ML20005A907
| ML20005A907 | |
| Person / Time | |
|---|---|
| Issue date: | 06/30/1981 |
| From: | Hanchett J, Hasselberg F, Singh M NRC OFFICE OF ADMINISTRATION (ADM), NRC OFFICE OF INSPECTION & ENFORCEMENT (IE), NRC OFFICE OF PUBLIC AFFAIRS (OPA) |
| To: | |
| References | |
| NUREG-0770, NUREG-770, NUDOCS 8107060001 | |
| Download: ML20005A907 (57) | |
Text
i NUREG-07/0 4
(
Glossary of Terms Nuclear Power and Radiation U.S. Nuclear Regulatory Csmmission Office of Public Affairs Office of Inspection and Enforcement Office of Administration Compilers: J. G. Hanchett, OPA, F. W. Hasselberg, ole Editor: M. H. Singh, ADM pn "ecoq, n
A i) s 53.'mj i s,
j i
e e
N PH s -
C b
bs JUN 3 01981 > r -
2 v L renu anaAton [o I
,Q
%s#
8107060001 810630?
0770 R y
N Available from GP0 Sales Program Division of Technical Information and Docu'aent Control U.S. Nuclear Regulatory Commission Washington, DC 20555 1
6
... - ~...
NUREG-07/0 Glossary of Terms Nuclear Power and Radiation Manuscript Completed: May 1981 Date Published: June 1981 Compilers: J. G. Hanchett, OPA, F. W. Hasseiberg, OIE Editor: M. H. Singh, ADM Office of Public Affairs Office of Inspection and Enforcement Office of Administration U.S. Nuclear Regulatory Comm!ssion Washington, D.C. 20555 ra f
'*w,,
?
5 e
'.,...../
l t
)
iii - Gloencry of Taran ABSTRACT This " Glossary of Terms: Nuclear Power and Radiation" is a compila-tion of words and concepts commonly used in the nuclear power field defined to assist the news media and members of the public in under-standing this often complex technology. The glossary was compiled by the NRC Office of Inspection and Enforcement and the Office of Public Affairs from a variety of internal and external sources. It is a part of the agency's response to a recommendation by the President's Commission on the Accident at Three Mile Island that government agencies, utility companies and the news media better prepare themselves to dis-seminate information to the public, in a form that is understandable.
i
v - Glonecry of Terma a
CONTENTS Page ABSTRACT............................................................
iii
. INTRODUCTION........................................................
1 DEFINITIONS.........................................................
3 SIMPLIFIED SCHEMATIC 0F BOILING WATER REACTOR (BWR) PLANT...............................................
47 SIMPLIFIED SCHEMATIC OF PRESSURIZED WATER i
REACTOR (PWR) PLANT...............................................
48 ELEMENTS AND ELEMENT ABBREVIATIONS..................................
49 PREFIXES............................................................
50 s:-
j
GLOSSARY OF TERMS Introduction The President's Commission on the Accident at Three Mile Island (the Kemeny Commission) made several recommendations under the general heading of "The Public's Right to Information." These recommendations were mainly concerned with the responsibility held by government agencies, utility companies and the news media to do a better job of dissewinating information to the public.
Among the reccamendations, the President's Commission stated that
" Federal and state agencies, as well as the utility, should make adequate 5
preparation'for a syste-stic public information program so that in time of a radiation-related emergency, they can provide timely and accurate infor-nation to the newa media and the public in a form that is understandable" (emphasis added).
The President's Commission also recommended that major media outlets and those other media, regardless of size, located near nuclear power plants, " hire and train specialists who have more than a passing famil-iarity with reactors and the language of radiation." Furthermore, the Commission added, reporters should discipline themselves "to place complex information in a context that is understandable to the public [ emphasis added] and that allows members of the public to make decisions regarding their health and safety."
As part of the U.S. Nuclear Regulatory Commission response to those recommendations, the Office of Inspection and Enforcement and the Office of Public Affairs have developed this " Glossary of Terms: Nuclear Power and Radiation" as part of the course material for an introductory seminar on nuclear power plants and radiation to be presented to the news media.
It is our first attempt to define in readily understandable language, a wide variety of terms and concepts commonly used in the disciplines related to nuclear power.
There is certainly no shortage of excellent scientific and technical dictionaries. However, most of them are compiled for scientists and engineers and are not sufficiently broad to cover the range of topics--
nuclear physics, radiation, nuclear reactor components and operations, fuel cycle, and health physics, to name a few--involved in a nuclear power plant.
We have therefore developed our own glossary, borrowing liberally from a variety of internal and external sources. We have attempted to redefine many of the terms and concepts in a way that will be under-standable to the news reporter and the layman.
In some instances, we suspect that our simplification--and, perhaps, oversimplification--of certain terms may offend some of our technical colleagues.
In other
Glenocry of Taras - 2 cases, the definitions may still be too technical. When the defini-tions include terms that are also defined elsewhere in the text, they are identified by underlining.
Our goal is to provide a useful start toward defining terms that are, at times, both complex and mystifying. The editors will welcome, from any source, comments and suggestions for additions, deletions, corrections and further clarification.and simplification of the terms defined in this glossary.
i
~.
a
3 - Glossary of Terms Definitions A
absorber Any material that absorbs or lessens the intensity of ionizing radiation. Neutron absorbers (like boron, hafnium, and cadmium) are used in control rods for reactors.
Concrete and steel absorb gamma rays and neutrons in reactor shields. A thin sheet of paper or metal will absorb or weaken alpha particles and all except the most energetic beta particles.
(See control rod; shielding.)
ab-orption The process by which the number of particles or photons entering a body of matter is reduced or attenuated by interaction with the matter.
(See neutron capture.)
access hatch An airtight door system that preserves the (air lock) pressure integrity of a reactor containment building while allowing access to personnel and equipment.
activation The process of making a material radioactive by bombardment with neutrons, protons, or other nuclear radiation.
(See induced radioactivity.)
activation products See induced radioactivity.
activity See radioactivity.
acute exposure See exposure.
acute radiation See radiation sicknees (syndrome).
sickness (syndrome) air lock See access hatch.
air sampling The collection and analysis of samples of air to measure its radioactivity or to detect the presence of radioactive substances, particulate matter or chemical pollutants.
ALARA Acronym for "As Low as Reasonably Achievable," a basic concept of radiation protection that specifies that radioactive discharges from nuclear plants and radiation exposure to perscanel be kept as far below regulation limits as feasible. The term was originally "As Low as Practicable."
Gl m cry of Tarm7 -4 A,
l alpha particle A positively charged particle ejected spontaneously from the nuclei of some radioactive elements.
It is identical to a helium nucleus that has a mass number of 4 and an electrostatic charge of
+2.
It has low-penetrating power and short range. The most energetic alpha particle will generally fail to penetrate the skin. Alphan are hazardous when an alpha-emitting isotope is introduced into the
- bcdy, anion Negatively charged ion.
(See ionization.)
atom The smallest particle of an element that cannot be divided or broken up by chemical means.
It consists of a central core called the nucleus, which contains protons and neutrons. Electrons revolve in orbits in the region surrounding the nucleus.
atomic energy Energy released in nuclear reactions. Of particular interest is the energy released when a neutron initiates the breaking up or fissioning of an atom's nucleus into smaller pieces (fission), or when two nuclei are joined together under millions of degrees of heat (fusion).
It is more correctly called " nuclear energy."
Atomic Energy Federal agency created in 1946 to manage the Commission (AEC) development, use and control of nuclear energy for military and civilian application. Abolished by the Energy Reorganization Act of 1974 and succeeded by the Energy Research and Development Administration (now part of the U. S. Department of Energy) and the U.S. Nuclear Regulatory Commission, atomic number The number of positively charged protons in the nucleus of an atom.
atomic weight See mass number.
attenuation See absorption.
auxiliary building Building at a nuclear power plant, frequently located adjacent to the reactor containment building, that houses most of the reactor
5 ' Glestery of T.res auxiliary ar.1 safety syst.;;.s, such as radio-active waste systems, chemical and volume control systems and emergency cooling water systess.
auxiliary feedwater Backup feedwater supply used during nuclear plant startup and shutdown; also known as emergency feedwater.
(See feedwater.)
4 f
i
)
i f
I
GI ss ry rf T^rms - 6 E
background radiation The radiation in man's natural environment, including cosmic rays and radiation from the naturally radioactive elements, both outside, and inside the bodies of humans and animels.
It is also called natural radiation. The usually quoted average individual exposure from background radiation is 125 millirem per year.
beta particle A charged particle emitted from a nucleus during radioactive decay, with a mass equal to 1/1837 that of a proton. A negatively charged beta particle is identical to an electron. A posi-Lively charged beta particle is called a positron.
Large amounts of beta radiation may cause skin burns, and beta emitters are harmful if they enter the body.
Beta particles are easily stopped by a thin sheet of metal or plastic.
binding energy The minimum energy required to separate a nucleus into its component neutrons and protons.
bioassay The collection and analysis of human hair, tissue, nasal smcars, urine or fecal samples to determine the amount of radioactive material that night have been ingested by the body.
biological halflife The time required for a biological system, such as that of a human, to eliminate by natural processes half the amount of a substance (such as a radioactive material) tbat has entered it.
biological shield A mass of absorbing material placed around a reactor or, radioactive source to reduce the radiation to a level safe for humans.
body burden The amount of radioactive material present in the body of a human or an animal.
boiling water reactor A reactor in which water, used as both coolant (BWP.)
and moderator, is allowed to boil in the core.
The resulting steam can be used directly to drive a turbine and electrical generator.
bone seeker A radioisotope that tends to accumulate in the bones when it is introduced into the body. An example is strontium-90, which behaves clemically like calcium.
~. _
Glensory of Taras - 7 E
breeder A reactor that produces more nuclear fuel than it, consumes. A fertile material, such as uranium-238, when bombarded by neutrons, is transformed into a fissile material, such as plutonium-239, which can be used as fuel. (See fissile, fissionable and fertile material.)
Btu A British thermal unit. The amount of heat required to change the temperature of one pound of water one degree Fahrenheit at sea level.
BWR A boiling water reactor.
l l
m,-
,,s.,
-.----..._-s
-.,,..-__y,
Gl+ -^ry cf T^rms - 8 s
(}
calibration The check or correction of the accuracy of a measuring instrument to assure proper operations 1 characteristics.
(See counter.)
cask A heavily shielded container used to store and/or ship radioactive materials. Lead and steel are common materials used in the manufacture of casks.
cation A positively charged ion.
(See ionization.)
chain reaction A reaction that stimulates its own repetition.
In a fission chain reaction, a fissionable nucleus absorbs a neutron and fissions, releasing addi-tional neutrons. These in turn can be absorbed by other fissionable nuclei, releasing still more neutrons. A fission chain reaction is self-sus-taining when the number of neutrons released in a given time equals or exceeds the number of neutrons lost by absorption in nonfissionable material or by escape from the system.
charged particle An ion. An elementary particle carrying a positive or negative electric charge.
chemical compound See compound.
chemical Following an ionization event, the positive and recombination negatively charged ion pairs may or may not re-align themselves to form the same chemical sub-stance they formed before Loriz? tion. Thus, chemical recombination could change the chemical j
composition of the material bombarded by radiation.
The h pothetical result of a power reactor core China syndrome i
melt accident in which molten fuel melts through the reactor pressure vessel and the buttom of the containment building and into the earth "all the way to China."
chronic exposure See exposure.
cladding The thin-walled metal tube that forms the outer jacket of a nuclear fuel rod.
It prevents corrosion of the fuel by the coolant and the release of fission products into the coolant.
Aluminum, stainless steel and zirconium alloys are common cladding materials.
9 - Gleannry of Tarma E
cleanup system A system used for continuously filtering and demineralizing the reactor coolant system to reduce contamination levels and minimize corrosion.
coastdown An action that permits the reactor power level to decrease gradually as the fuel in the core is depleted.
cold shutdown The term used to define a reactor coolant system at atmospheric pressure and at a temperature below 212*F following a reactor cooldown.
(See control rod.)
compound A chemical combination of two or more elements combined in a fixed and definite proportion by weight.
condensate Water that has been produced by the cooling of steam in a condenser.
condenser A large heat exchanger designed to cool exhaust steam from a turbine below the boiling point so that it can be returned to the heat source as water.
In a pressurized water reactor, the water is returned to the steam generator.
In a boiling water reactor, it returns to the reactor core.
The heat removed from the steam by the condenser is transferred !.o a circulating water system and is exhausted to the environment, either through a cooling tower or directly into a body of water.
(See cooling tower.)
contamination The deposition of unwanted _-adioactive material on the surfaces of structures, areas, objects, or personnel.
containment The provision of a gastight shell or other enclosure around a reactor to confine fission piaducts that otherwise might be released to the atmosphere in the event of an accident.
control rod A rod, plate or tube containing a material such as hafnium, boron, etc., used to control the power of a nuclear reactor. By absorbing neutrons, a control rod prevents the neutrons from causing further fission.
(See poison.)
Gle w.ry ef Tarms - 10 E
controlled area A defined area in which the occupational exposure of personnel to radiation or radioactive material is under the supervision of an individual in charge of radiation protection.
control room The area in a nuclear power plant from which (building)'
most of the plant power production and emer-gency safety equipment can be operated by remote control.
coolant A substance-circulated through a nuclear reactor to remove or transfer heat. The most commonly used coolant in the United States is water. Other coolants include heavy water, air, carbon dioxide, helium, liquid sodium and sodium potassium alloy.
cooldown The gradual decrease in reactor fuel rod tempera-ture caused by the removal of heat from the reactor coolant system.
cooling tower A heat exchanger designed to aid in the cooling of water that was used to cool exhaust steam exiting the turbines of a powet plant. Cooling towers transfer exhaust heat into the air instead of into a body of water.
core The central portion of a nuclear reactor contain-ing the fuel elements, moderator, neutron poisons and support structures.
core melt accident See China syndrome Penetratingionizingradiation,kbothparticulate cosmic radiation and electromagnetic, originating in outer space.
Secondary cosmic rays, formed by interactions in the earth's atmosphere, account for about 45 to 50 millirem of tne 125 millirem background radia-tion that an average individual receives in a year.
counter A general designation applied to radiation detection instruments or survey meters that detect and measure radiation. The signal that announces an ionization event is called a count.
(See Geiger-Mueller counter.)
critical mass The smallest mass of fissionable materisl that will support a self-sustaining chain reaction.
11 - Glocenry of Term 7 critical organ The body organ receiving a radionuclide or rad-iation dose that results in the greatest overall damage to the body.
criticality A term used in reactor physics to describe the state when the number of neutrons released by fission is exactly balanced by the neutrons being absorbed (by the fuel and poisons) and escaping the reactor core. A reactor-is said to be " critical" when it achieves a self-sustaining nuclear chain reaction.
crud A colloquial term for corrosion and wear products (rust particles, etc.) that become radioactive under a radiation flux.
(See induced radio-activity.)
cumulative dose The total dose resulting from repeated exposures of radiation to the same region, or to the whole body, over a period of time, curie The basic unit used to describe the intensity of (Ci) radioactivity in a sample of material. The curie is equal to 37 billion disintegrations per second, which is approximately the rate of decay of I gram of radium. A curie is also a quantity of any radionuclide that decays at a rate of 37 billion disintegrations per seccnd. Named for Marie and Pierre Curie, who discovered radium in 1898.
l
--g
~v,,-y--
m e.i-r, r-.,wmegm, p
v-w y-
3-&gwv.-
-av-.
mi.
-w
G1c - ry cf Tmrma _12 D
daughter products Isotopes that are formed by the radioactive decay of some other isotope.
In the case of radium-226, for example, there are 10 successive daughter products, ending in the stable isotope lead-206.
decay heat The heat produced by the decay of rad oactive fission products after the reactor has been shut down.
(See residual heat.)
decay, radioactive The decrease in the amount of any radioactive material with the passage of time, due to the spontaneous emission from the atomic nuclei of either alpha or beta particles, often accompanied by gamma radiation.
(See halflife; radioactive.)
deconter'n= tion The reduction or removal of contaminating radio-active material from a structure, area, object, or person. Decontamination may be accomplished by (1) treating the surface to remove or decrer
- he contamination; (2) letting the material stai.,
o that the radioactivity is decreased as a result of natural decay; ano (3) covering the contamination to shield or attenuate the radiation emitted.
depleted uranium Uranium having a percentage of uranium-235 smaller than the 0.7% found in natural uranium.
It is obtained from spent (used) fuel elements or as by-product tails, or residues, from uranium isotope separation.
(See mill tailings.)
design-basis A postulated accident that a nuclear facility accident must be designed and built to withstand with-out loss to the systems, structures and coa-ponents necessary to assure public health and safety.
design-basis Earthquakes, tornadoes, hurricanes, floods, phenomena etc., that a nuclear facility must be designed and built to withstand without loss to the systems, structures, and componerds necessary to assure public health and safety.
(See seismic Category I.)
detector A material or device that is sensitive to radiation and can produce a response signal suitable for measurement or analysis. A radiation detection instrument.
(See counter.)
deuterium An isotope of hydrogen with one prot'>n and one neutron in the nucleus.
(See heavy water.)
1 13 - Glossery of Terra D
deut 2ron The nucleus of deuterium.
It contains one proton and one neutron, differential pressure The difference in pressure between two points of a (DP) system, such as between the inlet and outlet of a
- pump, disintegration See decay, radioactive.
Doppler coefficient See fuel temperature coefficient of reactivity, dose A quantity (total or accumulated) of ionizing radiation received. The term " dose" is often used in the sense of the exposure dose, expressed in roentgens, which is a measure of the total amount of ionization that the quantity of radiation could produce in air. This should be distinguished from the absorbed dose, given in rads, that represents the energy absorbed from the radiation in a gram of any material. Furthermore, the bio-logical dose, given in rem, is a measure of the biological damage to living tissue from the radia-tion exposure, dose equivalent A term used to express the amount of effective radiation when modifying factors have been con-sidered. The product of absorbed dose multiplied by a quality factor multiplied by a distribution factor.
It is expressed numerically in rem.
dosimeter A portable instrument for measuring and registering the total accumulated exposure to ionizing radiation.
(See dosimetry.)
dosimetry The theory and application of the principles and techniques involved in the measurement and recording of radi,atio'n doses.
Its practical aspect is concerned with the use of various types of radiation instruments with which measurements are made.
(See film badge; survey meter.)
dose rate The radiation dose delivered per unit of time.
Measured, for example, in rem per hour.
drywell The containment structure enclosing a boiling water reactor vessel and its recirculation system.
The drywell provides both a pressure suppression system and a fission product barrier under accident conditions.
Gle m ry ef T;rmi - 14 E
effective halflife The time required for the amount of a radioactive element deposited in a living organism to be diminished 50 percent as a result of the combined action of radioactive decay and biological elimination.
(See biological halflife.)
efficiency, plant The percentage of the total energy content of a power plant's fuel that is converted into elec-tricity. The remaining energy is lost to the environment as heat.
eldctrical generator An electromagnetic device that converts mechanical (rotational) energy into electrical energy. Most large electrical generators are driven by steam or water turbine systems.
electromagnetic A traveling wave motion resulting from changing radiation electric or magnetic fields. Familiar electro-magnetic radiations range from X-rays (and gamma rays) of short wavelength, through the ultra-violet, visible, and infrared regions, to radar and radio waves of relatively long wavelength.
All electromagnetic radiations travel in a vacuum with the velocity of light.
(See photon.)
electron An elementary particle with a unit negative charge and a mass 1/1837 that of the proton.
Electrons surround the positively charged nucleus and determine the chemical properties of the atom.
(See beta particle.)
element One of the 103 known chemical substances that cannot be broken down further without changing its chemical properties. Some examples include hydrogen, nitrogen, gold, lead and uranium.
l emergency core Reactor system components (pumps, valves, heat l
cooling system exchangers, tanks and piping) that are specific-
[ECC(S)]
ally designed to remove residual heat from the reactor fuel rods should the normal core cooling system (reactor coolant system) fail.
emergency feedwater See auxiliary feedwater.
enrichment See isotopic enrichment.
excursion A sudden, very rapid rise in the power level of a reactor caused by supercriticality. Excursions l
l
15 - Gle::nry cf Terma E
are usually quickly suppressed by the negative temperature coefficient, the fuel temperature coefficient or the void coefficient (depending on reactor design), and by rapid insertion of control rods.
exposure The absorption of radiation or ingestion of a r$_".o nuclid e. Acute exposure is generally accepted to be a large exposure received over a short period of time. Chronic exposure is expisur.: received during a lifetime.
(See dose.)
external radiation Exposure to ionizing radiation when the radiation source is located outside the body.
extremities The hands and forearms and, with restrictions, the head, feet, and ankles.
(Permissible radiation exposures in these regions are generally greater than in the whole body because they contain less blood-forming material and have smaller volumes for energy absorption.)
4
G1 m ry of T;rm7 - 16 E
fast fission Fission of a heavy atom (such as uranium-238) when it absorbs a high-energy (fr.st) neutron. Most fissionable materials need thermal (slow) neutrons in order to fission.
fast neutron A neutron with kinetic energy greater than its surroundings released during fission.
D fast reactor A reactor in which the fission chain reaction is sustained primarily by fast neutrons rather than by slow-moving neutrons.
Fast reactors contain little or no moderator to slow down the neutrons from the speeds at which they are ejected from fissioning nuclei.
feedwater Water supplied to the reactor pressure vessel (in a BWR) or the steam generator (in a PWR) that removes heat from the reactor fuel rods by boiling and becoming steam. The steam becomes the driving force for the plant turbine generator.
fertile material A material, which is not itself fissile (fis-sionable by thermal neutrons), that can be con-verted into a fissile material by irradiation in a reactor. There are two basic fertile materials, uranium-238 and thorium-232. When these fertile materials capture neutrons, they are couverted into fissile plutonium-239 and uranium-233, respectively.
film Eadge A pack of photographic film used for approximate measurement of radiation exposure for personnel monitoring purposes. The badge may contain two or three films of differing sensitivity, and it may contain a filter that shields part of the film from certain types of radiation.
fissile material Although sometimes used as a synonym for fission-able material, this term has acquired a more restricted meaning; namely, any material fissionable by thermal (slow) neutrons. The three primarily fissile materials are uranium-233, uranium-235 and plutonium-239.
fission The splitting of a nucleus into at least two other nuc1ci and the release of a relatively large amount of energy. Two or three neutrons are usually re-leased during this type of transformation.
4 17 - Glonnery of Term 3 L
fission gases Those fission products that exist in the gaseous state. Primarily the noble gases (krypton, xenon, radon, etc.).
fission products The nuclei (fission fragments) formed by the fission of heavy elements, plus the nuclides formed by the fission fragments' radioactiie
' decay.
fissionable material Commonly used as.a synonym for fissile material, the meaning of this term has been extended to include material that can be fissioned by fast neutrons, such as uranium-238.
5 flux A term applied to the amount of some type of radiation crossing a certain area per unit time.
The unit of flux is the number of particles, energy, etc., per square centimeter per second, fuel assembly A cluster of fuel rods (or plates). Also called a fuel element. Many fuel assemblies make up a reactor core.
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 a reactor, chemical reprocessing to recover the fissionable material remaining in the spent fuel, reenrichment of the fuel material, refabrication into new fuel elements, and waste disposal.
fuel element See fuel assembly.
l fuel reprocessing The processing of reactor fuel to separate the unused fissionable material from waste material.
fuel rod A long, slender tube that holds fissionable material (fuel) for nuclear reactor use. Fuel rods are assembled into bundles called fuel elements or fuel assemblies, which are loaded individually into the reactor core.
fuel temperature The physical property of fuel pellet material coefficient of (uranium-238) that causes the uranium to absorb reactivity more neutrons away from the fission process as fuel pellet temperature increases. This acts to stabilize power reactor operations. Also known as the Doppler coefficient.
. - -. - - -., _ -. -. -. -. ~. -.,. -,.. - - -. - _... _ -. _ _.
m Glerrary of Tiro 1 - 18 E
fusion (thermo-A nuclear reaction characterized by joining nuclear reaction) together of light nuclei to form heavier nuclei, the energy for the reactic as being provided by violent thermal agitation of particles at very high temperatures.
If the colliding particles are properly chosen and the agitation is violent enough, there will be a release of energy from the reaction. The energy of the stars is derived from such reactiona.
l l
l l
r
19 - Glo:Sc ry o f Ta rm7 gap The space inside a reactor fuel rod that exists between the fuel pellet and the fuel rod cladding, gamma ray High-energy, short wavelength electromagnetic (gamma radiation (a packet of energy) emitted from the radiation) nucleus.
Gamma radiation frequently accompanies alpha and beta emissions and always accompanies fission. Gamma rays are very penetrating and are best stopped or shielded against by dense mate-rials, such as lead or uranium.
Gamma rays are similar to X-rays, but are usually more energetic.
gas-cooled reactor A nuclear reactor in which a gas is the coolant.
gases Normally formless fluids that completely fill the space and take the shape of their container.
gaseous diffesion A method of isotopic separation based on the fact (plant) that gas atoms or molecules with different masses will diffuse through a porous barrier (or membrane) at different rates. This method is used to sepa-rate uranium-235 from uranium-238; it requires large gaseous dif fusion plants and enormous amounts of electric power.
Geiger-Mueller A radiation detection and measuring instrument.
counter It consists of a gas-filled tube containing elec-trodes, between which there is an electricel 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 radiation.
It was named for Hans Geiger and W. Mueller who invented it in the 1920s.
It is sometimes called simply a Geiger counter, or a G-M counter.
graphite A form of carbon, similar to the lead used in pencils, used as a moderator in some nuclear reactors.
Glewry ef Tarms - 20 E
halflife The time in which half the atoms of a particular radioactive substance disintegrate to another nuclear form. Measured halflives vary from mill-ionth of a second to billions of years. Also called physical halflife.
- halflife, The time required for the body to eliminate half biological of the material taken in by natural biological means.
- halflife, The time required for a radionuclide contained in effective a biological system, such as a human or an animal, to reduce its accivity by half as a combined result of radioactive decay and biological elimination.
half-thickness The thickness of any given absorber that will reduce the intensity of a beam of radiation to one-half its initial value.
(See attenuation; shielding.)
head, reactor vessel The removable top section of a reactor pressure vessel.
It is bolted in place during power oper-ation and removed during refueling to permit access of fuel-handling equipment to the core.
health physfes The science concerned with recognition, evalu-ation and control of health hazards from ionizing radiation.
heat exchanger Any device that transfers heat from one fluid (liquid or gas) to another fluid or to the environment.
heat sink Anything that absorbs heat; usually part of the environment, such as the air, a river or outer space.
heatup The rise in temperature of the reactor fuel rods resulting from an increase in the rate of fission in the core.
heavy water Water containing significantly more than the (D 0) natural proportions (one in 6500) of heavy hydro-2 gen (deuterium) atoms to ordinary hydrogen atoms.
Heavy water is used as a moderator in some reactors because it slows down neutrons effec-tively and also has a low probability for absorp-tion of neutrons.
l 21 - G1connry of Tarms E
heavy-water-moderated A reactor that uses heavy water as its moderator, reactor Heavy water is an excellent moderator and thus permits the use of inexpensive (unenriched) uranium as a fuel.
high radiation area Any area in which a major portion of the body could receive a radiation dose of 100 millirem (0.1 rem) in one hour. These areas must be posted as "high radiation areas" and access into these areas is maintained under strict control.
hot A collaquial term meaning highly radioactive.
hot spot The region in a radiation / contamination area in which the level of radiation / contamination is noticeably greater than in neighboring regions in the area.
l i
l
GL vry cf T:rms - 22 1
induced Radioactivity that is created when stable sub-radioactivity stances are bombarded by ionizing radiation.
For example, the stable isotope cobalt-59 becomes the radiactive isotope cobalt-60 under neutron bombardment.
internal radiation Nuclear radiation resulting from radioactive substances in the body.
Some examples are iodine-131 found in the thyroid gland, and strontium-90 and plutonium-239 found in bone.
ion An atom that has too many or too few electrons, causing it to be chemically active; an electron that is not associated (in orbit) with a nucleus.
(See ionization.)
ionization The process of adding one or more electrons to, or removing one or more electrons from, atoms or molecules, thereby creating ions.
High tempera-tures, electrical discharges, or nuclear radia-tions can car m ionization.
ionization chamber An instrument that detects and measures ionizing radiation by measuring the electrical current that flows when radiation ionizes gas in a chamber, making the gas a conductor of electricity.
(See counter.)
ionizing radiation Any radiation capable -f displacing electrons from atoms or molecules, thereby producing ions.
Examples:
alpha, beta, gamma, X-rays, neutrons and ultraviolet light.
High doses of ionizing radiation may produce cevere skin or tissue damage.
irradiation Expanure to radiation.
isotone One of several different nuclides having the same number of neutrons in their nuclei.
isotope One of two or more atoms with the same number of protons, but different numbers of neutrons in their nuclei. Thus, carbon-12, carbon-13 and carbon-14 are isotopes of the element carbon, the numbers denoting the approximate atomic weights.
Isotopes have very nearly the same chemical properties, but often different physical properties (for example, carbon-12 and -13 are stable, carbon-14 is radio-active.
23 - Glossary of Terms 1
isotope separation The process of separating isotopes from one another, or changing their relative abundances, as by gaseous diffusion or electromagnetic separation.
Isotope separation is a step in the isotopic enrichment process.
isotopic enrichment A process by which the relative abundances of the l
isotopes of a given element are altered, thus producing a form of the element that has been enriched in one particular isotope and depleted in its other isotopic forms.
I u
I j
i Ibhi l
l 1
l l
l l
E kilo-A prefix that multiplies a basic unit by 1000.
Example:
I kilometer = 1000 meters.
kilovolt The unit of electrical potential equal to 1000 l
(kV) volts.
kinetic energy The energy that a body possesses by virtue of its mass and velocity; the energy of motio.
l l
Glessnry cf T rms - 24 L
LD 50/30 The dose of radiation expected to cause death within 30 days to 50 percent of those exposed.
Generally accepted to range from 400 te 450 rem received over a short period of time [also known as lethal dose (LD)].
light water Ordinary water (H O) as distinguished frr3 heavy 2
water (D 0).
2 light-water reactor A term used to designate reactors using ordinary water as coolant, including boiling water reactors (BWRs) and pressurized water reactors (PWRs), the most common types used in the United States.
loop In a pressurized water reactor, the coolant flow path through piping from the reactor pressure vessel to the steam generator, to the reactor coolant pump, and back to the reactor pressure vessel. Large PWRs may have as many as four separate loops.
low population zone An area of low population density often required (LPZ) around a nuclear installation. The number and density of residents is of concern in emergency planning so that certain protective measures (such as notification and instructions to resi-dents) can be accomplished in a timely manner.
T I
25 - Glo snry of Tarma E
mass-energy equation The equation developed by Albert Einstein which 2
is usually given as E = mc, slowing that, when the energy of a body changes by an amount E (no matter what form the 2nergy takes), the mass, m, 2
of the body will change by an amount equal to E/c,
2 The factor c, the square of the speed of light in a vacuum, may be regarded as the conversion factor relating units of mass and energy. The equation predicted the possibility of releasing enormous amounts of energy by the conversion of mass to energy.
It is also called the Einstein equation.
mass number The number of wieleons (neutrons and protons) in the nucleus of an atom. Also known as the atomic weight of an atom.
mega-A prefix that multiplies a basic unit by 1,000,000, megacurie One million curies.
(See curie.)
micro-A prefix that divides a basic unit into one million parts.
microcurie A one-millionth part of a curie.
(See curie.)
microsecond A one-millionth part of a second.
mill tailings Naturally radioactive residue from the processing of urarium ore into yellowcake in a mill. Although the milling process recovers about 93 percent of the uranium, the residues, or tailings, contain several radioactive elements, including uranium, thorium, radium, polonium and radon.
milli-A prefix that divides a basic unit by 1000.
millirem A one-thousandth part of a rem.
(See rem.)
milliroentgen A one-thousandth part of a roentgen.
(See roentgen.)
moderator A material, such as ordinary water, heavy water, or graphite, used in a reactor to slow down high-velocity neutrons, thus increasing t'ne likelihood of fission.
moderator temperature The property of a reactor moderator to coefficient of slow down fewer neutrons as its temperature reactivity increases. This acts to stabilize power reactor operations.
Glossary of Terms - 26 E
molecule A group of atoms held together by chemical forces.
A a,lecule is the smallest unit of a cumpound that can exist by itself and retain all its chemical properties.
monitoring Periodic or continuous determination of the amount of ionizing radiation or radioactive contamination present in an occupied regiota, as a safety measure, for purposes of health protection.
(See radio-logical survey.)
27 - Glonenry of Terms N
nano-A prefix that divides a basic unit by one billion.
nanocurie One billionth part of a curie.
natural radiation See background radiatien.
natural uranium Uranium as found in nature.
It contains 0.7 per-cent uranium-135, 99.3 percent uranium-238 and a trace of uranium-234, negative temperature See moderator temperature coefficent.
coefficient neutron An uncharged elementary particle with a mass slightly greater than that of the proton, and found in the nucleus of every atom heavier than hydrogen.
neutron capture The procesr in which an atomic nucleus absorbs or captures a neutron.
neutron chain A process in which some of the neutrons released reaction in one fission event cause other fissions to occur.
There are three types of chain reactions:
(1) Nonsustaining chain reaction--An average of less than one fission is produced by the f
neutrons released by each previous fissicn (reactor suberiticality.)
(2) Sustaining chain reaction--An average of exactly one fission is produced by the neutrons released by each previous fission (reactor criticality.)
(3) Multiplying chain reaction--An average of more than one fission is produced by the neutrons released by previous fission (reactor super-cricitality.)
neutron generation The release, thermalization and absorption of fission neutrons by a fissile material and the fission of that material producing a second generation of neutrons.
In a typical reactor system, there are about 40,000 generations of neutrons every second.
neutron leakage Neutrons that escape from the vicinity of the fissionable material in a reactor core. Neutrons that leak out of the fuel region are no longer
Glossary of Teres - 28 E
available to cause fission and must be absorbed by shielding placed around the reactor pressure vessel for that purpose.
reutron, slow See neutron, thermal.
neutron source A radioactive material (decays by neutron emission) that can be inserted into a reactor to ensure that a sufficient quantity of neutrons is available to start a chain reaction and register on neutron detection equipment.
neutron, thermal A neutron that has (by collision with other particles) reached an energy state equal to that of its surroundings.
(See thermalization.)
noble gas A gaseous chemical element that does not readily enter into chemical combination with other elements. An inert gas.
(See fission gases.)
non-vital plant Systems at a nuclear facility that may or may systems not be necessary for the operation of the faci-lity (i.e., power production), but that would have little or no effect on public health and safety should they fail. These systems are not g
safety related.
nozzle As used in PWRs and BWRs, the interface for fluid (inlet or outlet) between reactor plant components (pressure vessel, coolant pumps, steam generators, etc.) and their associated piping systems, nuclear disintegratie-See decay, radioactive, nuclear energy The energy liberated by a nuclear reaction (fission or fusion) or by radioactive decay.
nuclear fission See fission.
I nuclear force A powerful short-ranged attractive force that holds together the particles inside an atomic nucleus.
nuclear fusion See fusion.
29 - Glcancry of Tc;res E
nuclear power plant An electrical generating facility using a nuclear reactor as its power (heat) source.
nuclear radiation See _ radiation, nuclear, nuclear reaction See reaction, nuclear.
nuclear reactor See reactor, nuclear, nucleon Common name for a constituent particle of the atomic nucleus. At present, applied to protqta and neutrons but may include any other particles found to exist in the nucleus, nucleus (or atomic The small, central, positively charged region of nucleus);
an atom that carries essentially all the mass.
nuclei (plural)
Except for the nucleus of ordinary (light) hydrogen, which has a single proton, all atomic nnelei contain both protons and neutrons. The number of protons determines the total positive charge, or atomic number; this is the same for all the atomic nuclei of a given chemical element.
The total number of neutrons and protons is called the mass number.
(See isotope.)
nuclide A general. term referring to all known isotopes, both stable (279) and unstable (about 5000), of the chemical elements.
l I
l l
,-e
...-r,,
Glossary of Teres - 30 9
s operating basis An earthquake that could be expected to. affect earthquake the plant site, but for which the plant power production equipment is designed to remain functional without undue risk to public health and safety.
(See design-basis phenomenon.)
oralloy Uranium enriched in the isotope uranium-235.
This material is an excellent fission fuel and is capable of sustaining a chain reaition.
1 1
31 - Glo7cary of Terc, P
parent A radionuclide that upoa radioactive decay or disintegration yields a specific nuclide (the daughter).
parts per million Parts (molecules) of a substance contained in a (ppm) million parts of air (or water) by volume.
pellet, fuel As used in PWRs and BWRs, a pellet is a small cylinder approximately 3/8-inch in diameter and 5/S-inch in length consisting of uranium fuel in a ceramic form--uranium dioxide, UO. Typi-2 cal fuel pellet enrichments range from 2 to 3.5 percent uranium-235.
periodic table An arrangement of chemical elements in order of increasing atomic number. Elements of similar properties are placed one under the other, yielding groups or families of elements. Within each group, there is a variation of chemical and physical properties, but in general there is a similarlty of chemical behavior within each group.
personnel monitoring The determination of the degree of radioactive contamination on individuals using survey aeters, or the determination of radiation dosage received by means of dosimetry devices.
photodosimetry The determination of the cumulative dose of ionizing radiation by use of photographic film.
photon A quantum (or packet) of energy emitted in the y4 form of electromagnetic radiation. Gamma rays g
and X-rays are examples of photons.
pico-A prefix that divides a basic unit by one trillion.
picoeurie One trillionth part of a curie.
pig A container (usually lead) used to ship or store radioactive materials. The thick walls protect the person handling the container from radiation. Large containers are commonly called casks.
pile A nuclear reactor; called a pilt because the earliest reactors were " piles" of graphite and uranium blocks.
l t
G1 ry of T rms - 32 P
plutonium A heavy, radioactive, manmade metallic element (Pu) with atomic number 94.
Its most important isotope is fissile plutonium-239, which is produced by neutron irradiation of uranium-238.
pocket dosimeter A small iontzation detection inctrument that indicates radiation exposure directly. An auxiliary charging device is usually necessary.
poison In reactor physics, a material other than fission-able material in the vicir.ity of the reactor core that will absorb neutrons. The addition of poisons, such as control rod _s or boron, into the reactor is said to be an addition of negative reactivity.
pool reactor A reactor in which the fuel elements are suspended in a pool of water that serves as the reflector, moderator and coolant. Popularly called a
" swimming pool reactor," it is used for research and training, not for electrical generation.
positron Particle equal in mass, but opposite in charge, to the electron; a positive electron.
power reactor A reactor designed to produce heat for electric generation, as distinguished from reactors used for research, for producing radiation or fission-able materials, or for reactor component testing.
pressure vessel A strong-walled container housing the core of D
most types of power reactors; it usually also contains the moderator, neutrcn reflector, I
thermal shield and control rods.
pressurized water A power reactor in which heat is transferred reactor from the core to a heat exchanger by high-(PWR) temperature water kept under high pressure in the primocy system. bteam is generated in a secondary circuit. Many reactors producing electric power are pressurized water reactors.
pressurizer A tank or vessel that acts as a head tank (or
[
surge volume) to control the pressure in a i
pressurized water reactor.
primary system See reactor coolant syster.
I
33 - G1 cam ry of Tarma i.
E proportional counter An instrument in which an electronic detection system receives pulses that are proportional to
.the number of ions formed in a gas-filled tube by ionizing radiation.
proton An eleser.tary nuclear particle with a positive electric charge located in the nucleus of an atom.
(See atomic number.)
PWR A pressurized water reactor.
I F
I I
I l
l I
t I
l I
t i
'h-
.,e.
.,,...,n-,
,.--=e..,
Glossary of Terms - 34 9
quality factor The factor by which the absorbed dose is to be multiplied to obtain a quantity that expresses, on a common scale for all ionizing radiations, the biological damage to exposed persons.
It is used because some types of radiation, such as alpha particles, are s' ore biologically damaging than other types.
quantum theory The concept that er.ergy is radiated intermittently in units of definite. magnitude called quanta, and absorbed in a like manner.
(See photon.)
9
'i 1
l l
-i. i..,,,,,
l e,
35 - Glotscry cf Term 3 E
rad Acronym for radiation absorbed dose. The basic unit of absorbed dose of radiation.
A dose of one rad means the absorption of 100 ergs (a small but measurable amount of energy) per gram of absorbing material.
radiac An acronym derived from " radioactivity detection indication and computation." a generic term applying to radiological instruments or equipment, radiation, nuclear Particles (alpha, beta, neutrons) or photons (gamma) emitted from the nucleus of an unstable (radioactive) atom as a result of radioactive decay.
I radiation area Any accessible area in which the level of radia-tion is such that a major portion of ar individ-ual's body could receive in any one hour a dose.
in excess of 5 millirem, or in any five conse-cutive days a dose in excess of 100 millirem.
radiation detection A device that detects and records the chare.c-instrument teristics of ionizing radiation.
(See counter.)
radiation monitoring See monitoring.
radiation shielding Reduction of radiation by interposing a shield of absorbing material between any radioactive source and a person, work area or radiation-sensitive device.
radiation sickness The complex of symptoms characterizing the disease (syndrome) known as radiation injury, resulting from exces-sive exposure of the whole body (or large part) to ionizing radiation. The earliest of these symptoms are nausea, fatigue, vomiting, and diarrhea, which may be Zollowed b, loss of hair (epilation), hemorrhage, inflamation of the mouth and throat, and general loss of energy.
In severe cases, where the radiation exposure has been relatively large, death may occur within two to four weeks. Those who survive 6 weeks after the receipt of a single large dose of radiation may generally be expected to recover.
radiation source Usually a manmade sealed source of radiation used in teletherapy, radiography, as a power t
source for batteries, or in varior.A +.ypes of
^ l Gle m ry cf Tarm7 - 36 E
industrial gauges. Machines such as accelerators tad radioisotope generators and naturai radio-nuclides may be considered sources.
radiation standards Exposure standards, permissible concentrations, rules for safe handling, regulations for trans-portation, regulations for industrial control of radiation and control of radioactive material by legislative means.
radiation syndrome See radiation sickness (syndrome).
radiation warning An officially prescribed symbol (a magenta symbol trefoil) on a yellow background that must be displayed where certain quantitiep of radio-active materials are present or tihere certain doses rf radiation could be reccived.
radioactive Exhibiting radioactivity or pertaining to radio-activity.
radioactive Deposition of rsdioactive material in any place contamination where it mav 'aarm persons or equipment, radioactive isotope A radioist.toge.
1 radioactive series A succession of nuclides, each of which transforms by radioactive disintegration into the next until a stable nuclide results. Tne first member is called the parent, the intermediate members are called daughters, and the final stable member is called the end product.
radioactive waste See waste, radioactive.
radioactivity The spontaneoun emission of radiation, generally
,'I alpha or beta particles, often accompanied by gamma rays, from the nuclees of an unstable
)
isotope.
radiography The making of shadow images on photographic film by the action of ionizing radiation.
radioisotope An unstable isotope of an clement that decays or disintegrates spontaneously, emitting radiation.
Approximately 5000 natural and artificial radio-isotopes have been toentified.
37 - Glossary of Terms R
radiological survey The evaluation of the radiation hazards accom-panying the production, use, or existence of radioactive materials under a specific set of conditions. Such evsluation customarily includes a physical survey of the disposition of materials and equipment, measurements or estimates of the levels of radiation that may be involveu, and a sufficient knowledge of processes affecting these materials to predict hazards resulting from expected or possible changes in materials or equipment.
radiology That branch of medicine dealing with the diag-nostic and therapeutic applications of radiant energy, including X-rays and radioisotopes.
radionuclide A radioisotope.
radiosensitivity The relative susceptibility of cella, tissues, organs, organisms, or other substances to the
, 3 injurious action of radiation.
radium A radioactive metallic element with atomic (Ra) number 88.
As found in nature, the most common isotope has a mass number of 226.
It occurs in minute quantities associated with uranium in pitchblend, carnotite and other minerals.
radon A radioactive element that is one of the heaviest (Rn) gases known.
Its atomic number is 86, and its mess number is 222.
It is a daughter of radium.
reaction Any process involving a chemical or nuclear change.
reactivity A term expressing the departure of a reactor system from criticality. A positive reactivity addition indicates a move toward supercriticality (power increase). A negative reactivity addition indicates a move toward suberiticality (power decrease).
reactor coolant The cooling system used to remove energy from the system reactor core and transfer that energy either directly or indirectly to the steam turbine.
reactor, nuclear A device in which nuclear fission may be sustained and controlled in a self-supporting nuclear reaction. The varieties are many, but all incor-porate certain features, including fissionable material or fuel, a mcderating material (unless C
Glerrery ef Taras - 38 1
I R
the reactor is operated on fast neutrons), a reflector to conserve escaping neutrons, pro-visions for removal of heat, measuring and con-trolling instruments, and protective devices.
recycling The reuse of fissionable-material after it has been recovered by chemical processing from spent
- o. depleted reactor fuel, reenriched and then refabricated into new fuel elements, reflector A layer of material immediately surrounding a reactor core that scatters back (or reflects) into the core many neutrons that-would otherwise escape.
The returned neutrons can then cause more fissions and improve the neutron economy of the reactor.
Common reflector materials are graphite, beryllium, water and nattral uranium.
t rem Acronym of roentgen equivalent man.
The unit of dose of any ionizing radiation that produces the same biological effect as a unit of absorbed dose of ordinary X-rays.
(See quality factor.)
reprocessing See recycling.
restricted area Any area to which access is controlled for the protection of individuals from exposure to radiation and radioactive materials.
roentgen A unit of exposure to ionizing radiation.
It is (r) that amount of gamma or X-rays required to produce ions carrying 1 electrostatic unit of electrical charge in 1 cubic centimeter of dry air under standard conditions. Named after Wilhelm Roentgen, German scientist who discovered X-rays in 1895.
roentgen equivalent See rem.
man (ur mammal)
39 - Glorsary of Tera 2 S
safeguards The protection of special nuclear material (SNM) to prevent theft, loss or sabotage.
(See special nuclear material.)
safe shutdown A design-basis earthquake.
(See design-basis earthquake phenomenon.)
safety injection The rapid insertion of a chemically soluble neutron poison (such as boric acid) into the reactor coolant system to ensure reactor shut-down.
(See shutdown.)
safety related The managerial controls, administrative documents, operating procedures, systems, structures and components that have been designed to mitigate the consequences of postulated accidents that could cause undue risk to public health and safety.
safety rod See control rod; scram.
i scattered radiation Radiation that, during its passage through a sub-stance, has been changed in direction.
It may also have been modified by a decrease in energy.
It is one form of secondary radiation, scintillation The combination of phosphor, photomultiplier tube, detector or and associated electronic circuits for counting counter light emissions produced in the phosphor by ionizieg radiation.
(See counter.)
l scram Sudden shutting down of a nuclear reactor, usually l
by rapid insertion of control
'ods, either auto-matically or manually by the reactor operator.
secondary radiation Radiation originating as the result of absorption of other radiation in matter.
It may be either electromaFnetic or particulate in nature.
secondary system The steam generator tubes, steam turbine, condenser h
and associated pipes, pumps and heaters used to convert the heat energy of the reactor coolant system into mechanical energy for electrical gener-ation. Most commonly used in reference to pres-surized water reactors.
seismic Category I A term used to define structures, systems and com-ponents that are designed and built to withstand the maximum potential (earthquake) stresses for the particular region that a nuclear plant is sited.
G1r-'ry ef Tarm - 40 m
E shielding Any material or obstruction that absorbs radiation and thus tends to protect personnel or materials from the effects of ionizing radiation.
shutdown A decrease in the rate of fission (and heat pro-duction) in a reactor (usually by the insertion of control rods into the core). See suberit-icality.)
somatic effects of Effects of radiation limited to the exposed indiv-radiation idual, as distinguished from genetic effects, wnich may also affect subsequent unexposed generations.
special nuclear Includes plutonium, uranium-233, or uranium material enriched in the isotopes uranium-233 or uranium-235.
spent (depleted) fuel Nuclear reactor fuel that has been used to the extent that it can no longer effectively sustain a chain reaction.
spent fuel pool An underwater storage and cooling facility for fuel elements that have been removed from a reactor.
stable isotope An isotope that does not undergo radioactive decay.
startup An increase in the rate of fission (and heat pro-duction) in a reactor usually by the removal of control rods from the core).
(See supercriti-cality.)
stay time The period during which personnel may remain in a restricted area before accumulating some permis-sible dose.
steam generator The heat exchanger used in some reactor designs to transfer heat from the primary (reactor coolant) system to the secondary (steam) system. This l
design permits heat exchange with little or no contamination of the secondary system equipment.
suberiticality The condition of a nuclear reactor system when the rate of production of fission neutrons is 1
I lower than the rate of production in the previous generation due to increased neutron leakage and poisons.
suberitical mass An amount of fissionable material insufficient in quantity or of improper geometry to sustain a fission chain reaction.
41 - Glonenry of Term 7 S
supercriticality The condition for increasing the level of oper-ation of a reactor. The rate of fission neutron production exceeds all neutron losses, and the overall neutron population increases.
(See critical mass; criticality.)
supercritical A reactor in which the power level is increasing.
reactor superheating The heating of a vapor, particularly steam, to a temperature much higher than the boiling point at the existing pressure. This is done in some power plants to improve efficiency and to reduce water damage to the turbine.
o survey A study to (1) find the radiation or contamin-ation level of specific objects or locations within an area of interest; (2) locate regions of higher-than-average intensity; i.e.,
hot spots.
(See personnel monitoring.)
survey meter Any portable radiation detection instrument especially adapted for inspecting an area to establish the existence and amount of radio-active material present.
(See counter.)
e
Gl+a-cry cf T2rms - 42
-T i
tailings, tails See mill tailinas.
tenth thickness The thickness of a given material that will decrease the amount (or dose) of radiation to one-tenth of the amount incident upon it.
Two-tenth thicknesses will reduce the dose received by a factor of 10 x 10; i.e.,100, and so on.
(See shielding.)
terrestrial
=The portion of natural radiation (background) that radiation is emitted by naturally occurring radioactive materials in the earth.
thermal breeder A breeder reactor in which the fission chain reactor reaction is sustained by thermal neutrons.
(See neutron, thermal.)
thermalization The process undergone by high-energy (fast) neutrons as they lose energy by collision.
(See neutron, thermal.)
thermal neutron See neutron, thermal.
thermal reactor A reactor in which the fission chain reaction is sustained primarily by thermal neutrons. Most current reactors are thermal reactors.
thermal shield A layer or layers of high-density material located within a reactor pressure vessel or between the vessel and the biological shield to reduce radia-tion heating in the vessel and the biological shield.
thermonuclear An adjective referring to the process in which very high temperatures are used to bring about the fusion of light nuclei, such as those of the hydrogen isotopes, deuterium and tritium, with the accompanying liberation of energy.
(See fusion.)
J transient A change in the reactor coolant system temperature i
and/or pressure due to a change in power output of the reactor. Transients can be caused by adding or removing neutron poisons, by increasing or de-creasing the electrical load on the turbine j
generator, or by accident conditions.
l trip, reactor See scram.
l I
43 - Glecesry of Terms T.
tritium A radioactive isotope of hydrogen (one proton, two neutrons). Because it is chemically iden-tical to natural hydrogen, tritium can easily be taken into the body by any ingestion path. Decays by beta emission.
Its radioactive halflife is about 12-1/2 years.
turbine A rotary engine made with a series of curved vanes on a rotating shaft. Usually turned by water or steam. Turbines are considered to be the most economical means to turn large electrical generators.
turbine generator A steam (or water) turbine directly connected to (TG) an electrical generator. The two devices are often referred to as one unit.
I 1
e,
l Glemnry of Tarms - 44 E
ultraviolet Electromagnetic radiation of a wavelength between the shortest visible violet and low-energy X-rays.
unrestricted area The area outside the owner-controlled portion of a nuclear facility (usually the site boundary).
unstable isotope A radioisotope.
uranium A radioactive element with the atomic number 92, (U) and as found in natural ores, an atomic weight of approximately 238. The two principal natural isotopes are uranium-235 (0.7 percent of natural uranium), which is fissile, and uranium-238 (99.3 percent of natural uranium), which is fissionable by fast neutrons and is fertile. Natural uranium also includes a minute amount of uranium-234.
uranium enrichment See isotopic enrichment.
uranium millings See mill tailings.
(tails)
Y vapor The gaseous form of substances that are normally in liquid or solid form.
vessel See pressure vessel.
vital plant systems See safety related.
void An area of lower density in a moderating system (such as steam bubbles in water) that allows more neutron leakage than does the more dense l
material around it.
(See moderator; void coeffi-cient; neutron leakage.)
void' coefficient of Property of a reactor plant moderating system k,
reactivity where, as temperature increases in the system, neutron leakage increases due to an increase in j'
the number and size of voids (steam bubbles) in the moderator.
1
,.w--
-e y
--m w
pm g
7 w
-y,---
45 - Gloacary of Terma 3
waste, radioactive Solid, liquid and gaseous materials from nuclear operations that are radioactive or become radio-active and for which there is no further use.
Wastes are generally classified as high level (having radioactivity concentrations of hundreds of thousands of curies per gallon or cubic foot),
low level (in the range of 1 microcurie per gallon or cubic foot), or intermediate level (between these extremes).
whole-body counter A device used to identify and measure the radiation in the body (body burden) of human beings and animals; it uses heavy shielding to keep out background radiation and ultrasensitive radiation detectors and electronic counting equipment.
whole-body exposure An exposure of the body to radiation, in which the entire body rather than an isolated part is irra-diated. Where a radioisotope is uniformly distri-buted throughout the body tissues, rather than being concentrated in certain parts, the irradia-tion can be considered as a whole-body exposure.
wipe sample A sample made for the purpose of determining the presence of removable radioactive contamination on a surface.
It is done by wiping, with slight pressure, a piece of soft filter paper over a representative type of surface area.
It is also known as a " swipe sample."
l E
Gle7enry of Tarm3 - 46 X
X-rays Penetrating electromagnetic radiation (photon) having a wavelength that is much shorter than that of visible light.
These rays are usually produced by excitation of the electron field around certain nuclei. In nuclear reactions, it is customary to refer to photons originating in the nucleus as gamma rays, and to those originating in the electron field of the atom as X-rays.
These rays are sometimes called roentgen rays after their discoverer, W. K. Roentgen.
I yellowcake A product of the uranium milling process, yellow-cake is a solid uranium-oxygen compound (U 0s) 3 that takes its name from its color and texture Yellowcake is the feed material used for fuel enrichment and fuel pellet fabrication.
I Y
47 - Glornary of Terms
' t:!
^^^
Turbine li!$!
C jjj I
Reactor Vessel jv' v'; ~-
o r
yvy.
3.x
/
3 y Fuel ~
fll iO! jll Generator Electrical
'E i
v a
Condenser
~)_
f) t (Recirc \\w/
b Feedwater 3
3 b,
Pump Pump SIMPLIFIED SCHEMATIC OF BOILING WATER REACTOR (BWR) PLANT l
i l
i
Gle"acry of Tarm7 - 48 I.- W
~..
I Il nnn
- -,y:
jl::.
- I!!!I;:::
///
Turbine r I
- Steam
///
Generator
/v'v'f
{
a f
O o
~
f.
- .f Electrical Generator Pressurizer '...
rg a
Condenser a
u
}.
('
'T Feedwater
-T
%g - ~ [N A - + '
G L
D Pump Fuel a
Reactor Vessel 4
y Reactot Coolant '.
W~ ll !
V Pump T
~
i SIMPLIFIED SCHEMATIC OF PRESSURlZED WATER REACTOR (PWR) PLANT e
49 - GlosNry of Terms, ELEM2NTS AND ELEMENT ABBREVIATIONS Name Symbol Name Symbol J
actinium Ac mercury Ng aluminum Al molybdenum Mo americum Am neodymium Nd antimony Sb neon Ne arsenic As neptunium Np astatine At nickel Ni barium Ba niobium Nb berkelium Bk nitrogen N
beryllium Be nobelium No bismuth Bi osmium Os 0
boron B
oxygen bromine Br palladium Pd cadmium Cd phosphorus P
calcium Ca platinum Pt californium Cf plutonium Pu carbon C
polonium Po cerium Ce potassium K
cesium Cs praseodymium Pr chlorine Cl promethium Pm l
chromium Cr protactinium Pa cobalt
.Co radium Ra Cu radon Rn copper curium Cm rhenium Re dysprosium Dy rhodium Rh I
einsteinium Es rubidium Rb erbium Er ruthenium Ru europium Eu samarium Sm l
j fermium Fm scandium Sc fluorine F
selenium Se francium Fr silicon Si gadolinium Gd silver Ag gallium Ga sodium Na i
j germanium Ge strontium Sr gold Au sulfur S
hafnium Hf tantalum Ta hclium He technetium Tc holmium Ho tellurium Te hydrogen H
terbium Tb indium In thallium Tl iodine I
Ir thulium Tm iron Fe tin Sn krypton Kr titanium Ti l.
W lanthanum La tungsten lawrencium Lr uranium U
l Pb vanadium V
lead Xe lithium Li xenou lutetium Lu ytterbium Yb Y
magnesium Mg yttriam Mn zine Zn manganese mendelevium Md zirconium Zr
Gle ncry of txrms - 50 PREFIXES d
deci
-(= 10 1)~
da deka
(= 10) c centi
(= 10 2) h kecto
(= 10 )
2 m
-milli
(= 10 3) k kilo
(= 10 )
8 p
micro'
-(= 10 s)
M mega-(= 10 ).
8 n
nanc
(= 10 8)
G giga
(= 10 )'
8 p
pico
(= 10 12)
T
. tera
(=.1012) f femto
(= 10 15) a atto-
'(= 10 18) 1 4
I-4 3-j '
i k
t I
m
.,r,
--,r-r--
-- =,
-rm.,y--
y,,-
9..%-,.,
yrm,,...,.
_y,
51 - Glecerry of Tarma NOTES
Gl' ~Ary cf T'rms - 52 NOTES
f,RC Fow 335 U.S. NUCLE AR REGULATOR ( COMMISSION BIBLIOGRAPHIC DATA SHEET NUREG-0770
- 4. Tl'LE AN D SUBTlTLE (Add Volume No., s/ appropriaseJ
- 2. fte,,, ef,n aj Glossary of Terms
- 3. RECIPIENT'S ACCESSION F".
Subtitle: Nuclear Power and Radiation
- 7. AUTHOR (S)
- 5. DATE REPORT COMPLETED Compilers:
J. G. Hanchett, OPA, F.W. Hasselberg, 0IE; LuvH lvEAR Editor:
M. H. Singh, ADM May 1981 9 PERFORMING ORGANIZATION N AME AND MAILING ADDRESS (/nclude 2,p Codel DATE REPORT ISSUED MONTH l YEAR Office of Public Affairs June 1981
' Office of Inspection and Enforcement
- s. a,ar, uanni Wi{shikko{[DAdmnisqratiin Of ice o ONONb
- 12. SPONSORING ORGANIZATION NAME AND MAILING ADDRESS (/nclude 2,p Oode/
Same as 9, above.
ii. CONTR ACT NO.
- 13. TYPE OF REPORT PE RIOD COVE RED (inclusive dares) 15 SUPPLEMENTARY NOTES
- 14. (Leave ormA) t
- 16. ABSTR ACT 000 words or less)
This " Glossary of Terms: Nuclear Power and Radiation" is a compilation of words and concepts commonly used in the nuclear power field defined to assist the news media and members of the public in understanding this often complex technology. The glossary was compiled by the NRC Office of Inspection and Enforcement and the Office of Public Affairs from a variety of internal and external sources.
It is a part of the agency's resp 2nse to a recommendation by the President's Commission of the Accident at Three Mile Island that government agencies, utility companies and the news media better prepare themselves to disseminate information to the public, in a form that is und:rstandable.
l
[
17 KEY WORDS AND DOCUMENT AN ALYSIS 17a DESCRIPTORS l
l l
17b. IDENTIFsE RS/OPEN-EN DE D TERMS 18 AV AILABILITY STATEMENT 19 SE CURITY CLASS (Th,s repo.-rl 21 NO OF PAGES nclass m ed Unlimited
- 20. SECURITY CLASS (This oave)
- 22. PRICE Unclassified S
I NRC F ORM 335 17 77)
. ~.
_,