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Glossary G - I


RadTown Glossary
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Gamma Rays

High-energy electromagnetic radiation emitted by certain radionuclides when their nuclei transition from a higher to a lower energy state. These rays have high energy and a short wave length. All gamma rays emitted from a given isotope have the same energy, a characteristic that enables scientists to identify which gamma emitters are present in a sample. Gamma rays are very similar to x-rays.

Geiger Counter

A radiation detection and measuring instrument. It consists of a gas-filled tube containing electrodes, between which there is an electrical voltage, but no current flowing. When ionizing radiation passes through the tube, a short, intense pulse of current passes from the negative electrode to the positive electrode and is measured or counted. The number of pulses per second measures the intensity of the radiation field. It is the most commonly used portable radiation detection instrument.

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The time in which one half of the atoms of a radioactive isotope disintegrates into another nuclear form. Half-lives vary from billionths of a billionth of a second to billions of years. Also called physical or radiological half-life.

Hazardous Waste

Waste products that can pose a substantial or potential hazard to human health or the environment when improperly managed. Hazardous waste is regulated at the federal level under the Resource Conservation and Recovery Act. A waste may be hazardous because it has at least one of four characteristics - ignitable, corrosive, reactive, or toxicity--or it may be included on one of several lists of waste groups that are known to be hazardous.

High-Level Radioactive Waste

The highly radioactive material resulting spent nuclear fuel reprocessing:

The highly radioactive materials can be designated as high-level waste, if they require permanent isolation. This determination is made by the U.S. Nuclear Regulatory Commission based criteria established in U.S. law.

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RadTown Glossary
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A nonmetallic solid element. There are both radioactive and non-radioactive isotopes of iodine.

  1. An atom or molecule that has too many or too few electrons, causing it to have an electrical charge, and therefore, be chemically active
  2. An electron that is not associated (in orbit) with a nucleus

The process of adding one or more electrons to, or removing one or more electrons from, atoms or molecules, thereby creating ions. High temperatures, electrical discharges, or nuclear radiation can cause ionization. You can learn more about ionization at

Ionizing Radiation

Any radiation capable of displacing electrons from atoms or molecules, thereby producing ions. Some examples are alpha, beta, gamma, and X-rays. High doses of ionizing radiation may produce severe skin or tissue damage.


Exposure to radiation.

Having the same number of protons but a different number of neutrons.

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