ENEA’s Divertor Tokamak Test (DTT) Facility to use Metrosil energy extraction and overvoltage protection

Each set of protection Metrosil’s will extract 684 MJ, at a nominal current of 42.5 kA while clamping overvoltages at 5.1 kV

(Manchester, UK, August 2023), Specialist electrical protection equipment is to be deployed on a new fusion energy project in an industry-first. ENEA, Italy’s National Agency for New Technologies, Energy and Sustainable Economic Development and its partners have specified Metrosil, made by UK-based M&I Materials, to protect superconducting magnets on its Divertor Tokamak Test (DTT) green energy project.

Metrosil patented silicon carbide (SiC) varistor tile systems are designed to clamp voltage to a required magnitude and quickly extract energy stored in superconducting magnets during a quench. The design of each unit has been optimised for ease of installation and M&I Materials’ High Energy Test Laboratory (HETL) guarantees and certifies protection from a quench at maximum operating current – preventing damage to the magnet and costly maintenance.

These special high energy units deliver the highest energy density of any SiC power varistor system available today, while providing a compact, space-saving installation.

Metrosil SiC tiled units will provide the energy extraction and overvoltage protection for the DTT’s TF (Toroidal Field) coil circuit and be used for testing of the CS (Central Solenoid) and PF (Poloidal Field) Coils. The Metrosil High Energy varistor system will form a critical part in all three TF FDUs (Fast Discharge Units). Each set will extract 684 MJ, at a nominal current of 42.5 kA while clamping at 5.1 kV.

Metrosil engineers have been working closely with OCEM Energy Technology (Bologna) who are providing the power electronics and systems integration for the Metrosil High Energy varistor protection system.

“We are thrilled to be working alongside OCEM in providing the DTT consortium with an energy extraction solution” says Dominic Coll, Commercial Manager for Metrosil. “Our varistors are proven to extract energy up to three times faster than a linear dump resistor, our work with CERN and KEK proves this. Metrosil protects superconducting magnets and provides cost savings as less energy is deposited within the cryostat. A reduction in hot spots prevents helium escaping and minimises the need for cooling power after a quench.”

Alessandro Lampasi, responsible for the Coil Power Supply Team of the Divertor Tokamak Test (DTT) facility, including members from 11 research and industry partners, specified SiC varistors into the DTT project. Alessandro states, “I became aware of Metrosil due to their ongoing work with CERN and realised their potential in assisting us with an energy extraction solution. Tokamak coils require protection systems to extract stored magnetic energy without damaging the power supply circuit. This is especially critical in superconducting coils, due to quench phenomena. Fast discharge units (FDUs) are necessary for protection, which can be inserted into the coil circuit. The results achieved by CERN demonstrated the suitability of Metrosil in this regard.”