Radiation, nuclear

Energy given off by matter in the form of tiny fast-moving particles (alpha particles, beta particles, and neutrons) or pulsating electromagnetic rays or waves (gamma rays) emitted from the nuclei of unstable radioactive atoms.

Atoms

All matter is composed of atoms, which are made up of various parts; the nucleus contains minute particles called protons and neutrons, and the atom’s outer shell contains other particles called electrons.

Nucleus

The nucleus carries a positive electrical charge, while the electrons carry a negative electrical charge. These forces work toward a strong, stable balance by getting rid of excess atomic energy (radioactivity). In that process, unstable radioactive nuclei may emit energy, and this spontaneous emission is called nuclear radiation.

Types of radiation

All types of nuclear radiation are also ionizing radiation, but the reverse is not necessarily true; for example, x-rays are a type of ionizing radiation, but they are not nuclear radiation because they do not originate from atomic nuclei.

Natural radiation

In addition, some elements are naturally radioactive, as their nuclei emit nuclear radiation as a result of radioactive decay, but others are induced to become radioactive by being irradiated in a reactor.

Differences in radiation

Naturally occurring nuclear radiation is indistinguishable from induced radiation.

Glossary of radiation terms

• 11(e)(2) byproduct material A legal definition from the Atomic Energy Act. The tailings or wastes produced by the extraction or concentration of uranium or thorium from any ore processed primarily for its source material content.

• Absorbed Dose   The amount of radiation absorbed by an object or person. The unit for absorbed dose is the rad (U.S. unit) or the gray (Gy, the international unit). One gray is equal to 100 rads.

• Acute Exposure   Exposure to an amount of radiation all at once or from multiple exposures in a short period of time. In most cases, a large acute exposure to radiation causes both immediate (see radiation sickness) and delayed effects (cancer or death).

• Agreement State   A state that has signed an agreement with the U.S. Nuclear Regulatory Commission (NRC) allowing the state to regulate the use of byproduct radioactive material. See, NRC Agreement State Program: http://www.nrc.gov/about-nrc/state-tribal/agreement-states.html

• Alpha Particle   A form of particulate ionizing radiation made up of two neutrons and two protons. Alpha particles pose no direct or external radiation threat; however, they can pose a serious health threat if ingested or inhaled.

• Ambient Air   The air that surrounds us.

• Background Radiation   Radiation that is always in the environment. The majority of background radiation occurs naturally and a small fraction comes from man-made elements.

• Becquerel   Becquerels are the international unit used to measure radioactivity. One becquerel is the amount of a radioactive material that will undergo one transformation per second. Becquerels are not used to measure radiation dose or radiation exposure. The U.S. unit is the Curie (Ci). Abbreviation:Bq

• Beneficiation   The use of milling, flotation, sintering, gravity concentration or other processes to allow the desired mineral to be separated from wastes and used.

• Beta Particle   A form of particulate ionizing radiation made up of small, fast-moving particles. Some beta particles are capable of penetrating the skin and causing damage such as skin burns. Beta-emitters are most hazardous when they are inhaled or swallowed.

• Byproduct Material   Radioactive materials left over from the production or use of plutonium, enriched uranium or uranium-233.

• Chronic Exposure   Continuous or intermittent exposure to radiation over a long period of time. With chronic exposure, there is a delay between the start of the exposure and the observed health effect, such as cancer, benign tumors, cataracts, and potentially harmful genetic changes.

• Contact-handled   A legal definition from the WIPP Land Withdrawal Act. Transuranic waste whose radioactive dose rate is less than or equal to 200 mrem per hour. Workers may directly handle drums of this waste.

• Contamination (radiation)   Radioactive contamination occurs when radioactive material is deposited on or in an object or person. A contaminated person has radioactive materials on or inside their body.

• Coordinating Agency   The federal department or agency with primary responsibility for coordinating the federal response to a large-scale emergency.

• Curie   The curie is U.S. unit used to measure radioactivity. One curie is roughly the activity of one gram of Radium-226. Curies are not used to measure radiation dose. The international unit is the Becquerel (Bq). Abbreviation:Ci

• Decay Chain   The series of decays or transformations that radionuclides go through before reaching a stable form. For example, the decay chain that begins with Uranium-238 culminates in Lead-206, after forming intermediates such as Uranium-234, Thorium-230, Radium-226, and Radon-222. Also called the "decay series."

• Decay Products   The atoms formed and the energy and particles emitted as radioactive material decays to reach a stable form.

• Decommission   The process of removing a nuclear facility from service. This involves reducing residual radioactivity to a level that permits the release of the property for limited or unrestricted use.

• Decontamination (radioactive)   The removal of radioactive material from a structure, object or person.

• Depleted Uranium   Depleted uranium (DU) is the material left after most of the uranium-235 is separated from uranium-238 and uranium-234 for use in nuclear power. Abbreviation:DU

• Dewatered   Solids or soils are considered dewatered when the free water is removed from the material. Dewatered does not mean dry; the material may still be moist.

• Dirty Bomb   A mix of explosives, such as dynamite, with radioactive powder or pellets. Also known as a radiological dispersal device (RDD). A dirty bomb is not a nuclear weapon.

• Dose (radiation)   The amount of radiation delivered to an object or person.

• Dose Rate   The radiation dose delivered per unit time.

• Effective Dose   The amount of radiation absorbed by an object or person, adjusted to account for the type of radiation received and the effect on particular organs. The unit used for effective dose is sievert (Sv, the international unit) or rem (U.S. unit).

• Emanation Rate   The rate which radon will escape a matrix. Often expressed as a percentage. For soils, typical emanation rates are 20 – 30%; for scale or slag, ~1%.

• Epidemiological Studies   Studies of the distribution in a population of disease and other health issues as related to age, sex, race, ethnicity, occupation, economic status, or other factors.

• Exposure Pathway   The way in which a person is exposed to radiation. The three basic pathways are inhalation (breathing), ingestion (eating or drinking), and external exposure (from outside the body).

• Exposure (radiation)   Radiation exposure, also called irradiation, occurs when radioactive material or a radiation machine emits radiation. You can be exposed to radiation without being contaminated. Having a medical x-ray is an example of being exposed but not contaminated. Many radiation monitors measure exposure rates.... more

• Fallout   Radioactive material in the air from a nuclear explosion that will cool into dust-like particles and fall to the ground.

• Federal Radiation Council   The Federal Radiation Council (FRC) was established to advise the President on radiation matters related to health. These responsibilities and authorities were transferred to EPA when it was established by President Nixon under Reorganization Plan No. 3 of 1970.  Abbreviation:FRC

• Fission   The splitting of an atomic nucleus into at least two other nuclei with the release of a relatively large amount of energy. Fissioning that occurs without any outside cause is called "spontaneous fission."

• Fracking   Hydraulic fracturing, also referred to as "fracking," is the process of drilling into host formations (shales and tight sandstones) and injecting fluids and sand under pressures great enough to fracture the rock formations to allow the extraction of oil and gas.

• Fuel Cycle   The series of steps involved in supplying fuel for nuclear power reactors. The fuel cycle can include milling, fabrication and use of fuel.

• Fusion   A reaction in which two lighter atomic nuclei unite to form a heavier one. Reactions of this type release enormous amounts of energy. The energy of the sun and stars come from fusion.  

• Gamma Rays   A form of ionizing radiation that is made up of weightless packets of energy called photons. Gamma rays can pass completely through the human body; as they pass through, they can cause damage to tissue and DNA.

• Generally Applicable Standards   Requirements that apply to general categories of activities, conditions or sites, rather than any specific situation or place. Under the Atomic Energy Act of 1954, EPA has authority to establish "generally applicable environmental standards for the protection of the general environment from radioactive material."

• Geographic Information System   A system for linking information to a particular geographical location. A Geographic Information System (GIS) allows users to manipulate and analyze specific provided data. Abbreviation:GIS

• Gray   A gray is the international unit used to measure absorbed dose (the amount of radiation absorbed by an object or person). The U.S. unit for absorbed dose is the rad. One gray is equal to 100 rads. Abbreviation:gy

• Half-life   The time required for half of the radioactive atoms present to decay or transform. Some radionuclides have half-lives of mere seconds, but others have half-lives of hundreds or millions of years.

• Health Physics   A scientific field that focuses on radiation protection of humans and the environment.

• High-level Radioactive Waste   Highly radioactive materials produced as a byproduct inside nuclear reactors. Other highly radioactive materials can be designated as high-level waste, if they require permanent isolation.

• Igneous   A type of rock formed when molten volcanic rock has cooled and solidified.

• Improvised Nuclear Device   A type of nuclear weapon that gives off four types of energy: a blast wave, intense light, heat, and radiation. The bomb dropped on Hiroshima, Japan, at the end of World War II is an example of nuclear device. Abbreviation:IND

• In-situ Recovery   A process to recover uranium in which fluids are injected into ground water to mobilize the uranium in underground deposits. Extraction wells then collect the groundwater, which is processed at the surface to recover the uranium.

• Ion   An atom or molecule that has too many or too few electrons, causing it to have an electrical charge.

• Ionization   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.

• Ionizing Radiation   Radiation with so much energy it can knock electrons out of atoms. Ionizing radiation can affect the atoms in living things, so it poses a health risk by damaging tissue and DNA in genes.

• Isotope   A form of an element that has the same number of protons but a different number of neutrons in the nucleus, giving it a different atomic mass. For example, uranium has thirty-seven different isotopes, including uranium-235 and uranium-238.  

• Karst   A type of terrain where there are numerous sinkholes and large voids such as caves. Karst is created when water dissolves rocks such as limestone, halite (salt) and gypsum.

• Linear No Threshold Model   The assumption that the risk of cancer increases linearly as radiation dose increases. This means, for example, that doubling the dose doubles the risk and that even a small dose could result in a correspondingly small risk. Using current science, it is impossible to know what the actual risks are at very small doses. Abbreviation:LNT

• Low-level Radioactive Waste   Radioactive waste that is not uranium or thorium mill tailings, transuranic waste, spent nuclear fuel, or high level waste. Low-level does necessarily not mean “low radioactivity.” Abbreviation:LLRW

• Maximum Contaminant Level   The amount of a contaminant allowed in public drinking water under the Safe Drinking Water Act (SDWA). Abbreviation:MCL

• Milling   Industrial operations that process ores to concentrate desired minerals. According to the Atomic Energy Act, uranium milling is any activity that results in generation of byproduct material during the production of special nuclear material.

• millirem   The millirem is the U.S. unit used to measure effective dose. One millirem equals 0.001 rem. The international unit is milliSievert (mSv). Abbreviation:mrem

• Mixed Waste   Mixed waste contains both radioactive and hazardous waste components.

• Naturally Occurring Radioactive Materials   Materials found in nature that emit ionizing radiation that have not been moved or concentrated by human activity. Abbreviation:NORM

• Non-ionizing Radiation   Radiation that has enough energy to move atoms or cause them to vibrate, but not enough to remove electrons. Examples of this kind of radiation are radio waves, visible light and microwaves.

• Overburden   Soil and rocks that have been moved out of the way to get to ore are called "overburden." In areas where there are high concentrations of radionuclides in the rock, overburden may have some enhanced radioactivity, but not enough to mine and process.

• Photon   A discrete "packet" of pure electromagnetic energy that has no mass and travels at the speed of light. Gamma and X-rays are photons.

• Picocurie   The picocurie is a U.S. unit used to measure radioactivity. One picocurie is one trillionth of a curie. Abbreviation:pCi

• Porosity   The capacity of soil or rock to hold water.

• Primordial   Existing since the formation of the solar system, naturally occurring.

• Radiation   Energy given off as either particles or rays.

• Radiation sickness   A serious illness that can happen when a person is exposed to very high levels of radiation, usually over a short period of time.

• Radioactive Decay   The process in which an unstable (radioactive) nucleus emits radiation and changes to a more stable isotope or element.

• Radioactivity   The emission of ionizing radiation released by a source in a given time period. The units used to measure radioactivity are becquerel (Bq) and curie (Ci).

• Radiogenic   Caused by ionizing radiation.

• Radioisotope   Radioactive forms of the same element, with the same number of protons but different number of neutrons. For example, Radium-228, Radium-226, and Radium-224 are radioisotopes of radium. Radioisotopes are a subset of radionuclides.

• Radiological Dispersion Device   A mix of explosives, such as dynamite, with radioactive powder or pellets. Also known as a dirty bomb. A radiological dispersal device is not a nuclear weapon. Abbreviation:RDD

• Radionuclide   Radioactive forms of elements are called radionuclides. Radium-226, Cesium-137, and Strontium-90 are examples of radionuclides.

• Raffinate   What is left behind after the more soluble portion of a material is removed. A liquid from which impurities have been removed by solvent extraction.

• Redox Potential   The measure of the tendency of a substance to acquire electrons (chemical reduction). Redox potential is measured in volts (V), or millivolts (mV).

• Remote-handled   A legal definition from the WIPP Land Withdrawal Act. Transuranic waste whose radioactive dose rate is 200 mrem per hour or greater. Drums of this waste are handled with special equipment.

• Risk   The probability of injury, disease or death from exposure to a hazard. Radiation risk may refer to all excess cancers caused by radiation exposure (incidence risk ) or only excess fatal cancers (mortality risk). Risk may be expressed as a percent, a fraction, or a decimal value. For example, a 1% excess... more

• Risk Assessment   An evaluation of the risk to human health or the environment from a hazard. Risk assessments may look at either existing hazards or potential hazards.

• Roentgen Absorbed Dose   The U.S. unit used to measure absorbed radiation dose (the amount of radiation absorbed by an object or person). The international equivalent is the Gray (Gy). One hundred rads are equal to 1 Gray. Abbreviation:rad

• Roentgen Equivalent Man   The U.S. unit to measure effective dose. The international unit is sieverts (Sv). Abbreviation:rem

• Shelter in Place   An emergency response instruction meaning get inside a building right away. If you can get to a brick or concrete multi-story building or basement within a few minutes, go there.

• Sievert   An international unit used to measure effective dose. The U.S. unit is rem. Abbreviation:Sv

• Slag   Byproduct left after a desired metal is thermally separated from its raw ore.

• Source Material   Uranium, thorium or any combination of them. Includes ores that contain, by weight, one-twentieth of 1 percent (0.05 percent), or more, of uranium, thorium, or any combination of them.

• Spent Nuclear Fuel   Fuel that has been withdrawn from a nuclear reactor after use. It is still highly radioactive.

• Statutory Authority   Responsibility and authority assigned by law to a governmental organization.

• Tailings   The remaining portion of a metal-bearing ore after some or all of a metal, such as uranium, has been extracted.

• Transuranic   Elements with atomic numbers higher than uranium (92). For example, plutonium and americium are transuranics.

• Transuranic Waste   Waste materials containing elements with atomic numbers higher than uranium (92) at concentrations greater than 100 nCi/g.

• Uncertainty   The inability to know for sure, often due to limitations in data. Identifying uncertainties helps define the limitations of a scientific study.

• X-Rays   A form of ionizing radiation made up of photons. X-rays are capable of passing completely through the human body. Medical x-rays are the single largest source of man-made radiation exposure.

• Yellowcake   The solid form of mixed uranium oxide, which is produced from uranium ore in the milling process. Its color can vary from yellow to orange to dark green. Yellowcake is processed into nuclear fuel.