prEN 17216

Construction products: Assessment of release of dangerous substances - Determination of activity of radium-226, thorium-232 and potassium-40 in construction products using semiconductor gamma-ray spectrometry

This document describes a test method for the determination of the activity of the radionuclides radium-226, thorium-232 and potassium-40 in construction products using semiconductor gamma-ray spectrometry.
This document describes sampling from a laboratory sample, sample preparation, and the sample measurement by semiconductor gamma-ray spectrometry. It includes background subtraction, energy and efficiency calibration, spectrum analysis, activity calculation with the associated uncertainties or the decision threshold and detection limit calculation, and the reporting of results.
The scope of this document is not product-specific. However, there are a limited number of product-specific components, such as the preparation of the laboratory sample and drying of the test portion. The method is applicable to samples from products consisting of single or multiple constituents.

Bauprodukte - Bewertung der Freisetzung von gefährlichen Stoffen - Messung der spezifischen Aktivität von Radium-226, Thorium-232 und Kalium-40 mittels Halbleiter-Gammaspektrometrie

Dieses Dokument beschreibt ein Prüfverfahren zur Bestimmung der spezifischen Aktivitäten der Radionuklide Radium-226, Thorium-232 und Kalium-40 in Bauprodukten durch Halbleiter-Gammaspektrometrie.
Dieses Dokument beschreibt die Probenahme einer Laborprobe, die Probenvorbereitung und die Messung der Probe durch Halbleiter-Gammaspektrometrie. Dazu gehört die Hintergrundsubtraktion, Energie- und Effizienzkalibrierung, Spektralanalyse, Berechnung der Aktivität mit den zugehörigen Unsicherheiten oder der Berechnung der Erkennungsgrenze und Nachweisgrenze und Angabe der Prüfergebnisse.
Der Anwendungsbereich dieses Dokuments ist nicht produktspezifisch. Allerdings gibt es eine begrenzte Anzahl produktspezifischer Komponente, wie die Vorbereitung der Laborprobe und die Trocknung der Prüfmenge. Das Verfahren eignet sich für Produktproben, die aus einzelnen oder multiplen Bestandteilen bestehen.

Produits de construction: Évaluation de l’émission de substances dangereuses - Détermination de l’activité du radium 226, du thorium 232 et du potassium 40 dans les produits de construction par spectrométrie gamma

No Scope Available

Gradbeni proizvodi - Ocenjevanje sproščanja nevarnih snovi - Določanje aktivnosti radija Ra-226, torija Th-232 in kalija K-40 z gama spektrometrijo

General Information

• Status: Not Published
• Publication Date: 13-Apr-2023
• ICS: 91.100.01 - Construction materials in general
• Technical Committee: CEN/TC 351 - Construction Products - Assessment of release of dangerous substances
• Drafting Committee: CEN/TC 351/WG 3 - Radiation from construction products
• Current Stage: 4060 - Closure of enquiry - Enquiry
• Start Date: 31-Aug-2023
• Due Date: 18-Feb-2022
• Completion Date: 31-Aug-2023
• Directive: 305/2011 - Regulation (eu) No 305/2011 of the European Parliament and of the Council of 9 march 2011 laying down harmonised conditions for the marketing of construction products and repealing council directive 89/106/eec
• Mandate: M/366 - Concerning the execution of standardisation work for the development of horizontal standardised assessment methods for harmonized approcaches relating to dangerous substances under the construction products directive (CPD)
• Ref Project: oSIST prEN 17216:2023 - Construction products: Assessment of release of dangerous substances - Determination of radium-226, thorium-232 and potassium-40 activity using gamma-ray spectrometry

Relations

• Revises: CEN/TS 17216:2018 - Construction products - Assessment of release of dangerous substances - Determination of activity concentrations of radium-226, thorium-232 and potassium-40 in construction products using semiconductor gamma-ray spectrometry
• Effective Date: 10-Jun-2020

Overview

The European Standard prEN 17216:2023 provides a comprehensive test method for assessing the activity of radionuclides radium-226 (Ra-226), thorium-232 (Th-232), and potassium-40 (K-40) in construction products using semiconductor gamma-ray spectrometry. Prepared by CEN Technical Committee 351, this document supersedes the previous CEN/TS 17216:2018 and supports harmonized product safety evaluations under the Construction Products Directive.

The standard focuses on a non-product-specific methodology for:

• Sampling from laboratory samples,
• Sample preparation including drying,
• Measurement using semiconductor gamma-ray spectrometry,
• Spectrum analysis with background subtraction and calibration,
• Calculation of radionuclide activity alongside uncertainties, decision thresholds, and detection limits,
• Reporting results in a standardized format.

This approach ensures reliable assessment of the release of dangerous substances, specifically radioactive elements, vital for regulatory compliance and product certification.

Key Topics

Sampling and Sample Preparation

• Guidelines for obtaining representative laboratory samples or sub-samples.
• Preparation of test specimens, including crushing and drying, tailored to the product but within standardized procedures.
• Ensures homogeneity and proper handling to reflect intrinsic radiological properties of the material.

Semiconductor Gamma-Ray Spectrometry

• Principle analytical technique used for determining radionuclide activity.
• Includes detailed processes for energy and efficiency calibration.
• Methods to correct for background radiation and instrument dead time.
• Use of calibration sources with known activity to ensure measurement accuracy.

Data Processing & Analysis

• Spectrum analysis techniques to identify characteristic gamma-ray peaks for Ra-226, Th-232, and K-40.
• Calculation of activity concentration expressed in becquerels per kilogram (Bq/kg).
• Determination of standard uncertainty, decision thresholds, and detection limits to quantify measurement confidence.
• Use of correction factors, such as dead-time, decay, and attenuation corrections, to refine results.

Reporting and Documentation

• Requirements for comprehensive test reports documenting sampling conditions, measurement parameters, calibration data, and final activity results.
• Facilitates traceability and compliance verification for CE marking and conformity assessment.

Applications

The prEN 17216:2023 standard is critically applied in:

• Construction Material Testing
  Assessment of raw materials or finished construction products containing natural radionuclides ensures compliance with health and safety regulations.

• Regulatory Compliance
  Supports CE marking processes by providing validated radionuclide activity data required under European directives for construction products.

• Environmental Protection and Radiation Safety
  Enables manufacturers to monitor and control the release of radioactive substances, reducing exposure risks to workers and end-users.

• Quality Control and Product Certification
  Laboratories use this method for routine testing and verification of construction materials before market release.

• Research and Development
  Assists innovation in building materials by benchmarking radiological properties during product development stages.

Related Standards

• EN ISO 20042:2021 – Measurement of radioactivity - Generic test method for gamma-ray emitting radionuclides using gamma-ray spectrometry, serving as a normative reference for calibration and measurement principles.

• EN ISO 18589 Series – Procedures for environmental radiation measurement which align with parts of the sampling and analysis methodology.

• NEN 5697 – Specific methodologies for sample handling and radionuclide measurement, complementing the procedures described in prEN 17216.

• EN 16687:2023 – Referenced for definitions related to sampling, test specimen preparation, and calibration source terminology.

This suite of standards works collectively to ensure robust, harmonized approaches to radionuclide activity determination in construction materials, underpinning safety and market acceptance within the EU.

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Keywords: prEN 17216, radium-226 activity, thorium-232 activity, potassium-40 activity, construction products, gamma-ray spectrometry, semiconductor detectors, radionuclide activity measurement, release of dangerous substances, construction material testing, radiation safety, CE marking compliance, CEN standard, building materials radioactivity assessment.

Standards Content (Sample)

SLOVENSKI STANDARD
01-julij-2023
Gradbeni proizvodi - Ocenjevanje sproščanja nevarnih snovi - Določanje
aktivnosti radija Ra-226, torija Th-232 in kalija K-40 z gama spektrometrijo
Construction products: Assessment of release of dangerous substances - Determination
of radium-226, thorium-232 and potassium-40 activity using gamma-ray spectrometry
Bauprodukte - Bewertung der Freisetzung von gefährlichen Stoffen - Messung der
spezifischen Aktivität von Radium-226, Thorium-232 und Kalium-40 mittels Halbleiter-
Gammaspektrometrie
Ta slovenski standard je istoveten z: prEN 17216
ICS:
13.020.99 Drugi standardi v zvezi z Other standards related to
varstvom okolja environmental protection
17.240 Merjenje sevanja Radiation measurements
91.100.01 Gradbeni materiali na Construction materials in
splošno general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
June 2023
ICS 91.100.01 Will supersede CEN/TS 17216:2018
English Version
Construction products: Assessment of release of
dangerous substances - Determination of radium-226,
thorium-232 and potassium-40 activity using gamma-ray
spectrometry
Bauprodukte - Bewertung der Freisetzung von
gefährlichen Stoffen - Messung der spezifischen
Aktivität von Radium-226, Thorium-232 und Kalium-
40 mittels Halbleiter-Gammaspektrometrie
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 351.
If this draft becomes a European Standard, 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.

This draft European Standard was established by CEN 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, Türkiye and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2023 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 17216:2023 E
worldwide for CEN national Members.

Contents Page
European foreword . 4
Introduction . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Symbols and abbreviations . 8
5 Principles of the test method . 11
6 Sampling and sample preparation . 11
6.1 Sampling scheme. 11
6.2 Sampling and sub-sampling . 12
6.3 Test specimen/test portion preparation . 13
7 Test procedure . 16
7.1 General. 16
7.2 Measurement . 16
8 Processing the test data . 19
8.1 General. 19
8.2 Analysis of the spectrum . 20
8.3 Calculating activity concentration . 20
8.4 Standard uncertainty. 22
8.5 Decision threshold . 24
8.6 Detection limit . 25
9 Test performance . 26
10 Test report . 27
Annex A (normative) Method for the determination of the radon leakage rate of a test specimen
container . 28
A.1 Principle . 28
A.2 Apparatus, equipment and reagents. 28
A.3 Test . 28
A.4 Processing experimental data . 29
Annex B (normative) Preparation of calibration sources and determination of detection
efficiency . 32
B.1 Principle . 32
B.2 Apparatus, equipment and reagents. 32
B.3 Standardized calibration sources . 32
B.4 Determination of the detection efficiency . 35
Annex C (normative) Method for the determination of the massic activity in a product
containing multiple constituents . 37
Annex D (informative) Complementary photopeaks to verify the activity concentration in the
test specimen . 38
Annex E (informative) Method for the determination of the correct number of pulses in a
photopeak (only to be used for single peaks) . 39
Annex F (informative) Performance data . 40
Bibliography . 41

European foreword
This document (prEN 17216:2023) has been prepared by Technical Committee CEN/TC 351
“Construction products: Assessment of release of dangerous substances”, the secretariat of which is held
by NEN.
The document is currently submitted to the CEN Enquiry.
The document will supersede CEN/TS 17216:2018.
This document has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association.
The main changes compared to the previous edition are as follows:
— Transfer of technical specification into European Standard;
— Addition of validation data from interlaboratory validation on repeatability and reproducibility (see
Clause 1, Clause 9 and Annex F); [to be completed for 2nd CEN Enquiry]
— Updating of normative and informative cross-references.
Introduction
This document is a European Standard developed under Mandate M/366 issued by the European
Commission in the framework of the “Construction Products Directive” 89/106/EEC. This document
addresses the part of Mandate M/366 which provides for the preparation of horizontal
measurement/test methods for the determination of the activity of the radionuclides radium-226,
thorium-232 and potassium-40 in construction products using gamma-ray spectrometry.
Mandate M/366 is a complement to the product mandates issued by the European Commission to CEN
under the Construction Products Directive (CPD). The harmonized product standards (hEN) developed
in CEN under mandates (and ETAs developed in EOTA for products or kits) specify construction
product(s) as placed on the market and address their intended conditions of use.
The information produced by applying this document can be used for purposes of CE marking and
evaluation/attestation of conformity. Product specification, standardization of representative sampling
and procedures for any product-specific laboratory sample preparation are the responsibility of product
TCs and are not covered in this document.
This document supports existing regulations and standardized practices and is based on methods
described in standards such as EN ISO 10703, EN ISO 18589-2, EN ISO 18589-3 and NEN 5697. In
summary, this document describes the following:
— sampling, sub-sampling and test specimen preparation;
— measurement by gamma-ray spectrometry;
— background subtraction, energy and efficiency calibration, spectrum analysis;
— calculation of activities with associated uncertainties;
— reporting of results.
Determination of the activities is done by gamma-ray spectrometry. Procedures for all stages of the
analytical process are provided in this document. Although the tested sample rarely reflects a product’s
form under its intended conditions of use, the measured activity concentration is an intrinsic property of
the product. It does not vary with the construction product’s form. Consequently, the test results reflect
the radiological content of the product under its intended use. The document is intended to be non-
product-specific in scope. However, there are some limited elements related to the sample preparation
that are product-specific.
1 Scope
This document describes a test method for the determination of the activity of the radionuclides radium-
226, thorium-232 and potassium-40 in construction products using semiconductor gamma-ray
spectrometry.
This document describes sampling from a laboratory sample, sample preparation, and the sample
measurement by semiconductor gamma-ray spectrometry. It includes background subtraction, energy
and efficiency calibration, spectrum analysis, activity calculation with the associated uncertainties or the
decision threshold and detection limit calculation, and the reporting of results.
The scope of this document is not product-specific. However, there are a limited number of product-
specific components, such as the preparation of the laboratory sample and drying of the test portion. The
method is applicable to samples from products consisting of single or multiple constituents.
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.
EN ISO 20042:2021, Measurement of radioactivity - Gamma-ray emitting radionuclides - Generic test
method using gamma-ray spectrometry (ISO 20042:2019)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
3.1
blank
test result obtained by carrying out the test procedure with an equivalent volume of demineralised or
distilled water instead of the test portion
, 3.3.4.1]
[SOURCE: EN 16687:2023
3.2
calibration source
sample with known radioactivity concentration and material properties that corresponds to the volume
and geometry of the test specimen
[SOURCE: EN 16687:2023 , 3.3.4.2]
3.3
crushed material
sample material prepared by crushing (a part) of the laboratory sample
[SOURCE: EN 16687:2023 , 3.3.4.4]

Under preparation. Stage at the time of publication: FprEN 16687:2023.
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: EN ISO 20042:2021, 3.5]
3.5
laboratory sample
sample or sub-sample(s) sent to or received by the laboratory
[SOURCE: EN 16687:2023 , 3.2.2.1 – modified, Notes to entry removed]
3.6
live time
time during which pulses are processed during an acquisition (real) time
Note 1 to entry: The time is given in seconds.
Note 2 to entry: Live time is the counting time corrected for the dead time.
[SOURCE: EN ISO 20042:2021, 3.12]
3.7
test portion
amount of the test sample taken for testing/analysis purposes, usually of known dimension, mass or
volume
[SOURCE: EN 16687:2023 , 3.2.2.3 – modified, Examples removed]
3.8
test sample
sample, prepared from the laboratory sample, from which test portions are removed for testing or for
analysis
[SOURCE: EN 16687:2023 , 3.2.2.2]
Note 1 to entry: From the test sample a test portion is removed for determining the correction factor for dry mass,
and one or multiple test specimen(s) are removed for radiation testing.
3.9
test specimen
test portion specially prepared for testing in a test facility in order to determine the radiation behaviour
of the product under intended conditions of use
[SOURCE: EN 16687:2023 , 3.2.2.4 – modified to read ‘determine’ instead of ‘simulate’; Examples
removed]
3.10
test specimen container
holder shaped like a beaker or a vessel that can be sealed and that is used to make determinations on the
test specimen
[SOURCE: EN 16687:2023 , 3.3.4.5]
4 Symbols and abbreviations
For the purposes of this document, the following symbols, names of quantities and units apply
Symbol Name of quantity Unit
A activity of the standardized calibration source j at energy E Bq
i;j i
a massic activity of radionuclide i Bq/kg
i
a massic activity of radionuclide i in the test specimen l Bq/kg
i;l
#
detection limit of radionuclide i of test specimen l Bq/kg
a
il;
*
decision threshold of radionuclide i of test specimen l Bq/kg
a
il;
E energy used for determining radionuclide i keV
i
f attenuation correction factor –
f true-summing correction factor –
f dead-time correction factor –
f decay correction factor –
f sample versus reference source positioning/height correction –
f is the mass fraction of the constituent j; –
j
i, j, l ordinals to indicate radionuclides, materials and samples –
k uncertainty coverage factor –
k uncertainty coverage factor with a default value of 1,65 at α = 0,05 –
1−α
k uncertainty coverage factor with a default value of 1,65 at β = 0,05 –
1−β
m dry mass of the test portion kg
d
m mass of the material constituent j per m of the construction product kg
j
m mass of matrix material j kg
j;mat
m mass of sub sample l of standardized material j kg
j;l;stand
m mass of the test specimen l kg
l
m fresh mass of the test portion kg
w
N corrected number of pulses in the photopeak –
N number of pulses collected in channel q –
q
average number of pulses per channel before the peak –
N
b
Symbol Name of quantity Unit
average number of pulses per channel after the peak –
N
f
N net number of pulses in the photopeak that corresponds to energy E of –
i;j i
standardized calibration source j
N number of pulses that is collected in the continuum under the photopeak when –
cont;l
counting the test specimen l
N number of pulses that is collected in the continuum under the photopeak with –
cont;i;j;mat
energy E of matrix material j
i
N number of pulses that is collected in the continuum under the photopeak with –
cont;i;j;k;stand
energy E of sub sample k of standardized material j
i
N total number of pulses that is collected in the channels belonging to the –
tot;i;j;mat
photopeak with energy E of matrix material j
i
N total number of pulses that is collected in the channels belonging to the –
tot;i;j;k;stand
photopeak with energy E of sub sample k of standardized material j
i
N total number of pulses that is collected in the channels belonging to the –
tot;l
photopeak when counting the test specimen l
n number of test specimens –
P gamma-ray-emission probability at energy E –
i i
p , p , p free parameters used in an e-power formula –
1 2 3
−1
R counting rate of the blank that is determined from the number of pulses that is s
cont;0
collected in the continuum under the photopeak
−1
R counting rate of the test specimen l that is determined from the number of s
cont;l
pulses that is collected in the continuum under the photopeak
−1
R corrected counting rate of the blank s
cor;0
−1
R corrected specific counting rate of matrix material j at energy E (s·kg)
cor;i;j;spec;mat i
−1
R average specific corrected counting rate of all subsamples k of (s·kg)
cor;i;j;spec;stand
standardized material j at energy E
i
−1
R corrected specific counting rate of sub sample l of standardized material j at (s·kg)
cor;i;j;l;spec;stand
energy E
i
−1
R corrected counting rate of the test specimen l that is determined for the s
cor;l
photopeak
−1
R corrected counting rate in spectrum v of the tested container j s
cor;j;v
−1
R total counting rate of the blank that is determined from the total number of s
tot;0
pulses that is collected in the channels belonging to the photopeak
−1
R total counting rate of the test specimen l that is determined from the total s
tot;l
number of pulses that is collected in the channels belonging to the photopeak
S total radon production in the building material Bq/s
t live time s
t live time of the blank s
Symbol Name of quantity Unit
t live time of the calibration source j s
j
t live time of matrix material j s
j;mat
t live time of sub sample l of standardized material j s
j;l;stand
t live time of the test specimen l s
l
t live time when measuring the radon leakage of the beaker s
L
t live time of the gas sample in spectrum w s
w
−1
up1 uncertainty in the free parameter p1 of the radon leakage test s
u external uncertainty of the mass activity of radionuclide i Bq/kg
i;ext
u internal uncertainty of the mass activity of radionuclide i Bq/kg
i;int
u uncertainty of the massic activity of radionuclide i from counting of the test Bq/kg
i;l;R
specimen l
u uncertainty of the massic activity of radionuclide i from counting of the test Bq/kg
i;R
specimen(s)
u total uncertainty of the massic activity of radionuclide i Bq/kg
i,tot
V sample volume m
v spectrum number, ascending from 1 to 10 –
w calibration factor for energy E for the conditions used in testing the test Bq∙s/kg
i;l i
specimen l
α probability of a first order error with a default value of 0,05 –
β probability of a second order error with a default value of 0,05 –
−1
εi;j radionuclide-specific counting efficiency for energy Ei and the standardized (Bq·s)
calibration source j
−1
ε radionuclide-specific counting efficiency for energy E and a counting (Bq·s)
i;l i
sample with mass m
l
η correction factor for dry mass of the test specimen –
−1
λL radon leakage rate (of the test specimen container) s
−1
λ decay constant of radon-222 s
Rn
−6 −1
NOTE λ = 2,1 × 10 s .
Rn
ν relative external uncertainty of the corrected specific counting rate of –
i;j;ext
standardized material j at energy E
i
νi;j;int relative internal uncertainty of the corrected specific counting rate of –
standardized material j at energy E
i
ν relative uncertainty due to radon-222 leakage from the test specimen –
L
container
ν relative uncertainty of the activity of radionuclide i associated with the term w –
i;w
ν relative uncertainty in the counting efficiency of radionuclide i –
i;ε
5 Principles of the test method
The activity of the gamma-ray emitting radionuclides in construction products are determined using
gamma-ray spectrometry. Activity content is a material property independent from the physical form of
a construction product.
The activity of gamma-ray emitting radionuclides present in the test specimen is based on the analysis of
the energies and the peak areas obtained from the full-energy peaks of the gamma-ray lines in the
spectrum.
The test method requires accurate energy and efficiency calibration. Calibration methods presently used
in the laboratories can be applied, these shall be accompanied with a determination of the uncertainty.
Selected gamma-ray lines are specified to determine the relevant radionuclides.
The activity is determined by measuring a sample held in a container with a known geometry. This
determination, requiring as it does a test specimen of granular material, will only rarely reflect a
product's form under its intended conditions of use. Nevertheless, as the massic activity is an intrinsic
material property, it will reflect the massic activity under its intended conditions of use.
For radium-226 and thorium-232 the activity is determined using a progeny nuclide, while for potassium-
40 the activity is determined directly. In case the activity is determined using a progeny nuclide, a secular
equilibrium between the progeny nuclide and its originating nuclide shall be established. To reach
equilibrium between radium-226 and its progenies, the test specimen is stored in a radon-tight container
for a period of at least three weeks.
Despite the required waiting time of three weeks a disequilibrium in the thorium-232 decay chain can be
present. Such disequilibrium is caused by different dissolution ratios between thorium and radium, in
combination with its particular hydrogeological history or industrial processing. In case of such
disequilibrium the thorium-232 activity is approximated by the activity of radium-228 or thorium-228.
NOTE 1 Thorium-232 with a half-life of 1,41 × 10 years is the parent nuclide of the thorium decay chain.
Thorium-232 emits a 63,81 keV gamma ray with an emission probability of 0,263 %. It overlaps with the 63,28 keV
gamma ray emitted by thorium-234 with an emission probability of 4,1 %. Thus thorium-232 cannot be determined
directly by gamma-ray spectrometry. Determination through its progeny radionuclides actinium-228, lead-212 and
thallium-208 can be performed correctly only if these radionuclides are in radioactive equilibrium with thorium-
232.
NOTE 2 Where the activity of thorium-228 and radium-228 is significantly different, alternative measurement
techniques or procedures to determine the thorium-232 activity more accurately are available but are outside the
scope of this document.
6 Sampling and sample preparation
6.1 Sampling scheme
A flowchart of the sampling is presented in Figure 1 in support of the relevant definitions given in
Clause 3.
Figure 1 — Diagram of the sample scheme
6.2 Sampling and sub-sampling
6.2.1 General
The method starts with a laboratory sample received by the laboratory. For the preparation of the
laboratory sample the following considerations should be taken into account:
a) For general guidance on sampling and sampling procedures for the making of a laboratory sample
reference should be made to CEN/TR 16220;
b) For construction products consisting of multiple constituents, a laboratory sample containing all of
the material constituents can be put forward for testing. Alternatively, each of the constituents can
be sent for testing individually. In that case the massic activity in the construction product shall be
calculated using the procedures described in Annex C (normative);
c) For construction products where blending of the various material constituents results in a change of
material composition or loss of weight, the calculation of the massic activity should consider the
composition of the construction product in its final state;
d) Where a cement-based concrete laboratory sample is prepared from a fresh, wet concrete, reference
should be made to the sampling procedures in EN 12350-1 and the production of hardened
specimens in EN 12390-2. These procedures are additional to the sampling procedures described in
CEN/TR 16220.
A representative portion of the laboratory sample is crushed to make the test sample. For the materials
described in 6.3.2.1, no crushing is needed. From the test sample, test portions are taken for general
analytical testing and as a test specimen on which to perform radiation testing.
6.2.2 Sub-sampling from the laboratory sample
Randomly take some sub-samples from the laboratory sample. The random sub-samples shall contain
sufficient material to prepare a minimum of one test specimen and a test portion for general analytical
testing.
6.3 Test specimen/test portion preparation
6.3.1 Apparatus and ancillary materials
6.3.1.1 Crushing apparatus, used to obtain a test sample with particle sizes of no more than 2 mm,
such as for example a mortar or a ball mill.
6.3.1.2 Sieve, with apertures which retain particles of more than 2 mm.
6.3.1.3 Calibrated balance, with a measurement uncertainty not more than 0,1 % for the typical
mass of the test sample, test portion and test specimen.
6.3.1.4 Mechanical compacting device (recommended), for compacting the granular content in
the test specimen container, such as for example a vibrating table.
6.3.1.5 Test specimen container, suited for gamma-ray spectrometry with a preselected volume
and geometry. The container should have the following characteristics:
a) be made of materials impermeable to radon;
NOTE Polymer materials suitable for use are high density polyethylene (HDPE) and polyethylene terephthalate
(PET). Note that Marinelli beakers are also made from polypropylene (PP), which is not always radon
impermeable.
b) be made of materials with low absorption of gamma radiation;
c) preferably have volumes adapted to the shape of the detector for maximum gamma-ray detection
efficiency; To decrease self-absorption effects, the filling height of the content shall be minimized;
d) be watertight and chemically inert;
e) have a wide opening to facilitate filling;
f) be resistant to mechanical impacts;
g) a transparent container should be selected in order to verify easily that the content of the container
is similar to the geometry of the established calibration.
Marinelli beakers are recommended for coaxial detectors. For planar detectors, cylindrical geometries
are recommended. Alternatively, other size containers can be selected to cover for a wide range of
densities and expected activities. The filling height, size and type of container should be selected to
maximize the detection efficiency, without compromising the representativeness of the test specimen.
6.3.1.6 Closing lid, that can be used to cover the test specimen container without any air pockets
after it is filled with the test specimen.
6.3.1.7 Sealant, for example, acrylic paste, a two-component epoxy adhesive, a wide insulation tape
with surface degreaser, or a paraffin disk with liquid paraffin.
6.3.1.8 Test beaker, for determination of dry matter content, with a volume of not more than 250 ml.
The test beaker shall be able to contain the required amount of sample material spread evenly on the
bottom allowing the water to evaporate and shall withstand the temperature required for drying.
6.3.2 Preparation of test portion and test specimen
6.3.2.1 General
Laboratory samples, or sub-samples taken there from, require no further preparation when they are
homogeneous in terms of chemical composition and activity concentration and when the test sample
geometry fits the test specimen container appropriately. This is the case for granular materials or
powders with a particle size less than 2 mm (cement, fly-ash, powdered gypsum, etc.), or for flexible
materials (mineral wool, etc.).
In all other cases, the test samples shall be prepared by crushing it:
a) Crush test samples to a maximum particle size of 2 mm using the crushing apparatus described in
6.3.1.1.
If sample units are too large to be inserted in the crushing apparatus, take a representative sub-
sample and break the units into smaller pieces using appropriate means, not introducing
contamination.
Ideally, dry procedures for such size reduction are used, but the use of wet-sawing is permitted. In
this case, dry the samples until the dry mass is obtained in a similar way as given in 6.3.2.2 and 7.2.3.3
before performing the test.
b) Sieve the crushed material to ensure that the size of all particles is not more than 2 mm. If necessary,
repeat crushing from step a).
c) Homogenize the sieved material, using a mixer or manually with spoon.
6.3.2.2 Test specimen for determination of activity concentration
Prepare a minimum of one test specimen.
If there are indications that the activity might not be uniformly distributed in the test sample or test
specimen it is recommend to prepare at least three test specimens. This can occur if the activity is not
uniformly distributed along the range of particle sizes.
a) Determine the radon leakage of the test specimen container in accordance with Annex A (normative).
b) Clean the container and weigh the empty test specimen container, together with the lid.
c) Fill the test specimen container.
The test specimen can be dried before filling the container as described in 7.2.3.3. In that case no
correction for dry weight shall be applied, and the preparation of a test portion as described in 6.3.2.2
and the subsequent drying described in 7.2.3.3 shall not be applied.
1) Fill test specimen container incrementally up to the same level corresponding with the
established calibration.
2) Vibrate the test specimen container or carefully tap the test specimen container after addition of
each increment to achieve a constant compacted sample.
d) Place the lid on, or in, the test specimen container such that it is resting on the material.
NOTE Figure 2 shows various examples of test specimen container shapes and lids.

Figure 2 — Sketch of various test specimen containers with lid and crushed material
e) Clean the outside of the container to remove any excess material left adhering from the filling
process.
f) Weigh the test specimen container plus test specimen and lid, and calculate the mass of the test
specimen by subtracting the mass of the test specimen container and lid from the total mass.
g) Seal the lid to the test specimen container so that it is radon-tight.
Sealing the edges where they join the lid on the test specimen container has proven to be suitable.
Before sealing, ensure the corresponding surfaces of the container and the lid are degreased. Then
glue or use an insulation tape. In case of insulating tape use 3 layers (without wrinkles) tightly glued
along the perimeter of the container-lid joint. An alternative method is the use of a paraffin disk with
liquid paraffin. In that case the remaining void should be filled with liquid paraffin until the test
specimen container is completely full. The lid should be screwed on while the paraffin is liquid.
h) Store the test specimen in the container for at least three weeks before performing the test, to allow
radon-222 and its progeny to equilibrate with its parent nuclide radium-226.
6.3.2.3 Test portion for determination of dry matter content
Prepare a single test portion in the following manner if the test specimen was not dried (as in 7.2.3.3)
prior to filling the test specimen container.
a) Weigh the empty test beaker to the nearest 0,1 % of its mass.
It is recommended to use a glass weighing bottle that can be closed in order to minimize re-
absorption of moisture during sample manipulation.
b) Add a test portion to the test beaker, with a recommended weight of approximately 10 g.
Consider more accurate weighing of the test beaker in case the weight of the test beaker is more than
the weight of the test portion.
c) Weigh the test beaker plus test portion to the nearest 0,1 % of the total mass.
d) Obtain the mass (m ) of the test portion by subtracting the mass of the test beaker from the combined
w
mass of the beaker plus test portion.
e) Carry out the determination of the dry matter content in accordance with 7.2.3.3.
7 Test procedure
7.1 General
The gamma radiation emitted from the test specimen is measured using a gamma-ray detector. The test
measurements shall be carried out in accordance with 7.2. It is recommended that the quality of testing
is validated by participation in interlaboratory comparisons and/or in recognized proficiency testing
schemes.
7.2 Measurement
7.2.1 Apparatus, software and calibration standards
7.2.1.1 Standardized efficiency calibration sources.
7.2.1.2 Energy calibration source(s), with gamma-ray energies spread over the interval
determined by the main peaks of interest.
7.2.1.3 Drying oven, capable of maintaining a set temperature within ± 2 °C.
7.2.1.4 Desiccator.
7.2.1.5 Semiconductor detector.
Semiconductor gamma-ray spectrometer, consisting of a detector with a high energy resolution (for
example a high-purity germanium detector), a pulse processing and data acquisition system (including
software) with at least 4 096 channels.
It is recommended to use detectors with an energy resolution (FWHM) better than 2,2 keV (for the Co
peak at 1 332 keV) and with a peak/Compton ratio between 50 and 80 for Cs. Guidance on testing and
use of the germanium detector is given in IEC 60973, IEC 61151 and IEC 61452.
NOTE Pulse sorting equipment is readily available with 16 000 or more channels.
7.2.1.6 Shielding for the detector.
The detector shall be shielded on all sides including the bottom, to reduce the background to a low
constant level.
NOTE It is important that the background signal is not just low but, in particular, also constant. A variable
background signal can be caused by the presence of radon or radon progeny in the air as well as other reasons. For
the analysis of low levels of radioactivity, it can therefore be necessary to ventilate the assembly itself and the room
where it is set up. Ventilation of the assembly can be carried out using nitrogen gas.
7.2.1.7 Gamma-ray spectrometry analysis software, for analysing the acquired spectra.
Before using the software in routine operations, a check shall be performed on the numeric results. It is,
in particular, important to verify whether the method used to determine the continuum under a
photopeak and the method used to analyse the peaks using a small number of counting pulses provides
accurate results. It is recommended that, during routine use, a visual check and critical evaluation is
performed on the results provided by the software especially in relation to qualitative aspects. It is also
recommended that the same software is used for the evaluation of the spectra from the test samples and
for the evaluation of the calibration spectra.
NOTE Computer software that can analyse gamma-ray spectra is readily available and is often supplied in
combination with the detection equipment.
7.2.2 Detector energy and efficiency calibration
7.2.2.1 Energy calibration
Place one or more energy calibration sources in the measuring facility and configure the amplifier in such
a way that the first channel matches to an energy level between 0 keV and 50 keV. In addition, adjust, the
amplifier to ensure that the energy is less than 0,5 keV per channel. Determine where the photopeaks of
the calibration source are being counted and the energies with which these photopeak agree and the
relationship between the channel number and the energy using the channel numbers. Determine the
mathematical expression with which this relationship can be described with sufficient accuracy.
Individual observations shall deviate from the mathematical relationship by no more than 1 keV.
7.2.2.2 Efficiency calibration
Determine the radionuclide specific detection efficiency ε for the four energies E . listed in Table 1, for
i i
the conditions used in testing. Alternative photopeaks that can be used are listed in Annex D
(informative). The uncertainty in the detection efficiency shall be determined and should be less than
10 %.
Table 1 — Gamma-ray energies for determining the activity from radium-226, thorium-228,
radium-228 and potassium-40
Radionuclide Progeny Symbol Measured E Emission Interfering
i
a
radionuclide radionuclide [keV] probability nuclides
[%]
radium-226 – U lead-214 352 37,6 –

A
1; j
Th
thorium-232 thorium-228 thallium-208 583 30,4 –

A
2;j
radium-228 Th actinium-228 911 26,6 –

A
3; j
potassium-40 – K potassium-40 1461 10,7 actinium-

A
4 ;j
NOTE In the channel corresponding to the 1 461 keV energy line of potassium-40, a substantial relative
contribution from the 1 459,2 keV energy line of actinium-228 is expected when activities of potassium-40 are
low compared with the activity of radium-228.
U Th Th K
a
A , A , A and A are the activities of standardized calibration source j defined in Annex B
1; j 2; j 3; j 4; j
(normative).
The detection efficiency shall be determined according to one of the methods in EN ISO 20042:2021, 8.2,
which are:
a) direct comparison with a calibration source of the same radionuclide in the same matrix and
geometry. The detailed description of this method for NORM in construction products and building
materials in Annex B (normative) shall be used;
b) measurement of the full energy photopeak detection efficiency as a function of energy;
c) calculation of the full energy photopeak detection efficiency as a function of energy by Monte Carlo
simulation or other modelling technique. Such numerical models are sensitive to input parameters
such as the detector dimensions, and therefore shall be checked using at least one calibration source
containing radionuclides that emit gamma-rays covering the energy range of interest. If a
discrepancy is found between efficiency calculated using the model and the calibration source, the
discrepancy shall be investigated and corrections applied to the numerical model.
The same algorithm for analysis of the spectrum shall be used for both calibration and measurement of
the test specimen.
The detection efficiency is affected by the following factors:
— the detector;
— the geometry of the sample with respect to the detector (solid angle);
— the density of the sample and the sample container characteristics;
— the sample mass and chemical composition;
— the heterogeneity of the sample matrix with respect to activity, density and chemical composition.
When one of these factors is changed, the detection efficiency shall be re-evaluated for the new
conditions.
7.2.3 Measurements
7.2.3.1 Measurement of the test specimen
Measure each of the prepared test specimens individually. Therefore, place test specimen k on the
detector. Place the test specimen in an accurately reproducible position corresponding with the
established calibration.
Start the measurement. Never measure a test specimen when the counting rate or dead time is higher
than the one at which the detection efficiency is determined. Dead time corrections shall be properly
performed and not avoided, and corrections should also be properly validated. Record the spectrum, and
perform these activities for all the test specimens.
Appropriate counting times should be considered to reach sufficient levels of uncertainty, taking into
account the requirement to subtract the background spectrum.
7.2.3.2 Measurement of the blank
A background spectrum shall be recorded at
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