ASTM D3648-23: Measurement Of Radioactivity

Geiger counter with radioactive materials in the background adhering to ASTM D3648-23 practices for measurement of radioactivity.

Radiation with enough energy to cause changes at the atomic level is called ionizing radiation, and it can damage cells. Consequently, it is important to measure the potential health effects of radiation. ASTM D3648-23: Standard Practices For The Measurement Of Radioactivity summarizes the various generic radiometric techniques, equipment, and practices that are used for the measurement of radioactivity.

What Is ASTM D3648?

ASTM D3648-23 covers a review of the accepted counting practices currently used in radiochemical analyses. The practices are a compilation of the various counting techniques employed in the measurement of radioactivity, and they are divided into four sections: General Information, Alpha Counting, Beta Counting, and Gama Counting. The standard contains information applicable to all types of radioactive measurements, while each of the other sections is specific for a particular type of radiation.

How Is Radioactivity Measured?

Radioactivity is a measure of the ionizing radiation released by a radioactive material. There are different but interrelated units for measuring radioactivity and estimating health effects. The amount of radioactivity is reported in Becquerel (Bq), which is the international unit, or the Curie (Ci), which is the unit used in the United States. Since a curie is a large unit, radioactivity results are usually shown in picocuries (pCi). A picocurie is one trillionth of a curie. The higher the number, the more radiation released by the material.

Detecting Radiation

A Geiger counter, also called a Geiger-Muller tube, is commonly used to measure the amount of radioactivity (but there are other types of detectors that may be used). It detects ionizing radiation such as alpha particles, beta particles, and gamma rays using the ionization effect produced in a Geiger–Muller tube, which has two main parts: a sealed tube or chamber that is filled with gas, and an information display.

Radiation enters the tube and when it collides with the gas, it pushes an electron away from the gas atom and creates an ion pair. A wire in the middle of the tube attracts electrons, creating other ion pairs and sending a current through the wire. The current goes to the information display and moves a needle across a scale or makes a number display on a screen. These devices usually provide “counts per minute,” or the number of ion pairs created every 60 seconds. If the loudspeaker is on, it clicks every time an ion pair is created. The number of clicks indicates how much radiation is entering the Geiger counter chamber.

Common Radiation Exposures

People are exposed to radiation daily from different sources, such as naturally occurring radioactive materials in the soil, the sun, and cosmic rays from outer space (which we receive more when we fly in an airplane). Other sources of radiation are man-made, such as x-rays, radiation therapy to treat cancer, and electrical power lines. Too much exposure to radiation can damage tissues by changing cell structure and damaging DNA. This can cause serious health problems, including cancer.

ASTM D3648-23: Standard Practices For The Measurement Of Radioactivity is available on the ANSI Webstore.

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