The glossary story... Home    Author    Research    Methodology    Contact
  Glossary terms... A    B    C    D    E    F    G    H    I    J    K    L    M    N    O    P    Q    R    S    T    U    V    W    XYZ    numbers
  Collections... dose    elements    neutrons    nuclides    radiation    radioactive decay    reactions    reactors radiation safety   
units    U.S.Regs   
  Further Reading... general    nuclear science    nuclear engineering    health physics   
d
A symbol for deci.
A symbol for deuteron.


D
(1) A symbol for deuterium.
(2) A symbol for absorbed dose.


D2O
A symbol for heavy water.

DAC
An acronym for derived air concentration.

daughter
A synonym for daughter nuclide.

daughter element
A synonym for daughter nuclide.

daughter nuclide
The nuclide produced in radioactive decay.

Synonym: daughter.
Synonym: daughter element.
Synonym: decay product.
Synonym: descendent.
Related to decay chain.
Related to parent nuclide.


daughter product
A synonym for daughter nuclide.

DBA
Acronym for design-basis accident.

DBE
1. An acronym for design-basis earthquake.
2. An acronym for design-basis event.


DBT
An acronym for design-basis tornado.

DE
An acronym for dose equivalent.

decay
A synonym for radioactive decay.

decay chain
A series of nuclides linked in a chain by radioactive decay. Each nuclide in the chain decays to the next until a stable nuclide is reached.

Synonym: decay family.
Synonym: decay series.
Synonym: disintegration chain.
Synonym: disintegration family.
Synonym: disintegration series.
Synonym: family.
Synonym: radioactive decay chain.
Synonym: radioactive family.
Synonym: radioactive series.
Related to daughter nuclide.
Related to parentage.
Related to parent nuclide.


decay coefficient
A synonym for decay constant.

decay constant
The proportionality constant of decay for a nuclide. It is related to the half-life by the expression λ = ln 2 / T1/2 , where λ is the decay constant and T1/2 is the half-life of the nuclide. A sample initially containing N0 atoms of a particular radionuclide that has a decay constant of λ will have an initial activity equivalent to A0 = dN/dt = - λN0. Over time the activity will decrease as given by the expression A = A0 e-λt.

Synonym: decay coefficient.
Synonym: disintegration constant.
Synonym: radioactive constant.
Synonym: radioactive decay constant.


decay daughter
A synonym for daughter nuclide.

decay electron
A synonym for beta particle.

decay energy
A synonym for decay Q-value.

decay family
A synonym for decay chain.

decay heat
Heat produced through radioactive decay. It is especially important for fission products.

Acronym: DH.
Related to after heat.


decay mode
A particular type of radioactive decay. Examples include β- decay, β+ decay, a decay, internal transition, and spontaneous fission.

decay product
A synonym for daughter nuclide.

decay Q-value
The total energy that can be emitted in radioactive decay.

Synonym: decay energy.
Synonym: disintegration energy.
Synonym: nuclear disintegration energy.
Related to Q-value.


decay rate
A synonym for activity.

decay scheme
A level scheme populated in radioactive decay.

Related to level scheme.

decay series
A synonym for decay chain.

deci
A unit prefix equivalent to 10-1.

Symbol: d.

declared pregnant woman
A woman who has voluntarily informed her employer, in writing, of her pregnancy and the estimated date of conception.

Reference: 10CFR20.

decommission
The process of dismantling a reactor or accelerator. It involves removing fuel, contaminated water, and decontaminating removable devices, preparing the remaining structure for long-term, safe storage or isolation.

DECON
Acronym for decontamination and dismantlement.

decontamination
The process of removing unwanted contaminants from the surface of an object or from an area. Decontamination is designed to reduce the risks of exposure. Contaminants can be radioactive, chemical, or biological. This term applies to removal by washing, biological agents, chemical action, mechanical cleaning, or other techniques.

Related to immediate decontamination.
Related to operational decontamination.
Related to radioactive contamination.
Related to thorough decontamination.


decontamination factor
For a decontamination or other separation process it is a ratio of the initial activity to the final activity.

Acronym: DF.
Related to decontamination index.


decontamination index
The logarithm of the decontamination factor.

Related to decontamination factor.

deep dose
A synonym for deep-dose equivalent.

deep-dose equivalent
The dose equivalent to tissue at a depth of one centimeter due to external radiation.

Symbol: Hd.
Synonym: deep dose.
Related to total organ dose equivalent.


defense in depth
An approach to facility safety that builds-in layers of defense against release of hazardous materials so that no one layer by itself, no matter how good, is completely relied upon. To compensate for potential human and mechanical failures, defense in depth is based on several layers of protection with successive barriers to prevent the release of hazardous material to the environment. This approach includes protection of the barriers to avert damage to the plant and to the barriers themselves. It includes further measures to protect the public, workers, and the environment from harm in case these barriers are not fully effective.

Acronym: DID.

delayed fission neutron
A neutron emitted by a fission product.

Related to beta-delayed neutron.
Related to fission neutron.
Related to prompt fission neutron.


delayed health effects
Effects of radiation that appear long after the original exposure.

Related to nonstochastic effects.
Related to stochastic effects.


delayed neutron
Acronym: DN.
See instead beta-delayed neutron.


depleted fuel
A synonym for spent nuclear fuel.

depleted uranium
Uranium in which 235U has an isotopic abundance of less than is found in nature. It is less than approximately 0.711%.

Related to enriched uranium.
Related to natural uranium.


derived air concentration
The concentration of a given radionuclide in air which, if breathed by the reference man for a working year of 2,000 hours under conditions of light work, results in an intake of 1 ALI. Derived air concentration values are given in Table 1, Column 3, of appendix B to 10CFR part 20.1001-20.2401.

Reference: 10CFR20.
Acronym: DAC.
Related to annual limit on intake.
Related to light work.
Related to reference man.


descendent
A synonym for daughter nuclide.

design-basis accident
A standard to which a nuclear facility is designed. It is a postulated accident that the facility must withstand without loss to the components, systems, and structures.

Acronym: DBA.
Related to category 1 design-basis event.
Related to category 2 design-basis event.
Related to design-basis criticality.
Related to design-basis earthquake.
Related to design-basis event.
Related to design-basis explosion.
Related to design-basis fire.
Related to design-basis flood.
Related to design-basis tornado.


design-basis criticality
A criticality accident that is the most severe design basis accident of that type applicable to the area under consideration.

Related to category 1 design-basis event.
Related to category 2 design-basis event.
Related to design-basis accident.
Related to design-basis earthquake.
Related to design-basis event.
Related to design-basis explosion.
Related to design-basis fire.
Related to design-basis flood.
Related to design-basis tornado.


design-basis earthquake
That earthquake for which the safety systems are designed to remain functional both during and after the event, thus assuring the ability to shut down and maintain a safe configuration.

Acronym: DBE.
Synonym: safe-shutdown earthquake
Related to category 1 design-basis event.
Related to category 2 design-basis event.
Related to design-basis accident.
Related to design-basis criticality.
Related to design-basis event.
Related to design-basis explosion.
Related to design-basis fire.
Related to design-basis flood.
Related to design-basis tornado.


design-basis event
A postulated event used in the design to establish the acceptable performance requirements of the structures, systems, and components.

Acronym: DBE.
Synonym: design-basis phenomenon.
Related to category 1 design-basis event.
Related to category 2 design-basis event.
Related to design-basis accident.
Related to design-basis criticality.
Related to design-basis earthquake.
Related to design-basis explosion.
Related to design-basis fire.
Related to design-basis flood.
Related to design-basis tornado.


design-basis explosion
An explosion that is the most severe design basis accident of that type applicable to the area under consideration.

Related to design-basis accident.
Related to design-basis criticality.
Related to design-basis earthquake.
Related to design-basis event.
Related to design-basis fire.
Related to design-basis flood.
Related to design-basis tornado.


design-basis fire
A fire that is the most severe design basis accident of this type. In postulating such a fire, failure of automatic and manual fire suppression provisions shall be assumed except for those safety class items or systems that are specifically designed to remain available (structurally or functionally) through the event.

Related to design-basis accident.
Related to design-basis criticality.
Related to design-basis earthquake.
Related to design-basis event.
Related to design-basis explosion.
Related to design-basis flood.
Related to design-basis tornado.


design-basis flood
A flood that is the most severe design basis accident of that type applicable to the area under consideration.

Related to design-basis accident.
Related to design-basis criticality.
Related to design-basis earthquake.
Related to design-basis event.
Related to design-basis explosion.
Related to design-basis fire.
Related to design-basis tornado.


design-basis phenomenon
A synonym for design-basis event.

design-basis tornado
A tornado that is the most severe design basis accident of that type applicable to the area under consideration.

Acronym: DBT.
Related to design-basis accident.
Related to design-basis criticality.
Related to design-basis earthquake.
Related to design-basis event.
Related to design-basis explosion.
Related to design-basis fire.
Related to design-basis flood.


detection gas
A gas sensitive to radiation and that produces an electric, electromagnetic or other signal which can be more easily detected.

detector
A synonym for radiation detection instrument.

deterministic effects
A synonym for nonstochastic effects.

deuterium
An isotope of hydrogen which has a single proton and a single neutron. Deuterium is a stable, naturally occurring nuclide found with an isotopic abundance of 1 part in every 7,000 parts of 1H. A deuterium nucleus is often referred to as a deuteron. The name was proposed by Bohr and Heisenberg.

Symbol: 2H.
Symbol: D.
Synonym: diplogen.
Synonym: heavy hydrogen.
Related to deuteron.
Related to hydrogen.
Related to tritium.


deuterium oxide
A water molecule which is composed of an atom of oxygen to which two atoms of the nuclide deuterium (2H) are attached.

Symbol: D2O.
Synonym for heavy water.


deuteron
The nucleus of the 2H atom. A deuterium nucleus. The deuteron has a mass of 3.3435860(20)x10-27 kg or 2.013553214(24) amu.

Symbol: d.
Synonym: (obsolete)diplon.
Related to deuterium.


DH
An acronym for decay heat.

DID
An acronym for defense in depth.

diplogen
(obsolete term)

A name Rutherford proposed in 1932 for the nuclide 2H, deuterium.

A synonym for deuterium.

diplon
(obsolete term)

A synonym for the deuteron used primarily in Europe.

directional dose equivalent
A synonym for equivalent dose.

disintegration
A synonym for radioactive decay.

disintegration chain
A synonym for decay chain.

disintegration constant
A synonym for decay constant.

disintegration electron
A synonym for beta particle.

disintegration energy
A synonym for decay Q-value.

disintegration family
A synonym for decay chain.

disintegration rate
A synonym for activity.

disintegration series
A synonym for decay chain.

disintegrations per minute
The number of decays that occur per minute for a population of a nuclide or a sample containing radioactive material.

disintegrations per second
The number of decays that occur per second for a population of a nuclide or a sample containing radioactive material.

disposal facility
The land, structures, and equipment used for the disposal of waste.

Reference: DOE Order 5820.2A.

DN
An acronym for delayed neutron.

DNB
An acronym for departure from nucleate boiling.

DNBR
An acronym for departure from nucleate boiling ratio.

dollar
A unit of reactor reactivity defined as $1.00 = keff/b, where keff is the effective multiplication factor and b is the total fraction of delayed neutrons.

Symbol: $.
Related to cent.
Related to effective multiplication factor.
Related to inhour.
Related to reactivity.


dosage
A synonym for dose.

dosage rate
A synonym for dose rate.

dose
The amount of energy of a radiation absorbed in matter. The SI standard unit of dose is the gray.

Synonym: dosage.
Synonym: radiation dose.
Related to absorbed dose.
Related to collective dose.
Related to committed dose equivalent.
Related to committed effective dose equivalent.
Related to dose equivalent.
Related to effective dose equivalent.
Related to gray.
Related to integral absorbed dose.
Related to total effective dose equivalent.


dose commitment
The dose equivalent received by a person to a specified organ during one calendar year due to uptake of a radionuclide.

Synonym: committed dose.

dose equivalent
A synonym for equivalent dose.

dose limits
The permissible upper bounds of radiation doses.

Reference: 10CFR20.1003.

dose meter
A synonym for dosimeter.

dose rate
The radiation dose per unit time.

Synonym: dosage rate.

dosimeter
A device that measures radiation dose.

Synonym: dose meter.

dosimetry
Of or pertaining to the process of measuring radiation dose.

double beta decay
Radioactive decay that occurs with the emission of two β- particles. It is a rare type of decay.

Synonym: ββ decay
Synonym: β-β- decay
Synonym: double-beta disintegration


DP
An acronym for differential pressure.

dpm
A symbol for the measurement unit decays per minute.

dps
A symbol for the measurement unit decays per second.

D/P
An acronym for differential pressure.

dual beta decay
For a nuclide it is a term that refers to the existence of beta minus and positron emission decay modes.

Related to beta decay.
Related to β- decay.
Related to positron decay.


dubnium
A chemical element with atomic number 105.

Symbol: Db.
Synonym: (obsolete) hahnium.
Synonym: (obsolete) unnilpentium.
Related to transition metals.


DW
An acronym for drywell.

DWL
An acronym for drywell.

Dy
A symbol for dysprosium.

dysprosium
A chemical element with atomic number 66. Dysprosium was discovered in 1866 by Paul-émile Lecoq de Boisbaudran. In 1950, Spedding and associates were able to isolate the element through the separation techniques of ion-exchange and metallographic reduction. The name dysprosium is derived from dysprositos, Greek for hard to get.

Symbol: Dy.
Related to lanthanides.
Related to rare earths.
Related to terbium earths.
 
 
Copyright © 2003-2006 Scientific Digital Visions, Inc. All rights reserved.

Our partner sites:
Argus Clearinghouse 
uk slot machines