23
Isotope Emits Half-life Product
U-238 alpha 4.5
billion
years
Th-234 Thorium
Th-234
beta
24.1 days
Pa-234
Proactinium
Pa-234 beta 1.17
minutes
U-234 Uranium
U-234 alpha 250,000
years
Th-230 Thorium
Th-230 alpha 80,000
years
Ra-226 Radium
Ra-226 alpha 1,602
years
Rn-222 Radon
Rn-222 alpha 3.8
days Po-218 Polonium
Po-218 alpha 3
minutes Pb-214 Lead
Pb-214 beta
26.8
minutes
Bi-214 Bismuth
Bi-214 beta 19.7
minutes
Po-214 Polonium
Po-214 alpha 164
micro-
seconds
Pb-210 Lead
Pb-210 beta
21
years Bi-210 Bismuth
Bi-210 beta 5
days Po-210 Polonium
Po-210 alpha 138
days Pb-206 Lead
Measuring Radiation
Alpha, beta, gamma, and x-rays ionize material they strike or pass
through. The amount of radiation is generally determined by
measuring the resulting ionization.
The Geiger tube used in the Radalert 100 consists of an anode
(positive electrode) positioned in the center of a tubular cathode
(negative electrode) filled with a mixture of argon, neon, and either
chlorine or bromine gases. The cathode is a thin-walled metallic
cylinder sealed at each end with an insulating disk to contain the
gas. The anode is a wire that extends into the cylinder. A high
voltage is applied to the electrodes to create an electrical field
within the chamber. When radiation passes through the chamber