SIST EN ISO 9463:2021

Nuclear energy - Nuclear fuel technology - Determination of plutonium in nitric acid solutions by spectrophotometry (ISO 9463:2019)

This document specifies an analytical method by spectrophotometry, for determining the plutonium concentration in nitric acid solutions, with spectrophotometer implemented in hot cell and glove box allowing the analysis of high activity solutions. Commonly, the method is applicable, without interference, even in the presence of numerous cations, for a plutonium concentration higher than 0,5 mg·l−1 in the original sample with a standard uncertainty, with coverage factor k = 1, less than 5 %.
The method is intended for process controls at the different steps of the process in a nuclear fuel reprocessing plant or in other nuclear facilities.

Kernenergie - Kernbrennstofftechnologie - Spektrophotometrische Plutoniumbestimmung in Salpetersäurelösungen (ISO 9463:2019)

Énergie nucléaire - Technologie du combustible nucléaire - Détermination du plutonium dans les solutions d'acide nitrique par spectrophotométrie (ISO 9463:2019)

Le présent document spécifie une méthode d'analyse par spectrophotométrie, destinée à déterminer la concentration en plutonium dans des solutions d'acide nitrique, le spectrophotomètre étant mis en œuvre dans des chaînes blindées et des boîtes à gants permettant l'analyse de solutions de hautes activités. La méthode est habituellement applicable, sans interférence, même en présence de nombreux cations, pour une concentration en plutonium supérieure à 0,5 mg·l−1 dans l'échantillon d'origine avec une incertitude, avec un facteur d'élargissement k = 1, de moins de 5 %.
La méthode est destinée aux contrôles à différents stades du processus dans une usine de retraitement de combustible nucléaire ou dans d'autres installations nucléaires.

Jedrska energija - Tehnologija jedrskih goriv - Določevanje plutonija v raztopinah dušikove kisline s spektrofotometrijo (ISO 9463:2019)

General Information

• Status: Published
• Public Enquiry End Date: 30-Nov-2020
• Publication Date: 21-Feb-2021
• ICS: 27.120.30 - Fissile materials and nuclear fuel technology
• Technical Committee: I13 - Imaginarni 13
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 18-Feb-2021
• Due Date: 25-Apr-2021
• Completion Date: 22-Feb-2021
• Ref Project: EN ISO 9463:2021 - Nuclear energy - Nuclear fuel technology - Determination of plutonium in nitric acid solutions by spectrophotometry (ISO 9463:2019)

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN ISO 9463:2021
01-april-2021
Jedrska energija - Tehnologija jedrskih goriv - Določevanje plutonija v raztopinah
dušikove kisline s spektrofotometrijo (ISO 9463:2019)
Nuclear energy - Nuclear fuel technology - Determination of plutonium in nitric acid
solutions by spectrophotometry (ISO 9463:2019)
Énergie nucléaire - Technologie du combustible nucléaire - Détermination du plutonium
dans les solutions d'acide nitrique par spectrophotométrie (ISO 9463:2019)
Ta slovenski standard je istoveten z: EN ISO 9463:2021
ICS:
27.120.30 Cepljivi materiali in jedrska Fissile materials and nuclear
gorivna tehnologija fuel technology
SIST EN ISO 9463:2021 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 9463:2021

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SIST EN ISO 9463:2021


EN ISO 9463
EUROPEAN STANDARD

NORME EUROPÉENNE

February 2021
EUROPÄISCHE NORM
ICS 27.120.30
English Version

Nuclear energy - Nuclear fuel technology - Determination
of plutonium in nitric acid solutions by spectrophotometry
(ISO 9463:2019)
Énergie nucléaire - Technologie du combustible
nucléaire - Détermination du plutonium dans les
solutions d'acide nitrique par spectrophotométrie (ISO
9463:2019)
This European Standard was approved by CEN on 18 January 2021.

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
© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 9463:2021 E
worldwide for CEN national Members.

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SIST EN ISO 9463:2021
EN ISO 9463:2021 (E)
Contents Page
European foreword . 3

2

---------------------- Page: 4 ----------------------
SIST EN ISO 9463:2021
EN ISO 9463:2021 (E)
European foreword
The text of ISO 9463:2019 has been prepared by Technical Committee ISO/TC 85 "Nuclear energy,
nuclear technologies, and radiological protection” of the International Organization for Standardization
(ISO) and has been taken over as EN ISO 9463:2021 by Technical Committee CEN/TC 430 “Nuclear
energy, nuclear technologies, and radiological protection” the secretariat of which is held by AFNOR.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by August 2021, and conflicting national standards shall
be withdrawn at the latest by August 2021.
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 9463:2019 has been approved by CEN as EN ISO 9463:2021 without any modification.

3

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SIST EN ISO 9463:2021

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SIST EN ISO 9463:2021
INTERNATIONAL ISO
STANDARD 9463
Third edition
2019-01
Nuclear energy — Nuclear fuel
technology — Determination of
plutonium in nitric acid solutions by
spectrophotometry
Énergie nucléaire — Technologie du combustible nucléaire —
Détermination du plutonium dans les solutions d'acide nitrique par
spectrophotométrie
Reference number
ISO 9463:2019(E)
©
ISO 2019

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SIST EN ISO 9463:2021
ISO 9463:2019(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2019
All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Fax: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved

---------------------- Page: 8 ----------------------
SIST EN ISO 9463:2021
ISO 9463:2019(E)

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Chemical conditions . 1
5.1 Stability of Pu(VI) . 1
5.2 Rate of oxidation of Pu(IV) to Pu(VI) . 2
5.3 Destruction of the excess oxidant . 2
5.4 Comparison of Ce(IV) and Ag(II) . 2
5.5 Molar extinction coefficient of Pu(VI) . 2
6 Reagents . 3
6.1 General . 3
6.2 Common reagents for methods using silver oxide or cerium as oxidant . 3
6.3 Reagents for method using silver oxide as oxidant . 3
6.4 Reagents for method using Ce(IV) as oxidant . 3
7 Apparatus . 4
8 Test procedure . 4
8.1 Preparation of the different solutions. 4
8.1.1 Plutonium calibration solution . 4
8.1.2 Sample solutions . 5
8.2 Spectrophotometer setup . 6
8.3 Measurements . 6
8.3.1 Background measurement . 6
8.3.2 Measurements on the calibration solution . 7
8.3.3 Measurements on the sample solution . 7
9 Expression of the result. 7
9.1 Calculation of the concentration of plutonium in the sample . 7
9.2 Reproducibility . 8
9.3 Detection limit . 8
10 Interferences . 8
10.1 Anions . 8
10.2 Cations . 9
Annex A (informative) Preparation of silver (II) oxide (AgO) .11
Bibliography .12
© ISO 2019 – All rights reserved iii

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SIST EN ISO 9463:2021
ISO 9463:2019(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 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 85, Nuclear energy, nuclear technologies,
and radiological protection, Subcommittee SC 5, Nuclear installations, processes and technologies.
This third edition cancels and replaces the second edition (ISO 9463:2009), which has been technically
revised. The main change compared to the previous edition is the use of silver (II) oxide powder for the
plutonium valence adjustment.
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 2019 – All rights reserved

---------------------- Page: 10 ----------------------
SIST EN ISO 9463:2021
INTERNATIONAL STANDARD ISO 9463:2019(E)
Nuclear energy — Nuclear fuel technology —
Determination of plutonium in nitric acid solutions by
spectrophotometry
1 Scope
This document specifies an analytical method by spectrophotometry, for determining the plutonium
concentration in nitric acid solutions, with spectrophotometer implemented in hot cell and glove
box allowing the analysis of high activity solutions. Commonly, the method is applicable, without
interference, even in the presence of numerous cations, for a plutonium concentration higher than
−1
0,5 mg·l in the original sample with a standard uncertainty, with coverage factor k = 1, less than 5 %.
The method is intended for process controls at the different steps of the process in a nuclear fuel
reprocessing plant or in other nuclear facilities.
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 1042, Laboratory glassware — One-mark volumetric flasks
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
4 Principle
Plutonium is quantitatively oxidized to the hexavalent state either with cerium (IV) or with silver
oxide. The excess of silver oxide is destroyed by the addition of sulfamic acid. The optical density
2+
of the plutonium (VI) (PuO ) absorption peak at the wavelength of 831 nm is then measured on a
2
spectrophotometer. The result is obtained by comparison to a calibration performed under similar
conditions (with the same nitrate content).
5 Chemical conditions
5.1 Stability of Pu(VI)
Pu(VI) is very stable under the operating conditions of the method over the range
−1 + −1
2 mol·l < c(H ) < 5 mol·l .
© ISO 2019 – All rights reserved 1

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SIST EN ISO 9463:2021
ISO 9463:2019(E)

5.2 Rate of oxidation of Pu(IV) to Pu(VI)
The rate of oxidation by Ce(IV) decreases as the acidity increases. With the reagent quantities stated in
−1 −1
the method, the oxidation is complete in 2 min or more in 2 mol·l or 3 mol·l nitric acid.
−1
As an example, the oxidation of Pu(IV) in 4 mol·l nitric acid is complete in between 10 min and 15 min
[2]
when the Ce/Pu initial ratio is higher than 20 .
With silver oxide, the oxidation is very fast, much faster than with Ce(IV).
2+ + 4+ 3+
In addition, the Ag /Ag redox potential is higher than that of Ce /Ce and is better adapted to cope
with the presence of organic traces in solution.
On the other hand, cerium presents the advantage to be stable in sulfuric acid so that it can be added as
a precise quantity in solution.
5.3 Destruction of the excess oxidant
With cerium the excess reagent and product Ce(III), does not interfere (no absorption above 450 nm)
[2]
and does not need to be destroyed .
With silver oxide as oxidant, the excess reagent shall be destroyed by reaction with a small excess of
[2]
sulfamic acid or rise of temperature .
5.4 Comparison of Ce(IV) and Ag(II)
As regards Pu(IV) oxidation into Pu(VI), the reactivity and use of Ce(IV) and Ag(II) are compared in
Table 1, in order to guide the analyst in the selection of the best reactant for oxidation.
Table 1 — Comparison of Ce(IV) and Ag(II)
Oxidizer Ag(II) Ce(IV)
Introduction of reactants − +
Spectral interferences − +
Oxidizing power ++ +
Oxidation kinetics ++ −
Oxidizer excess destruction Sulfamic acid or rise of temperature Not necessary
Operating temperature Room temperature
5.5 Molar extinction coefficient of Pu(VI)
1)
The nominal molar extinction coefficient i.e. the molar attenuation coefficient of Pu(VI) in nitric acid
−1 −1 −1 −1[3]
solution varies between 400 l·mol ·cm and 500 l·mol ·cm , with a very narrow full width at half
maximum (FWHM) of about 4 nm.
The molar extinction coefficient and therefore absorbance depends upon a number of parameters, for
example:
— The nitrate ion concentration. The decrease in molar extinction coefficient becomes more
−1 −1
pronounced at higher nitrate levels. At about 3 mol·l nitrate, an increase of 0,1 mol·l in the total
nitrate content causes a decrease of about 0,7 % in the molar extinction coefficient.
−1
— The acidity. This change is generally less than 0,1 % for a free acid change of 0,1 mol·l . Thus the
influence of free acidity is an order of magnitude less than that of the nitrate content.
1) The molar extinction coefficient is the absorbance of light by a chemical species at a given wavelength and for
a 1 cm light path. It is an intrinsic property of the species. The SI unit of molar attenuation coefficient is the square
2 −1 −1 −2 −1 −1
metre per mole (m ·mol ), but in practice, it is usually taken as the mol ⋅cm or the l.mol ⋅cm .
2 © ISO 2019 – All rights reserved

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SIST EN ISO 9463:2021
ISO 9463:2019(E)

— The temperature. The decrease in molar extinction coefficient is about 0,5 % per degree Celsius.
6 Reagents
6.1 General
All reagents shall be of analytical grade.
This procedure requires that measurements are made in nitric acid medium as this permits either
Ce(IV) or silver oxide to be used as oxidant and is convenient for most applications. Commonly the
−1
sample is diluted into
...

SLOVENSKI STANDARD
oSIST prEN ISO 9463:2020
01-november-2020
Jedrska energija - Tehnologija jedrskih goriv - Določevanje plutonija v raztopinah
dušikove kisline s spektrofotometrijo (ISO 9463:2019)
Nuclear energy - Nuclear fuel technology - Determination of plutonium in nitric acid
solutions by spectrophotometry (ISO 9463:2019)
Énergie nucléaire - Technologie du combustible nucléaire - Détermination du plutonium
dans les solutions d'acide nitrique par spectrophotométrie (ISO 9463:2019)
Ta slovenski standard je istoveten z: prEN ISO 9463
ICS:
27.120.30 Cepljivi materiali in jedrska Fissile materials and nuclear
gorivna tehnologija fuel technology
oSIST prEN ISO 9463:2020 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
oSIST prEN ISO 9463:2020

---------------------- Page: 2 ----------------------
oSIST prEN ISO 9463:2020
INTERNATIONAL ISO
STANDARD 9463
Third edition
2019-01
Nuclear energy — Nuclear fuel
technology — Determination of
plutonium in nitric acid solutions by
spectrophotometry
Énergie nucléaire — Technologie du combustible nucléaire —
Détermination du plutonium dans les solutions d'acide nitrique par
spectrophotométrie
Reference number
ISO 9463:2019(E)
©
ISO 2019

---------------------- Page: 3 ----------------------
oSIST prEN ISO 9463:2020
ISO 9463:2019(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2019
All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Fax: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved

---------------------- Page: 4 ----------------------
oSIST prEN ISO 9463:2020
ISO 9463:2019(E)

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Chemical conditions . 1
5.1 Stability of Pu(VI) . 1
5.2 Rate of oxidation of Pu(IV) to Pu(VI) . 2
5.3 Destruction of the excess oxidant . 2
5.4 Comparison of Ce(IV) and Ag(II) . 2
5.5 Molar extinction coefficient of Pu(VI) . 2
6 Reagents . 3
6.1 General . 3
6.2 Common reagents for methods using silver oxide or cerium as oxidant . 3
6.3 Reagents for method using silver oxide as oxidant . 3
6.4 Reagents for method using Ce(IV) as oxidant . 3
7 Apparatus . 4
8 Test procedure . 4
8.1 Preparation of the different solutions. 4
8.1.1 Plutonium calibration solution . 4
8.1.2 Sample solutions . 5
8.2 Spectrophotometer setup . 6
8.3 Measurements . 6
8.3.1 Background measurement . 6
8.3.2 Measurements on the calibration solution . 7
8.3.3 Measurements on the sample solution . 7
9 Expression of the result. 7
9.1 Calculation of the concentration of plutonium in the sample . 7
9.2 Reproducibility . 8
9.3 Detection limit . 8
10 Interferences . 8
10.1 Anions . 8
10.2 Cations . 9
Annex A (informative) Preparation of silver (II) oxide (AgO) .11
Bibliography .12
© ISO 2019 – All rights reserved iii

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oSIST prEN ISO 9463:2020
ISO 9463:2019(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 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 85, Nuclear energy, nuclear technologies,
and radiological protection, Subcommittee SC 5, Nuclear installations, processes and technologies.
This third edition cancels and replaces the second edition (ISO 9463:2009), which has been technically
revised. The main change compared to the previous edition is the use of silver (II) oxide powder for the
plutonium valence adjustment.
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 2019 – All rights reserved

---------------------- Page: 6 ----------------------
oSIST prEN ISO 9463:2020
INTERNATIONAL STANDARD ISO 9463:2019(E)
Nuclear energy — Nuclear fuel technology —
Determination of plutonium in nitric acid solutions by
spectrophotometry
1 Scope
This document specifies an analytical method by spectrophotometry, for determining the plutonium
concentration in nitric acid solutions, with spectrophotometer implemented in hot cell and glove
box allowing the analysis of high activity solutions. Commonly, the method is applicable, without
interference, even in the presence of numerous cations, for a plutonium concentration higher than
−1
0,5 mg·l in the original sample with a standard uncertainty, with coverage factor k = 1, less than 5 %.
The method is intended for process controls at the different steps of the process in a nuclear fuel
reprocessing plant or in other nuclear facilities.
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 1042, Laboratory glassware — One-mark volumetric flasks
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
4 Principle
Plutonium is quantitatively oxidized to the hexavalent state either with cerium (IV) or with silver
oxide. The excess of silver oxide is destroyed by the addition of sulfamic acid. The optical density
2+
of the plutonium (VI) (PuO ) absorption peak at the wavelength of 831 nm is then measured on a
2
spectrophotometer. The result is obtained by comparison to a calibration performed under similar
conditions (with the same nitrate content).
5 Chemical conditions
5.1 Stability of Pu(VI)
Pu(VI) is very stable under the operating conditions of the method over the range
−1 + −1
2 mol·l < c(H ) < 5 mol·l .
© ISO 2019 – All rights reserved 1

---------------------- Page: 7 ----------------------
oSIST prEN ISO 9463:2020
ISO 9463:2019(E)

5.2 Rate of oxidation of Pu(IV) to Pu(VI)
The rate of oxidation by Ce(IV) decreases as the acidity increases. With the reagent quantities stated in
−1 −1
the method, the oxidation is complete in 2 min or more in 2 mol·l or 3 mol·l nitric acid.
−1
As an example, the oxidation of Pu(IV) in 4 mol·l nitric acid is complete in between 10 min and 15 min
[2]
when the Ce/Pu initial ratio is higher than 20 .
With silver oxide, the oxidation is very fast, much faster than with Ce(IV).
2+ + 4+ 3+
In addition, the Ag /Ag redox potential is higher than that of Ce /Ce and is better adapted to cope
with the presence of organic traces in solution.
On the other hand, cerium presents the advantage to be stable in sulfuric acid so that it can be added as
a precise quantity in solution.
5.3 Destruction of the excess oxidant
With cerium the excess reagent and product Ce(III), does not interfere (no absorption above 450 nm)
[2]
and does not need to be destroyed .
With silver oxide as oxidant, the excess reagent shall be destroyed by reaction with a small excess of
[2]
sulfamic acid or rise of temperature .
5.4 Comparison of Ce(IV) and Ag(II)
As regards Pu(IV) oxidation into Pu(VI), the reactivity and use of Ce(IV) and Ag(II) are compared in
Table 1, in order to guide the analyst in the selection of the best reactant for oxidation.
Table 1 — Comparison of Ce(IV) and Ag(II)
Oxidizer Ag(II) Ce(IV)
Introduction of reactants − +
Spectral interferences − +
Oxidizing power ++ +
Oxidation kinetics ++ −
Oxidizer excess destruction Sulfamic acid or rise of temperature Not necessary
Operating temperature Room temperature
5.5 Molar extinction coefficient of Pu(VI)
1)
The nominal molar extinction coefficient i.e. the molar attenuation coefficient of Pu(VI) in nitric acid
−1 −1 −1 −1[3]
solution varies between 400 l·mol ·cm and 500 l·mol ·cm , with a very narrow full width at half
maximum (FWHM) of about 4 nm.
The molar extinction coefficient and therefore absorbance depends upon a number of parameters, for
example:
— The nitrate ion concentration. The decrease in molar extinction coefficient becomes more
−1 −1
pronounced at higher nitrate levels. At about 3 mol·l nitrate, an increase of 0,1 mol·l in the total
nitrate content causes a decrease of about 0,7 % in the molar extinction coefficient.
−1
— The acidity. This change is generally less than 0,1 % for a free acid change of 0,1 mol·l . Thus the
influence of free acidity is an order of magnitude less than that of the nitrate content.
1) The molar extinction coefficient is the absorbance of light by a chemical species at a given wavelength and for
a 1 cm light path. It is an intrinsic property of the species. The SI unit of molar attenuation coefficient is the square
2 −1 −1 −2 −1 −1
metre per mole (m ·mol ), but in practice, it is usually taken as the mol ⋅cm or the l.mol ⋅cm .
2 © ISO 2019 – All rights reserved

---------------------- Page: 8 ----------------------
oSIST prEN ISO 9463:2020
ISO 9463:2019(E)

— The temperature. The decrease in molar extinction coefficient is about 0,5 % per degree Celsius.
6 Reagents
6.1 General
All reagents shall be of analytical grade.
This procedure requires that measurements are made in nitric acid medium as this permits either
Ce(IV) or silver oxide to be used as oxidant and is convenient for most applications. Commonly the
−1
sample is diluted into 3 mol·l nitric acid. It is acceptable to use Ce(IV) as oxidant at low acidities
and silver oxide as oxidant at high acidities provided that the concentration of the nitric acid used for
calibration is similarly adjusted.
6.2 Common reagents for methods using silver oxide or cerium as oxidant
−1
6.2.1 Nitric acid, c(HNO ) = (3 ± 0,05) mol·l . It can be prepared by dilution of concentrated nitric
3
acid in water (6.2.2).
6.2.2 Water, complying with grade 3 of ISO 3696.
6.2.3 Reference solution, plutonium in solution in nitric acid with a nitrate concentration close
to that of the sample to analyse.
−1
The recommended minimum plutonium concentration is 5 mg·l . For instance the plutonium
−1
concentration can be about 20 mg·l .
The plutonium reference solution used for the analysis can be prepared by dilution of a concentrated
reference mother plutonium solution.
6.3 Reagents for method using silver oxide as oxidant
−1
6.3.1 Sulfamic acid c(NH SO H) = 0,5 mol·l solution in water.
2 3
It can be prepared by dissolution of 48,5 g NH SO H in 1 l of water:
2 3
— in a beaker, weigh 48,5 g of NH SO H;
2 3
— add 800 ml of water (6.2.2);
— homogenize;
— transfer the solution into a 1 l volumetric flask;
— adjust the volume with water (6.2.2).
6.3.2 Silver (II) oxide (AgO) powder, fine black powder commercially available.
The protocol to prepare AgO, if AgO powder is not available, is given in Annex A.
6.4 Reagents for method using Ce(IV) as oxidant
-1
6.4.1 Nitric acid, c(HNO ) = 1 mol·l .
3
6.4.2 Ceric ammonium nitrate, (NH ) Ce(NO ) , orange-red, water-soluble cerium salt.
4 2 3 6
© ISO 2019 – All rights reserved 3

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oSIST prEN ISO 9463:2020
ISO 9463:2019(E)

4+ −1
6.4.3 Ce(IV), c(Ce ) = 0,4 mol·l .
This reagent can be prepared in a number of ways. One procedure can be as follows.
−1
Dissolve 219,3 g of ceric ammonium nitrate [(NH ) Ce(NO ) ] (6.4.2) in 600 ml of 1 mol·l nitric acid
4 2 3 6
(6.4.1)
...