SIST EN ISO 13165-3:2020

Water quality - Radium-226 - Part 3: Test method using coprecipitation and gamma-spectrometry (ISO 13165-3:2016)

ISO 13165-3:2016 specifies the determination of radium-226 (226Ra) activity concentration in all types of water by coprecipitation followed by gamma-spectrometry (see ISO 18589‑3).
The method described is suitable for determination of soluble 226Ra activity concentrations greater than 0,02 Bq l−1 using a sample volume of 1 l to 100 l of any water type.
For water samples smaller than a volume of 1 l, direct gamma-spectrometry can be performed following ISO 10703 with a higher detection limit.
NOTE This test method also allows other isotopes of radium, 223Ra, 224Ra, and 228Ra, to be determined.

Wasserbeschaffenheit - Radium 226 - Teil 3: Verfahren mittels Kopräzipitation und Gammaspektrometrie (ISO 13165-3:2016)

Dieser Teil von ISO 13165 legt die Bestimmung der Aktivitätskonzentration von Radium 226 (226Ra) in allen Arten von Wasser durch Mitfällung und anschließende Gammaspektrometrie fest (siehe ISO 18589 3).
Das beschriebene Verfahren eignet sich zur Bestimmung der Aktivitätskonzentrationen von löslichem 226Ra von mehr als 0,02 Bq l−1 bei einem Probenvolumen von 1 l bis 100 l eines beliebigen Wassertyps.
Für Wasserproben mit einem Volumen von weniger als 1 l kann eine direkte Gammaspektrometrie nach ISO 10703 mit einer höheren Nachweisgrenze durchgeführt werden.
ANMERKUNG   Mit diesem Prüfverfahren können auch andere Radiumisotope, 223Ra, 224Ra und 228Ra, bestimmt werden.

Qualité de l'eau - Radium 226 - Partie 3: Méthode d'essai par coprécipitation et spectrométrie gamma (ISO 13165-3:2016)

L'ISO 13165-3:2016 spécifie la détermination de l'activité volumique du radium 226 (226Ra), dans tous les types d'eaux par coprécipitation suivie d'une spectrométrie gamma (voir l'ISO 18589‑3).
La méthode décrite est applicable pour la détermination de l'activité volumique du 226Ra soluble ayant une activité volumique en 226Ra supérieure à 0,02 Bq l−1 en utilisant un volume d'échantillon compris entre 1 l et 100 l de tout type d'eau.
Pour des échantillons d'eau inférieurs à un volume de 1 l, la spectrométrie gamma directe peut être effectuée en se conformant à l'ISO 10703 avec une limite de détection supérieure.
NOTE Cette méthode d'essai permet également le mesurage d'autres isotopes du radium (223Ra, 224Ra et 228Ra).

Kakovost vode - Radij Ra-226 - 3. del: Preskusna metoda s soobarjanjem in gama spektrometrijo (ISO 13165-3:2016)

General Information

• Status: Published
• Public Enquiry End Date: 01-Aug-2019
• Publication Date: 07-Apr-2020
• ICS: 13.060.60 - Examination of physical properties of water
• ICS: 17.240 - Radiation measurements
• Technical Committee: KAV - Water quality
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 31-Mar-2020
• Due Date: 05-Jun-2020
• Completion Date: 08-Apr-2020
• Ref Project: EN ISO 13165-3:2020 - Water quality - Radium-226 - Part 3: Test method using coprecipitation and gamma-spectrometry (ISO 13165-3:2016)

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN ISO 13165-3:2020
01-maj-2020
Kakovost vode - Radij Ra-226 - 3. del: Preskusna metoda s soobarjanjem in gama
spektrometrijo (ISO 13165-3:2016)

Water quality - Radium-226 - Part 3: Test method using coprecipitation and gamma-

spectrometry (ISO 13165-3:2016)

Wasserbeschaffenheit - Radium 226 - Teil 3: Verfahren mittels Kopräzipitation und

Gammaspektrometrie (ISO 13165-3:2016)
Qualité de l'eau - Radium 226 - Partie 3: Méthode d'essai par coprécipitation et
spectrométrie gamma (ISO 13165-3:2016)
Ta slovenski standard je istoveten z: EN ISO 13165-3:2020
ICS:
13.060.60 Preiskava fizikalnih lastnosti Examination of physical
vode properties of water
17.240 Merjenje sevanja Radiation measurements
SIST EN ISO 13165-3:2020 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 13165-3:2020
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SIST EN ISO 13165-3:2020
EN ISO 13165-3
EUROPEAN STANDARD
NORME EUROPÉENNE
February 2020
EUROPÄISCHE NORM
ICS 13.060.60; 17.240
English Version
Water quality - Radium-226 - Part 3: Test method using
coprecipitation and gamma-spectrometry (ISO 13165-
3:2016)

Qualité de l'eau - Radium 226 - Partie 3: Méthode Wasserbeschaffenheit - Radium 226 - Teil 3: Verfahren

d'essai par coprécipitation et spectrométrie gamma mittels Kopräzipitation und Gammaspektrometrie (ISO

(ISO 13165-3:2016) 13165-3:2016)
This European Standard was approved by CEN on 6 October 2019.

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 13165-3:2020 E

worldwide for CEN national Members.
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SIST EN ISO 13165-3:2020
EN ISO 13165-3:2020 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST EN ISO 13165-3:2020
EN ISO 13165-3:2020 (E)
European foreword

The text of ISO 13165-3:2016 has been prepared by Technical Committee ISO/TC 147 "Water quality”

of the International Organization for Standardization (ISO) and has been taken over as EN ISO 13165-

3:2020 by Technical Committee CEN/TC 230 “Water analysis” the secretariat of which is held by DIN.

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 13165-3:2016 has been approved by CEN as EN ISO 13165-3:2020 without any

modification.
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SIST EN ISO 13165-3:2020
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SIST EN ISO 13165-3:2020
INTERNATIONAL ISO
STANDARD 13165-3
First edition
2016-03-01
Water quality — Radium-226 —
Part 3:
Test method using coprecipitation and
gamma-spectrometry
Qualité de l’eau — Radium 226 —
Partie 3: Méthode d’essai par coprécipitation et spectrométrie gamma
Reference number
ISO 13165-3:2016(E)
ISO 2016
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SIST EN ISO 13165-3:2020
ISO 13165-3:2016(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2016, 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

the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. [phone]
Fax [phone]
[e-mail]
www.iso.org
ii © ISO 2016 – All rights reserved
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SIST EN ISO 13165-3:2020
ISO 13165-3:2016(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Symbols .......................................................................................................................................................................................................................... 2

5 Principle of the measurement ................................................................................................................................................................ 3

6 Reagents and equipment ............................................................................................................................................................................. 3

6.1 Reagents........................................................................................................................................................................................................ 3

6.2 Equipment ................................................................................................................................................................................................... 4

7 Sampling ........................................................................................................................................................................................................................ 4

7.1 Sample collection .................................................................................................................................................................................. 4

7.2 Sample transport and storage .................................................................................................................................................... 4

8 Procedures .................................................................................................................................................................................................................. 4

8.1 Blank sample preparation ............................................................................................................................................................. 4

8.2 Sample preparation ............................................................................................................................................................................ 5

8.3 Counting procedure ............................................................................................................................................................................ 5

9 Quality assurance and quality control programme ......................................................................................................... 5

9.1 General ........................................................................................................................................................................................................... 5

9.2 Influence quantities ............................................................................................................................................................................ 6

9.3 Instrument verification.................................................................................................................................................................... 6

9.4 Method verification ............................................................................................................................................................................. 6

9.5 Demonstration of analyst capability .................................................................................................................................... 6

10 Expression of results ........................................................................................................................................................................................ 6

10.1 General ........................................................................................................................................................................................................... 6

226

10.2 Water-soluble Ra activity concentration .................................................................................................................. 7

10.3 Standard uncertainty of activity concentration .......................................................................................................... 7

10.4 Decision threshold ............................................................................................................................................................................... 7

10.5 Detection limit ......................................................................................................................................................................................... 7

10.6 Limits of the confidence interval ............................................................................................................................................. 8

10.7 Corrections for contributions from other radionuclides and background ......................................... 8

10.7.1 General...................................................................................................................................................................................... 8

10.7.2 Contribution from other radionuclides ........................................................................................................ 9

10.7.3 Contribution from background ........................................................................................................................10

11 Expression of results .....................................................................................................................................................................................10

Annex A (informative) Uranium and its decay chain .......................................................................................................................12

Bibliography .............................................................................................................................................................................................................................14

© ISO 2016 – All rights reserved iii
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SIST EN ISO 13165-3:2020
ISO 13165-3:2016(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 WTO principles in the Technical

Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information

The committee responsible for this document is ISO/TC 147, Water quality, Subcommittee SC 3,

Radioactivity measurements.

ISO 13165 consists of the following parts, under the general title Water quality — Radium-226:

— Part 1: Test method using liquid scintillation counting
— Part 2: Test method using emanometry
— Part 3: Test method using coprecipitation and gamma-spectrometry
iv © ISO 2016 – All rights reserved
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SIST EN ISO 13165-3:2020
ISO 13165-3:2016(E)
Introduction

Radioactivity from several naturally occurring and human-made sources is present throughout the

environment. Thus, water bodies (surface waters, ground waters, sea waters) can contain radionuclides

of natural and human-made origins:

Natural radionuclides, including potassium-40, and those of the thorium and uranium decay series, in

particular radium-226, radium-228, uranium-234, uranium-238, and lead-210, can be found in water for

natural reasons (e.g. desorption from the soil and wash-off by rain water) or releases from technological

processes involving naturally 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,

curium), tritium, carbon-14, strontium-90, and gamma emitters radionuclides can also be found

in natural waters as they can be authorized to be routinely released into the environment in small

quantities in the effluent discharge from nuclear fuel cycle facilities and following their use in unsealed

form in medicine or industry. They are also found in the water due to the past fallout of the explosion in

the atmosphere of nuclear devices and those following the Chernobyl and Fukushima accident.

Human-made radionuclides, such as transuranium elements (americium, plutonium, neptunium,

curium), tritium, carbon-14, strontium-90, and some gamma emitting radionuclides, can also be found

in natural waters as a result of authorized routine releases into the environment in small quantities in

the effluent discharged from nuclear fuel cycle facilities. They are also released into the environment

following their use in unsealed form for medical and industrial applications. They are also found in

the water as a result of past fallout contamination resulting from the explosion in the atmosphere of

nuclear devices and accidents such as those that occurred in Chernobyl and Fukushima.

Drinking water can thus contain radionuclides at activity concentration which could present a risk to

human health. In order to assess the quality of drinking water (including mineral waters and spring

waters) with respect to its radionuclide content and to provide guidance on reducing health risks by

taking measures to decrease radionuclide activity concentrations, water resources (groundwater, river,

lake, sea, etc.) and drinking water are monitored for their radioactivity content as recommended by the

World Health Organization (WHO) and can be required by some national authorities.

The need of a standard on a test method of radium-226 activity concentrations in water samples is

justified for test laboratories carrying out these measurements, required sometimes by national

authorities, as they may have to obtain a specific accreditation for radionuclide measurement in

drinking water samples.

Radium-226 activity concentration can vary widely according to local geological and climatic

−1 −1

characteristics and ranges from 0,001 Bq·l in surface waters up to 50 Bq·l in natural groundwaters;

the guidance level for radium 226 in drinking water as recommended by WHO is 1 Bq·l (see

Reference [13]).

NOTE The guidance level is the activity concentration (rounded to the nearest order of magnitude) with an

−1 −1

intake of 2 l·d of drinking water for 1 year that results in an effective dose of 0,1 mSv·y for members of the

public, an effective dose that represents a very low level of risk that is not expected to give rise to any detectable

adverse health effect.

This International Standard is one of a series on determination of the activity concentration of

radionuclides in water samples.
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SIST EN ISO 13165-3:2020
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SIST EN ISO 13165-3:2020
INTERNATIONAL STANDARD ISO 13165-3:2016(E)
Water quality — Radium-226 —
Part 3:
Test method using coprecipitation and gamma-
spectrometry

WARNING — Persons using this part of ISO 13165 should be familiar with normal laboratory

practice. This part of ISO 13165 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 in accordance with this part of

ISO 13165 be carried out by suitably qualified staff.
1 Scope
226

This part of ISO 13165 specifies the determination of radium-226 ( Ra) activity concentration in all

types of water by coprecipitation followed by gamma-spectrometry (see ISO 18589-3).

226

The method described is suitable for determination of soluble Ra activity concentrations greater

than 0,02 Bq l using a sample volume of 1 l to 100 l of any water type.

For water samples smaller than a volume of 1 l, direct gamma-spectrometry can be performed following

ISO 10703 with a higher detection limit.
223 224 228

NOTE This test method also allows other isotopes of radium, Ra, Ra, and Ra, to be determined.

2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

ISO 5667-3, Water quality — Sampling — Part 3: Preservation and handling of water samples

ISO 10703, Water quality — Determination of the activity concentration of radionuclides — Method by

high resolution gamma-ray spectrometry

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/IEC 17025, General requirements for the competence of testing and calibration laboratories

ISO 80000-10, Quantities and units — Part 10: Atomic and nuclear physics
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 80000-10 and the

following apply.
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SIST EN ISO 13165-3:2020
ISO 13165-3:2016(E)
3.1
activity

number of spontaneous nuclear disintegrations occurring in a given quantity of material during a

suitably small interval of time divided by that interval of time
[SOURCE: ISO 921:1997, 23]
3.2
reference standard

standard, generally having the highest metrological quality available at a given location or in a given

organisation, from which measurements made there are derived
3.3
working standard

standard which, usually calibrated against a reference standard (3.2), is used routinely to calibrate or

check material measures, measuring instruments or reference materials. It can be used as a solution of

known activity (3.1) concentration obtained by precise dilution or dissolution of a reference standard

4 Symbols

For the purposes of this part of ISO 13165, the symbols defined in ISO 11929 and ISO 80000-10, and the

following apply.
Table 1 — List of symbols
V Volume of the test sample in litres

A Activity of each radionuclide in calibration source, at the calibration time, in becquerels

226
cc,

Activity concentration of Ra, without and with corrections, expressed in becquerels per litre

AAc
M Mass of barium sulfate, in grams
sulfate
M Mass of barium nitrate, in grams
nitrate
M Mass of barium carbonate, in grams
carbonate
t Sample spectrum counting time, in seconds
t Background spectrum counting time, in seconds
t Calibration spectrum counting time, in seconds

Number of counts in the net area of the peak considered, at energy E, in the sample, background

nn,,n
NN0 Ns
and calibration spectra, respectively

Number of counts in the gross area of the peak considered, at energy E, in the sample, back-

nn,,n
gg0 gs
ground and calibration spectra, respectively

Number of counts in the background of the peak considered, at energy E, in the sample, back-

nn,,n
bb0 bs
ground and calibration spectra, respectively
Efficiency of the detector at energy E, at actual measurement geometry
R Chemical yield

Probability of the emission of a gamma ray with energy, E, of each radionuclide, per decay, i.e.

the branching ratio or the number of γ-quanta per decay
u(c ) Standard uncertainty of activity concentration, in becquerels per litre
u(x) Standard uncertainty of measurand x
u (x) Relative uncertainty: u(x)∕x
rel

U Expanded uncertainty calculated by U = k u(c ) with k usually equals 2, in becquerels per litre

c Decision threshold, in becquerels per litre
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SIST EN ISO 13165-3:2020
ISO 13165-3:2016(E)
Table 1 (continued)
c Detection limit, in becquerels per litre
 
C , C
Lower and upper confidence limits, of each radionuclide, in becquerels per litre
A A
5 Principle of the measurement
226

Measurement of Ra activity concentration in water is carried out in two separate steps: a sample

[13][14][15]
preparation step, followed by a measurement by gamma-spectrometry.

The sample preparation consists of a filtration of the water sample (see ISO 5667-3) to ensure the

226

measurement of the activity concentration of the Ra soluble fraction. The filtration is followed by a

226
pre-concentration, coprecipitation, and accumulation of decay products of Ra.
226

After filtration and acidification of the water sample, the Ra is coprecipitated into sulfate using a

carrier such as barium nitrate or carbonate. The radium and barium sulfates are then washed, dried,

and weighed. The chemical yield is obtained gravimetrically.

For water samples that may have an existing concentration of soluble barium, another tracer should be

used to avoid a chemical yield above 100 %.
133

When a radiometric tracer, such as Ba is used as an internal standard to assess the recovery yield,

then this recovery yield is used instead of R in the Formulae (2) and (4).
226

The Ra activity concentration of the precipitate is measured by gamma-spectrometry using a high

purity germanium detector with low system background.
235

The presence of other gamma emitters, such as U, in the precipitate can interfere with the

226
quantification of Ra activity.
226

The assessment of the soluble Ra activity concentration is carried out by the measurement of its

214 214

decay products, Pb and Bi, at equilibrium reached four weeks after the last coprecipitation step.

6 Reagents and equipment
6.1 Reagents

Unless otherwise stated, use only reagents of recognized analytical grade and distilled or demineralized

water or water of equivalent purity and no undesirable radioactivity.
6.1.1 Concentrated nitric acid solution (HNO ), 65 % or 69 %.
6.1.2 Nitric acid solution (HNO ), diluted to 2,28 %.
6.1.3 Nitric acid solution (HNO ), diluted to 18 %.
−1 2+
6.1.4 Carrier solution, 10,0 g·l ·Ba .

Slowly dissolve barium nitrate Ba(NO ) (19,0 g) or barium carbonate BaCO (14,3 g) in one litre of

3 2 3

nitric acid solution (6.1.2). The salt mass shall be weighed accurately (better than 1 %) and recorded.

226

It is recommended to use a Ba(NO ) or BaCO reagent with a low Ra activity concentration. The

3 2 3
226

presence of Ra in the reagent shall be controlled using a blank sample prepared with distilled or

demineralized water.
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SIST EN ISO 13165-3:2020
ISO 13165-3:2016(E)
6.1.5 Concentrated sulfuric acid solution (H SO ), 98 %.
2 4
6.1.6 Cellulose ester filter of porosity, 0,45 µm.
6.2 Equipment
Usual laboratory equipment and, in particular, the following:
6.2.1 Peristaltic or membrane pump.
6.2.2 Magnetic bar stirrer.
6.2.3 Centrifuge and tubes.
6.2.4 Precision balance.
6.2.5 Drying oven.
6.2.6 Gas-tight container.
6.2.7 Gamma-spectrometry system, with low background capability.
7 Sampling
The method can be used on water samples up to 100 l.
7.1 Sample collection
The sampling conditions shall comply with ISO 5667-3.

If required, the filtration is carried out during or immediately after collection and before

acidification, otherwise, radioactive material already adsorbed onto the suspended particulate

material can be desorbed.

It is recommended that plastic single-use type containers are used for sample collection.

The volume of the water sample to collect for measurement depends on the detection limits required by

the customer.
7.2 Sample transport and storage
The water sample shall be transported and stored according to ISO 5667-3.

When pre-concentration is desired, acidify the sample to between pH 1 and pH 3 with HNO . Acidification

of the water sample minimizes the loss of radioactive material from solution by adsorption.

The test shall be performed as soon as possible.
8 Procedures
8.1 Blank sample preparation

Prepare a blank with distilled or demineralized water by performing the operations described in step

a) to i) in 8.2.
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8.2 Sample preparation

a) To prevent adsorption effects and proliferation of algae, the water sample is acidified to pH 1 with

nitric acid (see 6.1.1). The water sample volume can be 1 l to 100 l. Acidification of the sample shall

not be performed with hydrochloric acid as barium sulfate is partially soluble in it.

b) Pour dropwise, precisely, 50 ml of carrier solution (see 6.1.4) into the solution to be analysed, with

vigorous stirring. In the case of natural water rich in sulfate ions, such as seawater, the barium and

radium have to be mixed before the sulfate is precipita
...