Nuclear fuel technology - Controlled-potential coulometric assay of plutonium (ISO 12183:2016)

ISO 12183:2016 describes an analytical method for the electrochemical assay of pure plutonium nitrate solutions of nuclear grade, with a total uncertainty not exceeding ±0,2 % at the confidence level of 0,95 for a single determination (coverage factor, K = 2). The method is suitable for aqueous solutions containing more than 0,5 g/L plutonium and test samples containing between 4 mg and 15 mg of plutonium. Application of this technique to solutions containing less than 0,5 g/L and test samples containing less than 4 mg of plutonium requires experimental demonstration by the user that applicable data quality objectives will be met.
For some applications, purification of test samples by anion exchange is required before measurement to remove interfering substances when present in significant amounts.

Kernbrennstofftechnologie - Coulometrische Bestimmung von Plutonium mit kontrolliertem Potential (ISO 12183:2016)

In diesem Dokument wird das Analyseverfahren für die elektrochemische Prüfung von reinen Plutoniumnitrat-Lösungen nuklearer Qualität beschrieben, deren Gesamtunsicherheit ±0,2 % bei einem Vertrauensniveau von 0,95 bei einer Einzelbestimmung (Erweiterungsfaktor, K = 2) nicht übersteigt. Das Verfahren eignet sich für wässrige Lösungen, die mehr als 0,5 g/l Plutonium sowie Prüfproben, die zwischen 4 mg und 15 mg Plutonium enthalten. Die Anwendung dieses Verfahrens für Lösungen, die weniger als 0,5 g/l Plutonium und Prüfproben, die weniger als 4 mg Plutonium enthalten, erfordert einen experimentellen Nachweis durch den Anwender, dass die vorgeschriebenen Datenqualitätsziele erreicht werden.
Bei manchen Anwendungen ist vor der Messung eine Reinigung der Prüfproben durch Anionenaustausch erforderlich, um Störsubstanzen zu entfernen, wenn diese in erheblichen Mengen vorhanden sind. Siehe Abschnitt 10 bezüglich der Erläuterung von Störungen und entsprechende Korrekturmaßnahmen. Eine Reinigung ist auch dann erforderlich, wenn die Reinheit der Prüfprobe unbekannt ist oder wenn sie während des Herstellungsprozesses unvorhersehbar schwankt.
In Abschnitt 11 werden die Änderungen bei der Anwendung der Verfahren sowie die Methoden, die angewendet werden können, und wichtige Überlegungen bei der Auswahl der Messparameter besprochen, die sich jedoch nach wie vor im Anwendungsbereich dieses Dokuments befinden.

Technologie du combustible nucléaire - Dosage du plutonium par coulométrie à potentiel imposé (ISO 12183:2016)

L'ISO 12183:2016 décrit une méthode analytique pour le dosage électrochimique de plutonium pur dans des solutions nitriques de qualité nucléaire, avec une incertitude ne dépassant pas ± 0,2 % dans un intervalle de confiance de 0,95 pour une simple détermination (facteur d'élargissement, K = 2). La méthode est adaptée aux solutions aqueuses contenant plus de 0,5 g/L de plutonium et à des échantillons d'essai contenant entre 4 mg et 15 mg de plutonium. L'application de cette technique aux solutions contenant moins de 0,5 g/L et d'échantillons d'essai contenant moins de 4 mg de plutonium exige que l'utilisateur démontre expérimentalement que les objectifs relatifs à la qualité des données applicables soient atteints.
Pour certaines applications, une purification des échantillons d'essai par échange anionique est nécessaire avant la mesure pour éliminer les substances interférentes présentes en quantités significatives. Se reporter à l'Article 10 qui traite des interférences et des actions correctives. La purification est aussi nécessaire dans les situations où la pureté de l'échantillon d'essai n'est pas connue ou quand elle peut fluctuer de façon imprévisible dans le procédé de fabrication.
L'Article 11 traite des changements dans l'application de la méthode et de la méthodologie qui peuvent être appliquées et des considérations importantes pour sélectionner les paramètres de mesure, tout en restant à l'intérieur du domaine d'application du présent document.

Tehnologija jedrskih goriv - Kulometrična analiza plutonija z nadzorovanim potencialom (ISO 12183:2016)

Standard ISO 12183:2016 opisuje analitično metodo za elektrokemično analizo čistih raztopin plutonijevega nitrata jedrske kakovosti s skupno negotovostjo, ki ne presega ±0,2 % pri stopnji zaupanja 0,95 za eno določanje (faktor pokritja, K = 2). Metoda je primerna za vodne raztopine, ki vsebujejo več kot 0,5 g/l plutonija in testne vzorce, ki vsebujejo med 4 mg in 15 mg plutonija. Uporaba te tehnike pri raztopinah, ki vsebujejo manj kot 0,5 g/l in testnih vzorcih, ki vsebujejo manj kot 4 mg plutonija, od uporabnika zahteva eksperimentalni prikaz, da se zagotovi zahtevana kakovost podatkov.
V nekaterih primerih je pred merjenjem potrebno čiščenje preskusnih vzorcev z izmenjavo anionov, da se odstrani moteče snovi, ko so te prisotne v pomembni količini.

General Information

Status
Published
Public Enquiry End Date
31-Jan-2019
Publication Date
02-Jul-2019
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
20-Jun-2019
Due Date
25-Aug-2019
Completion Date
03-Jul-2019

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SLOVENSKI STANDARD
SIST EN ISO 12183:2019
01-september-2019
Tehnologija jedrskih goriv - Kulometrična analiza plutonija z nadzorovanim
potencialom (ISO 12183:2016)

Nuclear fuel technology - Controlled-potential coulometric assay of plutonium (ISO

12183:2016)
Kernbrennstofftechnologie - Coulometrische Bestimmung von Plutonium mit
kontrolliertem Potential (ISO 12183:2016)

Technologie du combustible nucléaire - Dosage du plutonium par coulométrie à potentiel

imposé (ISO 12183:2016)
Ta slovenski standard je istoveten z: EN ISO 12183:2019
ICS:
27.120.30 Cepljivi materiali in jedrska Fissile materials and nuclear
gorivna tehnologija fuel technology
SIST EN ISO 12183:2019 en,fr,de

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

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SIST EN ISO 12183:2019
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SIST EN ISO 12183:2019
EN ISO 12183
EUROPEAN STANDARD
NORME EUROPÉENNE
June 2019
EUROPÄISCHE NORM
ICS 27.120.30
English Version
Nuclear fuel technology - Controlled-potential coulometric
assay of plutonium (ISO 12183:2016)

Technologie du combustible nucléaire - Dosage du Kernbrennstofftechnologie - Coulometrische

plutonium par coulométrie à potentiel imposé (ISO Bestimmung von Plutonium mit kontrolliertem

12183:2016) Potential (ISO 12183:2016)
This European Standard was approved by CEN on 8 March 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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, 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

© 2019 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 12183:2019 E

worldwide for CEN national Members.
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SIST EN ISO 12183:2019
EN ISO 12183:2019 (E)
Contents Page

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

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SIST EN ISO 12183:2019
EN ISO 12183:2019 (E)
European foreword

The text of ISO 12183:2016 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 12183:2019 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 December 2019, and conflicting national standards

shall be withdrawn at the latest by December 2019.

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, Former Yugoslav Republic of Macedonia,

France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,

Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.
Endorsement notice

The text of ISO 12183:2016 has been approved by CEN as EN ISO 12183:2019 without any modification.

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SIST EN ISO 12183:2019
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SIST EN ISO 12183:2019
INTERNATIONAL ISO
STANDARD 12183
Third edition
2016-08-15
Nuclear fuel technology — Controlled-
potential coulometric assay of
plutonium
Technologie du combustible nucléaire — Dosage du plutonium par
coulométrie à potentiel imposé
Reference number
ISO 12183:2016(E)
ISO 2016
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SIST EN ISO 12183:2019
ISO 12183:2016(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. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2016 – All rights reserved
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SIST EN ISO 12183:2019
ISO 12183:2016(E)
Contents Page

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

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

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

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

4 Principle ........................................................................................................................................................................................................................ 1

5 Reagents ........................................................................................................................................................................................................................ 2

6 Apparatus ..................................................................................................................................................................................................................... 2

7 Procedure..................................................................................................................................................................................................................... 8

7.1 Plutonium determination .............................................................................................................................................................. 8

7.1.1 Weighing the test sample, with an uncertainty of ±0,01 %, K = 1. ........................................ 8

7.1.2 Preparation of the test sample ............................................................................................................................. 9

7.1.3 Electrode pre-treatment............................................................................................................................................ 9

7.1.4 Electrical calibration of the current integration system .............................................................10

7.1.5 Formal potential determination ......................................................................................................................11

7.1.6 Coulometric blank determination..................................................................................................................12

7.1.7 Plutonium measurement .......................................................................................................................................13

7.2 Analysis of subsequent test samples .................................................................................................................................13

8 Expression of results .....................................................................................................................................................................................14

8.1 Calculation of the electrical calibration factor ..........................................................................................................14

8.2 Calculation of the blank ................................................................................................................................................................14

8.3 Fraction of electrolysed plutonium ....................................................................................................................................15

8.4 Plutonium content ............................................................................................................................................................................16

8.5 Quality control ......................................................................................................................................................................................16

9 Characteristics of the method ..............................................................................................................................................................16

9.1 Repeatability ..........................................................................................................................................................................................16

9.2 Confidence interval ..........................................................................................................................................................................17

9.3 Analysis time ..........................................................................................................................................................................................17

10 Interferences .........................................................................................................................................................................................................17

11 Procedure variations and optimization ....................................................................................................................................21

11.1 Accountability measurements and reference material preparation .....................................................21

11.2 Process control measurements..............................................................................................................................................21

11.3 Measurement cell design .............................................................................................................................................................21

11.4 Electrolyte and electrode options ........................................................................................................................................22

11.5 Test sample size ..................................................................................................................................................................................22

11.6 Background current corrections ..........................................................................................................................................22

11.7 Correction for iron ............................................................................................................................................................................23

11.8 Control-potential adjustment ..................................................................................................................................................24

11.9 Calibration methodologies ........................................................................................................................................................24

Annex A (normative) Purification by anion-exchange separation .....................................................................................25

Annex B (normative) Determination of formal potential, E ...................................................................................................27

Bibliography .............................................................................................................................................................................................................................28

© ISO 2016 – All rights reserved iii
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SIST EN ISO 12183:2019
ISO 12183:2016(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 World Trade Organization (WTO) principles in the

Technical Barriers to Trade (TBT) see the following URL: www.iso.org/iso/foreword.html.

The committee responsible for this document is Technical Committee ISO/TC 85, Nuclear energy, nuclear

technologies, and radiological protection, Subcommittee SC 5, Nuclear fuel cycle.

This third edition cancels and replaces the second edition (ISO 12183:2005), which has been technically

revised.
iv © ISO 2016 – All rights reserved
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SIST EN ISO 12183:2019
INTERNATIONAL STANDARD ISO 12183:2016(E)
Nuclear fuel technology — Controlled-potential
coulometric assay of plutonium
1 Scope

This document describes an analytical method for the electrochemical assay of pure plutonium nitrate

solutions of nuclear grade, with a total uncertainty not exceeding ±0,2 % at the confidence level of

0,95 for a single determination (coverage factor, K = 2). The method is suitable for aqueous solutions

containing more than 0,5 g/L plutonium and test samples containing between 4 mg and 15 mg of

plutonium. Application of this technique to solutions containing less than 0,5 g/L and test samples

containing less than 4 mg of plutonium requires experimental demonstration by the user that applicable

data quality objectives will be met.

For some applications, purification of test samples by anion exchange is required before measurement to

remove interfering substances when present in significant amounts. Refer to Clause 10 for a discussion

of interferences and corrective actions. Purification is also appropriate in situations where the purity

of the test sample is unknown or when it may fluctuate unpredictably in a manufacturing process.

Clause 11 discusses the changes in application of the method and methodology that can be applied and

important considerations when selecting measurement parameters, while still remaining within the

intended scope of this document.
2 Normative references
There are no normative references in this document.
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:

— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp
4 Principle
The key steps and their purposes are outlined below:

— test samples are prepared by weighing and then fuming to dryness with sulphuric acid to achieve a

consistent and stable anhydrous plutonium sulphate salt that is free from chloride, fluoride, nitrate,

nitrite, hydroxylamine, and volatile organic compounds;

— if needed to remove interferences, dissolve test samples and purify by anion exchange, then fume

the eluted plutonium solution in the presence of sulphuric acid to obtain the dry plutonium sulphate

chemical form;

— measure a blank of the nitric acid supporting electrolyte and calculate the background current

correction applicable to the electrolysis of the test sample from charging, faradaic, and residual

[1]
current ;

— dissolve the dried test sample in the previously measured supporting electrolyte (the blank);

© ISO 2016 – All rights reserved 1
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SIST EN ISO 12183:2019
ISO 12183:2016(E)

— reduce the test sample at a controlled potential that electrolyses the plutonium to greater than

99,8 % Pu and measure the equilibrium solution potential at the end of this step by control-

[2]
potential adjustment ;

— oxidize the test sample at a controlled potential that electrolyses the plutonium to greater than

99,8 % Pu and measure the equilibrium solution potential at the end of this electrolysis by control-

potential adjustment;

— correct the result for the background current and the fraction of plutonium not electrolysed;

— calibrate the coulometer using traceable electrical standards and Ohm’s Law;

— use the measured value of the coulometer calibration factor and the Faraday constant to convert the

coulombs of integrated current from the electrolyses to moles of plutonium;

— use traceable quality-control plutonium standards to demonstrate independently the performance

of the measurement system;

— periodically measure the formal potential of the plutonium couple, E which is user-specific based

on the cell design, connections, reference electrode type, and the acid-type and molarity of the

supporting electrolyte.

These steps ensure that representative, reproducible, and stable test samples are prepared for

measurement. The test samples are measured using a protocol that is based upon first principles and is

consistent with a traceable, electrical calibration of the coulometer. Additional details are provided in

Clauses 10 and 11.
5 Reagents
Use only analytical grade reagents.

All aqueous solutions shall be prepared with double-distilled or distilled, demineralized water with a

resistivity greater than 10 MΩ⋅cm, i.e. ISO 3696 Grade 1 purified water.
5.1 Nitric acid solution, c (HNO ) = 0,9 mol/L.
NOTE Refer to 11.4 for other electrolyte options.
5.2 Amidosulphuric acid solution, c (NH HSO ) = 1,5 mol/L.
2 3
5.3 Sulphuric acid solution, c (H SO ) = 3 mol/L.
2 4

NOTE Molarity is not a critical parameter for sulphuric acid used to fume plutonium test samples, provided

the concentration of the reagent is well above the level where colloidal plutonium complexes form.

5.4 Pure argon or nitrogen, (O content lower than 10 ppm).
5.5 Pure air, free of organic contaminants.
6 Apparatus

Usual laboratory equipment found in a medium-activity radiochemical laboratory suitable for work

with plutonium shall be used.

6.1 Analytical balance, installed in radiological containment unit and must be capable of weighing

1 g mass, with an uncertainty of ±0,1 mg (coverage factor, K = 1). This represents a relative uncertainty

of 0,01 %.
2 © ISO 2016 – All rights reserved
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SIST EN ISO 12183:2019
ISO 12183:2016(E)

— Weighing less than 1 g will increase the relative uncertainty to >0,01 %, in an inversely

proportional manner.

— If the uncertainty of the balance, as installed, does not meet the ±0,01 mg criterion, then

correspondingly larger test samples are required.

6.2 Weighing burette, glass or plastic, the material selection is not critical provided it maintains a

stable mass (tare weight) and static charge is controlled as described in 7.1.1.

6.3 Equipment for test sample evaporation in the coulometric cell, comprising of an overhead

radiant heater or hot-plate with controls to adjust temperature. Design requirements and optional

features for effective evaporation and fuming include:

— providing settings that allow both rapid and well-controlled rate of initial evaporation, followed by

fuming the remaining sulphuric acid solution to dryness at a higher temperature;

— preventing mechanical loss of the test sample solution from boiling and/or spattering;

— preventing contamination by extraneous chemicals, such as those which may be used to neutralize

acid vapours;

— heating of the coulometer cell wall to optimize fuming and minimize refluxing of sulphuric acid by

placing the cell inside an optional aluminium tube with an inner diameter that is 1 mm to 3 mm

larger than the outer diameter of the cell and a height that is 1 mm to 5 mm shorter than the cell may

be placed around the cell during the fuming step to heat the walls of the cell;

NOTE An aluminium block with holes bored to a similar specification for inserting the cell may be used

instead of the aluminium tubes.

— addition of an optional air supply with the delivery tube directed towards the surface of the liquid

to optimize the evaporation rate and disperse the acid fumes;

— addition of an optional vapour capture and local neutralization to control acid fumes, depending

upon facility design and ventilation system requirements.
See Figure 1.
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SIST EN ISO 12183:2019
ISO 12183:2016(E)
Dimensions in centimetres
Figure 1 — Sample evaporation system
6.4 Controlled-potential coulometer.
See Figure 2.
6.4.1 Coulometer cell assembly, comprising the following:
— a stirrer motor with a rotation frequency of at least 1 000 min ;

NOTE 1 Adjustable-speed motors allow optimizing rotation rates for individual cell designs. Stirrer

motors powered by isolated DC power supplies are desirable to prevent electrical noise from being

superimposed on the blank and test sample electrolysis current signals sent to the integrator.

— a cylindrical or tapered glass coulometric cell of capacity 50 mL, or less, with an O-ring seal and a

tight-fitting lid with openings to insert the following internal equipment:

— an inlet tube for humidified, inert gas to displace dissolved and atmospheric oxygen from the

solution and the electrolysis cell, respectively;

— a stirrer with blade and shaft made from chemically inert materials [e.g. polytetrafluoroethylene

(PTFE)], and designed to prevent splashing; the shaft of the stirrer is typically located in the

centre of the cell and connected directly to the stirrer motor;

— a working electrode made of gold (e.g. 99,99 %) and consisting of a gold wire welded or machined

to a cylindrical gold wire frame, nominally 15 mm high and 20 mm in diameter, around which

is welded or machined a very fine gold mesh, which is typically several layers (e.g. four layers);

NOTE 2 Refer to 11.4 for other working electrode options.

— a glass tube plugged at the bottom end with a sintered-glass disc (typical dimensions of 2,5-mm

thick and pore size <0,01 μm), the tube filled with nitric acid (5.1) and the tip of the sintered-glass

end positioned within the ring of the working electrode;

— a reference electrode, saturated calomel electrode (SCE), or other reference electrodes as described

in 11.3, is inserted into the glass tube;
4 © ISO 2016 – All rights reserved
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ISO 12183:2016(E)

— another glass tube, similar to the first one, also filled with nitric acid (5.1), and the tip of the sintered-

glass end positioned within the ring of the working electrode;

— an auxiliary electrode consisting of a platinum wire, 0,5 mm to 3,0 mm in diameter, is inserted into

the second glass tube;

NOTE 3 The platinum wire may be coiled to increase the surface area submerged in the supporting

electrolyte, as illustrated in Figure 2.

— a gas washer bottle, filled with reagent water as described in Clause 5, to humidify the inert gas

before it is introduced into the coulometer cell assembly.

The diameter of the glass tube and sintered-glass disc containing the auxiliary electrode may be larger

than that of the glass tube and sintered-glass disc containing the reference electrode. The flow rate of

the solution through both glass discs shall be less than 0,05 mL/h.

a) A thermocouple or resistance thermometer installed in the coulometer cell assembly for measuring

the temperature of the test sample solution during the measurement process is an optional feature.

The solution temperature should be measured either during the oxidation of the test sample or

immediately following the analysis. An uncertainty goal for the temperature measurement is

±0,2 °C (K = 1).

— If it is not possible to insert a temperature sensor into the electrolysis cell or not desirable

to measure the temperature of the test sample solution immediately after the electrolysis is

completed, then estimate the solution temperature from the ambient air temperature or the

reagent temperature. Note that the purge gas is cooled by expansion causing the solution

temperature to decrease relative to the ambient temperature; the extent of this decrease is a

function of the inert-gas flow rate and the cell design. The measured air or reagent temperature

value must be corrected for this cooling effect. A higher uncertainty of ±1 °C, K = 1, is expected

in the calculated solution temperature.

b) For optimum potential control, position the sintered-glass discs of the reference and auxiliary

electrodes glass tubes to meet the following requirements:

— the closest distance from the reference electrode sintered-glass disc to the working electrode is

2 mm or less;

— the distance between the two sintered-glass discs containing the auxiliary and reference

electrodes is less than the distance between the auxiliary electrode disc and the nearest point

on the working electrode.

c) The hole through which the stirrer shaft is inserted serves as the primary escape vent for the

inert gas. Except for this hole, all other insertions are tight fitting. The inert-gas flow rate must

be sufficiently high to quickly remove oxygen from the supporting electrolyte and the test sample

solution. Furthermore, it must prevent leakage of air into the cell assembly during the electrolysis.

A practical guide for adjusting the flow rate is to direct all or part of the inert gas supply toward

the solution, such that a 2 mm to 4 mm dimple is formed on the surface without causing the

solution to splash.

— Cell assemblies with an optimized design, an adequate inert-gas flow rate, and a tight fit, will

remove oxygen in 5 min or less. The time required to remove oxygen from the solution should

be established by users based on testing of their cell assembly under routine conditions.

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SIST EN ISO 12183:2019
ISO 12183:2016(E)
Key
1 video 8 auxiliary (or counter) electrode in bridge tube filled with
supporting electrolyte
2 printer (optional)
3 control computer 9 reference electrode in bridge tube filled with supporting
electrolyte
4 keyboard 10 inert gas
5 potentiostat and integrator 11 stirrer
6 digital voltmeter (DVM) 12 working electrode
7 AC/DC power for stirring motor 13 cell
Figure 2 — Coulometric cell assembly connections
[3][4]
6.4.2 Instrumentation, comprising the following :
a) Potentiostat with the desired range of electrolysis potentials for plutoniu
...

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