Thorium and Environment

Thorium Metal Ingot

What happens to thorium when it enters the environment?

Thorium is a natural part of the environment.

Thorium changes extremely slowly into other radioactive substances.

It takes about 14 billion years for half of the thorium-232 to change into new forms.

As rocks are broken up by wind and water, the thorium and all other components of the rocks become part of the soil

Thorium in soil can be washed into rivers and lakes.

Windblown dust and volcanic eruptions are natural sources of thorium in the air.

Burning coal may release small amounts of thorium into the air.

Mining thorium or making products that contain it may also release thorium into the environment.

How does thorium get into the environment?

Natural thorium is present in very small quantities in virtually all rock, soil, water, plants and animals. Where high concentrations occur in rock, thorium may be mined and refined, producing waste products such as mill tailings. If not properly controlled, wind and water can introduce the tailings into the wider environment.

Commercial and federal facilities that have processed thorium may also have released thorium to the air, water, or soil. Man-made thorium isotopes are rare, and almost never enter the environment.

How does thorium change in the environment?

As thorium-232 undergoes radioactive decay, it emits an alpha particle, with accompanying gamma radiation, and forms radium-228. This process of releasing radiation and forming a new radionuclide continues until stable lead-208 is formed. The half-life of thorium-232 is about 14 billion years.

Two other isotopes of thorium, which can be significant in the environment, are thorium-230 and thorium-228. Both decay by alpha emission, with accompanying gamma radiation, in 75,400 years and 1.9 years, respectively.

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