EN ISO 19581:2020

SLOVENSKI STANDARD
01-maj-2020
Merjenje radioaktivnosti - Radionuklidi, ki sevajo gama žarke - Metoda hitrega
presejanja z uporabo scintilacijskega zaznavala in gama spektrometrije (ISO
19581:2017)
Measurement of radioactivity - Gamma emitting radionuclides - Rapid screening method
using scintillation detector gamma-ray spectrometry (ISO 19581:2017)
Bestimmung der Radioaktivität - Gammastrahlung emittierende Radionuklide -
Schnellverfahren mit Szintillationsdetektor und Gammaspektrometrie (ISO 19581:2017)
Mesurage de la radioactivité - Radionucléides émetteurs gamma - Méthode d'essai de
dépistage par spectrométrie gamma utilisant des détecteurs par scintillation (ISO
19581:2017)
Ta slovenski standard je istoveten z: EN ISO 19581:2020
ICS:
17.240 Merjenje sevanja Radiation measurements
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 19581
EUROPEAN STANDARD
NORME EUROPÉENNE
February 2020
EUROPÄISCHE NORM
ICS 17.240
English Version
Measurement of radioactivity - Gamma emitting
radionuclides - Rapid screening method using scintillation
detector gamma-ray spectrometry (ISO 19581:2017)
Mesurage de la radioactivité - Radionucléides Bestimmung der Radioaktivität - Gammastrahlung
émetteurs gamma - Méthode d'essai de dépistage par emittierende Radionuklide - Schnellverfahren mit
spectrométrie gamma utilisant des détecteurs par Szintillationsdetektor und Gammaspektrometrie (ISO
scintillation (ISO 19581:2017) 19581:2017)
This European Standard was approved by CEN on 6 January 2020.

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
© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 19581:2020 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
The text of ISO 19581:2017 has been prepared by Technical Committee ISO/TC 85 "Nuclear energy,
nuclear technologies, and radiological protection” of the International Organization for Standardization
(ISO) and has been taken over as EN ISO 19581:2020 by Technical Committee CEN/TC 430 “Nuclear
energy, nuclear technologies, and radiological protection” the secretariat of which is held by AFNOR.
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 August 2020, and conflicting national standards shall
be withdrawn at the latest by August 2020.
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.
According to the CEN-CENELEC Internal Regulations, the national standards organizations 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.
Endorsement notice
The text of ISO 19581:2017 has been approved by CEN as EN ISO 19581:2020 without any modification.

INTERNATIONAL ISO
STANDARD 19581
First edition
2017-10
Measurement of radioactivity —
Gamma emitting radionuclides
— Rapid screening method using
scintillation detector gamma-ray
spectrometry
Mesurage de la radioactivité — Radionucléides émetteurs gamma —
Méthode d'essai de dépistage par spectrométrie gamma utilisant des
détecteurs par scintillation
Reference number
ISO 19581:2017(E)
©
ISO 2017
ISO 19581:2017(E)
© ISO 2017, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
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Tel. +41 22 749 01 11
Fax +41 22 749 09 47
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www.iso.org
ii © ISO 2017 – All rights reserved

ISO 19581:2017(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols and units . 3
5 Principle . 4
6 Apparatus . 6
7 Sample container . 7
8 Procedure. 7
8.1 Packaging of samples for measuring purposes . 7
8.2 Calibration . 8
8.2.1 General. 8
8.2.2 Reference source . 8
8.2.3 Check source . 8
8.2.4 Energy calibration . 8
8.2.5 Detection efficiency calibration . 9
8.3 Validation of the screening level .11
8.4 Screening procedure .11
8.4.1 Total spectrum counting / Single channel analyser counting .11
8.4.2 Multichannel analyser counting .12
8.4.3 Effect of sample density .13
9 Test report .13
Annex A (informative) Example of application of ISO 19581 for radio-caesium screening .15
Bibliography .18
ISO 19581:2017(E)
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 ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment,
as well as information about ISO's adherence to the World Trade Organization (WTO) principles in the
Technical Barriers to Trade (TBT) see the following URL: www.iso.org/iso/foreword.html.
This document was prepared by Technical committee ISO/TC 85, Nuclear Energy, nuclear technologies,
and radiological protection, Subcommittee SC 2, Radiological protection.
iv © ISO 2017 – All rights reserved

ISO 19581:2017(E)
Introduction
Everyone is exposed to natural radiation. The natural sources of radiation are cosmic rays and
naturally occurring radioactive substances which exist in the earth and within the human body. Human
activities involving the use of radiation and radioactive substances add to the radiation exposure
from this natural exposure. Some of those activities, such as the mining and use of ores containing
naturally-occurring radioactive materials (NORM) and the production of energy by burning coal that
contains such substances, simply enhance the exposure from natural radiation sources. Nuclear power
plants and other nuclear installations use radioactive materials and produce radioactive effluent and
waste during operation and on their decommissioning. The use of radioactive materials in industry,
agriculture and research is expanding around the globe.
All these human activities give rise to radiation exposures that are only a small fraction of the global
average level of natural exposure. The medical use of radiation is the largest and a growing man-made
source of radiation exposure in developed countries. It includes diagnostic radiology, radiotherapy,
nuclear medicine and interventional radiology.
Radiation exposure also occurs as a result of occupational activities. It is incurred by workers in
industry, medicine and research using radiation or radioactive substances, as well as by passengers
and crew during air travel and for astronauts. The average level of occupational exposures is generally
[11]
below the global average level of natural radiation exposure .
As uses of radiation increase, so do the potential health risk and the public's concerns. Thus, all these
exposures are regularly assessed in order to
a) improve the understanding of global levels and temporal trends of public and worker exposure
b) to evaluate the components of exposure so as to provide a measure of their relative importance, and
c) to identify emerging issues that may warrant more attention and study.
While doses to workers are mostly directly measured, doses to the public are usually assessed by
indirect methods using radioactivity measurements results performed on various sources: waste,
effluent and/or environmental samples.
To ensure that the data obtained from radioactivity monitoring programs support their intended use, it
is essential that the stakeholders (for example, nuclear site operators, regulatory and local authorities)
agree on appropriate methods and procedures for obtaining representative samples and then
handling, storing, preparing and measuring the test samples. A assessment of the overall measurement
uncertainty needs also to be carried out systematically. As reliable, comparable and ‘fit for purpose’
data are an essential requirement for any public health decision based on radioactivity measurements,
international standards of tested and validated radionuclide test methods are an important tool for
the production of such measurement results. The application of standards serves also to guarantee
comparability over time of the test results and between different testing laboratories. Laboratories
apply them to demonstrate their technical qualifications and to successfully complete proficiency
tests during interlaboratory comparison, two prerequisites for obtaining national accreditation.
Today, over a hundred international standards, prepared by Technical Committees of the International
Standardization Organization, including those produced by ISO/TC85, and the International
Electrotechnical Commission (IEC), are available for application by testing laboratories to measure the
main radionuclides.
Generic standards help testing laboratories to manage the measurement process by setting out the
general requirements and methods to calibrate and validate techniques. These standards underpin
specific standards which describe the test methods to be performed by staff, for example, for different
types of sample. The specific standards cover test methods for:
40 3 14
— Naturally-occurring radionuclides (including K, H, C and those originating from the thorium
226 228 234 238 210
and uranium decay series, in particular Ra, Ra, U, U, Pb) which can be found in
materials from natural sources or can be released from technological processes involving naturally
ISO 19581:2017(E)
occurring radioactive materials (e.g. the mining and processing of mineral sands or phosphate
fertilizer production and use);
— Human-made radionuclides, such as transuranium elements (americium, plutonium, neptunium,
3 14 90
and curium), H, C, Sr and gamma emitting radionuclides found in waste, liquid and gaseous
effluent, in environmental matrices (water, air, soil, biota) and food and feed as a result of authorized
releases into the environment and of fallout resulting from the explosion in the atmosphere of
nuclear devices and accidents, such as those that occurred in Chernobyl and Fukushima.
Environmental materials, including foodstuffs, thus may contain radionuclides at activity
concentrations which could present a risk to human health. In order to assess the potential human
exposure to radioactivity and to provide guidance on reducing health risks by taking measures to
decrease radionuclide activity concentrations, the environment and foodstuffs are routinely monitored
for radioactivity content as recommended by the World Health Organization (WHO). Gamma-emitting
radionuclides are usually quantified in environmental and food samples by gamma-ray spectrometry
using High Purity Germanium (HPGe) gamma-ray spectrometry. Following a nuclear accident, a
screening approach based on rapid test methods is recommended to help the decision makers to decide
whether activity concentrations in environmental samples, feed and food samples are above or below
[12]
operational intervention levels (OILs) that are specifically set up to manage nuclear and radiological
emergency. During nuclear emergency response, these default radionuclide specific OILs for food, milk
and water concentrations from laboratory analysis would be used to measure the effectiveness of
[12][13]
protective actions and contribute to determining any further actions required .
In 1989, following the Chernobyl accident, the first version of the Codex Guideline Levels (GLs) for
Radionuclides in Foods Contaminated Following a Nuclear or Radiological Emergency (in the following
referred to as “Codex GLs”) was adopted. The Codex GLs were reviewed in 2006 and are included
[14][15]
in the General Standard for Contaminants and Toxins in Food and Feeds . During a nuclear
106 106 131
emergency situation, the Codex GLs for gamma-emitting radionuclides such as Ru/ Rh and I is
−1 60 103 137 134 144 −1
100 Bq·kg ; the GL for Co, Ru, Cs and Cs, Ce is higher at 1000 Bq·kg but a lower limit of
−1
100 Bq·kg still applies for foods for infants. Default radionuclide specific OILs for food, milk and water
concentrations from laboratory analysis set up by FAO, IAEA, ILO, OECD/NEA, PAHO, OCHA, WHO were
[16]
recently revised .
NOTE The Codex GLs are the activity concentration in foods that would result in an effective dose of
1 mSv/year for members of the Public (infant and adult) in accordance with the most recent recommendations
of the International Commission on Radiological Protection (ICRP) considering that 550 kg of food is consumed
per year by an adult and 200 kg of food and milk is consumed per year by an infant, with 10 % of the diet is of
imported food, all of which is contaminated giving an import to production factor of 0,1. For convenience the
GL values were rounded, and radionuclides with ingestion dose coefficients of similar magnitudes grouped
and given similar GLs values. However, separate GLs were derived for infants and adults due to differences in
radionuclide absorption, metabolism and sensitivity to radiation.
Emergency preparedness should include planning for the implementation of optimized test methods
that can provide rapid estimates of activity concentration to be checked against OILs. Thus, an
international standard on a screening method using Gamma-Ray Spectrometry is justified for use
by testing laboratories carrying out measurements of gamma-emitting radionuclides during an
emergency situation. Such laboratories are intended to obtain a specific accreditation for radionuclide
measurement in environmental and/or food samples.
This document describes, after proper sampling, sample handling and preparation, a screening method
to quantify rapidly the activity concentration of iodine and caesium in environmental, feedstuffs and
foodstuffs samples using scintillation spectrometer during an emergency situation.
This document is one of a set of generic international standards on measurement of radioactivity.
vi © ISO 2017 – All rights reserved

INTERNATIONAL STANDARD ISO 19581:2017(E)
Measurement of radioactivity — Gamma emitting
radionuclides — Rapid screening method using
scintillation detector gamma-ray spectrometry
WARNING — Persons using this document should be familiar with normal testing laboratory
practice. This standard 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 and to ensure compliance with any national regulatory conditions.
IMPORTANT — It is absolutely essential that tests conducted according to this document be
carried out by suitably trained staff.
1 Scope
This document specifies a screening test method to quantify rapidly the activity concentration of
131 132 134 137
gamma-emitting radionuclides, such as I, Te, Cs and Cs, in solid or liquid test samples using
gamma-ray spectrometry with lower resolution scintillation detectors as compared with the HPGe
detectors (see IEC 61563).
This test method can be used for the measurement of any potentially contaminated environmental
matrices (including soil), food and feed samples as well as industrial materials or products that
have been properly conditioned. Sample preparation techniques used in the screening method
are not specified in this document, since special sample preparation techniques other than simple
machining (cutting, grinding, etc.) should not be required. Although the sampling procedure is of
utmost importance in the case of the measurement of radioactivity in samples, it is out of scope of this
document; other international standards for sampling procedures that can be used in combination with
this document are available (see References [1],[2],[3],[4],[5],[6]).
131 134
The test method applies to the measurement of gamma-emitting radionuclides such as I, Cs
and Cs. Using sample sizes of 0,5 l to 1,0 l in a Marinelli beaker and a counting time of 5 min to
−1
20 min, decision threshold of 10 Bq·kg can be achievable using a commercially available scintillation
spectrometer [e.g. thallium activated sodium iodine (NaI(Tl)) spectrometer 2” ϕ × 2” detector size, 7 %
resolution (FWHM) at 662 keV, 30 mm lead shield thickness].
This test method also can be performed in a “makeshift” laboratory or even outside a testing laboratory
on samples directly measured in the field where they were collected.
During a nuclear or radiological emergency, this test method enables a rapid measurement of the sample
activity concentration of potentially contaminated samples to check against operational intervention
levels (OILs) set up by decision makers that would trigger a predetermined emergency response to
[12]
reduce existing radiation risks .
Due to the uncertainty associated with the results obtained with this test method, test samples requiring
more accurate test results can be measured using high-purity germanium (HPGe) detectors gamma-ray
[7][8]
spectrometry in a testing laboratory, following appropriate preparation of the test samples .
This document does not contain criteria to establish the activity concentration of OILs.
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 19581:2017(E)
ISO 11929, Determination of the characteristic limits (decision threshold, detection limit and limits of the
confidence interval) for measurements of ionizing radiation — Fundamentals and application
ISO 80000-10, Quantities and units — Part 10: Atomic and nuclear physics
ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
IEC 61453, Nuclear instrumentation — Scintillation gamma ray detector systems for the assay of
radionuclides – Calibration and routine tests
3 Terms and definitions
For the purposes of this document, the terms, definitions, and the symbols and abbreviations given in
ISO 80000-10 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at http://www.iso.org/obp
— IEC Electropedia: available at http://www.electropedia.org/
3.1
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
3.2
emergency
non-routine situation that necessitates prompt action, primarily to mitigate a hazard or adverse
consequences for human life and health, property and the environment
[SOURCE: IAEA safety glossary 2016 Rev.]
Note 1 to entry: This includes nuclear and radiological emergencies and conventional emergencies such as
fires, release of hazardous chemicals, storms or earthquakes. It includes situations for which prompt action is
[12]
warranted to mitigate the effects of a perceived hazard .
3.3
operational intervention level
OIL
set level of a measurable quantity that corresponds to a generic criterion
[SOURCE: IAEA safety glossary 2016 Rev. Mod]
Note 1 to entry: OILs are calculated levels, measured by instruments or determined by laboratory analysis,
that corresponds to an intervention level or action level. These are typically expressed in terms of dose rates
or of activity of radioactive material released, time integrated air activity concentrations, ground or surface
concentrations, or activity concentrations of radionuclides in environmental, food or water samples. OILs are
used immediately and directly (without further assessment) to determine the appropriate protective actions on
[12]
the basis of an environmental measurement .
2 © ISO 2017 – All rights reserved

ISO 19581:2017(E)
3.4
reference level
level of dose, risk or activity
concentration above which it is not appropriate to plan exposures to occur and below which optimization
of protection and safety would continue to be implemented
[SOURCE: IAEA safety glossary 2016 Rev.]
Note 1 to entry: The chosen value for a reference level depends upon the prevailing circumstances of the exposure
[13]
under consideration . Above the reference level, it is judged that the risks from exposure are not justified and
therefore is not allowed to occur. Below the reference level, optimization of personnel protection needs to be
implemented to keep exposures as low as reasonably achievable (ALARA).
3.5
screening level
SL
values that are set up by the laboratory taking into account the characteristics of the measuring
equipment and the test method to guarantee that the test result and its uncertainty obtained are fit for
purpose for comparison with the operational intervention levels (OILs)
Note 1 to entry: The screening level is less than the OIL. Therefore food is safe for consumption if the screening
[16]
level is not exceeded. Actions to take, if the food is not safe for consumption, are given in Reference .
4 Symbols and units
A Activity of each radionuclide in reference source, at the measurement time, in becquerels
c Activity concentration of each radionuclide expressed in becquerels per kilogram
A
c Activity concentration that corresponds to the screening level of each radionuclide
A,SL
expressed in becquerels per kilogram
c Activity concentration that corresponds to the OIL of each radionuclide expressed in
A,RL
becquerels per kilogram
Decision threshold, without and with corrections, in becquerels per kilogram
*
c
A
# Detection limit, without and with corrections, in becquerels per kilogram
c
A
 Upper limits of the confidence interval, in becquerels per kilogram
c
A
R the ratio of the indicated value of a spectrometer to the conventional true value of spe-
i
cific radionuclide, i
ε Counting efficiency of the detector at energy, E
E
ε Radionuclide-specific counting efficiency of the detector at energy, E, of specific radi-
i,E
onuclide, i
n , Number of net counts in the gamma-ray energy region of interest, at energy E, in the
N,E
sample spectrum, in the calibration spectrum and in the spectrum obtained from the
n
Ns,E,
measurement of reference sample having activity that corresponds to the screening
n
level, respectively
N,SL,E
n , n , Number of gross counts in the gamma-ray energy region of interest, at energy E, in the
g,E gb,E
sample spectrum, in the background spectrum, in the calibration spectrum and in the
n n
gs,E g,SL,E
spectrum obtained from the measurement of reference sample having activity that
corresponds to the screening level, respectively
ISO 19581:2017(E)
P Probability of the emission of a gamma ray with energy, E, of each radionuclide, per decay
E
R Response of the detector/radiometer to the reference activity of radionuclide, i
i
t Sample counting live time, in seconds
g
T Background counting live time, in seconds
b
t Reference source counting live time, in seconds
s
t Counting live time, in seconds, of a reference sample with an activity corresponding to
SL
a screening level
t The two sided t-distribution with k-1 degree of freedom and α two sides probability
k-1,α
u(c ) Standard uncertainty associated with the measurement result c , without and with
A A
corrections, in becquerels per kilogram
U Expanded uncertainty calculated by U = k ·u (c ) with k = 1, 2., in becquerels per kilogram
A
m Mass of the sample for test, in kilograms
α, β Probability of a false positive and false negative decision, respectively
1−γ Probability for the coverage interval of the measurand
5 Principle
During a nuclear or radiological emergency, it is essential to measure rapidly the activity concentration
in samples from the environment and potentially contaminated foodstuffs and feed to protect
workers and the public, in accordance with international standards, by keeping doses below the dose
[13]
reference levels . It is recognized among organizations responsible for emergency management
that good preparedness can substantially improve the emergency situation response. Thus default
OILs for food are set up by national authorities, and measurement procedures using commonly
available contamination screening equipment are implemented to meet the OILs criteria. This should
be carried out as part of the emergency preparedness process. The process of assessing radionuclide
concentrations in food, milk and water is shown in Figure 1. During the process of assessing radionuclide
concentrations in food, milk and water the potentially contaminated food should be screened over a
wide area and analysed to determine promptly the activity concentration of gross and/or individual
radionuclides. If the OIL are not exceeded, the food, milk and water are safe for consumption during
the emergency phase. If an OIL is exceeded, the radionuclide specific concentrations in the food, milk or
[17]
water should be determined. Finally, as soon as possible the guidance in Reference should be used
to determine whether the food, milk or water is suitable for international trade, and national criteria or
[18]
WHO guidance should be used to determine whether the food, milk or water is suitable for long term
[16]
consumption after the emergency phase .
4 © ISO 2017 – All rights reserved

ISO 19581:2017(E)
Figure 1 — Example of process of assessing radionuclide concentrations in food
[16]
(see explanations in the text and modified from Reference )
Laboratories shall make the necessary arrangements to be able to perform appropriate and reliable
analyses of environmental and food/feed samples for the purposes of an emergency response. Thus,
a screening approach is required, using a fast test method that rapidly provides test results to the
decision maker in order to determine whether food and/or feed is suitable for human and/or animal
consumption during the post-accident monitoring period and for international trade.
The main radioactive materials released into the atmosphere during a power plant nuclear accident are
131 132 133 134 136 137
volatile elements including iodine isotopes ( I, I, I), caesium isotopes ( Cs, Cs, Cs) and
tellurium ( Te). Samples taken from the environment, the foodstuffs and feed may initially contain
131 [19]
high activity concentrations of I relative to the caesium isotopes . Although often activity released
is also dominated by noble gases, these cannot end up in food.
Therefore the accident monitoring that shall be implemented immediately following a nuclear accident
requires a test method designed for the screening of I activity concentration of environmental
and food samples. When using a test method with a scintillation detector system incorporating a
spectrometer (hereinafter referred to as scintillation spectrometer) or a portable gamma-ray detector
(e.g. survey meter) with no radionuclide discrimination function, I is not determined separately from
other iodine isotopes and caesium isotopes. When using a test method with a scintillation spectrometer
131 134 137
I, Cs and Cs can be discriminated and potentially quantified with a test method using a
scintillation spectrometer. However, using a multichannel analyzer (MCA) with a peak deconvolution
program does not avoid the contributions in the energy region of interest of other radionuclides,
including short-lived iodine isotopes, caesiums and naturally occurring radionuclides. The I activity
concentration is therefore overestimated but this is considered as acceptable during the immediate
phase following a nuclear accident to rapidly assess the contamination.
A few months after the accident, the short-lived radionuclides, including iodine isotopes, have decayed.
134 137
Longer-lived radionuclides including Cs and Cs become predominant in environmental and food
samples. During this later period, when using a test method with a portable gamma-ray detector (e.g.
134 137
survey meter) with no radionuclide discrimination function, Cs and Cs activity concentration
cannot be quantified separately and the test result is considered as the gross activity of both Cs and
Cs. With a scintillation spectrometer individual nuclide activity concentrations can be determined.
ISO 19581:2017(E)
However contributions from naturally occurring radionuclides might be unavoidable even during this
later period.
134 137
NOTE In the later stage, the radionuclide composition is usually known, including the ratio of Cs to Cs;
it allows to estimate the activity concentration of the individual caesium isotopes using the gross activity results.
Direct measurement without iodine retention treatment, evaporation or ashing can be used to measure
the activity concentration rapidly during the accident and post-accident monitoring period. The test
sample is measured directly without any preparation, preferably in a Marinelli beaker type container.
As the tests are performed to check the activity concentration of the sample against OILs set up by
national authority, screening levels should be set in a range from half of these OILs to close to the OILs
in order to avoid false-positives.

Upper limit of confidence interval of the best estimate of the true value for the screening level C
A,SL
1)
shall be below that for the operational intervention level C with a 95 % confidence level (α = 0,05,
A,RL
k = 2) as shown in the following equation:

CC=+tu⋅<()CC (1)
AA,,SL SL kA−1,,α SL A,RL
where
t is the two sided t-distribution;
is the uncertainty of the best estimate of the true value for the screening level.
uC()
A,SL
The probability distribution function associated with the test results can be obtained by repeating the
tests on the same samples. uC() should be determined by repeated measurement with the
A,SL
minimum counting time of a reference source or reference material with an activity close to the

screening level of the radionuclide tested and containing no other radionuclide. C should specify
A,SL
the number of repeated measurements which would enable the use of a t-distribution (see 8.3). This
document recommends to repeat the measurements of the same sample a minimum of 4 times.
In order to ensure the reliability of the screening test, the decision threshold (see ISO 11929) is defined
taking into consideration that the counting time shall be shortened to obtain the test results rapidly
for a large number of samples. This document recommends that one-fourth of the OIL value is an
appropriate value for the decision threshold.
6 Apparatus
Several types of scintillation spectrometers can be used for sample screening. Commercially available
scintillation crystals that would be useful for the screening test are shown in Table 1.
Table 1 — Examples of commercially available scintillation crystals. Typical detector size and
its resolution are also shown
Crystal Detector size Resolution at 662 keV
NaI(Tl) 2” ϕ × 2” 8 %
CsI(Tl) 2” ϕ × 2” 10 %
LaBr 2” ϕ × 2” <3 %
1)  α = 0,05 (k = 2) is often chosen by default in the international standards for radiological protection but another
α value may be required by the national regulation authority. For example, screening level being set above half of
the level of the reference value with α=0,02 were required by Japanese government authority for the radio-caesium
screening test in food following the Fukushima accident.
6 © ISO 2017 – All rights reserved

ISO 19581:2017(E)
Table 1 (continued)
Crystal Detector size Resolution at 662 keV
SrI(Eu) 1,5” ϕ × 1,5” <4 %
CeBr 2” ϕ × 2” <4 %
GAGG(Ce) 2” ϕ × 2” <7 %
BGO 2” ϕ × 2” 10 %
CLYC 2” ϕ × 2” <5 %
A spectrometry apparatus consists of two parts: the scintillation detector with plug-on or external
electronics and multi-channel analyser and the device which handles stores and analyses the measured
spectra. Digital signal processing electronics are commonly used. Portable scintillation spectrometers
for in situ measurements are also available. For screening, a simple total spectrum counting system
that counts all pulses above a low-energy threshold or single-channel analyser (SCA) counting system
that counts all pulses between upper and lower energy boundaries can be also used.
A portable gamma-ray detector (e.g. dose-rate meter that cannot provide spectrum information) which
has sufficient sensitivity can also be used for screening as a simple total spectrum counting system that
counts all pulses above a low-energy threshold instead of a spectrometer. For screening measurements,
a portable gamma dose-rate meter may be simpler to use than spectrometers if a sufficiently low
decision threshold is achievable within an appropriate counting time. However when low OILs are
implemented, a radiation shield and/or large scintillator may be required to reduce the background
level and to have sufficient detection efficiency, respectively.
7 Sample container
Sample containers that are suited to gamma spectrometry have the recommended characteristics:
— be made of materials with low absorption of gamma radiation;
— be made of transparent or semi-transparent material to see the level of content;
— have volumes and geometries adapted to the shape of the detector to ensure maximum detection
efficiency;
— be watertight and not react with the test sample constituents;
— have a wide-necked opening and a close-fitting lid to facilitate filling;
— highly resistant to breakage.
In order to verify easily that the content of the container conforms to the standard counting geometry, a
transparent container with a clearly discernible mark to indicate the fill level should be used.
To avoid contamination of the container or in order to reuse it, the sample can be placed in a plastic bag
in the container.
8 Procedure
8.1 Packaging of samples for measuring purposes
Test samples submitted to screening by gamma spectrometry measurement are usually rough test
samples without any preparation.
The procedure shall be carried out as follows:
a) Choose the container type that is best suited to the largest quantity of the test sample and
determine the mass of the empty container (tare).
ISO 19581:2017(E)
b) Fill the container to the level of the filling mark and measure the gross mass of the container.
Visually check the surface level of the test sample in the container and ensure that it is horizontal
before measuring.
c) Measure and note the test sample mass or volume. This information is needed to calculate the
−1 −1
activity concentration (Bq·kg or Bq·l ).
d) Hermetically seal the container if volatile radionuclides are being measured.
e) Clean the outside of the container to remove potential contamination due to the filling process.
8.2 Calibration
8.2.1 General
The calibration procedure is presented for two types of apparatus:
a) gross-count type apparatus.
An apparatus that counts all the signals with pulse heights higher than a threshold.
b) single-channel or multi-channel pulse height analysing type apparatus.
An apparatus that analyses pulse heights of signals using a single-channel or multi-channel pulse height
analysing function.
All apparatus shall be operated in accordance with th
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