June 2012

Geiger Counters 3 - Uses

            Geiger counters have many important uses with respect to the detection and measurement of alpha, beta and gamma radiation. Uranium-238 with traces of  uranium-235 is mined for refinement use as a fuel. Plutoium-239 and thorium-232 are also used as nuclear fuels. The use of commercial radioisotopes is wide-spread. Sources of alpha particles or helium nuclei include polonium-210 and uranium-238. Sources of beta particles or fast electrons include strontium-90, thallium-204, carbon-14 and hydrogen-3 or tritium. Sources of energetic photons of gamma include barium-133, cadmium-109, cobalt-57, cobalt-60, europium-152, manganese-54, sodium-22, zinc-65 and technetium-99. Cesium-137 emits gamma and beta. Americium-241emits gamma and alpha.

Non-nuclear Industrial Uses

            Radiation and Geiger counters are used to measure the strength of welds, the wear and corrosion of metals, and in the analysis of minerals and fuels. Gamma rays from Cobalt-60 are used to kill bacteria in foods and halt cellular processes that would lead to sprouting. This process must be closely monitored.

Nuclear Industry Uses

            Geiger counters are used for detecting leakage of radioactive materials from containers during storage and transportation, detecting radioactive contamination of other objects and materials, detecting leakage of radiation from pipes and containment vessels in nuclear power plants. Geiger counters are used to locate and evaluate deposits of uranium ores.

Environmental Uses

            Geiger counters are used to monitor radiation levels in the atmosphere, ground water, lakes, rivers and oceans. Radiation is monitored in landfills and dumps, nuclear waste repositories, warehouses and transport areas. Radioisotopes can help monitor pollutants and to measure the movement of surface waters as well as the runoff of rain water. Geiger counters are used by first responders to check for radiation at a disaster site or the site of a terrorist attack.

Home Uses

            Radon gas is a significant danger in homes and should be monitored. Smoke detectors contain radioactive materials that may be released if the detectors are damaged. Radioactive particles and gases may invade the home from nuclear accidents and can be tested for with Geiger counters.

Medical Uses

            A number of different isotopes are utilized in modern medicine that must be carefully handled and should be monitored by Geiger counters. Some medical equipment emits radiation such as X-rays. Radioisotopes injected into patients are taken up by specific tissues and used for imaging or for treatment of cancers.

Laboratory Uses

Geiger Counters 2 - Evolution of common Geiger Counters

            Ionizing radiation is measured by a device called a Geiger counter. The Geiger counter is named after its inventor Hans Geiger who created the Geiger counter in 1908. Walther Müller collaborated on improving the counter in 1928 and the counters are also called Geiger-Müeller counters.  A Geiger counter consists of a Geiger-Müeller tube which detects radiation by emitting a pulse of electrical energy when penetrated by ionizing radiation and supporting hardware.

            Geiger-Mueller tubes come in a range of sizes, shapes and sensitivities. One end is open to allow the entry of ionizing radiation. Some Geiger counters allow thin shields which block alpha particles and thick shields which block beta particles to be shifted into position over the open end of the tube. The tube may be included inside a handheld device or it may be on a cable attached to a box containing the support hardware. Inexpensive Geiger counters for wide spread use have evolved over the years.

            The US federal civil defense agencies had a Geiger counter design called a CD V-700 manufactured by 15 different contractors beginning around 1950.. The early models used special high voltage batteries which were replaced by standard D cells in the later models. CD V-700 design included  bulky metal box about twelve inches long by eight inches high by six inches wide and weighting about 5 pounds. The box has a long handle running the length of the top. The Geiger-Müeller tube is about nine inches long and three inches in diameter on a thirty six inch cable. The CD V-700 is used to detect gamma and beta radiation. Some were modified to be able to detect alpha radiation by making the window in the end of the tube larger to provide more area. Tens of thousands of these models were distributed to build state and local civil defense agencies in the 1950s and 1960s These Geiger counters are what people usual think of when Geiger counters are mentioned. They have been featured in many movies and television shows and many are still in use today.

            A newer design was manufactured for the U.S. government in the 1980s by the Victoreen company, one of the contractors for the original CD V-700. The model 496 was build in the same box as the CD V-700 but featured some improvements such as BNC connectors for external probes, a built in speaker that clicks to indicate radiation, a batter test circuit and a meter graduated in clicks per minute.

Pages