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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 autoignition temperature or self-ignition temperature, often called spontaneous ignition temperature or minimum ignition temperature (or shortly ignition temperature) and formerly also known as kindling point, of a substance is the lowest temperature at which it spontaneously ignites in a normal atmosphere without an external source of ignition, such as a flame or spark. [1]
Plutonium in the delta (δ) phase [8] 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 ...
Reference Kelvin Celsius Fahrenheit Comments 1 H hydrogen (H 2) ; use: 13.99 K: −259.16 °C: −434.49 °F WEL: 14.01 K: −259.14 °C: −434.45 °F CRC: −259.16 °C: LNG
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]
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.
Fission product yields by mass for thermal neutron fission of U-235 and Pu-239 (the two typical of current nuclear power reactors) and U-233 (used in the thorium cycle). This page discusses each of the main elements in the mixture of fission products produced by nuclear fission of the common nuclear fuels uranium and plutonium.
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.