Lesson 2 ◆ 2.7 Enrichment Methods

Syllabus Coverage: NFC1.1

Natural uranium has the following isotopic composition (by mass):

Natural uranium consists of 238^{238}U (99.274%), 235^{235}U (0.711%), and 234^{234}U (0.006%).

For most reactor types, the content of fissile 235^{235}U must be increased — a process known as enrichment. Light water reactors (PWR and BWR) typically require fuel enriched to 3-5% 235^{235}U. Notable exceptions include CANDU reactors and the former UK Magnox reactors, which used natural uranium fuel.

The principal methods of enrichment that have been developed are:

  1. Gaseous diffusion — historically the first large-scale method
  2. Gas centrifuge — now the dominant commercial method
  3. Laser separation (AVLIS and MLIS) — experimental/developmental
  4. Electromagnetic separation (Calutron) — historical, used in WWII
  5. Gas nozzle (aerodynamic) — experimental
  6. Chemical exchange — limited application