HardAssetsInvestor

Written by Tom Vulcan  |

April 19, 2010

Radioisotopes: A Market In Decay?

Details

Radioisotopes are used in everything from smoke detectors to cancer treatments. But is a supply crunch on the way?

• What is a radioisotope, and how is it used?
• How do you make a radioisotope?
• Ways to play an increasingly small supply

 

Radioisotopes, or unstable versions of an element that emit radiation as they try to reach a more stable form, are critical in modern medicine:

"⁹⁹Mo is used to produce ⁹⁹Mo/^99mTc generators (a generator technology developed at Brookhaven National Laboratory) for use in nuclear medicine. ^99mTc is the most widely used radionuclide in nuclear medicine, both for the detection of disease and for the study of organ structure and function. More than 15 million procedures are performed each year in the U.S. using ^99mTc."

                                                                Isotopes for the Nation's Future — A long range plan      

                                                                U.S. Nuclear Science Advisory Committee — Aug. 27, 2009

 

However, the U.S. produces none of the radioisotope molybdenum-99 (⁹⁹Mo), from which comes the radioisotope technetium-99m (^99mTc). Indeed, none has been produced in the country since 1988.

^99mTc is so important that it is used in more than 80 percent of all nuclear medicine diagnostics and studies of organ structure and function. Not only is the figure of 15 million, quoted above, probably too small, but the number of procedures using ^99mTc in the U.S. alone probably accounts for a half, if not more, of the 35 million such procedures carried out globally each year.

 

A Short Guide To Isotopes

The simplest way to envisage an atom is to imagine a nucleus, which consists of protons and neutrons, surrounded by a cloud of electrons. The number of protons in the nuclei of any element's atoms determines the chemical character of that element.

Different isotopes of an element all contain the same number of protons, but different numbers of neutrons and, hence, have different atomic masses. While some isotopes are stable, others are not: For the 82 stable elements, there are around 275 associated stable isotopes and 1,800 unstable isotopes or radioisotopes. (The U.S. Nuclear Science Advisory Committee (NSAC), in the report quoted above, estimates the number of natural and artificial radioactive isotopes as exceeding 3,200 and "...growing every year.")

The nuclei of unstable isotopes usually stabilize through radioactive decay (hence the name "radioisotope"). That is, as the isotope tries to reach a more stable form, it kicks off alpha particles—two protons and two neutrons—and/or beta particles, which are electrons or positrons. These beta particles are often (but not always) accompanied by the emission of gamma rays or electromagnetic radiation.

Unstable isotopes rarely occur in nature and are nearly always produced artificially. For example, ^99mTc is produced as the artificially produced radioisotope ⁹⁹Mo decays, which decays through gamma ray emission (and a rearrangement of its nucleus) to become ⁹⁹Tc.

 

Using Radioisotopes

Radioisotopes, either naturally occurring or artificially produced, are useful because they emit radiation, whether alpha, beta or gamma. You're probably familiar with carbon dating, which uses a naturally occurring isotope of carbon, ¹⁴C (carbon-14); ¹⁴C can measure the age of water up to 50,000 years old. But it may come as a surprise that, according to the Australian Nuclear Science and Technology Organisation (ANSTO), smoke detectors represent "the largest number of devices based on radioisotopes used world-wide." (The devices use a minute quantity of ²⁴¹americium, which is a product of the decay of plutionum-241.)  

Around 200 different radioisotopes are currently used in a variety of applications, such as in food and agriculture, industry or medicine.