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r
A symbol for reactivity.

R
A symbol for roentgen.

Ra
A symbol for radium.

rad
(1) A symbol for roentgen absorbed dose.
(2) A symbol for radiation absorbed dose.


radiation
Often a synonym for ionizing radiation. Generally this includes alpha particles, beta particles, gamma rays x-rays, neutrons, high-speed electrons, high-speed protons, and other particles capable of producing ions. Radiation, as used in 10CFR part 20, does not include non-ionizing radiation, such as radio- or microwaves, or visible, infrared, or ultraviolet light.

Related to ionizing radiation.
Related to nuclear radiation.


radiation absorbed dose
A synonym for roentgen absorbed dose.

radiation area
An area, accessible to individuals, in which radiation levels could result in an individual receiving a dose equivalent in excess of 0.005 rem (0.05 mSv) in 1 hour at 30 centimeters from the radiation source or from any surface that the radiation penetrates.

Reference: 10CFR20.
Related to high radiation area.
Related to very high radiation area.


radiation detection instrument
A device or material that is sensitive to radiation and which can produce a signal which can be recorded. Photographic film is a simple detector. Other forms include gas-filled counters (e.g., Geiger-Müller or proportional), crystal scintillators (e.g., sodium iodide), and semiconductor detectors (e.g., germanium or silicon).

Synonym: detector.

radiation dose
A synonym for dose.
Reference: 10CFR20.1003.


radiation injury
Injury that is a result of exposure to large doses of radiation.

Related to radiation sickness.

radiation monitoring
The measurement of radiation levels, concentrations, surface area concentrations or quantities of radioactive material and the use of the results of these measurements to evaluate potential exposures and doses.

Reference: 10CFR20.
Acronym: RM.
Synonym: monitoring.
Synonym: radiation protection monitoring.


radiation protection monitoring
A synonym for monitoring.

radiation safety officer
An individual with responsibility for the overall radiation safety program at the facility.

Acronym: RSO.
Reference: 10CFR36.


radiation shielding
Attenuation of radiation by placing a shield of absorbing material between the radiation source and a person, or a device sensitive to radiation.

Synonym: shielding.

radiation sickness
An illness resulting from excessive exposure to ionizing radiation. The earliest symptoms are nausea, vomiting, and diarrhea, which may be followed by loss of hair, hemorrhage, inflammation of the mouth and throat, and general loss of energy.

Synonym: radiation illness.
Synonym: radiation syndrome.
Related to radiation injury.


radiation source
A radioactive sample or a device (e.g., accelerator, x-ray generator) that emits radiation.

Acronym: RS.
Related to sealed radioctive source.


radiation syndrome
A synonym for radiation sickness.

radiation weight factor
A synonym for radiation weighting factor.
Reference: 10CFR20.1003; 10CFR30.4; 10CFR70.4; 10CFR76.4; USACHPPM TG 204.


radiation weighting factor
A normalization factor applied to the absorbed dose to produce the equivalent dose in a tissue or organ. The radiation weighting factor accounts for the effectiveness of radiation in inducing stochastic effects at low doses. Quality factor is an obsolete synonym for radiation weighting factor. Synonym: radiation weight factor.
Related to quality factor.
Related to tissue weighting factor.


radioactive
Having the capacity to undergo spontaneous disintegration by the emission of radiation. The term applies to an atom, a collection of atoms or an object.

radioactive constant
A synonym for decay constant.

radioactive contamination
Synonym: contamination.
Related to decontamination.


radioactive decay
Spontaneous emission by a nucleus of photons or particles.

The spontaneous transformation of one nuclide into another by emission of particles, absorption of an orbital electron, or by fission. It also refers to gamma-ray and conversion electron emission that only reduces the excitation energy of the nucleus.

Synonym: atom disintegration.
Synonym: atomic disintegration.
Synonym: decay.
Synonym: disintegration.
Synonym: nuclear disintegration.
Synonym: radioactive disintegration.


radioactive decay chain
A synonym for decay chain.

radioactive decay constant
A synonym for decay constant.

radioactive disintegration
A synonym for radioactive decay.

radioactive equilibrium
A condition where the rate of production of a nuclide by radioactive decay equals the rate of decay of that nuclide.

Related to equilibrium.
Related to secular equilibrium.
Related to transient equilibrium.


radioactive family
A synonym for decay chain.

radioactive half-life
A synonym for half-life.

radioactive material
(1) (49CFR173.403y) Material with a specific activity of greater than 0.002 mCi/g.

(2) (10CFR76) Source material, special nuclear material, or byproduct material, possessed, used, transferred, or disposed of.

Acronym: RAM.

radioactive isotope
A nuclide that is radioactive.

radioactive nuclide
An nuclide capable of undergoing radioactive decay.

Synonym: stable nuclide.
Synonym: (colloquial) unstable isotope.


radioactive series
A synonym for decay chain.

radioactive waste
(1) Radioactive sources, devices or materials made radioactive by contamination or irradiation, by-products from nuclear power and the nuclear fuel cycle that are to be discarded or placed in long-term storage.

(2) High-level radioactive waste and other radioactive materials other than high-level radioactive waste that are received for emplacement in a geologic repository.

(3) Solid, liquid, or gaseous material that contains radionuclides regulated under the Atomic Energy Act of 1954, as amended, and which is of negligible economic value considering costs of recovery. Radioactive waste includes sources, devices or materials made radioactive by contamination or irradiation, by-products from nuclear power and the nuclear fuel cycle.

Synonym: nuclear waste.
Synonym: rad waste.
Related to high-level waste.
Related to high-level radioactive waste.


radioactivity
Of or pertaining to radioactive nuclides, or objects or matter containing radioactive nuclides.

radiobioassay
A synonym for bioassay.

radiography
The examination of the structure of materials by nondestructive methods, utilizing sealed sources of byproduct materials. Radiations can be used to produce images of an object either by measuring their transmission through or their interaction with the object. Medical x-rays and x-ray baggage inspection are examples of transmission measurements. A neutron baggage inspection system images an object by measuring the spatial distribution of capture gamma rays produced by the reaction of neutrons with nitrogen in the object. Autoradiography describes the process of imaging an object using radiations produced by the radioactive decay of nuclides in the object. The radionuclides can be the result of radionuclide tagging, contamination by some source, or they can be produced by irradiating the object with neutrons or other radiations.

References: 10CFR30, 10CFR34.

radioisotope
A synonym for radionuclide.

radiological sabotage
Any deliberate act directed against a plant or transport in which an activity licensed pursuant to the regulations in this chapter is conducted, or against a component of such a plant or transport which could directly or indirectly endanger the public health and safety by exposure to radiation.

Reference: 10CFR73.

radiological survey
The directed effort to determine the distribution and dose rates of radiation in an area.

radiology
The study and use of radiation and radioactive substances for the treatment of disease.

radionuclide
A radioactive nuclide.

Synonym: radioisotope.

radioresistance
The ability of a cell, organ or organism to absorb radiation without significant damage.

Related to radiosensitivity.

radiosensitivity
The sensitivity of a cell, organ or organism to the exposure of radiation.

Related to radioresistance.

radiotoxicity
The hazard posed by a radiation or radioactive material to a cell, organ or organism.

radium
A chemical element with atomic number 88. Radium was discovered in 1898 by Marie Sklodowska Curie in an ore of pitchblende. In 1911 Curie and André Debierne successfully isolated radium by electrolysis. The name radium is derived from radius, Latin for ray.

Symbol: Ra.
Related to alkaline earth metals.


radium emanation
(obsolete term)

The nuclide 222Rn.
Symbol: RaEm.

radon
A chemical element with atomic number 86. Radon was discovered in 1900 by Friedrich Ernst Dorn. The name radon is derived from radius, Latin for ray.

Symbol: Rn.
Synonym: (obsolete) emanation.
Synonym: (obsolete) emanon.
Synonym: (obsolete) niton.


rad waste
A synonym for radioactive waste.

RaEm
A symbol for radium emanation.

RAM
A symbol for radioactive material.

rare earths
The lanthanides including sometimes scandium and yttrium.

Related to cerium.
Related to dysprosium.
Related to erbium.
Related to europium.
Related to gadolinium.
Related to holmium.
Related to lanthanides.
Related to lanthanum.
Related to lutetium.
Related to neodymium.
Related to periodic table.
Related to praseodymium.
Related to promethium.
Related to samarium.
Related to scandium.
Related to terbium.
Related to thulium.
Related to ytterbium.
Related to yttrium.


rare gases
A synonym for noble gases.

Rb
A symbol for rubidium.

RBE
An acronym for relative biological effectiveness.
Reference: DOE G 421.1-1.


RCS
An acronym for reactor coolant system.

Re
A symbol for rhenium.

reactivity
A measure of the departure of a reactor from criticality. It is defined as r = keff - 1, where keff is the effective multiplication factor. Reactivity is expressed in units of cent, dollar, and inhour.

Symbol: r.
Synonym: reactor reactivity.
Related to cent.
Related to control rod.
Related to dollar.
Related to effective multiplication factor.
Related to inhour.
Related to power coefficient.


reactivity worth
The effect that a parameter or component has on the reactivity of a reactor.

Synonym: worth.
Related to control rod.


reactor
A synonym for nuclear reactor.

reactor core
The region of a nuclear reactor containing the fissionable material.

Synonym: core.

reactor period
The time required for the neutron flux to increase by a factor of e.

Symbol: pile period.

reactor reactivity
A synonym for reactivity.

reactor trip
Acronym: RT.
A synonym for scram.


reactor vessel
A large steel container that houses the reactor core, control rods, moderator and coolant, and other control systems to maintain safe operation of the reactor.

Acronym: RV.
Synonym: containment vessel.
Synonym: pressure vessel.


reactor vessel head
The top section of a reactor pressure vessel. It is bolted in place during reactor operation and is removed to provide access to the core during maintenance and refueling.

recombination
A synonym for chemical recombination.

redundancy
Of or pertaining to the duplication of safety and control systems to ensure safe and reliable operation of a reactor or other device.

reference man
A hypothetical aggregation of human (male or female) physical and physiological characteristics arrived at by international consensus. These characteristics may be used by researchers and public health workers to standardize results of experiments and to relate biological insult from ionizing radiation to a common base.

reflector
A synonym for neutron reflector.

regulator rod
A control rod that has a small reactivity equivalent and is used to make fine adjustments to the reactor reactivity. It usually moves more quickly than a shim rod and has a reactivity worth of less than a dollar.

Related to control rod.
Related to safety rod.
Related to shim rod.


relative biological effectiveness
The ratio of an absorbed dose of a radiation to that of a standard which will give comparable damage in a biological material.

Acronym: RBE.
Synonym: biologic effectiveness of radiation.
Reference: NUREG-0544, Rev. 4.


rem
A symbolfor for roentgen equivalent man.
Reference: NUREG-0544, Rev. 4.


remedial action
Activities conducted at DOE facilities to reduce potential harm to and/or harm to the environment from radioactive and/or hazardous substance contamination.

repository
A facility for the permanent deep geologic disposal of High Level or Transuranic Waste.

research reactor
A nuclear reactor designed for radionuclide production, materials testing, and training.

resonance region neutron
A neutron with an energy between 1 eV and 0.01 MeV.

Related to cold neutron.
Related to continuum region neutron.
Related to epithermal neutron.
Related to fast neutron.
Related to low energy region neutron.
Related to slow neutron.
Related to thermal neutron.
Related to ultra cold neutron.
Related to very cold neutron.


restricted area
An area, access to which is limited by the licensee for the purpose of protecting individuals against undue risks from exposure to radiation and radioactive materials. Restricted area does not include areas used as residential quarters, but separate rooms in a residential building may be set aside as a restricted area.

Reference: 10CFR20, 10CFR60.
Related to unrestricted area.


Rf
A synonym for rutherfordium.

Rh
A symbol for rhodium.

rhenium
A chemical element with atomic number 75. Rhenium was discovered in 1925 by Otto Berg, Karl Friedrich Noddack, and Ida Tacke during experiments on platinum ore and the mineral columbite. The name rhenium is derived from the Latin word rhenus.

Symbol: Re.
Related to transition metals.


rhodium
A chemical element with atomic number 45. Rhodium was discovered in 1803 by William Hyde Wollaston during experiments on crude platinum ore. The name rhodium is derived from rhodon, Greek for rose colored.

Symbol: Rh.
Related to transition metals.


RM
An acronym for radiation monitoring.

Rn
A symbol for radon.

roentgen
A unit of radiation exposure defined as the amount of x- or gamma-radiation that produces 1 esu of charge per cm3 of dry air at 0 °C and 760 torr.

Symbol: R.
Related to milliroentgen.


roentgen absorbed dose
A unit of radiation dose defined as 100 erg/g or 0.01 J/kg. The SI unit of dose is the gray (Gy), where 1 Gy = 100 rad.

Symbol: rad.
Synonym: radiation absorbed dose.
Related to gray.


roentgen equivalent mammal
A synonym for roentgen equivalent man.
Reference: DOD 3150.8-M.


roentgen equivalent man
A unit of absorbed dose defined as the number of rads times a quality factor. It represents a dose equivalent or a dose that is correlated with injury due to radiation exposure. The sievert is the SI unit of absorbed dose; 1 rem is equivalent to 0.01 sievert.

Symbol: rem.
Synonym: roentgen equivalent mammal.
Related to quality factor.
Related to roentgen absorbed dose.
Related to sievert.
Reference: NUREG-0544, Rev. 4.


RS
An acronym for radiation source.

RSO
An acronym for radiation safety officer.

RT
An acronym for reactor trip.

Ru
A symbol for ruthenium.

rubidium
A chemical element with atomic number 37. Rubidium was discovered in 1860 by Robert Bunsen and Gustav Kirchoff in the mineral lepidolite. The name rubidium is derived from rubidus, Latin for deep red colored.

Symbol: Rb.
Related to alkali metals.


ruthenium
A chemical element with atomic number 44. Ruthenium was discovered in 1844 by Karl Klaus in a sample of crude platinum. The name ruthenium is derived from Ruthenia, Latin for Russia.

Symbol: Ru.
Related to transition metals.


rutherfordium
A chemical element with atomic number 104. Rutherfordium was discovered in 1964 by a team of scientists at the Joint Institute for Nuclear Research at Dubna in Russia who named the element kurchatovium. The Russian scientists were unable to duplicate their results and therefore lost credit to a team of scientists at the University of California, Berkeley, who identified the element. The scientists in California were successful in isolating the element after irradiating 249Cf with 12C. The name rutherfordium was given in honor of Ernest Rutherford.

Symbol: Rf.
Synonym: (obsolete) kurchatovium.
Synonym: (obsolete) unnilquadium.
Related to transition metals.


RV
An acronym for reactor vessel.
 
 
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