Enrichment: the basics

Quick 'Chemistry 101' Refresher

Naturally occurring Uranium (U)  is composed of 2 major isotopes, all have the same Atomic Number but different Atomic Weights.  These isotopes have similar chemical properties but different nuclear properties.

  • • U-238  The most plentiful/abundant; over 99% of nature uranium is U-238.
  • • U-235  The only fissile uranium isotope; approximately 0.72% of natural uranium is U-235.
Uranium and the Periodic Table

Atomic Mass refers to 1 atom, describing a single Isotope of an element.

Atomic Mass Calc

Why Enrichment?

Uranium cannot be used as a fuel or weapon in its natural state.   To be used as reactor fuel or bomb manufacture, U-235 must be separated from natural uranium.
U-235 is the only fissile isotope in natural Uranium (U), therefore Uranium must be "enriched" to have a higher percent concentration of U-235.

% of U-235 comparison

U-235 Concentration needed for:

    Power reactor
  • 3-5%
  • This level of uranium is called Low Enriched Uranium (LEU)
    Nuclear weapon  
  • 90%
  • Referred to as Weapons Grade or Highly Enriched Uranium (HEU)

Gaseous Diffusion Enrichment Process

Gaseous Diffusion is the method used at the Paducah Gaseous Diffusion Plant to enrich uranium.  See the process broken down to the molecular level.

Uranium Enrichment Stages

The PGDP Enrichment Process as presented to the Heath Middle School

enrichment process explanation

Click here to view the rest of the Middle School presentation