ISO 16795:2024

Nuclear energy - Determination of Gd2O3 content in pellets containing uranium oxide by X-ray fluorescence spectrometry

This document specifies a method which covers the determination of Gd2O3 content in UO2 fuel pellets, by X-ray fluorescence spectrometry. Either wave dispersion X-ray fluorescence (WD-XRF) or energy dispersion X-ray fluorescence (ED-XRF) is applicable, however, this document states a method by using WD-XRF using Gd Lα-line. This method has been tested for mass fractions of from 2 % to 10 % Gd2O3.

Énergie nucléaire — Détermination de la teneur de Gd2O3 par spectrométrie à fluorescence X dans des pastilles combustibles contenant de l'oxyde d'uranium

Le présent document spécifie une méthode applicable à la détermination de la teneur en Gd2O3 dans les pastilles de UO2 par spectrométrie à fluorescence X. La méthode de fluorescence X à dispersion de longueur d’onde (WD-XRF) ou la méthode de fluorescence X à dispersion d’énergie (ED-XRF) est applicable. Dans le présent document, la méthode appliquée est la technique WD-XRF utilisant la raie Lα du Gd. Cette méthode a été testée pour des fractions massiques en Gd2O3 allant de 2 % à 10 %.

General Information

• Status: Published
• Publication Date: 21-Apr-2024
• 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 - Nuclear installations, processes and technologies
• Current Stage: 6060 - International Standard published
• Start Date: 22-Apr-2024
• Due Date: 21-Jun-2024
• Completion Date: 22-Apr-2024

Relations

• Revises: ISO 16795:2004 - Nuclear energy - Determination of Gd2O3 content of gadolinium fuel pellets by X-ray fluorescence spectrometry
• Effective Date: 25-Jun-2022

Overview

ISO 16795:2024 - "Nuclear energy - Determination of Gd2O3 content in pellets containing uranium oxide by X‑ray fluorescence spectrometry" - specifies a validated method to determine gadolinium oxide (Gd2O3) mass fraction in UO2 fuel pellets. The document describes an X‑ray fluorescence (XRF) approach (WD‑XRF is specified using the Gd Lα‑line, although ED‑XRF is noted as applicable) and has been tested for Gd2O3 mass fractions from 2 % to 10 %.

Key topics and requirements

• Technique: Wave‑dispersive X‑ray fluorescence (WD‑XRF) using the Gd Lα line (ED‑XRF also applicable).
• Sample preparation:
  • Standard pellets of (U,Gd)O2 prepared by blending UO2 and Gd2O3 powders.
  • Powders dried at 110 °C for 2 h, blended (shaken) for ≥4 h for homogeneity.
  • Pressing into pellets with the same size as production fuel pellets; sintered under production conditions (furnace up to ~1 800 °C).
  • Polishing of the pellet face with 800‑grit SiC paper and cleaning prior to analysis.
• Instrumentation & calibration:
  • Sequential X‑ray spectrometer with precision goniometer, LiF 200 analyser crystal, multi‑channel analyser, and appropriate detectors.
  • Mandatory calibration steps: angle calibration, pulse‑height distribution, background correction, and stability (sensitivity) check (drift monitor).
  • Linear calibration curve is generated from standard pellets covering 2 %–10 % Gd2O3 (Y = net count rate; X = mass fraction).
• Typical measurement parameters (as given): 40 kV voltage, 60 mA current, Gd Lα at 6.056 keV, 2θ ≈ 61.115°, counting time ~200 s, background correction ±1.20°.
• Quality and reporting:
  • Precision/accuracy examples: RMS of calibration curve ~0.014 %; coefficient of variation in tests ranged up to ~0.98 %.
  • Test report must identify the sample, reference ISO 16795:2024, list method, results, any deviations, calibration standard reference, and buoyancy correction status.

Applications and users

• Practical for nuclear fuel manufacturers, fuel quality control laboratories, and irradiation testing facilities requiring routine or acceptance testing of Gd2O3 doped UO2 fuel pellets.
• Useful where non‑destructive, high‑throughput compositional checks are needed during pellet production, calibration of process controls, or verification of burnable poison loading.
• Also applicable to laboratories preparing metrologically traceable working standards in accordance with ISO 17034 or ASTM C1128.

Related standards

• ISO 17034 (reference material producers)
• ASTM C1128 (preparation of working reference materials for nuclear fuel)
• ISO 12183, ISO 12749‑3, ISO 80000 (related nuclear and units references)

Keywords: ISO 16795:2024, Gd2O3, UO2 pellets, X‑ray fluorescence, WD‑XRF, Gd Lα‑line, calibration curve, fuel fabrication, nuclear fuel quality control.

Standards Content (Sample)

International
Standard
ISO 16795
Second edition
Nuclear energy — Determination
2024-04
of Gd O content in pellets
2 3
containing uranium oxide by X-ray
fluorescence spectrometry
Énergie nucléaire — Détermination de la teneur de Gd O par
2 3
spectrométrie à fluorescence X dans des pastilles combustibles
contenant de l'oxyde d'uranium
Reference number
© ISO 2024
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]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Apparatus . 1
6 Reagents . 2
7 Preparation of standards . 2
8 Polishing . 3
9 Equipment calibration . 3
9.1 Angle calibration.3
9.2 Pulse-height distribution .3
9.3 Background correction .3
9.4 Stability (sensitivity) check .3
10 Calibration curve . 4
11 Measurements . 4
12 Precision and accuracy . 4
13 Test report . 4
Annex A (informative) Angle calibration and background correction. 6
Annex B (informative) Precision and accuracy . 7
Bibliography . 8

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
This second edition cancels and replaces the first edition (ISO 16795:2004), which has been technically
revised.
The main changes are as follows:
— the title of this document has been modified;
— requirements for the standard pellet has been added in Clause 7;
— range of Gd O content covered by calibration curve has been added in Clause 10;
2 3
A list of all parts in the ISO 16795 series can be found on the ISO website.
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
International Standard ISO 16795:2024(en)
Nuclear energy — Determination of Gd O content in pellets
2 3
containing uranium oxide by X-ray fluorescence spectrometry
1 Scope
This document specifies a method which covers the determination of Gd O content in UO fuel pellets, by
2 3 2
X-ray fluorescence spectrometry.
Either wave dispersion X-ray fluorescence (WD-XRF) or energy dispersion X-ray fluorescence (ED-XRF) is
applicable, however, this document states a method by using WD-XRF using Gd Lα-line.
This method has been tested for mass fractions of from 2 % to 10 % Gd O .
2 3
2 Normative references
ISO 17034, General requirements for the competence of reference material producers
ASTM C1128, Standard Guide for Preparation of Working Reference Materials for Use in Analysis of Nuclear Fuel
Cycle Materials
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminology databases for use in standardization at th
...