China ramps up CHSN01 fusion magnet jacket for cryogenic reactors

by Riko Seibo
Tokyo, Japan (SPX) Jan 06, 2026
China has produced 30 tons of cryogenic jacket material made from its CHSN01 steel in continuous lengths of about 5 km for use in Cable-in-Conduit Conductors for future fusion reactors. The jacket is designed for magnets that must endure strong fields and very low temperatures in advanced fusion devices.

Mechanical tests at 4.2 K show the CHSN01 jacket reaches an average yield strength of 1560 MPa, elongation of 32.7%, and fracture toughness of 220 MPa-m1/2. These values indicate the steel can resist high loads while still deforming and absorbing energy before fracture under cryogenic conditions.

Compared with widely used 316LN steel, the CHSN01 jacket delivers about 40 percent higher yield strength while maintaining similar plasticity and toughness. Fatigue testing also shows better resistance to crack growth than both 316LN and JK2LB jackets.

At around 20 K, CHSN01 combines non-magnetic behavior with high strength and toughness, which is important for superconducting fusion magnets that must operate in strong magnetic fields without magnetic interference from support structures. The balance of properties positions CHSN01 as a candidate material for next-generation fusion magnet jackets.

The same performance characteristics could enable lighter or more compact structures in other cryogenic systems, including spaceflight propellant tanks and hydrogen energy infrastructure. In these applications, CHSN01 may replace 316LN where higher strength is required without sacrificing ductility or toughness.

The complete study is accessible via DOI: 10.1007/s41365-025-01847-5.

Research Report: Mass production and performance evaluation of CHSN01 jacket for future fusion applications

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