Publication Laka-library:
Thorium for fission power

AuthorJ.W.Storm van Leeuwen
DateMay 2016
Classification (THORIUM CYCLE - GENERAL)

From the publication:

Thorium for fission power
Jan Willem Storm van Leeuwen, MSc
Independent consultant
member of the Nuclear Consulting Group
May 2016

1 Thorium as nuclear fuel
Thorium is a radioactive metal, 3-4 times more abundant in the Earth’s crust 
than uranium. Thorium has a characteristic terrestrial isotopic composition, 
consisting for nearly 100% of Th-232, and traces of other isotopes, for 
example Th-228 and Th-230.
Thorium is a highly reactive metal. At standard temperature and pressure, 
thorium is slowly attacked by water, but does not readily dissolve in most 
common acids, the exception being hydrochloric acid. It dissolves in 
concentrated nitric acid containing a small amount of catalytic fluoride 
or fluorosilicate ions; if these are not present, passivation can occur. 
At high temperatures, it is easily attacked by oxygen, hydrogen, nitrogen, 
the halogens, and sulfur. It can also form binary compounds with carbon 
and phosphorus.
Finely divided thorium metal presents a fire hazard due to its 
pyrophoricity and must therefore be handled carefully. When heated in air, 
thorium turnings ignite and burn brilliantly with a white light to produce 
the dioxide. In bulk, the reaction of pure thorium with air is slow, 
although corrosion may eventually occur after several months;  most 
thorium samples are however contaminated with varying degrees of the 
dioxide, which greatly accelerates corrosion. Such samples slowly tarnish 
in air, becoming gray and finally black.
None of the thorium isotopes is fissile. The concept of thorium as nuclear 
fuel is based on the conversion by neutron capture of non-fissile 
thorium-232 into uranium-233, which is as fissile as plutonium-239. 
Consequently the application of thorium as fuel for nuclear power 
requires a special nuclear system. We will return to this issue below.