ASTM D1943-20

Standard Test Method for Alpha Particle Radioactivity of Water 

SIGNIFICANCE AND USE
5.1 This test method was developed for the purpose of measuring gross alpha radioactivity in water. It is used for the analysis of both process and environmental water to determine gross alpha activity which is often a result of natural radioactivity present in minerals.
SCOPE
1.1 This test method covers the measurement of alpha particle activity of water. It is applicable to nuclides that emit alpha particles with energies above 3.9 MeV and at activity levels above 0.02 Bq/mL (540 pCi/L) of radioactive homogeneous water. This test method is not applicable to samples containing alpha-emitting radionuclides that are volatile under conditions of the analysis.  
1.2 This test method can be used for either absolute or relative determinations. In tracer work, the results may be expressed by comparison with a standard that is defined to be 100 %. For radioassay, data may be expressed in terms of alpha disintegration rates after calibration with a suitable standard. General information on radioactivity and measurement of radiation has been published in Refs (1-3)2 and summarized in Practices D3648.  
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.4 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.  
1.5 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: 14-Oct-2020
• ICS: 13.060.60 - Examination of physical properties of water
• Technical Committee: D19 - Water
• Drafting Committee: D19.04 - Methods of Radiochemical Analysis

Relations

• Refers: ASTM D1129-13(2020)e2 - Standard Terminology Relating to Water
• Effective Date: 01-May-2020
• Refers: ASTM D7902-20 - Standard Terminology for Radiochemical Analyses
• Effective Date: 01-May-2020
• Refers: ASTM D4448-01(2019) - Standard Guide for Sampling Ground-Water Monitoring Wells
• Effective Date: 01-Feb-2019
• Refers: ASTM D7902-18 - Standard Terminology for Radiochemical Analyses
• Effective Date: 01-Feb-2018
• Refers: ASTM D7902-16 - Standard Terminology for Radiochemical Analyses
• Effective Date: 01-Feb-2016
• Refers: ASTM D7902-14 - Standard Terminology for Radiochemical Analyses
• Effective Date: 15-Jan-2014
• Refers: ASTM D7902-14e1 - Standard Terminology for Radiochemical Analyses
• Effective Date: 15-Jan-2014
• Refers: ASTM D4448-01(2013) - Standard Guide for Sampling Ground-Water Monitoring Wells
• Effective Date: 01-Apr-2013
• Refers: ASTM D2777-12 - Standard Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
• Effective Date: 15-Jun-2012
• Refers: ASTM D3648-04(2011) - Standard Practices for the Measurement of Radioactivity
• Effective Date: 01-Jan-2011
• Refers: ASTM D3370-10 - Standard Practices for Sampling Water from Closed Conduits
• Effective Date: 01-Dec-2010
• Refers: ASTM D1129-10 - Standard Terminology Relating to Water
• Effective Date: 01-Mar-2010
• Refers: ASTM D3370-08 - Standard Practices for Sampling Water from Closed Conduits
• Effective Date: 01-Oct-2008
• Refers: ASTM D2777-08 - Standard Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
• Effective Date: 15-Jan-2008
• Refers: ASTM D3370-07 - Standard Practices for Sampling Water from Closed Conduits
• Effective Date: 01-Dec-2007

Overview

ASTM D1943-20 is the internationally recognized standard test method for determining alpha particle radioactivity in water. Developed by ASTM International, this method is essential for assessing gross alpha activity in both process and environmental water samples. Alpha radioactivity is a common occurrence in water due to naturally occurring minerals, making this standard valuable for regulatory compliance, environmental monitoring, and industrial water quality control.

This test method applies to water containing alpha-emitting nuclides with particle energies above 3.9 MeV and at concentrations greater than 0.02 Bq/mL (540 pCi/L). It is not suitable for measuring volatile alpha emitters under the analysis conditions.

Key Topics

• Measurement Range and Limitations
  • Targeted at non-volatile, alpha-emitting radionuclides with energies >3.9 MeV.
  • Valid for water with activity levels above 0.02 Bq/mL.
• Applicability
  • Suitable for both absolute and relative determinations. Results may be compared against calibration standards or reported as disintegration rates after appropriate calibration.
• Test Method Summary
  • Water samples are concentrated by evaporation or chemical techniques.
  • Alpha radioactivity is measured using proportional counters or scintillation detectors.
  • Results can be expressed in Bq/mL based on detector efficiency and standard calibration.
• Safety and Compliance
  • Emphasizes the need for users to establish proper safety, health, and environmental practices.
  • Adherence to international standardization guidelines, supporting regulatory acceptance.

Applications

ASTM D1943-20 is widely used across industries and regulatory bodies for the following purposes:

• Drinking Water Compliance
  • Detects gross alpha activity to ensure water supply safety in accordance with public health regulations.
• Environmental Monitoring
  • Supports regular surveillance of surface water, groundwater, and effluents around industrial sites, mining operations, and nuclear facilities.
• Industrial Process Control
  • Monitors and controls the radioactive content in water used in manufacturing, energy production, and chemical processes.
• Radiochemical Research
  • Facilitates tracer studies and research requiring measurement of alpha particle concentrations in laboratory and field settings.

Related Standards

This test method references and is harmonized with several other ASTM standards important for water quality testing and radiochemical analysis, including:

• ASTM D1129: Terminology Relating to Water
• ASTM D1193: Specification for Reagent Water
• ASTM D2777: Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
• ASTM D3370: Practices for Sampling Water from Flowing Process Streams
• ASTM D3648: Practices for the Measurement of Radioactivity
• ASTM D4448: Guide for Sampling Ground-Water Monitoring Wells
• ASTM D6001: Guide for Direct-Push Groundwater Sampling for Environmental Site Characterization
• ASTM D7282: Practice for Setup, Calibration, and Quality Control of Instruments Used for Radioactivity Measurements
• ASTM D7902: Terminology for Radiochemical Analyses

Summary

Implementing ASTM D1943-20 ensures reliable, precise, and standardized measurement of gross alpha activity in water. The method provides foundational support for environmental health, water quality compliance, and effective industrial process management, making it an indispensable tool for laboratories and facilities tasked with radiological monitoring.

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: D1943 − 20
Standard Test Method for
Alpha Particle Radioactivity of Water
This standard is issued under the fixed designation D1943; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope 2. Referenced Documents
1.1 This test method covers the measurement of alpha 2.1 ASTM Standards:
particle activity of water. It is applicable to nuclides that emit D1129Terminology Relating to Water
alpha particles with energies above 3.9 MeV and at activity D1193Specification for Reagent Water
levels above 0.02 Bq/mL (540 pCi/L) of radioactive homoge- D2777Practice for Determination of Precision and Bias of
neous water. This test method is not applicable to samples Applicable Test Methods of Committee D19 on Water
containing alpha-emitting radionuclides that are volatile under D3370Practices for Sampling Water from Flowing Process
conditions of the analysis. Streams
D3648Practices for the Measurement of Radioactivity
1.2 This test method can be used for either absolute or
D4448GuideforSamplingGround-WaterMonitoringWells
relative determinations. In tracer work, the results may be
D6001Guide for Direct-Push Groundwater Sampling for
expressed by comparison with a standard that is defined to be
Environmental Site Characterization
100%.Forradioassay,datamaybeexpressedintermsofalpha
D7282Practice for Set-up, Calibration, and Quality Control
disintegration rates after calibration with a suitable standard.
of Instruments Used for Radioactivity Measurements
General information on radioactivity and measurement of
D7902Terminology for Radiochemical Analyses
radiation has been published in Refs (1-3) and summarized in
Practices D3648.
3. Terminology
1.3 The values stated in SI units are to be regarded as
3.1 Definitions:
standard. No other units of measurement are included in this
3.1.1 For definitions of terms used in this standard, refer to
standard.
Terminologies D1129 and D7902.
1.4 This standard does not purport to address all of the
3.1.2 For terms not defined in this standard, Terminology
safety concerns, if any, associated with its use. It is the
D1129, or Terminology D7902, reference may be made to
responsibility of the user of this standard to establish appro-
other published glossaries.
priate safety, health, and environmental practices and deter-
4. Summary of Test Method
mine the applicability of regulatory limitations prior to use.
1.5 This international standard was developed in accor-
4.1 The test sample is reduced by evaporation or a suitable
dance with internationally recognized principles on standard-
chemical method to the minimum weight of material having
ization established in the Decision on Principles for the
measurable alpha activity. Alpha radioactivity is measured by
Development of International Standards, Guides and Recom-
aninstrumentcomposedofadetectingdevice,amplifier,power
mendations issued by the World Trade Organization Technical
supply, and scaler—the most widely used being proportional
Barriers to Trade (TBT) Committee.
and scintillation counters. In the proportional counter, which
may be of the windowless or thin window type, alpha particles
1 entering the sensitive region of the detector produce ionization
This test method is under the jurisdiction ofASTM Committee D19 on Water
andisthedirectresponsibilityofSubcommitteeD19.04onMethodsofRadiochemi- of the counting gas.The negative ion of the original ion pair is
cal Analysis.
Current edition approved Oct. 15, 2020. Published November 2020. Originally
approved in 1996. Last previous edition approved in 2012 as D1943–05 (2012). For referenced ASTM standards, visit the ASTM website, www.astm.org, or
DOI: 10.1520/D1943-20. contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
The boldface numbers in parentheses refer to a list of references at the end of Standards volume information, refer to the standard’s Document Summary page on
this standard. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D1943 − 20
accelerated towards the anode, producing additional ionization to 15% loss at 1 mg/cm . Liquid samples shall be evaporated
of the counting gas and developing a voltage pulse at the to dryness onto dishes that allow the sample to be counted
anode.Inthescintillationdetector,alphaparticlesinteractwith
directly by the detector. Solids on the dish shall remain
the material of the phosphor, transferring some of their energy
constant in amount between related test samples, and should
to electrons. These electrons subsequently lose part of their
duplicate the density of the solids of the plated standard.
energy by excitation rather than ionization of atoms, and the
7.2 Mostalphacountersareinsensitivetobeta,gamma,and
excited atoms revert to the ground state by re-emitting energy
X-ray (1-3).
in the form of light quanta. A suitable light-sensitive device,
usually a photomultiplier or solid-state diode, transforms the
8. Apparatus
resulting flashes of light into voltage pulses. By use of suitable
electronic apparatus, the pulse is amplified to a voltage
8.1 Alpha Particle Counter, consisting of either a propor-
sufficient for operation of the counting scaler. The number of
tionaldetectororascintillationdetector,andascalerconform-
pulses per unit time is related to the disintegration rate of the
ing to the following requirements:
test sample.The efficiency of the system can be determined by
8.1.1 Proportional Detector—This may be one of several
use of a suitable alpha standard having equivalent residual
types commercially available. The material used in the con-
plated solids.
struction of the detector should contain a minimal amount of
detectableradioactivity.Toestablishfreedomfromundesirable
5. Significance and Use
characteristics, the manufacturer shall supply voltage plateau
5.1 This test method was developed for the purpose of
and background counting rate data. Voltage plateau data shall
measuring gross alpha radioactivity in water. It is used for the
show the threshold voltage, slope, and length of plateau for a
analysis of both process and environmental water to determine
particular input sensitivity.
gross alpha activity which is often a result of natural radioac-
8.1.2 Scintillation Detector—This may be one of several
tivity present in minerals.
types commercially available. It shall consist of an “activated”
6. Measurement Variables
zinc sulfide phosphor having a minimum effective diameter of
36.5 mm and a superficial density of 10 to 15 mg/cm . The
6.1 The relatively high absorption of alpha particles in the
phosphor shall be mounted so that it can be attached and
sample media affects the counting rate of the measurement.
optically coupled to a multiplier phototube. Extraneous light
Effects of geometry, back-scatter, source diameter, as well as
the purity, pressure variation, and type of counting gas used shallbeexcludedfromthephosphoreitherbyitsbeingcovered
shall also be considered. Thus, for reliable relative with a thin (less than 1 mg/cm ) opaque window or by
measurements, the variables shall be held constant while
enclosing the assembly in a lightproof sample changer. The
counting all test samples and standards. For absolute
material used in the construction of the detector shall be free
measurements, appropriate efficiency factors shall be applied.
from detectable radioactivity.To establish freedom from unde-
If a windowless proportional counter is employed, the sample
sirable characteristics, the manufacturer shall supply voltage
mount shall be electrically conducting.
plateau and background counting rate data. Voltage plateau
6.1.1 In tracer studies or tests requiring only relative
data shall show the threshold voltage, slope, and length of a
measurements, in which the data are expressed as being
plateau for a specified scaler sensitivity.
equivalent to a defined standard, the above correction factors
8.1.3 Scaler—Often the scaler, power supply, and amplifier
can be simply combined into a counting efficiency factor. The
are contained in a single chassis, generally termed the scaler.
use of a counting efficiency factor requires that sample
Thepowersupplyandamplifiersectionsshallbematchedwith
mounting, material of mounting dish, and weight of residue
the type of detector to produce satisfactory operating charac-
(milligrams per square centimetre), in addition to conditions
teristics and to provide sufficient range in adjustments to
affectingtheabovedescribedfactors,remainconstantthrough-
maintaincontrolledconditions.Themanufacturershallprovide
outthedurationofthetestandthatthecomparativestandardbe
resolving time information for the counting system.The scaler
prepared for counting in the same manner as the test samples.
shall have capacity for storing and visually displaying at least
The data from comparative studies between independent labo-
10 counts with a resolving time no greater than 5 µs. The
ratories when not expressed in absolute units are more mean-
instrumentshallhaveanadjustableinputsensitivitythatcanbe
ingfulwhenexpressedaspercentagerelationshipsorasequiva-
matched to the detector and a variable high voltage power
lent of a defined standard.
supply with indicating meter.
6.2 Thelimitofsensitivityforbothscintillationandpropor-
tional counters is a function of the background counting rate 8.2 Sample Mounting Dish—Dishes having a flat bottom of
which should be as low as is feasible. Massive shielding is not adiameterslightlylessthantheinsidediameterofthedetector.
used for alpha counters. The maximum activity for this test Flat dishes are preferred, but dishes may be used that have 3.2
method is 1600 Bq.
mm high side walls with the angle between dish bottom and
sideequaltoorgreaterthan120°.Dishesshallbeofamaterial
7. Interferences
that will not corrode under the plating conditions and shall be
of uniform surface density; platinum and stainless steel have
7.1 Solidscontentinthesamplecontainingthealphaemitter
producessignificantlossesinsamplecountingratesofabout10 been used for this purpose.
D1943 − 20
9. Reagents observed and record the “threshold” voltage. Advance the
voltageinincrementsofconvenientmagnitude(approximately
9.1 Purity of Reagents—Reagent grade chemicals shall be
25 V) and determine the counting rate at four or more settings
used in all tests. Unless otherwise indicated, it is intended that
of the sensitivity control at each voltage setting. Measure the
all reagents shall conform to the specifications of the Commit-
backgroundcountingrateateachofthesettingsusinganempty
tee onAnalytical Reagents of theAmerican Chemical Society,
sample mounting dish in place of the standard.
where such specifications are available. Other grades may be
11.1.1 The QC source may be any available alpha-emitting
used, provided it is first ascertained that the reagent is of
radionuclide having a half-life sufficiently long to eliminate
sufficiently high purity and free from radioactivity to preclude
decay corrections. Knowledge of its true disintegration rate is
detrimental effects. Some chemicals, even of high purity,
not essential. The radionuclide shall be permanently fixed to
contain naturally occurring radioactive elements, for example,
the dish and uniformly distributed over an area preferably
uranium, actinium, and thorium. Consequently, when carrier
smallerthanthedishbottom;electro-depositionandflamingof
chemicals are used in the analysis of low-radioactivity
a salt-flee solution are the two methods most generally used.
samples, the radioactivity of the carriers shall be determined
Quality control sources are commercially available.
under identical analytical conditions of the sample including
residual dish solids. The radioactivity of the reagents shall be 11.2 Plot the gross counting rate of the standard against the
considered as background and subtracted from the test sample voltage.Thecountingrateshouldriseinitiallyasthevoltageis
counting rate. increased, then, for at least some of the settings of the
sensitivity control, reach an approximate constant value, and
9.2 Purity of Water—Unless otherwise indicated, references
finally rise again.The“ plateau” of the curve should be at least
towatershallbeunderstoodtomeanreagentwaterconforming
100 V in length and have a slope less than 2%⁄100 V;
to Specification D1193, Type III.
however, shorter plateaus or one with greater slope shall be
9.3 Nitric Acid (sp gr 1.42)—Concentrated nitric acid
acceptable if a well-regulated high voltage power supply is
(HNO ).
available.
9.4 Nitric Acid (1+30)—Mix 1 volume of concentrated
11.3 Plot the ratio of the square of the net counting rate of
HNO (sp gr 1.42) with 30 volumes of water.
the standard to the background counting rate against the
voltage for each of the settings of the sensitivity control.
9.5 Alpha-Emitting Radioactive Standard Solution (;200
Bq/mL), traceable to the SI through a national metrology
11.4 Determinetheoptimumconditionsforoperationofthe
insti
...

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: D1943 − 05 (Reapproved 2012) D1943 − 20
Standard Test Method for
Alpha Particle Radioactivity of Water
This standard is issued under the fixed designation D1943; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope
1.1 This test method covers the measurement of alpha particle activity of water. It is applicable to nuclides that emit alpha particles
with energies above 3.9 MeV and at activity levels above 0.02 Bq/mL (540 pCi/L) of radioactive homogeneous water. This test
method is not applicable to samples containing alpha-emitting radionuclides that are volatile under conditions of the analysis.
1.2 This test method can be used for either absolute or relative determinations. In tracer work, the results may be expressed by
comparison with a standard that is defined to be 100 %. For radioassay, data may be expressed in terms of alpha disintegration rates
after calibration with a suitable standard. General information on radioactivity and measurement of radiation has been
published published in Refs (1-3) and summarized in PracticePractices D3648.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.5 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:
D1129 Terminology Relating to Water
D1193 Specification for Reagent Water
D2777 Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
D3370 Practices for Sampling Water from Flowing Process Streams
D3648 Practices for the Measurement of Radioactivity
This test method is under the jurisdiction of ASTM Committee D19 on Water and is the direct responsibility of Subcommittee D19.04 on Methods of Radiochemical
Analysis.
Current edition approved June 1, 2012Oct. 15, 2020. Published August 2012November 2020. Originally approved in 1996. Last previous edition approved in 20052012
as D1943 – 05.D1943 – 05 (2012). DOI: 10.1520/D1943-05R12.10.1520/D1943-20.
Friedlander, G., et al.,The boldface numbers in Nuclear and Radiochemistry,parentheses refer to 3rd Ed., John Wiley and Sons, Inc., New York, NY, 1981.a list of
references at the end of this standard.
Price, W. J., Nuclear Radiation Detection, 2nd Ed., McGraw-Hill Book Co., Inc., New York, NY, 1964.
Lapp, R. E., and Andrews, H. L., Nuclear Radiation Physics, 4th Ed., Prentice-Hall Inc., New York, NY, 1972.
Overman, R. T., and Clark, H. M., Radioisotope Techniques, McGraw-Hill Book Co., Inc., New York, NY, 1960.
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’sstandard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D1943 − 20
D4448 Guide for Sampling Ground-Water Monitoring Wells
D6001 Guide for Direct-Push Groundwater Sampling for Environmental Site Characterization
D7282 Practice for Set-up, Calibration, and Quality Control of Instruments Used for Radioactivity Measurements
D7902 Terminology for Radiochemical Analyses
3. Terminology
3.1 Definitions—For definitions of terms used in this test method, refer to Terminology D1129. For terms not defined in this
test method or in Terminology D1129, reference may be made to other published glossaries.
3.1 Definitions:
3.1.1 For definitions of terms used in this standard, refer to Terminologies D1129 and D7902.
3.1.2 For terms not defined in this standard, Terminology D1129, or Terminology D7902, reference may be made to other
published glossaries.
4. Summary of Test Method
4.1 The test sample is reduced by evaporation or a suitable chemical method to the minimum weight of material having
measurable alpha activity. Alpha radioactivity is measured by an instrument composed of a detecting device, amplifier, power
supply, and scaler—the most widely used being proportional and scintillation counters. In the proportional counter, which may be
of the windowless or thin window type, alpha particles entering the sensitive region of the detector produce ionization of the
counting gas. The negative ion of the original ion pair is accelerated towards the anode, producing additional ionization of the
counting gas and developing a voltage pulse at the anode. In the scintillation detector, alpha particles interact with the material of
the phosphor, transferring some of their energy to electrons. These electrons subsequently lose part of their energy by excitation
rather than ionization of atoms, and the excited atoms revert to the ground state by re-emitting energy in the form of light quanta.
A suitable light-sensitive device, usually a multiplier phototube, photomultiplier or solid-state diode, transforms the resulting
flashes of light into voltage impulses.pulses. By use of suitable electronic apparatus, the pulse is amplified to a voltage sufficient
for operation of the counting scaler. The number of pulses per unit time is related to the disintegration rate of the test sample. The
efficiency of the system can be determined by use of a suitable alpha standard having equivalent residual plated solids.
5. Significance and Use
5.1 This test method was developed for the purpose of measuring gross alpha radioactivity in water. It is used for the analysis of
both process and environmental water to determine gross alpha activity which is often a result of natural radioactivity present in
minerals.
6. Measurement Variables
6.1 The relatively high absorption of alpha particles in the sample media affects the counting rate of the measurement. Effects of
geometry, back-scatter, source diameter, as well as the purity, pressure variation, and type of counting gas used shall also be
considered. Thus, for reliable relative measurements, the variables shall be held constant while counting all test samples and
standards. For absolute measurements, appropriate efficiency factors shall be applied. If a windowless proportional counter is
employed, the sample mount shall be electrically conducting.
6.1.1 In tracer studies or tests requiring only relative measurements, in which the data are expressed as being equivalent to a
defined standard, the above correction factors can be simply combined into a counting efficiency factor. The use of a counting
efficiency factor requires that sample mounting, material of mounting dish, and weight of residue (milligrams per square
centimetre), in addition to conditions affecting the above described factors, remain constant throughout the duration of the test and
that the comparative standard be prepared for counting in the same manner as the test samples. The data from comparative studies
between independent laboratories when not expressed in absolute units are more meaningful when expressed as percentage
relationships or as equivalent of a defined standard.
6.2 The limit of sensitivity for both scintillation and proportional counters is a function of the background counting rate which
should be as low as is feasible. Massive shielding is not used for alpha counters. The maximum activity for this test method is 1600
Bq.
D1943 − 20
7. Interferences
7.1 Solids content in the sample containing the alpha emitter produces significant losses in sample counting rates of about 10 to
15 % loss at 1 mg/cm mg/cm . Liquid samples shall be evaporated to dryness onto dishes that allow the sample to be counted
directly by the detector. Solids on the dish shall remain constant in amount between related test samples, and should duplicate the
density of the solids of the plated standard.
7.2 Most alpha counters are insensitive to beta, gamma, and XX-ray radiations. (1-3).
8. Apparatus
8.1 Alpha Particle Counter, consisting of either a proportional detector or a scintillation detector, and a scaler conforming to the
following requirements:
8.1.1 Proportional Detector—This may be one of several types commercially available. The material used in the construction of
the detector should contain a minimal amount of detectable radioactivity. To establish freedom from undesirable characteristics,
the manufacturer shall supply voltage plateau and background counting rate data. Voltage plateau data shall show the threshold
voltage, slope, and length of plateau for a particular input sensitivity.
8.1.2 Scintillation Detector—This may be one of several types commercially available. It shall consist of an “activated” zinc
sulfide phosphor having a minimum effective diameter of 36.5 mm and a superficial density of 10 to 15 mg/cm mg/cm . The
phosphor shall be mounted so that it can be attached and optically coupled to a multiplier phototube. Extraneous light shall be
excluded from the phosphor either by its being covered with a thin (less than 1 mg/cm mg/cm ) opaque window or by enclosing
the assembly in a lightproof sample changer. The material used in the construction of the detector shall be free from detectable
radioactivity. To establish freedom from undesirable characteristics, the manufacturer shall supply voltage plateau and background
counting rate data. Voltage plateau data shall show the threshold voltage, slope, and length of a plateau for a specified scaler
sensitivity.
8.1.3 Scaler—Often the scaler, mechanical register, power supply, and amplifier are contained in a single chassis, generally termed
the scaler. The power supply and amplifier sections shall be matched with the type of detector to produce satisfactory operating
characteristics and to provide sufficient range in adjustments to maintain controlled conditions. The manufacturer shall provide
resolving time information for the counting system. The scaler shall have capacity for storing and visually displaying at least 10 10
counts with a resolving time no greater than 5 μs. The instrument shall have an adjustable input sensitivity that can be matched
to the detector and a variable high voltage power supply with indicating meter.
8.2 Sample Mounting Dish—Dishes having a flat bottom of a diameter slightly less than the inside diameter of the detector. Flat
dishes are preferred, but dishes may be used that have 3.2-mm 3.2 mm high side walls with the angle between dish bottom and
side equal to or greater than 120°. Dishes shall be of a material that will not corrode under the plating conditions and shall be of
uniform surface density; platinum and stainless steel have been used for this purpose.
9. Reagents
9.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all
reagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society, where
such specifications are available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high
purity and free from radioactivity to preclude detrimental effects. Some chemicals, even of high purity, contain naturally occurring
radioactive elements, for example, uranium, actinium, and thorium. Consequently, when carrier chemicals are used in the analysis
of low-radioactivity samples, the radioactivity of the carriers shall be determined under identical analytical conditions of the
sample including residual dish solids. The radioactivity of the reagents shall be considered as background and subtracted from the
test sample counting rate.
American National Standard Glossary of Terms in Nuclear Science and Technology (ANSI N1.1) available from the American National Standards Institute, 1430
Broadway, New York, NY 10018.
Reagent Chemicals, American Chemical Society Specifications,ACS Reagent Chemicals, Specifications and Procedures for Reagents and Standard-Grade Reference
Materials, American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed by the American Chemical Society, see Analar Standards for
Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and National Formulary, U.S. PharmaceuticalPharmacopeial Convention, Inc.
(USPC), Rockville, MD.
D1943 − 20
9.2 Purity of Water—Unless otherwise indicated, references to water shall be understood to mean reagent water conforming to
Specification D1193, Type HI.III.
9.3 Nitric Acid (sp gr 1.42)—Concentrated nitric acid (HNO ).
9.4 Nitric Acid (1 + 30)—Mix 1 volume of concentrated HNO (sp gr 1.42) with 30 volumes of water.
9.5 Alpha-Emitting Radioactive Standard Solution (;200 Bq/mL), traceable to the SI through a national metrology institute
(NMI) such as National Institute of Standards and Technology (NIST).Science and Technology (NIST) in the United States and
the National Physical Laboratory (NPL) in the United Kingdom.
10. Sampling
10.1 Collect the sample in accordance with Practices D3370., Guide D4448, or Guide D6001, as applicable.
10.2 Preserve the sample in a radioactive homogeneous state. A sample shall be made radioactive homogeneous by addition of
a reagent in which the radionuclides or compounds of the radionuclides present would be soluble in large concentrations. Addition
of acids, complexing agents, or stable chemically similar carriers may be used to obtain homogeneity. Consideration of the
chemical nature of the radionuclides and compounds present and the subsequent chemistry of the method shall indicate the action
to be taken.
11. Establishing Gas Proportional Counter Operating Plateau
11.1 Put the instrument into operation according to the manufacturer’smanufacturer’s instructions. Place a quality control (QC)
source in the detector, set the sensitivity control near its maximum and turn the “count” switch to “count” position. Slowly increase
the high voltage until the first counts are observed and record the “threshold” voltage. Advance the voltage in increments of
convenient magnitude (approximately 25 V) and determine the counting rate at four or more settings of the sensitivity control at
each
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