ASTM C1673-07
(Terminology)Standard Terminology of C26.10 Nondestructive Assay Methods
Standard Terminology of C26.10 Nondestructive Assay Methods
SCOPE
1.1 The terminology defined in this document is associated with nondestructive assay of nuclear material.
1.2 All of the definitions are associated with measurement techniques that measure nuclear emissions (that is, neutrons, gamma-rays, or heat) directly or indirectly.
1.3 definitions are relevant to any standards and guides written by subcommittee C26.10.
General Information
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Standards Content (Sample)
Designation:C1673–07
Standard Terminology of
C26.10 Nondestructive Assay Methods
This standard is issued under the fixed designation C 1673; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
typically from intense low-energy X or gamma rays.
1. Scope
1.1 The terminology defined in this document is assoc iated
accidentals, n—the detection of multiple neutron events
with nondestructive assay of nuclear material.
within the gate width that are not produced from the same
1.2 All of the definitions are associated with measurement
fission.
techniques that measure nuclear emissions (that is, neutrons,
DISCUSSION—Accidental events take their name from the fact that it
gamma-rays, or heat) directly or indirectly.
is the accidental or random summing of neutrons, which are not time
1.3 definitions are relevant to any standards and guides
correlated with a common origin (fission or cosmic-ray burst), that give
written by subcommittee C26.10.
rise to the appearance of a signature like that from genuine correlated
events.
2. Referenced Documents
accuracy,n—(1) bias;(2) the closeness of a measured value to
2.1 ASTM Standards:
the true value; and (3) the closeness of a measured value to
E 456 Terminology Relating to Quality and Statistics
an accepted reference or standard value.
2.2 DOE Orders:
active assay,n—assay based on the observation of radiation(s)
DOE Order 435.1 Low-level Waste Requirements
induced by irradiation from an external source.
DOE Order 5820.2 Radioactive Waste Management
alpha, a, n—the ratio of the uncorrelated neutron emission
rate from (,n) reactions to the spontaneous neutron emission
3. Terminology
rate from a non-multiplying item.
(alpha) reaction, n—a reaction that occurs when energetic
aperture, n—the size of the opening in the collimator through
alpha particles collide with low atomic number nuclei
which the radiation of interest is intended to pass.
resulting in the emission of a neutron
assay, v—to determine quantitatively the amount of one or
240 240
Pu-effective mass, n—the mass of Pu that would produce
more nuclides of interest contained in an item.
the same coincident neutron response in the instrument as
attenuation correction, n—correction to the measured count
the assay item.
rate for attenuation of radiation that provides an estimate of
the unattenuated radiation emission rate of the radionuclides
DISCUSSION—It is a function of the quantity of even mass isotopes of
plutonium in the assay item and fundamental nuclear constants, being assayed.
sometimes referred to as effective Pu mass.
attenuation, n—reduction of radiation flux due to the interac-
tion of radiation with material between the source of the
absorber foils, n—foils, usually of copper, tin, cadmium, or
radiation and the detector.
lead, used to attenuate the gamma flux reaching a detector.
background,n—extraneoussignalsuperimposedonthesignal
DISCUSSION—Absorber foils are used to reduce the count rate,
of interest.
Beers Law, n—the fraction of uncollided gamma rays trans-
1 mitted through layers of equal thickness of an absorber is a
ThisterminologyisunderthejurisdictionofASTMCommitteeC26onNuclear
constant.
Fuel Cycle and is the direct responsibility of Subcommittee C26.10 on Non
Destructive Assay.
benign matrix, n—material that has a negligible effect on the
Current edition approved June 1, 2007. Published July 2007.
result of the measured parameter.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
blank, n—a prepared item containing a matrix as similar as
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on practical to the items being measured that is free, to the
the ASTM website.
extent possible, of the radionuclides of interest.
Available from the U.S. Department of Energy (DOE), 1000 Independence
Ave., SW Washington, DC 20585.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
C1673–07
DISCUSSION—The most important matrix parameters are those that
data quality objective, n—measurement uncertainty and con-
affect the result of the measurement technique being used.
fidence levels specified by the scope of work.
dead time, n—the period following the detection of an event
calibration standard, n—an item similar to the items to be
during which the detection electronics cannot register a
assayed, for which the parameters of interest and all prop-
subsequent event.
erties to which the measurement technique is sensitive are
known.
DISCUSSION—Dead time is usually expressed as a percentage of
calorimeter, n—a device to measure heat or rate-of-heat
elapsed time.
generation.
delayed neutrons, n—neutrons emitted by the item that are
calorimetric assay, n—determination of the mass of radioac-
produced from decay of the fission products.
tive material through the measurement of its thermal power
by calorimetry and the use of nuclear decay constants and, if DISCUSSION—These neutrons are produced at a time after the initial
fission event.
necessary, additional isotopic measurements.
certification, n—a written declaration from a certifying body
depleted uranium, n—uranium containing less than the natu-
or its legitimate designee that a particular measurement
rally occurring fraction of U isotopes (< 0.7 weight
process or measurement personnel comply with stated crite-
percent).
ria or that a measured item has the stated characteristics.
die-away time, n—the average life time of the neutron
code validation, n—process to determine that the software
population as measured from the time of emission to
performs its intended functions correctly, ensure that it
detection, escape, or absorption. The average lifetime is the
performs no unintended functions, and provides information
time required for the neutron population to decrease by a
about its quality and reliability.
factor of 1/e.
coincidence gate length, n—the time interval following the
doubles, n—the detection of neutron pairs produced from the
detection of a neutron during which additional neutrons are
same fission event.
considered to be in coincidence with the original neutron.
DISCUSSION—The doubles terminology is often used in reference to
coincident neutrons, n—two or more neutrons emitted simul-
multiplicity counting, but it is the same as the reals from coincidence
taneously from a single event, such as from a nucleus during
counting.
fission.
effective specific power, p , n—the rate of energy emission
collimated detector, n—a detector surrounded by a shield that
eff
imposes a directional response on the collimated detector. per unit mass of radionuclide at the time of measurement.
far-field measurement, n—a measurement geometry where
collimator, n—a shield that imposes a directional response on
the detector. Generally, for gamma ray detection the colli- the analyst can assume that all gamma rays emitted from the
item enter the detector along paths parallel to each other.
mator is a hollow cylinder or rectangular prism of high
atomic number (Z) and high density material, mounted field of view, n—the entire solid angle subtended by the
collimated detector.
coaxially to the detector and extending over the detector and
fissile isotopes, n—isotopes that can be induced to fission by
beyond the detector face.
Comptonscattering,n—scatteringofgammaraysthatmayor thermal neutrons.
may not be from the radionuclide of interest.
233 235 239 241
DISCUSSION— U, U, Pu, and Pu are the most common fissile
isotopes.
DISCUSSION—Thescatteringreducestheenergyofthegammarayand
results in a continuum of gamma ray energies.
flux monitors, n—detectors in the measurement chamber that
computed tomography, n—see tomography. measure the neutron flux of interrogating neutrons (cavity
flux monitor) or item neutrons (drum flux monitor).
confidence interval, n—The range of values, calculated from
the probability distribution (often sufficiently well character- heat-flow calorimeter, n—a calorimeter so constructed that
the heat generated in the calorimeter flows past a tempera-
ized by the estimate of the mean and standard deviation),
which is expected to include the population mean with a ture sensing element, through a thermal resistance, to a
constant temperature heat sink.
stated level of confidence or likelihood.
holdup, n—the residual nuclear material remaining in process
DISCUSSION—For more details see Test Method E 456.
equipment and facilities.
contact measurement, n—a special case of a near-field
homogeneous matrix, n—a matrix whose characteristics im-
measurement in which measurements are made with the portant to the measurement result is uniform throughout the
detector assembly in contact with the item, for example,
item.
tank, pipe, ductwork, being assayed. infinite thickness, n—the thickness of material through which
control chart, n—a graphical plot of test results with respect
99.9 % of the gamma rays of the designated energy cannot
to time or sequence of measurement together with limits in penetrate.
which they are expected
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