Stichting Laka

Publication Laka-library:
Uranium enrichment: Just Plain Facts to Fuel an Informed Debate on Nuclear Proliferation and Nuclear Power (2004)

Author	Arjun Makhijani, Chalmers, Smith
	6-01-2-25-11.pdf
Date	October 2004
Classification	6.01.2.25/11 (URANIUM - ENRICHMENT)
Front

1. Uranium Enrichment - Introduction

There is one element that occurs in nature that has been the raw material for nuclear 
bombs: uranium, chemical symbol U. (1) Uranium occurs as a mixture of three 
different isotopes - that is, three different atomic weights that have virtually the same 
chemical properties, but different nuclear properties (see Uranium fact sheet, p. 30). 
These isotopes are U-234, U-235, and U-238. The first is a highly radioactive trace 
component found in natural uranium, but it is not useful in any applications; the 
second isotope is the only fissile material (2) that occurs in nature in significant 
quantities, and the third is the most plentiful isotope (99.284 percent of the weight 
of a sample of natural uranium is U-238), but it is not fissile. U-238 can, however, 
be split by high energy neutrons, releasing large amounts of energy and is therefore 
often used to enhance the explosive power of thermonuclear, or hydrogen, bombs.

(1) Thorium-232, which is also naturally occurring, can be used to make bombs
by first converting it into U-233 in a nuclear reactor. However, uranium fuel for 
the reactor, or fuel derived from uranium (such as plutonium) is needed for this 
conversion if U-233 is to be produced in quantity from thorium-232.
(2) A fissile material is one that can be spilt (or fissioned) by low energy neutrons
and is also capable of sustaining a chain reaction. Only fissile materials may be 
used as fuel for nuclear reactors or nuclear weapons. Examples of other fissile 
materials, besides uranium-235, are uranium-233 and plutonium-239.