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Purpose

The purpose of this Procedure is twofold:

1) To document the quality procedures used to ensure that the NIST Standard Reference Materials 

(SRMs) for Radioactivity Measurements are of the highest metrological quality, and

2) To document the principles and practices of the production processes of the radioactivity SRMs.

There are a wide range of individual values and protocols that could be used to produce a radioactivity 

SRM. Hence, the exact values of properties and the exact production details of the current radioactivity 

SRMs are presented in appendices rather than in the body of this Procedure.

Background

NIST radioactivity SRMs represent the national basis for accurate radioactivity measurements. A number 

of commercial companies provide secondary radioactivity standards, both for specific and general needs. 

These secondary standards are linked to the NIST-produced national standards through Measurement 

Assurance Programs with NIST. Generally, the radioactivity SRMs that are available from NIST are 

provided for one of several reasons: (a) they are not available from outside commercial suppliers, (b) 

commercially-produced standards may not be traceable to national standards, (c) the accuracy of 

commercially-produced standards is not adequate for a significant number of users, or (d) there are enough 

requests from the user community for a standard not otherwise available. Radioactivity SRMs can 

typically be classified into three general categories: (1) environmental and nuclear power, (2) medicine, 

and (3) basic and applied research using or involving radioactivity in the development of nuclear data and 

the examination of basic nuclear processes.

NIST issues a wide array of SRMs for radioactivity measurements. Typically, there are 50 to 60 such 

SRMs in stock; calibrations have been performed on approximately 80 different radionuclides. Expanded 

uncertainties of these calibrations are typically 1 percent or less. These calibrations are performed using 

approximately 20 radiometric and a few mass spectrometric methods. The SRMs are issued in a number of 

configurations, including acidic solutions of alpha- and beta-particle and gamma-, and x-ray emitting 

radionuclides, gases, and various matrix materials. The NIST Complex Matrix radioactivity SRMs (see 

RPD Procedure 16) are a result of a collaboration of national and international environmental laboratories. 

These SRMs are distributed as ground, homogenized powders of soils, sediments, and organic materials 

and are characterized for as many as 20 radionuclides at environmental levels.

NIST radioactivity measurements are compared with the primary standards of other National Metrology 

Institutes (NMIs) through international measurement comparisons, including those organized and 

evaluated by the International Bureau of Weights and Measures (BIPM). The results of such international 

comparisons, as well as an extensive data file of NIST Calibration and Measurement Capabilities (CMCs), 

may be found on the BIPM website at www.bipm.org.

Scope

Appendix A1 lists the properties of 48 radioactivity SRMs that are in stock or in preparation as of October

2019. The certified massic activities (activity divided by the total mass of the sample [1]) of the 

radioactivity SRMs have a range of more than 9 orders of magnitude, from less than 10-3 Bq·g-1to more 

than 106 Bq·g-1. The half-lives have a range of more than 13 orders of magnitude, from less than 10-3 years 

(6 hours) to more than 1010 years. Radioactivity SRMs with short half-lives are available only at certain 

preannounced times. The radionuclides range from hydrogen-3 (Z = 1) to curium-244 (Z = 96), and 

include solids, liquids, and gases.
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For such a wide variety of radioactivity SRMs there is not a single procedure (or even a small number of 

procedures) that can be used to describe how they are made. There is, however, a sequence of steps that 

can be used to describe, in general, the production process of an SRM, including a radioactivity SRM. 

Each of these steps is discussed in greater detail in the Procedures section of this document. Within each 

step, the intent will be generally the same, but the exact sequence of the steps and the exact procedure by 

which each step is carried out may vary from SRM to SRM. Each of the most common procedures within 

each step will be described in detail in an appendix dedicated to that procedure. These appendices form a 

collection of "modular building blocks" from which the appropriate ones can be selected and combined to 

form the complete production procedure for any given radioactivity SRM. See Appendix A1 for the 

information necessary to construct the complete production procedure for each radioactivity SRM.

Safety

The production processes for the radioactivity SRMs involve working with radioactive materials,

sometimes at very high levels of activity and dose rate, with various acids and other chemicals, and with 

potentially dangerous equipment. Safe work practices are an essential part of the production process. See 

step 6 in the procedures section.

Equipment

The production of the NIST radioactivity SRMs involves a large number of different machines and 

measuring instruments. See step 8 in the Procedures section.

Uncertainty Analysis

A measurement result is complete only when accompanied by a quantitative statement of its uncertainty. 

The uncertainty often determines the usefulness of the measurement result. The analysis and reporting of 

measurement uncertainties is an essential step in the production process. See step 19 in the Procedures 

section.

Records

The data in the production records should be complete enough so that anyone who is reasonably familiar 

with the SRM production process can reproduce any or all of the calculations that lead to the final 

measurement results and uncertainties for the SRM (i.e., the certified values) and evaluate and reproduce 

the production process (e.g., for the next batch of that SRM). See step 22 in the Procedures section.

Filing and Retention

The radioactivity SRM production records are stored in Building 245, B50 SRM Records Storage Room. 

The production records are retained for as long as the SRM is available for sale to the public, plus at least 

an additional 10 years. See step 22 in the Procedures section.

The Radiation Physics Division (RPD) Quality Manager shall maintain the original and all past versions of 

this RPD Procedure.

Procedures

The need for a new SRM largely derives from advice from the radioactivity user community. Interactions 
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with this community include the annual CIRMS (Council on Ionizing Radiation Measurements and 

Standards) meeting, the NRMAP, Inc. steering committees, focused workshops and personal interactions 

with users within other laboratories, academia and industry. This need is usually identified by the principal 

investigator responsible for producing, calibrating and certifying the SRM. A need could also be identified 

by other Radioactivity Group (RG) members.

The responsibilities of the Radioactivity Group Leader, SRM Coordinator and SRM principal investigator 

as well as the coordination of SRM activities among them, is described in RPD-QM-II.

Below is a sequence of general steps that can be used to describe the production process of a radioactivity 

SRM.

Step 1. Determine the intended use, the requirements, and the demand for the SRM.

Insuring that each NIST radioactivity SRM is of the highest metrological quality requires more than having 

low uncertainty of the certified values. It also requires that the form, chemical composition, size, activity, 

and packaging of the SRM are such that the user can easily make correct and accurate measurements; the 

price of the SRM must also be acceptable to the intended customers. In order to help ensure all of these 

things, the RG seeks the advice of a number of organizations in addition to the requests and suggestions of 

individual customers. 

If this SRM is a renewal (i.e., the production of a new batch of an already existing, but presently out-ofstock, SRM), the previous sales record is also considered. If there is some question about the continued 

need for a particular radioactivity SRM, then previous customers for that SRM are usually consulted to 

obtain their comments and suggestions.

See Appendix A1 for the (primary) intended use for each radioactivity SRM.

Step 2. Select the chemical and physical properties of the SRM and select the chemical and physical 

quantities that are to be quantified and/or certified.

There are three basic guidelines for the selection of the chemical and physical properties of a radioactivity 

SRM:

1. The SRM should be stable (there is no chemical or physical change to the radioactivity SRM, other 

than the intrinsic radioactive decay, that changes a certified value by more than 25 percent of its stated 

uncertainty over the stated time period) for a period of at least ten half-lives of the primary 

radionuclide or for at least 20 years, whichever is less. 

2. The SRM should be as similar as is practical to the sample(s) that the customer will measure. This 

helps reduce or eliminate additional uncertainties due to dilution or due to corrections for different 

geometries, different photon absorptions, etc.

3. The SRM should be useable by as many customers as possible. For example, at the request of the U.S. 

Environmental Protection Agency, all new batches of solution radioactivity SRMs that are used as 

tracers for environmental measurements are made with nitric acid. This is because stainless-steel 

planchets are widely used to make deposited sources for environmental measurements and nitric acid 

does not significantly attack stainless steel (unlike, for example, hydrochloric acid).

There are two basic guidelines for the selection of the chemical and physical properties whose values are to 

be quantified:

1. All of the properties that are essential to the proper use of the radioactivity SRM must be described 

quantitatively. For example, some users are able to dispense solution SRMs volumetrically only using 
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a pipette. Since the solution radioactivity SRMs have certified values of massic activity (activity per 

unit mass), the solution density must be accurately quantified in order for the SRM to be useful. 

2. The precision of contributing measurements should be considered such that the expanded uncertainty 

of the SRM remains low enough to be satisfactory for the majority of users.

See Appendix A1 for the properties of each radioactivity SRM.

Step 3. Select a suitable container and packaging for the SRM.

The three basic guidelines for the selection of a suitable container for a radioactivity SRM are the same as 

for selecting the chemical and physical properties of the SRM (see step 2).

The containers currently in use for radioactivity SRMs have been selected according to these guidelines. 

See Appendix A1 for the container used for each radioactivity SRM.

As part of the production process, additional packaging is placed around the container of the radioactivity 

SRM. This packaging is designed to protect the SRM during handling and long-term storage and is 

designed to pass the performance tests for Type-A packages of radioactive material. The packaging

currently in use for the radioactivity SRMs have proven satisfactory over decades of use. 

Step 4. Select a measurement model, suitable sampling and measurement method (experimental design),

including the sequence of operations for the production process.

Four possible types of measurement models are considered for the radioactivity SRMs.

1. LMNL = Linear, Multiplicative, Normal, Low Correlation

2. LMNH = Linear, Multiplicative, Normal, High Correlation

3. LMOL = Linear, Multiplicative, Other than Normal, Low Correlation

4. NMNL = Non-Linear, Multiplicative, Normal, Low Correlation

The first type of measurement model has proven to be appropriate for most of the radioactivity SRMs. The 

measurement model is selected in consultation with the NIST Statistical Engineering Division, if needed.

Measurements are made on one or more samples of the master solution/mixture to determine the values of 

the properties that are to be quantified. In order for these measurements to be relevant to the SRM 

solution/mixture, the two solutions or mixtures must be gravimetrically related. In the RPD, only 

gravimetric measurements are used when dispensing or diluting the master and the SRM solutions.

It is clearly advantageous in terms of production effort (and often in terms of minimizing the measurement 

uncertainty as well) to have the master solution and the SRM solution be the same, and this is done 

whenever practical. For most gamma-ray-emitting radioactivity SRMs, the master solution and the SRM 

solution are the same solution. For the gamma-ray-emitting solutions, both liquids and gases, the 

unopened SRM ampoule is the sample for measurement. 

For alpha-particle-emitting and beta-particle-emitting radioactivity SRMs, the master solution and the 

SRM solution may or may not be the same solution. For the low-level environmental tracer solutions, the 

SRM solution is a quantitative dilution of the master solution. Careful and thorough mixing of the 

solutions is essential if the calibration of the master solution is to be relevant to the SRM solution. The 

master solution is gravimetrically dispensed to make point sources and/or liquid scintillation sources for 

measurement. If the master solution is to be diluted to make the SRM solution, this is usually done at the 

same time.

The selection of primary and confirmatory measurement methods depends primarily on the decay mode of 
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the primary radionuclide and on the activity and physical form of the sample(s) to be measured. The 

general criteria for the selection of a measurement method are:

1. Non-destructive to the sample (if possible)

2. Ease of measurement

3. Ease of sample preparation

4. Low measurement uncertainty

5. Selectivity (if more than one radionuclide is present)

6. High detection efficiency (especially if the decay rate is low)

There are presently 16 basic methods, some with many variations, that are used for primary, confirmatory,

and/or impurity measurements of the radioactivity SRMs. See Appendix A1 for the measurement 

method(s) used for each radioactivity SRM.

The sequence in which the required steps are to be carried out, and the required facilities, equipment, 

personnel, supplies, and funding, should be documented in whatever form is satisfactory for the purpose, 

such as lists, tables, drawings, flow charts, Gantt diagrams, etc.

Step 5. Have the proposed production process reviewed and approved.

The review and approval of the SRM production plan are carried out by the Radioactivity Group Leader

and the SRM Coordinator. A record of this review shall be maintained with the SRM documentation. 

Step 6. Have the proposed safety measures reviewed and approved by the NIST Occupational Health and

Safety Division.

The acquisition and use of radioactive material at NIST must be approved, in advance, by the NIST 

Radiation Safety Division (RSD), part of the NIST Office of Safety, Health and Environment, in the 

context of an Ionizing Radiation Safety Committee (IRSC)-approved Safety Evaluation (SE). For the 

radioactivity SRM production process, this is done by submitting a Proposed Use Request under a specific 

SE, along with a properly signed (by the RG Leader and RPD Chief) NIST 364 “Radioactive Material 

Request,” or NIST 365 “Change to Radioactive Material Authorization” for approval. Once approved by 

RSD, the proposed use is assigned an identification number and can be referenced in future production 

processes. 

Step 7. Obtain the necessary funding.

This step is normally carried out by the radioactivity SRM production Coordinator together with the RG 

leader. Funding of a radioactivity SRM production from the SRM Working Capital Fund requires the 

approval of the RPD Chief, and the Office of Refence Materials

Step 8. Arrange for the use of the necessary facilities, equipment, and personnel

A number of suitable general purpose radiochemistry laboratories are available in the NIST Radiation 

Physics Division/Radioactivity Group (RPD/RG) for the preparation of radioactivity SRMs and 

measurement of samples. The production of the NIST radioactivity SRMs involves a large number of 

different machines and measuring instruments. It is the intent of the RPD/RG that there are enough units 

of each type of equipment available so that no one piece of equipment is essential to the production process 

of any SRM. For example, the preparation of 50 mg radioactive point sources may require a microbalance 

with a capacity of >7 g, a readability of <5 μg, and a standard uncertainty of <50 μg (relative to the SI). 

The RPD/RG currently has at least 6 balances that meet these specifications, all of which are serviced and 

calibrated once per year with NIST traceable masses.
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This step is normally carried out by, or in cooperation with, the Coordinator of radioactivity SRM 

production and with the concurrence of the RG leader.

Step 9. Acquire suitable materials.

As used here, materials include

a. the radioactive material for the radioactivity SRM,

b. chemical reagents and other consumable materials, and

c. SRM containers, glassware, and other laboratory supplies.

Most radionuclides used to produce radioactivity SRMs are available from commercial suppliers. 

Radionuclidic purity and carrier concentration vary somewhat, but one can usually purchase suitable 

radioactive starting material that does not require any additional chemical purification. A few 

radionuclides that are used for radioactivity SRMs are the parent of a radioactive decay chain and chemical 

purification may be necessary to improve the calibration accuracy or because of the way in which the SRM 

is used. 

Chemical reagents used as solvents and non-radioactive carriers are at least Analytical Grade reagents, and 

each bottle is provided with a lot analysis. Spectroscopic Grade reagents or Trace Element Grade reagents 

are preferred.

Borosilicate glass or Teflon containers are always used for solution radioactivity SRMs.

Step 10. Prepare and characterize the materials (as necessary).

The SRM containers, glassware, and other laboratory supplies are prepared, as necessary, using standard 

analytical laboratory techniques for washing, rinsing, drying, labeling, etc.

For most of the radioactivity SRMs, the radioactive starting material is received as a solution. The material 

is measured for radiological (and sometimes chemical) impurities. This is typically done using gamma-ray 

spectrometry. If the radioactive material is a pure alpha-particle emitter or a pure beta-particle emitter, a 

portion of the solution may also be measured using alpha-particle or beta-particle spectrometry. 

Depending upon the nature and level of the impurities, additional chemical separation may be required.

Step 11. Prepare the master solution (or mixture) and, if different from the master, the SRM solution (or 

mixture).

The master solution or mixture is the material that is calibrated, and the measurements on this material are 

used to determine the certified values; it is always gravimetrically related to the SRM solution or mixture. 

The massic activity of the master solution is optimized for the calibration measurements.

For solution radioactivity SRMs, the density of the SRM solution is measured because some users are able 

to dispense solution SRMs volumetrically only using a pipette. In the RPD/RG, only gravimetric 

measurements are used when dispensing or diluting the master and the SRM solutions. 

Step 12. Dispense the SRM solution (or mixture) into the SRM containers.

Solution radioactivity SRMs are prepared using a precision liquid dispenser to dispense the SRM solution. 

For gamma-ray-emitting solution SRMs, the volume of solution is (5.0 ± 0.1) mL in a NIST standard 5 

mL borosilicate-glass ampoule (from a NIST ampoule stock reserved for this purpose), and each ampoule 
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is weighed before and after filling (some gamma-ray-emitting solution SRMs are used for measurements as 

the unopened ampoule). Since the solution radioactivity SRMs have certified values of activity per unit 

mass, the total mass of the solution in the ampoule must also be measured and included in the certificate.

For alpha-particle-emitting and beta-particle-emitting radioactivity SRMs, the ampoules are also made of 

borosilicate glass but need not be NIST standard 5 mL ampoules. The volume of solution is approximately 

5.0 mL, and some of the ampoules (usually >10 %) are weighed before and after filling. The mass of the 

solution may or may not be included in the certificate as alpha-particle and beta-particle measurements 

cannot be made on the solution in an unopened ampoule.

For gaseous radioactivity SRMs, the borosilicate-glass gas ampoules are filled to a measured pressure, 

usually somewhat less than atmospheric pressure, using a vacuum rack and a gas transfer system. No 

attempt is made to measure the exact volume of a gas ampoule. Gas ampoules are certified in terms of the 

total activity in each ampoule.

Step 13. Seal and inspect the SRM containers.

Ampoules: All ampoules are flame sealed. Each ampoule is closely inspected to ensure that the seals are 

adequate and without defects. Any ampoule with a defective seal is opened and the solution is transferred 

to a new ampoule with an aspirating pycnometer. The new ampoule is then sealed. All sealed ampoules 

must be tested to ensure the integrity of the seal. This is performed by inverting the cooled ampoule several 

times over a wad of tissue paper and visually examining the tissue for the presence of any liquid. The tissue 

is also surveyed with a portable instrument for contamination. If the ampoule is to be opened immediately 

after sealing (e.g., as in performing a dilution), it is not required that the ampoule be smeared and further 

surveyed. All other sealed ampoules must be smeared for possible contamination. Smears of SRM 

production ampoules must be measured by RSD.

Step 14. Prepare samples for measurement.

For the gamma-ray-emitting solution radioactivity SRMs, both liquids and gases, the SRM is the sample 

for measurement.

For the alpha-particle-emitting and beta-particle-emitting radioactivity SRMs, the master solution is the 

sample for the calibration measurements. The master solution is gravimetrically dispensed to make point 

sources and/or liquid scintillation sources for measurement. In addition, some of the SRM ampoules 

(typically the first, middle, and last ampoule filled) are opened and similar sources are made to check the 

gravimetric dilution ratio between the master solution and the SRM solution. In general, the uncertainty 

associated with the direct measurement of the dilution ratio will be much larger than the uncertainty 

associated with the gravimetric measurements. The direct measurement serves as a check on any serious 

error in the gravimetric measurements, in the calculations, or in the thoroughness of mixing the solution.

See Appendix A1 for the method of preparing the measurement samples for each radioactivity SRM.

Step 15. Measure the value of each selected property as obtained directly or indirectly from a “primary 

reference measurement procedure”.

For the gamma-ray-emitting solution radioactivity SRMs, both liquids and gases, each ampoule is 

measured in the Pressurized Ionization Chamber "A" (PIC "A") and/or Auto ionization chamber (AutoIC) 

to determine the total activity of the primary radionuclide. Corrections are made for the response due to 

any other photon-emitting radionuclides present.
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See Appendix A1 for the measurement method used for each radioactivity SRM.

Step 16. Confirm each measured value using one or more confirmatory measurement methods.

Where possible, independent confirmatory measurement methods are used to verify the results from the 

primary measurement method. Comparison with samples from one or more of the previous batches of the 

same SRM is also used when such samples are available. A confirmatory method is also used to measure 

one or more of the individual radioactivity SRMs when the SRM solution is not the master solution. This 

serves as an additional check on the dispensing and/or dilution of the master solution.

See Appendix A1 for the confirmatory measurement method(s) used for each radioactivity SRM.

Step 17. Measure the homogeneity among (and possibly within) SRM units.

The homogeneity among radioactivity SRM units is usually confirmed by making measurements on 

several units within the same batch.

For gamma-ray-emitting solution radioactivity SRMs, the massic activity of the solution in each ampoule 

can be calculated from the measured activity and the measured solution mass. The massic activities are 

checked for deviant values and for correlations (such as with dispensing sequence or mass of solution).

For alpha-particle-emitting and pure beta-particle-emitting solution radioactivity SRMs, several ampoules 

(typically one of the first, middle, and last of the ampoules filled) are opened and the massic activity of 

each solution is measured. The massic activities are checked for deviant values and for correlations (such 

as with dispensing sequence).

See Appendix A1 for the homogeneity test(s) used for each radioactivity SRM.

Step 18. Establish traceability.

For solution radioactivity SRMs, the measurements include:

1. Radionuclide(s),

2. Massic Activity(ies),

3. Expanded Uncertainty(ies),

4. Reference Time,

5. Solution Mass, and

6. Solution Density (uncertified) at a reference temperature (usually 20 C).

For gas ampoules and point sources, the measurements include:

1. Radionuclide(s),

2. Total Activity(ies),

3. Expanded Uncertainty(ies), and

4. Reference Time.

The measurements made as part of the calibration of a radioactivity SRM are traceable to NIST as follows:

1. Time

Measurements of clock time are made using direct time transmissions from NIST Boulder. Counting 

time increments obtained with calibration instruments are measured by counting the number of cycles 

from temperature compensated crystal oscillators whose frequencies are measured using a frequency 

meter traceable to NIST. 
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2. Mass

Balances and scales used to measure the mass of the SRM solution (or solid) are serviced and 

calibrated at least once per year using masses (weight sets) directly traceable to NIST. 

3. Length (Volume)

Volumetric glassware used to determine the solution density is Class A glassware and is 

gravimetrically calibrated using distilled water and the well-established relationship between the 

density of pure water and the temperature.

4. Temperature / Pressure / Relative Humidity

The manufacturer’s stated accuracy for instruments used to measure temperature, pressure and relative 

humidity are sufficient.

The determination of activity requires that the number of radioactive decays that occur during a finite time 

interval be counted. The time interval can usually be chosen so as to make its uncertainty negligible. The 

difficulty lies in determining the efficiency of the detector for the radioactive decays. Every radioactivity 

detector has some intrinsic inefficiency, has a finite size (and hence boundaries), cannot detect radioactive 

decays that deposit less than some minimum amount of energy in the detector (threshold), and gives some 

count rate even in the absence of radioactive decays in the source (background count rate). The efficiency 

of a single detector (decays detected/total decays) cannot be verified without reference to one or more other 

detectors.

The efficiency of a detector has to be calculated on the basis of one or more theoretical measurement 

models, each of which has some inherent uncertainty. For radioactive decay, the theoretical measurement 

models with the lowest uncertainties are those that use multiple detectors, time correlation measurements, 

and efficiency extrapolations. (See references [4-6].) These measurement models (and the related 

measurement methods: coincidence and anticoincidence counting with efficiency-extrapolation techniques) 

cannot be used with all radionuclides or types of decay. But activity calibrations using these models and 

techniques have become the cornerstone of the international measurement system for radioactivity. The 

calibration of virtually all radioactivity measurement instruments is based upon them.

Step 19. Evaluate the uncertainty.

Measurement uncertainty is evaluated in accordance with the Guide to the Expression of Uncertainty in 

Measurement [2] and the Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement 

Results [3].

In general, the uncertainty components associated with the instruments and artifacts used to measure time, 

mass, length (volume), temperature, pressure, and relative humidity, are small and reasonably well known. 

For most radioactivity SRMs, the largest component of uncertainty arises from the uncertainty in the 

detection efficiency for the radioactive decays. The uncertainties associated with the detection efficiency 

(decays detected/total decays) vary with the type of radioactive decay, with the type of detector, and with 

the measurement method. 

See Appendix A1 for the radionuclide, the decay mode(s), the expanded uncertainty, the measurement 

method(s), and other data for each radioactivity SRM.

Step 20. Label, package, and store the SRM containers.

As part of the production process, additional packaging is placed around the container for the radioactivity

SRM. This packaging is designed to protect the SRM during handling and long-term storage. The

packaged SRMs are stored in Building 245, SRM Storage Room until shipped to the customer.

The US Department of Transportation (USDOT) and the US Nuclear Regulatory Commission (USNRC) 
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require that personnel that label and package radioactive material for shipping be certified to do so. 

USDOT certification is available through training by the NIST RSD. Shipping of Radioactive SRMs is 

covered in Procedure 19.

The Office of Reference Material (ORM) provides support services in the production and delivery of 

SRMs. These services include label research and design, SDS development for the SRMs, pricing for 

SRMs, order processing, and documentary support necessary for delivering the SRMs

Step 21. Prepare the SRM Certificate and Conduct Technical Review.

The NIST Certificate for a radioactivity SRM contains information about the composition, the properties, 

and the proper use of the SRM, and additional required information as stated in NIST-QM-I. For an 

example of previously issued certificates, see Appendix A2. 

Prior to issuance, the certificate undergoes a final technical review. The technical review must be 

approved (and signed) by the principal investigator, RG leader, the RPD chief and the SRM coordinator.

Step 22. Collect and store the production records.

The radioactivity SRM production plan, detailed descriptions of the certification methods and procedures, 

methods of validation, measurement uncertainty, and sampling plans are archived together in a three-ring 

binder. These documents and records are stored in Building 245, B50 (SRM Records Storage Room). The 

production information is retained for as long as the SRM is available for sale to the public, plus at least an 

additional 10 years.

A list of the typical contents of the Record File is presented below:

Preparatory

• Justification for SRM production. This is a simple statement as to why the SRM is being 

produced; e.g., reissue of previous one, new demand for new one and justification, etc. 

The SRM coordinator can assist in the justification. 

• Funding request to and approval from the SRM Program Office. This is largely handled 

by the SRM coordinator. 

• Approval for acquisition and use of radioactive materials by GRSD (NIST 364) or 

change to radioactive material authorization (NIST 365)

• Description of the experimental design/plans (i.e., list, table, diagrams, outline, 

flowchart, etc.), which may include measurement methods, sequence of steps to be used, 

facilities, equipment, supplies, personnel, counting source preparation details, etc.

• Production approval by SRM coordinator, including number to be produced, activity 

levels, composition, etc. 

• Purchase order for radioactive material (if necessary).

• Acquisition of material explanation (if not purchased).

Production (as applicable)

• Any relevant technical information of the material provided by the manufacturer or from 

previous production.

• Safety Data Sheet (SDS; if material presents a physical, chemical or biological hazard).

• Preparation of carrier solution data.

• Preparation of master solution or mixture data.

• Dispenser test data (if applicable).

• SRM dispensing data (if applicable).
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• Statement of SRM sterilization and independent documentation if available (e.g., 

radiation sterilization for natural matrix SRM).

• Preparation of counting sources/samples data (if applicable).

Data and Analyses (for standardization)

• Hardcopies of all original data, including all original hand-written data sheets and all 

instrument print outs.

• Notations of any equipment and instruments settings (as needed).

• Hardcopies of all data analyses records (electronic version is acceptable to include, but 

hardcopy is needed), including all analysis software output, all spreadsheets, all summary 

tables, graphs, etc.

• Any calculations performed, e.g., for corrected masses, solution composition, decay 

corrections, decay-corrected K values for appropriate RRS (see RPD Procedure 01), LS 

detection efficiencies, etc.

• Explanation of any calculation assumptions. 

• An uncertainty analysis page (including basis, assumptions, and derivations as needed).

Certification and Transfer

• Summary statement(s) – in short paragraph or tabular form-- regarding the basis for the

certified values and how they were determined. 

• Production/calibration schedule of all principal steps (from the initial design and lab set 

up through the certification) with a listing of the responsible person(s) and dates.

• All the drafts of the certificate and revisions (see NIST-QM-I for everything that the 

certificate must contain at a minimum).

• Packaging information and a sample of the SRM label.

• All packaging inserts; user notes, SDS, etc.

• Technical review sheet (signed).

• Transfer form(s) to SRM stock or inventory control. This is largely handled by the SRM 

coordinator.

Step 22. Monitoring Stability of SRMs.

The SRMs produced by RPD have indefinite periods of validity since the stability of the 

solution was a deciding factor in production (see Step 2) which means that there is no direct 

stability testing for extending expiration dates. However, the stability of the SRMs is

monitored by the use of scientific judgement, random inspection, results from interlaboratory 

comparisons, communications with customers and by establishing links between new and 

previous calibrations of the radionuclide.
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References

The calibration and/or production processes for some of the radioactivity SRMs have been published in the 

literature.

[1] International Organization for Standardization (ISO), ISO Standards Handbook - Quantities and Units, 

1993, revised by ISO 80000:2009. Available from https://www.iso.org/standard/30669.html.

(accessed Oct 2019).

[2] GUM: Guide to the Expression of Uncertainty in Measurement; JCGM 100:2008 (GUM 1995 with 

Minor Corrections); with JCGM 101:2008, JCGM104:2009, JCGM 102:2011 and JCGM 106:2012. 

Joint Committee for Guides in Metrology: BIPM, Sevres Cedex, France (2008); available at 

https://www.bipm.org/en/publications/guides/gum.html (accessed Oct 2019)

[3] Taylor, B.N.; Kuyatt, C.E.; Guidelines for Evaluating and Expressing the Uncertainty of NIST 

Measurement Results; NIST Technical Note 1297, U.S. Government Printing Office: Washington, 

DC (1994); available at http://www.nist.gov/pml/pubs/index.cfm (accessed Mar 2013).

[4] National Council on Radiation Protection and Measurements Report No. 58, A Handbook of 

Radioactivity Measurements Procedures, Second Edition, 1985. Available from the National Council 

on Radiation Protection and Measurements, 7910 Woodmont Avenue, Bethesda, MD 20814 U.S.A.

[5] International Commission on Radiation Units and Measurements (ICRU) Report 52, Particle Counting 

in Radioactivity Measurements, 1994. Available from ICRU Publications, 7910 Woodmont Avenue, 

Bethesda, MD 20814 U.S.A.

[6] W.B. Mann, A. Ritz, and A. Spernol, Radioactivity Measurements - Principles and Practice, 1991, 

Pergamon Press, Oxford.

[7] Possolo, A. Simple Guide for Evaluating and Expressing the Uncertainty of NIST Measurement Results

NIST Technical Note 1900, (2015) https://doi.org/10.6028/NIST.TN.1900.
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Appendix A1: Properties and Preparation of the NIST Radioactivity SRMs, as of October 2019.

Certified values are in bold type. Abbreviations and Notes are provided at the end of Appendix A1.

SRM Number 4222d 4226D 4233f 4239

Radionuclide C-14 Ni-63 Cs-137 Sr-90

Decay Mode(s) (>1%) BP BP BP,GR BP

Half Life 5.70 ka 100.1 a 30.05 a 28.79 a

Intended Use CAL(LSC) CAL(LSC) CAL(Ge,NaI) CAL (LSC)

Physical State Liquid Liquid Liquid Liquid

Chemical Form n-Hexadecane NiCl2 CsCl SrCl2

Solution/Mixture 

Composition

n-Hexadecane 1.2 mol·L

-1 HCl 1 mol·L-1

 HCl 1 mol·L-1 HCl

Solution/Mixture Mass (g) ~4 5.09 5.067 5.0832

Solution density (g·mL-1) 0.771 1.014 1.015 1.017

Containment 5AMP 5AMP 5NIST 5NIST

Non-radioactive Carrier None NiCl2 CsCl SrCl2; YCl3

Carrier Concentration 

(mg·L-1)

- 105 26 46; 52

Massic Activity (Bq·g

-1

) 54.01 k 85.94 k 221.1 k 31.79 k

Reference Time 10 Sep 2014 11 Nov 2009 04 Aug 2018 25 Dec 2006

Expanded Uncertainty 

(k=2) (%)

0.896 0.84 0.78 0.46

Source of Starting 

Material(s)

PUR(COM) PUR(COM) PUR(COM) PUR (COM)

Preparation of Starting 

Material(s)

None None None None

Impurity Measurement 

Method

GRS0(Ge),LSC2 GRS0&2(Ge) GRS0&2(Ge) GRSI(Ge)

Radionuclidic Impurities 

Detected

None None None None

Relative Activity of the 

Impurity

- - - -

Preparation of Master

Solution

DIL CAR,DIL CAR,DIL DIL (4234A)

Preparation of SRM 

Solution

= Master = Master = Master CAR, QDIL

Preparation of 

Measurement Samples

GRV2 GRV2 None GRV2

Measurement Model Type LMNL LMNL LMNL LMNL

Measurement Method LSC2+ET(H-3) LSC2+ET(H-3), 

CPR

PIC2(CAC) LSC 2+ET(H-3)

Confirmatory Method(s) LSC (TDCR) None None LSC (TDCR)

Homogeneity Test SEQ SEQ ALL RAN

Other Information - - - -
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Appendix A1: Properties and Preparation of the NIST Radioactivity SRMs, as of 2019.

Certified values are in bold type. Abbreviations and Notes are provided at the end of Appendix A1.

SRM Number 4251d 4274 4288B 4320b

Radionuclide Ba-133 Ho-166m Tc-99 Cm-244

Decay Mode(s) (>1%) EC, GR BP,GR BP AP

Half Life 10.52 a 1.20 ka 211 ka 18.1 a

Intended Use CAL(Ge,NaI) CAL(Ge,NaI) CAL,ENV CAL,ENV

Physical State Liquid Liquid Liquid Liquid

Chemical Form BaCl2 HoCl3 KTcO4 Cm(NO3)3

Solution/Mixture 

Composition

1 mol·L

-1 HCl 1 mol·L-1

 HCl 0.001 mol·L-1 KOH 1 M HNO3

Solution/Mixture Mass (g) 5.063 5.057 4.994 5.170

Solution density (g·mL-1) 1.015 1.016 0.997 1.033

Containment 5NIST 5NIST 5AMP 5AMP

Non-radioactive Carrier BaCl2 HoCl3 None None

Carrier Concentration 

(mg·L-1)

133 282 - -

Massic Activity (Bq·g-1) 382.6 k 19.3 k 31.55 k 35.47

Reference Time 13 Jul 2018 15 Feb 2006 01 May 2008 01 Sep 2011

Expanded Uncertainty 

(k=2) (%)

1.2 0.81 to 2.4 0.66 1.4

Source of Starting 

Material(s)

PUR (COM) PUR(USDOE) PUR(USDOE) PUR(USDOE)

Preparation of Starting 

Material(s)

None None None SEP

Impurity Measurement 

Method

GRS0&2(Ge GRS0&2(Ge) GRS0&2(Ge) GRS0(Ge),APS2

Radionuclidic Impurities 

Detected

None Tm-170 None Pu-240;Cm-243, 

Cm-245

Relative Activity of the 

Impurity

- - - 1.E-2;3.E-4; 8.E5

Preparation of Master 

Solution

DIL DIL DIL DIL

Preparation of SRM

Solution

CAR, QDIL = Master = Master = Master

Preparation of 

Measurement Samples

GRV2, QDIL None GRV2 GRV1

Measurement Model Type LMNL LMNL LMNL LMNL

Measurement Method LSC(CAC) GRS(Ge) LSC 2+ET(H-3) LSC1

Confirmatory Method(s) LSC 2+ET(H3), 

LSC(TDCR),

PIC (CAC)

PIC2(CAC) CAC+ET(Co-60), 

LSC(TDCR), CPR

GRS(Ge)

Homogeneity Test ALL ALL SEQ RAN

Other Information - - - -
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Appendix A1: Properties and Preparation of the NIST Radioactivity SRMs, as of October 2019.

Certified values are in bold type. Abbreviations and Notes are provided at the end of Appendix A1.

SRM Number 4321d 4322d 4323c 4324B

Radionuclide U-NAT Am-241 Pu-238 U-232

Decay Mode(s) (>1%) AP AP,GR AP AP

Half Life 4.468 Ga 432.6 a 87.74 a 68.9 a

Intended Use CAL,ENV CAL,ENV CAL,ENV CAL,ENV

Physical State Liquid Liquid Liquid Liquid

Chemical Form UO2(NO3)2 Am(NO3)3 Pu(NO3)6 UO2(NO3)2

Solution/Mixture 

Composition

1 mol·L-1 HNO3 1 mol·L-1 HNO3 3 mol·L-1 HNO3 2 mol·L-1

HNO3

Solution/Mixture Mass (g) 5.284 5.14 5.511 5.321

Solution density (g·mL-1) 1.057 1.032 1.102 1.064

Containment 5AMP 5AMP 5AMP 5NIST

Non-radioactive Carrier None None None None

Carrier Concentration (mg·L1

)

- - - -

Massic Activity (Bq·g-1) 459.63 (Total) 133.7 22.73 38.22

Reference Time 15 Mar 2017 01 Mar 2019 11 Oct 2016 01 Jul 2002

Expanded Uncertainty (k=2) 

(%)

1.07 0.32 0.50 0.80

Source of Starting Material(s) PUR(USDOE) PUR(COM) PUR(USDOE) PUR(COM)

Preparation of Starting 

Material(s)

DSS None DSS None

Impurity Measurement 

Method

GRS1(Ge),APS2 GRS0(Ge) GRS0(Ge),APS2 GRS0(Ge),APS

1

Radionuclidic Impurities 

Detected

None None None None

Relative Activity of the 

Impurity

- - - -

Preparation of Master 

Solution

QDIL DIL DIL None

Preparation of SRM Solution QDIL QDIL QDIL QDIL

Preparation of Measurement 

Samples

GRV1 GRV1 GRV1 GRV1

Measurement Model Type LMNL LMNL LMNL LMNL

Measurement Method WTR0,MS2 LSC1 LSC1 CAC

Confirmatory Method(s) LSC2, APS None APS PIC1(THE),CP

R

Homogeneity Test ALL RAN SEQ SEQ

Other Information - - - -
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Appendix A1: Properties and Preparation of the NIST Radioactivity SRMs, as of October 2019.

Certified values are in bold type. Abbreviations and Notes are provided at the end of Appendix A1.

SRM Number 4326A 4328C 4329a 4330C

Radionuclide Po-209 Th-229 Cm-243 Pu-239

Decay Mode(s) (>1%) AP AP,GR AP,GR AP

Half Life 125.2 a 7.340 ka 28.9 a 24.110 ka

Intended Use CAL,ENV CAL,ENV CAL,ENV CAL,ENV

Physical State Liquid Liquid Liquid Liquid

Chemical Form PoCl4 Th(NO3)4 Cm(NO3)3 Pu(NO3)6

Solution/Mixture 

Composition

2 mol·L-1 HCl 1.1 mol·L

-1

HNO3

1 mol·L-1 HNO3 3.4 mol·L-1

HNO3

Solution/Mixture Mass (g) 5.169 5.1791 5.156 2.7707

Solution density (g·mL-1) 1.032 1.036 Not given 1.1082

Containment 5AMP 5NIST 5AMP 5AMP

Non-radioactive Carrier None None None None

Carrier Concentration 

(mg·L-1)

- - - -

Massic Activity (Bq·g-1) 39.01 35.29 30.54 38.41

Reference Time 1 Dec 2013 31 Dec 2007 15 May 2019 1 May 2009

Expanded Uncertainty 

(k=2) (%)

0.46 0.60 0.20 0.46

Source of Starting 

Material(s)

PUR(COM) PUR(USDOE) PUR(USDOE) PUR(USDOE)

Preparation of Starting 

Material(s)

None DSS DSS DSS

Impurity Measurement 

Method

GRS0(Ge),APS1 GRS0(Ge) GRS0(Ge),APS2 GRS0(Ge),APS2

Radionuclidic Impurities 

Detected

None None Am-243;Cm-244 None

Relative Activity of the 

Impurity

- - In preparation -

Preparation of Master 

Solution

DIL DIL DIL DIL

Preparation of SRM 

Solution

QDIL QDIL = Master QDIL

Preparation of 

Measurement Samples

GRV1 GRV1 GRV1 GRV1

Measurement Model Type LMNL LMNL LMNL LMNL

Measurement Method LSC1 CAC1&2 LSC LSC1

Confirmatory Method(s) GCE1,SB1 LSC2+ET(H-3), 

LSC(TDCR),SB

2, APS, CPR

None CPR

Homogeneity Test SEQ SEQ None RAN

Other Information - - - -
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Appendix A1: Properties and Preparation of the NIST Radioactivity SRMs, as of October 2019.

Certified values are in bold type. Abbreviations and Notes are provided at the end of Appendix A1.

SRM Number 4332E 4334j 4337 4338A

Radionuclide Am-243 Pu-242 Pb-210 Pu-240

Decay Mode(s) (>1%) AP,GR AP BP,GR AP

Half Life 7.370 ka 373.5 ka 22.2 a 6.564 ka

Intended Use CAL,ENV CAL,ENV CAL,ENV CAL,ENV

Physical State Liquid Liquid Liquid Liquid

Chemical Form Am(NO3)3 Pu(NO3)6 Pb(NO3)2 Pu(NO3)6

Solution/Mixture 

Composition

1.1 mol·L-1

HNO3

3.1 mol·L-1

HNO3

1 mol·L-1 HNO3 2.8 mol·L-1

HNO3

Solution/Mixture Mass (g) 5.1713 5.499 5.133 5.471

Solution density (g·mL-1) 1.035 1.1099 1.028 1.091

Containment 5AMP 5AMP 5NIST 5AMP

Non-radioactive Carrier None None Pb(NO3)2, 

Bi(NO3)3,

None

Carrier Concentration 

(mg·L-1)

- - 17, 39 -

Massic Activity (Bq·g-1) 38.49 26.08 9.037 k 40.88

Reference Time 1 Oct 2008 09 Aug 2017 15 June 2006 01 May 1996

Expanded Uncertainty 

(k=2) (%)

0.90 0.51 2.4 0.76

Source of Starting 

Material(s)

PUR(COM) PUR(USDOE) PUR(COM) PUR(USDOE)

Preparation of Starting 

Material(s)

None DSS None DSS

Impurity Measurement 

Method

GRS0(Ge) GRS1(Ge),APS

2

GRS0&2(Ge) GRS0(Ge),APS

2

Radionuclidic Impurities 

Detected

None Pu-241; Am241None Pu-238;Am-241

Relative Activity of the 

Impurity

- 1.5E-3;8E-5 - 9.E-3;2.E-4

Preparation of Master 

Solution

DIL DIL DIL DIL

Preparation of SRM 

Solution

QDIL QDIL QDIL QDIL

Preparation of 

Measurement Samples

GRV1 GRV1 GRV1 GRV1

Measurement Model Type LMNL LMNL LMNL LMNL

Measurement Method LSC2+ET(H-3) LSC1 LSC2+ET(H-3) DSA1,LSC1

Confirmatory Method(s) CPR LSC2 GRS2(Ge) LSC2

Homogeneity Test SEQ SEQ RAN SEQ

Other Information - - - -
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Appendix A1: Properties and Preparation of the NIST Radioactivity SRMs, as of October 2019.

Certified values are in bold type. Abbreviations and Notes are provided at the end of Appendix A1.

SRM Number 4339B 4340B 4341A 4342A

Radionuclide Ra-228 Pu-241 Np-237 Th-230

Decay Mode(s) (>1%) BP BP AP,GR AP

Half Life 5.75 a 14.33 a 2.14 Ma 75.38 ka

Intended Use CAL,ENV CAL,ENV CAL,ENV CAL,ENV

Physical State Liquid Liquid Liquid Liquid

Chemical Form Ra(NO3)2 Pu(NO3)6 Np(NO3)3 Th(NO3)4

Solution/Mixture 

Composition

1.3 mol·L-1

HNO3

2.8 mol·L-1

HNO3

2 mol·L-1 HNO3 1.0 mol·L-1

HNO3

Solution/Mixture Mass (g) 5.180 5.5050 5.320 5.1626

Solution density (g·mL-1) 1.034 1.087 1.067 1.032

Containment 5NIST 5AMP 5AMP 5NIST

Non-radioactive Carrier Ba(NO3)2 None None None

Carrier Concentration 

(mg·L-1)

19.8 - - -

Massic Activity (Bq·g-1) 195 258.5 152.3 40.83

Reference Time 7 Oct 2010 15 June 2007 1 Sep 2012 1 Apr 2007

Expanded Uncertainty 

(k=2) (%)

7.2 3.8 0.94 0.38

Source of Starting

Material(s)

DON(NIST) PUR(COM) PUR(USDOE) PUR(USDOE)

Preparation of Starting 

Material(s)

DSS,SEP None DSS DSS,SEP

Impurity Measurement 

Method

GRS1(Ge) GRS1(Ge); APS GRS0(Ge),APS1 GRS1,MS0

Radionuclidic Impurities 

Detected

Ra-226; Th232Am-241;Pu239+240; Pu238, Pu-242Total Alpha Th-229;Th-232

Relative Activity of the 

Impurity

2.6E-3; 4E-4 8.8E-4; 4E4;1.6E-4;7.7E-69.9E-6 4E-4;6E-7

Preparation of Master 

Solution

DIL DIL DIL DIL

Preparation of SRM 

Solution

QDIL QDIL QDIL QDIL

Preparation of 

Measurement Samples

GRV1&2 GRV1 GRV1 GRV1

Measurement Model Type LMNL LMNL LMNL LMNL

Measurement Method GRS(Ge) LSC2+ET(H-3) LSC LSC1

Confirmatory Method(s) APS( LSC2(TDCR) CAC & Ge SB2

Homogeneity Test RAN RAN RAN RAN

Other Information - - - -
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Appendix A1: Properties and Preparation of the NIST Radioactivity SRMs, as of October 2019.

Certified values are in bold type. Abbreviations and Notes are provided at the end of Appendix A1.

SRM Number 4361C 4370d 4401L # 4404L #

Radionuclide H-3 Eu-152 I-131 Tl-201

Decay Mode(s) (>1%) BP BP,EC,GR BP,GR EC,GR

Half Life 12.312 a 13.517 a 8.02070 d 72.912 h

Intended Use HYD CAL(Ge,NaI) CAL,NM CAL,NM

Physical State Liquid Liquid Liquid Liquid

Chemical Form H2O EuCl3 KI TlNO3

Solution/Mixture 

Composition

H2O 1 mol·L-1 HCl 0.007 mol·L-1

LiOH+

1.2 mol·L-1

HNO3

Solution/Mixture Mass (g) ~500 5.0338 4.9744* 5.2051*

Solution density (g·Ml-1) 0.998 Not given 0.999 1.040

Containment 500GB 5NIST 5NIST 5NIST

Non-radioactive Carrier None EuCl3 KI TlNO3

Carrier Concentration

(mg·L-1)

- 277 70 100

Massic Activity (Bq·g-1) 2.009 18.70 k 5.365 M 5.858 M

Reference Time 03 Sep 1998 19 Jul 2018 every Jan every Apr

Expanded Uncertainty 

(k=2) (%)

0.76 1.2 0.70 0.80

Source of Starting

Material(s)

PUR(COM) PUR(USDOE) PUR(COM) PUR(COM)

Preparation of Starting 

Material(s)

None None None None

Impurity Measurement 

Method

GRS0(Ge),BPS

1

GRS1(Ge) GRS1&2(Ge) GRS1&2(Ge)

Radionuclidic Impurities 

Detected

None Eu-154 None Tl-200;Tl-202

Relative Activity of the 

Impurity

- 1.2E-3 - 2.E-3;2.E-3

Preparation of Master 

Solution

= 4926E CAR,DIL = 4401H = 4404H

Preparation of SRM 

Solution

QDIL = Master CAR,QDIL CAR,QDIL

Preparation of 

Measurement Samples

GRV2 None None None

Measurement Model Type LMNL LMNL LMNL LMNL

Measurement Method GCI PIC1(CPD) PIC1&2(CAC) PIC1&2(CAC)

Confirmatory Method(s) LSC2 CPD2(Ge) CDP2(Ge) CPD2(Ge)

Homogeneity Test SEQ ALL ALL ALL

Other Information [d] - - -
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Appendix A1: Properties and Preparation of the NIST Radioactivity SRMs, as of October 2019.

Certified values are in bold type. Abbreviations and Notes are provided at the end of Appendix A1.

SRM Number 4406L # 4407L # 4410H # 4412L #

Radionuclide P-32 I-125 Tc-99m Mo-99

Decay Mode(s) (>1%) BP EC,GR IT,GR BP,GR

Half Life 12.284 d 59.400 d 6.01 h 65.94 h

Intended Use CAL,NM CAL,NM CAL,NM CAL,NM

Physical State Liquid Liquid Liquid Liquid

Chemical Form H3PO4 KI NaTcO4 Na2MoO4

Solution/Mixture 

Composition

0.06 mol·L-1

H3PO4

0.01 mol·L-1

LiOH

0.16 mol·L-1 

NaCl

3.1 mol·L-1 

HNO3

Solution/Mixture Mass (g) 5.1459* 4.9608* 4.9865* 5.5053*

Solution density (g·Ml-1) 1.001 0.999 1.005 1.102

Containment 5NIST 5NIST 5NIST 5NIST

Non-radioactive Carrier None KI None Na2MoO4

Carrier Concentration 

(mg·L-1)

- 60 - 90

Massic Activity (Bq·g-1) 3.6 M 1.433 M 1.408 G 15.22 M

Reference Time every Apr every Nov every Aug every Feb

Expanded Uncertainty 

(k=2) (%)

0.42 0.78 0.64 0.72

Source of Starting 

Material(s)

PUR(COM) PUR(COM) PUR(COM) PUR(COM)

Preparation of Starting 

Material(s)

None None None None

Impurity Measurement 

Method

GRS2(Ge) GRS1&2(Ge) GRS2(Ge) GRS1&2(Ge)

Radionuclidic Impurities 

Detected

None None Mo-99 None

Relative Activity of the 

Impurity

- 1.E-6 -

Preparation of Master 

Solution

DIL = 4407H DIL = 4412H

Preparation of SRM 

Solution

= Master CAR,QDIL = Master CAR,QDIL

Preparation of 

Measurement Samples

GRV2 GRV2 None None

Measurement Model Type LMNL LMNL LMNL LMNL

Measurement Method LSC SPC PIC1(CAC) PIC1&2(CAC)

Confirmatory Method(s) None CDP2(Ge) CPD2(Ge) CDP2(Ge)

Homogeneity Test RAN ALL ALL ALL

Other Information - - -
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Appendix A1: Properties and Preparation of the NIST Radioactivity SRMs, as of October 2019.

Certified values are in bold type. Abbreviations and Notes are provided at the end of Appendix A1.

SRM Number 4415L # 4416L # 4417L # 4427L #

Radionuclide Xe-133 Ga-67 In-111 Y-90

Decay Mode(s) (>1%) BP,GR EC,GR EC,GR BP

Half Life 5.243 d 3.2612 d 2.8047 d 64.0 h

Intended Use CAL,NM CAL,NM CAL,NM CAL,NM

Physical State Gas Liquid Liquid Liquid

Chemical Form Xe GaCl3 InCl3 YCl3

Solution/Mixture 

Composition

Xe 2 mol·L-1 HCl 3.2 mol·L-1 HCl 1.1 mol·L-1 HCl

Solution/Mixture Mass (g) ~7 mg total 5.1523* 5.265* 5.0844*

Solution density (g·mL-1) ~25 Kpa 1.033 1.053 1.017

Containment 5GAS 5NIST 5NIST 5NIST

Non-radioactive Carrier None GaCl3 InCl3 YCl3

Carrier Concentration 

(mg·L-1)

800 60 50

Massic Activity (Bq·g-1) 563.8 M total* 4.688 M 6.224 M 5.731 M

Reference Time every Sep every May every Jul every Oct

Expanded Uncertainty 

(k=2) (%)

0.78 0.60 0.54 0.72

Source of Starting 

Material(s)

PUR(COM) PUR(COM) PUR(COM) PUR(COM)

Preparation of Starting 

Material(s)

None None None None

Impurity Measurement 

Method

GRS1&2(Ge) GRS1&2(Ge) GRS1&2(Ge) GRS1&2(Ge)

Radionuclidic Impurities 

Detected

Kr-85;Xe131mNone In-114m Sr-90

Relative Activity of the 

Impurity

5.E-6;1.5E-2 - 3.E-4 7.E-8

Preparation of Master 

Solution

= 4415H = 4416H = 4417H = 4427H

Preparation of SRM 

Solution

CAR,QDIL CAR,QDIL CAR,QDIL CAR,QDIL

Preparation of

Measurement Samples

None None None GRV2

Measurement Model Type LMNL LMNL LMNL LMNL

Measurement Method PIC1&2(GCI) PIC1&2(CAC) PIC1&2(CAC) LSC2

Confirmatory Method(s) CPD2(Ge) CDP2(Ge) CPD2(Ge) PIC2(LSC)

Homogeneity Test Not applicable ALL ALL ALL

Other Information - - - -
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Appendix A1: Properties and Preparation of the NIST Radioactivity SRMs, as of October 2019.

Certified values are in bold type. Abbreviations and Notes are provided at the end of Appendix A1.

SRM Number 4915F 4919I 4926E 4927G

Radionuclide Co-60 Sr-90 H-3 H-3

Decay Mode(s) (>1%) BP,GR BP BP BP

Half Life 1925.28 d 28.80 a 12.312 a 12.32 a

Intended Use CAL(Ge,NaI) CAL(LSC) CAL(LSC),HYD CAL(LSC)

Physical State Liquid Liquid Liquid Liquid

Chemical Form CoCl2 SrCl2 H2O H2O

Solution/Mixture 

Composition

1.1 mol·L-1

HCl

1.0 mol·L-1 HCl H2O H2O

Solution/Mixture Mass (g) 5.0595 5.0790 ~20 4.99

Solution density (g·mL-1) 1.017 1.017 0.998 0.998

Containment 5NIST 5AMP 20SERUM 5AMP

Non-radioactive Carrier CoCl2 SrCl2;YCl3 None None

Carrier Concentration 

(mg·L-1)

130 36;50 - -

Massic Activity (Bq·g-1) 58.29 k 4.261 k 5.038 k 544.2 k

Reference Time 01 Nov 2005 25 Dec 2006 03 Sep 1998 01 May 2015

Expanded Uncertainty 

(k=2) (%)

0.5 0.48 0.72 0.96

Source of Starting 

Material(s)

PUR(COM) PUR(COM) PUR(COM) PUR(COM)

Preparation of Starting 

Material(s)

None None None None

Impurity Measurement 

Method

GRS2(Ge) GRS1(Ge) GRS0(Ge),BPS0 GRS0(Ge),BPS1

Radionuclidic Impurities 

Detected

Co-57 None None None

Relative Activity of the 

Impurity

3.8E-5 - - -

Preparation of Master 

Solution

CAR,DIL DIL(4234A) =4927F DIL

Preparation of SRM 

Solution

= Master CAR,QDIL QDIL =Master

Preparation of 

Measurement Samples

None GRV2 GRV2 GRV2

Measurement Model Type LMNL LMNL LMNL LMNL

Measurement Method PIC2(CAC) LSC2+ET(H-3) GCI1 GCI2

Confirmatory Method(s) None LSC(TDCR) LSC2 LSC2

Homogeneity Test ALL RAN SEQ SEQ

Other Information - - - -
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Appendix A1: Properties and Preparation of the NIST Radioactivity SRMs, as of October 2019.

Certified values are in bold type. Abbreviations and Notes are provided at the end of Appendix A1.

SRM Number 4929F 4943 4949D 4965

Radionuclide Fe-55 Cl-36 I-129 Ra-226

Decay Mode(s) (>1%) EC BP,EC BP,GR AP,GR

Half Life 2.737 a 301 ka 15.7 Ma 1.600 ka

Intended Use CAL(LSC),EN

V

CAL(LSC),ENV ENV,CAL(LSC) CAL,ENV

Physical State Liquid Liquid Liquid Liquid

Chemical Form FeCl3 NaCl NaI RaCl2

Solution/Mixture 

Composition

1 mol·L-1 HCl H2O 0.01 mol·L-1

NaOH + 0.007 

mol·L-1 Na2SO3

1.4 mol·L-1 HCl

Solution/Mixture Mass (g) 5.080 ~3 5.005 5.098

Solution density (g·mL-1) 1.014 Not given 0.999 1.019

Containment 5AMP 5AMP 5AMP 5NIST

Non-radioactive Carrier FeCl2 NaCl None BaCl2

Carrier Concentration 

(mg·L-1)

56 200 - 1700

Massic Activity (Bq·g-1) 58.43 k 10.95 k 2.747 k 30.99

Reference Time 30 Nov 2005 Dec 1984 01 Jan 2014 09 Sep 1991

Expanded Uncertainty 

(k=2) (%)

1.7 0.82 1.08 1.23

Source of Starting 

Material(s)

PUR(COM) PUR(COM) PUR(COM) PUR(COM)

Preparation of Starting 

Material(s)

None None None None

Impurity Measurement 

Method

GRS1&2(Ge) GRS0(Ge),BPS2 GRS1(Ge),BPS2 GRS0&1(Ge)

Radionuclidic Impurities 

Detected

None None None None

Relative Activity of the 

Impurity

- - - -

Preparation of Master 

Solution

CAR,DIL DIL DIL CAR,QDIL

Preparation of SRM 

Solution

CAR,QDIL =Master CAR,QDIL CAR,QDIL

Preparation of 

Measurement Samples

GRV2 GRV2 GRV2 GRV2

Measurement Model Type LMNL LMNL LMNL LMNL

Measurement Method MC GCE1 CAC1 WTR0

Confirmatory Method(s) LSC2, CPR LSC2 TDCR, GRS(Ge) LSC2

Homogeneity Test RAN SEQ RAN PIC2,CPD2

Other Information - - - -
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Appendix A1: Properties and Preparation of the NIST Radioactivity SRMs, as of October 2019.

Certified values are in bold type. Abbreviations and Notes are provided at the end of Appendix A1.

SRM Number 4966A 4967A 4969 4990C

Radionuclide Ra-226 Ra-226 Ra-226 C-14

Decay Mode(s) (>1%) AP,GR AP,GR AP,GR BP

Half Life 1.600 ka 1.600 ka 1.600 ka 5.70 ka

Intended Use CAL,ENV CAL,ENV CAL,ENV C14

Physical State Liquid Liquid Liquid Solid

Chemical Form RaCl2 RaCl2 RaCl2 Oxalic Acid

Solution/Mixture 

Composition

1 mol·L-1 HCl 1 mol·L

-1 HCl 1.5 mol·L-1 HCl Powder

Solution/Mixture Mass (g) 5.085 5.086 5.122 28 x 8

Solution density (g·mL-1) 1.017 1.017 1.024 -

Containment 5NIST 5NIST 5NIST 60JAR x 8

Non-radioactive Carrier BaCl2 BaCl2 BaCl2 None

Carrier Concentration 

(mg·L-1)

6376 80 100 -

Massic Activity (Bq·g-1) 287.6 2.482 k 3.047 0.008

Reference Time 0 Jan 2007 01 Sep 2003 15 Sep 1998 1980

Expanded Uncertainty 

(k=2) (%)

1.3 1.20 1.8 1.6

Source of Starting 

Material(s)

PUR(COM) PUR(COM) PUR(COM) PUR(COM)

Preparation of Starting 

Material(s)

None None None None

Impurity Measurement 

Method

GRS0&1(Ge) GRS0&1(Ge) GRS0&1(Ge) GRS0(Ge)

Radionuclidic Impurities 

Detected

None None None None

Relative Activity of the 

Impurity

- - - -

Preparation of Master 

Solution

CAR,QDIL CAR,QDIL CAR,QDIL OA

Preparation of SRM 

Solution

CAR,QDIL CAR,QDIL CAR,QDIL OA

Preparation of 

Measurement Samples

GRV2 GRV2 GRV2 OA

Measurement Model Type LMNL LMNL LMNL LMNL

Measurement Method RPIC WTR0 WTR0 GCI2

Confirmatory Method(s) GRS1(Ge), 

GRS1(NaI)

LSC2 LSC2 LSC2

Homogeneity Test PIC2,CPD2 PIC2,CPD2 PIC2,CPD2 RAN

Other Information - - - [[a],[b]
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ABBREVIATIONS AND ACRONYMS

General

* = Representative value; each unit is individually measured and certified.

+ = Solution also contains other components. See the SRM Certificate for more information.

# = Short-lived SRMs 

Decay Modes

AP = Alpha-Particle emission

BP = Beta-Particle emission

EC = Electron Capture

GR = Gamma-Ray emission

IT = Internal Transition

Intended Use

AMS = Accelerator Mass Spectrometry

CAL( ) = Calibration of instruments ( ) and procedures

C14 = Carbon-14 dating measurements

ENV = Environmental measurements

GEO = Geological and geochronological measurements

HYD = Hydrological measurements

NM = Nuclear Medicine

Containment 

20SERUM = 20 mL glass serum vial

500GB = 500 mL glass bottle

5AMP = 5 mL borosilicate glass ampoule

5GAS = 5 ml gas ampoule [c]

5NIST = 5 mL NIST glass ampoule

60JAR = 60 mL glass jar

Source of Starting Material 

COM = Commercial supplier

DON ( ) = Donated by ( )

IAEA = International Atomic Energy Agency

PUR ( ) = Purchased from ( )

USDOE = United States Department of Energy

Preparation of Starting Material(s) 

DSS = Dissolution of solid material(s)

SEP = Radiochemical Separation / Purification

Measurement Methods 

0 = Starting material

1 = Material from the Master Solution

2 = Material from the SRM container

AC = Atom Counting

APS = Alpha-particle Spectrometry

BPS = Beta-particle Spectrometry
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CAC = Coincidence/Anticoincidence Counting

CPD( ) = Calibrated Photon Detection System (Ge, NaI, etc.)

CPR = Compared with previous RSRM

DSA = Defined Solid Angle Counting

ET( ) = Efficiency Tracing using ( ) as the tracing radionuclide

GCE = Gas Counting (External)

GCI = Gas Counting (Internal)

Ge = Germanium photon detector

GRS( ) = Gamma-ray Spectrometry using ( )

LSC = Liquid Scintillation Counting

MC = Microcalorimetry

MS = Mass Spectrometry

NaI = Sodium Iodide photon detector

OA = Other Agency. Distributed but not certified by NIST.

PIC( ) = Ionization Chamber calibrated using ( )

RPIC = Pulse Ionization Chamber for Radon Measurements

SB = Surface Barrier alpha-particle detector

SPC = Sum-Peak Counting

TDCR = Triple-to-Double Coincidence Ratio

THE = Theoretically Computed

WTR = Weight of Radionuclide

Preparation of Solutions/Mixtures 

BL = Blending

CAR = Addition of non-radioactive carrier

DIL = Dilution

DIL5 = Dilution to (5.0 ± 0.1) mL in a 5 mL NIST ampoule

QDIL = Quantitative dilution

Preparation of Measurement Samples 

0 = Starting material

1 = Material from the Master Solution

2 = Material from the SRM container

DIL5 = Dilution to (5.0 ± 0.1) mL in a 5 mL NIST ampoule

GRV = Dispense by mass

QDIL = Quantitative dilution

Measurement Models 

LMNL = Linear, Multiplicative, Normal Distribution, Low Correlation

LMNH = Linear, Multiplicative, Normal Distribution, High Correlation

LMOL = Linear, Multiplicative, Other than Normal Distribution, Low Correlation

NMNL = Non-Linear, Multiplicative, Normal Distribution, Low Correlation

Homogeneity Test 

ALL = Measure every SRM dispensed

SEQ = Measure sequential samples of the SRM (typically the first, some of the middle, and the last 

dispensed)

RAN = Measure SRMs randomly selected out of the total dispensed

Other Information

[letter] = Note
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[number] = Reference

NOTES

[a] SRM 4990C replaces SRM 4990, which has been in use in radiocarbon dating laboratories since 1958. 

The material is part of a 450 kg lot of oxalic acid that was prepared by fermentation of French beet 

molasses from the 1977 spring, summer, and fall harvests. The ratio of the massic activity of SRM 4990C 

to that of SRM 4990, and the isotopic ratios of carbon-13 to carbon-12 in each, were measured by eleven 

international carbon dating laboratories in an intercomparison organized by L.M. Cavallo and W.B. Mann. 

See Proceedings of the 11th International Radiocarbon Dating Conference, M. Stuiver and R. Kra, Editors, 

Radiocarbon 25, No. 2 (1983).

[b] This standard is not radioactive material for licensing or shipping purposes.

[c] Flame-sealed borosilicate glass ampoule with an outside diameter of 1.5 cm and a length of 4.5 cm.
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AppendixA2.
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