Fallout plutonium

Integral concentration over the entire fallout period is estimated to be 0.12 fCi-year/m3 (4.4 pBq-ycar/m3). Confirmation for these concentration estimates come from two sources comparison with plutonium fallout and cumulative deposits of241 Am activity in soil, which is a reflection of integral air concentrations. 

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. 

Plutonium (Pu) is an artificial element of atomic number 94 that has its main radioactive isotopes at 2 °Pu and Pu. The major sources of this element arise from the manufacture and detonation of nuclear weapons and from nuclear reactors. The fallout from detonations and discharges of nuclear waste are the major sources of plutonium contamination of the environment, where it is trapped in soils and plant or animal life. Since the contamination levels are generally very low, a sensitive technique is needed to estimate its concentration. However, not only the total amount can be estimated. Measurement of the isotope ratio provides information about its likely... 

Ayres, R. W. (1975). Policing plutonium the civil liberties fallout. Civil Liberties Law Review 10(2) 369-443. Bendocci, C. G. (1993). Women and Technology An Annotated Bibliography. New York Gareaud Publishing. Boyer, R. O., and Morals, II. M. (1955). Labor s Untold Stoiy. New York Cameron Assoc. 

Research into the aquatic chemistry of plutonium has produced information showing how this radioelement is mobilized and transported in the environment. Field studies revealed that the sorption of plutonium onto sediments is an equilibrium process which influences the concentration in natural waters. This equilibrium process is modified by the oxidation state of the soluble plutonium and by the presence of dissolved organic carbon (DOC). Higher concentrations of fallout plutonium in natural waters are associated with higher DOC. Laboratory experiments confirm the correlation. In waters low in DOC oxidized plutonium, Pu(V), is the dominant oxidation state while reduced plutonium, Pu(III+IV), is more prevalent where high concentrations of DOC exist. Laboratory and field experiments have provided some information on the possible chemical processes which lead to changes in the oxidation state of plutonium and to its complexation by natural ligands. 

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. 

Fallout plutonium arrives in natural waters either by direct atmospheric deposition or by erosion and/or dissolution from the land. Although in the past, this plutonium was considered to be in a refractory form due to formation within the fire ball, it seems more likely that most of the plutonium originated in the stratosphere by the decay of 239Np (from 239U formed during the detonation)(4). Deposition occurs predominantly with one or a few atoms incorporated in a raindrop. Investigations by Fukai indicate that collected rain contains soluble plutonium which has oxidation states that are almost totally Pu(V+VI)05). 

The results indicated certain correlations and generalities about plutonium that led to further questions regarding its chemical state in aquatic systems. For instance, the concentrations of fallout plutonium in natural waters was strongly dependent upon the concentration of DOC but no correlation to pH was obtained. 

In systems that receive only fallout plutonium, the lakes with... 

An interesting aspect of the characterization of plutonium as Pu(V) in the Irish Sea, Lake Michigan, and Pond 3513 is that the origins of the radionuclides are different in each system, i.e., fuel reprocessing waste, fallout, and laboratory effluents, respectively. 

The early field studies revealed that elevated concentrations of fallout plutonium correlated with Increased concentrations of dissolved organic carbon. Experiments at Argonne National Laboratory corroborate this correlation the explanation Is probably that the organic compounds complex Pu(IV), and, hence, decrease the distribution ratio between water and sedlments(27). In these experiments the distribution ratio (Kj) between sediment and natural waters was measured as a function of DOC. Measurements of Kj In both field and laboratory experiments show an unmistakable effect of DOC upon the distribution ratio. Figure 4 shows the Inverse correlation between the K, of plutonium and concentration of DOC. 

Half-lives span a very wide range (Table 17.5). Consider strontium-90, for which the half-life is 28 a. This nuclide is present in nuclear fallout, the fine dust that settles from clouds of airborne particles after the explosion of a nuclear bomb, and may also be present in the accidental release of radioactive materials into the air. Because it is chemically very similar to calcium, strontium may accompany that element through the environment and become incorporated into bones once there, it continues to emit radiation for many years. About 10 half-lives (for strontium-90, 280 a) must pass before the activity of a sample has fallen to 1/1000 of its initial value. Iodine-131, which was released in the accidental fire at the Chernobyl nuclear power plant, has a half-life of only 8.05 d, but it accumulates in the thyroid gland. Several cases of thyroid cancer have been linked to iodine-131 exposure from the accident. Plutonium-239 has a half-life of 24 ka (24000 years). Consequently, very long term storage facilities are required for plutonium waste, and land contaminated with plutonium cannot be inhabited again for thousands of years without expensive remediation efforts. 

Paatero J, Jaakkola T. 1998. Transfer of plutonium, americium and curium from fallout into reindeer after the Chernobyl accident. Boreal Environment Research 3 181-189. 

Unstable, silvery metal. The element was first discovered in the fallout from the first hydrogen bomb on the Bikini Atoll (1952), later produced by neutron bombardment of plutonium. Half-lives of the isotopes range from 20 to 401 days. "Relatively short-lived" in comparison to Einstein s formula E=m-c2, which is valid forever. Only of scientific interest. 

The plutonium concentration in marine samples is principally due to environmental pollution caused by fallout from nuclear explosions and is generally at very low levels [75]. Environmental samples also contain microtraces of natural a emitters (uranium, thorium, and their decay products) which complicate the plutonium determinations [76]. Methods for the determination of plutonium in marine samples must therefore be very sensitive and selective. The methods reported for the chemical separation of plutonium are based on ion exchange resins [76-80] or liquid-liquid extraction with tertiary amines [81], organophosphorus compounds [82,83], and ketones [84,85]. 

Testa and Staccioli [70] have pointed out that Microthene-710 (a micro-porous polyethylene) as a support material for triphenylphosphine oxide in cyclohexane medium has a potential application for the determination of plutonium in fallout samples. 

Carpenter R, Beasley TM, Zahnie D, et al. 1987. Cycling of fallout (plutonium, americium-241, cesium-137) and natural (uranium, thorium, lead-210) radionuclides in Washington continental slope sediments. Geochim Cosmochim Acta 51 1897-1921. 

Santschi PH, Li YH, Adler DM, et al. 1983. The relative mobility of natural (thorium, lead and polonium) and fallout (plutonium, americium, cesium) radionuclides in the coastal marine environment Results from model ecosystems (MERL) and Narragansett Bay. Geochim Cosmochim Acta 47 201-210. 

Michel, H., Barci-Funel, G., Dalmasso, J., Ardisson, G., Appleby, P. G Haworth, E. El-Daoushy, F. 2002. Plutonium and americium inventories in atmospheric fallout and sedimentary coves from Blelham Tarn, Cumbria, UK. Journal of Environmental Radioactivity, 59, 127-137. 

Montero, P. R. Sanchez, A. M. 2001. Plutonium contamination from accidental release or simply fallout study of soils at Palomares (Spain). Journal of Environmental Radioactivity, 55, 157-165. 

Numerous radionuclides have been applied to marine sedimentary problems. These are generally grouped into cosmic-ray produced (cos-mogenic) nuclides ( C, °Be, Be, "Al), nuclear bomb-produced (fallout) nuclides ( Cs, plutonium isotopes, 24iAm), and naturally occurring nuclides ultimately derived from the decay of 38u, and 232xh parents. 

The small number of atoms involved in some radiochemical procedures can alter the expected behavior. Although time-dependent processes obeying first-order kinetics are not changed by changes in concentration, the same is not true of second-order kinetics. For example, at 10-2 M, isotopic exchange between U(IV) and U(VI) has a lifetime of 2h, whereas at 10-10M, the same lifetime is 400 d. Another example is Np(V), which is unstable with respect to disproportionation and yet jjrCi / L solutions of NpOj are stable. The extreme dilution in some solutions can mean that equilibrium is not reached due to kinetic limitations. Fallout plutonium, present in the aqueous environment at concentrations of 10 18-10 17 M, has not reached equilibrium in over 40 y. 

---