Plutonium mass number range

Plutonium Pu 94 artificial isotopes only mass number range 234-246... 

Their work as part of the Manhattan Project was kept secret and was finally reported in 1946, after World War II, although the existence of plutonium had been revealed to the world earlier, when the atomic bomb was dropped over Nagasaki, Japan. There are sixteen isotopes of plutonium, having mass numbers ranging from 232 to 247. The principal isotopes of Pu are those having mass numbers 238, 239, 240, 241, 242, and 244. Ton quantities of Tu (having a half-life of 2. 4 X 0 y) are available. The isotope Tu is the source material for nuclear weapons and is produced via neu-... 

The critical masses reported here are of interest since, owing to handling difficulties, only a limited number of plutonium-metal critical mass measurements have been reported. Specific conclusions include the critical masses of steel-oil reflected assemblies are increased, relative to oil-only reflection the curve of critical mass variation with steel thickness, for steel-< reflection of hemispherical asseinblies, shows structure, which is similar to that found in previous enriched-uran-lum metal measurements on spherical assemblies. The structure observed consists of a pair of inflectlan points at steel thicknesses of 2 and cm together with a maximum at 3 cm. This structure has been shown to a be associated with the scattering resonances of Fein the energy range 20 to 100 keV. 

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