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Plutonium normally has six allotropes and forms a seventh (zeta, ζ) at high temperature within a limited pressure range. [17] These allotropes, which are different structural modifications or forms of an element, have very similar internal energies but significantly varying densities and crystal structures .
The odd numbered fissile plutonium isotopes present in spent nuclear fuel, such as Pu-239, decrease significantly as a percentage of the total composition of all plutonium isotopes (which was 1.11% in the first example above) as higher and higher burnups take place, while the even numbered non-fissile plutonium isotopes (e.g. Pu-238, Pu-240 and ...
Plutonium in the delta (δ) phase [7] normally exists in the 310 °C to 452 °C range but is stable at room temperature when alloyed with a small percentage of gallium, aluminium, or cerium, enhancing workability and allowing it to be welded in weapons applications. The δ phase has more typical metallic character and is roughly as strong and ...
As plutonium cools, changes in phase result in distortion and cracking. This distortion is normally overcome by alloying it with 3–3.5 molar% (0.9–1.0% by weight) gallium, forming a plutonium-gallium alloy, which causes it to take up its delta phase over a wide temperature range. [39]
As plutonium cools, changes in phase result in distortion and cracking. This distortion is normally overcome by alloying it with 30–35 mMol (0.9–1.0% by weight) gallium, forming a plutonium-gallium alloy, which causes it to take up its delta phase over a wide temperature range. [21]
The δ phase is the least dense and most easily machinable. It is formed at temperatures of 310–452 °C at ambient pressure (1 atmosphere), and is thermodynamically unstable at lower temperatures. However, plutonium can be stabilized in the δ phase by alloying it with a small amount of another metal.
By heating it, the metallurgists discovered five temperatures between 137 and 580 °C (279 and 1,076 °F) at which it suddenly started absorbing heat without increasing in temperature. This was a strong indication of multiple allotropes of plutonium ; but was initially considered too bizarre to be true.
a = 0.6183 nm b = 0.4822 nm c = 1.0964 nm β = 101.79° (at 20 °C) [1] Thermal expansion: 49.6 × 10 −6 /K (at 20 °C) [1]: Thermal conductivity: 6.74 W/(m⋅K) ...