Fr.: étoile très riche en métaux
The property of some crystals of exhibiting three different colors when viewed from three different directions under white lights. → dichroism.
From Gk. tri- "three" + chroic, from chroma "color" + -ism.
Sefâmi, from se, → three, + fâm "color," + -i noun suffix.
Fr.: enrichissement de l'uranium
The process by which the percentage of → fissile uranium in a sample is increased. Uranium obtained from mining contains several → isotopes of uranium in different compositions, such as U-238 (~99%), U-235 (~0.7%), and U-234 (~0.02%). Among them, U-235 is the only one that is fissile, i.e. can be used in a → nuclear reactor to produce heat (and consequently electricity) in a controlled manner. As such, the concentration of U-235 as a fuel used in a reactor needs to be increased, which is done using several techniques, such as → gaseous diffusion.