Biochemical Techniques and Instrumentation

3.1.3. Types of radioisotopes

Naturally occurring radioisotopes:

1. Primordial radioisotopes

Primordial radioisotopes originate mainly from the interiors of stars. eg. Uranium and Thorium. They are still present as their half-lives are so long that they are not yet completely decayed.

2. Secondary radioisotopes

Secondary radioisotopes are radiogenic isotopes derived from the decay of primordial radioisotopes. They have shorter half-lives than primordial radioisotopes.

3. Cosmogenic radioisotopes

Cosmogenic isotopes are continually being formed in the atmosphere due to cosmic rays. eg. Carbon-14

Artificially produced radioisotopes:

1. Nuclear reactors

The high flux of neutrons activate the elements placed within the nuclear reactor to produce radioisotopes. eg. Thallium-201 and Iridium-192.

2. Particle accelerators

Cyclotrons accelerate protons to bombard a target and produce positron that emits radioisotopes. eg. Fluorine-18.

3. Radionuclide generators

Radioisotopes generators contain a parent isotope produced in a nuclear reactor, that decay to produce a radioisotope. e.g.Technetium-99 produced Molybdenum -99.

4. Nuclear explosions

Radioisotopes produced as an unavoidable side effect of nuclear and thermonuclear explosions.