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Purpose

The purpose of this procedure is to describe the measurement and reporting procedures for beta- and alphaparticle emitting radionuclides by liquid scintillation (LS) counting.

Scope

The procedures covered here include: (i) preparation of LS counting sources; (ii) comparative LS calibrations 

of submitted radionuclide solutions against NIST standards; (iii) efficiency tracing of beta emitters using the 

CIEMAT/NIST methodology with tritium (3H) standards as the LS efficiency monitor; (iv) 4παβ LS calibrations 

for alpha emitters or alpha-beta decay chains; and (v) Triple-to-Double Coincidence Ratio (TDCR) Counting.

Scheduled calibration services for submitted samples of radionuclides that are to be measured by LS counting 

are offered as a complement to Standard Reference Materials. Customers must initially contact NIST 

Radioactivity Group as to whether the radionuclide or sample composition is suitable for measurement by LS 

counting. 

Many radionuclides can be calibrated by more than one measurement service, e.g., by high-resolution gamma 

ray spectrometry, or re-entrant ionization chamber measurements, or LS counting. Calibrations by LS counting 

are very labor intensive. As a result, in general, if it is possible to perform the calibration by ion chamber 

measurements the calibration services 43010c (half-lives longer than 15 days) or 43020c (half-lives shorter

than 15 days) will be used rather than an LS calibration service. Radionuclides most suitably calibrated by LS 

calibration services are pure beta emitters with no significant gamma ray emissions, e.g., 3H, 14C, 32P, 36Cl, 63Ni,

89Sr, 90Y, 204Tl. 

There are stringent limitations on the physical and chemical form and activity range of sources that can be 

accepted. To ensure that these specifications are understood, it is essential that there be good communication 

between the technical user and the technical contact at NIST.

Two general requirements apply to all sources submitted for calibration: (1) all shipments must conform to 

applicable Nuclear Regulatory Commission (NRC) and Department of Transportation (DOT) packaging and 

transport; and (2) source descriptions, including approximate activity, must be provided in advance. The NIST 

Radiation Safety Division (RSD) must approve the receipt of radioactive material, and sources may be refused 

if the necessary information is not available. Copies of regulations may be obtained from Operations Division,

Office of Hazardous Materials, Department of Transportation, Washington, DC 20950. Postal regulations 

prohibit the mailing of radioactive materials that require a caution label under DOT regulations.
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All sources arriving at NIST are checked by the RSD for radiation level and source integrity. Sources should be 

shipped to the attention of the technical contact at NIST.

Definitions

Liquid Scintillation (LS) Counting

LS counting is the measurement of radioactivity of a sample which utilizes the technique of intimately mixing 

the active material with a liquid scintillator to form a LS cocktail and counting the resultant photon emissions.

It allows more efficient counting because of the 4 detection geometry.

LS Cocktail

An LS cocktail is the counting source used for LS measurements. It is typically contained in a 20 mL glass or 

plastic, screw-capped LS vial and consists of an organic-based commercial scintillation fluid (composed of an 

organic solvent with solutes of a scintillant and surfactant materials), a small aliquot of a radioactive solution 

(commonly a dilute acid with carrier ions, though occasionally an alkaline solution), and a carrier solution or 

water to increase the aqueous fraction in the cocktail. 

CIEMAT/NIST

CIEMAT/NIST is an acronym for Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas and 

the National Institute of Standards and Technology, which are the respective national standards laboratory of 

Spain and the United States. Researchers from the two institutions collaboratively developed the efficiency 

tracing method which bears the names of those laboratories.

Equipment and Supplies

Certain commercial equipment, instruments, or materials are identified in this document to foster 

understanding. Such identification does not imply recommendation or endorsement by the National Institute 

of Standards and Technology, nor does it imply that the materials or equipment identified are necessarily the 

best available for the purpose.

The LS counters available for the measurements are: (1) PerkinElmer Tri-Carb 4910TR; (2) Beckman Coulter 

LS6500; (3) Hitachi Aloka AccuFlex LSC-8000; (4) Perkin Elmer Quantulus Ultra Low-Level LS Spectrometer 1220; 

(5) NIST Triple-to-Double Coincidence Ratio Counter.

LS vials used to prepare the counting sources are screw-capped glass or plastic. 
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Commercially prepared scintillation fluids used to prepare LS counting sources are environmentally safe. They 

include UltimaGold, UltimaGold AB, InstaGel, OptiFluor (PerkinElmer) amongst others.

Information about safe packaging, labeling and disposing of liquid scintillation vials and fluid can be found 

here. https://www.ehs.washington.edu/system/files/resources/Liquid_Scintillation_Fluid_Focus_Sheet.pdf

Chemical laboratory equipment needed to prepare the LS counting sources includes scintillation fluid 

dispensing bottles, aspirating pycnometers, an analytical balance (capacity 200g and readability down to 

0.0001 g), a microbalance (capacity 40 g and readability down to 0.000001 g), and suitable carrier solutions to 

adjust aqueous fraction. 

Radiation Safety 

Radiation safety training and assessment services are provided by the RSD. The laboratories used for 

preparation of LS counting sources and the room used for LS counting are designated as a Radiation Facility.

LS sources to be measured must be checked and be found to be free of any external radioactive contamination 

before being loaded into the LS counters.

Procedures

Preparation of LS Counting Sources

In general, standardization measurements utilize more than one scintillation fluid, and typically a series of 6 or 

more counting sources are made for each scintillation fluid. For comparative measurements against a known 

standard the composition of the cocktails for both the sample solution and standard must be closely matched, 

and all sources shall be essentially identical in composition. For counting sources with variable chemical 

quenching as used for 3H standard efficiency tracing, the 3H standard counting sources are closely matched in 

terms of chemical composition to the sample counting sources. The two series of sources (sample series and 

3H series) are identical except for the amount of imposed quenching agent used to vary the quenching. This is 

done to ensure that there is only one quenching variable (the imposed quench agent). In general, all sources 

are prepared gravimetrically, however, mass determinations of bulk components are not always required. 

When very close matching is critical and required, an analytical balance is used for weighing the bulk 

components. Radioactive solutions are weighed with a microbalance using the aspirating pycnometer method. 

The preparation steps are as follows:

1. Each of the series of LS vials are filled with approximately 10 mL of a suitable scintillation fluid from a 

dispensing bottle.
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2. The aqueous fraction in each vial is adjusted to about 0.06 or greater by adding carrier solution with a 

pycnometer or syringe.

3. For a quench-varied series, varying amounts of the imposed quench agent (typically a 1:3 ratio of 

nitromethane in ethanol) is added dropwise with a pycnometer to the series of vials.

4. The radioactive sample vessel (either a flame-sealed glass ampoule or a crimp-sealed glass vial) is 

opened and the solution is aspirated into a pycnometer.

5. The pycnometer is placed on the microbalance and weighed.

6. A quantity, generally in the range of 15 mg to 100 mg, is dispensed into one of the LS vials, and the 

pycnometer is reweighed to determine the dispensed mass of radioactive solution. The pycnometer

mass is recorded at every step. Buoyancy correction due to air displacement is applied to all mass 

measurements done.

7. The procedure is repeated until all LS vials are filled. Any remaining radioactive solution is then 

transferred to an empty ampoule. The empty pycnometer is weighed one last time and disposed in 

radioactive waste.

8. The ampoule with the remainder of the radioactive sample is flame sealed, the outside checked for 

external contamination by taking and counting smears and stored. 

9. Identical steps are performed for the 3H vials and ampoule used for 3H-standard efficiency tracing. 

10. The LS vials are shaked or swirled to ensure complete mixing of the components. In addition, the 

solutions in the LS vials are visually examined for apparent non-homogeneity or phase separation after 

mixing

11. Each filled LS vial is checked to ensure that the LS vial cap is tightly closed, and the outside of each vial 

is checked for external contamination by taking and counting smears.

Comparative LS Counting

Each LS instrument has its own method and protocol for loading and counting samples as well as for data 

collection and is used in accordance with the respective manufacturer’s instructions and user manuals located 

in Bldg. 245, room H215. 

Solutions for calibration will be measured by comparative measurements against NIST standards (e.g., certified 

SRMs), if available.

A typical experimental design for such comparative measurements consists of: (1) prepare a set of 6 or more 

LS cocktails of the standard; (2) prepare a set of 6 or more matched cocktails of the solution to calibrate; (3) 

prepare at least two matched blanks for background subtraction; (4) these sets of cocktails are to be as closely 

matched as possible in terms of chemical composition; (5) at least two different series of cocktails should be 

prepared using two different scintillation fluids; (6) All cocktails should be measured in at least two different 

LS counters, and should be measured for a minimum of 3 to 5 measurement cycles for each trial. 
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The data collected contains: (1) start time and date of measurements; (2) elapsed time; (3) counting rate 

(usually in units of counts per minute) in a given window; and (4) quench indicating parameter (QIP). Options 

for other instrument quantities, such as luminescence detection and correction, homogeneity monitoring, etc. 

are available, but are generally not used. Collection and storage of the LS spectra may or may not be employed. 

All calculations are performed manually with spreadsheets and extensive graphical analyses. The LS counters’

software is not used for calculations. 

Massic counting rates for each vial for each measurement are calculated by subtracting that measurement 

cycle’s background (or average background for the entire measurement trial), correcting for radioactive decay 

to the reference time and normalizing by the mass of the radioactive substance in the vial. The two massic 

counting rates for the standard RS and for the test solution RX are related to the massic activity Ax and 

standard’s massic activity AS through AX = AS ( RX / RS ). 

The mean massic activity is obtained as an unweighted or weighted average of all AX values, with an appropriate 

statistical precision estimator, e.g., a standard deviation of the mean on considering all within- and betweenmeasurement components of variance.

LS Efficiency Tracing

Calibrations by LS efficiency tracing are often considered to be more “absolute” or primary compared to 

comparative LS counting. The procedure has been used somewhat routinely in the NIST Radioactivity Group 

since the late 1980s. 

The underlying model for LS efficiency tracing has been described in detail by Zimmerman and Collé [J. Res. 

Natl. Inst. Stds Tech. 102, 455-477, 1997] and references therein for the standardization of 63Ni. The following 

description of the method is an extract from this publication. It must be emphasized that many revised and 

improved efficiency calculation programs have been developed since the use of EFFY4 in 1996. EFFY4 is a 

revised and updated version of EFFY2. See E. Garcia-Torano and A. Grau Malonda, Comp. Phys. Comm. 36, 307 

(1985); and A. Grau Malonda, E. Garcia-Torano, and J. M. Los Arcos, Int. J. Appl. Radiat. Isot. 2, 157 (1985). For 

MICELLE and MICELLE2, see C.A. Grau, Comput. Phys. Comm. 176, 305 (2007); and K. Kosset, A. Grau-Carles, 

Appl. Radiat. Isot. 68, 1482-1488 (2010). Also there have been many computer modernizations that have 

enhanced computational capability. 

The CIEMAT/NIST 3H efficiency tracing method is a protocol by which the LS counting efficiency for a cocktail 

of interest under known, varying quenching conditions is obtained by following the efficiency of a closely 

matched (in terms of cocktail composition) standard. Tritium is a good candidate for this standard because of 

its low β-energy, which makes it very sensitive to quenching effects. In order to describe the overall efficiency 

of the counting system, a “figure of merit” M is employed. This parameter is meant to describe the energy (in 

keV) required to produce one photoelectron at the first dynode of the PMT. For a decay event with energy E
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from the β-spectral distribution, the fraction of energy lost due to heat absorption outside the solution (i.e., 

the container walls) is given by 1–W(E), while the fractional energy loss due to secondary interactions within 

the solution (“quenching”) is given by 1–Q(E). The energy remaining, and thus available to produce 

photoelectrons, is then EQ(E)W(E) and represents the unquenched energy of the decay event. The average 

number of photoelectrons produced at the first dynode of the PMT is then 

ň = M–1 EQ(E) W(E). (1)

For low energies (< 100 keV), β-particles with the distribution of these photoelectrons are assumed to follow 

Poisson statistics (at higher β-energies the distribution is normal). Thus, the probability of detecting x

photoelectrons from a mean number of photoelectrons ň can be calculated by 

P(x, n) =

n

−x

x!

 exp(–ň), (2)

and the probability of detecting zero electrons (the “nondetection probability”) is just

P(0, ň) = exp (–ň) , (3)

where the probability distributions are normalized to 1. The detection probability for a single PMT is then (1–

exp(–ň)). Hence, for a two-PMT system in coincidence, the expected efficiency above the detection threshold 

is given by 

ê(E) = {1 – exp [–ň]}2

= {1 – exp [–M–1EQ(E)W(E)]}2 . (4)

This efficiency, however, still only applies to events above the detection threshold. In order to include events 

below the threshold, an extrapolation to zero detection threshold must be made. 

This is achieved in the CIEMAT/NIST method by relating this probabilistic efficiency ê to one that can be 

determined experimentally. The calculation model for this transformation is embodied in some efficiency 

calculational program (e.g., EFFY4 or as used more recently MICELLE2). These programs calculate the efficiency 

for a given M by first calculating the shape of the β-spectrum for a particular nuclide through the Fermi 

distribution function P(Z, E) dE (not to be confused with the Poisson probability distribution P(x , n), given 

above). By comparing the number of particles emitted to the number of those that would most likely be 

detected, the efficiency can be calculated by the relationship 

ê =

∫ {1 – exp[–M−1 EQ (E)W(E)]}

2 P(Z,E) dE

Emax

0

∫ P(Z,E) dE Emax

0

(5)

where the integrals represent the total number of counts (numerator) or -particles (denominator) over the 

energy from 0 keV to the β-endpoint. In practice, the procedure consists of running the program to obtain a 
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table of M vs ê [(accomplished by numerical integration of Eq. (5)] for each of the nuclides involved in the 

study, including the tracing standard. The efficiency of the standard is then experimentally determined, and a 

corresponding value of M is read from the table. The precision in the determinations is based on the step size 

between successive M-values used when running the program. A fit of M vs q, an experimentally determined 

quench indicating parameter (QIP), is obtained for the standard. Since the relationship between q and M is 

assumed to be independent of the radionuclide, the same equation can be used to obtain M for each of the 

other nuclides based on the measured q for that nuclide as long as the measurements are carried out using a 

set of standards with cocktail compositions identical to those of the radionuclide being analyzed. By performing 

this fit of M vs q, it is possible to make the necessary (small) adjustments to the figure of merit between 

cocktails which are slightly mismatched in composition, volume, or any other condition that leads to slightly 

different quenching. Based on the M calculated from this equation, the efficiency for that particular nuclide 

can be obtained for those quenching conditions using the tables generated by the program.

The general data analysis scheme for any given experiment is as follows: 

1. The count rates of all background blanks are averaged. 

2. The count rate for each cocktail is corrected for background by subtracting the average integral 

background rate from the observed gross integral count rate of the cocktail. 

3. The counting rates are then decay corrected to a common reference time.

4. The corrected count rate for each cocktail was divided by the mass of the added radioactive solution 

to obtain a massic rate Rx with unit s–1g

–1

. 

5. An average (across all cycles in the measurement trial) massic count rate, Řx across all cycles in the 

measurementtrial, and an average QIP, qm is obtained for each cocktail. 

6. An average efficiency for each 3H cocktail is calculated from the known massic activity of the 3H 

standard and the experimental massic count rate for each 3H cocktail. 

7. Based on each average efficiency, an average figure of merit, M3H, is obtained for that cocktail by 

looking up the corresponding M value for that average efficiency in the tables generated by the 

program for 3H. 

8. A third-degree polynomial fit of M3H vs qm is obtained. 

9. From this fit, a figure of merit, MS, for each test sample cocktail is calculated from its qm. 

10. Using the tables generated by the program, an average efficiency for each test sample cocktail is

obtained. Dividing this efficiency into the average massic count rate for that cocktail, the massic 

activity, AS is calculated. 
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As for comparative LS counting, all calculations are performed using commercially-available spreadsheet 

programs and do not rely on LS counter internal software calculations. Similarly, the measurement results for 

the traced activity are thoroughly examined by graphical and statistical analyses, looking for possible 

systematic effects, including cocktail instability, cocktail composition variations, and between counter and 

between composition variations. Zimmerman and Collé [op. cit.] for the 1996 63Ni standardization examined 

the effect of 10 different experimental conditions. 

LS Counting of -Particle Emitting Nuclides and  Decay Chains 

Alpha particles in LS cocktails are detected with essentially 100 % efficiency. R. Fitzgerald and A.M. Forney, [LSC 

2010, “Determination of the liquid scintillation counting inefficiency (wall effect) for alpha emitters using the 

alpha-gamma anticoincidence method”, LSC2010 Advances in Liquid Scintillation Spectrometry, pp. 331-339 

(2010)] demonstrated that there is no counting inefficiency due to a “wall effect” for alpha emitters. As a result, 

LS calibrations of pure alpha emitters are rather straightforward. 

Source preparation and counting schema are essentially similar to that for comparative LS counting. A few (3 

to 6) LS vials are prepared with cocktails of a scintillation fluid, an aliquot of the radioactive material, and carrier 

solution to achieve an aqueous fraction of at least 0.06. The massic counting rate Rx is equivalent to the massic 

activity Ax.

For 4παβ LS counting of decay chains with multiple alpha and beta emitting nuclides, the LS counting rate at 

time t with respect to the reference time is given by the sum of the individual counting rates of all members of 

the decay chain, i.e., 

R = ∑i Aα(i)εα(i) exp (−it) + ∑j Aβ(j)εβ(j) exp (−jt), (6)

where Aα(i) and Aβ(j) are the activities of the respective α and β emitting nuclides, εα(i) and εβ(j) are the 

respective efficiencies for the α and β nuclides, and i and j are the respective decay constants for the 

nuclides. The efficiencies for εα(i) are taken as equal to 1, and the εβ(j) efficiencies are obtained through 

efficiency tracing using a series of matched 3H standard vials as the efficiency monitor. The individual Aα(i) and 

Aβ(j) are related to the parent nuclide through use of Bateman equations. The activity of the parent is obtained

through use of these relationships and the measured corrected LS rate R.

Treatment of the chains in the decay of 229.Th and for 234U, 235U and 238U in natural uranium has been described

by R. Fitzgerald, R. Collé, et al. [Appl. Radiat. Isot 68. 1303-1308 (2010)] and R. Collé and L. Laureano-Perez, et 

al. [ J.Res. Natl. Inst Stds Tech. 122, #44 (2017)], respectively. 

Triple-to-double Coincidence Ratio (TDCR) Counting
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Calibrations by TDCR counting are considered “absolute” or primary because the absolute counting efficiency 

is determined without reference to another activity measurement. The procedure has been used routinely in 

the NIST Radioactivity Group since the early 2000s. 

TDCR counting is a figure-of-merit technique, relying on the same underlying models as efficiency tracing and 

the principles have been described in detail in several reviews [e.g., Broda et al., Metrologia 44, S36-S52;

Kossert et al., Metrologia 52, S172-S190]. Very briefly, in a system with three photomultiplier tubes having 

equal quantum detection efficiencies, the counting efficiency for triple coincidences can be calculated from 

the energy spectrum, S(E), and the energy-dependent quench function, Q(E), according to

 (7)

and the counting efficiency for the logical sum of double coincidences is given by

. (8)

As in the efficiency tracing method, the counting efficiencies depend on the free parameter M. The free 

parameter of a given LS sample is defined by the condition

, (9)

where RT and RD are the experimentally determined net counting rates in the triple and the double coincidence 

channels, respectively. In practice, the “logical sum of doubles” is used for RD. For a counting system with three 

photomultiplier tubes, A, B, and C, where the double coincidence event rates are designated RAB, RBC, and RAC, 

the logical sum of doubles rate is calculated as RD = (RAB + RBC + RAC) - 2RT. After determination of the free 

parameter, the counting efficiency εD can be computed and subsequently the sample activity is obtained (A = 

Rnet/ ε) with ε = εD and Rnet = RD. In the same manner, the activity can be calculated using εT and RT.

The same calculational programs used in efficiency tracing are used to calculate the relationship between the 

triple-to-double coincidence ratio and the absolute εD and εT. To test the validity of the efficiency model, a 

range of efficiencies is sampled either via chemical quenching (as in efficiency tracing) or via application of 

neutral density (“gray”) filters to the LS vials. Additional corrections for, e.g., photomultiplier tube asymmetries 

and random coincidences are applied in spreadsheets as part of the data analysis.

The general data analysis scheme for any given experiment is as follows: 

max ( )

3 3

T

0

( )(1 ) ,

E E Q E

M  S E e dE

− 

 = − 

max

( )/3 2 ( )/3 3

D

0

( )(3(1 ) 2(1 ) )

E

EQ E M EQ E M  S E e e dE − −

= − − − 

T T

D D

( )

( )

M R

M R





=
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1. The count rates of background blanks are corrected for accidental coincidences and averaged. If 

multiple gray filters are used to vary efficiency, then filter-specific averages are used. 

2. Cocktail- and gray filter-specific double and triple count rates for each photomultiplier tube are 

corrected for accidental coincidences and then the appropriate blank counting rates are used to 

calculate background-corrected double and triple count rates.

3. The corrected double and triple count rates are then used to calculate the logical sum of doubles 

and the triple-to-double coincidence ratio.

4. The logical sum of doubles counting rates are then decay corrected to a common reference time.

5. The corrected count rates for each source are divided by the mass of the added radioactive solution 

to obtain a massic rate Rx with unit s–1g

–1

. 

6. The efficiency curve relating the triple-to-double coincidence ratio to εD (constrained to the range 

of experimentally observed values of the triple-to-double coincidence ratio) is fit to an appropriate 

polynomial or spline function. That function is then used to calculate a value of εD from the measured 

triple-to-double coincidence ratio associated with each Rx. 

7. Dividing each Rx by its associated εD then gives the massic activity. The data are examined for any 

trending in the calculated massic activities with time or efficiency. 

As for comparative LS counting, all calculations are performed using commercially-available spreadsheet 

programs. Similarly, the measurement results for the activity are thoroughly examined by graphical and 

statistical analyses, looking for possible systematic effects, including cocktail instability, cocktail composition 

variations, and between counter and between composition variations.

Uncertainty Analysis 

Comparative LS Counting

The quality of the LS measurement results is evaluated by graphical and statistical analyses of the Ax data, 

evaluating temporal cocktail stability by examining Ax as a function of measurement time and evaluating the 

within-measurement variance for replicates on a given vial and the between-vial variance for a given set of 

cocktails, as well as the between -composition and between-counters components of variance. Acceptable 

between-component differences should be less than 2 % in worst cases. 

Typical uncertainty components are shown in many of the dozens of papers listed in the References Section. 

The uncertainty components are combined in quadrature to obtain a standard uncertainty, which is expanded 
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by a factor of k = 2 to give an expanded uncertainty. Depending on nuclide and other measurement conditions, 

typical k = 2 relative expanded uncertainties by comparative LS counting range from about 0.3 % to 1.5 %. 

LS Efficiency Tracing

Uncertainty analyses and evaluations of measurement results for efficiency tracing are similar to those for 

comparative LS counting. 

Zimmerman and Collé [op. cit.] developed a complete measurement and uncertainty model for LS efficiency 

tracing for the standardization of 63Ni. The model identified 28 separate uncertainty components (with 

estimates of their magnitudes), some of which are partially or wholly embodied in computed precision 

estimators. The model is illustrated schematically in Figure 1.

In addition, a special issue of Metrologia [vol. 52 (2015)] on uncertainty treatments for radioactivity 

measurements includes an article by K. Kossert, R Broda, P. Cassette, G. Ratel and B. Zimmerman on

“Uncertainty determination for activity measurements by means of the TDCR method and the CIEMAT/NIST

efficiency tracing technique.”

TDCR counting

Uncertainty analyses and evaluations of measurement results for TDCR counting are similar to those for 

comparative LS counting and efficiency tracing. 

The above-mentioned article by Kossert et al. in the special issue of Metrologia [vol. 52 (2015)] on uncertainty 

treatments for radioactivity measurements gives an excellent overview of the major uncertainty components 

and important considerations.

Acceptance Criteria

The data are examined to see if the results show the expected activity, and the standard deviation of repeated 

measurement on the source is checked to see if it is in the range expected for the radionuclide (normally less 

than 0.1 percent at 1 sigma). If there is a discrepancy in activity, a new set of sources are prepared and 

measured. If the standard deviation is abnormally high, the data is examined for possible trends. The customer 

is contacted if a discrepancy cannot be resolved.

Validation of Method

The measurement method is validated using systematic assessment of the factors influencing the result with 

extensive graphical analyses. The method robustness is tested by using more than one LS cocktail and 
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evaluating the measurement results uncertainty based on an understanding of the theoretical principles and 

practical experience of the performance of the method.

Calibration Report

Reports of Test or Calibration, at a minimum should contain or address the following, unless there are valid 

reasons for not doing so. Additional information may be provided

a) a title (e.g., “Report of Test”, “Calibration Report” or “Report of Special Test”). 

b) the first page shall be on NIST letterhead or be equivalently identified as originating from NIST.

c) the name and address of the laboratory. 

d) the NIST Calibration Services test or calibration number, and service ID number. 

e) page numbers, with the last page designated as the end of the report. 

f) the name and address of the customer (refer to USPS Publication 28, Postal Addressing Standards). 

g) a description, unambiguous identification, and, when necessary, the condition of the item(s) tested or 

calibrated. 

h) the principal radionuclide 

i) reference time and date 

j) equipment used and method of calibration (traceability to primary standard); a description of the 

calibration method; additions to, deviations, or exclusions from the method, if applicable. 

k) certified values for activity with the units of measurement

l) decay-scheme assumptions, if applicable

m) assessment of radionuclidic purity 

n) overall uncertainty determinations for calibration

o) the date of receipt of the test or calibration item(s), where this is critical to the validity and application 

of the results. 

p) the conditions (e.g., environmental) under which the calibrations were made that have an influence 

on the measurement results, if applicable

q) the date(s) of performance of the laboratory activity. 

r) the date of issue of the report. 

s) a statement to the effect that the results relate only to the items tested, calibrated or sampled; 

evidence or a statement that the measurement results are traceable. 

t) the name of the person(s) performing the measurements and analyses; the name, function, and 

signature of the person(s) authorizing the report. 

u) an explanation of the proper use and interpretation of the reported results as necessary (this can be 

in the form of an addendum).
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Reported values are checked against the data on the spreadsheet and this check is noted by initialing. Drafts 

of reports are identified as such and assigned a draft number. Results of draft proofreading are noted and 

initialed on the draft. Signatures are obtained at the appropriate level and, if paper, the original report is 

embossed with a Department of Commerce seal. A copy marked file copy and two marked copies are 

maintained with the calibration printouts, stored in folders identified by company, radionuclide, date, and 

service number. If requested, the original paper report is sent to the customer. Electronically signed reports 

are stored in the calibration record of the E-commerce system.

Records

Calibration printouts and report copies are stored in folders identified by company, radionuclide, date, and 

service number. 

Ring binders of calibration records, including measurement data, are maintained by the Radioactivity Group in 

Building 245 for at least five years.

Documentation

User manuals for the LS counters are in Bldg 245, Room H215.

SOP 682.04-0071 (March 2011), Sample Preparation and Liquid Scintillation Counting – located in SOP shared 

drive.

SOP 846.04-0031 (October, 2019), Counting of Liquid Scintillation (LS) Sources – located in SOP shared drive.

NIST website, Activity Calibrations, Special Tests of Beta-Particle-emitting solution Sources, 

https://shop.nist.gov/ccrz__ProductDetails?sku=43060S&cclcl=en_US

Filing and Retention

Filing and Retention Calibration printouts are stored in folders identified by company, radionuclide, date, and 

service number. For customer calibration, the calibration report is prepared, and the required signatures

obtained. A copy is made for customer file and the original sent. Reports created and signed digitally are 

downloaded to the calibration record in the E-commerce system. The RPD Quality Manager shall maintain the 

original and all past versions of this RPD Procedure
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Figure 1. Measurement model for 4πβ LS spectrometry of 63Ni (as an example) using 3H-standard efficiency 

tracing as given by the CIEMAT/NIST method. The component uncertainties are identified as either ui or si as 

identified by Zimmerman and Collé [op. cit.]
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References

This compilation of references is a partial list of some of the standardizations and calibrations by LS 

measurements by the NIST Radioactivity Group. 

E. Napoli, J.T. Cessna, R. Fitzgerald, L. Pibida, R. Collé, L. Laureano-Perez, B.E. Zimmerman, D.E. Bergeron, 

Primary standardization of 224Ra activity by liquid scintillation counting, Applied Radiation Isotopes 155 (2020) 

108933; https://doi.org/10.1016/j.apradiso.2019.108933

R.M. Essex, R.W. Williams, K.C. Treinen, R. Collé, R. Fitzgerald, R. Galea, J. Keightley, J. LaRosa, L. LaureanoPerez, S. Nour, L. Pibida, Preparation and calibration of a 231Pa reference material, Journal of Radioanalytical 

and Nuclear Chemistry; https://doi.org/10.1007/s10967-019-06711-6 (2019). 

R.M. Essex, J.L. Mann, R. Collé, L. Laureano-Perez, M.E. Bennett, H. Dion, R.P. Fitzgerald, A.M. Gaffney, A. 

Gourgiotis, A. Hubert, K.G.W. Inn, W.S. Kinman, S.P.Lamont, R. Steiner, R.W. Williams. New determination of 

the 229.Th half-life, Journal Radioanalytical and Nuclear Chemistry 317, 515-525 (2018). 

https://doi.org/10.1007/s10967-018-6032-9

D.E. Bergeron, J.T. Cessna, R. Fitzgerald, L. Pibida, B.E. Zimmerman, Standardization of I-124 by three liquid 

scintillation-based methods, Appl. Radiat. Isotop., 154, 108849 (2019).

D.E. Bergeron, J.T. Cessna, R. Fitzgerald, L. Pibida, B.E. Zimmerman, Standardization of 64Cu activity, Appl. 

Radiat. Isotop., 139, 266 (2018).

R. Collé, L. Laureano-Perez, R.P. Fitzgerald, S. Nour, J.J. LaRosa, B.E. Zimmerman, L. Pibida, D.E. Bergeron, 

Natural Uranium Radioactivity Solution Standard: SRM 4321d, Journal of Research of the National Institute of 

Standards and Technology, 122, Article 44 (2017). https://doi.org/10.6028/jres.122.044

R. Collé, L. Laureano-Perez, D.E. Bergeron, Comparison of tritiated-water standards by liquid scintillation for 

calibration of a new Standard Reference Material, Applied Radiation Isotopes 112, 38-49 (2016).

R. Collé, R.P. Fitzgerald, L. Laureano-Perez, Development of an Ultra-Pure, Carrier-Free 209Po Solution Standard, 

Journal of Research of the National Institute of Standards and Technology, 120, 138-163 (2015). 

http://dx.doi.org/10.6028/jres.120.011

D.E. Bergeron, R. Galea, L. Laureano-Pérez, B.E. Zimmerman, Comparison of C-14 liquid scintillation counting 

at NIST and NRC Canada, Appl. Radiat. Isotop. 109, 30 (2016).

B.E. Zimmerman, D.E. Bergeron, J.T. Cessna, R. Fitzgerald, L. Pibida, Revision of the NIST standard for 

223Ra: New measurements and review of 2008 data, NIST Journal of Research, 120, 37 (2015).
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L. Laureano-Pérez, R. Collé, R. Fitzgerald, Standardization of 237Np, Applied Radiation Isotopes 87, 269-273 

(2014). 

R. Collé, R.P. Fitzgerald, L. Laureano-Perez, A new determination of the 209Po half-life, Journal of Physics G: 

Nuclear & Particle Physics 41, 105103 (2014). 

In Error for 50 years: critical Polonium-209 half-life is revised, IOP Science, LabTalk, 

http://iopscience.iop.org/0954-3899/labtalk-article/58252 Polonium’s Most Stable Isotope Gets Revised HalfLife Measurement, NIST Tech Beat (September 9, 2014), http://www.nist.gov/pml/div682/po-090914.cfm

D.E. Bergeron, J.T. Cessna, B.M. Coursey, R. Fitzgerald, and B.E. Zimmerman, A review of NIST primary activity 

standards for 18F: 1982 to 2013, NIST Journal of Research, 119, 371 (2014).

R. Fitzgerald, B.E. Zimmerman, D.E. Bergeron, J.T. Cessna, L. Pibida, D.S. Moreira, A new NIST primary 

standardization of 18F, Appl. Radiat. Isotop., 85, 77 (2014).

L. Laureano-Perez, R. Collé, R. Fitzgerald, B.E. Zimmerman, L. Cumberland, Investigation into the 

Standardization of 99Tc, Applied Radiation Isotopes 68, 1489-1494 (2010).

R. Fitzgerald, R. Collé, L. Laureano-Perez, L. Pibida, S. Nour, and B.E. Zimmerman, A new primary 

standardization of 229Th , Applied Radiation Isotopes 68, 1303-1308 (2010).

L. Laureano-Pérez, R. Collé, R. Fitzgerald, Standardization of Pu-241: Issues and Problems, 

Advances in Liquid Scintillation Spectrometry, LSC 2010, Radiocarbon, University Arizona, pp. 321-330, 2010.

R. Collé, Radionuclidic standardization by primary methods: An overview, Journal Radioanalytical & Nuclear 

Chemistry 280, 265-273 (2009). 

R. Collé and L. Laureano-Perez, On the Standardization of 209Po and 210Pb, Advances in Liquid Scintillation 

Spectrometry, LSC 2008, Radiocarbon, University Arizona, pp. 77-85, 2009.

R. Fitzgerald A.M. Forney, DETERMINATION OF THE LIQUID SCINTILLATION COUNTING INEFFICIENCY (WALL 

EFFECT) FOR ALPHA EMITTERS, USING THE ALPHA-GAMMA ANTICOINCIDENCE METHOD, LSC2010, 

Radiocarbon, (2011) https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=906829

R. Collé, B.E. Zimmerman, P. Cassette, L. Laureano-Perez, 63Ni, its half-life and standardization: Revisited, 

Applied Radiation Isotopes 66, 60-68 (2008).
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R. Collé, Radionuclidic standardization by primary methods: An overview (extended abstract), in M. Navarrete, 

Proceedings of the 2nd International Nuclear Chemistry Congress, National University of Mexico, Mexico City, 

2008, p.64. 

R. Collé, L. Laureano-Perez, I. Outola, A note on the half-life of 209Po, Applied Radiation Isotopes 65, 728-730 

(2007).

L. Laureano-Perez, R. Collé, R. Fitzgerald, I. Outola, L. Pibida, A liquid-scintillation-based primary 

standardization of 210Pb, Applied Radiation Isotopes 65, 1368-1380 (2007).

R. Collé, Calibration of 32P "hot-wall" angioplasty-balloon-catheter sources by liquid-scintillation-spectrometrybased destructive radionuclidic assays, Applied Radiation Isotopes, 54, 611-622 (2001).

R. Collé, On the Radioanalytical Methods Used to Assay Stainless-Steel-Encapsulated, Ceramic-Based 90Sr90Y 

Intravascular Brachytherapy Sources, Applied Radiation Isotopes 52, 1-18 (2000).

R. Collé, Chemical Digestion and Radionuclidic Assay of TiNi-Encapsulated 32P Intravascular Brachytherapy 

Sources, Applied Radiation Isotopes 50, 811-833 (1999).

B.M. Coursey, R. Collé, B.E. Zimmerman, J. Cessna, and D.B. Golas, National Radioactivity Standards for BetaEmitting Radionuclides Used in Intravascular Brachytherapy, International Journal of Radiation Oncology, 

BiologyPhysics 41, 207-216 (1998).

P. Cassette, T. Altzitzoglou, R. Broda, R. Collé, P. Dryak, P. de Felice, E. Gunther, J.M. Los Arcos, G. Ratel, B. 

Simpson, and F. Verrezen, Comparison of Activity Measurements of 63Ni and 55Fe in the Framework of the 

EUROMET 297 Project, Applied Radiation Isotopes 49, 1403-1410 (1998).

R. Collé and B.E. Zimmerman, A Compendium on the NIST Radionuclidic Assays of the Massic Activity of 63Ni 

and 55Fe Solutions Used for an International Intercomparison of Liquid Scintillation Spectrometry Techniques, 

Journal of Research NIST 102, 523-549 (1997).

R. Collé, A Simple Transform to Linearize and Resolve Two-Component Decay Data: Illustration of Its Use and 

Efficacy in Assaying 33P/32P Mixtures by Liquid Scintillation Counting, Radioactivity and Radiochemistry 8, no.2, 

5-18 (1997).

B.E. Zimmerman and R. Collé, Standardization of 63Ni by 4 Liquid Scintillation Spectrometry with 3H-Standard 

Efficiency Tracing, Journal of Research NIST, 102, 455-477 (1997).
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B.E. Zimmerman and R. Collé, Comparison of the French and U.S. National 3H (Tritiated H2O) Standards by 4

Liquid Scintillation Spectrometry, Applied Radiation Isotopes 48, 521-526 (1997).

R. Collé, Cocktail Mismatch Effects in 4 Liquid Scintillation Spectrometry: Implications Based on the 

Systematics of 3H Detection Efficiency and Quench Indicating Parameter Variations with Total Cocktail Mass 

(Volume) and H2O Fraction, Applied Radiation Isotopes 48, 833-842 (1997).

R. Collé, Systematic Effects of Total Cocktail Mass (Volume) and H2O Fraction on 4 Liquid Scintillation 

Spectrometry of 3H, Applied Radiation Isotopes, 48, 815-831 (1997).

B.E. Zimmerman and R. Collé, Cocktail Volume Effects in 4 Liquid Scintillation Spectrometry with 3H-Standard 

Efficiency Tracing for Low-Energy -Emitting Radionuclides, Applied Radiation Isotopes, 48, 365-378 (1997). 

R. Collé and B.E. Zimmerman, Nickel-63 Standardization: 1968-1995, Radioactivity and Radiochemistry 7, no. 

2, 12-27 (1996).

R. Collé and B.E. Zimmerman, 63Ni Half-Life: A New Experimental Determination and Critical Review, Applied 

Radiation Isotopes, 47, 677-691 (1996).

F.J. Schima and R. Collé, Alpha-Particle and Electron Capture Decay of 209Po, Nuclear Instruments and Methods 

in Physics Research, A369, 498-502 (1996).

B.E. Zimmerman and R. Collé, The Standardization of 63Ni by Liquid Scintillation Spectrometry with 3H-Standard 

Efficiency Tracing: A New Calibration and Review of Data from Calibrations Over the Past 27 Years, Radioactivity 

and Radiochemistry 6, no.4, 52 (1995) [abstract only].

 

R. Collé, Zhichao Lin, F.J. Schima, P.A. Hodge, J.W.L. Thomas, J.M.R. Hutchinson and B.M. Coursey, Preparation 

and Calibration of Carrier-Free 209Po Solution Standards, Journal of Research NIST 100, 1-36 (1995).

R. Collé, A Precise Determination of the 222Rn Half-Life by 4 Liquid Scintillation Measurements, 

Radioactivity and Radiochemistry 6, no.1, 16-29 (1995).

R. Collé, Zhichao Lin, J.M.R. Hutchinson and F.J. Schima, Delayed Isomeric State in 205Pb and Its Implications for 

4 Liquid Scintillation Spectrometry of 209Po, Applied Radiation Isotopes 45, 1165-1175 (1994).

R. Collé and Joylene W.L. Thomas, 36Cl/Cl Accelerator-Mass-Spectrometry Standards: Verification of Their 

Serial-Dilution-Solution Preparations by Radioactivity Measurements, Journal of Research NIST 98, 653-677 

(1993). 
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R. Collé, Long-Term Stability of Carrier-Free Polonium Solution Standards, Radioactivity and Radiochemistry 4, 

no. 2, 20-35 (1993).

B.M. Coursey, J.M. Calhoun, J. Cessna, J., D.B. Golas, F.J. Schima, M.P. Unterweger, M.P., Liquid-Scintillation 

Counting Techniques for the Standardization of Radionuclides Used in Therapy, Nucl. Instrum. Meth. Part A.,

A339, 36 (1994).

J.M. Calhoun, J. Cessna, and B.M. Coursey, A System for the Intercomparison of Pure-Beta-Particle-Emitting 

Radionuclides.Nuclear Instrum. Meth. Part A. A312, 114 (1992.)

J.M. Calhoun, J. Cessna, J., B.M. Coursey, D.D. Hoppes, F.J. Schima, F.J. and M.P. Unterweger, The 

Standardization and Decay Scheme of Holmium-166, Radioactivity and Radiochemistry V2/N4, 38 (1991), 

B.M. Coursey, E. Garcia-Torano, D.B Golas, A. Grau Malonda, D.H. Gray, D.D. Hoppes, D.D., J.M.Los Arcos, , 

M.T. Martin-Casallo, F.J. Schima, M.P. Unterweger, M.P. ,The Standardization and Decay Scheme of Rhenium186, Appl. Radiat. Isot. 42, 865 (1991).

J.M. Calhoun, B.M. Coursey, D. Gray, L. Karam, The Standardization of Sulfur-35 Methionine by Liquid 

Scintillation Efficiency Tracing with Hydrogen-3, Proc. International Conference - New Trends in Liquid 

Scintillation Counting and Organic Scintillators, Gatlinburg, TN, Oct. 1989. Ross. H., Noakes, J. and Spaulding, 

J. (eds.), Lewis Publishers, Chelsea, MI, 1991.

B.M. Coursey, L.L. Lucas,A. Grau Malonda, E. Garcia-Torano, E. , The Standardization of Plutonium-241 and 

Nickel-63, Nuclear Instrum. and Meth. Part A. A279, 603 (1989).

A. Grau Malonda, B.M. Coursey, B.M., Calculation of Beta-Particle Counting Efficiency for Liquid-Scintillation 

Systems with Three Phototubes,.Appl. Radiat. Isot. 39, 1191 (1988).

B.M. Coursey, M.P. Unterweger, L.L. ,Lucas, E. Garcia-Torano, E., Data-Handling System for Liquid-Scintillation 

Standardizations, Trans. Amer. Nucl. Soc. 55, 54 (1987). 

B.M.Coursey, J.M. Calhoun, Liquid Scintillation Counting of Inorganic Radiochemicals in High-Efficiency 

Scintillators in Proc. Intl. Conf. "Liquid Scintillation Counting: Recent Developments and Applications, Peng. 

C.T., Horrocks, D.L., Alpen, E.L. (eds.), Academic Press, New York (1980).

A. Grau Malonda, B.M. Coursey, Standardization of Isomeric-Transition Radionuclides by Liquid-Scintillation 

Efficiency Tracing with Hydrogen-3: Application to Technetium-99m, Appl. Radiat. Isot. 38, 695 (1987). 

B.M.Coursey, D.D. Hoppes, D.D.,F.J. Schima, M.P. Unterweger,, The Standardization of Samarium-153,.Appl. 

Radiat. Isot. 38, 31 (1987). 
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B.M. Coursey, W.B. Mann, A. Grau Malonda, E. Garcia-Torano, J.M. Los Arcos, J.A.B. Gibson, and D. Reher, 

Standardization of Carbon-14 by 4πß Liquid-Scintillation Efficiency Tracing with Hydrogen-3.Int. J. Appl. 

Radiat. Isotopes 37, 403 (1986).

B.M. Coursey, A. Grau Malonda, E. Garcia-Torano, E., J.M. Los Arcos, Standardization of Pure-Beta-ParticleEmitting Radionuclides, Trans. Amer. Nucl. Soc. 50, 13 (1985). 

B.M. Coursey, J.A.B. Gibson, M. Heitzmann, and J. Leak, Standardization of Technetium-99 by Liquid 

Scintillation Counting,.Int. J. Appl. Rad. Isotopes 35, 1103 (1984).

B.M. Coursey, D.D. Hoppes, D.D., M.P. Unterweger, A. Grau, R. Margolin, and R. Kessler, Standardization of 

Fluorine-18 for Use in Positron Emission Tomography,.Int. J. Appl. Rad. Isotopes 34, 1181 (1983). 

B.M. Coursey, J.M. Calhoun, R.L. Ayres, and W. Sunaryo, W. Liquid Scintillation and NaI(Tl) Counting of Iodine129 in Solution, Trans. Amer. Nucl Soc. 43, 42 (1982).

B.M. Coursey, J.M. Calhoun, K.G.W Inn, L.L. Lucas, L.L., Liquid-Scintillation Counting Techniques for Inorganic 

Radiochemicals, Trans. Amer Nucl Soc. 39, 25 (1981).