EN 17462:2021

SLOVENSKI STANDARD
01-julij-2021
Krma: metode vzorčenja in analize - Določevanje radionuklidnega joda-131, cezija-
134 in cezija-137 v krmi
Animal feeding stuffs: Methods of sampling and analysis - Determination of the
radionuclides Iodine-131, Caesium-134 and Caesium-137 in feed
Futtermittel: Probenahme- und Untersuchungsverfahren - Bestimmung der Radionuklide
Jod-131, Cäsium-134 und Cäsium-137 in Futtermittel
Aliments des animaux : Méthodes d’échantillonnage et d’analyse - Détermination des
radionucléides iode 131, césium 134 et césium 137 dans les matières premières et
aliments composés pour animaux
Ta slovenski standard je istoveten z: EN 17462:2021
ICS:
65.120 Krmila Animal feeding stuffs
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 17462
EUROPEAN STANDARD
NORME EUROPÉENNE
April 2021
EUROPÄISCHE NORM
ICS 65.120
English Version
Animal feeding stuffs: Methods of sampling and analysis -
Determination of the radionuclides Iodine-131, Caesium-
134 and Caesium-137 in feed
Aliments des animaux : Méthodes d'échantillonnage et Futtermittel: Probenahme- und
d'analyse - Détermination des radionucléides iode 131, Untersuchungsverfahren - Bestimmung der
césium 134 et césium 137 dans les matières premières Radionuklide Jod-131, Cäsium-134 und Cäsium-137 in
et aliments composés pour animaux Futtermittel
This European Standard was approved by CEN on 22 February 2021.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 17462:2021 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Symbols and abbreviations . 8
4.1 Symbols . 8
4.2 Abbreviations . 10
5 Principle . 11
6 Safety precautions . 11
7 Apparatus . 11
7.1 General . 11
7.2 Equipment for test portion preparation . 11
7.3 Containers to be used . 12
8 Procedure. 12
8.1 Calibration . 12
8.2 Test portion preparation . 15
8.3 Spectrum recording . 16
8.4 Spectrum analysis . 16
8.5 Quality assurance . 17
9 Expression of results . 18
9.1 Massic activity calculation . 18
9.2 Characteristic limits . 23
9.3 Precision . 24
9.4 Test report . 25
Annex A (informative) List of possible interfering gamma rays . 26
Annex B (informative) Example of uncertainty budget in gamma-ray spectrometry using an
HPGe detector . 27
Annex C (informative) Results of the collaborative trial . 28
Bibliography . 33

European foreword
This document (EN 17462:2021) has been prepared by Technical Committee CEN/TC 327 “Animal
feeding stuffs - Methods of sampling and analysis”, the secretariat of which is held by NEN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by October 2021, and conflicting national standards shall
be withdrawn at the latest by October 2021.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document has been prepared under a standardization request given to CEN by the European
Commission and the European Free Trade Association.
According to the CEN-CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
Introduction
131 134 137
This document describes a method for I, Cs and Cs massic activity determination (Bq/kg) in
animal feeding stuffs. It was initiated by Directorate General for Health and Food Safety (DG SANTE) of
the European Commission following the accident in the Fukushima Daiichi nuclear power plant in
March 2011. The event highlighted the need for standardized measurements of the three most common
radioactive contaminants following such type of nuclear accident.
The most commonly used method for identification and quantification of these radionuclides in animal
feeding stuffs samples is high-resolution gamma-ray spectrometry. As this is a secondary measurement
method based on analysis of photopeaks of the emitted gamma rays, care should be taken to use
appropriate energy and efficiency calibrations for the detector and test portion used. This method of
massic activity determination is described in the present document.
1 Scope
131 134
This document describes a method for determination of the massic activity (Bq/kg) of I, Cs and
Cs in animal feeding stuffs in monitoring laboratories.
General guidance on the preparation of feed samples and the measurement of the three radionuclides
131 134 137
I, Cs and Cs by high resolution gamma-ray spectrometry is provided. The current document aims
to be complementary to existing standards. More information on sample preparation, moisture content
determination and gamma-ray spectrometry can be found in specific standards referred to in this
document. For example, generic advice on the equipment selection, detectors and quality assurance for
gamma-ray spectrometry can be found in ISO 20042 [4].
The method was fully statistically tested and evaluated in a collaborative trial comprising five animal
131 134 137
feeding stuff samples for the radionuclides I, Cs and Cs. Details on the successfully tested
working range for each of the examined radionuclides are described in Annex C.
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 cited edition applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
EN ISO 662, Animal and vegetable fats and oils — Determination of moisture and volatile matter content
(ISO 662)
EN ISO 665, Oilseeds — Determination of moisture and volatile matter content (ISO 665)
EN ISO 712, Cereals and cereal products — Determination of moisture content — Reference method
(ISO 712)
EN ISO 6497, Animal feeding stuffs — Sampling (ISO 6497)
EN ISO 6540, Maize — Determination of moisture content (on milled grains and on whole grains)
(ISO 6540)
EN ISO 11929-1:2019, Determination of the characteristic limits (decision threshold, detection limit and
limits of the coverage interval) for measurements of ionizing radiation — Fundamentals and application
— Part 1: Elementary applications (ISO 11929-1)
ISO 771, Oilseed residues – Determination of moisture and volatile matter content
ISO 6496, Animal feeding stuffs — Determination of moisture and other volatile matter content
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN ISO 6497 and the following
apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at http://www.electropedia.org/
3.1
background
spectrum recorded by the gamma-ray detector when no sample is measured
Note 1 to entry: The spectral data, including full energy peaks, in such a spectrum is resulting from radioactive
decay occurring in the environment surrounding the detector (including the cosmic ray interactions) or in the
detector.
3.2
background continuum
events in the spectrum that form a smooth curve onto which the photopeaks are superimposed
Note 1 to entry: The continuum may arise from gamma-rays scattered inside the test sample or any surrounding
materials, from cosmic radiation or from radionuclides in the surrounding materials.
[SOURCE: ISO 20042:2019, 3.1 [4]]
3.3
blank sample
sample, liquid or solid, with very low to no activity for radiation of the same type and region of interest,
with a mass and a composition as close as possible to those of the test sample
[SOURCE: EN ISO 19581:2020, 3.1 [1]]
3.4
dead time
time during spectrum acquisition (real time) during which pulses are not recorded or processed
Note 1 to entry: Dead time is given by real time minus live time.
Note 2 to entry: The time is given in seconds.
[SOURCE: ISO 20042:2019, 3.5 [4]]
3.5
efficiency transfer
detection efficiency transfer
calculation that enables the user to establish the value of the detection efficiency for a given gamma-ray
peak in the spectrum of the test portion, when only the detection efficiency from an experimental
calibration with a reference source that may have a different composition, density and/or geometry
compared to the test portion is known
3.6
high resolution gamma-ray spectrometry
energy resolution obtained with a Ge(Li) or an HPGe detector
Note 1 to entry: This definition is specific to gamma-ray spectrometry.
3.7
laboratory sample
sample as prepared (from the lot) for sending to the laboratory and intended for inspection or testing
[SOURCE: EN ISO 6498:2012, 2.1.2 [2]]
3.8
live time
time during which pulses are processed during an acquisition (real) time
Note 1 to entry: The time is given in seconds.
[SOURCE: ISO 20042:2019, 3.12 [4]]
3.9
photopeak
full energy peak (FEP)
peak observed above the background continuum in a gamma-ray spectrum due to events that deposit
the full energy of the photon in the detector material, usually approximately Gaussian in shape
[SOURCE: ISO 20042:2019, 3.17 [4]]
3.10
real time
time taken to acquire a spectrum
Note 1 to entry: The time is given in seconds.
[SOURCE: ISO 20042:2019, 3.19 [4]]
3.11
sample holder
device that is specially designed to enable the placement of a given sample container in a well-defined
position on top of a specific detector
3.12
spectrometry system
complete assembly of the sensor and associated pulse-processing electronics that converts the gamma-
rays detected by the sensor into a pulse-height spectrum
[SOURCE: ISO 20042:2019, 3.22 [4]]
3.13
test portion
quantity of material drawn from the test sample (or from the laboratory sample if both are the same)
[SOURCE: EN ISO 6498:2012, 2.1.4 [2]]
3.14
test sample
subsample or sample prepared from the laboratory sample and from which test portions will be taken
[SOURCE: EN ISO 6498:2012, 2.1.3 [2]]
3.15
true coincidence summing
TCS
coincidence summing
cascade-summing
simultaneous detection of two or more gamma-rays in the spectrometry system, due to the emission of
a cascade of gamma-rays in the decay of a single nucleus in the test sample
[SOURCE: ISO 20042:2019, 3.24 [4]]
4 Symbols and abbreviations
4.1 Symbols
For the purposes of this document, the following symbols apply:
Symbol Name of quantity Unit
A activity of a reference radionuclide emitting photons of energy E in the calibration Bq
source, at the time of calibration
a annum (year), the tropical year which is approximately equal to 365,2422 d year
a massic activity at energy E of a radionuclide in the sample Bq/kg
m
a ; massic activity of Cs obtained using the gamma-ray of energy i, which is either Bq/kg
m,605
a 604,72 keV or 795,86 keV
m,796
'
massic activity of Cs based on the weighted mean calculation including the two Bq/kg
a
m
major gamma rays of this radionuclide
*
decision threshold Bq/kg
a
m
#
detection limit Bq/kg
a
m

true value of massic activity at energy E of a radionuclide in the sample Bq/kg
a
d day (1 day = 86 400 s) day
f factor to correct for gamma-ray attenuation within the test portion (self- -
att(E)
attenuation)
f factor to correct for decay between the reference time and the start of the -
d
measurement and during the measurement
NOTE 1  The latter is important for short-lived radionuclides like I.
f is the factor to correct for decay between the reference time and the start of the -
d1
measurement
f is the factor to correct for decay during the measurement -
d2
f composite correction factor for the gamma ray with energy E considering all -
E
necessary corrections as shown in Formula (6)
f factor to correct for geometry differences -
g
ftcs,E factor to correct for true coincidence summing effects -
NOTE 2  In this case, this is only applicable to 134Cs.
k coverage factor -
Symbol Name of quantity Unit
m quantity of the test portion kg
m corrected quantity of the test portion kg
c
m dry mass of the moisture content determination portion kg
d
m fresh mass of the test portion kg
f
m fresh mass of the moisture content determination portion kg
w
N number of gamma rays used for the calculation of massic activity for Cs -
n number of counts in the net area of the photopeak at energy E, in the background -
b,E
spectrum
n number of counts in the net area of the photopeak at energy E, in the test portion -
N,E
spectrum
P probability (per 100 decays) of the emission of a gamma ray with energy E by a -
E
radionuclide
NOTE 3  The probability can be expressed in percentage (%) or in absolute values.
−1
r net count rate in the full energy peak at energy E s
N,E
T temperature °C
t background spectrum live time s
b
t test portion spectrum live time s
g
t time elapsed between the reference time and the start of the measurement s
i
NOTE 4  It will have a negative value when the measurement was started before the
reference time and a positive value when the measurement was started after the reference
time.
t test portion spectrum real time s
r
t calibration spectrum live time s
s
t1/2 half-life of a radionuclide s
U(a ) expanded uncertainty with coverage factor k calculated as U = k × u Bq/kg
m
u(a ) standard uncertainty of the massic activity Bq/kg
m
u(a ); standard uncertainty of the massic activity calculated for the two most intense Bq/kg
m,605
gamma rays (604,72 keV and 795,86 keV) of Cs
u(a )
m,796
u(n ) uncertainty of the net number of counts in the photopeak at energy E in the -
b,E
background spectrum
u(n ) uncertainty of the net number of counts in the photopeak at energy E in the test -
N,E
portion spectrum
u(r ) uncertainty of the net count rate -
N,E
u random uncertainty component -
rand
u (A) relative uncertainty of the activity of a reference radionuclide emitting photons of -
rel
energy E in the calibration source, at the time of calibration

Symbol Name of quantity Unit
u (f ) relative uncertainty of the factor to correct for decay between the reference time -
rel d
and the start of the measurement and during the measurement
u (f ) relative uncertainty of the composite correction factor for the gamma ray with -
rel E
energy E considering all necessary corrections as shown in Formula (6)
u (f ) relative uncertainty of the factor to correct for true coincidence summing effects -
rel tcs,E
u (m) relative uncertainty of the quantity of the test portion -
rel
u (P ) relative uncertainty of the probability (per 100 decays) of the emission of a gamma -
rel E
ray with energy E by a radionuclide
u (r ) relative uncertainty of the net count rate -
rel N,E
u (ε ) relative uncertainty of the detection efficiency at energy E for the specific -
rel E
measurement geometry and detector used
u systematic uncertainty component -
sys
utot total uncertainty calculated based on random and systematic components -
u(w) total standard uncertainty for coverage factor w -
u (w) relative value of total standard uncertainty for coverage factor w -
rel
  standard uncertainty of a as a function of its true value Bq/kg
m
ua
( )
m
v ; v weighting factor for the calculation of massic activity of Cs using the two most -
605 796
intense gamma rays (604,72 keV and 795,86 keV)
w calibration factor -
ɛ detection efficiency at energy E for the specific measurement geometry and -
E
detector used
−1
λ decay constant of a radionuclide s
4.2 Abbreviations
ALARA As low as reasonably achievable
FEP Full energy peak
FWHM Full width at half maximum
HPGe High purity germanium
IEC International Electrotechnical Commission
ISO International Organization for Standardization
TCS True coincidence summing
5 Principle
A homogenous test portion is placed in a measurement container. The container is positioned in front of
a high energy resolution (e.g. high purity germanium) detector in a well-defined position. The full-
energy peaks of the emitted gamma particles present in the test portion are analysed and massic
131 134 137
activities of I, Cs and Cs are quantified using the high resolution gamma-ray spectrometry
technique. Appropriate energy and efficiency calibration shall be applied for each detector and sample
used.
6 Safety precautions
The optimization (ALARA) principle shall be applied at all times.
Handling of the samples should be performed according to the local safety regulations.
Personal protective equipment like laboratory coat, gloves, protective eyewear and personal dosimeter
shall be worn during the test portion preparation. The gloves shall be changed when the preparation is
finished to avoid cross-contamination.
Laboratory samples shall be stored in a cool and dark place, at a temperature not exceeding room
temperature and not lower than 0 °C. Perishable materials shall be kept at a temperature of
1 °C < T < 5 °C.
Care shall be taken as losses of iodine can occur if the material is not properly preserved. If presence of
gaseous iodine is suspected hermetically sealed containers shall be used and empty space or air pockets
between the sample and the lid of the container shall be avoided. Bound iodine can also easily become
volatile in the presence of microorganisms (due to methylation), in acidic environments or at
temperatures higher than 80 °C.
7 Apparatus
7.1 General
All equipment used during sample preparation shall be cleaned after each use to avoid cross-
contamination.
7.2 Equipment for test portion preparation
7.2.1 General
This document only provides guidance specific to its scope concerning the equipment for test portion
preparation. More details and a comprehensive description can be found in EN ISO 6498 [2].
7.2.2 Balance
In the test portion preparation process a balance or scale sensitive to 0,1 % of the mass of the test
portion and with a capacity of at least the wet mass of the test portion shall be used to determine the
mass.
7.2.3 Thermostatically controlled heating chamber
If results normalized to the dry mass are required, an oven or another suitable thermostatically
controlled heating chamber shall be used. The equipment shall be calibrated and capable of maintaining
the temperature needed to analyse the moisture content of the material with an uncertainty that is at
most 2 °C.
7.2.4 Equipment for particle size reduction and homogenization
Mills and mixers should be used to reduce the particle size and homogenize the test portion, in
particular if the particle size of the initial material is > 6 mm.
7.2.5 Equipment for handling dry powdered materials
An ion blower or other type of equipment should be used to reduce static electricity.
After the transfer of the test portion to the measurement container, a tapper or vibrating table could be
used to compact the test portion and equalize its height.
7.2.6 Gamma-ray spectrometry equipment
A gamma-ray spectrometer with high energy resolution (e.g. an HPGe) detector coupled to a pulse
processing, a data acquisition system and a computer shall be used to collect the spectra.
It is recommended to use detectors whose energy resolution (FWHM) is better than 2,2 keV (for the
60 137
Co peak at 1 332 keV) and with a peak/Compton ratio between 50 and 80 for Cs. For more
information, see IEC 61452 [5].
7.3 Containers to be used
7.3.1 Moisture content determination container
A container able to withstand the drying temperature shall be used if moisture content determination is
required. It shall be suitable for containing a portion of a test sample required by the relevant ISO
standard used for moisture content determination without loss of sample material while permitting
water to evaporate.
7.3.2 Measurement container
Guidance information on a proper container for the test portion is given in ISO 20042 [4].
If the measurement container is to be reused, it shall first be emptied, cleaned and checked for
radiopurity as it could have become contaminated by the previously measured test portion.
8 Procedure
8.1 Calibration
8.1.1 General
The gamma-ray spectrometry detector shall be calibrated for energy and peak detection efficiency. The
calibration should follow the requirements of IEC 61452 [5].
8.1.2 Energy calibration
The sources used for the energy calibration may be point sources of a single nuclide emitting gamma
rays of different energies (e.g. Eu), multiple nuclide point sources or a series of sources containing
radionuclides emitting one or more gamma rays.
Emphasis should be placed on the energy interval 364 keV to 911 keV, as the main gamma rays of both
the radionuclides in the scope of this document and the potentially interfering radionuclides (listed in
Annex A) have energies in that interval.
8.1.3 Detection efficiency calibration
The counting detection efficiency for a gamma-ray energy is affected by five major factors:
— the intrinsic detector efficiency;
— the position of the source in relation to the detector;
— the physical dimensions of the measurement container;
— the density, matrix composition and the filling height of the test portion;
— the shield (indirectly by minimizing interfering radiation or environmental background).
The experimental calibration of the detection efficiency should be performed using a reference volume
source (i.e. not a point source) measured in the same container and position as the test portion. The
properties of the reference volume source should be as similar as possible to those of the test portion.
To account for differences in their properties proper techniques for efficiency transfer should be
applied (see below).
As spiking can result in an inhomogeneous activity distribution preparation of a reference volume
source in the laboratory is only possible if a reliable and validated spiking procedure is available. Blank
material can be spiked with a multi-nuclide solution, several individual solutions containing suitable
radionuclides or a solution of a single nuclide emitting many gamma rays. Attention should be paid to
cover the region of interest (364 keV to 911 keV).
The net count rate (r ) shall be calculated using Formula (1).
N,E

t
g

nn−×
Nb,,E E

t
b

r = (1)
N,E
t
g
where
−1
r is the net count rate in the full energy peak at energy E, in s ;
N,E
n is the net number of counts in the peak, at energy E, in the test portion spectrum;
N,E
n is the number of net counts in the peak, at energy E, in the background spectrum;
b,E
is the test portion spectrum live time, in s;
t
g
is the background spectrum live time, in s.

t
b
The detection efficiency at the energy E (ε ) should be calculated according to Formula (2).
E
r
N,E
ε = (2)
E
AP× ××f f
EEd tcs,
where
ε is the detection efficiency at energy E for the specific measurement geometry and detector
E
used;
−1
r is the net count rate in the full energy peak at energy E calculated using Formula (1), in s ;
N,E
A is the activity of the reference radionuclide emitting photons of energy E in the calibration
source, at the time of the calibration, in Bq;
P is the absolute probability of the emission of a photon with energy E, per decay;
E
f is the factor to correct for decay between the reference time and the start of the
d
measurement and during the measurement;
f is the factor to correct for true coincidence summing effects.
tcs,E
Once the detection efficiencies for the radionuclides present in the reference volume source are
calculated, they should be plotted against the energy of the emitted photon. Then, an efficiency curve
should be constructed by suitable fitting [ISO/IEC/IEEE 12207] [6] (see Figure 1). Extrapolation is not
allowed.
Key
X energy [keV]
Y efficiency
Figure 1 — Example of detection efficiency calibration curve for silica gel spiked with a
multigamma solution plotted in a log-log diagram using polynomial fit
In case the detection efficiency calibration is performed using a source of a different geometry and/or
matrix composition than the test portion, it is possible to transfer the experimental detection efficiency
curve to the test portion geometry using calculations. A laboratory can develop its own semi-empirical
calculations for that purpose. It is also possible to compute the efficiency transfer using Monte Carlo
codes. General purpose codes as well as codes specifically dedicated to efficiency calculations in
gamma-ray spectrometry are available [7].
Absolute values of the detection efficiency can be calculated using Monte Carlo simulations only. It shall
however not be considered as full proof for a detection efficiency curve. This method should not be used
unless the computer model is very elaborate and validated by the laboratory. This validation shall be
based on comparison of the calculated efficiency values to the experimental ones for several energies
and different geometries [8].
Detection efficiencies for gamma-ray energies not present in the calibration source should be
interpolated using the formula obtained from the fitting of the calibration curve. The additional
uncertainty component due to the interpolation shall be accounted for in the uncertainty budget.
The same software and settings for analysis of the spectrum shall be used for both the test portion and
the calibration source.
When using a calibration source with cascading gamma-rays, true coincidence summing corrections
shall be applied.
8.2 Test portion preparation
General guidance on feed sample preparation is provided in EN ISO 6498 [2]. Guidance specific for
gamma-ray spectrometry samples can be found in ISO 20042 [4].
If the test portion mass is required to be corrected for its moisture content, taking into account the
sample matrix, a suitable procedure as described in ISO 6496 (General), EN ISO 662 (Animal and
vegetable fats and oils), EN ISO 665 (Oilseeds), ISO 771 (Oilseed residues), EN ISO 712 (Cereals and
cereal products) or EN ISO 6540 (Maize) shall be applied. Due to volatility of I in elevated
temperatures this test shall be conducted on a separate portion of the test sample material (i.e. not on
the test portion for the gamma-spectrometric measurements).
Test portion preparation should be carried out in a dedicated room other than the room in which the
measurement takes place, in order to avoid contamination of the instruments.
In order to minimize the correction factors, preferably the same type of measurement container and
sample size should be used for both the measurements of the test portion and the detection efficiency
calibration of the detector.
A hermetically sealed container shall be used if presence of volatile radionuclides (e.g. iodine in gaseous
form) is suspected in the laboratory sample. In such a case the lid shall be resting on the material and
formation of air pockets between the material and the lid shall be avoided.
In order to prepare a test portion for measurement the following steps shall be conducted:
1) The container shall be labelled with the test portion identification code;
2) The mass (including the lid) and inner dimensions of the empty container shall be recorded;
3) The test portion shall be transferred to the container;
4) The test portion filling height shall be recorded and compared with the filling height of the
efficiency calibration reference volume source (if it is used);
5) The container shall be closed with a lid or, in case of presence of volatile radionuclides, sealed;
6) Possible contamination on the outside of the container shall be avoided or removed, e.g. with tissue
pre-wetted with e.g. isopropanol or ethanol and left to dry;
7) The mass of the container with the test portion shall be recorded and the test portion mass
calculated;
8) Care shall be taken that the upper surface of the material in the container is horizontal and stable
(e.g. the container could be tapped on the benchtop, on a tapper or a vibrating table);
9) The density of the test portion material shall be calculated.
8.3 Spectrum recording
The measurement container shall be placed in front of the detector in a well-defined position,
preferably the same as the one used for the calibration source. Direct contact between the sample and
the detector should be avoided.
Start the measurement and acquire the spectrum for a counting time sufficient to obtain a detection
limit that fulfils the criteria for the method to be fit for purpose or to obtain the required accuracy.
For blank samples the counting time should be at least as long as the longest measurement time
considered for analysis.
131 134 137
Table 1 — Recommended nuclear data for I, Cs and Cs
Energy of main
a
Radionuclide Half-life P
E
gamma ray
%
keV
I 8,0233 (19) d 364,489 (5) 81,2 (5)
604,720 (3) 97,63 (8)
Cs 2,0644 (14) a
795,86 (1) 85,47 (9)
Cs 30,05 (8) a 661,657 (3) 84,99 (20)
NOTE 1  The number in parentheses is the numerical value of the combined standard uncertainty
(k = 1) and refers to the corresponding last digit (or two digits) of the quoted result.
NOTE 2  The data in this table are extracted from the DDEP database [9] on 12 February 2019.
a
"a" in this table refers to annum (year), the tropical year which is approximately equal to
365,2422 d.
131 134 137
Further information on the nuclear data of I, Cs and Cs can be found in the monographies of
BIPM [10], [11], [12] on the website of the Decay Data Evaluation Project (DDEP) [9].
8.4 Spectrum analysis
The photopeaks present in the spectrum in the energy range of interest should be identified by
application of the energy calibration described in 8.1.2. For each photopeak in the range of interest the
radionuclide to which it is assigned shall be properly identified and their corresponding net peak areas
determined.
The photopeaks identified and fitted by the software shall be subject to quality control. When deemed
necessary the fit should be adjusted manually.

Using spectrum analysis software the net area counts (n ) in each of the photopeaks of interest are
N,E
obtained by integrating the peak area and subtracting the background continuum in the region of
interest. In case the uncertainty of the net area counts obtained from the software is used in the
uncertainty budget a verification of this uncertainty component is required.
8.5 Quality assurance
The detector should be adequately shielded against natural background radiation. More detailed
information can be found in ISO 20042 [4].
The background should be measured before and after measuring of a series of test portions. The
duration of such a measurement should be at least as long as of the longest test portion measurement.
As it is advised in Annex A of ISO 20042:2019 [4], background spectra shall be periodically inspected in
detail to verify the stability of the background. The total count rate of each individual spectrum should
be obtained as well as the peak energies and peak areas. These values should be compared with the
previous background spectra and a curve of count rate as a function of time should be plotted in order
to monitor the stability of the background. In case of detector contamination appropriate cleaning of the
detector and/or sample holders should be performed. Detector contamination may also be monitored
by shorter measurements and by evaluating specific regions of interest in the spectrum.
In order to ensure the stability of the spectrometry system an appropriate quality assurance procedure
should be applied like e.g. to regularly measure a dedicated reference source that is always positioned
on the detector in the same way. Periodical measurements of a known source, of e.g. Eu, placed at a
well-defined position, are required for control of the stability of energy and efficiency calibration and
energy resolution of a detector. These data should be evaluated separately for low-, mid- and high-
energy peaks in the spectrum. In the presence of a radionuclide emitting more than one gamma line
with significant number of counts in the calibration source or Cs in the spectrum of the test portion
the results of activity calculations should be checked separately for each gamma line and compared. If a
significant difference is observed between the obtained results the reason for it should be investigated,
e.g. presence of interfering peaks (see Annex A), or background increase.
Whenever custom-made software is used for data collection and analysis it should be written and tested
according to relevant software standards such as ISO/IEC/IEEE 12207 [6].
In absence of peak(s) of the radionuclide(s) of interest in the spectrum the detection limit shall be
calculated following the formulae given in EN ISO 11929-1. If the relative uncertainty of the calibration
factor u (w) is below 15 % the detection limit is sufficiently well computed from the method proposed
rel
by Currie [13] and could be used as a pragmatic approach. The uncertainty component, u (w), is the
rel
total relative standard uncertainties for all factors making up the calibration factor w, as shown in
Formulae (3) and (4).
Blank samples should be prepared in the same location as the test portions in order to monitor the
contamination level of the preparation facilities. They should be placed in the same type of
measurement container and measured in the same geometry as the test portion.
Software programs for spectrum analysis automatically give the net peak area by subtracting the
background continuum under the peak. In case a peak at the same energy exists both in the background
and in the test portion spectra only the net number of counts in the peak should be subtracted. The
whole background spectrum shall not be subtracted from that of the test portion.
If a commercial software package is used for the activity calculations, it should be validated by
measuring reference samples preferably containing the same radionuclides as the ones under
investigation. The decay data that is used by the software shall be checked.
9 Expression of results
9.1 Massic activity calculation
9.1.1 General
The detection efficiency (ɛ ) for each of the peaks of interest shall be obtained from the efficiency curve
E
(8.1.3).
The gamma ray energies to be used for the calculations are given in Table 1. It is recommended to
consult the DDEP website [9] for the latest updates of the nuclear data.
The net count rate (r ) shall be calculated using Formula (1).
N,E
The massic activity (a ) shall be expressed in Bq/kg for each of the energies given in Table 1 (if present
m
in the test portion) and calculated using Formulae (3) and (4).
r
N,E
a rw× (3)
mN,E
P ×ε ××mf
EE E
with
w= (4)
P ×ε ××mf
EE E
where
a is the massic activity at energy E of a radionuclide in the sample, in Bq/kg;
m
P is the absolute emission probability per decay of the emission of a gamma ray with energy E
E
by the radionuclide in question;
ε is the detection efficiency at energy E for the specific measurement geometry and detector
E
used;
m is the quantity of the test portion, in kg;
f is the composite correction factor for the gamma ray with energy E considering all necessary
E
corrections;
w is the calibration factor.
In case when it is required to correct the quantity of the test portion (m) with its moisture content
Formula (5) shall be applied:
m
d
mm× (5)
cf

m
w
where
m is the corrected quantity of the test portion, in kg;
c
m is the fresh mass of the test portion, in kg;
f
m is the dry mass of the moisture content determination portion, in kg;
d
m is the fresh mass of the moisture content determination portion, in kg.
w
The corrected mass of the test portion (m ) should then in the Formula (4) replace the quantity of the
c
test portion (m).
=
= =
The composite correction factor (f ) shall be calculated using Formula (6).
E
(6)
f=ff× ××f f
E d att()E tcs,Eg
where
f is the correction factor for the gamma ray with energy E considering all necessary
E
corrections;
f is the factor to correct for decay between the reference time and the start of the
d
measurement and during the measurement;
NOTE 1  The latter is important for short-lived radionuclides like I.
f is the factor to correct for attenuation within the test portion (self-attenuation);
att(E)
f is the factor to correct for true coincidence summing;
tcs,E
NOTE 2  This is in this case only applicable to Cs.
f is the correction factor for geometry differences.
g
Note that f and f are often calculated using Monte Carlo codes and therefore obtained
g att(E)
simultaneously as one correction factor.
9.1.2 Decay correction (fd) calculation
The activity shall be corrected by the factor f using Formula (7).
d
1 1
f × (7)
d
ff
d1 d2
with
λt
i
f = e (8)
d1
and

λt
r

f = (9)
d2
−λt
r
1− e
where
f is the factor to correct for decay between the reference time and the start of the
d
measurement and during the measureme
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