ASTM C1221-10(2018)

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:C1221 −10 (Reapproved 2018)
Standard Test Method for
Nondestructive Analysis of Special Nuclear Materials in
Homogeneous Solutions by Gamma-Ray Spectrometry
This standard is issued under the fixed designation C1221; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
1.1 This test method covers the determination of the con-
2.1 ASTM Standards:
centration of gamma-ray emitting special nuclear materials
C1133/C1133MTest Method for Nondestructive Assay of
dissolved in homogeneous solutions. The test method corrects
SpecialNuclearMaterialinLow-DensityScrapandWaste
for gamma-ray attenuation by the solution and its container by
by Segmented Passive Gamma-Ray Scanning
measurement of the transmission of a beam of gamma rays
C1168PracticeforPreparationandDissolutionofPlutonium
from an external source (Refs. (1), (2), and (3)).
Materials for Analysis
1.2 Two solution geometries, slab and cylinder, are consid- C1490GuidefortheSelection,TrainingandQualificationof
ered.The solution container that determines the geometry may Nondestructive Assay (NDA) Personnel
be either a removable or a fixed geometry container. This test
C1592/C1592MGuide for Making Quality Nondestructive
method is limited to solution containers having walls or a top
Assay Measurements (Withdrawn 2018)
and bottom of equal transmission through which the gamma
C1673Terminology of C26.10 NondestructiveAssay Meth-
rays from the external transmission correction source must
ods
pass.
E181Test Methods for Detector Calibration andAnalysis of
Radionuclides
1.3 This test method is typically applied to radionuclide
concentrations ranging from a few milligrams per litre to
2.2 ANSI Standards:
several hundred grams per litre. The assay range will be a
ANSI N15.20Guide to Calibrating Nondestructive Assay
function of the specific activity of the nuclide of interest, the
Systems
physical characteristics of the solution container, counting
ANSI N15.35Guide to Preparing Calibration Material for
equipment considerations, assay gamma-ray energies, solution
NondestructiveAssaySystemsthatCountPassiveGamma
matrix, gamma-ray branching ratios, and interferences.
Rays
1.4 This standard does not purport to address all of the ANSI N15.37Guide to the Automation of Nondestructive
safety concerns, if any, associated with its use. It is the
Assay Systems for Nuclear Material Control
responsibility of the user of this standard to establish appro-
ANSI N42.14American National Standard for Calibration
priate safety, health, and environmental practices and deter-
and Use of Germanium Spectrometers for the Measure-
mine the applicability of regulatory limitations prior to use.
ment of Gamma-Ray Emission Rates of Radionuclides
For specific hazards, see Section 9.
ANSI/IEEE 645Test Procedures for High-Purity Germa-
1.5 This international standard was developed in accor-
nium Detectors for Ionizing Radiation
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
3. Terminology
Development of International Standards, Guides and Recom-
3.1 Fordefinitionsoftermsusedinthistestmethod,referto
mendations issued by the World Trade Organization Technical
Committee C26.10’s Terminology standard, C1673.
Barriers to Trade (TBT) Committee.
1 3
ThistestmethodisunderthejurisdictionofASTMCommitteeC26onNuclear For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Fuel Cycle and is the direct responsibility of Subcommittee C26.10 on Non contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Destructive Assay. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved April 1, 2018. Published April 2018. Originally the ASTM website.
approved in 1992. Last previous edition approved in 2010 as C1221–10. DOI: The last approved version of this historical standard is referenced on
10.1520/C1221-10R18. www.astm.org.
2 5
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
this test method. 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
C1221−10 (2018)
4. Summary of Test Method
4.1 Manynuclearmaterialsspontaneouslyemitgammarays
with energies and intensities characteristic of the decaying
nuclide. The analysis for these nuclear materials is accom-
plished by selecting appropriate gamma rays and measuring
their intensity to identify and quantify the nuclide.
4.1.1 The gamma-ray spectrum of a portion of solution is
obtained with a collimated, high resolution gamma-ray detec-
tor.
4.1.2 Count-rate-dependent losses are determined and cor-
rections are made for these losses.
4.1.3 A correction factor for gamma-ray attenuation in the
solution and its container is determined from the measurement
of the transmitted intensity of an external gamma-ray source.
The gamma rays from the external source have energies close
NOTE 1—The sample geometry in this case is a slab. (Not to scale.)
to those of the assay gamma rays emitted from the solution.
FIG. 2Schematic of an Uplooking Configuration
Figs. 1 and 2 illustrate typical transmission source, solution,
and detector configurations. Gamma rays useful for assays of
TABLE 1 Suggested Nuclide/Source Combinations
235 239
U and Pu are listed in Table 1.
Count
Peak Peak Peak
Transmission Rate
4.1.4 The relationship between the measured gamma-ray
Nuclide Energy Energy Energy
Source Correction
intensity and the nuclide concentration (the calibration con- (keV) (keV) (keV)
Source
stant) is determined by use of appropriate standards (ANSI
235 169 241
U 185.7 Yb 177.2 Am 59.5
N15.20, ANSI N15.35, and Guide C1592/C1592M).
198.0
239 75 133
Pu 413.7 Se 400.1 Ba 356.3
4.2 In the event that the total element concentration is
239 57 109
Pu 129.3 Co 122.1 Cd 88.0
desired and only one isotope of an element is determined (for 136.5
example, Pu), the isotopic ratios must be measured or
estimated.
5.4 The test method assumes that the solution-detector
5. Significance and Use
geometry is the same for all measured items. This can be
5.1 Thistestmethodisanondestructivemeansofdetermin-
accomplished by requiring that the liquid height in the side-
ing the nuclide concentration of a solution for special nuclear
lookinggeometryexceedsthedetectorfieldofviewdefinedby
material accountancy, nuclear safety, and process control.
the collimator. For the upward-looking geometry, a fixed
solution fill height must be maintained and vials of identical
5.2 It is assumed that the nuclide to be analyzed is in a
radii must be used unless the vial radius exceeds the field of
homogeneous solution (Practice C1168).
view defined by the collimator.
5.3 The transmission correction makes the test method
5.5 Since gamma-ray systems can be automated, the test
independent of matrix (solution elemental composition and
method can be rapid, reliable, and not labor intensive.
density)andusefuloverseveralordersofmagnitudeofnuclide
concentrations. However, atypical configurationwill normally
5.6 This test method may be applicable to in-line or off-line
spanonlytwotothreeordersofmagnitudebecauseofdetector
situations.
dynamic range.
6. Interferences
6.1 Radionuclides may be present in the solution, which
produce gamma rays with energies that are the same or very
nearly the same as the gamma rays suggested for nuclide
measurement,countratecorrection,ortransmissioncorrection.
Thus,thecorrespondingpeaksinthegamma-rayspectrummay
be unresolved and their areas may not be easily determined
unless multiplet fitting techniques are used. In some cases, the
nuclideofinterestmayemitothergammaraysthatcanbeused
foranalysisoralternativetransmissionorcountratecorrection
sources may be used.
6.1.1 Occasionally,asignificantamountof Npisfoundin
237 233
a plutonium solution. The Np daughter, Pa, emits a
gamma ray at 415.8 keV as well as other gamma rays in the
300 to 400 keVregion.These Pa gamma rays may interfere
NOTE1—Thesamplegeometrymaybeeithercylindricaloraslab.(Not
with the analysis of Pu at 413.7 keV and at several other
to scale.)
FIG. 1Schematic of a Sidelooking Configuration normally useful Pu gamma-ray energies. In this case,
C1221−10 (2018)
the Pu gamma ray at 129.3 keV may be a reasonable 6.2.2 Use solution containers that are free of outer surface
alternative. In addition, the 398.7 keV gamma ray from Pa contamination. Remove any contamination from the instru-
may interfere with the transmission corrections based on the mentthatmayinterferewithanalyses.Itmaynotbepossibleto
400.7 keV Se gamma-ray measurements. Multiple fitting completelydecontaminatein-lineinstrumentation.Inthiscase,
techniques can resolve these problems. the contamination should be minimized to the extent practical.
169 235
6.2.3 The measurement of background should be made at
6.1.2 Yb,usedasthetransmissionsourcefor Uassays,
various times during the day. Varying backgrounds can be
emits a 63.1 keV gamma ray that may interfere with the
caused by process activities that often occur on regular
measurementoftheareaofthepeakproducedbythe59.5keV
schedules. These time-dependent backgrounds might not be
gamma ray of Am, which is commonly used as the count
detected if the background is checked at the same time each
rate correction source. The 63.1 keV Yb gamma ray should
day.
be attenuated by placing a cadmium absorber over the trans-
mission source. Cd may be a suitable alternative count rate
6.3 High-energy gamma rays from fission products in the
correction source.
solution will increase the Compton background and decrease
239 75
6.1.3 In the special case of Pu assays using Se as a
the precision of gamma-ray intensity measurements in the
transmission source, random coincident summing of the 136.0
lower energy (<500 keV) region of the spectrum.
and279.5keVgamma-rayemissionsfrom Seproducesalow
6.4 Low energy X- and gamma rays from either the trans-
intensity sum peak at 415.5 keV that interferes with the peak
mission or count rate correction source may contribute signifi-
area calculation for the peak produced by the 413.7 keV
cantly to the total system electronic pulse rate causing in-
gamma ray from Pu. The effects of this sum peak interfer-
creased count rate losses and sum peak interferences. An
ence can be reduced by using absorbers to attenuate the
absorber should be fixed between the source and detector to
radiation from the Se to the lowest intensity required for
reduce the number of low energy X-rays detected.
transmission measurements of acceptable precision. The prob-
7. Apparatus
lem can be avoided entirely by making two separate measure-
mentsoneachitem/solution;first,measurethepeakareaofthe
7.1 Gamma-Ray Detector System—General guidelines for
transmission source with the solution in place and second,
selection of detectors and signal-processing electronics are
measure the peak area of the assay gamma ray while the
discussed in Guide C1592/C1592M, and ANSI N42.14. Refer
detector is shielded from the transmission source. An addi-
to the References section for a list of other recommended
tional benefit of the “dual scan” is a better signal to noise ratio
references. This system typically consists of a gamma-ray
in the individual spectra.
detector, spectroscopy grade amplifier, high-voltage bias
239 241
6.1.4 In Pu solutions with high activities of Am
supply, multi-channel analyzer, and detector collimator. The
or U, or both, the Compton continuum from intense 208.0
systemmayalsoincludeanoscilloscope,aspectrumstabilizer,
keV gamma rays may make the 129.3 keV gamma ray from
a computer, and a printer. General guidelines for selection of
Pu unusable for assays. Also, the 416.0 keV sum peak that
detectors and signal-processing electronics are discussed in
resultsfrompileupofthe208.0keVgammaraysmayinterfere
Guide C1592/C1592M. Data acquisition systems are consid-
with the 413.7 keV gamma ray from Pu. Use an absorber
ered in ANSI N15.37. It is recommended that the system be
(for example, 0.5 to 0.8 mm of tungsten) between the detector
implemented by an NDA Professional (C1490). The system
and solution to attenuate the 208.0 keV gamma rays. This will
should have the following components:
attenuatetheintensityofthelowerenergygammaraysandalso
7.2 High Resolution, Germanium, Gamma-Ray
reduce the sum peak interference. The resulting Pu assay
Detector—A coaxial-type detector with full width at half
will be based on the 413.7 keV gamma ray.
maximum (FWHM) resolution typically 1000 eV or better at
6.1.5 X-rays of approximately 88 keV from lead in the
122 keV may be used for the analysis. A planar-type detector
shielding may interfere with the measurement of the 88.0 keV
withsimilarresolutionmayalsobeused.Thestatedresolutions
gamma-ray peak when Cd is used as the count rate correc-
areforguidanceonly.Theselectionofdetectortype,coaxialor
tion source. Graded shielding (4) is required to remove the
planar, should be based on the usual considerations of effi-
interference.
ciencyandresolutionrequiredforthespecificapplication.Test
procedures for detectors are given in Test Methods E181 and
6.2 Peaks may appear in the spectrum at gamma-ray ener-
ANSI/IEEE 645.
gies used for analysis when there is no solution present. This
may be caused by excessive amounts of radioactive material
7.3 DetectorCollimator—Thecollimatordefinesthefieldof
storedinthevicinityofthedetectororbycontaminationofthe
view of the detector to a reproducible solution geometry and
instrument. This can cause variable and unacceptably high
shields the detector from ambient radiation. This test method
backgrounds leading to poor measurement quality.
addresses two potential solution/collimator geometries that
6.2.1 Remove unnecessary radioactive material from the will dictate the analytical expression used. Other designs
vicinity and also restrain movement of radioactive material require case-by-case assessment.
around the assay area during measurements. Shielding should 7.3.1 The collimator in the slab geometry (both upward
be provided that completely surrounds the detector with the looking and sidelooking) is a cylindrical hole with its axis
exception of the collimator opening. Shielding opposite the normal to the slab.The diameter of the collimator should limit
detector on the far side of the solution will also reduce the the field of view of the detector to within the solution volume
amount of ambient radiation incident on the detector. (see Figs. 1 and 2).
C1221−10 (2018)
7.3.2 Thecollimatorinthecylindricalgeometryshouldbea 7.8 Solution Container—Either a removable solution vial
slit perpendicular to the axis of the solution. The field of view withreproduciblegamma-raypathlengthandwallthicknessor
in this case is within the solution volume in the axial direction a fixed-path-length flow-through cell. Low atomic number
(see Fig. 1) and includes the entire solution volume in the material should be used in container production to reduce
radial direction (Fig. 3). absorption of assay gamma-rays. The equations presented in
thistestmethodapplyonlytosolutioncontainerswithwallsor
7.4 Absorber Foils—Absorbers are used to reduce the over-
a top and bottom of equal transmission for the cylindrical and
all count rate due to low energy X-rays and gamma rays from
slab geometry configurations, respectively.
the solution, transmission source, and count rate correction
source. The absorbers are usually cadmium, tin or copper, or
8. Reference Materials
combination. Any change of these absorbers requires recali-
bration of the assay system.
8.1 Calibration of the assay system involves using a set of
standards to determine the relationship between the observed,
7.5 Count Rate Correction Source—To minimize
corrected count rate of the characteristic gamma ray of a
interferences, the source should be chosen to have gamma-ray
nuclide and the concentration of the nuclide known to be
energies lower than the gamma rays of interest. The source
present. After correcting for background, rate-related losses,
must be fixed relative to the detector, and its beam relative to
and attenuation effects, a direct proportionality constant is
the detector must not be attenuated by the solution. See Table
determined between count rate and nuclide concentration.
1 for suggested gamma-ray sources. Alternatively, commer-
cially available high precision electronic pulsers may be used
8.2 Prepare at least three calibration standards for each
for count rate correction. nuclide to be assayed. Standards should span the expected
concentration range of solution. The use of three calibration
7.6 Transmission Source—The transmission source should
standardswillverifythevalidityofthetransmissioncorrection
preferably emit gamma rays that bracket the energy of the
and the linearity of the instrument. More than three standards
assay gamma ray from the nuclide of interest.Asingle gamma
may be required if the instrument covers a wide concentration
ray with an energy near the assay gamma ray may be used.
range.
Table 1 provides a list of suggested nuclides for use as
8.2.1 The standards should be certified to contain a known
transmission sources with nuclides of interest. The source
nuclide concentration by an alternative technique traceable to
activity should typically be a few tens of millicuries. Where a
certified reference materials.
two-measurement assay (as described in 6.1.3) will be used,
8.2.2 Standards should be in a matrix providing transmis-
construct the instrument such that the detector can be shielded
sionssimilartothoseexpectedforsolutionsandbeinthesame
from the transmission source during measurement of the assay
container geometry to be used for solution assays.
gamma rays. A computer controlled shutter between the
transmission source and solution is ideal for this purpose in an 8.3 Mathematical calibrations benchmarked to traceable
automated system. The transmission source should be placed
sources may be used in place of physical reference materials.
opposite the detector and shine through the aperture of the Any calibration must be verified with a working standard or
detector collimator as illustrated in Fig. 1. The transmission source.
source should shine through the diameter of the solut
...