessary... 

In the Aquafluor process [G4] developed by the General Electric Company, most of the plutonium and fission products in irradiated light-water reactor (LWR) fuel are separated from uranium by aqueous solvent extraction and anion exchange. Final uranium separation and purification is by conversion of impure uranyl nitrate to UFg, followed by removal of small amounts of PuF , NpFg, and other volatile fluorides by adsorption on beds of NaF and Mgp2 and a final fractional distillation. A plant to process 1 MT/day of irradiated low-enriched uranium fuel was built at Morris, Illinois, but was never used for irradiated fuel because of inability to maintain on-stream, continuous operation even in runs on unirradiated fuel. The difficulties at the Morris plant are considered more the fault of design details than inherent in the process. They are attributed to the attempt to carry out aqueous primary decontamination, denitration, fluorination, and distillation of intensely radioactive materials in a close-coupled, continuous process, without adequate surge capacity between the different steps and without sufficient spare, readily maintainable equipment [G5, R8]. 

Evaporators coupled to efficient deentrainment devices provide capability for a high degree of separation for most radioactive materials. The inherently high operating cost of evaporation limits its application to those liquids that have a high concentration of dissolved solids and require high decontamination factors. 

A filtered air supply should maintain a positive pressure relative to surrounding areas under ail operational conditions and flush the area effectively. Moreover, particular attention should be paid to the protection of the zone of greatest risk, that is, the immediate environment to which the product and the cleaned components in contact with it are exposed. The various recommendations regarding air supplies and pressure differentials may need to be modified if it becomes necessary to contain materials such as pathogenic, highly toxic, radioactive, or live viral or bacterial materials. Decontamination faalities and the treatment of air leaving a dean area may be necessary for some operations. 

Routes of entry for radioactive materials are much the same as for poisons. However, the radioactive source or material does not have to be directly contacted for radiation exposure to occur. Exposure occurs from the radiation being emitted from the radioactive source. Once a particulate radioactive material enters the body, it is dangerous because the source now becomes an internal source rather than an external one. You cannot protect yourself by time, distance, or shielding from a source that is inside your body. Contact with or ingestion of a radioactive material does not make you radioactive. Contamination occurs with radioactive particles, but with proper decontamination, these can be successfully removed. After they are removed, they cannot cause any further damage to the body. 

Advising state and local health departments on how to protect people, animals, and food and water supplies from contamination by radioactive materials Providing technical assistance and consultation to state and local health departments on medical treatment, follow-up, and decontamination of victims exposed to radioactive materials Establishing and maintaining a registry of people exposed to or contaminated by radioactive materials... 

Management of a radiation accident depends on whether the victim has been contaminated or only irradiated. Irradiated victims pose no threat to health-care providers and may be managed with no special precautions. On the other hand, contaminated victims must be decontaminated to prevent spread of radioactive materials to others and the environment. 

The principal parameter for decontamination of liquid effluent from the pressurized water reactor by RO and UF is the decontamination factor (DF), which is the ratio of the amount of nuclides in the inlet stream (specified in terms of the concentration or activity of radioactive materials) to the amount of nuclides in the effluent stream following RO or UF treatment. According to the Gaseous... 

When using radioactive materials or perhaps some unusually toxic materials, where it would be necessary to decontaminate the work surface after a spUl, the choice clearly should be limited to those materials such as stainless steel that are least likely to absorb materials. However, if the use of such materials is rninimal and limited to very low levels of activity or concentrations (as it should be when used on an open bench), the work surface can be protected with an absorbent paper with a chemically resistant backing. The higher cost of the premium materials could be avoided if the need does not otherwise exist. 

Reactor Decontamination and Decommissioning. Design of the areas to which access is required in the reactor facility that may become contaminated with radioactive materials under normal or abnormal operating conditions shall incorporate measures to simplify decontamination and to facilitate decontamination for... 

Conveyances may become contaminated during the carriage of radioactive material by the non-fixed contamination on the packages. If the conveyance has become contaminated above this level, it should be decontaminated to at least the appropriate limit. This provision does not apply to the internal surfaces of a conveyance provided that the conveyance remains dedicated to the transport of radioactive material or surface contaminated objects under exclusive use (see para. 514.1). 

Some simple operational improvements can also help minimize mixed waste. Surpluses can be minimized by limiting the acquisition of chemicals and radioactive materials to immediate needs. Contaminated equipment can sometimes be reused within restricted areas or decontaminated. Establishing procedures for noncontaminated materials can enable generators to keep normal trash separate from contaminated waste. 

Contaminated wastes derive from the fabrication of weapon components and related activities also. Further, the end of Cold War resulted in closing weapons production facilities and the creation of decontamination products, surplus plutonium, and other radioactive materials. These materials have to be safely disposed so that they do not cause any harm to public health or the environment. Moreover, they have to be secured so that they carmot be easily recovered and reused. 

RDDs using explosives present the same dangers as any other explosion (see Chapter 6), plus the dispersal of radioactive material. Depending upon the amount of explosive, the type and physical state of the radioactive materials, winds, and prevailing weather, a RDD might contaminate a large area, especially downwind from the site. Whenever possible, you should approach explosion sites from upwind. Contamination can be a long-lived event, and it can require both extensive and expensive decontamination efforts. 

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