Foreword

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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.

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 mostly derived from the tokamak configuration but also applicable to other configurations and layouts that may be adopted by future fusion devices.

2 Normative references

3 Terms and definitions

4 Application of superconductivity in fusion facilities

4.1 Overview of the superconducting magnet system

4.2 Safety systems present in fusion facilities

5 Requirements for confinement system

5.1 General

5.2 Requirements associated with the presence of superconducting magnets

5.3 Protection of confinement system against magnetic energy

5.4 Protection of confinement system against other hazard

6 Requirements for radiation protection

6.1 Safe operation

6.2 Maintenance and repairability

7 Requirements specific to other systems

7.1 Plasma performance monitoring system

7.2 Magnetic diagnosis and monitoring system

7.3 Quench detection and protection system

7.4 Diagnosis and monitoring system in support of confinement systems

7.5 Other requirements

Bibliography

ISO 18518:2025

Magnetic fusion facilities. Requirements for the safety systems raised by the application of the superconducting technology

Current

Published:

22 Sep 2025