- radiation absorbed dose. The basic unit of absorbed dose of ionizing radiation.
One rad is equal to the absorption of 100 ergs of radiation energy per gram
- In the direction of a radius between the center and the surface of a circle,
cylinder, or sphere.
- Radian -
A unit in circular measure, an angle subtended at the center of a circle by
an arc of equal length to the radius. One radian is equal to 57.296.
- Energy traveling in the form of electromagnetic
Absorbed Dose (RAD) - the quantity that expresses
the amount of energy which ionizing radiation imparts to a given mass of matter.
Area - Any area, accessible to personnel, in which there exists radiation,
originating in whole or in part within licensed material, at such levels that
a major portion of the body could receive in any one hour a dose in excess
of 5 millirems, or in any 5 consecutive days, a dose in excess of 100 millirems.
Damage - A general term for the alteration of properties of a material
arising from radiation exposure to x-rays, gamma rays, neutrons, heavy-particle
radiation or fission fragments in nuclear fuel material.
Pressure - The pressure exerted on a surface by
Protection Guide - The total amounts of ionizing radiation dose over
certain periods of time which may safely be permitted to exposed industrial
groups. These standards, established by the Federal Radiation Council, are
equivalent to what was formerly called the "maximum permissible exposure."
Sources - An object that emitted radiation.
- Atoms which are energetically unstable and decay to a stable condition by
emitting radiation are said to be radioactive.
Activity - The amount of radiation an object is
Contamination - Deposition of any radioactive material in
any place where it is not desired, particularly where it may be harmful.
Decay - The
process by which the nucleus of a radioactive isotope decomposes and releases
Elements - Elements
that naturally emit radiation when the nucleus of the atoms disintegrate or
Half-Life (1/2T) - the time required for one half the atoms in a radioactive
substance to decay. For example, the radioactive half-life of cesium is 30.174
years. Radionuclides with short half-lives decay quickly and radionuclides
with longer half-lives emit energy over longer periods of time.
Material - Includes any such material whether or not subject to licensing
control by the commission.
- Equipment and materials (from nuclear operations) which are radioactive
and for which there is no further use.
- spontaneous decay
of the nucleus of an atom by the emission of particles, usually accompanied
by electromagnetic radiation. It is also defined as the mean number of nuclear
transformations occurring in a given quantity of radioactive material per
unit time, expressed in either becquerels (Bq) or curies (Ci). Most radionuclides
have multiple forms of radioactive emissions, and are classified according
to their principal decay modes. The most common types of radiation are
Alpha, Beta and
Concentration Guide - The concentration of radioactivity in an environment
which results in doses equal to those in the radiation protection guide. This
Federal Radiation Council term replaces the former "maximum permissible
photographic recording produced by the passage of radiation through a subject
onto a film.
- Any individual who performs or who, in attendance at the site where the
sealed source or sources are being used, personally supervises radiographic
operations and who is responsible to the licensee for assuring compliance
with the requirements of these regulations and the conditions of the licenses.
Code - A code for specifying minimum standards related to radiographic
Exposure Device - Any instrument containing therein, in which the
sealed source or shielding thereof may be moved, or otherwise change, from
a shielded to unshielded position for purposes of making a radiographic exposure.
Film - A type of film that is sensitive to a certain
type of radiation allow an image to form when exposed.
Interpretation - The determination of the cause and significance
of subsurface discontinuities indicated on the radiograph. The evaluation
as to the acceptability or rejectibility of the materials is based upon the
judicious application of the radiographic specifications and standards governing
Qualification Test - A procedure for determining the optimum value
of the d/t ratio, or the proper working distance of an x-ray tube or a radioactive
Screens - Metallic or fluorescent sheets used to intensify the radiation
effect on films.
process of making a radiograph
- Radio frequency
Display - The presentation of unrectified signals on a cathode ray
tube. See also video presentation.
elements that are atomically unstable and radioactive.
- That branch of medicine which uses ionizing radiation for diagnosis and
- A nuclide that is radioactive.
- A radioactive element with the atomic number 88 and an atomic weight of
226. In nature, radium is found associated with uranium, which decays to radium
by a series of alpha and beta emissions. Radium is used as a radiation source.
- Rads -
An absorbed does of 0.01 joules of energy per kilogram of tissue.
- The maximum ultrasonic path length that is displayed. See also sweep length.
Control - A means of expanding the pattern obtained on the cathode
ray tube so that any portion of the total distance being tested can be presented.
- The thinning or separation of particles in a propagating medium due
to the relaxation phase of an ultrasonic cycle. Opposite of compression. A
compressional wave is composed of alternating compressions and rarefactions.
- Ridges on a fatigue fracture that indicate where two adjacent fatigue areas
have grown together. Ratchet marks usually originate perpendicular to a surface
and may be straight or curved, depending on the combination of stresses that
- A beam of energy of small cross section.
Waves - An ultrasonic wave that propagates along the surface of a test
object. The particle motion is elliptical in a plane perpendicular to the
surface, decreasing rapidly with depth below the surface. The effective depth
of penetration is considered to be about one wavelength.
- Relative biological effectiveness. An RBE dose is the dose measured in rems.
Radiography - A radiograph is produced electronically
rather than on film so there is very little lag time.
- The section of the ultrasonic instrument that amplifies echoes returning
from the test object. Also, the transducer that picks up the echoes.
- (1) The change from one crystal structure to another, such as occurs on
heating or cooling through a critical temperature. (2)The formation of a new,
strain-free grain structure from that existing in cold-worked metal, usually
accomplished by heating.
Alternating Current - By means of device called a rectifier, which
permits current to flow in one direction only, alternating current can be
converted to direct or unidirectional current. This differs from direct current
in that the current value varies from a steady level. This variation may be
extreme, as inn the case of half-wave rectified single-phase AC or slight,
as in the case of three-phase rectified AC.
- A tube or circuit capable of converting the high voltage alternating wave
from into a usable unidirectional voltage wave form.
Factor - Dose rate without a shield divided by the dose rate with
a shield interposed between a source and a point at which radiation is measured.
- Eddy current transducer.
- A block or series of blocks of material containing artificial or natural
discontinuities or one or more reflecting areas at one or more distances from
the test surface, which are used for reference in defining the size and distance
of defective areas in materials.
Coil - Coil which enables bridge balancing in absolute probes. Its
impedance is close to test coil impedance but does not couple to test material.
Standards - A reference object containing known reflectors representing
accept or reject criteria.
- A sample test object.
- A group of radiographs containing images of discontinuities. These can be
used as comparison "standards" for acceptability of materials.
- A picture of recording of the indications presented on the cathode
ray tube of the ultrasonic instrument.
- A recording or chart made of either the signals transmitted through a part
or reflected back from defects within a part, or both
Beam - A beam that occurs in the second medium when an ultrasonic
beam is incident at an acute angel on the interface between two media having
different sound velocities.
- The change in direction of an acoustic wave as the ultrasonic beam
passes from one medium into another having a different sound velocity. A change
in both direction and mode occurs at acute angles of incidence. At small angles
of incidence, the original mode and a converted mode may exist in the second
Index -The ratio of the velocity of the incident wave to that of
a refracted wave. It is known as the refractive index of the second medium
with respect to the first.
- (1) In a butt joint, weld metal on the face of the weld that extends out
beyond a surface plane common to the members being welded; (2) in a fillet
weld, weld metal that contributes to convexity; (3) in a flash , upset or
gas pressure weld, the original diameter or thickness.
- An instrument function or control used for minimizing or eliminating low
amplitude signals (electrical or material noise) so that other signals may
be further amplified. Use of this control can reduce vertical linearity. Also
Level - The level above or below which a signal is an indication
of a rejectable discontinuity.
Biological Effectiveness (RBE)
- The relative effectiveness of a given kind of ionizing radiation in producing
a biological response as compared with 250,000 electron volt gamma rays.
- Relief of stress by creep. Some types of tests are designed to provide diminution
of stress by relaxation at constant strain, as frequently occurs in service.
- In nondestructive testing, an indication from a discontinuity requiring
- the degree of difficulty or resistance of a material to magnetize.
Magnetism - The term applied to the magnetism remaining in a magnetic
circuit after the magnetizing force is removed.
- REM - See Roentgen Equivalent Man.
- Roentgen equivalent physical. An obsolete unit of radiation dosage, now
superseded by the rad.
- Ability to repeatedly produce a measurement or detectable indication with separate measurements or inspections.
Rate - The number of pulses generated or transmitted per unit of
time (usually seconds).
- Elements present in an alloy in small quantities, but not added intentionally.
Field - The field left in a piece of ferromagnetic material when
the magnetizing force is reduced to zero.
Method (Magnetic Particle) - Bath is applied after current has been
shut off; that is, the indicating particles are on the part when residual
(remaining) magnetic field is present.
Stress – Internal stress; stress present in a body that is
free from external forces or thermal gradients.
(R) - The opposition to the flow of electrical current. Measured in ohms
- Reciprocal of conductivity.
that are used to control that amount of current flowing in a circuit by adding
a specific amount of resistance.
- The ability to clearly distinguish signals obtained from two reflective
surfaces with a minimum difference in depth. Near surface resolution is the
ability to clearly distinguish a signal from a reflector at a minimum distance
under the near surface without interference from the initial pulse signal.
Far surface resolution is the ability to clearly distinguish signals from
the back surface when the sound beam is normal to that back surface.
power - A measure of the ability of an ultrasonic system to separate
two signals close together in time or distance.
- A circuit having an inductor and capacitor connected in series or parallel.
When inductive reactance equals capacitive reactance the circuit is tuned
or in resonance.
- A method using the resonance principle for determining velocity, thickness
or presence or laminar discontinuities.
Circuits - A circuit containing capacitance and
Frequency - The frequency at which a body vibrates freely after being
set in motion by some outside force.
(vector field) -
When two or more magnetizing forces operating in different directions are
simultaneously applied to a ferromagnetic material, a resultant field is produced,
having a direction of the applied magnetizing forces. Such a field is also
referred to as a vector field. If either or both of the applied magnetizing
forces are themselves varying in direction or amount, the resultant field
is moving or swinging in direction and strength. Such a moving resultant field
is sometimes referred to as a "swinging field."
- The property of a given material of retaining, to a greater or lesser degree,
some amount of residual magnetism.
- RF Display
- See radio frequency display.
Method - A test method for bonded structures in which unbonds are
indicated by increased amplitude of ringing signals.
- Closely spaced multiple signals caused by multiple reflections in a thin
- Signals caused by continued vibration of a transducer.
- The time that the mechanical vibrations of a transducer continue after the
electrical pulse has stopped.
- The process of removing liquid penetrant inspection material from the surface
of an item by means of washing or flooding with another liquid, usually water.
Also termed "Wash."
- An ionization-type instrument designed to measure radiation dose.
- A unit of exposure dose of ionizing radiation. It is 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.
Equivalent Man (REM) - The biologically effective does in rems is the radiation does in rads multiplied
by a "quality factor" which is an assessment of the effectiveness
of that particular type and energy of radiation.
- A measure of radiation intensity of X-rays or
(of a Notch)
- The innermost part of a stress concentration, such as the bottom of a thread
Angle - In a dual element delay line transducer, the angle by which
the transducer elements of the delay line are tilted to direct the beams of
the two elements to intersect at a specified zone in the medium.
- A crack in either the weld or heat-affected zone at the root of a weld.
- The depth to which weld metal extends into the root of a joint.