prEN ISO 20899

Water quality - Plutonium and neptunium - Test method using ICP-MS (ISO/DIS 20899:2026)

This document specifies methods used to determine the concentration of plutonium and neptunium isotopes in water by inductively coupled plasma mass spectrometry (ICP-MS) (239Pu, 240Pu, 241Pu and 237Np). The concentrations obtained can be converted into activity concentrations of the different isotopes[9].
Due to its relatively short half-life and 238U isobaric interference, 238Pu can hardly be measured by this method. To quantify this isotope, other techniques can be used (ICP-MS with collision-reaction cell, ICP-MS/MS with collision-reaction cell or chemical separation). Alpha spectrometry measurement, as described in ISO 13167[10], is currently used[11].
This method is applicable to all types of water having a saline load less than 1 g·l−1. A dilution of the sample is possible to obtain a solution having a saline load and activity concentrations compatible with the preparation and the measurement assembly.
A filtration at 0,45 μm is needed for determination of dissolved nuclides. Acidification and chemical separation of the sample are always needed.
The limit of quantification depends on the chemical separation and the performance of the measurement device.
This method covers the measurement of those isotopes in water in activity concentrations between around[12][13]:
— 1 mBq·l−1 to 5 Bq·l−1 for 239Pu, 240Pu and 237Np;
— 1 Bq·l−1 to 5 Bq·l−1 for 241Pu.
In both cases, samples with higher activity concentrations than 5 Bq·l−1 can be measured if a dilution is performed before the chemical separation.
It is possible to measure 241Pu following a pre-concentration step of at least 1 000.

Wasserbeschaffenheit - Plutonium und Neptunium - Verfahren mittels ICP‑MS (ISO/DIS 20899:2026)

Qualité de l'eau - Plutonium et neptunium - Méthode d'essai par ICP-MS (ISO/DIS 20899:2026)

Le présent document décrit des méthodes permettant de déterminer la concentration des isotopes du plutonium et du neptunium dans l'eau, par spectrométrie de masse avec plasma à couplage inductif (ICP-MS) (239Pu, 240Pu, 241Pu et 237Np). Les concentrations obtenues peuvent être converties en activités volumiques des différents isotopes[9].
En raison de sa période relativement courte et des interférences isobariques de 238U, 238Pu est difficilement mesurable par cette méthode. Pour quantifier cet isotope, il est possible d'utiliser d'autres techniques (ICP-MS avec cellule de collision-réaction, ICP-MS/MS avec cellule de collision-réaction ou séparation chimique). Un mesurage par spectrométrie alpha, comme décrit dans l'ISO 13167[10], est couramment réalisé[11].
La présente méthode est applicable à tous types d'eau ayant une charge saline inférieure à 1 g·l−1. Une dilution de l'échantillon est possible afin d'obtenir une solution ayant une charge saline et une activité volumique compatibles avec la préparation et l'appareillage de mesure.
Une filtration à 0,45 μm est nécessaire pour déterminer les nucléides dissous. Une acidification et une séparation chimique de l'échantillon sont toujours nécessaires.
La limite de quantification est fonction de la séparation chimique et des performances du dispositif de mesure.
Cette méthode couvre le mesurage des isotopes présents dans les eaux dont l'activité volumique est approximativement comprise[12][13]:
— entre 1 mBq·l-1 et 5 Bq·l-1 pour 239Pu, 240Pu et 237Np;
— entre 1 Bq·l-1 et 5 Bq·l-1 pour 241Pu.
Dans les deux cas, des échantillons ayant une activité volumique supérieure à 5 Bq·l-1 peuvent être soumis au mesurage s'ils sont dilués avant la séparation chimique.
Il est possible de mesurer le 241Pu après une étape de préconcentration d'au moins 1 000.

Kakovost vode - Plutonij in neptunij - Preskusna metoda z masno spektroskopijo z induktivno sklopljeno plazmo (ICP-MS)

General Information

• Status: Not Published
• Publication Date: 19-Sep-2027
• ICS: 13.280 - Radiation protection
• Technical Committee: CEN/TC 230 - Water analysis
• Drafting Committee: CEN/TC 230 - Water analysis
• Current Stage: 4060 - Closure of enquiry - Enquiry
• Start Date: 14-May-2026
• Due Date: 07-Jan-2026
• Completion Date: 14-May-2026
• Ref Project: oSIST prEN ISO 20899:2026 - Water quality - Plutonium and neptunium - Test method using ICP-MS

Overview

prEN ISO 20899:2026 – "Water quality – Plutonium and neptunium – Test method using ICP-MS" establishes standardized procedures for measuring plutonium and neptunium isotope concentrations in water using inductively coupled plasma mass spectrometry (ICP-MS). Developed by CEN and aligned with ISO/DIS 20899:2026, this draft standard addresses the need for reliable testing of key transuranic isotopes-specifically ^239Pu, ^240Pu, ^241Pu, and ^237Np-in various water types, supporting both environmental monitoring and regulatory compliance.

The method further supports the conversion of measured mass concentrations into activity concentrations, a crucial step for regulatory reporting and risk assessment. While the protocol provides robust determination for several isotopes, it recognizes the analytical limitations when quantifying ^238Pu due to isobaric interference with ^238U and recommends complementary techniques where necessary.

Key Topics

• Target Isotopes and Applicability: The standard focuses on ^239Pu, ^240Pu, ^241Pu, and ^237Np, delivering applicable methods for measuring these in waters with salinity <1 g/L, including potable, surface, groundwater, marine, and wastewater.
• ICP-MS as Core Technology: Utilizes ICP-MS for rapid, highly sensitive multi-isotope detection. The standard prescribes guidelines on calibration, interference management, and method validation to ensure accuracy.
• Sample Handling Protocols:
  • Filtration: Required at 0.45 μm to isolate dissolved radionuclides.
  • Acidification and Chemical Separation: Ensures the stability and isolation of target analytes.
• Limits of Detection and Quantification:
  • Addresses measuring activity concentrations down to ~1 mBq/L for ^239Pu, ^240Pu, ^237Np, and ~1 Bq/L for ^241Pu.
  • Enables handling higher activities through dilution or pre-concentration, supporting flexibility in both routine and emergency scenarios.
• Interference Management: Details the need for robust chemical separation and considers isobaric, polyatomic, and tailing interferences-especially from uranium isotopes and other actinides.

Applications

Implementing prEN ISO 20899 offers practical value in several domains:

• Environmental Monitoring: Essential for assessing the impact of nuclear activities, accidental releases, or legacy contamination on aquatic systems.
• Drinking Water Safety: Supports water utilities and regulatory bodies in meeting World Health Organization (WHO) guidance and national limits for radionuclide concentrations in public water supplies.
• Industrial and Wastewater Analysis: Aids in compliance verification for nuclear, mining, and other industries required to monitor and report radioactive discharges.
• Emergency Response: Provides validated protocols that can be deployed swiftly in incidents involving radiological contamination of water.
• Research and Quality Assurance: Serves as a reference for laboratory method development, inter-lab comparability, and proficiency testing for radiochemical analysis.

Related Standards

prEN ISO 20899:2026 references and complements several international standards in water quality and radiochemical measurement:

• ISO 13167: For alpha spectrometry of plutonium isotopes, especially ^238Pu.
• ISO 5667-series: Guidance on water sampling, preservation, and handling procedures, crucial for sample integrity.
• ISO 17294-1 & -2: Details general and specific requirements for ICP-MS in water analysis, underpinning instrument operation in this method.
• ISO/IEC 17025: Quality management and competence for testing and calibration laboratories.
• ISO/IEC Guide 98-3: Principles and guidelines for the expression of measurement uncertainty.

By adopting prEN ISO 20899:2026, laboratories and regulatory agencies ensure data quality, comparability, and compliance with internationally recognized best practices for water quality monitoring of plutonium and neptunium isotopes using ICP-MS.

Standards Content (Sample)

SLOVENSKI STANDARD
01-april-2026
Kakovost vode - Plutonij in neptunij - Preskusna metoda z masno spektroskopijo z
induktivno sklopljeno plazmo (ICP-MS)
Water quality - Plutonium and neptunium - Test method using ICP-MS
Wasserbeschaffenheit - Plutonium und Neptunium - Verfahren mittels ICP-MS
Qualité de l'eau - Plutonium et neptunium - Méthode d'essai par ICP-MS
Ta slovenski standard je istoveten z: prEN ISO 20899
ICS:
13.060.60 Preiskava fizikalnih lastnosti Examination of physical
vode properties of water
13.280 Varstvo pred sevanjem Radiation protection
17.240 Merjenje sevanja Radiation measurements
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
International
Standard
ISO/DIS 20899
ISO/TC 147/SC 3
Water quality — Plutonium and
Secretariat: AFNOR
neptunium — Test method using
Voting begins on:
ICP-MS
2026-02-19
Qualité de l'eau — Plutonium et neptunium — Méthode d'essai
Voting terminates on:
par ICP-MS
2026-05-14
ICS: 13.060.60; 17.240; 13.280
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
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USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
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BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS.
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Reference number
ISO/DIS 20899:2026(en)
DRAFT
ISO/DIS 20899:2026(en)
International
Standard
ISO/DIS 20899
ISO/TC 147/SC 3
Water quality — Plutonium and
Secretariat: AFNOR
neptunium — Test method using
Voting begins on:
ICP-MS
Qualité de l'eau — Plutonium et neptunium — Méthode d'essai
Voting terminates on:
par ICP-MS
ICS: 13.060.60; 17.240; 13.280
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2026
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
BE CONSIDERED IN THE LIGHT OF THEIR
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or ISO’s member body in the country of the requester.
NATIONAL REGULATIONS.
ISO copyright office
RECIPIENTS OF THIS DRAFT ARE INVITED
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TO SUBMIT, WITH THEIR COMMENTS,
CH-1214 Vernier, Geneva
NOTIFICATION OF ANY RELEVANT PATENT
Phone: [phone]
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Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ISO/DIS 20899:2026(en)
ii
ISO/DIS 20899:2026(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 2
3 Terms and definitions . 2
4 Symbols . 2
5 Principle . 3
6 Sampling and sample storage . 5
7 Chemical reagents and apparatus . 5
7.1 Chemical reagents .5
7.2 Apparatus .5
8 Sample preparation . 6
8.1 General .6
8.2 Storage .6
8.3 Chemical separation .6
9 Measurement procedure . 6
9.1 Instrument verification .6
9.2 Quantification with internal calibration and isotopic dilution .7
10 Expression of results . 7
10.1 General .7
10.2 Mass bias evaluation .7
10.3 Internal calibration and isotopic dilution .8
11 Uncertainties for isotopic dilution. 8
12 Instrumental limit of detection . 9
13 Limit of quantification . 9
14 Activity concentration determination . 9
15 Test report . 9
Annex A (informative) Chemical separation of plutonium and neptunium by specific resin .11
Bibliography .13

iii
ISO/DIS 20899:2026(en)
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 of the voluntary nature of standards, 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 www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 147, Water quality, Subcommittee SC 3,
Radioactivity measurements.
This second edition cancels and replaces the first edition (ISO 20899:2018), which has been technically
revised.
The main changes are as follows:
— The scope was clarified
— Addition of recommendations regarding potential interferences
— The common SC 3 template for Introduction was implemented
— The common SC 3 template for Test report was implemented
— The bibliographical references were updated
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
ISO/DIS 20899:2026(en)
Introduction
Radionuclides are present throughout the environment; thus, water bodies (e.g. surface waters, ground
waters, sea waters) contain radionuclides, which can be of either natural or anthropogenic origin:
3 14 40
— Naturally-occurring radionuclides, including H, C, K and those originating from the thorium and
210 210 222 226 228 227 232 231 234 238
uranium decay series, in particular Pb, Po, Rn, Ra, Ra, Ac, Th, Pa, U, and U,
can be found in water bodies due to either natural processes (e.g., desorption from the soil and runoff by
rain water) or released from technological processes involving naturally occurring radioactive materials
(e.g. mining, mineral processing, oil, gas, and coal production, water treatment and the production and
use of phosphate fertilisers);
55 59 60 63 90 99 137
— Anthropogenic radionuclides such as Fe, Ni, Co, Ni, Sr, Tc, Cs transuranic elements (e.g., Np,
60 137
Pu, Am, and Cm), and some gamma emitting radionuclides such as Co and Cs can also be found in
natural waters. Small quantities of anthropogenic radionuclides can be discharged from nuclear facilities
to the environment as a result of authorized routine releases. The radionuclides present in liquid effluents
[1]
are usually controlled before being discharged to the environment and water bodies. Anthropogenic
radionuclides used for medical and industrial applications can be released to the environment after use.
Anthropogenic radionuclides are also found in waters due to contamination from fallout resulting from
above-ground nuclear detonations and accidents such as those that have occurred at the Chornobyl and
Fukushima nuclear facilities.
Radionuclide activity concentrations in water bodies can vary according to local geological characteristics
and climatic conditions and can be locally and temporally enhanced by releases from nuclear facilities
[2][3]
during planned, existing, and emergency exposure situations. Some drinking water sources can thus
contain radionuclides at activity concentrations that can present a human health risk. The World Health
[4]
Organization (WHO) recommends to routinely monitor radioactivity in drinking waters and to take
proper actions when needed to minimize the health risk.
National regulations usually specify the activity concentration limits that are authorized in drinking waters,
water bodies, and liquid effluents to be discharged to the environment. These limits can vary for planned,
existing, and emergency exposure situations. As an example, during either a planned or existing situation,
[4] 239 240 237 [4]
the WHO guidance level in drinking water are respectively 1 Bq·l−1 for Pu, Pu, Np and 10 Bq·l−1
for Pu, see NOTES 1 and 2. Compliance with these limits is assessed by measuring radioactivity in water
samples and by comparing the results obtained, with their associated uncertainties to these limits, as
[5]
specified by ISO/IEC Guide 98-3 and ISO 5667-20 ,
NOTE 1 If the WHO guidance level is not specified in Annex 6 of Reference [4], the value has been calculated using
the formula provided in Reference [4] and the dose coefficient data from References [6] and [7].
NOTE 2 The guidance level calculated in Reference [4] is the activity concentration that results in an effective dose
-1 -1
of 0,1 mSv·a for members of the public for an intake of 2 l·d of drinking water for one year. This is an effective
dose that represents a very low level of risk to human health and which is not expected to give rise to any detectable
[4]
adverse health effects .
239 240 241
This document contains method to support laboratories, which need to determine Pu, Pu, Pu and
Np in water samples. The method described in this document can be used for various types of waters (see
Clause 1). Minor modifications such as sample volume and counting time can be made if needed to ensure
that the decision threshold, detection limit, and uncertainties are below the required limits. This can be
done for several reasons such as emergency situations, lower national guidance limits, and operational
requirements.
v
DRAFT International Standard ISO/DIS 20899:2026(en)
Water quality — Plutonium and neptunium — Test method
using ICP-MS
WARNING — Persons using this document should be familiar with normal laboratory practice. This
document 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.
IMPORTANT — It is absolutely essential that tests conducted according to this document be carried
out by suitably trained staff.
1 Scope
239 240 241 237
This document specifies methods to determine the Pu, Pu, Pu and Np by inductively coupled
plasma mass spectrometry (ICP-MS). The mass concentrations obtained can be converted into activity
concentrations.
238 238
Due to its relatively short half-life and U isobaric interference, Pu can hardly be measured by this
method. To quantify Pu isotope by mass spectrometry, other techniques can be used (ICP-MS with
collision-reaction cell, ICP-MS/MS with collision-reaction cell or chemical separation). Alpha spectrometry
[8] [9]
measurement, as described in ISO 13167, is currently used .
The method is applicable to test samples of supply/drinking water, rainwater, surface and ground water,
marine water, as well as cooling water, industrial water, domestic, and industrial wastewater after proper
sampling and handling, and test sample preparation.
A chemical separation of Np and Pu, with quantitative removal of all other elements (including uranium,
americium, etc.) is mandatory, given all the potential interferences that may bias the measurement or lead
to false positives. Chemical separations can eliminate most of the U. However, use of reagents, glassware,
and atmosphere for the chemical separation, will also add U to the samples and prevent measurement of
Pu.
The limit of detection depends on the sample volume, the instrument used, the background count rate, the
detection efficiency, the counting time, and the chemical yield. The detection limit of the method described
-1 239 240
in this document, using currently available ICP-MS apparatus, is approximately 1 mBq·l for Pu, Pu,
237 -1 241
Np and 1 Bq·l for Pu, which is lower or of the same order of magnitude than the WHO criteria for safe
-1 239 240 237 -1 241 [4]
consumption of drinking water (1 mBq·l for Pu, Pu, Np and 10 Bq·l for Pu ).This method covers
[10][11]
the measurement of those radionuclides in water at activity concentrations between approximately :
−1 −1 239 240 237
— 1 mBq·l to 5 Bq·l for Pu, Pu and Np;
−1 −1 241
— 1 Bq·l to 5 Bq·l for Pu.
−1
Samples with higher activity concentrations than 5 Bq·l can be measured if a dilution is performed.
The higher is the concentration factor, the lower are the LD and LQ expressed in Bq/L of water. A
preconcentration is especially useful for the quantification of 241Pu that is usually the less abundant isotope
of plutonium.
The method described in this document is applicable in the event of an emergency situation.
239 240 241 237
Filtration of the test sample is necessary. The analysis of Pu, Pu, Pu and Np adsorbed to suspended
matter is not covered by this method. The analysis of the insoluble fraction requires a mineralization step
that is not covered by this document. In this case, the measurement is performed separately on each phase
or the total phase.
ISO/DIS 20899:2026(en)
It is the user’s responsibility to ensure the validity of this test method for the water samples tested.
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/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in
me a s ur ement (GUM: 1995)
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: Preservation and handling of water samples
ISO 5667-10, Water quality — Sampling — Part 10: Guidance on sampling of waste waters
ISO 17294-1:2024, Water quality — Application of inductively coupled plasma mass spectrometry (ICP-MS) —
Part 1: General requirements
ISO 17294-2:2023, Water quality — Application of inductively coupled plasma mass spectrometry (ICP-MS) —
Part 2: Determination of selected elements including uranium isotopes
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
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC Guide 98-3, ISO/IEC Guide 99
and ISO 80000-10 apply.
4 Symbols
−1
C Specific activity corresponding to one gram of the radionuclide Bq·g
s
−1
C Activity concentration corresponding to the mass concentration ρ measured for a Bq·l
given radionuclide
−1
ρ Mass concentration of the analyte for a given radionuclide per sample unit volume. μg·l
Mass concentration of internal standard radionuclide element per unit volume of the
−1
ρ μg·l
T
internal standard solution.
242 239
m Mass of the tracer solution added to Pu and/or Np g
T
−1
u(ρ) Standard uncertainty associated with the measurement result μg·l
U(x) Expanded uncertainty and the coverage factor k with k = 1, 2,…, U = k · u
u(x) Standard uncertainty of x result
−1
L Limit of detection, the lowest amount of an analyte that is detectable using an instru- μg·l
D
−1
ment, as determined by repeated measurement of a reagent blank
mBq·l
−1
L Limit of quantification, the smallest concentration of an analyte in the test sample μg·l
Q
−1
which can be determined with a fixed precision
mBq·l
−1
s Standard deviation of replicates of the blank Counts·s
No
−1
L Instrumental quantification expressed in counts rate for the chosen mass on charge Counts·s
Qins
ration (m/z), due to the blank and the instrument
-1
L Instrumental limit of detection expressed in counts rate for the chosen mass on charge Counts·s
DI
ration (m/z)
ISO/DIS 20899:2026(en)
V Volume of the sample l
−1
N Number of counts rates for a given mass in the blank solution Counts·s
−1
N Number of gross counts rates: uncorrected counts rate of a measurement Counts·s
−1
N Net number of counts rates N-N Counts·s
net 0
−1
N Net number of counts rates of the internal standard, at the internal standard mass Counts·s
netT
α Measurement bias constant which allows a correction for signal intensity bias between
the tracer and the analyte
M Isotope mass number
ΔM Mass difference M -M
i j
r Measured isotopic ratio
R True isotopic ratio
5 Principle
The principle of measurement of analysis using ICP-MS is described in ISO 17294-1 and ISO 17294-2.
239 240
ICP-MS has been successfully used to measure the mass concentrations of plutonium isotopes ( Pu, Pu,
241 237
Pu) and Np in water samples.
The results can be converted in activity concentrations using the specific activity as a conversion factor
[9] [12] [13] [14]
given in Table 1 [ , , , ].
The typical measurement time is several minutes per sample, including sample uptake, counting time and
washout before the next sample.
[][]
Table 1 — Plutonium and neptunium isotopes half-lives and specific activities
Half-life Specific activity
Plutonium isotope
−1
years Bq·g
239 9 6
Pu 24 100 (±11) 2,296·10 (±2,000·10 )
240 9 6
Pu 6 561 (±7) 8,396·10 (±9,000·10 )
241 12 10
Pu 14,33 (±0,04) 3,829·10 (±1,100·10 )
242 5 8 6
Pu 3,73 (±0,03)·10 1,465·10 (±1,180·10 )
244 6 5 3
Pu 81,1 (±0,6)·10 6,683·10 (±7,600·10 )
Half-life Specific activity
Neptunium
−1
years Bq·g
237 6 7 4
Np 2,144 (±0,007)·10 2,603·10 (±9,000·10 )
The Pu and Np isotopes in the water sample have to be measured after filtration (at 0,45 μm pore size) and
acid preservation if suspended particles are present for the determination of dissolved radionuclides and a
[12]
specific chemical separation shall be performed to limit potential interferences due to uranium isotopes
241 241 [15]
to Am (with Pu) and many potential polyatomic interferences. An example of chemical separation is
given in Annex A.
As described in the ISO 17294 series, a tracer is needed to calculate the chemical recovery and to perform
an isotopic dilution. A known amount of pure certified tracer standard solution is added to the sample test
portion and the calculation of isotope concentration is based on the isotopic ratios.
Activity certified standard solution can be converted into mass certified standard solution thanks to specific
activities in Table 1. External calibration requires more samples preparations and measurements, and more
242 244
complicated calculations. Therefore, if a certified isotope dilution tracer ( Pu or Pu for plutonium
quantification) is available, quantification by isotope dilution is highly preferable.
242 244
For the determination of plutonium isotopes in water, Pu is commonly used but Pu can also be chosen.
...