China’s fusion roadmap

China started nuclear fusion research in the 1960s and scientists and engineers have continued fusion-oriented technology research and with steady achievements.

Two major research institutes are contributing to Chinese magnetic-confined fusion development: the Institute of Plasma Physics, under Hefei Institutes of Physical Science, Chinese Academy of Sciences (ASIPP); and the Southwestern Institute of Physics (SWIP).

Fusion scientists from ASIPP have reconstructed the first domestic superconducting tokamak, the medium sized tokamak HT-7. The HT-7 tokamak has made significant contributions to the research on tokamak steady-state operation.

Fusion-oriented research progressed with construction of the HL-1 (upgrade HL-1M) in SWIP and other small tokamaks such as the KT-5 in the University of Sciences and Technology of China (USTC) and the upgraded CT-6B at the Institute of Physics of the Chinese Academy of Sciences (IP CAS) in Beijing.

A sound fundamental knowledge base of plasma physics research has been accumulated through experiments with these operating fusion tokamaks at the earlier research stage, which laid a solid foundation for the next fusion machine, the China Fusion Engineering Testing Reactor (CFETR). The preliminary conceptual design of CFETR was finished in 2015 and engineering design started in 2017.

Though controlled fusion technology is not yet approaching the commercial market, with many challenges still to overcome, we are close enough to witness the final challenging stages of development. There are extensive efforts and developments from a great many scientists and technicians from more than one hundred fusion research laboratories all over the world.

Fusion development in China

After about three years of intensive discussion in the Chinese fusion community, in 2015 consensus was reached on a roadmap of Chinese magnetic-confined fusion future development. Based on the roadmap, the three major domestic fusion tokamaks — EAST, HL-2M and J-TEXT — will continue offering reference and experimental validation for CFETR, which is the next-step tokamak device planned for the Chinese magnetic confinement fusion programme. These domestic tokamaks have also made significant contributions to the international fusion efforts at ITER.

In the next decade, the world fusion community will work together to complete ITER construction and begin operation. Each of ITER’s participant countries has plans to apply successful experience at ITER to its own programme to accelerate commercialisation. By joining ITER, a centre of excellence has been developed for specialists and engineers and Chinese fusion development has accelerated. ITER’s technology can provide the foundation for China’s future magnetic-confined fusion development.

Chinese fusion devices

The three major domestic tokamaks now in operation in China are the EAST machine in ASIPP at Hefei, HL-2A(M) in SWIP at Chengdu and J-TEXT at the Huazhong University of Science and Technology (HUST).

With experience from the HT-7 facilities and researchers at ASIPP, the EAST device at Hefei is aiming to hold plasma for exploitation for up to 1000 seconds. With an operating time of about ten years, EAST’s achievements have been in steady-state high-power operations and it has been upgraded to allow for research into long-pulse H-mode operation (steady-state/400s) with dominant electron heating.

The first divertor tokamak in China, HL-2A, was built at SWIP, with modifications to the original German ASDEX major components. Among its achievements are the divertor configuration discharge, diversified ELM mitigation techniques and other important physics issues relevant to the operation of ITER. The new advanced divertor configuration tokamak HL-2M, with a copper conductor, is an upgrade of the HL-2A machine and is under construction in SWIP. It has a major/minor radius of 1.78m/0.65m.

Universities in China been working on the plasma physics of magnetic confinement for nuclear fusion for nearly half a century. HUST has hosted the Joint-TEXT tokamak (J-TEXT) since 2004. It has allowed many young nuclear fusion scientists and technicians to engage in basic plasma physics research. USTC is another university specialising in theoretical plasma physics research and it has undertaken several critical ITER programmes. USTC’s newly-built medium-size Keda Torus eXperiment (KTX) plays an important role in developing the technologies required for fusion and is expected be an experimental test bed for new theories.

All these tokamaks have made substantial contributions not only in accelerating magnetic confinement fusion development but also in training scientists and engineers devoted to fusion development.

CFETR design and R&D

CFETR is designed to bridge the fusion experiments ITER and DEMO. It is based on earlier domestic fusion devices and aims to allow earlier realisation of fusion applications.

CFETR is expected to be the next magnetic confinement fusion machine. It aims for steady-state operation, as well as tritium self-sustainment. In phase one it should have 200MW fusion power and in phase two it should have power of 1GW to provide DEMO validation. Its main objectives are to: complement ITER; demonstrate full-cycle fusion at energies from 200MW to over 1GW; full tritium fuel cycle demonstration, with a tritium breeding ratio above 1.0; steady-state operation, with a duty cycle of about 0.3-0.5; explore options for easily changeable in-vessel components using remote handling techniques; address the physical and technical solutions for achieving steady state advanced operation and for licensing DEMO.

In concept design, CFETR has 13 subsystems: plasma physics and technology; layout design and system integration; superconducting magnet and cryogenics; in-vessel components; vacuum vessel and vacuum system; diagnosis and CODAC; heating and current drive system; electric power and control system; radiation protection and safety; remote control and maintenance system; fuel circulation system and waste disposal; auxiliary supporting system; and project management.

It took nearly four years to complete the concept design of CFETR. Previous studies mainly focused on a smaller machine (Phase 1) with major/minor radius R=5.7m, a=1.6m and BT=4–5T. To fulfil the objectives of Phase 2, the CFETR machine must be upgraded to a larger size. It is expected to have R=7–7.2m, a=2.2m, BT=6–7T.

Aggressive advanced plasma performance will lower the construction cost and smooth transfer to Phase 2, with the same machine able to meet the targets of both phases. Challenges remain on the power handling on the blanket and divertor, as well as managing material damage from neutron and high heat flux.

A combination of three heating and current drive systems — electron cyclotron waves, neutral beam and lower hybrid waves — will help achieve CFETR steady state operation. Each of the three systems plays a different role.

Tritium breeding is still among the most important issues for CFETR. Work in blanket configuration design and T-plant design have resulted in optimised and more appropriate tritium breeding.

Many other technical difficulties remain to be addressed before CFETR can reach successful construction and operation: they include material and component performance, plasma performance and safety issues. It takes time to address the technical and scientific issues and develop a sound experimental database.

China has progressed the CFETR to the detailed engineering stage, as part of a push towards the exploitation of a new energy source.

During CFETR design and R&D testing and verification is being carried out to add to the experimental database, but delays have slowed the development of CFETR. To address this problem, new research facilities to provide an experimental platform for CFETR pre-research have been proposed in China’s National Thirteenth Five-Year Plan.

CFTER construction will be conducted as scheduled in the 2020s if approved by Chinese government in time. It is expected to be complete in the 2030s. First it will be used to explore steady-state operation and tritium self-sustainment with a target of 200MW fusion power. The later phase, finishing in the 2040s, will encompass experimental studies for validation of critical issues for the fusion tokamak DEMO. It is thought that 2050 will see the start of construction of a prototype fusion power plant. This will be the final step in the Chinese roadmap towards a commercial fusion power plant.

Summary

As the formal partner of ITER with over fifty years of engagement in fusion research, China has made a remarkable contribution to the global fusion development.

According to the 2015 fusion roadmap the achievements of the EAST devices in ASIPP, the leading tokamak HL-2A(M) in SWIP and J-TEXT in HUST will continue to provide a solid foundation for the next fusion machine, CFETR.

Conceptual design of CFETR was finished in 2017, and detailed engineering design, large scale R&D and integrated simulation has started and will continue to fill the gaps that need to be overcome for the successful construction and operation of CFETR.

Energy plays a crucial role in human development, and people and nations share the same atmosphere on our planet. Together we will reap the benefits from reducing emissions of greenhouse gases and other pollutants. With strong support from the central government and joint cooperation from the research institutes, universities, developing industries and the international fusion community, the Chinese fusion development programme will keep moving forwards.

Author information: Yuntao Song, Professor, Institute of Plasma Physics, Chinese Academy of Sciences, Anhui, China