Physics of Nondestructive Evaluation > X-Rays > Isotope Decay Rate

Isotope Decay Rate

Common Radioactive Isotopes

Cobalt (Co60):
Co60 decays with 1.33 and 1.17 MeV gamma rays in half life of 5.27 years. Co60 is made by irradiation of Co59 in a nuclear reactor. This nuclide is useful for a thickness gauge of metal, level gauge, density gauge, a gamma radiography, and for sterilization.

Iridium (Ir192):
This nuclide is useful for a gamma radiography. Ir192 decays with 0.328 gamma rays in half life of 74 days.

Cesium (Cs137):
Cs137 is usually separated from rad waste of nuclear fuels. This nuclide is useful for a level gauge, a gamma radiography. Cs137 decays with 0.662 Mev gamma rays in a half life of 30.17 years.

Ytterbium (Yb169):
Yb169 has multiple uses including in memory devices and tuneable lasers. Yb169 decays with 0.063 MeV gamma rays in a half life of 32 days.

Thulium (Tm170):
This nuclide is useful for a thickness gauge of metal, a density gauge, and a gamma radiography. Tm170 decays with 0.084 MeV gamma rays in half life of 130 days.

Carbon14 Dating :
C-14 decays with by emitting a low energy Beta with a half-life of 5730 years. Radio-carbon dating is a method of obtaining age estimates on organic materials that have been used to date samples as old as 700,000 years.

The half-life of a material is the time it takes for half of the material to have decayed away. For example if you have one mCi of a material with a half life of 14.3 day, then after those 14.3 days only .5 mCi of the material will be left. AFter 28.6 days only .25 mCi will be left. Each radionuclide decays at its own unique rate which cannot be altered by any chemical or physical process. A useful measure of this rate is the half-life of the radionuclide. Half-life is defined as the time required for the activity of any particular radionuclide to decrease to one-half of its initial value. In other words one-half of the atoms have reverted to a more stable state material. Half-lives of radionuclides range from microseconds to billions of years. Half-life of two widely used industrial isotopes are 74 days for iridium-192, and 5.3 years for cobalt-60. More exacting calculations can be made for the half-life of these materials, however, these times are commonly used.

The applet below offers an interactive representation of radioactive decay series. The four series represented are Th232, Ir192, Co60, Ga75, and C14. Use the radio buttons to select the series that you would like to study. Note that Carbon-14 is not used in radiography, but is one of many useful radioactive isotopes used to determine the age of fossils.

The Sequence Info button displays a chart that depicts the path of the series with atomic numbers indicated on the vertical axis on the left, and the number of neutrons shown along the bottom. Colored arrows represent alpha and beta decays. To return to the main user interface, click the "Dismiss" button.

Initially, a selected series contains all parent material, and the amount is represented by a colored bar on a vertical logarithmic scale. Each line represents a factor of ten. In order to step forward through the sequence by a specified number of years, you may type the appropriate number into the "Time Step" field and hit "Enter." A negative time step will backtrack through the sequence.

You may choose a step interval in years and progress through each step by pressing the "Enter" key. The "Animate" button will automate the progress through the series. You can either choose a time step before you animate or leave it at zero. If the time step is left at zero, the system will choose time steps to optimize viewing performance.

Note: “If you want to investigate the uranium and thorium decay chains they can do so, here: ”More Information