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Glossary N - P


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Naturally Occurring Radioactive Materials (NORM)

Radioactive materials that are found in nature. Until recently, technologically enhanced naturally occurring radioactive materials (TENORM) was referred to simply as NORM. The words technologically enhanced were added to distinguish clearly between radionuclides as they occur naturally and radionuclides that human activity has concentrated or exposed to the environment.


A small particle possessing no electrical charge typically found within an atom's nucleus. A neutron has about the same mass as a proton.

Neutron Radiation

Neutron radiation is energy released from an atom in the form of neutral particles called neutrons. Neutrons are part of the basic building blocks of atoms. They have no charge and are about the same mass as a proton. Due to ion-producing collisions with matter and absorption/decay processes, neutrons are a type of ionizing radiation.

Non-Ionizing Radiation

Radiation that has lower energy levels and longer wavelengths than ionizing radiation. It is not strong enough to affect the structure of atoms it contacts, but is strong enough to heat tissue and can cause harmful biological effects. Examples include radio waves, microwaves, visible light, and infrared from a heat lamp.

Nuclear Energy

The heat energy produced by the process of nuclear reaction (fission or fusion) within a nuclear reactor or by radioactive decay.

Nuclear Fuel Cycle

The series of steps involved in supplying fuel for nuclear power reactors. It can include mining, milling, isotopic enrichment, fabrication of fuel elements, use in reactors, chemical reprocessing to recover the fissionable material remaining in the spent fuel, re enrichment of the fuel material re fabrication into new fuel elements and waste disposal.

Nuclear Power Plant

An electrical generating facility using a nuclear reactor as its power (heat) source. The coolant that removes heat from the reactor core is normally used to boil water. The steam produced by the boiling water drives turbines that rotate electrical generators.


A proton or a neutron; a constituent of the nucleus


The central part of an atom that contains protons and neutrons. The nucleus is the heaviest part of the atom.


A general term applicable to all atomic forms of an element. Nuclides are characterized by the number of protons and neutrons in the nucleus, as well as by the amount of energy contained within the atom.

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The way in which people are exposed to radiation or other contaminants. The three basic pathways are inhalation (contaminants are taken into the lungs), ingestion (contaminants are swallowed), and direct (external) exposure (contaminants cause damage from outside the body).

Pico curie

One one-trillionth (1/1,000,000,000,000) of a curie.


A heavy, man-made, radioactive metallic element. The most important isotope is Pu-239, which has a half-life of more than 20,000 years; it can be used in reactor fuel and is the primary isotope in weapons. One kilogram is equivalent to about 22 million kilowatt-hours of heat energy. The complete detonation of a kilogram of plutonium produces an explosion equal to about 20,000 tons of chemical explosive.

Plutonium is a bone-seeking radiation hazard, and can be lethal depending on the dose and exposure time.


A radioactive chemical element and a product of radium decay. Polonium is found in uranium ores.

Power Reactor

A reactor designed to produce heat for electric generation, as distinguished from reactors used for research, for producing radiation or fissionable materials or for reactor component testing.

Protective Action Guide

A protective action guide tells state and local authorities at what projected dose they should take action to protect people from exposure to unplanned releases of radioactive material into the environment.


A small particle, typically found within an atom's nucleus, that possesses a positive electrical charge. The number of protons is unique for each chemical element.

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