SIST EN ISO 16793:2021

Nuclear fuel technology - Guidelines for ceramographic preparation of UO2 sintered pellets for microstructure examination (ISO 16793:2018)

This document describes the ceramographic preparation of uranium dioxide (UO2) sintered pellets for qualitative and quantitative microstructure examinations.
These examinations can be carried out before and after thermal or chemical etching.
They enable
—          observations of fissures, inter- or intra-granular pores and inclusions, and
—          measurement of pore and grain size and measurement of pore and grain size distributions.
The measurement of average grain size can be carried out using a classical counting method as described in ISO 2624 or ASTM E112[3], i.e. intercept procedure, comparison with standard grids or reference photographs.
The measurement of pore-size distributions is usually carried out by an automatic image analyser. If the grain-size distributions are also measured with an image analyser, it is recommended that thermal etching be used to reveal the grain structure uniformly throughout the whole sample.

Kernbrennstofftechnologie - Leitfaden für die keramographische Herstellung gesinterter UO2-Pellets zur Untersuchung des Feingefüges (ISO 16793:2018)

Technologie du combustible nucléaire - Lignes directrices pour la préparation céramographique de pastilles UO2 frittées pour l'examen de la microstructure (ISO 16793:2018)

Le présent document décrit la préparation céramographique de pastilles de dioxyde d'uranium (UO2) frittées, permettant de réaliser des examens qualitatifs et quantitatifs de leur microstructure.
Ces examens peuvent être réalisés avant et après une attaque chimique ou thermique.
Ils permettent
—          l'observation des fissures, des pores intergranulaires ou intragranulaires et des inclusions, et
—          le mesurage de la taille des grains et de la porosité, ainsi que de leur distribution.
Le mesurage de la taille moyenne des grains peut être effectué par une méthode courante de comptage décrite dans l'ISO 2624 ou l'ASTM E112[3], c'est-à-dire une méthode par interception, comparaison avec des grilles normalisées ou avec des images types.
Le mesurage de la distribution des tailles de pores est généralement effectué par un analyseur d'images automatique. Si la distribution granulométrique est également mesurée avec un analyseur d'images, il est recommandé d'utiliser une attaque thermique pour révéler de façon uniforme la structure des grains de l'ensemble de l'échantillon.

Tehnologija jedrskih goriv - Smernice za pripravo keramografske preiskave mikrostrukture za sintrane pelete UO2 (ISO 16793:2018)

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 16793:2021 - Nuclear fuel technology - Guidelines for ceramographic preparation of UO2 sintered pellets for microstructure examination (ISO 16793:2018)

Overview

EN ISO 16793:2021 - "Nuclear fuel technology - Guidelines for ceramographic preparation of UO2 sintered pellets for microstructure examination" provides harmonized, practical guidance for preparing uranium dioxide (UO2) sintered fuel pellets for both qualitative and quantitative microstructural analysis. The standard covers sample sectioning, mounting options, grinding, polishing, dismounting, and both chemical and thermal etching to reveal grains, pores, fissures and inclusions for microscopy and image analysis.

Key topics and requirements

• Scope of examination: Observations of fissures, inter- and intra-granular pores, inclusions; measurement of pore and grain sizes and distributions.
• Preparation procedures: Three principal workflows - unmounted samples, mounted samples that remain mounted, and mounted samples that require later dismounting.
• Sectioning & equipment: Use of a metallographic sectioning machine with a diamond wheel and water inlet; manual or automatic polishing machines; ultrasonic cleaning; vacuum impregnation; thermal etching furnace; mechanical gripping devices and optical microscopes.
• Polishing & consumables: Abrasive papers (P60–P2500), diamond polish suspensions (0.25–15 µm), aqueous alumina/silica suspensions (0.05–1 µm), and various polishing cloths.
• Etching methods: Guidance on chemical etching and thermal etching (thermal etching requires unmounted samples and is recommended when image analysis is used to measure grain-size distributions to ensure uniform grain revelation). Thermal etching is performed under an oxidizing CO2 atmosphere.
• Measurement techniques: Average grain-size measurement may follow classical counting/intercept procedures as per ISO 2624 or ASTM E112. Pore-size distributions are commonly measured with automatic image analysers.
• Safety & reagents: Lists hazardous reagents used (e.g., hydrogen peroxide, concentrated sulfuric acid, hydrofluoric acid, chromium (VI) oxide) and the need for appropriate PPE and ventilation (fume hood) when handling them.

Applications and users

EN ISO 16793:2021 is intended for:

• Nuclear fuel manufacturers and fabrication quality-control laboratories
• Materials scientists and metallographers working on UO2 pellet microstructure
• Research institutions studying sintering, porosity, grain growth and failure mechanisms
• Regulatory and certification bodies assessing fuel microstructure for safety and performance

The standard supports routine production inspection, failure analysis, research characterization, and image-analysis workflows for assessing grain size and pore distributions in nuclear fuel pellets.

Related standards

• ISO 2624 - grain-size measurement methods (classical counting/intercept)
• ASTM E112 - standard for determining average grain size
• ISO 3696 - demineralized water quality (referenced for consumables)

Keywords: EN ISO 16793:2021, ceramographic preparation, UO2 sintered pellets, microstructure examination, thermal etching, chemical etching, grain size, pore-size distribution, image analyser.

Standards Content (Sample)

SLOVENSKI STANDARD
01-april-2021
Tehnologija jedrskih goriv - Smernice za pripravo keramografske preiskave
mikrostrukture za sintrane pelete UO2 (ISO 16793:2018)
Nuclear fuel technology - Guidelines for ceramographic preparation of UO2 sintered
pellets for microstructure examination (ISO 16793:2018)
Technologie du combustible nucléaire - Lignes directrices pour la préparation
céramographique de pastilles UO2 frittées pour l'examen de la microstructure (ISO
16793:2018)
Ta slovenski standard je istoveten z: EN ISO 16793:2021
ICS:
27.120.30 Cepljivi materiali in jedrska Fissile materials and nuclear
gorivna tehnologija fuel technology
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 16793
EUROPEAN STANDARD
NORME EUROPÉENNE
February 2021
EUROPÄISCHE NORM
ICS 27.120.30
English Version
Nuclear fuel technology - Guidelines for ceramographic
preparation of UO2 sintered pellets for microstructure
examination (ISO 16793:2018)
Technologie du combustible nucléaire - Lignes
directrices pour la préparation céramographique de
pastilles UO2 frittées pour l'examen de la
microstructure (ISO 16793:2018)
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 16793:2021 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
The text of ISO 16793:2018 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 16793:2021 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 16793:2018 has been approved by CEN as EN ISO 16793:2021 without any modification.

INTERNATIONAL ISO
STANDARD 16793
Second edition
2018-08
Nuclear fuel technology — Guidelines
for ceramographic preparation of UO
sintered pellets for microstructure
examination
Technologie du combustible nucléaire — Lignes directrices pour la
préparation céramographique de pastilles UO frittées pour l'examen
de la microstructure
Reference number
ISO 16793:2018(E)
©
ISO 2018
ISO 16793:2018(E)
© ISO 2018
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
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Published in Switzerland
ii © ISO 2018 – All rights reserved

ISO 16793:2018(E)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Procedures . 2
5.1 General . 2
5.2 Sample preparation without mounting . 2
5.3 Sample preparation with mounting, not needing subsequent dismounting . 2
5.4 Sample preparation with mounting, needing subsequent dismounting . 2
6 Apparatus . 2
7 Reagents and consumables . 3
8 Methods . 4
8.1 Sectioning . 4
8.2 Mounting . 4
8.3 Grinding . 4
8.4 Polishing . 5
8.5 Dismounting . 5
9 Etching . 5
9.1 Introduction . 5
9.2 Chemical etching . 5
9.3 Thermal etching . 5
Bibliography . 8
ISO 16793:2018(E)
Foreword
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bodies (ISO member bodies). The work of preparing International Standards is normally carried out
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