ASTM C1168-23

Standard Practice for Preparation and Dissolution of Plutonium Materials for Analysis

SIGNIFICANCE AND USE
5.1 Plutonium and uranium mixtures are used as nuclear reactor fuels. For use as a nuclear reactor fuel, the material must meet certain criteria for combined uranium and plutonium content, effective fissile content, and impurity content as described in Specifications C757 and C833. After dissolution using one of the procedures described in this practice, the material is assayed for plutonium and uranium to determine if the content is correct as specified by the purchaser.  
5.2 Unique plutonium materials, such as alloys, compounds, and scrap metals, are typically dissolved with various acid mixtures or by fusion with various fluxes. Many plutonium salts are soluble in hydrochloric acid. One or more of the procedures included in this practice may be effective for some of these materials; however their applicability to a particular plutonium material shall be verified by the user.
SCOPE
1.1 This practice is a compilation of dissolution techniques for plutonium materials that are applicable to the test methods used for characterizing these materials. Dissolution treatments for the major plutonium materials assayed for plutonium or analyzed for other components are listed. Aliquots of the dissolved materials are dispensed on a mass basis when one of the analyses must be of high precision, such as plutonium assay; otherwise they are dispensed on a volume basis.  
1.2 Procedures in this practice are intended for the dissolution of plutonium metal, plutonium oxide, and uranium-plutonium mixed oxides. Aliquots of dissolved materials are analyzed using test methods, such as those developed by Subcommittee C26.05 on Methods of Test, to demonstrate compliance with applicable requirements. These may include product specifications such as Specifications C757 and C833.  
1.3 One or more of the procedures in this practice may be applicable to unique plutonium materials, such as alloys, compounds, and scrap materials. The user must determine the applicability of this practice to such materials.  
1.4 The treatments, in order of presentation, are as follows:    
Procedure Number  
Procedure Title  
Section  
1  
Dissolution of Plutonium Metal with Hydrochloric Acid at Room Temperature  
9  
2  
Dissolution of Plutonium Metal with Hydrochloric Acid and Heating  
10  
3  
Dissolution of Plutonium Metal with Sulfuric Acid  
11  
4  
Dissolution of Plutonium Oxide and Uranium-Plutonium Mixed
Oxide by the Sealed-Reflux Technique  
12  
5  
Dissolution of Plutonium Oxide and Uranium-Plutonium Mixed Oxides by Sodium Bisulfate Fusion  
13  
6  
Dissolution of Uranium-Plutonium Mixed Oxides and Low-Fired Plutonium Oxide in Beakers  
14  
7  
Open-Vessel (with Reflux Condenser) Dissolution of Plutonium Oxide Powder  
15  
8  
Open-Vessel (with Reflux Condenser) Dissolution of Mixed Oxide Powder  
16  
9  
Closed-Vessel Hot Block Dissolution of Plutonium Oxide Powder  
17  
10  
Open-Vessel (with Reflux Condenser) Dissolution of Mixed Oxide Pellets  
18  
1.5 The values stated in SI units are to be regarded as standard. The non-SI unit of molarity (M) is also to be regarded as standard. Values in parentheses (non-SI units), where provided, are for information only and are not considered standard.  
1.6 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.7 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.

General Information

• Status: Published
• Publication Date: 30-Sep-2023
• ICS: 27.120.30 - Fissile materials and nuclear fuel technology
• Technical Committee: C26 - Nuclear Fuel Cycle
• Drafting Committee: C26.05 - Methods of Test

Relations

• Replaces: ASTM C1168-15 - Standard Practice for Preparation and Dissolution of Plutonium Materials for Analysis
• Effective Date: 01-Oct-2023
• Refers: ASTM C859-24 - Standard Terminology Relating to Nuclear Materials
• Effective Date: 01-Jan-2024
• Refers: ASTM C859-23 - Standard Terminology Relating to Nuclear Materials
• Effective Date: 15-Feb-2023
• Referred By: ASTM C1268-23 - Standard Test Method for Quantitative Determination of ²⁴¹Am in Plutonium by Gamma-Ray Spectrometry
• Effective Date: 01-Oct-2023
• Referred By: ASTM C1625-19 - Standard Test Method for Uranium and Plutonium Concentrations and Isotopic Abundances by Thermal Ionization Mass Spectrometry
• Effective Date: 01-Oct-2023
• Referred By: ASTM C1432-15 - Standard Test Method for Determination of Impurities in Plutonium: Acid Dissolution, Ion Exchange Matrix Separation, and Inductively Coupled Plasma-Atomic Emission Spectroscopic (ICP/AES) Analysis
• Effective Date: 01-Oct-2023
• Referred By: ASTM C1108-23 - Standard Test Method for Plutonium by Controlled-Potential Coulometry
• Effective Date: 01-Oct-2023
• Referred By: ASTM C1590-21 - Standard Practice for Alternate Actinide Calibration for Inductively Coupled Plasma-Mass Spectrometry
• Effective Date: 01-Oct-2023
• Referred By: ASTM C1307-21 - Standard Test Method for Plutonium Assay by Plutonium (III) Diode Array Spectrophotometry
• Effective Date: 01-Oct-2023
• Referred By: ASTM C1165-23 - Standard Test Method for Determining Plutonium by Controlled-Potential Coulometry in H<inf>2</inf>SO<inf>4</inf> at a Platinum Working Electrode
• Effective Date: 01-Oct-2023
• Referred By: ASTM C1637-21 - Standard Test Method for Determination of Impurities in Plutonium Materials-Acid Digestion and Inductively Coupled Plasma-Mass Spectroscopy (ICP-MS) Analysis
• Effective Date: 01-Oct-2023
• Referred By: ASTM C1816-16 - Standard Practice for The Ion Exchange Separation of Small Volume Samples Containing Uranium, Americium, and Plutonium Prior to Isotopic Abundance and Content Analysis
• Effective Date: 01-Oct-2023
• Referred By: ASTM C1221-10(2018) - Standard Test Method for Nondestructive Analysis of Special Nuclear Materials in Homogeneous Solutions by Gamma-Ray Spectrometry
• Effective Date: 01-Oct-2023
• Referred By: ASTM C1855-18 - Standard Test Method for Determination of Uranium and Plutonium Concentration in Aqueous Solutions Using Hybrid K-Edge Densitometry and X-Ray Fluorescence
• Effective Date: 01-Oct-2023
• Referred By: ASTM C1672-17 - Standard Test Method for Determination of Uranium or Plutonium Isotopic Composition or Concentration by the Total Evaporation Method Using a Thermal Ionization Mass Spectrometer
• Effective Date: 01-Oct-2023

Overview

ASTM C1168-23 is the internationally recognized standard practice for the preparation and dissolution of plutonium materials for analysis. Developed by ASTM International, this standard provides a comprehensive set of dissolution techniques tailored to the characterization and assay of plutonium metal, plutonium oxide, and uranium-plutonium mixed oxides - key materials in the nuclear fuel cycle. The procedures outlined are essential in ensuring accurate, reliable analysis of nuclear materials, which is critical for compliance with specifications such as ASTM C757 and C833 for reactor fuels.

Key Topics

• Dissolution Methods: A wide array of dissolution procedures is covered in the standard, including the use of mineral acids and fusion techniques. Procedures address the dissolution of standard forms of plutonium and uranium-plutonium materials, as well as unique materials such as alloys, compounds, and scrap metals.
• Sample Preparation: Emphasis is placed on removing surface oxides, selecting representative sample sizes, and using high-purity reagents and apparatus to prevent contamination.
• Analytical Precision: The standard specifies that aliquots of dissolved material are dispensed by mass for high-precision analyses, such as plutonium assay, and by volume for routine impurity analyses.
• Safety Considerations: Detailed precautions for the handling of strong acids and the use of specialized equipment such as inert atmosphere gloveboxes, fume hoods, and pressure-rated vessels are included to promote safe laboratory practices.
• Quality Control: The document references requirements for equipment calibration, reagent purity, and sample handling to ensure traceability and reproducibility of analytical results.

Applications

Compliance with ASTM C1168-23 ensures that laboratories and nuclear fuel manufacturers can:

• Assess Nuclear Fuel Materials: Determine the precise content of plutonium and uranium in metallic and oxide forms to meet regulatory and purchaser specifications for nuclear reactor fuels.
• Support Nuclear Quality Assurance: Produce accurate data required for the certification of fuel materials, supporting regulatory submissions and quality control programs.
• Characterize Diverse Plutonium Forms: Apply validated dissolution techniques to a range of materials, including plutonium metals, oxides, mixed oxides, and certain unique forms, after suitability testing.
• Enable Trace Impurity Analysis: Prepare samples in a way that allows for subsequent high-quality impurity and isotopic analyses, crucial for maintaining fuel purity and performance.
• Meet International and Industry Standards: Demonstrate conformity with internationally recognized practices, facilitating commerce and meeting audit requirements in the nuclear sector.

Related Standards

For a comprehensive approach to the analysis and processing of nuclear materials, the following ASTM and ISO standards should be consulted alongside ASTM C1168-23:

• ASTM C757: Specification for Nuclear-Grade Plutonium Dioxide Powder for Light Water Reactors
• ASTM C833: Specification for Sintered (Uranium-Plutonium) Dioxide Pellets for Light Water Reactors
• ASTM C859 / C1145: Terminology relating to nuclear materials and advanced ceramics
• ASTM C1210: Guide for Establishing a Measurement System Quality Control Program for Analytical Chemistry Laboratories Within Nuclear Industry
• ASTM E1154 / ISO 8655: Piston or plunger operated volumetric apparatus and operator qualification

Practical Value

Using ASTM C1168-23 enables nuclear laboratories and fuel manufacturers to adopt consistent, validated procedures for the challenging task of plutonium material analysis. Adherence to these methods supports safe handling, precise results, and international acceptance - all critical factors for success in the nuclear industry.

Keywords: ASTM C1168-23, plutonium dissolution, uranium-plutonium mixed oxide, nuclear fuel analysis, dissolution techniques, sample preparation, reactor fuel specifications, nuclear laboratory standards, nuclear materials analysis, quality control in nuclear chemistry.

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: C1168 − 23
Standard Practice for
Preparation and Dissolution of Plutonium Materials for
Analysis
This standard is issued under the fixed designation C1168; 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 the analyses must be of high precision, such as plutonium
assay; otherwise they are dispensed on a volume basis.
1.1 This practice is a compilation of dissolution techniques
1.2 Procedures in this practice are intended for the dissolu-
for plutonium materials that are applicable to the test methods
tion of plutonium metal, plutonium oxide, and uranium-
used for characterizing these materials. Dissolution treatments
plutonium mixed oxides. Aliquots of dissolved materials are
for the major plutonium materials assayed for plutonium or
analyzed using test methods, such as those developed by
analyzed for other components are listed. Aliquots of the
Subcommittee C26.05 on Methods of Test, to demonstrate
dissolved materials are dispensed on a mass basis when one of
compliance with applicable requirements. These may include
product specifications such as Specifications C757 and C833.
1.3 One or more of the procedures in this practice may be
This practice is under the jurisdiction of ASTM Committee C26 on Nuclear
applicable to unique plutonium materials, such as alloys,
Fuel Cycle and is the direct responsibility of Subcommittee C26.05 on Methods of
Test.
compounds, and scrap materials. The user must determine the
Current edition approved Oct. 1, 2023. Published October 2023. Originally
applicability of this practice to such materials.
approved in 1990. Last previous edition approved in 2015 as C1168 – 15. DOI:
10.1520/C1168-23. 1.4 The treatments, in order of presentation, are as follows:
Procedure Number Procedure Title Section
1 Dissolution of Plutonium Metal with Hydrochloric Acid at Room 9
Temperature
2 Dissolution of Plutonium Metal with Hydrochloric Acid and Heating 10
3 Dissolution of Plutonium Metal with Sulfuric Acid 11
4 Dissolution of Plutonium Oxide and Uranium-Plutonium Mixed 12
Oxide by the Sealed-Reflux Technique
5 Dissolution of Plutonium Oxide and Uranium-Plutonium Mixed 13
Oxides by Sodium Bisulfate Fusion
6 Dissolution of Uranium-Plutonium Mixed Oxides and Low-Fired 14
Plutonium Oxide in Beakers
7 Open-Vessel (with Reflux Condenser) Dissolution of Plutonium 15
Oxide Powder
8 Open-Vessel (with Reflux Condenser) Dissolution of Mixed Oxide 16
Powder
9 Closed-Vessel Hot Block Dissolution of Plutonium Oxide Powder 17
10 Open-Vessel (with Reflux Condenser) Dissolution of Mixed Oxide 18
Pellets
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1168 − 23
1.5 The values stated in SI units are to be regarded as 4. Summary of Dissolution Procedures
standard. The non-SI unit of molarity (M) is also to be regarded
4.1 Most plutonium-containing materials are dissolved with
as standard. Values in parentheses (non-SI units), where
various mineral acids and, except for plutonium metal, with
provided, are for information only and are not considered
applied heat. In some cases, dissolution-resistant materials are
standard.
dissolved in heated and sealed containers in which pressuriza-
1.6 This standard does not purport to address all of the
tion provides a higher temperature than is attained at ambient
safety concerns, if any, associated with its use. It is the
pressure.
responsibility of the user of this standard to establish appro-
4.2 The dissolved materials are quantitatively transferred to
priate safety, health, and environmental practices and deter-
a tared polyethylene dispensing bottle for subsequent deliveries
mine the applicability of regulatory limitations prior to use.
of weighed aliquots for high-precision analysis methods, such
1.7 This international standard was developed in accor-
as assays, or to a volumetric flask for deliveries of volume
dance with internationally recognized principles on standard-
aliquots for less precise analysis methods, such as impurity
ization established in the Decision on Principles for the
analyses. Dilute acids are used as rinses to effect quantitative
Development of International Standards, Guides and Recom-
transfers and as diluents in the polyethylene dispensing bottles
mendations issued by the World Trade Organization Technical
and volumetric flasks. The use of water for these purposes can,
Barriers to Trade (TBT) Committee.
in some cases, result in hydrolysis of plutonium to produce
polymers that, although soluble, are nonreactive in separation
2. Referenced Documents
treatments or in plutonium assay methods that have no
2.1 ASTM Standards:
pretreatments, such as fuming with acid.
C757 Specification for Nuclear-Grade Plutonium Dioxide
4.3 The procedures included in this practice are briefly
Powder for Light Water Reactors
described in 4.4 through 4.8. Other dissolution reagents are
C833 Specification for Sintered (Uranium-Plutonium) Diox-
possible, but are not addressed in this practice. When alternate
ide Pellets for Light Water Reactors
reagents are employed, the user shall verify their suitability for
C859 Terminology Relating to Nuclear Materials
the intended use.
C1145 Terminology of Advanced Ceramics
4.4 Plutonium metal is dissolved with hydrochloric acid
C1210 Guide for Establishing a Measurement System Qual-
(Section 9 or 10) or with sulfuric acid (Section 11).
ity Control Program for Analytical Chemistry Laborato-
ries Within Nuclear Industry
4.5 Plutonium oxide, calcined at about 1000 °C or lower, is
D1193 Specification for Reagent Water
dissolved with a mixture of hydrochloric, nitric, and hydroflu-
D7439 Test Method for Determination of Elements in Air-
oric acids using the sealed-reflux technique (Section 12) (1).
borne Particulate Matter by Inductively Coupled Plasma-
More refractory plutonium oxide is dissolved with a fusion
–Mass Spectrometry
using sodium bisuflate flux (Section 13) (2).
E1154 Specification for Piston or Plunger Operated Volu-
4.6 A mixture of nitric and hydrofluoric acid in beakers can
metric Apparatus and Operator Qualification
be used for low-fired (<650 °C) plutonium oxide (Section 14).
2.2 ISO Standards:
Open-vessel dissolution using nitric and hydrofluoric acids can
ISO 8655 Piston-Operated Volumetric Instruments (6 parts)
be used for low-fired plutonium oxide (Section 15) or mixed
oxide (Section 16). Closed-vessel hot block dissolution can
3. Terminology
also be used for low-fired plutonium oxide (Section 17).
Plutonium oxide fired at temperatures above 650 °C may also
3.1 Definitions—Except as otherwise defined herein, defini-
be dissolved using one of the methods described in Sections 14
tions of terms are as given in Terminology C859.
through 17 when complete dissolution can be demonstrated.
3.2 Definitions of Terms Specific to This Standard:
4.7 Uranium-plutonium mixed oxide is dissolved in any of
3.2.1 calcination, n—(calcine, v)—firing or heating of a
the following ways: by the sealed-reflux technique using a
granular or particulate solid at less than fusion temperature, but
mixture of hydrochloric, nitric, and hydrofluoric acids (Section
sufficient to remove most of its chemically combined volatile
12), by sodium bisulfate fusion (Section 13), by a heated
matter and otherwise to develop the desired properties for use.
mixture of nitric and hydrofluoric acids in a beaker (Section
C1145
14), or by open-vessel dissolution using nitric and hydrofluoric
3.2.2 reagent blank, n—solution containing all reagents
acids (Section 16).
used in sample preparation, in the same quantities used for
4.8 Mixed oxide pellets are dissolved using open-vessel
preparation of blank and sample solutions. D7439
dissolution with nitric and hydrofluoric acids (Section 18).
4.9 Combinations of these dissolution techniques described
For referenced ASTM standards, visit the ASTM website, www.astm.org, or in the preceding paragraphs are sometimes used on difficult-
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
to-dissolve samples.
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
Available from International Organization for Standardization (ISO), ISO
Central Secretariat, Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva, The boldface numbers in parentheses refer to a list of references at the end of
Switzerland, http://www.iso.org. this practice.
C1168 − 23
4.10 Quantitative transfers of samples and subsequent solu- 7.1 Purity of Reagents—All reagents used should be of the
tion are required. Whenever a loss is incurred or even highest purity available. Other grades may be used if they are
suspected, the sample is rejected. Solutions of dissolved determined not to affect the final result.
samples are inspected for undissolved particles; if particles are
7.2 Purity of Water—Unless otherwise indicated, references
present, further treatment is necessary to attain complete
to water shall be understood to mean reagent water, as defined
solubility. When analyzing the dissolved sample for trace
by Type I of Specification D1193.
impurities, caution should be exercised so the dissolution
8. Precautions
process does not cause the impurity to be lost or does not
significantly increase the level of impurity being determined.
8.1 Strong acids are used by these dissolution procedures.
Safety glasses and gloves must be worn when handling these
5. Significance and Use
solutions. Extreme care should be exercised in using hydroflu-
5.1 Plutonium and uranium mixtures are used as nuclear
oric acid and other hot concentrated acids. Acid solutions are
reactor fuels. For use as a nuclear reactor fuel, the material
evaporated by these dissolution procedures. These operations
must meet certain criteria for combined uranium and plutonium
must be conducted in a fume hood.
content, effective fissile content, and impurity content as
8.2 Hydrofluoric acid is a highly corrosive and toxic acid
described in Specifications C757 and C833. After dissolution
that can severely burn skin, eyes, and mucous membranes.
using one of the procedures described in this practice, the
Hydrofluoric acid differs from other acids because the fluoride
material is assayed for plutonium and uranium to determine if
ion readily penetrates the skin, causing destruction of deep
the content is correct as specified by the purchaser.
tissue layers. Unlike other acids that are rapidly neutralized,
5.2 Unique plutonium materials, such as alloys, compounds,
hydrofluoric acid reactions with tissue may continue for days if
and scrap metals, are typically dissolved with various acid
left untreated. Familiarization and compliance with the Safety
mixtures or by fusion with various fluxes. Many plutonium
Data Sheet is essential.
salts are soluble in hydrochloric acid. One or more of the
8.3 Extreme care is required when using procedures that
procedures included in this practice may be effective for some
involve closed vessels, pressurization, or both (Sections 12 and
of these materials; however their applicability to a particular
17). Potential explosions or rupturing of vessels could injure
plutonium material shall be verified by the user.
personnel or breach glovebox containment, or both. Appropri-
6. Apparatus ate controls are required to prevent pressure or temperature
from exceeding prescribed by safety limits.
6.1 Ordinary laboratory apparatus are not listed, but are
assumed to be present.
9. Procedure 1 – Dissolution of Plutonium Metal with
6.2 The following items are used by most or all procedures Hydrochloric Acid at Room Temperature
listed herein. Apparatus specific to one, or a few, procedures
9.1 Apparatus:
are listed under the specific procedures where they are used.
9.1.1 Hot Plate, thermostatically controlled, capable of
6.2.1 Balances, for weighing samples and solutions. A
maintaining a surface temperature of up to at least 200 °C.
balance with a sensitivity of 0.1 mg is necessary; however, a
NOTE 2—The surface temperature of a hot plate can vary considerably
balance with 0.01 mg sensitivity is more desirable. A calibrated
with position on hot plates with large surface areas. It is therefore
balance must be used.
recommended that the performance of the hot plate be characterized
6.2.2 Beakers and Erlenmeyer Flasks—Generally, borosili-
before use.
cate glass is recommended; however, the analyst should be sure
9.1.2 Centrifuge Tube, optional, to receive weighed sample
that safety and sample contamination from the container are
if beaker is not used.
considered when choosing appropriate containers. For
9.1.3 Watch glasses.
example, when hydrofluoric acid is used, the use of borosilicate
9.1.4 Infrared lamp.
glass may be avoided due to etching.
9.2 Reagents:
6.2.3 Volumetric flasks or polyethylene dispensing bottles,
9.2.1 Hydrochloric Acid, concentrated (sp gr 1.18), 12 M.
for collecting the final solution from which aliquots are
9.2.2 Hydrochloric Acid, 6 M—Add 500 mL of 12 M HCl to
dispensed.
<500 mL of water and dilute to 1 L with water.
6.2.4 File or brush, for cleaning plutonium metal surfaces
9.2.3 Hydrochloric Acid, 1 M—Add 83 mL of 12 M HCl to
(used in Sections 9 through 11).
<900 mL of water and dilute to 1 L with water.
6.2.5 Inert Atmosphere Glove-Box System—capability of
9.2.4 Hydrofluoric Acid, concentrated (sp gr 1.17), 28 M.
maintaining H O content of less than 10 μL ⁄L and O content
2 2
9.2.5 Hydrofluoric Acid, 1.3 M—Transfer 4.8 mL of 28 M
less than 2 % is preferred.
HF, using a plastic pipet, to a 100 mL plastic graduated
6.2.6 Piston-Operated Volumetric Pipettors, complying
cylinder containing <90 mL of water and dilute to 100 mL with
with the requirements of Specification E1154, applicable
water. Transfer to a plastic bottle for storage.
portions of ISO 8655 (six parts), or both.
9.2.6 Nitric Acid, concentrated (sp gr 1.42), 16 M.
7. Reagents
9.3 Procedure:
NOTE 1—Reagents used in specific procedures are listed within the
9.3.1 Remove surface oxide, if present, from the bulk
procedure or procedures where they are used. The following information
applies to all reagents. sample before cutting into portions. Removal of surface oxide
C1168 − 23
may be performed by filing or brushing the plutonium metal, or 10.4.1 Remove surface oxide, if present, from the bulk
by using other mechanical or chemical means. sample before cutting into portions. Removal of surface oxide
may be performed by filing or brushing the plutonium metal, or
NOTE 3—Plutonium metal reacts with air and moisture to form PuO .
by using other mechanical or chemical means.
An inert-atmosphere glovebox system can be utilized for mechanical
removal of surface oxide, but is not recommended for removal by
NOTE 5—Plutonium metal reacts with air and moisture to form PuO .
chemical means. Use of an inert-atmosphere glovebox system is recom-
An inert-atmosphere glovebox system can be utilized for mechanical
mended when preparing standards or tracers.
removal of surface oxide, but is not recommended for removal by
chemical means. Use of an inert-atmosphere glovebox system is recom-
9.3.2 Weigh a representative sample size, considering the
mended when preparing standards or tracers.
required uncertainty and the analysis method to be used.
Normal sample size is 50 mg to 700 mg, but this may vary. A 10.4.2 Weigh a representative sample size, considering the
certified sample mass, if known, may be used in lieu of required uncertainty and the analysis method to be used. A
weighing. certified sample mass, if known, may be used in lieu of
9.3.3 Transfer the weighed sample to a beaker or centrifuge weighing.
tube and cover with a watch glass. 10.4.3 Transfer the weighed sample to a beaker or Erlen-
9.3.4 Add 6 M HCl dropwise, or in small portions, through meyer flask, add just enough 0.1 M HCl to cover the metal,
then slowly add 7 mL to 8 mL of 12 M HCl and cover with a
the spout of the beaker or centrifuge tube until the sample
dissolves completely. watch glass.
10.4.4 Allow the metal to dissolve for 10 min to 15 min at
9.3.5 Inspect the solution for suspended particles or depos-
ited solid and, if present, warm the solution (using, for room temperature.
10.4.5 Inspect the solution for suspended particles or depos-
example, an infrared lamp).
9.3.6 If solid still is present, add 0.5 mL 16 M HNO and ited solid and, if present, add an additional 2 mL of 12 M HCl
and heat to boiling for 2 h.
three drops 1.3 M HF, and heat until dissolution is complete.
9.3.7 Quantitatively transfer the solution using at least four 10.4.6 If solid is still present, add an additional 2 mL of
12 M HCl and 2 drops of 1M HF, and heat for an additional 2 h.
rinses of the watch glass and beaker or centrifuge tube with
1 M HCl. Transfer to a volumetric flask and bring to volume 10.4.7 Repeat step 10.4.6 as necessary until dissolution is
complete.
using 1 M HCl. Alternatively, for high-precision analyses,
transfer to a previously tared polyethylene dispensing bottle, 10.4.8 Quantitatively transfer the solution using at least four
rinses of the watch glass and beaker or centrifuge tube with
weigh the bottle with the solution, and calculate the mass
difference to determine final volume. 1 M HCl. Transfer to a volumetric flask and bring to volume
using 1 M HCl. Alternatively, for high-precision analyses,
9.3.8 Mix the solution, equilibrate to room temperature, and
dispense aliquots for analysis. transfer to a previously tared polyethylene dispensing bottle,
weigh the bottle with the solution, and calculate the mass
difference to determine final volume.
10. Procedure 2 – Dissolution of Plutonium Metal with
10.4.9 Mix the solution, equilibrate to room temperature,
Hydrochloric Acid and Heating
and dispense aliquots for analysis.
10.1 This procedure is for Pu metal pieces of approximately
0.5 g mass which may be conditioned under an inert atmo-
11. Procedure 3 – Dissolution of Plutonium Metal with
sphere glovebox system.
Sulfuric Acid
10.2 Apparatus:
11.1 Apparatus:
10.2.1 Hot Plate: thermostatically controlled, capable of
11.1.1 Infrared lamp.
maintaining a surface temperature of up to at least 200 °C.
11.1.2 Watch glasses.
11.1.3 Magnetic stirrer with TFE-fluorocarbon stir bar.
NOTE 4—The surface temperature of a hot plate can vary considerably
with position on hot plates with large surface areas. It is therefore
11.2 Reagents:
recommended that the performance of the hot plate be characterized
11.2.1 Sulfuric Acid, concentrated (sp gr 1.84), 18 M.
before use.
11.2.2 Sulfuric Acid, 0.5 M—Cautiously add 28 mL of 18 M
10.2.2 Watch glasses.
H SO to water and dilute to 1 L with water.
2 4
10.3 Reagents:
11.3 Procedure:
10.3.1 Hydrochloric Acid, concentrated (sp gr 1.18), 12 M.
11.3.1 Remove surface oxide, if present, from the bulk
10.3.2 Hydrochloric Acid, 1 M—Add 83 mL of 12 M HCl to
sample before cutting into portions. Removal of surface oxide
<900 mL of water and dilute to 1 L with water.
may be performed by filing or brushing the plutonium metal, or
10.3.3 Hydrochloric Acid, 0.1 M—Add 8.3 mL of 12 M HCl
by using other mechanical or chemical means.
to <900 mL of water and dilute to 1 L with water.
NOTE 6—Plutonium metal reacts with air and moisture to form PuO .
10.3.4 Hydrofluoric Acid, concentrated (sp gr 1.17), 28 M. 2
An inert-atmosphere glovebox system can be utilized for mechanical
10.3.5 Hydrofluoric Acid, 1 M—Transfer 3.6 mL of 28 M
removal of surface oxide, but is not recommended for removal by
HF, using a plastic pipet, to a 100 mL plastic graduated
chemical means. Use of an inert-atmosphere glovebox system is recom-
cylinder containing <90 mL of water and dilute to 100 mL with
mended when preparing standards or tracers.
water. Transfer to a plastic bottle for storage.
11.3.2 Weigh a representative sample size, considering the
10.4 Procedure: required uncertainty and the analysis method to be used.
C1168 − 23
Normal sample size is 50 mg to 700 mg, but this may vary. A
certified sample mass, if known, may be used in lieu of
weighing.
11.3.3 Transfer the weighed sample to a beaker or Erlen-
meyer flask and cover with a watch glass.
11.3.4 Carefully place a TFE-fluorocarbon stirring bar in the
beaker or flask along with 30 mL to 40 mL of 0.5 M H SO , put
2 4
the dissolution container on a magnetic stirrer, and mix the
solution until the sample is dissolved.
11.3.5 Inspect the solution for suspended particles or depos-
ited solid and, if present, warm the solution (using, for
example, an infrared lamp).
11.3.6 Quantitatively transfer the solution using at least four
rinses of the watch glass and beaker or Erlenmeyer flask with
0.5 M H SO . Transfer to a volumetric flask and bring to
2 4
volume using 0.5 M H SO . Alternatively, for high-precision
2 4
analyses, transfer to a previously tared polyethylene dispensing
bottle, weigh the bottle with the solution, and calculate the
mass difference to determine final volume.
11.3.7 Mix the solution, equilibrate to room temperature,
and dispense aliquots for analysis.
12. Procedure 4 – Dissolution of Plutonium Oxide and
Uranium-Plutonium Mixed Oxide by the Sealed-Reflux
FIG. 2 Heating Block
Technique
NOTE 7—The procedure described in this section is based on Ref. (1)
and should be considered an example. A different apparatus may be used
and is intended for sample sizes of approximately 0.5 g. A modification of
if it has been shown to meet the performance requirements of this section.
the procedure and apparatus for samples of up to 100 g is described in Ref.
(3). The procedure has been used on mixed oxide pellets with minor 12.1.2 Stopper—A stopper which will not react with the
modifications; see Note 10.
dissolution matrix must be used. A solid stopper inserted in a
hollow, polyethylene stopper liner has been found to be
12.1 Apparatus:
satisfactory. Certain fluorinated elastomers, designated as
12.1.1 Sealed-Reflux Dissolution Apparatus—The example
FKMs, have also been found to be satisfactory.
apparatus is shown in Fig. 1 and Fig. 2 and is further described
12.1.3 Spring clamp that will hold the tube snugly to the
in Ref (1).
reflux condenser, but will release pressure at a level well below
NOTE 8—The apparatus shown in Fig. 1 and Fig. 2 is based on Ref. (1)
the failure point of the tube. (Warning—The spring clamp
must be selected to ensure that the tube releases pressure well
below the point that would cause the tube to fail physically. A
suggested value is 827 kPa (120 psi) but should be verified
prior to use. Only one clamp should be used so as not to
compromise this safety feature.)
12.1.4 Weighing pan.
12.2 Reagents:
12.2.1 Hydrochloric Acid, concentrated (sp gr 1.18), 12 M.
12.2.2 Hydrochloric Acid, 1 M—Add 83 mL of 12 M HCl to
<900 mL of water and dilute to 1 L with water.
12.2.3 Hydrofluoric Acid, concentrated (sp gr 1.17), 28 M.
12.2.4 Hydrofluoric Acid, 1.3 M—Transfer 4.8 mL of 28 M
HF, using a plastic pipet, to a 100 mL plastic graduated
cylinder containing <90 mL of water and dilute to 100 mL with
water. Transfer to a plastic bottle for storage.
12.2.5 Nitric Acid, concentrated (sp gr 1.42), 16 M.
12.3 Procedure:
12.3.1 Tare a weighing pan or other type of container.
12.3.2 Transfer sample to the tared pan or other container
until the desired mass of sample is obtained, usually 0.5 g.
Weigh to at least 0.1 mg sensitivity.
12.3.3 Quantitatively transfer the sample from the
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: C1168 − 15 C1168 − 23
Standard Practice for
Preparation and Dissolution of Plutonium Materials for
Analysis
This standard is issued under the fixed designation C1168; 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
1.1 This practice is a compilation of dissolution techniques for plutonium materials that are applicable to the test methods used
for characterizing these materials. Dissolution treatments for the major plutonium materials assayed for plutonium or analyzed for
other components are listed. Aliquots of the dissolved samplesmaterials are dispensed on a weightmass basis when one of the
analyses must be highly reliable, of high precision, such as plutonium assay; otherwise they are dispensed on a volume basis.
1.2 Procedures in this practice are intended for the dissolution of plutonium metal, plutonium oxide, and uranium-plutonium
mixed oxides. Aliquots of dissolved samplesmaterials are analyzed using test methods, such as those developed by Subcommittee
C26.05 on Methods of Test, to demonstrate compliance with applicable requirements. These may include product specifications
such as Specifications C757 and C833.
1.3 One or more of the procedures in this practice may be applicable to unique plutonium materials, such as alloys, compounds,
and scrap materials. The user must determine the applicability of this practice to such materials.
1.4 The treatments, in order of presentation, are as follows:
Procedure Number Procedure Title Section
1 Dissolution of Plutonium Metal with Hydrochloric Acid at Room 9
Temperature
2 Dissolution of Plutonium Metal with Hydrochloric Acid and Heating 10
3 Dissolution of Plutonium Metal with Sulfuric Acid 11
4 Dissolution of Plutonium Oxide and Uranium-Plutonium Mixed 12
Oxide by the Sealed-Reflux Technique
5 Dissolution of Plutonium Oxide and Uranium-Plutonium Mixed 13
Oxides by Sodium Bisulfate Fusion
6 Dissolution of Uranium-Plutonium Mixed Oxides and Low-Fired 14
Plutonium Oxide in Beakers
7 Open-Vessel (with Reflux Condenser) Dissolution of Plutonium 15
Oxide Powder
8 Open-Vessel (with Reflux Condenser) Dissolution of Mixed Oxide 16
Powder
9 Closed-Vessel Hot Block Dissolution of Plutonium Oxide Powder 17
10 Open-Vessel (with Reflux Condenser) Dissolution of Mixed Oxide 18
Pellets
This practice is under the jurisdiction of ASTM Committee C26 on Nuclear Fuel Cycle and is the direct responsibility of Subcommittee C26.05 on Methods of Test.
Current edition approved Sept. 1, 2015Oct. 1, 2023. Published October 2015October 2023. Originally approved in 1990. Last previous edition approved in 20082015 as
C1168 – 08.C1168 – 15. DOI: 10.1520/C1168-15.10.1520/C1168-23.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1168 − 23
1.5 The values stated in SI units are to be regarded as standard. The non-SI unit of molarity (M) is also to be regarded as standard.
Values in parentheses (non-SI units), where provided, are for information only and are not considered standard.
1.6 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 healthsafety, health, and environmental practices and determine
the applicability of regulatory limitations prior to use.
1.7 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.
2. Referenced Documents
2.1 ASTM Standards:
C757 Specification for Nuclear-Grade Plutonium Dioxide Powder for Light Water Reactors
C833 Specification for Sintered (Uranium-Plutonium) Dioxide Pellets for Light Water Reactors
C859 Terminology Relating to Nuclear Materials
C1145 Terminology of Advanced Ceramics
C1210 Guide for Establishing a Measurement System Quality Control Program for Analytical Chemistry Laboratories Within
Nuclear Industry
D1193 Specification for Reagent Water
D7439 Test Method for Determination of Elements in Airborne Particulate Matter by Inductively Coupled Plasma–Mass
Spectrometry
E1154 Specification for Piston or Plunger Operated Volumetric Apparatus and Operator Qualification
2.2 ISO Standards:
ISO 8655 Piston-Operated Volumetric Instruments (6 parts)
3. Terminology
3.1 Definitions—Except as otherwise defined herein, definitions of terms are as given in Terminology C859.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 calcination, n—(calcine,v)—firing or heating of a granular or particulate solid at less than fusion temperature, but sufficient
to remove most of its chemically combined volatile matter and otherwise to develop the desired properties for use. C1145
3.2.2 reagent blank, n—solution containing all reagents used in sample preparation, in the same quantities used for preparation
of blank and sample solutions. D7439
4. Summary of Dissolution Procedures
4.1 Most plutonium-containing samplesmaterials are dissolved with various mineral acids and, except for plutonium metal, with
applied heat. In some cases, dissolution-resistant materials are dissolved in heated and sealed containers in which pressurization
provides a higher temperature than is attained at ambient pressure.
4.2 The dissolved materials are quantitatively transferred to a tared polyethylene dispensing bottle for subsequent deliveries of
weighed aliquots for high-precision analysis methods, such as assays, or to a volumetric flask for deliveries of volume aliquots for
less precise analysis methods, such as impurity analyses. Dilute acids are used as rinses to effect quantitative transfers and as
diluents in the polyethylene dispensing bottles and volumetric flasks. The use of water for these purposes can, in some cases, result
in hydrolysis of plutonium to produce polymers that, although soluble, are nonreactive in separation treatments or in plutonium
assay methods that have no pretreatments, such as fuming with acid.
4.3 The procedures included in this practice are briefly described in 4.4 through 4.8. Other dissolution reagents are possible, but
are not addressed in this practice. When alternate reagents are employed, the user shall verify their suitability for the intended use.
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 the ASTM website.
Available from International Organization for Standardization (ISO), ISO Central Secretariat, Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva, Switzerland,
http://www.iso.org.
C1168 − 23
4.4 Plutonium metal is dissolved with hydrochloric acid (Section 9 or 10) or with sulfuric acid (Section 11).
4.5 Plutonium oxide, calcined at about 1000°C1000 °C or lower, is dissolved with a mixture of hydrochloric, nitric, and
hydrofluoric acids using the sealed-reflux techniquestechnique (Section 12) (1). More refractory plutonium oxide is dissolved with
a fusion using sodium bisuflate flux (Section 13) (2).
4.6 A mixture of nitric and hydrofluoric acid in beakers can be used for low-fired (<650°C)(<650 °C) plutonium oxide (Section
14). Open-vessel dissolution using nitric and hydrofluoric acids can be used for low-fired plutonium oxide (Section 15) or mixed
oxide (Section 16). Closed-vessel hot block dissolution can also be used for low-fired plutonium oxide (Section 17). Plutonium
oxide fired at temperatures above 650°C650 °C may also be dissolved using one of the methods described in Sections 14 through
17 when complete dissolution can be demonstrated.
4.7 Uranium-plutonium mixed oxide is dissolved in any of the following ways: by the sealed-reflux technique using a mixture of
hydrochloric, nitric, and hydrofluoric acids (Section 12), by sodium bisulfate fusion (Section 13), by a heated mixture of nitric and
hydrofluoric acids in a beaker (Section 14), or by open-vessel dissolution using nitric and hydrofluoric acids (Section 16).
4.8 Mixed oxide pellets are dissolved using open-vessel dissolution with nitric and hydrofluoric acids (Section 18).
4.9 Combinations of these dissolution techniques described in the preceding paragraphs are sometimes used on difficult-to-
dissolve samples.
4.10 Quantitative transfers of samples and subsequent solution are required. Whenever a loss is incurred or even suspected, the
sample is rejected. Solutions of dissolved samples are inspected for undissolved particles; if particles are present, further treatment
is necessary to attain complete solubility. When analyzing the dissolved sample for trace impurities, caution should be exercised
so the dissolution process does not cause the impurity to be lost or does not significantly increase the level of impurity being
determined.
5. Significance and Use
5.1 Plutonium and uranium mixtures are used as nuclear reactor fuels. For use as a nuclear reactor fuel, the material must meet
certain criteria for combined uranium and plutonium content, effective fissile content, and impurity content as described in
Specifications C757 and C833. After dissolution using one of the procedures described in this practice, the material is assayed for
plutonium and uranium to determine if the content is correct as specified by the purchaser.
5.2 Unique plutonium materials, such as alloys, compounds, and scrap metals, are typically dissolved with various acid mixtures
or by fusion with various fluxes. Many plutonium salts are soluble in hydrochloric acid. One or more of the procedures included
in this practice may be effective for some of these materials; however their applicability to a particular plutonium material shall
be verified by the user.
6. Apparatus
6.1 Ordinary laboratory apparatus are not listed, but are assumed to be present.
6.2 The following items are used by most or all procedures listed herein. Apparatus specific to one, or a few, procedures are listed
under the specific procedures where they are used.
6.2.1 Balances, for weighing samples and solutions. A balance with a sensitivity of 0.1 mg is necessary; however, a balance with
0.01 mg sensitivity is more desirable. A calibrated balance must be used.
6.2.2 Beakers and Erlenmeyer Flasks—Generally, borosilicate glass is recommended; however, the analyst should be sure that
safety and sample contamination from the container are considered when choosing appropriate containers. For example, when
hydrofluoric acid is used, the use of borosilicate glass may be avoided due to etching.
The boldface numbers in parentheses refer to a list of references at the end of this practice.
C1168 − 23
6.2.3 Volumetric flasks or polyethylene dispensing bottles, for collecting the final solution from which aliquots are dispensed.
6.2.4 File or brush, for cleaning plutonium metal surfaces (used in Sections 9 through 11).
6.2.5 Inert Atmosphere Glove-Box System—capability of maintaining less than 10 ppm of H O and 2 % of content of less than
10 μL ⁄L and O content less than 2 % is preferred.
6.2.6 Piston-Operated Volumetric Pipettors, complying with the requirements of Specification E1154, applicable portions of ISO
8655 (six parts), or both.
7. Reagents
NOTE 1—Reagents used in specific procedures are listed within the procedure or procedures where they are used. The following information applies to
all reagents.
7.1 Purity of Reagents—All reagents used should be of the highest purity available. Other grades may be used if they are
determined not to affect the final result.
7.2 Purity of Water—Unless otherwise indicated, references to water shall be understood to mean reagent water, as defined by Type
I of Specification D1193.
8. Precautions
8.1 Strong acids are used by these dissolution procedures. Safety glasses and gloves must be worn when handling these solutions.
Extreme care should be exercised in using hydrofluoric acid and other hot concentrated acids. Acid solutions are evaporated by
these dissolution procedures. These operations must be conducted in a fume hood.
8.2 Hydrofluoric acid is a highly corrosive and toxic acid that can severely burn skin, eyes, and mucous membranes. Hydrofluoric
acid differs from other acids because the fluoride ion readily penetrates the skin, causing destruction of deep tissue layers. Unlike
other acids that are rapidly neutralized, hydrofluoric acid reactions with tissue may continue for days if left untreated.
Familiarization and compliance with the Safety Data Sheet is essential.
8.3 Extreme care is required when using procedures that involve closed vessels, pressurization, or both (Sections 12 and 17).
Potential explosions or rupturing of vessels could injure personnel or breach glovebox containment, or both. Appropriate controls
are required to prevent pressure or temperature from exceeding prescribed by safety limits.
9. Procedure 1 – Dissolution of Plutonium Metal with Hydrochloric Acid at Room Temperature
9.1 Apparatus:
9.1.1 Hot Plate, thermostatically controlled, capable of maintaining a surface temperature of up to at least 200°C.200 °C.
NOTE 2—The surface temperature of a hot plate can vary considerably with position on hot plates with large surface areas. It is therefore recommended
that the performance of the hot plate be characterized before use.
9.1.2 Centrifuge Tube, optional, to receive weighed sample if beaker is not used.
9.1.3 Watch glasses.
9.1.4 Infrared lamp.
9.2 Reagents:
9.2.1 Hydrochloric Acid, concentrated (sp gr 1.18), 12 M.
9.2.2 Hydrochloric Acid, 6 M—Add 500 mL of 12 M HCl to <500 mL of water and dilute to 1 L with water.
C1168 − 23
9.2.3 Hydrochloric Acid, 1 M—Add 83 mL of 12 M HCl to <900 mL of water and dilute to 1 L with water.
9.2.4 Hydrofluoric Acid, concentrated (sp gr 1.17), 28 M.
9.2.5 Hydrofluoric Acid, 1.3 M—Transfer 4.8 mL of 28 M HF, using a plastic pipet, to a 100-mL100 mL plastic graduated cylinder
containing <90 mL of water and dilute to 100 mL with water. Transfer to a plastic bottle for storage.
9.2.6 Nitric Acid, concentrated (sp gr 1.42), 16 M.
9.3 Procedure:
9.3.1 Remove surface oxide, if present, from the bulk sample before cutting into portions. Removal of surface oxide may be
performed by filing or brushing the plutonium metal, or by using other mechanical or chemical means.
NOTE 3—Plutonium metal reacts with air and moisture to form PuO . An inert-atmosphere glovebox system can be utilized for mechanical removal of
surface oxide, but is not recommended for removal by chemical means. Use of an inert-atmosphere glovebox system is recommended when preparing
standards or tracers.
9.3.2 Weigh a representative sample size, considering the required uncertainty and the analysis method to be used. Normal sample
size is 50 to 700 mg, 50 mg to 700 mg, but this may vary. A certified sample mass, if known, may be used in lieu of weighing.
9.3.3 Transfer the weighed sample to a beaker or centrifuge tube and cover with a watch glass.
9.3.4 Add 6 M HCl dropwise, or in small portions, through the spout of the beaker or centrifuge tube until the sample dissolves
completely.
9.3.5 Inspect the solution for suspended particles or deposited solid and, if present, warm the solution (using, for example, an
infrared lamp).
9.3.6 If solid still is present, add 0.5 mL 16 M HNO and three drops 1.3 M HF, and heat until dissolution is complete.
9.3.7 Quantitatively transfer the solution using at least four rinses of the watch glass and beaker or centrifuge tube with 1 1 M HCl.
Transfer to a volumetric flask and bring to volume using 1 1 M HCl. Alternatively, for high-precision analyses, transfer to a
previously tared polyethylene dispensing bottle, weigh the bottle with the solution, and calculate the weightmass difference to
determine final volume.
9.3.8 Mix the solution, equilibrate to room temperature, and dispense aliquots for analysis.
10. Procedure 2 – Dissolution of Plutonium Metal with Hydrochloric Acid and Heating
10.1 This procedure is for Pu metal pieces of approximately 0.5 g mass which may be conditioned under an inert atmosphere
glovebox system.
10.2 Apparatus:
10.2.1 Hot Plate: thermostatically controlled, capable of maintaining a surface temperature of up to at least 200°C.200 °C.
NOTE 4—The surface temperature of a hot plate can vary considerably with position on hot plates with large surface areas. It is therefore recommended
that the performance of the hot plate be characterized before use.
10.2.2 Watch glasses.
10.3 Reagents:
10.3.1 Hydrochloric Acid, concentrated (sp gr 1.18), 12 M.
C1168 − 23
10.3.2 Hydrochloric Acid, 1 M—Add 83 mL of 12 M HCl to <900 mL of water and dilute to 1 L with water.
10.3.3 Hydrochloric Acid, 0.1 M—Add 8.3 mL of 12 M HCl to <900 mL of water and dilute to 1 L with water.
10.3.4 Hydrofluoric Acid, concentrated (sp gr 1.17), 28 M.
10.3.5 Hydrofluoric Acid, 1 M—Transfer 3.6 mL of 28 M HF, using a plastic pipet, to a 100-mL100 mL plastic graduated cylinder
containing <90 mL of water and dilute to 100 mL with water. Transfer to a plastic bottle for storage.
10.4 Procedure:
10.4.1 Remove surface oxide, if present, from the bulk sample before cutting into portions. Removal of surface oxide may be
performed by filing or brushing the plutonium metal, or by using other mechanical or chemical means.
NOTE 5—Plutonium metal reacts with air and moisture to form PuO . An inert-atmosphere glovebox system can be utilized for mechanical removal of
surface oxide, but is not recommended for removal by chemical means. Use of an inert-atmosphere glovebox system is recommended when preparing
standards or tracers.
10.4.2 Weigh a representative sample size, considering the required uncertainty and the analysis method to be used. A certified
sample mass, if known, may be used in lieu of weighing.
10.4.3 Transfer the weighed sample to a beaker or Erlenmeyer flask, add just enough 0.1 M HCl to cover the metal, then slowly
add 77 mL to 8 mL of 12 M HCl and cover with a watch glass.
10.4.4 Allow the metal to dissolve for 1010 min to 15 min at room temperature.
10.4.5 Inspect the solution for suspended particles or deposited solid and, if present, add an additional 2 mL of 12 M HCl and heat
to boiling for 2 h.
10.4.6 If solid is still present, add an additional 2 mL of 12 12 M HCl and 2 drops of 1M HF, and heat for an additional 2 h.2 h.
10.4.7 Repeat step 10.4.6 as necessary until dissolution is complete.
10.4.8 Quantitatively transfer the solution using at least four rinses of the watch glass and beaker or centrifuge tube with 1 1 M
HCl. Transfer to a volumetric flask and bring to volume using 1 1 M HCl. Alternatively, for high-precision analyses, transfer to
a previously tared polyethylene dispensing bottle, weigh the bottle with the solution, and calculate the weightmass difference to
determine final volume.
10.4.9 Mix the solution, equilibrate to room temperature, and dispense aliquots for analysis.
11. Procedure 3 – Dissolution of Plutonium Metal with Sulfuric Acid
11.1 Apparatus:
11.1.1 Infrared lamp.
11.1.2 Watch glasses.
11.1.3 Magnetic stirrer with TFE-fluorocarbon stir bar.
11.2 Reagents:
11.2.1 Sulfuric Acid, concentrated (sp gr 1.84), 18 M.
11.2.2 Sulfuric Acid, 0.5 M—Cautiously add 28 mL of 18 M H SO to water and dilute to 1 L with water.
2 4
C1168 − 23
11.3 Procedure:
11.3.1 Remove surface oxide, if present, from the bulk sample before cutting into portions. Removal of surface oxide may be
performed by filing or brushing the plutonium metal, or by using other mechanical or chemical means.
NOTE 6—Plutonium metal reacts with air and moisture to form PuO . An inert-atmosphere glovebox system can be utilized for mechanical removal of
surface oxide, but is not recommended for removal by chemical means. Use of an inert-atmosphere glovebox system is recommended when preparing
standards or tracers.
11.3.2 Weigh a representative sample size, considering the required uncertainty and the analysis method to be used. Normal
sample size is 5050 mg to 700 mg, but this may vary. A certified sample mass, if known, may be used in lieu of weighing.
11.3.3 Transfer the weighed sample to a beaker or Erlenmeyer flask and cover with a watch glass.
11.3.4 Carefully place a TFE-fluorocarbon stirring bar in the beaker or flask along with 3030 mL to 40 mL of 0.5 M H SO , put
2 4
the dissolution container on a magnetic stirrer, and mix the solution until the sample is dissolved.
11.3.5 Inspect the solution for suspended particles or deposited solid and, if present, warm the solution (using, for example, an
infrared lamp).
11.3.6 Quantitatively transfer the solution using at least four rinses of the watch glass and beaker or Erlenmeyer flask with 0.5 M
H SO . Transfer to a volumetric flask and bring to volume using 0.5 M H SO . Alternatively, for high-precision analyses, transfer
2 4 2 4
to a previously tared polyethylene dispensing bottle, weigh the bottle with the solution, and calculate the weightmass difference
to determine final volume.
11.3.7 Mix the solution, equilibrate to room temperature, and dispense aliquots for analysis.
12. Procedure 4 – Dissolution of Plutonium Oxide and Uranium-Plutonium Mixed Oxide by the Sealed-Reflux
Technique
NOTE 7—The procedure described in this section is based on Ref. (1) and is intended for sample sizes of approximately 0.5 g. A modification of the
procedure and apparatus for samples of up to 100 g is described in Ref. (3). The procedure has been used on mixed oxide pellets with minor modifications;
see Note 10.
12.1 Apparatus:
12.1.1 Sealed-Reflux Dissolution Apparatus—The example apparatus is shown in Fig. 1 and Fig. 2 and is further described in Ref
(1).
NOTE 8—The apparatus shown in Fig. 1 and Fig. 2 is based on Ref. (1) and should be considered an example. A different apparatus may be used if it
has been shown to meet the performance requirements of this section.
12.1.2 Stopper—A stopper which will not react with the dissolution matrix must be used. A solid stopper inserted in a hollow,
polyethylene stopper liner has been found to be satisfactory. Certain fluorinated elastomers, designated as FKMs, have also been
found to be satisfactory.
12.1.3 Spring clamp that will hold the tube snugly to the reflux condenser, but will release pressure at a level well below the failure
point of the tube. (Warning—The spring clamp must be selected to ensure that the tube releases pressure well below the point
that would cause the tube to fail physically. A suggested value is 827 kPa (120 psi) but should be verified prior to use. Only one
clamp should be used so as not to compromise this safety feature.)
12.1.4 Weighing pan.
12.2 Reagents:
12.2.1 Hydrochloric Acid, concentrated (sp gr 1.18), 12 M.
C1168 − 23
FIG. 1 Sealed-Reflux Dissolution Tube
FIG. 2 Heating Block
12.2.2 Hydrochloric Acid, 1 M—Add 83 mL of 12 M HCl to <900 mL of water and dilute to 1 L with water.
12.2.3 Hydrofluoric Acid, concentrated (sp gr 1.17), 28 M.
12.2.4 Hydrofluoric Acid, 1.3 M—Transfer 4.8 mL of 28 M HF, using a plastic pipet, to a 100-mL100 mL plastic graduated
cylinder containing <90 mL of water and dilute to 100 mL with water. Transfer to a plastic bottle for storage.
12.2.5 Nitric Acid, concentrated (sp gr 1.42), 16 M.
C1168 − 23
12.3 Procedure:
12.3.1 Tare a weighing pan or other type of container.
12.3.2 Transfer sample to the tared pan or other container until the desired weightmass of sample is obtained, usually 0.5 g. Weigh
to at least 0.1 mg sensitivity.
12.3.3 Quantitatively transfer the sample from the pan into a sealed-reflux tube, see Fig. 1.
12.3.4 Reweigh the pan. Compute the weightmass of s
...