Plutonium deposition

Plutonium, deposited on soil, moves downwards with a rate which depends on precipitation and soil properties. In dry, sandy areas, the downward rate may be 1 mm/year, while in rainy areas it may be 10 times higher (3). The rate is considerably reduced in clay soil. 

The pathway of plutonium dissolved in natural water, from a source such as a nuclear facility, to man, may be quite complicated. During the transport, the plutonium atoms encounter dissolved and particulate inorganic and organic matter, as well as minerals in rocks, sediment and soil, and living organisms which may metabolize the plutonium. Figure 1 depicts some of the more essential routes for plutonium between the point of emission and the plutonium consuming man. The overall effect of these pathways is that plutonium is slowly eliminated from the water, so that only a minor fraction of it reaches man. An example of this is that of the 4.2 tonnes of plutonium deposited on the earth after... 

Monomeric plutonium species deposited in the liver become concentrated in the liver ferritin, the principal iron repository (191). On analysis of plutonium deposition in bone a dichotomy becomes immediately apparent. Monomeric plutonium no longer follows an iron transport/deposition mechanism, for bone contains little or no iron complexed within the bone matrix. Calcium phosphate as a chromatographic media does, of course, retain iron. 

Bourlat et al. (1995) have presented results on the plutonium radioactivity levels in Mururoa lagoon water during the 1985-1991 period. The low radioactivity levels recorded, from 0.01 to 1.5 Bq/m are due to the slow solubilization of plutonium deposited in lagoon sediments following atmospheric experiments which took place from 1966 to 1974. The average concentrations of the lagoon water decrease from one year to the next. Since the Mururoa lagoon is open to the ocean, plutonium radioactivity traces are also detectable in the immediate vicinity of the atoll. 

The atmospheric nuclear tests which took place at the Mururoa Lagoon between 1966 and 1974 did not produce significant fallout on the emerged part of the atoll. The tests (three carried out on a barge) only affected the sediments at the bottom of the lagoon, especially in the area directly under the barge. In contrast, a few safety air tests that took place between 1966 and 1974 in the northern part of the atoll (between the Colette Motu and the Denise area) resulted in localised plutonium deposition on the coral bedrock. 

Studies in animals indicate that bone cancer is the most common form of malignancy induced by Pu-239 that has entered systemic circulation. The length of the latency period appears to depend on the amount of plutonium deposited in bone. Liver cancers have been observed in animals given Pu-239 injections, but they occur much less frequently than bone cancers. 

The results of the studies on the effect of silica particle size on sorption indicate that, in the range of silica diameter of 1.4 X 10 2 to 3.9 X 10 2 cm, there is very little difference in the final amount of plutonium sorbed, as shown in Table III, the total weight of silica being the same for each size fraction. The only differences lie in the surface density of the sorbed species and the rate at which the equilibrium was approached. As the surface area decreased (i.e., as the silica size increased), there was more plutonium deposited per unit area of surface. Also, the smaller size particles with the higher surface areas sorbed the plutonium at a faster rate. These results are difficult to interpret, except with the model of a limited number of sorbable species, all of which are taken up eventually by the silica. They would not, however, be consistent with the model of a limited number of sorbing sites. 

Health Effects Associated with Plutonium Deposition-Inhalation 2-2 Health Effects Associated With Plutonium Deposition - Oral... 

Health Effects Associated with Plutonium Deposition-Other Routes of Exposure 2 4 Existing Information on Health Effects of Plutonium... 

Persons with chronic obstructive lung diseases may be more susceptible to the toxic effects of inhaled plutonium. Based on results from studies in rats with pulmonary emphysema, plutonium deposition would be decreased in a person with pulmonary emphysema, but retention would be increased (Lundgren et al. 1981). Therefore, a greater radiation dose would be delivered to the lungs of a person with emphysema or other chronic obstructive lung diseases. 

Plutonium deposited on soil surfaces may be resuspended in the atmosphere especially in areas that have low soil moisture levels, such as the Nevada Test Site. In drier areas, the levels of ambient airborne dust are expected to be higher than in areas with normal rainfall (Harley 1980). The highest concentrations of plutonium are likely to be found in the fine silt-clay particle size range. Particles of this size tend to be transported the farthest distance by wind and water (WHO 1983). 

The isotope of plutonium inhaled will affect its behavior in the body. The bones and the liver are the primary organs for plutonium deposition following translocation in the body (ICRP 1982). However, Mclnroy et al. (1989) indicate that muscle tissue may also be a site of deposition. Plutonium-238 dioxide is more rapidly translocated from the lungs than plutonium-239 dioxide thereby causing more plutonium-238 to be concentrated in other body tissues (ICRP 1982). 

Craig D, Mahlum D, Klepper E. 1974. The relative quantity of airborne plutonium deposited in the respiratory tract and on the skin of rats. BNWL-SA-4867. Battelle Pacific Northwest Laboratory, Richland, WA. NTIS no. CONF-740702-1. 

R.A. (1995) Annihilation of plutonium in CANDU reactors. Proceedings, IAEA Technical Communications Meeting Unconventional Options for Plutonium Deposition, IAEA-TECDOC-840, p. 103. 

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