ISO/FDIS 12800

• Abstract:

  ISO 12800:2017 gives guidelines on the determination of the specific surface area of as-fabricated uranium dioxide powder by volumetric or gravimetric determination of the amount of nitrogen adsorbed on the powder, and can be applied to other similar materials, e.g. U3O8, UO2-PuO2 powders, and other bodies with similar surface areas, e.g. powder granules or green pellets, provided that the conditions described are fulfilled. Modifications using other adsorbing gases are included. The method is relevant as long as the expected value is in the range between 1 m2/g and 10 m2/g.

• Status: Not Published
• ICS: 27.120.30 - Fissile materials and nuclear fuel technology
• Technical Committee: ISO/TC 85/SC 5 - Nuclear installations, processes and technologies
• Drafting Committee: ISO/TC 85/SC 5/WG 1 - Analytical methodology in the nuclear fuel cycle
• Current Stage: 5020 - FDIS ballot initiated: 2 months. Proof sent to secretariat
• Start Date: 16-Sep-2026
• Completion Date: 16-Sep-2026

• Consolidates: FprEN ISO 12800 - Nuclear fuel technology - Guidelines on the measurement of the specific surface area of uranium dioxide and plutonium dioxide powders by the BET method (ISO/FDIS 12800:2026)
• Effective Date: 12-Feb-2026
• Revises: ISO 12800:2017 - Nuclear fuel technology — Guidelines on the measurement of the specific surface area of uranium oxide powders by the BET method
• Effective Date: 18-Jan-2025

ISO/FDIS 12800 is an ISO document for nuclear fuel technology. It gives guidelines for measuring the specific surface area of uranium dioxide and plutonium dioxide powders by the Brunauer-Emmett-Teller (BET) method, using nitrogen adsorption and related variants. It is written for nuclear fuel fabrication work where the expected surface area falls in the ranges covered by the document.

What does ISO/FDIS 12800 specify?

ISO/FDIS 12800 specifies how to determine the specific surface area of as-fabricated UO2 and PuO2 powders by volumetric or gravimetric measurement of adsorbed gas. It also extends to similar materials and to modified methods using other adsorbing gases when the stated conditions are met.

The document is organized into:

• Scope
• Normative references
• Terms and definitions
• Principle
• Procedure
• Expression of results
• Test report

Clause 1 limits the method to nuclear fuel fabrication and gives the expected measurement ranges for UO2 and PuO2. Clause 5 then covers sample preparation and the different measurement routes, while Clauses 6 and 7 cover calculation, uncertainty-related reporting, and the test report content.

What are the key requirements of ISO/FDIS 12800?

ISO/FDIS 12800 is built around the BET method, but it only applies when the material and isotherm behavior match the method assumptions. In practice, the operator has to choose a suitable pretreatment, measurement path, and calculation method, then document them clearly.

Applicability and measurement limits

Clause 1 states that the method is intended for UO2 and PuO2 powders, and it can also be applied to U3O8, UO2-PuO2 powders, powder granules, or green pellets when the described conditions are satisfied. The document also gives expected value ranges for UO2 and PuO2, which matters because the chosen sample mass and instrument sensitivity depend on the surface area level.

BET principle and isotherm type

Clause 4 explains that the BET method uses the amount of gas needed to form a monomolecular layer, derived from an isothermal adsorption curve at liquid-nitrogen temperature. The method applies only to type 2 or type 4 adsorption curves, so users need to confirm that the sample behavior fits the BET model before relying on the result.

Sample preparation

Clause 5.1 requires removal of surface contamination such as water vapor before measurement. For UO2 powders, the document gives example degassing conditions and warns against heating that could cause sintering or other surface changes; for PuO2 powders, it notes the need for stronger desorption conditions because of stronger adsorption.

Measurement routes

Clause 5 describes volumetric measurement, gravimetric measurement, a dynamic carrier-gas method, and alternative methods. The volumetric route uses a calibrated bulb and pressure change, while the gravimetric route measures adsorbed mass directly with a microbalance. This lets laboratories choose the apparatus they actually have, provided the method conditions are respected.

Multipoint and single-point evaluation

Clause 5.4 says the surface area determination normally uses at least three points in the relative-pressure region 0.05 < p/pr < 0.35, under equilibrium conditions. A single-point method is allowed only when lower accuracy is acceptable and the BET parameter C is high, which is important because it trades simplicity for reduced confidence.

Calculation and reporting

Clause 6 gives the BET equation, the linearized BET line, and the formulas for converting monolayer capacity into specific surface area. Clause 6.2 also states that precision depends on the equipment and that the user is responsible for method qualification, including calibration with a certified reference material. Clause 7 then defines the test-report items, including sample identification, result with expanded uncertainty, reference material used, instrument method, adsorbate purity, temperature, deviations, and unusual observations.

What changed in ISO/FDIS 12800 from the previous edition?

ISO/FDIS 12800 is the third edition and cancels and replaces ISO 12800:2017. The foreword lists these changes:

• the table of contents was adaptively revised
• Figure 1 in 4.2 was replaced
• new Subclauses 5.1.1 and 5.1.2 were added with carried-forward content
• new Subclauses 5.1.3 and 5.1.4 were added with new text
• Clause 5.2 was partially revised
• several editorial changes were made

Which standards are used with ISO/FDIS 12800?

ISO/FDIS 12800 cites ISO/IEC Guide 98-3 for expressing measurement uncertainty in the test report. That matters because the reported result needs an expanded uncertainty with the appropriate coverage factor.

ISO/FDIS 12800 also refers to ISO 9277, which provides the BET method basis for gas adsorption and supports the volumetric calculation approach. In this document, it is used for the BET equation, reference material practice, and the discussion of accurate volumetric measurement.

What does the ISO/FDIS 12800 document contain?

ISO/FDIS 12800 contains a principle section, a procedure section, calculation formulas, and a test-report clause. It includes Figure 1 for adsorption-isotherm classification and Figure 2 for the BET line, which are used to judge whether the sample behavior fits the method and to carry out the linear calculation.

Table 1 gives occupied areas per adsorbed molecule for nitrogen, argon, krypton, and xenon at stated temperatures. The document also gives practical descriptions of sample degassing, volumetric and gravimetric setups, a dynamic carrier-gas method, and a tracer method, so laboratories can adapt the guidance to their equipment and validation needs.

FINAL DRAFT
International
Standard
ISO/TC 85/SC 5
Nuclear fuel technology —
Secretariat: BSI
Guidelines on the measurement of
Voting begins on:
the specific surface area of uranium
2026-09-16
dioxide and plutonium dioxide
Voting terminates on:
powders by the BET method
2026-11-11
Technologie du combustible nucléaire — Lignes directrices pour
le mesurage de l'aire massique (surface spécifique) des poudres
d'oxyde d'uranium et de plutonium par la méthode BET
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 SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
ISO/CEN PARALLEL PROCESSING LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
FINAL DRAFT
International
Standard
ISO/TC 85/SC 5
Nuclear fuel technology —
Secretariat: BSI
Guidelines on the measurement of
Voting begins on:
the specific surface area of uranium
dioxide and plutonium dioxide
Voting terminates on:
powders by the BET method
Technologie du combustible nucléaire — Lignes directrices pour
le mesurage de l'aire massique (surface spécifique) des poudres
d'oxyde d'uranium et de plutonium par la méthode BET
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 SUPPOR TING DOCUMENTATION.
© ISO 2026
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
ISO/CEN PARALLEL PROCESSING
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
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Published in Switzerland Reference number
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
4.1 Summary of the BET method .1
4.2 Isothermal adsorption curves .2
4.3 Conditions and assumptions .2
5 Procedure . 3
5.1 Sample preparation .3
5.1.1 General .3
5.1.2 Uranium dioxide powders .3
5.1.3 Plutonium dioxide powders .3
5.1.4 Mass of sample .3
5.2 Volumetric measurement .3
5.3 Gravimetric measurement .4
5.4 Multipoint and single-point methods .4
5.5 Dynamic method (carrier gas method) .4
5.6 Alternative methods .4
6 Expression of results . 5
6.1 Methods of calculation .5
6.1.1 Multipoint determination .5
6.1.2 Single-point determination .7
6.2 Precision and accuracy .7
7 Test report . 7
Bibliography . 9

iii
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
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, in collaboration
with the European Committee for Standardization (CEN) Technical Committee CEN/TC 430, Nuclear energy,
nuclear technologies, and radiological protection, in accordance with the Agreement on technical cooperation
between ISO and CEN (Vienna Agreement) and with IEC/TC 76, Optical radiation safety and laser equipment.
This third edition cancels and replaces the second edition (ISO 12800:2017), which has been technically
revised.
The main changes are as follows:
— table of contents was adaptively revised;
— Figure 1 in 4.2 was replaced;
— new Subclauses 5.1.1 and 5.1.2 were added (headings only, the content was carried forward);
— new Subclauses 5.1.3 and 5.1.4 were added (entirely new text);
— content of 5.2 was partially revised;
— several editorial changes were added.
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
FINAL DRAFT International Standard ISO/FDIS 12800:2026(en)
Nuclear fuel technology — Guidelines on the measurement of
the specific surface area of uranium dioxide and plutonium
dioxide powders by the BET method
1 Scope
This document is applicable to nuclear fuel fabrication. It gives guidelines on the determination of the
specific surface area of as-fabricated uranium dioxide and plutonium dioxide powders by volumetric or
gravimetric determination of the amount of nitrogen adsorbed on the powder. For the measurement of other
uranium oxide powders, such as UO and U O , reference is made to the procedure for uranium dioxide. For
3 3 8
the measurement of MOX(UO -PuO ) powders, reference is made to the procedure for plutonium dioxide.
2 2
When conditions described are fulfilled, modifications using other adsorbing gases are included.
2 2
The method is applicable as long as the expected value is in the range from 1 m /g to 10 m /g for uranium
2 2
dioxide powders, in the range from 0.1 m /g to 45 m /g for plutonium dioxide powders.
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
...

ISO/TC 85/SC 5
Secretariat: BSI
Date: 2026-07-10xx
Nuclear fuel technology — Guidelines on the measurement of the
specific surface area of uranium dioxide and plutonium dioxide
powders by the BET method
Technologie du combustible nucléaire — Lignes directrices pour le mesurage de l'aire massique (surface
spécifique) des poudres d'oxyde d'uranium et de plutonium par la méthode BET
FDIS stage
TThihis drs draafftt i is s ssuubbmmiitttteedd ttoo aa ppaarraallellel l vvoottee i inn IISSOO,, CCEEN.N.

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: + 41 22 749 01 11
E-mail: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Contents
Foreword . iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
4.1 Summary of the BET method . 1
4.2 Isothermal adsorption curves . 1
4.3 Conditions and assumptions . 2
5 Procedure . 3
5.1 Sample preparation . 3
5.2 Volumetric measurement . 3
5.3 Gravimetric measurement . 4
5.4 Multipoint and single-point methods . 4
5.5 Dynamic method (carrier gas method) . 4
5.6 Alternative methods . 4
6 Expression of results . 5
6.1 Methods of calculation . 5
6.2 Precision and accuracy . 8
7 Test report . 8
Bibliography . 9

iii
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights
in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s)
which may be required to implement this document. However, implementers are cautioned that this may not
represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
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, in collaboration
with the European Committee for Standardization (CEN) Technical Committee CEN/TC 430, Nuclear energy,
nuclear technologies, and radiological protection, in accordance with the Agreement on technical cooperation
between ISO and CEN (Vienna Agreement) and with IEC/TC 76, Optical radiation safety and laser equipment.
This third edition cancels and replaces the second edition (ISO 12800:2017), which has been technically
revised.
The main changes are as follows:
— table of contents was adaptively revised;
— Figure 1 in 4.2 was replaced;
— new Subclauses 5.1.1 and 5.1.2 were added (headings only, the content was carried forward);
— new Subclauses 5.1.3 and 5.1.4 were added (entirely new text);
— content of 5.2 was partially revised;
— several editorial changes were added.
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
Nuclear fuel technology — Guidelines on the measurement of the
specific surface area of uranium dioxide and plutonium dioxide
powders by the BET method
1 Scope
This document is applicable to nuclear fuel fabrication. It gives guidelines on the determination of the specific
surface area of as-fabricated uranium dioxide and plutonium dioxide powders by volumetric or gravimetric
determination of the amount of nitrogen adsorbed on the powder. For the measurement of other uranium
oxide powders, such as UO and U O , reference is made to the procedure for uranium dioxide. For the
3 3 8
measurement of MOX(UO -PuO ) powders, reference is made to the procedure for plutonium dioxide. When
2 2
conditions described are fulfilled, modifications using other adsorbing gases are included.
2 2
The method is applicable as long as the expected value is in the range from 1 m /g to 10 m /g for uranium
2 2
dioxide powders, in the range from 0.1 m /g to 45 m /g for plutonium dioxide powders.
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
measurement (GUM:1995)
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at http://www.iso.org/obp
— IEC Electropedia: available at http://www.electropedia.org/
4 Principle
4.1 Summary of the BET method
The BET method is based on the determination of the amount of gas necessary to cover the surface by a
monomolecular layer. This amount is determined from the isothermal adsorption curve of nitrogen (N ) at
[1]
the temperature of liquid nitrogen (77,4 K) according to Reference . The amount of N adsorbed at a given
[2]
pressure is determined by volumetric or gravimetric measurement . In order to remove surface
contamination of the adsorbent, the sample has to be evacuated and heated under appropriate conditions
before the measurement is performed.
4.2 Isothermal adsorption curves
The isothermal adsorption curve describes the relationship between the mass of the adsorbate, m (N ),
A 2
adsorbed per gram of adsorbent (e.g. UO powder) at an equilibrium pressure of p at constant temperature T,
as shown in Formula (1):
𝑚𝑚 = ƒ(𝑝𝑝,𝑇𝑇) (1)
A
Generally, the relative pressure p/p is introduced instead of the absolute pressure p, where p is the
0 0
saturation vapour pressure which is 1,013 × 10 Pa for nitrogen at 77,4 K.
[3]
Most isothermal adsorption curves can be classified according to Reference to be one of the five common
types (see Figure 1).
Materials with pure micropores (with a diameter<2 nm) result in a type 1 adsorption curve. Most frequently,
types 2 and 4 adsorption curves are observed where the adsorption energy of the first layer, E , is much higher
than that of subsequent layers, E . When E ≈ E , type 3 or type 5 adsorption curves result. The BET method
n 1 n
can be applied to type 2 and type 4 cur
...

PROJET FINAL
Norme
internationale
ISO/TC 85/SC 5
Technologie du combustible
Secrétariat: BSI
nucléaire — Lignes directrices pour
Début de vote:
le mesurage de l'aire massique
2026-09-16
(surface spécifique) des poudres
Vote clos le:
d'oxyde d'uranium et de plutonium
2026-11-11
par la méthode BET
Nuclear fuel technology — Guidelines on the measurement of the
specific surface area of uranium dioxide and plutonium dioxide
powders by the BET method
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PROJET FINAL
Norme
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ISO/TC 85/SC 5
Technologie du combustible
Secrétariat: BSI
nucléaire — Lignes directrices pour
Début de vote:
le mesurage de l'aire massique
2026-09-16
(surface spécifique) des poudres
Vote clos le:
d'oxyde d'uranium et de plutonium
2026-11-11
par la méthode BET
Nuclear fuel technology — Guidelines on the measurement of the
specific surface area of uranium dioxide and plutonium dioxide
powders by the BET method
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Publié en Suisse
Numéro de référence
ii
Sommaire Page
Avant-propos .iv
1 Domaine d'application . 1
2 Références normatives . 1
3 Termes et définitions . 1
4 Principe. 1
4.1 Description de la méthode BET .1
4.2 Courbes isothermes d'adsorption .2
4.3 Conditions requises .2
5 Procédure . 3
5.1 Préparation de l'échantillon .3
5.1.1 Généralités .3
5.1.2 Poudres de dioxyde d'uranium .3
5.1.3 Poudres de dioxyde de plutonium.3
5.1.4 Masse d'échantillon .3
5.2 Méthode de mesure volumétrique .4
5.3 Méthode de mesure gravimétrique.4
5.4 Méthode multipoints et méthode dite “à point unique” .4
5.5 Méthode dynamique du gaz vecteur .4
5.6 Méthodes alternatives .4
6 Expression des résultats . 5
6.1 Méthodes de calcul . .5
6.1.1 Détermination multipoints .5
6.1.2 Détermination en un point .7
6.2 Fidélité et exactitude . .7
7 Rapport d'essai . 7
Bibliographie . 8

iii
Avant-propos
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Toutefois, il y a lieu d'avertir les responsables de la mise en application du présent document que des
informations plus récentes sont susceptibles de figurer dans la base de données de brevets, disponible à
l'adresse www.iso.org/brevets. L'ISO ne saurait être tenue pour responsable de ne pas avoir identifié tout ou
partie de tels droits de brevet.
Les appellations commerciales éventuellement mentionnées dans le présent document sont données pour
information, par souci de commodité, à l'intention des utilisateurs et ne sauraient constituer un engagement.
Pour une explication de la nature volontaire des normes, la signification des termes et expressions
spécifiques de l'ISO liés à l'évaluation de la conformité, ou pour toute information au sujet de l'adhésion de
l'ISO aux principes de l'Organisation mondiale du commerce (OMC) concernant les obstacles techniques au
commerce (OTC), voir www.iso.org/avant-propos.
Le présent document a été élaboré par le comité technique ISO/TC 85, Énergie nucléaire, technologies
nucléaires, et radioprotection, Sous-comité SC 5, Installations nucléaires, procédés et technologies, en
collaboration avec le comité technique du Comité européen de normalisation (CEN) CEN/TC 430, Énergie
nucléaire, technologies nucléaires, et radioprotection, conformément à l'accord de coopération technique entre
l'ISO et le CEN (Accord de Vienne) et avec l'IEC/TC 76, Sécurité des rayonnements optiques et matériels laser.
Cette troisième édition annule et remplace la deuxième édition (ISO 12800:2017), qui a fait l'objet d'une
révision technique.
Les principales modifications sont les suivantes:
— la table des matières a été révisée de manière adaptative;
— la Figure 1 au paragraphe 4.2 a été remplacée;
— les nouveaux paragraphes 5.1.1 et 5.1.2 ont été ajoutés (titres uniquement, le contenu a été reporté);
— les nouveaux paragraphes 5.1.3 et 5.1.4 ont été ajoutés (texte entièrement nouveau);
— le contenu du paragraphe 5.2 a été partiellement révisé;
— plusieurs modifications rédactionnelles ont été ajoutées.
Il convient que l'utilisateur adresse tout retour d'information ou toute question concernant le présent
document à l'organisme national de normalisation de son pays. Une liste exhaustive desdits organismes se
trouve à l'adresse www.iso.org/fr/members.html.

iv
PROJET FINAL Norme internationale ISO/FDIS 12800:2026(fr)
Technologie du combustible nucléaire — Lignes directrices
pour le mesurage de l'aire massique (surface spécifique) des
poudres d'oxyde d'uranium et de plutonium par la méthode
BET
1 Domaine d'application
Le présent document est applicable à la fabrication de combustible nucléaire. Il fournit des lignes directrices
relatives à la détermination de l'aire massique (surface spécifique) des poudres de dioxyde d'uranium et
de dioxyde de plutonium telles qu'elles sont fabriquées, par détermination volumétrique ou gravimétrique
de la quantité d'azote adsorbée sur la poudre. Pour la mesure d'autres poudres d'oxyde d'uranium, tel que
l'UO et l'U O , il est fait référence à la procédure relative au dioxyde d'uranium. Pour la mesure des poudres
3 3 8
MOX (UO -PuO ), il est fait référence à la procédure relative au dioxyde de plutonium. Lorsque les conditions
2 2
décrites sont remplies, des modifications utilisant d'autres gaz adsorbants sont incluses.
2 2
La méthode est applicable tant que la valeur attendue se situe dans la plage de 1 m /g à 10 m /g pour les
2 2
poudres de dioxyde d'uranium, dans la plage de 0,1 m /g à 45 m /g pour les poudres de dioxyde de plutonium.
2 Références normatives
Les documents suivants sont cités dans le texte de sorte qu'ils constituent, pour tout ou partie de leur
contenu, des exigences du présent document. Pour les références datées, seule l'édition citée s'applique. Pour
les références non datées, la dernière édition du document de référence s'applique (y compris les éventuels
amendements).
Guide ISO/IEC 98-3, Incertitude de mesure — Partie 3: Guide
...