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General
- Thorium is a chemical
element with the symbol Th and atomic number 90.
- Pure thorium is a
silvery-white metal that retains its luster for several months.
- Thorium has the
largest liquid range of any element: 2946 K between the melting point
and boiling point.
- Thorium is a
naturally-occurring, slightly radioactive metal.
- It is found in small
amounts in most rocks and soils, where it is about three times more
abundant than uranium.
- It is the most common
of a group of elements called the actinides.
- The most common ores
of thorium are thorite and monazite.
Mining
Process
- Thorium is a
relatively abundant element in the Earth's crust. Scientists estimate
that the crust contains about 15 parts per million of the element.
- The thorium in
monazite, thorite, or other minerals is first converted to thorium
dioxide (ThO2). This thorium dioxide is then heated with calcium to get
the free element.
- U-233 must be
recycled if thorium cycle is to be sustainable.
- Calculations are
performed to estimate the feasibility of operation of heavy-water
thermal neutron power reactor in self-su±cient thorium cycle.
- Cost of thorium
mining is much less than that of uranium because the radiation danger in
the process of thorium mining is »100 times less than in the uranium
mining.
Technology
- The coating of mouse
myocardial cells has been investigated with a variety of cytochemical
methods. The coating of the surface membrane gives a positive reaction
with ruthenium red, colloidal thorium, phosphotungstic acid (PTA) at low
pH, silver methenamine after periodic oxidation(PA-silver technique).
- A procedure has been
developed for the determination of uranium and thorium in geological
samples using extraction chromatography.
- A new oxidimetric
method for the titrimetric determination of thorium is based on the
precipitation of thorium as the normal molybdate followed by the
reduction and titration of the molybdenum equivalent to the thorium.
Market
- The thorium fuel
cycle could not compete economically with the well-known uranium cycle.
- Total amount of
thorium produced worldwide: 37 500 tonnes(US, Australia, China, India).
- Norway has one of the
major thorium reserves in the world.
- Thorium demand
worldwide remained depressed because of concerns over its naturally
occurring radioactivity.
- Thorium consumption
worldwide is relatively small compared with that of most other mineral
commodities.
- All thorium
compounds, metal, and alloys used by the domestic industry were derived
from imports, company stocks, or material previously acquired from the
U.S. Government stockpile.
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