Thorium Nuclear Fuel Cycle

Thorium Facts (as related to nuclear fuel usage)

Chemical Symbol is: Th

Physical & Chemical Properties

(facts below taken from Encyclopaedia Britannica CD 97, unless otherwise noted)

• Melting point of metal: 1700° C (3100° F) ³
• Melting point of oxide (ThO₂): 3050° C (5522° F) ³
• Natural Occurance:
  • 1/2 as abundant as Lead (Pb)
  • 3x more than Uranium

Thorium reacts slowly with air at room temperature to form a film (tarnish) of thorium dioxide (ThO₂ - sometimes also called "Thoria"). Unlike uranium dioxide (UO₂), thorium dioxide is the only stable oxide of thorium, which accounts for the greater stability of Thoria versus uranium dioxide. Thorium dioxide is also much more resistant to chemical interactions, which is demonstrated by its uses as a high temperature crucible (container) or in the gas mantle (used in "Coleman" camping laterns) invented in 1885 by Welsbach; which is a fabric soaked with a mixture of thorium nitrate and cerium nitrate, which upon ignition becomes a 99% Thoria "mantle" that glows white-hot when heated by a gas flame.

For nuclear applications, also important are thorium's radiation stability and thorium dioxide's higher thermal conductivity. These properties suggest thorium fuels have greater potential safety and fuel durability than the currently used uranium dioxide or even "MOX" (Mixed Oxide Fuels - formed by a mixture of plutonium dioxide, PuO₂, & uranium dioxide) nuclear fuels.

Nuclear Properties

• Thorium is radioactive; half-life of 14,100,000,000 years ¹.
• Natural thorium & uranium give you over half the radiation you receive now!
• Thorium is composed of primarily 1 isotope; Th-232.
  Thorium can also have up to ~100 ppm Th-230; depends upon colocation with uranium. ²
• Three times greater abundance of Th over uranium means 3 times more energy available than U.
  • More energy from thorium than all oil, coal, natural gas, or uranium combined!
  • Thousands of years of energy.
• Natural thorium absorbs a neutron (in a reactor) to ultimately form Uranium-233 (U-233); the third nuclear fuel {see diagram below}.

Thorium Nuclear Fuel Cycle Information

The "Transmutation" of Thorium into Uranium Nuclear Fuel

The Multiple Production Paths of Uranium-232

{NOTE: Above diagram data from CRC Handbook, 53rd Ed. Section "B"}

REFERENCES

1. CRC Handbook of Chemistry & Physics, 53rd Edition, page B-507. (Back)

2. The ratio of Th230:Th232 can be calculated by:

Th230/Th232 = 1.76 x 10^-5 * rU,Th.

Pgs 284 & 378, "NUCLEAR CHEMICAL ENGINEERING", Benedict, Pigford, & Levi (1981). Also, Page 515, "NUCLEAR REACTOR ENGINEERING", Glasstone & Sesonske (1981). (Back)

3. 53rd Ed. CRC Handbook of Chem. & Physics. (Back)