ISO 1709:2018

Nuclear energy - Fissile materials - Principles of criticality safety in storing, handling and processing

ISO 1709:2018 specifies the basic principles and limitations which govern operations with fissile materials. It discusses general nuclear criticality safety criteria for equipment design and for the development of operating controls, while providing guidance for the assessment of procedures, equipment, and operations. It does not cover specific quality assurance requirements or details of equipment or operational procedures. ISO 1709:2018 does not deal with the issues associated with administrative criteria relating to nuclear criticality safety. These issues are covered by ISO 14943. It does not cover the effects of radiation on man or materials, unless the material properties affect nuclear criticality safety. These criteria apply to operations with fissile materials outside nuclear reactors but within the boundaries of nuclear establishments. They are concerned with the limitations which are imposed on operations because of the properties of these materials which permit them to support nuclear chain reactions. These principles apply to quantities of fissile nuclides in which nuclear criticality safety is required to be established. ISO 1709:2018 can also be applied to the transport of fissile materials outside the boundaries of nuclear establishments.

Énergie nucléaire — Matières fissiles — Principes de sûreté-criticité lors des opérations d'entreposage, de manutention et de mise en oeuvre du procédé

General Information

• Status: Published
• Publication Date: 11-Feb-2018
• 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 8 - Nuclear criticality safety
• Current Stage: 9093 - International Standard confirmed
• Start Date: 06-Jul-2023
• Completion Date: 13-Dec-2025

Relations

• Amended By: ISO 1709:2018/Amd 1:2022 - Nuclear energy - Fissile materials - Principles of criticality safety in storing, handling and processing - Amendment 1: Methods of control and safety equipment
• Effective Date: 04-Sep-2021
• Revises: ISO 1709:1995 - Nuclear energy - Fissile materials - Principles of criticality safety in storing, handling and processing
• Effective Date: 04-Nov-2015

Overview

ISO 1709:2018 - "Nuclear energy - Fissile materials - Principles of criticality safety in storing, handling and processing" defines the fundamental principles and limitations for operations with fissile materials outside reactors. The standard provides guidance for nuclear criticality safety, focusing on equipment design, operating controls and the assessment of procedures and operations. It applies within the boundaries of nuclear establishments and can also be used for the transport of fissile materials. ISO 1709:2018 does not prescribe detailed quality-assurance requirements, administrative criteria (see ISO 14943), or radiation-health effects except where material properties affect criticality safety.

Key topics and technical requirements

ISO 1709:2018 addresses the following technical topics and requirements:

• Procedures and responsibilities

  • Clear assignment of operational responsibility for criticality safety.
  • Written procedures for operations above threshold quantities and visible availability in operating areas.
  • Review of procedures by personnel skilled in nuclear criticality safety, ideally administratively independent from operations.

• Equipment design and control

  • Incorporation of safety into equipment geometry and plant design to reduce criticality risk.
  • Equipment control and design restrictions to maintain subcritical configurations.

• Criticality assessment and demonstration of safety

  • Requirement for a nuclear criticality safety assessment for applicable operations, considering normal and credible abnormal conditions.
  • Use of established criteria and demonstration of an appropriate margin of criticality safety.

• Technical criteria and factors affecting criticality

  • Methods of control and achievement of control (defence-in-depth).
  • Factors: mass, geometry, volume, concentration, moderation, neutron absorbers, physical/chemical form, density, enrichment, reflection, interaction, temperature.
  • Consideration of possible abnormal conditions and processing violations.

• Operational controls and monitoring

  • Material control, dispatch/receipt procedures, training, monitoring of procedures.
  • Need for emergency planning and criticality detection/alarm systems where appropriate.

Practical applications

ISO 1709:2018 is used to:

• Develop and validate criticality safety assessments and operating limits.
• Inform design criteria for storage vessels, containers and processing equipment to avoid inadvertent criticality.
• Establish written operating procedures, training programs and monitoring controls.
• Support safety analyses for handling, processing and short-term transport of fissile materials.

Who should use this standard

• Nuclear criticality safety engineers and analysts
• Plant/process designers and equipment manufacturers
• Nuclear facility operators and operations management
• Regulatory bodies, safety auditors and compliance teams
• Transport planners handling fissile consignments outside reactor cores

Related standards

• ISO 7753 - criticality detection and alarm systems
• ISO 11320 - emergency preparedness and response for nuclear criticality safety
• ISO 14943 - administrative criteria for nuclear criticality safety

Keywords: ISO 1709:2018, nuclear criticality safety, fissile materials, criticality assessment, equipment design, storage, handling, processing, criticality alarm, transport.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 1709
Third edition
2018-02
Nuclear energy — Fissile materials
— Principles of criticality safety in
storing, handling and processing
Énergie nucléaire — Matières fissiles — Principes de sûreté-criticité
lors des opérations d'entreposage, de manutention et de mise en
oeuvre du procédé
Reference number
©
ISO 2018
© 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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below or ISO’s member body in the country of the requester.
ISO copyright office
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Published in Switzerland
ii © ISO 2018 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Procedures . 3
4.1 General . 3
4.2 Responsibility . 3
4.3 Equipment design. 3
4.4 Criticality assessment . 3
4.5 Written procedures . 3
4.6 Review of procedures . 4
4.7 Processing violations . 4
4.8 Training . 4
5 Technical criteria . 4
5.1 General . 4
5.2 Methods of control . 4
5.3 Achievement of control . 4
5.4 Factors affecting criticality . 5
5.4.1 General. 5
5.4.2 Mass . 5
5.4.3 Geometry . 5
5.4.4 Volume . 5
5.4.5 Concentration . 5
5.4.6 Moderation. 5
5.4.7 Neutron absorbers . 5
5.4.8 Physical and chemical form . 6
5.4.9 Density . 6
5.4.10 Enrichment . 6
5.4.11 Reflection . . 6
5.4.12 Interaction . 6
5.4.13 Temperature . 6
5.5 Possible abnormalities . 7
5.6 Bases of assessment . 7
5.7 Margin of criticality safety . 7
5.8 Demonstration of safety . 7
6 Equipment control . 8
7 Material control . 8
8 Dispatch and receipt of material . 8
9 Monitoring of procedures . 8
10 Need for an emergency plan and criticality alarm . 8
Bibliography . 9
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
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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).
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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.
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 1709:1995), which has been technically
revised.
A list of all parts in the ISO 1709 series can be found on the ISO website.
iv © ISO 2018 – All rights reserved

INTERNATIONAL STANDARD ISO 1709:2018(E)
Nuclear energy — Fissile materials — Principles of
criticality safety in storing, handling and processing
1 Scope
This document specifies the basic principles and limitations which govern operations with fissile
materials. It discusses general nuclear criticality safety criteria for equipment design and for the
development of operating controls, while providing guidance for the assessment of procedures,
equipment, and operations. It does not cover specific quality assurance requirements or details of
equipment or operational procedures.
This document does not deal with the issues associated with administrative criteria relating to nuclear
criticality safety. These issues are covered by ISO 14943. It does not cover the effects of radiation on
man or materials, unless the material properties affect nuclear criticality safety.
These criteria apply to operations with fissile materials outside nuclear reactors but within the
boundaries of nuclear establishments. They are concerned with the limitations which are imposed on
operations because of the properties of these materials which permit them to support nuclear chain
reactions. These principles apply to quantities of fissile nuclides in which nuclear criticality safety is
required to be established.
This document can also be applied to the transport of fissile materials outside the boundaries of nuclear
establishments.
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 7753, Nuclear energy — Performance and testing requirements for criticality detection and alarm systems
ISO 11320, Nuclear criticality safety — Emergency preparedness and response
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
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/
3.1
critical
having an effective neutron multiplication factor equal to unity
3.2
double batching
unintended increase in the quantity of a material that is controlled for Nuclear Criticality Safety such
that twice the intended quantity is present
Note 1 to entry: This typically applies to processes involving discrete quantities of material.
3.3
fissile material
material, other than natural or depleted uranium, that is capable of sustaining a thermal neutron chain
reaction
3.4
fissile nuclide
nuclide capable of undergoing fission by interaction with neutrons of any energy
3.5
credible abnormal conditions
identified faults and/or circumstances outside of the normal envelope of operations that may lead to an
unsafe situation
3.6
neutron absorber
material with which neutrons interact significantly by reactions resulting in their disappearance as
free particles
3.7
neutron leakage
neutrons leaving a fissile system boundary such that they no longer interact with that system
Note 1 to entry: For an array of fissile units, neutron leakage from one unit may or may not interact with other units.
3.8
nuclear chain reaction
series of nuclear reactions in which one of the agents necessary to the series is itself produced by the
same reactions
3.9
nuclear criticality accident
release of energy as a result of inadvertently producing a self-sustaining or divergent nuclear chain
reaction
3.10
nuclear criticality safety
protection against the consequences of a nuclear criticality accident, preferably by prevention of the
accident and responses to such accidents should they occur
3.11
nuclear criticality risk assessment
technically reviewed analysis that establishes the technical bases, limits, and controls for the nuclear
criticality safety of a given operation
3.12
defence-in-depth
hierarchical deployment of different levels of diverse equipment and procedures (known as barriers) to
prevent the escalation of faults to a hazardous condition
[SOURCE: IAEA Safety Glossary 2007 Edition, modified — The definition has been modified.]
3.13
over batching
unintended increase in the quantity of a material that is controlled for Nuclear Criticality Safety such
that one or more extra discrete quantities are present
2 © ISO 2018 – All rights reserved

3.14
criticality safety control
mechanism which provides a high level of assurance that the probability of occurrence of a critical
excursion is acceptably low
Note 1 to entry: An engineered feature (active or passive) or administrative requirement that establishes
constraints on the range of values that process parameters can assume with a given reliability (i.e. failure
frequency), thereby, providing a barrier to a criticality accident.
4 Procedures
4.1 General
The early recognition of the special hazards associated with fissile materials has led to the application
of formal control practices based on principles of nuclear criticality safety. Diligent and conscientious
application of these principles has produced an accident record which compares favourably with
common industrial accidents. Continuation and improvement of this generally favourable record should
have the cooperation of all those involved in operations.
4.2 Responsibility
Operational responsibility for nuclear criticality safety shall be clearly defined and shall bel
...