Fr.: enrichissement chimique
The → process by which the relative → abundance of a given → chemical element or → species in an → astrophysical object is increased. For example the the → increase of the → heavy element content of the → interstellar medium due to → stellar evolution.
Fr.: enrichissement de deutérium
The → enrichment of deuterium (D) with respect to
→ hydrogen (H) in
→ Solar System molecules
when compared with the D/H ratio in the
→ interstellar → solar nebula.
H-bearing molecules in → comets,
→ planets, and → chondrite
→ meteorites show a systematic D enrichment
relative to the → molecular hydrogen of the solar
nebula. Because there is no nuclear source for D in the Universe,
the observed → isotopic enrichment must have its
origin in chemical reactions having faster reaction rates for D than for H.
In the Solar nebula the → isotopic fractionation
of D between → water and H followed the reversible reaction:
deuterium enrichment factor
karvand-e pordâri-ye doteriom
Fr.: facteur d'enrichissement en deutérium
1) A process that changes the → isotopic ratio
in a material. For example, for uranium
the ratio of U-235 to U-238 may be increased by gaseous
diffusion of uranium hexafluoride.
Verbal noun of → enrich.
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.