Figure 2.3 Neutron Energy Spectra of Plutonium-Beryllium and Plutonium-Boron Neutron Sources Compared with a Fission Source

DOE-STD-1128-98

Figure 2.3 Neutron Energy Spectra of Plutonium-Beryllium and Plutonium-Boron Neutron

Sources Compared with a Fission Source

plutonium exists in the α phase, which has a triclinic structure with a

theoretical density of about 19.86 g/cm3. The dimensional stability of this

phase is aggravated by its high linear thermal expansion coefficient and its low

α β transition temperature. This transformation takes place at

approximately 115C, resulting in a 10% volume change. The combination of a

high specific activity and low thermal conductivity can result in significant

dimensional distortion during metal-forming operations. For this reason, a σ -

stabilized dilute gallium alloy, which has a density of about 15.75 g/cm3, is

used when a more dimensionally stable plutonium is desired (Merz, 1971).

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