ASTM C1514-08(2017)

Standard Test Method for Measurement of ²³⁵U Fraction Using Enrichment Meter Principle

SIGNIFICANCE AND USE
5.1 The enrichment meter principle provides a nondestructive measurement of the  235U fraction of uranium-bearing items. Sampling is not required and no waste is generated, minimizing exposure to hazardous materials and resulting in reduced sampling error.  
5.2 This method relies on a fixed and controlled geometry. The uranium-bearing materials in the measured items and calibration reference materials used for calibration must fill the detector field of view.  
5.3 Use of a low resolution detector (for example, NaI detector) to measure uranium with  235U fraction approximately 10 % which is contained in a thin-walled container can provide a rapid (typically 100 s), easily portable measurement system with precision of 0.6 % and bias of less than 1 %.  
5.4 Use of a high resolution detector (for example, high-purity germanium) can provide measurement with a precision better than 0.2 % and a bias less than 1 % within a 300-s measurement time when measuring uranium with  235U fraction in the range of 0.711 % or above which is contained in thin-walled containers.  
5.5 In order to obtain optimum results using this method, the chemical composition of the item must be well known, the container wall must permit transmission of the 185.7 keV gamma-ray, and the uranium-bearing material within the item must be infinitely thick with respect to the 185.7 keV gamma-ray. All items must be in identical containers or must have a known container wall thickness and composition.  
5.6 Items to be measured must be homogeneous with respect to both  235U fraction and chemical composition.  
5.7 When measuring items, using low-resolution detectors, in thin-walled containers that have not reached secular equilibrium (more than about 120 days after processing), either the method should not be used, additional corrections should be made to account for the age of the uranium, or high-resolution measurements should be performed.  
5.8 The method is often used as a enrichment verificatio...
SCOPE
1.1 This test method covers the quantitative determination of the fraction of  235U in uranium using measurement of the 185.7 keV gamma-ray produced during the decay of  235U.  
1.2 This test method is applicable to items containing homogeneous uranium-bearing materials of known chemical composition in which the compound is considered infinitely thick with respect to 185.7 keV gamma-rays.  
1.3 This test method can be used for the entire range of  235U fraction as a weight percent, from depleted (0.2 % 235U) to highly enriched (97.5 % 235U).  
1.4 Measurement of items that have not reached secular equilibrium between  238U and  234Th may not produce the stated bias when low-resolution detectors are used with the computational method listed in Annex A2.  
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.6 This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Published
• Publication Date: 31-Dec-2016
• ICS: 27.120.30 - Fissile materials and nuclear fuel technology
• Technical Committee: C26 - Nuclear Fuel Cycle
• Drafting Committee: C26.10 - Non Destructive Assay

Relations

• Replaces: ASTM C1514-08 - Standard Test Method for Measurement of ²³⁵U Fraction Using Enrichment Meter Principle
• Effective Date: 01-Jan-2017
• Refers: ASTM C1030-10(2018) - Standard Test Method for Determination of Plutonium Isotopic Composition by Gamma-Ray Spectrometry
• Effective Date: 01-Apr-2018
• Refers: ASTM C1490-04(2010) - Standard Guide for the Selection, Training and Qualification of Nondestructive Assay (NDA) Personnel
• Effective Date: 01-Oct-2010
• Refers: ASTM C1490-04 - Standard Guide for the Selection, Training and Qualification of Nondestructive Assay (NDA) Personnel
• Effective Date: 01-Feb-2004
• Refers: ASTM C1592-04 - Standard Guide for Nondestructive Assay Measurements
• Effective Date: 01-Feb-2004
• Refers: ASTM C1030-03 - Standard Test Method for Determination of Plutonium Isotopic Composition by Gamma-Ray Spectrometry
• Effective Date: 10-Jul-2003
• Refers: ASTM C1490-01 - Standard Guide for the Selection, Training and Qualification of Nondestructive Assay (NDA) Personnel
• Effective Date: 10-Jan-2001
• Refers: ASTM C1030-95(2001) - Standard Test Method for Determination of Plutonium Isotopic Composition by Gamma-Ray Spectrometry
• Effective Date: 10-Sep-1995
• Referred By: ASTM C1490-14(2023) - Standard Guide for the Selection, Training and Qualification of Nondestructive Assay (NDA) Personnel
• Effective Date: 01-Jan-2017
• Referred By: ASTM C1592/C1592M-21 - Standard Guide for Making Quality Nondestructive Assay Measurements
• Effective Date: 01-Jan-2017

Overview

ASTM C1514-08(2017) is the internationally recognized standard test method for quantitative determination of the fraction of uranium-235 (^235U) in uranium-bearing items using the Enrichment Meter principle. Developed by ASTM International, this standard provides a nondestructive assay (NDA) technique that utilizes gamma-ray spectrometry-specifically the 185.7 keV gamma-ray emitted during ^235U decay-to determine enrichment. This method offers significant advantages, including eliminating the need for sample removal, reducing hazardous exposure and minimizing sample-related error. It supports a wide range of uranium enrichment levels, from depleted to highly enriched uranium.

Key Topics

• Nondestructive Measurement: The enrichment meter enables assessment of ^235U content without physical sampling or generating radioactive waste, supporting safe and efficient testing practices.
• Detector Types: The method supports both low-resolution detectors (e.g., NaI) for rapid, portable measurements and high-resolution detectors (e.g., HPGe) for higher precision and minimal bias.
• Calibration: Calibration with reference materials spanning the expected enrichment range is essential for accurate readings. Consistency in container geometry, wall thickness, and chemical composition is required.
• Homogeneity Requirement: The uranium-bearing material must be homogeneous in both ^235U fraction and chemical makeup to ensure valid results.
• Applicability Range: Suited for items deemed infinitely thick to the 185.7 keV gamma-ray, this approach covers the full enrichment spectrum-from about 0.2% to 97.5% ^235U by weight.
• Correction Factors: Proper adjustment for container wall attenuation and differences in chemical form between calibration and measured items is critical for reliable outcome.
• Measurement Limitations: Items not in secular equilibrium after processing or those with uncharacterized impurities may yield biased results, especially when using low-resolution detectors.

Applications

This standard is widely employed within the nuclear fuel cycle, including:

• Uranium Enrichment Verification: Commonly used for verifying the enrichment level during production, processing, transport, and storage of uranium materials.
• Safeguards and Regulatory Compliance: Supports international nuclear safeguards by ensuring materials are appropriately characterized and accounted for, aiding adherence to regulatory frameworks such as those set by IAEA or national authorities.
• Facility Operations: Enables rapid, in situ enrichment determinations for process control and material accountability in enrichment plants, fuel fabrication sites, and research institutions.
• Containerized Assessments: Suitable for analyzing uranium stored in thin-walled or standard cylindrical containers, provided that container composition and wall thickness are known or controlled.
• Field Measurements: The portable, nondestructive nature of this method allows its use in remote field operations, minimizing handling risks and logistical complexity.

Related Standards

The effectiveness and implementation of ASTM C1514-08(2017) can be enhanced in conjunction with several related documents:

• ASTM C1030 - Determination of Plutonium Isotopic Composition by Gamma-Ray Spectrometry
• ASTM C1490 - Guide for Selection, Training, and Qualification of NDA Personnel
• ASTM C1592 - Guide for Nondestructive Assay Measurements
• ANSI N42.14 - Calibration and Use of Germanium Spectrometers for Measurement of Gamma-Ray Emission Rates of Radionuclides
• C26.10 Terminology Guide - Nuclear Fuel Cycle Terminology

Practical Value

By establishing a reliable, nondestructive, and portable method for measuring uranium enrichment, ASTM C1514-08(2017) plays a vital role in the safe handling, regulatory oversight, and quality assurance of uranium-bearing materials. The standard’s flexibility in detector choice, broad applicability across enrichment levels, and robust calibration requirements make it an essential resource for nuclear industry professionals and regulators seeking to enhance facility safety, measurement accuracy, and compliance efficiency.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: C1514 − 08 (Reapproved 2017)
Standard Test Method for
Measurement of U Fraction Using Enrichment Meter
Principle
This standard is issued under the fixed designation C1514; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope C1592 Guide for Nondestructive Assay Measurements
C26.10 Terminology Guide
1.1 This test method covers the quantitative determination
2.2 ANSI Standard:
of the fraction of U in uranium using measurement of the
N42.14 Calibration and Use of Germanium Spectrometers
185.7 keV gamma-ray produced during the decay of U.
for the Measurement of Gamma-Ray Emission Rates of
1.2 This test method is applicable to items containing
Radionuclides
homogeneous uranium-bearing materials of known chemical
composition in which the compound is considered infinitely
3. Terminology
thick with respect to 185.7 keV gamma-rays.
3.1 For definitions of terms used in this test method, refer to
1.3 Thistestmethodcanbeusedfortheentirerangeof U
Terminology C26.10.
fraction as a weight percent, from depleted (0.2 % U) to
highly enriched (97.5 % U).
4. Summary of Test Method
1.4 Measurement of items that have not reached secular
4.1 The test method consists of measuring the emission rate
238 234
equilibrium between U and Th may not produce the
of 185.7 keV gamma-rays from an item in a controlled
stated bias when low-resolution detectors are used with the
geometry and correlating that emission rate with the enrich-
computational method listed in Annex A2.
ment of the uranium contained in the item.
1.5 The values stated in SI units are to be regarded as
4.2 Calibration is achieved using reference materials of
standard. No other units of measurement are included in this
known enrichment. Corrections are made for attenuating ma-
standard.
terials present between the uranium-bearing material and the
1.6 This standard may involve hazardous materials,
detector and for chemical compounds different from the
operations, and equipment. This standard does not purport to
calibration reference materials used for calibration.
address all of the safety concerns, if any, associated with its
4.3 The measured items must completely fill the field of
use. It is the responsibility of the user of this standard to
view of the detector, and must contain a uranium-bearing
establish appropriate safety and health practices and deter-
material which is infinitely thick with respect to the 185.7 keV
mine the applicability of regulatory limitations prior to use.
gamma-ray. If the field of view is not filled, a correction factor
must be applied.
2. Referenced Documents
2.1 ASTM Standards:
5. Significance and Use
C1030 TestMethodforDeterminationofPlutoniumIsotopic
5.1 The enrichment meter principle provides a nondestruc-
Composition by Gamma-Ray Spectrometry
tive measurement of the U fraction of uranium-bearing
C1490 GuidefortheSelection,TrainingandQualificationof
items. Sampling is not required and no waste is generated,
Nondestructive Assay (NDA) Personnel
minimizing exposure to hazardous materials and resulting in
reduced sampling error.
This test method is under the jurisdiction ofASTM Committee C26 on Nuclear
5.2 This method relies on a fixed and controlled geometry.
Fuel Cycle and is the direct responsibility of Subcommittee C26.10 on Non
The uranium-bearing materials in the measured items and
Destructive Assay.
calibration reference materials used for calibration must fill the
Current edition approved Jan. 1, 2017. Published January 2017. Originally
approved in 2002. Last previous edition approved in 2008 as C1514 – 08. DOI:
detector field of view.
10.1520/C1514-08R17.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
the ASTM website. 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1514 − 08 (2017)
5.3 Use of a low resolution detector (for example, NaI 6.5 Any impurities present in the measured items must be
detector) to measure uranium with U fraction approximately homogeneously distributed and well characterized. The pres-
10 % which is contained in a thin-walled container can provide ence of impurities, at concentrations which can measurably
a rapid (typically 100 s), easily portable measurement system attenuate the 185.7 keV gamma-ray and which are not ac-
with precision of 0.6 % and bias of less than 1 %. counted for will result in a bias.
5.4 Use of a high resolution detector (for example, high- 6.6 The presence of radioactive impurities can affect the
purity germanium) can provide measurement with a precision determination of the 185.7 keV peak area. This type of
better than 0.2 % and a bias less than 1 % within a 300-s interference is most often encountered in low-resolution
measurement time when measuring uranium with U fraction measurement, but can affect high-resolution measurements.
in the range of 0.711 % or above which is contained in
6.7 Other factors, such as the paint on the outside of the
thin-walled containers.
cylinders and the condition of the cylinder inner walls after
5.5 In order to obtain optimum results using this method, exposure to UF , may affect the precision and bias for both the
the chemical composition of the item must be well known, the NaI and the HPGe measurement methods.
container wall must permit transmission of the 185.7 keV
7. Apparatus
gamma-ray, and the uranium-bearing material within the item
must be infinitely thick with respect to the 185.7 keV gamma-
7.1 Gamma-Ray Detector System—General guidelines for
ray. All items must be in identical containers or must have a
selection of detectors and signal-processing electronics are
known container wall thickness and composition.
discussed in Guide C1592, Test Method C1030, and ANSI
standard N42.14. Refer to the References section for a list of
5.6 Items to be measured must be homogeneous with
other recommended references (1). This system typically
respect to both U fraction and chemical composition.
consists of a gamma-ray detector, spectroscopy grade
5.7 When measuring items, using low-resolution detectors,
amplifier, high-voltage bias supply, multi-channel analyzer,
in thin-walled containers that have not reached secular equi-
and detector collimator. The system may also include detector
librium (more than about 120 days after processing), either the
backshielding,anultrasonicthicknessgauge,anoscilloscope,a
method should not be used, additional corrections should be
spectrum stabilizer, a computer, and a printer.
made to account for the age of the uranium, or high-resolution
7.2 A high-resolution detector system or a low-resolution
measurements should be performed.
detectorsystemshouldbeselected,dependingonprecisionand
5.8 The method is often used as a enrichment verification
bias requirements for the measurements. Additional detector
technique.
selection considerations are measurement time, cost, and ease
of use. High-resolution detector systems are generally larger,
6. Interferences
heavier, and more costly than low-resolution detector systems.
6.1 Appropriate corrections must be made for attenuating
Inaddition,thecostofhigh-resolutiondetectorsissignificantly
materials present between the uranium-bearing material and
higher (roughly an order of magnitude) than the cost of
the detector. Inappropriate correction for this effect can result
low-resolution detectors. High-resolution systems, however,
in significant biases.
provide better results than low-resolution systems, and elimi-
nate some interferences.
6.2 Incorrect knowledge of chemical form of the uranium-
7.2.1 High-Resolution Detector—Ahigh-resolution detector
bearing materials can result in a bias.
with a resolution of 1200 eV or better, full width at half
6.3 Depending on the dead-time correction method used,
maximum, at 122 keV is recommended. Either a planar or
excessive dead time can cause errors in live time correction
coaxial detector can be used, although excessive dead time can
and, thus, result in a measurement bias. Excessive dead time
resultifacoaxialdetectorwithhigh(>15 %)efficiencyisused.
can usually be eliminated by modifications to the detector
The selected detector should be of sufficient size (including a
collimator and aperture.
combination of surface area and thickness) to provide the
6.4 Background gamma-rays near 185.7 keV can result in a
desired counting-statistics based uncertainty within a reason-
bias. Table 1 is a list of interfering gamma-rays which may
able counting time.
cause an interference.
7.2.2 Low-Resolution Detector—A low-resolution detector
with the following specifications is recommended: a 5-cm
diam, 1.25-cm thick or larger detector with a resolution of
15 % or better at 122 keV.
TABLE 1 Interfering Gamma-Rays
7.2.3 Collimator and Shield Assembly—The detector colli-
Gamma-Ray Energy
Isotope Parent Measurement Affected
(keV)
mator and shield assembly must be of sufficient thickness to
Ra N/A 185.9 High Resolution,
attenuate in excess of 99.9 % of the 185.7 keV gamma-rays
Low Resolution
212 232
incident upon it. The detector collimator must also block in
Pb U 238.6 Low Resolution
224 232
Ra U 241.0 Low Resolution
excess of 99.9 % of the gamma-rays incident upon it and the
233 237
Pa Np 300.1 Low Resolution
233 237
Pa Np 311.9 Low Resolution
234 238
Th U Bremsstrahlung Low Resolution
Tc N/A Bremsstrahlung Low Resolution The boldface numbers in parentheses refer to the list of references at the end of
this standard.
C1514 − 08 (2017)
aperture must restrict the field of view of the detector so that required by regulations, the enrichment of the reference mate-
the uranium in the measured items and calibration reference rials used may need to span the range of anticipated enrich-
materials used for calibration completely fill the detector field ments for items to be measured. Use of the method outside the
of view. A filter (typically fabricated from cadmium or tin) range within which it was calibrated is possible due to the
may, optionally, be included to reduce the intensity of gamma- linearity of the calibration, but measurement uncertainty must
induced X rays from the collimator and shield assembly. be considered.
7.3 Preparation of Apparatus: 9.6 Determine the calibration constants and their uncertain-
7.3.1 Setup apparatus and set parameters according to ties using methods shown in Annex A1 and Annex A2,as
manufacturer instructions or site operating procedures. applicable to the method chosen for peak area determination.
10. Procedure
8. Hazards
10.1 Good measurement practice includes the measurement
8.1 Gamma-raydetectorsmayusepower-supplyvoltagesas
of an item used as a control source (refer to Guide C1592).
high as 5 kV. Appropriate precautions should be taken when
using, assembling, and disassembling these systems.
10.2 The uranium-bearing material within the measured
item must completely fill the field of view of the collimated
8.2 Collimators and shielding may use materials (for
detector in the geometry used for calibration.
example, lead and cadmium) which are considered hazardous
and/or toxic and can be physically heavy and difficult to
10.3 Precision for the net peak area should be adequate to
maneuver. Proper care in their use and disposal are required.
meet data quality objectives.
8.3 Uranium-bearing materials present both chemical and
10.4 Assess the peak background at the 185.7 KeV mea-
radiological hazards. The analyst should be aware of these
surement environment.
hazards and take appropriate precautions.
10.5 The area for the 185.7 keV peak must be determined
using the same method as was used for calibration (peak fitting
9. Calibration
or regions of interest). Refer to Table 1 for possible interfer-
9.1 Two types of reference materials are typically used for
ences.
performing calibration measurements: (1) certified reference
10.6 Obtain the wall thickness, and material composition
materials, and (2) secondary reference materials. Containers in
and density for the item’s container.
the same configuration as the items to be measured are
preferred. 10.7 Document the identifier for the measured item, the
9.1.1 Certified reference materials are commercially avail- chemical form of uranium-bearing material contained in the
able which have been fabricated for the primary purpose of item, the counting time used, the net peak area and its
calibration of gamma-ray systems for enrichment measure- uncertainty (or the information needed to compute the net peak
ments using the enrichment meter principle. area and its uncertainty), and the wall thickness and material.
9.1.2 Secondary reference materials can be fabricated by Other information can be recorded as desired.
analyzing for enrichment using destructive analysis techniques
10.8 Compute the attenuation correction factor and its
which have been calibrated with a traceable reference material.
uncertainty using equations shown in Annex A1.
9.2 Fillthefieldofviewforthecollimateddetector,withthe
10.9 Use appropriate corrections to account for different
uranium in the reference material.
chemical forms verses that used during calibration. See Refer-
9.3 Measure the reference material for a sufficient amount ences (2) and (3).
of time to obtain the desired precision for the net peak area.
10.10 Compute the enrichment and the measurement uncer-
The precision for the net peak area should be smaller (a factor
tainty using equations shown in Annex A1 or Annex A2,as
of ten is recommended) than the target overall measurement
appropriate.
system uncertainty.
11. Precision and Bias
9.4 Record the identifier for the measured item, the type of
uranium-bearing material contained in the item, the counting 11.1 Precision and bias are dependent on several factors,
time used, the net peak area and its uncertainty (or the including (but not limited to): measurement time, accuracy of
information needed to compute the net peak area and its wall thickness correction factor determination, wall thickness,
uncertainty), and the wall thickness and material. Other infor- purity of the measured items, collimation, and calibration
mation can be recorded as desired. The area for the 185.7 keV uncertainty. In general, the measurement can be tailored to
peakcanbedeterminedusingpeakfittingorregionsofinterest. provide the level of precision and bias required. The level of
Ifregionsofinterestareusedtodeterminetheareaofthe185.7 precision is, therefore, typically governed by practical consid-
keV peak, record the gross counts for each region to be used. erationsandbytheneedsofthemeasurementprogramanddata
quality objectives.
9.5 Repeat steps 9.2 – 9.4 for other reference materials. The
measurement of at least one additional item (total of two) is 11.2 Table 2 demonstrates that the calibration of the method
recommended for calibration of high-resolution systems. The is linear. Using a calibration performed with reference materi-
measurement of at least two additional items (total of three) is als ranging in enrichment from 0.31 wt % to 4.46 wt %,
recommended for calibration of low-resolution systems. If containers ranging in enrichment from 12.08 wt % to 97.54
C1514 − 08 (2017)
TABLE 2 Measurement of Highly Enriched Uranium in 5A Cylinders (UF )andZCans(U O ) Using an HPGe Detector (3)
6 3 8
Item Container Declared Measured U Difference Rel. Diff.
235 A
Number Type U (wt %) (wt %) (wt %) (%)
1 5A 12.08 12.13 0.05 0.4
2 5A 26.44 25.68 −0.76 −2.9
3 5A 44.08 43.28 −0.8 −1.8
4 5A 54.62 55.02 0.4 0.7
5 5A 64.89 64.6 −0.29 −0.4
6 5A 73.21 73.98 0.77 1.1
7 5A 97.60 94.8 −2.77 −2.8
8 Z 22.20 22.51 0.31 1.4
9 Z 33.73 33.41 −0.32 −0.9
10 Z 45.50 44.58 −0.92 −2
11 Z 56.20 57.27 1.07 1.9
12 Z 61.51 58.26 −3.25 −5.3
13 Z 86.57 89.31 2.74 3.2
14 Z 97.54 93.3 −4.24 −4.3
B
Average −0.57 −0.9
Standard Deviation 1.83 2.5
A
Measurement conditions: Items were measured for 100 s each using a planar HPGe detector. Calibration was performed using five certified reference standards ranging
in enrichment from 0.31 to 4.46 wt% U and 300 s count times. Nominal wall thickness for 5A cylinders is 0.635 cm of nickel. Nominal wall thickness of Z cans is 0.0381
cm of stainless steel.
B
Not significant at the 95 % confidence level.
wt % were measured (that is, the instrument was used outside steel up to 1.27 cm thick. Ten replicate measurements were
its calibration range). The average bias for this set of measure- madeofreferencematerialintwomeasurementconfigurations:
ments was –0.9 % relative. Table 3 demonstrates that this (1) the reference source alone, and (2) the reference source
linearity extends to lower enrichments (as low as 0.3206 placed behind 1.27 cm of steel to represent a thick-walled
wt %). A set of measurements performed using a single linear container. Using a single-tailed F test to test for observed
calibration based on measurement of three sources with mea- standard deviation larger than the standard deviation predicted
suredenrichmentsextendingfrom0.3206wt %to91.419wt% by counting statistics, neither of the two F values were
has an average bias of 0.9 %. statistically significant at
...