Formation of plutonium aerosols

Plutonium is a man-made element, and only infinitesimal traces occur naturally. It melts at 641°C and boils at 3330°C. 239Pu is formed in nuclear reactors by neutron capture in 238U, followed by two successive beta decays (Fig. 5.1). Further neutron captures lead to 240Pu and 241 Pu. 238Pu is formed from 239Pu by (n,2n) reactions, or from 235U by three successive neutron captures and two beta decays. Table 5.1 shows the half-lives, alpha and X-ray energies of the principal Pu isotopes. 

Plutonium aerosols can be formed in various ways, including  

The particle size of Pu aerosols is very variable, depending on the mode of formation. In Fig. 5.2, curves A, B and C show size spectra obtained by Carter Stewart (1971) in laboratory experiments on the oxidation of Pu metal in air. In controlled oxidation at temperatures below the ignition point (about 500°C), scaly, friable, oxide particles were produced, with median diameter increasing with temperature. Few particles less than 1 jum in diameter were found. When the delta alloy of Pu was used, the oxide was more adherent, and the particle size larger. Increase of particle size with increase of temperature was also found in laboratory oxidation of uranium metal (Megaw et al., 1961), and was ascribed to sintering of the oxide layer. 

Quite different results were obtained when Pu metal was heated in argon above its melting point, and droplets of molten metal were 

Nuclide Half-life Specific activity (Cig-1) Particle energy (MeV) % X-ray (MeV) % 

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