Radioactive materials, atmosphere

Several modes of waste management are available. The simplest is to dilute and disperse. This practice is adequate for the release of small amounts of radioactive material to the atmosphere or to a large body of water. Noble gases and slightly contaminated water from reactor operation are eligible for such treatment. A second technique is to hold the material for decay. This is appHcable to radionucHdes of short half-life such as the medical isotope technetium-9 9m = 6 h), the concentration of which becomes negligible in a week s holding period. The third and most common approach to waste... 

Two accidents of vastly differing severity have occurred at nuclear power plants. On 28 March 1979, an accident occurred in the nuclear power plant at Three Mile Island, Pennsylvania, USA. The radiation was contained and the small amount released had negligible effects on the health of individuals at the plant. On 26 April 1986 an accident occurred in the nuclear power plant 10 miles from the city of Chernobyl, then part of the Soviet Union. The chain reaction in the radioactive core of one of the four reactors became uncontrolled. Steam pressure rose to dangerous levels there were several explosions and a subsequent fire took several hours to extinguish. Large amounts of radioactive material were scattered over a wide area and into the atmosphere (later descending in a dilute form in rain all over the world). 

The process at Three Mile Island involved nuclear fission and subsequent reactor cooling using circulating water. The primary water was kept under pressure to prevent boiling. Heat was transferred to a secondary water system that supplied power to a steam generator. Upon completion of this step, steam condensate was recovered and recycled. All radioactive materials, including primary water, were enclosed in a lined concrete containment building to prevent their escape to the atmosphere. 

VAC TRAX is an ex situ thermal desorption process that separates contaminants such as volatile organic compounds (VOCs), semivolatile organic compounds (SVOCs), polychlorinated biphenyls (PCBs), and radioactive materials from soils, sludges, and solid trash. This process can be applied to mixed and unmixed waste streams. Because the nitrogen atmosphere in which the process occurs is inert, no combustion of organic material takes place. 

Radioisotope thermoelectric generators (RTGs) are sometimes used as power sources for space systems. In April 1964, a United States RTG navigational satellite, SNAP 9A, reentered the atmosphere and burned up at high altitude over the Mozambique Channel, releasing 629 trillion becquerels (TBq), equivalent to 17,000 Ci, of Pu and 0.48 TBq of Pu (Whicker and Schultz 1982a Richmond 1989). In January 1978, a Soviet RTG satellite, Kosmos 954, reentered the atmosphere over Canada and spread radiouranium across parts of that country (Richmond 1989). The amount of radioactive materials in space applications is expected to increase (Richmond 1989). 

TU any of the less-understood phenomena leading to the observed fall-out distribution resulting from a nuclear explosion occur on a relatively short time scale (a few tens of seconds or less). These short term phenomena lead to an initial distribution of radioactive material referred to as the source term in a fallout study. Many predictive calculations are based on an assumed source term, which of necessity has been quite oversimplified. Two typical simplifications made for purposes of model development are (1) that the radiochemical composition of fallout is well defined and uniform (2) that the particles comprising the initial debris are uniform with respect to settling rate in the atmosphere. The latter assumption has received considerable attention elsewhere, notably in the work of Miller (2). However, the former assumption concerning the radiochemical uniformity of the debris has received far less systematic attention. 

The direct contamination of vegetation by deposition of radioactive material from the atmosphere onto above-ground organs is important under three main circumstances. Firstly, where a release of radionuclides occurs to atmosphere during routine discharges from nuclear installations in most cases such releases are effectively continuous, although spike releases can take place, such as during blow-down when... 

Bonka, H., Horn, M. (1983). in Transfer of Radioactive Materials in the Terrestrial Environment Subsequent to an Accidental Release to Atmosphere, CEC, Dublin, 11-13 April 1983, pp. 41 -77. 

Another safety feature is a system of high-efficiency filters through which all air leaving the building must pass. These filters are designed to trap microscopic particles of radioactive materials that might otherwise be vented to the atmosphere. Other specialized devices and systems have also been developed for dealing with other kinds of accidents in various parts of the power plant. 

The dilution in air due to the atmospheric dispersion of radioactive aerosols resulting from a release of radioactive material was modelled for positions along the centre line of the plume using the diffusion equation with a top hat distribution to account for the directional fluctuations in crosswinds ... 

Fig. 9.1. Simplified pathways between radioactive materials released to atmosphere and man.

This is the most serious accident in the history of the development of nuclear energy. It was caused by illegal operations. The reactor core was completely destroyed and about 50 MCi of noble gas was released in the first day, April 26th. Furthermore, about 50 MCi of other fission products were released into the atmospheric environment until May 6th. The radioactivity from Chernobyl was detected at many places in the northern hemisphere. A large area of Europe received significant surface deposition of radioactive materials such as l and Cs. 

The Chernobyl accident involved the largest short-term release from a single source of radioactive materials to the atmosphere ever recorded. Of the materials released from the reactor core, four elements have dominated the short-term and long-term radiological situation in the affected areas of the USSR iodine (primarily caesium ( Cs, Cs), strontium (primarily Sr) and plutonium ( Pu, " Pu). In addition, highly radioactive fuel fragments (hot particles) were released. 

Depending on its explosive yield, a nuclear test may introduce radioactive materials to various heights in the atmosphere. The lowest level of the atmosphere is the troposphere, in which turbulent air movements occur. In addition to prevailing horizontal winds, there is also considerable vertical motion as evidenced by clouds, rain and... 

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