ISO 18518:2025

International
Standard
ISO 18518
First edition
Magnetic fusion facilities —
2025-09
Requirements for the safety systems
raised by the application of the
superconducting technology
Installations de fusion par confinement magnétique - Exigences
applicables aux systèmes de sûreté soulevées par l'application de
la technologie supraconductrice
Reference number
© ISO 2025
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Application of superconductivity in fusion facilities . 4
4.1 Overview of the superconducting magnet system .4
4.1.1 General .4
4.1.2 Cryogenic technology needed in superconducting magnet system .4
4.1.3 Auxiliary systems to the superconducting magnet system .5
4.2 Safety systems present in fusion facilities .5
4.2.1 Confinement system .5
4.2.2 Nuclear shielding system .5
4.2.3 Auxiliary safety system .6
5 Requirements for confinement system . 6
5.1 General .6
5.2 Requirements associated with the presence of superconducting magnets .6
5.3 Protection of confinement system against magnetic energy.7
5.4 Protection of confinement system against other hazard .7
6 Requirements for radiation protection . 8
6.1 Safe operation.8
6.2 Maintenance and repairability .8
7 Requirements specific to other systems . 10
7.1 Plasma performance monitoring system .10
7.2 Magnetic diagnosis and monitoring system .10
7.3 Quench detection and protection system .10
7.4 Diagnosis and monitoring system in support of confinement systems .11
7.5 Other requirements .11
Annex A (informative) Example of Paschen curve.12
Annex B (informative) Examples of radiation design limits for super-conducting coils in ITER
and DEMO .13
Annex C (informative) Examples of peak factors used in the ITER one dimensional neutronic
design analyses. 14
Annex D (informative) Vacuum vessel, first wall and blanket examples .15
Annex E (informative) Arcing prevention in superconducting magnets . 17
Bibliography . 19

iii
Foreword
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iv
Introduction
Fusion energy has the potential to serve as the ultimate carbon-free energy solution. Following significant
development and improvement on fusion science and technology, magnetic confined devices such as tokamak
or stellarators have become one of the main routes pursuing the fusion energy for a productive realisation.
Therefore, magnets are essential components of any Tokamak fusion device. After over decades’ development,
the magnets applied in Tokamak devices have evolved from ordinary magnets to superconducting magnets.
For instance, EAST in China, KSTAR in Korea and JT60-SA in Japan are all superconducting tokamak devices.
ITER (international thermonuclear experimental reactor) is the first fusion nuclear reactor in the world
with three main sets of superconducting magnets, namely TF (Toroidal Field) magnets, PF (Poloidal Field)
magnets and CS (Central Solenoid) magnets. For future magnetic fusion based reactors, such as various
fusion DEMO reactors (DEMOnstration reactors) proposed by different stakeholders, same types of magnets
will be anticipated in place in order to confine and shape the fusion plasma core, and to drive the plasma
current.
There are two primary safety functions in a fusion facility, namely the confinement of radioactive species
and the shielding protection against ionizing radiation. A set of safety systems need to be implemented in
order to realise the safety functions. For example, the confinement function would be realised by various
static and dynamic confinement barriers; the shielding function would be supplied by bulk of components
for the attenuation and absorption of neutrons and photons. The introduction and the application of the
superconducting technology would bring changes to subsequently lead to new requirements to the safety
systems in fusion facilities. There are some new risks and hazards associated with superconducting magnet
systems, e.g., the accidental discharge of the magnetic energy which may threaten the integrity of the first
confinement barrier, namely vacuum vessel in a fusion facility; the accidental outbreak of the cryogenic
coolant helium which may breach the cryostat and/or penetrations through building walls that are also
part of confinement barriers. In a D-T fusion facility, the superconducting magnet system would inevitably
operate in a radiation environment, thus, the shielding capability of such fusion facility should not only be
adequate to protect the workers and the public, but also aim to minimise the possibility to compromise the
reliability and the performance of the electronics and devices employed by the superconducting magnet
system. It should also facilitate the repairability of large-scale superconducting magnet by reducing and
minimising the radiation exposure to an as low as reasonably achieved (ALARA) in the associated nuclear
environment. Moreover, it should reduce the amount of radioactive waste by reducing the activation of
structural material of coils.
v
International Standard ISO 18518:2025(en)
Magnetic fusion facilities — Requirements for the safety
systems raised by the application of the superconducting
technology
1 Scope
This document specifies requirements concerning safety systems raised by the application of
superconducting magnets in fusion facilities. Safety systems include confinement systems (both static and
dynamic types), shielding barriers, penetrations, and supporting systems such as instrumentation and
control.
The requirements are applicable to both normal and abnormal operation of a fusion facility. For instance,
the radiation protection shall be adequate in order to permit the hands-on operation to the electronics and
parts for inspection, maintenance and replacement; the hazards associated with superconducting magnets,
such as the loss of superconductivity (quench), Paschen breakdown following helium and voltage leakage,
shall be prevented from breaching the integrity of safety systems.
This document will facilitate the design and assessment of the safety systems in a fusion facility with
superconducting magnets for all configurations, such as tokamak, stellarator and magneto-inertial fusion
devices. Based on the advancement and maturity of the tokamak configuration, this document outlines safety
requirements most
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