SIST EN ISO 9698:2015
(Main)Water quality - Determination of tritium activity concentration - Liquid scintillation counting method (ISO 9698:2010)
Water quality - Determination of tritium activity concentration - Liquid scintillation counting method (ISO 9698:2010)
This International Standard specifies the conditions for the determination of tritium activity concentration in samples of environmental water or of tritiated water using liquid scintillation counting. The choice of the analytical procedure, either with or without distillation of the water sample prior to determination, depends on the aim of the measurement and the sample characteristics. Direct measurement of a raw water
sample using liquid scintillation counting has to consider the potential presence of other beta emitter radionuclides. To avoid interference with these radionuclides when they are detected, the quantification of tritium will be performed following the sample treatment by distillation. The Annexes B, D and E describe three distillation procedures. The method is not applicable to the analysis of organically bound tritium; its
determination requires additional chemical processing (such as chemical oxidation or combustion). With suitable technical conditions, the detection limit may be as low as 1 Bq/l. Tritium activity concentrations below 106 Bq/l can be determined without any sample dilution. A prior enrichment step can significantly lower the limit of detection.
Wasserbeschaffenheit - Bestimmung der Aktivitätskonzentration von Tritium - Verfahren mit dem Flüssigszintillationszähler (ISO 9698:2010)
Diese Internationale Norm legt ein Verfahren zur Bestimmung der Aktivitätskonzentration von Tritium in natürlichen Wasserproben oder von tritiiertem Wasser ([3H]H2O) mithilfe eines Flüssigszintillationszählers fest.
Die Auswahl des analytischen Verfahrens, ob mit oder ohne Destillation der Wasserprobe vor der Bestimmung, hängt vom Ziel der Messung sowie von den Eigenschaften der Probe ab (siehe [1], [2], [3]).
Bei der Direktmessung von Rohwasserwasserproben mithilfe des Flüssigszintillationszählers muss das potenzielle Vorhandensein von Beta-Strahlen emittierenden Radionukliden berücksichtigt werden. Um bei Feststellung solcher Radionuklide Störungen mit diesen zu vermeiden, wird die Tritiumquantifizierung nach der Probenbehandlung durch Destillation durchgeführt (siehe [4], [5], [6], [7]). Drei Destillationsverfahren werden in den Anhängen B, D und E beschrieben.
Dieses Verfahren eignet sich nicht für die Analyse von organisch gebundenem Tritium. Diese Bestimmung erfordert weitere chemische Aufarbeitung (wie eine chemische Oxidation oder Verbrennung).
Unter geeigneten technischen Voraussetzungen liegt die Nachweisgrenze bei gerade einmal 1 Bq l-1. Aktivitätskonzentrationen von Tritium unter 106 Bq l-1 können ohne Probenverdünnung bestimmt werden. Eine vorherige Anreicherung kann die Nachweisgrenze beträchtlich senken (siehe [8], [9]).
Qualité de l'eau - Détermination de l'activité volumique du tritium - Méthode par comptage des scintillations en milieu liquide (ISO 9698:2010)
L'ISO 9698:2010 spécifie les conditions de détermination de l'activité volumique du tritium dans des échantillons d'eau environnementale ou d'eau tritiée par comptage des scintillations en milieu liquide.
Le choix du mode opératoire analytique, avec ou sans distillation de l'échantillon d'eau avant la détermination, dépend du but du mesurage et des caractéristiques de l'échantillon.
Le mesurage direct d'un échantillon d'eau brute par comptage des scintillations en milieu liquide doit prendre en compte la présence potentielle d'autres radionucléides émetteurs bêta. Pour éviter des interférences avec ces radionucléides lorsqu'ils sont détectés, la quantification du tritium est effectuée après avoir traité l'échantillon par distillation. Trois modes opératoires de distillation sont décrits.
Cette méthode n'est pas applicable à l'analyse du tritium organiquement lié; sa détermination nécessite un traitement chimique supplémentaire (telle une oxydation chimique ou une combustion).
Dans les conditions techniques adéquates, la limite de détection peut être réduite à 1 Bq l-1. Les activités volumiques du tritium inférieures à 106 Bq l-1 peuvent être déterminées sans dilution de l'échantillon. Une étape d'enrichissement préalable peut abaisser de manière significative la limite de détection.
Kakovost vode - Določevanje koncentracije aktivnosti tritija - Metoda štetja s tekočinskim scintilatorjem (ISO 9698:2010)
Ta mednarodni standard opisuje pogoje za določevanje koncentracije aktivnosti tritija v vzorcih okoljske vode ali tritirane vode s štetjem s tekočinskim scintilatorjem. Izbira analitskega postopka z destilacijo ali brez destilacije vzorca vode pred določevanjem je odvisna od cilja merjenja in lastnosti vzorca. Pri neposredni meritvi vzorca neobdelane vode s štetjem s tekočinskim scintilatorjem je treba upoštevati potencialno prisotnost drugih beta oddajnih radionuklidov. Za preprečevanje interference s temi radionuklidi, ko se zaznajo, se po obdelavi vzorca z destilacijo izvede kvantifikacija tritija. V dodatkih B, D in E so opisani trije postopki destilacije. Metoda se ne uporablja za analizo organsko vezanega tritija, ki za določevanje zahteva dodatno kemično predelavo (na primer kemično oksidacijo ali zgorevanje). Pod primernimi tehničnimi pogoji je lahko meja detekcije nizka, in sicer do 1 Bq/l. Koncentracije aktivnosti tritija pod 106 Bq/l se lahko določijo brez redčenja vzorca. Predhodni korak obogatitve lahko znatno zniža mejo detekcije.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 9698:2015
01-oktober-2015
.DNRYRVWYRGH'RORþHYDQMHNRQFHQWUDFLMHDNWLYQRVWLWULWLMD0HWRGDãWHWMDV
WHNRþLQVNLPVFLQWLODWRUMHP ,62
Water quality - Determination of tritium activity concentration - Liquid scintillation
counting method (ISO 9698:2010)
Wasserbeschaffenheit - Bestimmung der Aktivitätskonzentration von Tritium - Verfahren
mit dem Flüssigszintillationszähler (ISO 9698:2010)
Qualité de l'eau - Détermination de l'activité volumique du tritium - Méthode par
comptage des scintillations en milieu liquide (ISO 9698:2010)
Ta slovenski standard je istoveten z: EN ISO 9698:2015
ICS:
13.060.60 Preiskava fizikalnih lastnosti Examination of physical
vode properties of water
SIST EN ISO 9698:2015 en,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 9698:2015
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SIST EN ISO 9698:2015
EUROPEAN STANDARD
EN ISO 9698
NORME EUROPÉENNE
EUROPÄISCHE NORM
July 2015
ICS 13.080; 13.060.60
English Version
Water quality - Determination of tritium activity concentration -
Liquid scintillation counting method (ISO 9698:2010)
Qualité de l'eau - Détermination de l'activité volumique du Wasserbeschaffenheit - Bestimmung der
tritium - Méthode par comptage des scintillations en milieu Aktivitätskonzentration von Tritium - Verfahren mit dem
liquide (ISO 9698:2010) Flüssigszintillationszähler (ISO 9698:2010)
This European Standard was approved by CEN on 16 July 2015.
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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, 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: Avenue Marnix 17, B-1000 Brussels
© 2015 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 9698:2015 E
worldwide for CEN national Members.
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SIST EN ISO 9698:2015
EN ISO 9698:2015 (E)
Contents Page
European foreword .3
2
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SIST EN ISO 9698:2015
EN ISO 9698:2015 (E)
European foreword
The text of ISO 9698:2010 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 9698:2015 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 January 2016, and conflicting national standards shall be withdrawn at
the latest by January 2016.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] 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, Former Yugoslav Republic of Macedonia, France, Germany, Greece,
Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.
Endorsement notice
The text of ISO 9698:2010 has been approved by CEN as EN ISO 9698:2015 without any modification.
3
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SIST EN ISO 9698:2015
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SIST EN ISO 9698:2015
INTERNATIONAL ISO
STANDARD 9698
Second edition
2010-12-15
Water quality — Determination of tritium
activity concentration — Liquid
scintillation counting method
Qualité de l'eau — Détermination de l'activité volumique du tritium —
Méthode par comptage des scintillations en milieu liquide
Reference number
ISO 9698:2010(E)
©
ISO 2010
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SIST EN ISO 9698:2015
ISO 9698:2010(E)
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ii © ISO 2010 – All rights reserved
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SIST EN ISO 9698:2015
ISO 9698:2010(E)
Contents Page
Foreword .iv
Introduction.v
1 Scope.1
2 Normative references.1
3 Symbols, definitions and units .2
4 Principle .3
5 Reagents and equipment.3
6 Sampling and samples.5
7 Procedure.6
8 Expression of results.8
9 Test report.10
Annex A (informative) Numerical applications .12
Annex B (informative) Distillation of large volume sample .14
Annex C (informative) Internal standard methods .17
Annex D (informative) Distillation of small volume sample.19
Annex E (informative) Screening method for wet matrices.22
Bibliography.24
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SIST EN ISO 9698:2015
ISO 9698:2010(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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 9698 was prepared by Technical Committee ISO/TC 147, Water quality.
This second edition cancels and replaces the first edition (ISO 9698:1989), which has been technically
revised.
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SIST EN ISO 9698:2015
ISO 9698:2010(E)
Introduction
The tritium present in the environment is of natural origin and man made. As a result of atmospheric nuclear
weapon testing, emissions from nuclear engineering installations, and the application and processing of
isotopes, relatively large amounts of tritium have been released to the environment. Despite the low dose
factor associated to tritium, monitoring of tritium activity concentrations in the environment is necessary in
order to follow its circulation in the hydrosphere and biosphere.
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SIST EN ISO 9698:2015
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SIST EN ISO 9698:2015
INTERNATIONAL STANDARD ISO 9698:2010(E)
Water quality — Determination of tritium activity
concentration — Liquid scintillation counting method
WARNING — This International 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 International Standard
be carried out by suitably trained staff.
1 Scope
This International Standard specifies the conditions for the determination of tritium activity concentration in
3
samples of environmental water or of tritiated water ([ H]H O) using liquid scintillation counting.
2
The choice of the analytical procedure, either with or without distillation of the water sample prior to
determination, depends on the aim of the measurement and the sample characteristics (see References [1],
[2], [3]).
Direct measurement of a raw water sample using liquid scintillation counting has to consider the potential
presence of other beta emitter radionuclides. To avoid interference with these radionuclides when they are
detected, the quantification of tritium will be performed following the sample treatment by distillation (see
References [4], [5], [6], [7]). Three distillation procedures are described in Annexes B, D and E.
The method is not applicable to the analysis of organically bound tritium; its determination requires additional
chemical processing (such as chemical oxidation or combustion).
−1
With suitable technical conditions, the detection limit may be as low as 1 Bq l . Tritium activity concentrations
6 −1
below 10 Bq l can be determined without any sample dilution. A prior enrichment step can significantly
lower the limit of detection (see References [8], [9]).
2 Normative references
The following referenced documents are indispensable for the application 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 5667-1, Water quality — Sampling — Part 1: Guidance on the design of sampling programmes and
sampling techniques
ISO 5667-3, Water quality — Sampling — Part 3: Guidance on the preservation and handling of water
samples
ISO 5667-14, Water quality — Sampling — Part 14: Guidance on quality assurance of environmental water
sampling and handling
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
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SIST EN ISO 9698:2015
ISO 9698:2010(E)
ISO/IEC Guide 98-3:2008, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in
measurement (GUM:1995)
ISO/IEC Guide 99:2007, International vocabulary of metrology — Basic and general concepts and associated
terms (VIM)
3 Symbols, definitions and units
For the purposes of this document, the definitions, symbols and units defined in ISO 80000-10,
ISO/IEC Guide 98-3 and ISO/IEC Guide 99, as well as the following symbols, apply.
Maximum energy for the beta emission, in kilo-electronvolts
β
max
V Volume of test sample, in litres
m Mass of test sample, in kilograms
Mass density of the sample, in grams per litre
ρ
c Activity concentration, in becquerels per litre
A
a Activity per unit of mass, in becquerels per kilogram
A Activity of the calibration source, in becquerels
t Background counting time, in seconds
0
t Sample counting time, in seconds
g
t Calibration counting time, in seconds
s
n Number of repetitions
r Background count rate in the repetition i, per second
0i
r Mean background count rate for i repetitions, per second
0
r Sample count rate in the repetition i, per second
gi
r Mean sample count rate for i repetitions, per second
g
r Calibration count rate, per second
s
Detection efficiency
ε
Efficiency measured for each of the working standards to elaborate the quench curve
ε
q
f Quench factor
q
u(c ) Standard uncertainty associated with the measurement result, in becquerels per litre
A
U
Expanded uncertainty, calculated by U = k ⋅ u(c ) with k = 1, 2,…, in becquerels per litre
A
*
Decision threshold, in becquerels per litre
c
A
#
Detection limit, in becquerels per litre
c
A
<>
Lower and upper limits of the confidence interval, in becquerels per litre
cc,
A A
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SIST EN ISO 9698:2015
ISO 9698:2010(E)
4 Principle
The test portion is mixed with the scintillation cocktail in a counting vial to obtain a homogeneous medium.
Electrons emitted by tritium transfer their energy to the scintillation medium. Molecules excited by this process
return to their ground state by emitting photons that are detected by photodetectors.
The electric pulses emitted by the photodetectors are amplified, sorted (in order to remove random events)
and analysed by the electronic systems and the data analysis software. The count rate of these photons
allows the determination of the test portion activity, after correcting for the background count rate and
detection efficiency.
In order to determine the background count rate, a blank sample is prepared in the same way as the test
portion. The blank sample is prepared using a reference water of the lowest activity available, also sometimes
called “dead water”.
The detection efficiency is determined with a sample of a standard of aqueous tritium (calibration source), or a
dilution of this standard with water for the blank, measured in the same conditions as the test portion.
The conditions to be met for the blank sample, the test portion and the calibration source are the following:
⎯ same type of counting vial;
⎯ same filling geometry;
⎯ same ratio between test portion and scintillation cocktail;
⎯ temperature stability of the detection equipment;
⎯ value of quench indicating parameter included in calibration curve.
IMPORTANT — Quench correction: If the measurement results are affected by particular conditions of
chemical quenching, it is recommended that a quench curve be established. It is important to choose
a suitable chemical quenching agent for the type of quenching suspected in the sample.
NOTE For high activity and highly quenched samples, it may be practical to use an internal standard method, as
described in Annex C.
5 Reagents and equipment
Use only reagents of recognized analytical grade.
5.1 Reagents
5.1.1 Water for the blank
The water used for the blank shall be as free as possible of chemical impurities to avoid quenching, of
radioactive impurities (see Reference [10]) and with an activity concentration of tritium negligible in
comparison with the activities to be measured.
For example, a water sample with a low tritium activity concentration can be obtained from (deep)
subterranean water kept in a well-sealed borosilicate glass bottle in the dark at a controlled temperature
(ISO 5667-3). This blank water sample shall be kept physically remote from any tritium-containing material
−1
(see Clause 4, important notice). Determine the tritium activity concentration (t = 0), in Bq l , of this water and
note the date (t = 0) of this determination (see Clause 4, Note).
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ISO 9698:2010(E)
It is advisable to keep an adequate quantity of blank water in stock and to make small working amounts from it
for immediate use, as required. Contamination with tritium (e.g. from water vapour in the air and from tritium
sources such as luminous watches and gas chromatographs) or other radioactive species should be avoided.
−1
As the activity is becoming non-negligible for activities around 1 Bq l , it is necessary to use a blank water
measured to ensure the “absence” of tritium. The tritium activity concentration in the blank water can be
3
determined by enrichment followed by liquid scintillation counting or from the measurement of He by mass
−1
spectrometry. Preferably use blank water with a tritium activity concentration of less than 0,5 Bq l .
When the volume of blank water is sufficiently large, e.g. 10 l to 20 l, and well-sealed, tritium activity
concentration will remain stable for years, although it is advisable to determine the tritium activity
concentration at predetermined intervals, e.g. every year.
5.1.2 Calibration source solution
In order to avoid cross-contamination, prepare, in a suitable location which is remote from the area where the
tritium analyses are to be carried out, weigh and pour into a weighed volumetric flask (for example, 100 ml)
3
the requisite quantity of a concentrated tritium ([ H]H O) standard solution, so that the tritium activity
2
concentration will generate sufficient counts to reach the required measurement uncertainty after dilution with
blank water and thorough mixing. Calculate the tritium activity concentration of the resulting calibration source
solution (t = 0). Note the date at which the standard solution was made up (t = 0).
The tritium activity concentration of the calibration source solution at time t at which the samples are
measured must be corrected for radioactive decay.
5.1.3 Scintillation solution
The scintillation cocktail is chosen according to the characteristics of the sample to be analysed and according
to the properties of the detection equipment (see Reference [11]).
It is recommended to use a good hydrophilic scintillation cocktail, especially for the measurement of usual
environmental water.
The characteristics of the scintillation cocktail must allow the mixture to be homogeneous and stable.
For the direct measurement of raw waters containing particles in suspension, it is recommended that a
scintillation cocktail leading to a gel-type mixture be used.
It is recommended to:
⎯ store in the dark and, particularly just before use, avoid exposure to direct sunlight or fluorescent light in
order to prevent interfering luminescence;
⎯ comply with the storage conditions specified by the scintillation cocktail supplier.
The mixtures (scintillation cocktail and test sample) should be disposed of as chemical waste, and, depending
on the radioactivity, may require disposal as radioactive waste.
5.1.4 Quenching agent
The following are examples of chemical quenching agents: nitric acid, acetone, organochloride compounds,
nitromethane.
NOTE Some quenching agents are dangerous or toxic.
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ISO 9698:2010(E)
5.2 Equipment
Laboratory equipment, such as pipettes and balances, shall be employed that enables the expected/agreed
data quality objectives to be achieved, as well as the quantification of the uncertainty attached to the
measurement.
NOTE Control of the quantity of liquid scintillation cocktail used in source preparation is essential to achieve
consistent data quality.
5.2.1 Liquid scintillation counter
Liquid scintillation counter, preferably with an automatic sample transfer. Operation at constant temperature is
recommended following the manufacturer's instructions. Depending on the limit of detection to be reached, a
liquid scintillation counter with a low-level configuration may be needed. The method specified in this
International Standard relates to the widely used liquid scintillation counters with vials that hold about 20 ml.
When other vials are used with appropriate counters, the described method shall be adapted accordingly.
5.2.2 Counting vials
Different types of scintillation vials exist, manufactured using a range of materials. The most common are
glass vials and polyethylene vials. Glass vials allow visual inspection of the scintillation medium, but have an
40
inherent background, due to the presence of K. However, some organic solvents contained in scintillation
cocktails diffuse through the polyethylene, accelerating the degradation of the mixture.
Other types of vials exist:
40
⎯ glass vials with low level of K, will exhibit a lower background than “normal” glass vials;
⎯ for the determination of very low tritium concentration, the use of polytetrafluoroethylene (PTFE) vials or
polyethylene vials with an inner layer of PTFE on the inside vial wall is strongly recommended. Diffusion
of organic solvents is then slower through PTFE than through polyethylene. These vials are used for long
counting times with very low-level activity to be measured.
Generally, the vials are single use. If the vial is reused, it is necessary to apply an efficient cleaning procedure.
To prevent interfering luminescence, the counting vials should be kept in the dark and should not be exposed
to direct sunlight or fluorescent light, particularly just before use.
Toluene-based scintillation solutions may physically distort polyethylene and should therefore not be used in
combination with polyethylene counting vials. Diffusion of organic solvents into and through the polyethylene
walls is also a serious drawback of polyethylene vials.
6 Sampling and samples
6.1 Sampling
Conditions of sampling shall conform to ISO 5667-1.
It is not advised to acidify the sample due to the high chemical quench caused by acids, and the potential
presence of tritium in the acid, as specified in ISO 5667-3.
It is important that the laboratory receive a representative sample, unmodified during the transport or storage
and in an undamaged container. It is recommended to use a glass flask and to fill it to the maximum, to
minimize tritium exchange with the atmospheric moisture.
For low level activity measurements, it is important to avoid any contact between sample and atmosphere
during the sampling.
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ISO 9698:2010(E)
6.2 Sample storage
If required, the sample shall be stored in compliance with ISO 5667-3. If the storage duration exceeds that
specified in ISO 5667-3, it is advisable to store the samples in glass flasks.
7 Procedure
7.1 Sample preparation
7.1.1 Direct procedure
Measurement of the test sample is generally performed on raw water without removal of suspended matter. If
the activity of a filtered or centrifuged sample is to be measured, the removal of suspended matter shall be
performed as soon as possible after the sampling (see ISO 5667-3).
7.1.2 Distillation
Examples of distillation procedures are given in Annexes B, D and E.
Distillation shall avoid isotopic fractionation (see Reference [12]).
Distillation or any other physic-chemical treatment of water is not appropriate for simultaneous measurement
14
of tritium and C.
7.2 Preparation of the sources to be measured
Known quantity of test sample and scintillation cocktail are introduced into the counting vial.
After closing the vial, it shall be thoroughly shaken to homogenize the mixture.
The vial identification shall be written on the top of the vial stopper. The storage time depends upon the
scintillation mixture, the mixture stability and the nature of the sample. It is recommended to perform the
measurement as soon as any photoluminescence or static electricity effects have become negligible, e.g.
after 12 h.
In order to reduce photoluminescence effects, it is recommended that the above mentioned operations take
place in dimmed light (preferably light from an incandescent source or red light); in addition, direct sunlight or
fluorescent light should be avoided.
7.3 Counting procedure
The measurement conditions (measurement time, blank sample, number of cycles or repetitions) will be
defined according to the uncertainty and detection limit to be achieved.
7.3.1 Control and calibration
Statistical control of the detection system shall be monitored by measurement of suitable reference
background and reference sources usually provided by the equipment supplier, for example in compliance
[13]
with ISO 8258 .
The measurement of the blank sample is performed before each analysis or each series of sample
measurement in representative conditions of each type of measurement (Clause 4).
The detection efficiency is determined with a sample of a standard of aqueous tritium (calibration source), or a
dilution of this standard with water for the blank, measured in the same conditions as the test portion.
6 © ISO 2010 – All rights reserved
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SIST EN ISO 9698:2015
ISO 9698:2010(E)
Using direct measurement, it is essential to generate a quench curve for each type of water measured. The
quench curve is valid only for:
⎯ a given type of measurement equipment;
⎯ a given type of scintillation cocktail;
⎯ a given ratio of scintillation cocktail and test sample.
The quench curve is obtained with a series of working standards (10 for example), presenting different
quench. The matrix of the working standards is representative of matrix of the samples to be measured (same
scintillation liquid, same ratio scintillation liquid-test sample). The working standards may be prepared as
follows:
⎯ similar quantity of certified standard tritiated water solution in each vial; the activity of the certified
standard must be sufficient for the counting ratio to be defined with a known statistical precision, even in
the case of a strong quench;
⎯ the standard is completed with reference water until the volume of test sample is reached;
⎯ the scintillation cocktail is added to obtain the
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