ISO/FDIS 11704

ISO/TC 147/SC 3
Secretariat: AFNOR
Date: 2026-08-31
Water quality — Gross alpha and gross beta activity — Test method
using liquid scintillation counting
Date: 2026-06-15
Third edition
Qualité de l'eau — Activités alpha globale et bêta globale — Méthode d'essai par comptage des scintillations en
milieu liquide
TThhiiss d drraft iaft iss su subbmmiitted tted to to a pa parallearallel vl vote ote iinn IS ISOO, CE, CENN.

FDIS stage
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iii
Contents
Foreword . v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and symbols . 2
3.1 Terms and definitions . 2
3.2 Symbols . 2
4 Principle . 4
5 Sampling . 4
6 Chemical reagents, certified reference solutions and equipment . 5
6.1 Chemical reagents . 5
6.2 Certified reference solutions . 5
6.3 Equipment . 6
7 Procedure . 6
7.1 Direct counting . 6
7.2 Thermal preconcentration . 6
7.3 Sample preparation . 7
7.4 Liquid scintillation measurement . 7
8 Expression of results . 9
8.1 Calculation of activity per mass . 9
8.2 Standard uncertainty. 10
8.3 Decision threshold . 11
8.4 Limit of detection . 12
8.5 Limits of the coverage intervals . 13
9 Quality control . 14
10 Interference control . 14
10.1 Contamination . 14
10.2 Ingrowth of radon . 14
10.3 Loss of polonium . 15
11 Test report . 15
Annex A (informative) Set-up parameters and validation data . 17
Annex B (informative) Method performances under different conditions . 22
Bibliography . 23

iv
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
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The procedures used to develop this document and those intended for its further maintenance are described
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ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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This document was prepared by Technical Committee ISO/TC 147, Water quality, Subcommittee SC 3,
Radioactivity measurements., in collaboration with the European Committee for Standardization (CEN)
Technical Committee CEN/TC 230, Water analysis, in accordance with the Agreement on technical cooperation
between ISO and CEN (Vienna Agreement).
This third edition cancels and replaces the second edition (ISO 11704:2018), which has been technically
revised.
The main changes are as follows:
— — the introduction has been revised;
— — the expression of results has been revised in 8Clause 8;;
— — the Bibliography has been updated.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
v
Introduction
Radionuclides are present throughout the environment, thus, water bodies (e.g. surface waters, ground
waters, sea waters) contain radionuclides, which can be of either natural, or anthropogenic origin.
3 14 40
— — Naturally-occurring radionuclides, including H, C, K, and those originating from the thorium and
210 210 222 226 228 227 232 231 234 238
uranium decay series, in particular Pb, Po, Rn, Ra, Ra, Ac, Th, Pa, U and U, can be
found in water bodies due to either natural processes (e.g. desorption from the soil and runoff by rain
water) or released from technological processes involving naturally occurring radioactive materials (e.g.
mining, mineral processing, oil, gas, and coal production water treatment, and the production and use of
phosphate fertilizers).
55 59 63 90 99
— — Anthropogenic radionuclides such as Fe, Ni, Ni, Sr, Tc, transuranic elements (e.g. Np, Pu, Am,
60 137
and Cm) and some gamma emitting radionuclides such as Co and Cs can also be found in natural
waters. Small quantities of anthropogenic radionuclides can be discharged from nuclear facilities into the
environment as a result of authorized routine releases. The radionuclides present in liquid effluents are
[1]
usually controlled before being discharged to the environment[1] and water bodies. Anthropogenic
radionuclides used for medical and industrial applications can be released into the environment after use.
Anthropogenic radionuclides are also found in waters due to contamination fallout resulting from above-
ground nuclear detonations and accidents such as those that have occurred at the Chornobyl and
Fukushima nuclear facilities.
Radionuclide activity concentrations in water bodies can vary according to local geological characteristics and
climatic conditions and can be locally and temporally enhanced by releases from nuclear facilities during
[2][3]
planned, existing and emergency exposure situations[2][3]. . Some drinking-water sources can thus
contain radionuclides at activity concentrations that can present a human health risk. The World Health
[4]
Organization (WHO) recommends to routinely monitor radioactivity in drinking waters[4] and to take
proper actions when needed to minimize the health risk.
Gross alpha and beta measurements do not provide the exact radioactive activity of a sample but estimate the
activity concentration based on standard calibration sources. These measurements, known as the alpha and
beta index, serve as screening tools for an initial assessment of the total radioactivity.
National regulations usually specify the activity concentration limits that are authorized in drinking waters,
water bodies and liquid effluents to be discharged to the environment. These limits can vary for planned,
existing and emergency exposure situations. As an example, during either a planned or existing situation, the
-1 -1
WHO guidance level in drinking water is 0,5 Bq·l for gross alpha activity and 1 Bq·l for gross beta
[4]
activity[4] (see NOTES 1 and 2). Conformity to these limits is assessed by measuring radioactivity in water
samples and by comparing the results obtained, with their associated uncertainties, as specified by ISO/IEC
[5]
Guide 98-3 and ISO 5667-20[5] .
NOTE 1 If the value is not specified in Annex 6 of Reference [4][4],, the value has been calculated using the formula
provided in Reference [4][4] and the dose coefficient data from References [6][6] and[7] [7].
NOTE 2 The guidance level calculated in Reference [4][4] is the activity concentration that results in an effective dose
-1 −1
of 0,1 mSv·a to members of the public for an intake of 2 l·d of drinking water for one year. This is an effective dose that
represents a very low level of risk to human health and which is not expected to give rise to any detectable adverse health
[4]
effects[4] .
Minor modifications such as test portion sample volume and counting time to the method described in this
document can be made if needed to ensure that the decision threshold, detection limit and uncertainties are
below the required limits. This can be done for several reasons such as emergency situations, lower national
guidance limits and operational requirements.
vi
DRAFT International Standard ISO/FDIS 11704:2025(en)

Water quality — Gross alpha and gross beta activity — Test method
using alpha liquid scintillation counting
WARNING — Persons using this document should be familiar with normal laboratory practice. This
document does not purport to address all of the safety problems, if any, associated with its use. It is
the responsibility of the user to establish appropriate safety and health practices.
IMPORTANT — It is essential that testsTests conducted according to this document shall be carried
out by suitably qualifiedtrained staff.
1 Scope
This document specifies a method to measure gross alpha and gross beta activity concentrations for alpha-
and beta-emitting radionuclides using liquid scintillation counting (LSC).
-
The method described in this document is applicable to all types of waters with a dry residue of less than 5 g·l
. If there is a noticeable colour, then additional preparative steps will be needed such as dilution or acid
digestion.
The method described in this document is applicable to test samples of non-saline waters following proper
sampling, handling and preparation.
As mentioned in the introduction, the gross alpha and gross beta index is not expected to be as accurate or as
precise as specific radionuclide analysis after radiochemical separations: it is a screening analysis to ensure
reference levels of specific alpha and beta emitters have not been exceeded.
The method described in this document covers only non-volatile radionuclides below 80 °C, since some.
NOTE Some gaseous or volatile radionuclides (e.g. radon and radioiodine) can be lost during the source preparation.
The method described in this document is applicable to test samples of drinking water, rain water, surface and
ground water as well as cooling water, industrial water, domestic and industrial waste water after proper
sampling and test sample preparation. Filtration of the sample is necessary if suspended particles are present.
The detection limit depends on the test portion volume, the instrument used, the background count rate, the
detection efficiency and the counting time. The detection limit of the method described in this document, using
-1 -1
currently available liquid scintillation apparatus, is approximately 20 mBq·kg (α) and 100 mBq·kg (β),
-1
which is lower than the WHO criteria for safe consumption of drinking water 500 mBq·kg (α) and
-1 [4]
1 000 mBq·kg (β). This value can typically be achieved with a counting time of 500 min for a test sample
volume of 0,08 l.
The method described in this document can be used in the event of an emergency situation, because the results
can be obtained in less than 4 h by directly measuring water test samples without any treatment.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in
measurement (GUM:1995)
ISO 5667--1, Water quality — Sampling — Part 1: Guidance on the design of sampling programmes and
sampling techniques
ISO 5667--3, Water quality — — Sampling — — Part 3: Guidance on the preservationPreservation and
handling of water samples
ISO 80000-5667-10, Quantities and unitsWater quality — Sampling — Part 10: Atomic and nuclear
physicsGuidance on sampling waste water
ISO 11929-1, Determination of the characteristic limits (decision threshold, detection limit and limits of the
confidencecoverage interval) for measurements of ionizing radiation — Fundamentals and application –— Part
1: Elementary applications
ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
ISO/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in
measurement (GUM:1995)
ISO 80000-10, Quantities and units — Part 10: Atomic and nuclear physics
3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 80000--10, ISO 11929-1 and
ISO/IEC Guide 98--3 apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— — ISO Online browsing platform: available at https://www.iso.org/obp
— — IEC Electropedia: available at https://www.electropedia.org/
3.2 Symbols
−1
a , a Gross alpha and gross beta activity per mass Bq·g
α β
−1
, 𝑎˜ , 𝑎˜ Possible or assumed true values of the gross alpha and gross beta mass activity Bq·g
𝛼 𝛽
respectively
∗
∗
−1
, 𝑎 , 𝑎 Gross alpha and gross beta decision threshold respectively Bq·g
𝛼 𝛽
#
# −1
Gross alpha and gross beta detection limit respectively Bq·g
, 𝑎 , 𝑎
𝛼 𝛽
⊲ ⊳
−1
𝑎 , 𝑎 Lower and upper limits of the probabilistically symmetric coverage interval for Bq·g
𝛼 𝛼
gross alpha mass activity
⊲ ⊳
−1
𝑎 , 𝑎 Lower and upper limits of the probabilistically symmetric coverage interval for Bq·g
𝛽 𝛽
gross beta mass activity
< > < >
−1
𝑎 , 𝑎 𝑎 , 𝑎 Lower and upper limits of the shortest coverage interval for gross alpha mass Bq·g
α α 𝛼 𝛼
activity
< >
−1
𝑎 , 𝑎 Lower and upper limits of the shortest coverage interval for gross beta mass Bq·g
𝛽 𝛽
activity
A , A Activity of the alpha and beta emitter certified reference solution used for the α Bq
α β
and β calibration sources
m Mass of the test portion g
m Mass of initial sample subject to heating or possibly concentration g
m Mass of heated or concentrated sample g
m Mass of heated or concentrated sample transferred in the vial g
m , m Mass of alpha and beta emitters certified reference solutions, respectively g
Sα Sβ
−1
r , r Sample gross count rate, from the alpha and beta windows, respectively s
gα gβ
−1
r , r , r Background or blank count rate, from the alpha, beta and total windows, s
0α 0β 0T
respectively (background is indicate for calibration, blank for measurement)
−1
r , r , r Count rate of the alpha calibration source in the alpha, beta and total window s
Sα,α Sα,β Sα,T
−1
r , r , r Count rate of the beta calibration source in the alpha, beta and total window s
Sβ,α Sβ,β Sβ,T
t Sample counting time s
g
t Blank counting time s
t , t Counting time of α and β calibration sources s
Sα Sβ
−1
u (a) Standard uncertainty associated with the measurement result Bq·g
𝑢 Relative standard uncertainty -—
rel
−1
U Expanded uncertainty, calculated from U = k·u (a), where k = 1, 2 … Bq·g
−1
𝑢˜ (𝑎˜ ) Standard uncertainty of a as a function of its true value Bq·g
α
𝛼
−1
𝑢˜ (𝑎˜ ) Standard uncertainty of a as a function of its true value Bq·g
β
𝛽
ε , ε Counting efficiency for alpha and beta, respectively —
α β
Φ Distribution function of the standardized normal distribution —
α, β False positive and false negative probability respectively —
𝜒 Alpha interference — Fraction, i.e. fraction of counts observed in the beta —
𝛼→𝛽
window with respect to the total number of counts measured by the counter
when an alpha emitter is measured
𝜒 Beta interference — Fraction, i.e. fraction of counts observed in the alpha —
𝛽→𝛼
window with respect to the total number of counts measured by the counter
when a beta emitter is measured
k Quantiles of the standardized normal distribution for the probabilities p (for —
p
instance p = 1 − α, 1 − β or 1 − γ/2)
k Quantiles of the standardized normal distribution for the probabilities q (for —
q
instance q = 1−α, 1− β or 1−γ/2)
s Standard deviation of the efficiency in a repeatability condition —
rep
−1
w , w calibration factor for gross alpha and gross beta respectively l
α β
4 Principle
Gross alpha and gross beta activity concentrations are determined by using liquid scintillation counting of a
water sample mixed with a scintillation cocktail. If there is a noticeable colour, then additional preparative
steps shall be implemented, such as dilution or acid digestion.
As mentioned in the introduction, the gross alpha and gross beta index is not expected to be as accurate or as
precise as specific radionuclide analysis after radiochemical separations: it is a screening analysis to ensure
reference levels of specific alpha and beta emitters have not been exceeded.
Gross alpha and gross beta determinations are not absolute determinations of the sample radioactive activity,
but relative determinations referred to a specific alpha or beta emitter which constitutes the standard
calibration sources. These types of determinations are also known as the alpha and beta index and are usually
employed as screening parameters for first assessment of total radioactive content.
The sample is acidified using nitric acid and heated. Water samples with low salt content can be thermally
concentrated by slow evaporation to improve the method sensitivity. An aliquot of the sample is transferred
into a liquid scintillation vial and a scintillation cocktail is added; scintillations from the vial are then measured
with a liquid scintillation counter having an alpha and beta discrimination device.
The counter is previously optimized with respect to required alpha and beta discriminator setting and then
calibrated against alpha and beta emitter certified reference solutions. In the data evaluation, no correction
for chemical quenching is applied, since the procedure is designed to provide samples with a relatively
constant quench level.
The sample shall be filtrated if suspended particles are present.
The detection limit depends on the test portion volume, the instrument used, the background count rate, the
detection efficiency and the counting time. The detection limit of the method described in this document, using
-1 -1
currently available liquid scintillation apparatus, is approximately 20 mBq·kg (α) and 100 mBq·kg (β),
-1
which is lower than the WHO criteria for safe consumption of drinking water 500 mBq·kg (α) and
-1
1 000 mBq·kg (β)[4]. This value can typically be achieved with a counting time of 500 min for a test sample
volume of 0,08 l.
The method does not account for radioiodine, Rn and its short-lived progeny and it is not suitable for
H measurement. The method is not suitable for C-14 either, present as carbonate form, which is a very
uncommon case.
When suspended matter is present in significant quantities, a filtration step is required before acidification.
5 Sampling
Sampling, handling and storage of the water shall be done as specified in ISO 5667-1, ISO 5667-3 and
ISO 5667-10 and guidance is given for the different types of waters in References [8][8] to[14] [14]. It is
important that the. The laboratory receivesshall receive a sample that is truly representative and that has
neithernot been damaged noror modified during transportation or storage.
Collect 0,1 l to 1 l of water in a plastic bottle (6.3.4(6.3.4)) in accordance with ISO 5667-1 and ISO 5667-3. If
necessary, filter the sample immediately after collection and before acidification. If possible, acidify
immediately with nitric acid (6.1.1(6.1.1)) to a value not lower than pH 1,7 ± 0,2 (7.1(7.1)) or pH 2,7 ± 0,2 if
thermal preconcentration is desired (7.2(7.2).). Verify the acidity by using a pH meter (6.3.3(6.3.3).).
NOTE Acidification of the water sample minimizes the loss of radioactive material from solution by adsorption. If
carried out before filtration, it desorbs radioactive material already adsorbed on to the particulate material.
The relatively low acidification of the sample does not ensure long-term preservation. The test sample should
preferably be prepared within seven days from collection. Groundwater is usually more stable than raw
waters (see ISO 5667-3).
6 Chemical reagents, certified reference solutions and equipment
6.1 Chemical reagents
Use only reagents of recognised analytical grade, except for the scintillation cocktail.
It is recommended to use acids and bases of trace metal grade or equivalent (a better purity grade can also be
employed).
6.1.1 6.1.1 Nitric acid, c(HNO ) = commercially available acid with a mass fraction of w(HNO ) = (65 %
3 3
to 70) %.
6.1.2 6.1.2 Ultrapure water, with a resistivity of more than 18,2 MΩ cm at 25 °C and total organic carbon
−1
less than 1 μg∙l .
Unless otherwise stated in this document, water refers to ultrapure water.
Water can contain detectable amounts of Rn and short-lived progeny. It is therefore strongly recommended
to boil water under vigorous stirring and let it stand for one day before use. Alternatively, use nitrogen flushing
for about 1 h for a 2 l sample.
6.1.3 6.1.3 Scintillation cocktail, commercially available scintillation cocktails suitable for alpha and
beta discrimination (e.g. diisopropylnaphthalene-based cocktails), water miscible.
6.1.4 6.1.4 Volatile organic solvents, methanol or ethanol.
6.2 Certified reference solutions
6.2.1 General
In general, the instrumental parameters (efficiency, alpha and beta optimum discrimination) depend on alpha
and beta energies, thus the choice of alpha and beta emitter certified reference solutions depends on
knowledge of the type of radioactive contaminant likely to be present in the waters being tested
[15]
(see ISO 9696[15] and Reference [16][16]).).
NOTE More information on metrological traceability can be found in ISO/IEC 17025.
6.2.2 Alpha emitting certified reference solution
The alpha emitting certified reference solution shall not contain any unexpected (e.g. decay products of short
half-life) detectable alpha and beta activity.
Uranium-236 is a convenient choice when waters are checked for their natural radioactivity content, as its
energy is close to the most widespread natural radionuclides (e.g. uranium and thorium isotopes, Ra) and
it is commercially available without decay products of short half-life. Details of the absence of any decay
product should be provided in order to warrant proper use. The source certificate should contain all relevant
information about radioactive impurities possibly present in the solution.
Americium-241 is commonly used when artificial radionuclide contamination is suspected. Plutonium-239
can be used as well in such circumstances.
6.2.3 Beta emitting certified reference solution
The beta emitting certified reference solution shall not contain alpha-emitting radioisotopes.
90 90 40
A Sr and Y mixture or K are commonly used. A potassium solution for atomic absorption spectrometry
has one arguable advantage, in that its specific activity can be calculated from established physical constants
and isotopic abundance data which are independent of the calibration procedures of a particular organization.
137 36
Other beta emitters, such as Cs or Cl, can also be used.
6.3 Equipment
6.3.1 6.3.1 Balance.
6.3.2 6.3.2 Hot plate with magnetic stirrer and stirring bar.
6.3.3 6.3.3 pH meter.
6.3.4 6.3.4 Wide-mouth high-density polyethylene (HDPE) sample bottles.
6.3.5 6.3.5 Liquid scintillation counter, with α and β discrimination option, preferably an ultra-low level
counter to achieve better detection limits.
6.3.6 6.3.6 Polyethylene scintillation vials, capacity 20 ml, such as polyethylene terephthalate (PET)
vials, low diffusion PET vials or polytetrafluoroethylene (PTFE) -coated polyethylene vials.
PTFE-coated polyethylene vials are the best choice of scintillation vials because they prevent both the
diffusion of the cocktail into the wall of the vial and the absorption of radon from the outer environment. Glass
vials generally degrade α and β discrimination.
7 Procedure
7.1 Direct counting
Transfer an aliquot of the water sample (6.3.1) of approximately 50 g (see 6.3.1,), m , into a pre-weighed
beaker. If the laboratory sample has not yet been acidified, acidify the aliquot using nitric acid (6.1.1(6.1.1))
to pH 1,7 ± 0,2 (verify with pH meter, 6.3.36.3.3).).
Cover the beaker and heat to approximately 80 °C while stirring for 30 min (6.3.2(6.3.2)) to remove the
dissolved Rn. Allow the aliquot to cool and weigh it again to account for the losses due to evaporation.
Record the mass as m . Where radon or other volatile species maycan be expected, this method cannot be
applied, according to the chapter 1 (scope):; other measurement need tomethods shall be used.
The necessary amount of acid is small (normally about 0,15 g for a 50 g sample) and its mass can be neglected.
7.2 Thermal preconcentration
-−1
A thermal preconcentration for soft water samples (e.g. dry residue less than 500 mg·l , as in most drinking
-
waters) can be applied to increase the sensitivity of the method. Hard waters (dry residue more than 500 mg·l
−1
) can give rise to salt precipitations or to a difficult homogenization with the scintillation cocktail.
Transfer an (6.3.1) aliquot of the water sample of approximately 200 g (see 6.3.1,), m , into a pre-weighed
beaker. Reweigh the beaker. If the laboratory sample has not yet been acidified, acidify the aliquot using nitric
acid (6.1.1(6.1.1)) to pH 2,7 ± 0,2 (verify with a pH meter).
Slowly evaporate the aliquot on a hot plate (6.3.2(6.3.2)) to a final quantity of approximately 20 g. Allow the
aliquot to cool to room temperature and weigh the concentrated aliquot. Record the mass as m . The pH of the
concentrated aliquot shall be 1,7 ± 0,2.
No residue (or no undissolved salts) should be observed, otherwise direct counting (7.1(7.1)) or smaller
preconcentration factors shall be applied.
If salt content of sample is unknown, an estimate of the dissolved solids is advisable. Any commonly used
technique (ege.g. conductivity) can be adopted.
7.3 Sample preparation
Transfer a weighed (Error! Reference source not found.(6.3.1)) test portion (7.1(Error! Reference source
not found. or Error! Reference source not found.7.2),), m , of the prepared aliquot into the scintillation vial.
Add the scintillation cocktail (Error! Reference source not found.(6.1.3)) and shake vigorously. Clean the
scintillation vial (Error! Reference source not found.(6.3.6)) external surface with either ethanol or
methanol (Error! Reference source not found.(6.1.4)) and a cloth. Calculate the exact mass, m, of the sample
analysed using Error! Reference source not found.Formula (1)::
𝑚 𝑚
1· 3
𝑚 = (1)
...