Fallout, atmospheric, from nuclear

The major source of plutonium in natural waters is the atmospheric fallout from nuclear weapons tests. Fallout plutonium is ubiquitous in marine and freshwater environments of the world with higher concentrations in the northern hemisphere where the bulk of nuclear weapons testing occurred(3). Much of the research on the aquatic chemistry of plutonium takes place in marine and freshwater systems where only fallout is present. 

Atmospheric fallout from nuclear weapon tests and aquatic... 

Forms of silver in atmospheric emissions are probably silver sulfide, silver sulfate, silver carbonate, silver halides, and metallic silver (Smith and Carson 1977). About 50% of the silver released into the atmosphere from industrial operations is transported more than 100 km and is eventually deposited in precipitation (USPHS 1990). Minute amounts of 110mAg have been detected in natural waters and are attributed to atmospheric fallout from nuclear explosions (Smith and Carson 1977). 

About one-fifth of our annual exposure to radiation comes from nonnatural sources, primarily medical procedures. Television sets, fallout from nuclear testing, and the coal and nuclear power industries are minor but significant nonnatural sources. Interestingly, the coal industry far outranks the nuclear power industry as a source of radiation. The global combustion of coal annually releases into the atmosphere about 13,000 tons ol radioactive thorium and uranium. Worldwide, the nuclear power industries generate about 10,000 tons of radioactive waste each year. Most of this waste is contained, however, and is not released into the environment. As we explore in Chapter 19, where to bury this contained radioactive waste is a heated issue yet to be resolved. 

FALLOUT (Radioactive . The term fallout generally has been used to refer to particulate mutter that is thrown into the atmosphere by a nuclear process of short time duration. Primary examples are nuclear weapon debris and effluents from a nuclear reactor excursion. The name fallout is applied both to matter that is aloll and to matter that has been deposited on the surface of the earfh. Depending on the conditions of formation, this material ranges in texture from an aerosol to granules uf considerable size. The aerodynamic principles governing tls deposition are the same as for any Other material of comparable physical nature that is thrown into the air. such as volcanic ash or particles from chimneys. Therefore, many of the principles learned in. studies of fallout from nuclear weapons can be applied lo studies of other particulate pollution in the atmosphere. 

The instances described here indicate the important role of fluvial discharge in the secondary transport of atmospherically derived, highly adsorptive radionuclides in a river watershed. A particulate form of radionuclides associated with suspended solids in river water is especially important. It was shown that the form can account for 90% of the annual discharge of Cs (mainly from the fallout from nuclear weapon testing), as was observed in the Kuji River watershed. The importance of this mechanism has also been stressed by other researchers (e.g. Walling et al., 1989). 

In the past, radioanalytical chemistry laboratories processed samples resulting from monitoring nuclear weapons development facilities, fallout from nuclear weapon tests in the atmosphere, and nuclear power stations. At present, monitoring cleanup of former nuclear facilities is a major source of samples, and efforts are... 

The activity ratio Pu/ Pu varies depending on source term such as weapon plutonium, fallout from nuclear tests, the Chernobyl accident and releases from nuclear fuel reprocessing plants. The objective of this project was to investigate if there was any close fallout over Madagascar even if it was claimed that all Pu was evaporated in the upper atmosphere. 

Exposure of the general population to 241 Am via air, water, soil, and food are generally very low these background levels are a result of fallout from past atmospheric nuclear weapons tests. Since 1973, 241Am air concentrations have been less than 1 aCi/m3 (0.037 pBq/m3) and are continuing to decline (Bennett 1979). Levels around nuclear power plants are indistinguishable from fallout background (EPRI 1981). 

Caribou in northern Quebec contained up to 1129 Bq 137Cs/kg muscle FW in 1986/87, but only 10 to 15% of this amount originated from Chernobyl the remainder is attributed to fallout from earlier atmospheric nuclear tests (Crete et al. 1990). The maximum concentration of 137Cs in meat of caribou (Rangifer tarandus granti) from the Alaskan Porcupine herd after the Chernobyl accident did not exceed 232 Bq/kg FW, and this is substantially below the recommended level of 2260 Bq 137Cs/kg FW (Allaye-Chan et al. 1990). Radiocesium transfer in an Alaskan lichen-reindeer-wolf (Canis lupus) food chain has been estimated. If reindeer forage contained 100 Bq/kg DW in lichens and 5 Bq/kg DW in vascular plants, the maximum winter concentrations — at an effective half-life of 8.2 years in lichens and 2.0 years in vascular plants — were estimated at 20 Bq/kg FW in reindeer-caribou skeletal muscle and 24 Bq/kg FW in wolf muscle (Holleman et al. 1990). 

It has been estimated that 1.3 x 1016 Bq of 239+240 pu has been released to the environment from atmospheric detonation of nuclear weapons that 7.9 x 1014 Bq of 238Pu has been released, mosdy from bum-up of the nuclear powered satellite SNAP-9a and that 3.7 x 1013 Bq of 239+240 Pu was released by the Chernobyl accident (167,168). Many studies have been done to determine the cumulative fallout on soils, plants, bodies of water, animals, and humans. For example, the cumulative 239+240 pu fallout in forest and grasslands and in the liver of eldedy humans in Bavaria, Germany are approximately 50 Bq/m2 and 0.02 Bq/kg wet mass, respectively (167). 

C reaches the Earth s surface at the rate of 2.3 atoms/cm2/s after production by cosmic ray interaction in the atmosphere, corresponding to a total production of 1.4 x 1015Bq/y. 14C is also formed by the 14N(n, p) reaction by atmospheric tests of nuclear weapons. About 2.2 x 1017 Bq were made in the atmospheric test spike of the 1950s and 1960s that has been primarily transferred to the oceans and the biosphere. This means that 14C is the most significant fallout nuclide from the point of view of population dose. Nuclear power plants also release 14C as part of their normal operation contributing 0.1 x 1015 Bq/y. 

The biological effects of different radiation doses are given in Table 22.5. Although the effects sound fearful, the average radiation dose received annually by most people is only about 120 mrem. About 70% of this radiation comes from natural sources (rocks and cosmic rays) the remaining 30% comes from medical procedures such as X rays. The amount due to emissions from nuclear power plants and to fallout from atmospheric testing of nuclear weapons in the 1950s is barely detectable. 

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