ASTM C1625-05

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:C1625–05
Standard Test Method for
Uranium and Plutonium Concentrations and Isotopic
Abundances by Thermal Ionization Mass Spectrometry
This standard is issued under the fixed designation C1625; 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 C1347 Practice for Preparation and Dissolution of Uranium
Materials for Analysis
1.1 This test method covers the determination of the con-
C1411 Practice for The Ion Exchange Separation of Ura-
centration and isotopic composition of uranium and plutonium
nium and Plutonium Prior to Isotopic Analysis
in solutions. The purified uranium or plutonium from samples
C1415 TestMethodfor PuIsotopicAbundanceByAlpha
ranging from nuclear materials to environmental or bioassay
Spectrometry
matrices is loaded onto a mass spectrometric filament. The
D3084 Practice for Alpha-Particle Spectrometry of Water
isotopic ratio is determined by thermal ionization mass spec-
2.2 Other Documents
trometry, the concentration is determined by isotope dilution.
International Target Values 2000 for Measurement Uncer-
1.2 This standard does not purport to address all of the
tainties in Safeguarding Nuclear Materials
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish safety
3. Summary of Test Method
and health practices and determine the applicability of regu-
3.1 The uranium and plutonium are separated from each
latory limitations prior to use.
other and purified from other elements by selective extraction,
2. Referenced Documents anion exchange (such as in C1411) or extraction chromatog-
raphy. The uranium and plutonium fractions are individually
2.1 ASTM Standards:
mounted on rhenium filaments and analyzed by thermal
C753 Specification for Nuclear-Grade, Sinterable Uranium
ionization mass spectrometry to determine the relative abun-
Dioxide Powder
233 242 244
danceoftheisotopes.Ifaknown Uor Pu(or Pu)spike
C757 Specification for Nuclear-Grade Plutonium Dioxide
is added prior to chemical separation the corresponding el-
Powder, Sinterable
emental concentration may also be determined by isotope
C776 Specification for Sintered Uranium Dioxide Pellets
dilution mass spectrometry (IDMS).
C833 Specification for Sintered (Uranium-Plutonium) Di-
oxide Pellets
4. Significance and Use
C1008 Specification for Sintered (Uranium-Plutonium) Di-
4.1 Uraniumandplutoniumoxidescanbeusedasanuclear-
oxide Pellets—Fast Reactor Fuel
reactorfuelintheformofpellets.Inordertobesuitableforuse
C1068 GuideforQualificationofMeasurementMethodsby
as a nuclear fuel the starting material must meet certain
a Laboratory Within the Nuclear Industry
specifications, such as found in C757, C833, C753, C776,
C1156 Guide for Establishing Calibration for a Measure-
C1008, or as specified by the purchaser. The uranium and/or
ment Method Used to Analyze Nuclear Fuel Cycle Mate-
plutoniumconcentrationandisotopicabundancesaremeasured
rials
by mass spectrometry following this test method.
C1168 Practice for Preparation and Dissolution of Pluto-
4.2 The separated heavy element fractions placed on mass
nium Materials for Analysis
spectrometric filaments must be very pure. The quantity
required depends upon the sensitivity of the instrument detec-
This test method is under the jurisdiction ofASTM CommitteeC26 on Nuclear
tion system. If an electron multiplier detector is to be used,
Fuel Cycle and is the direct responsibility of Subcommittee C26.05 on Methods of
only a few nanograms are required. If a Faraday cup is used, a
Test.
few micrograms are needed. Chemical purity of the sample
Current edition approved June 1, 2005. Published October 2005. DOI: 10.1520/
C1625-05.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM H. Aigner et. al., “International Target Values 2000 for Measurement Uncer-
Standards volume information, refer to the standard’s Document Summary page on tainties in Safeguarding Nuclear Materials,” International Atomic Energy Agency
the ASTM website. STR-327, 2001.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
C1625–05
becomes more important as the sample size decreases, because purity available. Other grades may be used if they are deter-
ion emission of the sample is suppressed by impurities. mined not to affect the final result.
7.2 Filaments—high purity, the size and configuration are
5. Interferences
instrument dependent. Filaments should be degassed, and
5.1 Uranium-238 and Pu interfere in the measurement of
maybe carbon saturated, prior to use.
each other, and Am interferes with the measurement of
NOTE 1—The purity of the filaments should be confirmed with each
Pu, thereby requiring chemical separation. Removal of
batch received. Zone refined filaments should be used for low-level
impurities provides uniform ionization of uranium or pluto-
analyses.
nium, hence improved precision, and reduces the interference
from molecular species of the same mass number as the
7.3 Certified Reference Materials (CRM)—of varying iso-
uraniumorplutoniumisotopesbeingmeasured.Isotopicanaly-
topic composition, traceable to a national standard body , for
sis of plutonium should be completed within a reasonable time
use as calibration and quality control standards.
period (approximately 20 days) after separation from ameri-
7.4 Spikes—Materials, preferably CRMs, for use in the
241 241
cium to minimize interference of Am ingrowth from Pu.
determination of elemental concentration by IDMS.
5.2 Extreme care must be taken to avoid contamination of
the sample by environmental uranium. The level of uranium
8. Instrument Calibration
contamination should be measured by analyzing an aliquot of
8M nitric acid as a reagent blank and calculating the amount of
8.1 The measurement method may be qualified following
uranium it contains.
C1068 and calibrated following C1156.
5.3 When Pu is present in low abundance it may be
8.2 The measurement and correction for mass discrimina-
necessary to measure it by alpha-spectrometry following
tion and dead time are critical factors in obtaining precise and
C1415 or D3084.
accurate results. Equally critical to the accuracy of the mea-
surementisthelinearityofthetotalmeasuringcircuitincluding
6. Apparatus
the collector. Calibration of the mass spectrometer is based on
6.1 Mass Spectrometer—The suitability of mass spectrom-
theassumptionthatthesearetheonlysourcesofsignificant(>1
etersforusewiththistestmethodofanalysisshallbeevaluated 4
in 10 ) systematic error in the measurement. Thus, accurate
by means of performance tests described in this test method
calibration is made by analyzing standards of known isotopic
and in Practice . The mass spectrometer used should possess
composition under conditions in which cross-contamination
the following characteristics:
between samples does not occur.
6.1.1 A thermal ionization source with single or multiple
8.2.1 For multi-collector systems, the bias between collec-
filaments of rhenium, tungsten or tantalum.
tors may also be an important factor in the systematic error and
6.1.2 An analyzer radius sufficient to resolve adjacent
thus must also be evaluated prior to making measurements.
masses in the mass-to-charge range being studied, that is, m/z
+ +
= 233 to 238 for U or 238 to 244 for Pu . Abundance
8.2.2 For very low-level samples, or samples with extreme
sensitivity must be great enough to detect one part of Uin
ratios, other corrections may need to be made, e.g. dark count
400 parts U.
data/dark current.
6.1.3 Aminimum of one stage of magnetic deflection. Since
8.3 Mass Discrimination—Useatraceableisotopicstandard
the resolution is not affected, the angle of deflection may vary
to determine the mass discrimination. The deviation from the
with the instrument design.
certified value of the 235/238 ratio (for U) or the 239/242 ratio
6.1.4 A mechanism for changing samples.
(for Pu) is a measure of the mass discrimination of the mass
6.1.5 A direct-current (Faraday cup) or electron multiplier
spectrometer.
detector, as a single detector system or, several detectors in a
8.3.1 Calculate the elemental mass discrimination bias fac-
multicollectordesign,followedbyacurrentmeasuringdevice.
tor, B, as follows:
6.1.6 Apumping system to attain a vacuum of less than 400
-6
µPa (3 3 10 torr) in the source, the analyzer, and the detector
B 5 ~1/c!@~aR /R !21] (1)
i/j s
regions.
where:
6.1.7 Amechanism to scan masses by means of varying the
B = mass discrimination factor,
magnetic field or the accelerating voltage.
aR = average measured atom ratio of isotope i to isotope
i/j
6.1.8 A computer to collect and process data produced by
j
the instrument.
R = certified atom ratio value of the CRM
s
6.2 An Optical Pyrometer should be available to determine
c = Dmass/mass.Thevaluesfor cforvariousratiosand
the filament temperature.
ion species include:
6.3 Filament preheating and degassing unit for cleaning
unloaded filaments.
7. Materials and Reagents
7.1 Purity of Reagents—all reagents used in the final
Available from USDOE New Brunswick Laboratory, Argonne, IL, or other
purification and filament loading steps should be of the highest equivalent source.
C1625–05
+ +
emitting temperatures are 1450-1650°C for plutonium and
ratio U or Pu
235 238
U/ U +3/238
1650-1850°C for uranium.
236 235
U/ U -1/235
233 238 9.3.4 Locate the uranium or plutonium spike peak,
U/ U +5/238
238 239
234 235
or the U peak or the Pu peak, if analyzing unspiked
U/ U +1/235
242 239
Pu/ Pu -3/239
samples. Focus the major isotope beam by adjusting the
240 239
Pu/ Pu -1/239
magnetic field, the accelerating voltage, and any electrical or
241 239
Pu/ Pu -2/239
238 239
mechanical controls available.
Pu/ Pu +1/239
9.3.5 Theintensityofthemajorbeamisadjusteduntilstable
8.3.2 Correct every measured ratio, R , for mass discrimi-
i/j
emission of the desired intensity is achieved.The emission rate
nation as follows:
should be constant or at least increase or decrease slowly and
R 5aR /~11cB! (2)
i/j i/j
evenly.
where R is the corrected atom ratio of isotope i to isotope
9.3.6 When acceptable ion emission is reached, measure the
i/j
j
relative intensities of the ion peaks of interest. Multiple
8.4 Dead Time Correction—Required for counting detec-
measurements of isotope pairs are made to provide quality
tors, at high count rates. Use laboratory protocols for this
control parameters.
correction with high count rate samples.
9.3.7 Whensufficientdataarecollectedtoobtainthedesired
8.5 Linearity—The linearity of the mass spectrometer may
precision, turn off the filament current and discontinue the
be determined over the working ratio range by measuring
analysis.
235 238
the U/ U ratio, under identical conditions, of appropriate
9.3.8 Record and correct (see section 8) the isotopic ratios
235 238
CRMs. The ratio of the certified U/ U ratio to the experi-
of the ith to the jth species for the unspiked sample (R ), for
i/j
235 238
mental U/ U ratio is independent of isotopic ratio if the
the spike, (S ) and for the sample-plus-spike mixture (M ).
i/j i/j
233 234 235 236 238
system is linear. Under ideal conditions, any deviation from a
The symbols for the isotopes U, U, U, U, U,
238 239 240 241 242
constant value greater than 4 in 10,000 is likely to be
Pu, Pu, Pu, Pu, and Pu are abbreviated to 3, 4, 5,
nonlinearity. Uranium CRMs are used because the range of
6, 8, P8, 9, 0, 1, and 2, respectively (see section 10); note that
isotopic ratios of existing plutonium CRMs is not adequately
these symbols do not include every isotope that may be
large.
measured. In this nomenclature, the observed ratios of U
to U in the sample, the spike, and the sample-plus-spike
9. Procedure
mixture (R , S and M ) become R , S and M , respec-
i/j i/j i/j 8/3 8/3 8/3
tively.
9.1 Sample Preparation
9.1.1 Sample Dissolution—Dissolve an appropriate sample
to obtain the desired filament loading for the mass spectromet- 10. Calculation
ric analysis. See C1347 for the dissolution of uranium or
10.1 Calculate atom fraction U, A , on the unspiked U as
C1168 for plutonium.Add the appropriate amount of spike, by
follows:
weight or volume, as appropriate, if concentration is to be
A 5 R /~R 1 R 1 R 1 R ! (3)
5 5/8 4/8 5/8 6/8 8/8
determined by isotope dilution methods.
where R (which equals 1) is retained for clarity. Next,
8/8
NOTE 2—Spike addition and equilibration must be performed prior to
calculate atom fraction U, A , as follows:
chemical purification if determining concentration by IDMS.
A 5 R /~R 1 R 1 R 1 R ! (4)
8 8/8 4/8 5/8 6/8 8/8
9.1.2 Sample Purification—Use C1411 or similar procedure
In these equations, U is assumed to be the principal
to separate the uranium and plutonium from each other and
isotope. For highly enriched U where U is the principal
from other impurities.
isotope, obtain the ratio of each isotope to U instead of
9.2 Filament Loading—Samples may either be directly
to U by using R ,R ,R ,R in place of R ,R ,
loaded by evaporation, electroplated, or loaded onto a resin
4/5 5/5 6/5 8/5 4/8 5/8
R , and R . Finally, calculate the atom % N and N as
bead for mounting on the filament. Samples and standards
6/8 8/8 5 8
follows:
should be prepared for analysis by the same method at similar
mass loadings.
N 5 100A (5)
5 5
9.3 Sample Heating and Isotopic Ratio Measurement:
9.3.1 Insert the filament assembly into the mass spectrom-
N 5 100A (6)
8 8
eter. If the instrument contains a turret to allow loading of
If desired, calculate N and N similarly by dividing the
4 6
several samples, load at least one QC sample (blank or CRM)
corresponding atom ratio by the same sum of four ratios as
per wheel.
shown in Eq 3 and Eq 4 and by multiplying the resultant atom
9.3.2 Seal the source and evacuate to a pressure of less than
-6 fraction by 100 to obtain percent as shown in Eq 5 and Eq 6.
400 µPA (3 3 10 torr).
10.2 Calculate the corresponding atom fraction Pu, A ,
9.3.3 Slowly begin heating the sample filament. If not done
and atom percent Pu, N , on the unspiked Pu fraction as
previously, hold the sample filament at a dull, red glow
follows:
(500-700°C) for 5-30 minutes to permit outgassing (this may
A 5 R / ~R 1 R 1 R 1 R ! (7)
be performed in a separate system to reduce contamination of
9 9/9 9/9 0/9 1/9 2/9
the mass spectrometry source). When outgassing has ceas
...