UK-based Tokamak Energy in February announced that it had built the first set of new generation high temperature superconducting (HTS) magnets to be assembled and tested in fusion power plant-relevant scenarios. The magnets are intended for use in Tokamak’s planned ST-E1 fusion pilot plant expected to demonstrate the capability of delivering electricity into the grid in the early 2030s.
In 2022, Tokamak Energy achieved a world-first by reaching a plasma temperature of 100m degrees Celsius in its ST40 spherical tokamak. This is the threshold required for commercial fusion energy and the highest temperature ever achieved in a privately funded spherical tokamak.
Although most radiation from high-energy plasma neutrons will be absorbed by the tokamak’s shielding, the magnets must be able to withstand secondary gamma rays. Tokamak Energy, therefore, built and commissioned a specialist gamma radiation cryostat system – a vacuum device to provide thermal insulation for the magnets. This test system, at Tokamak’s headquarters in Oxfordshire, will now be disassembled, shipped, and rebuilt at the Gamma Irradiation Facility (GIF) based at the US Department of Energy’s (DOE’s) Sandia National Laboratories (SNL) in Albuquerque, New Mexico.
It is one of the few places in the world capable of housing the system while exposing the HTS magnets to a power plant representative dose rates of gamma radiation.
Tokamak Energy Magnet Development Manager Dr Rod Bateman, HTS said SNL “is ideally configured to test magnet durability and performance when exposed to gamma radiation. It is essential to push the boundaries now as we scale up our operations towards commercial fusion”. Research and analysis on sets of individual magnets will run for six months at GIF, which can undertake a 60-year lifetime test in just two weeks.
GIF Facility Supervisor Don Hanson explained that GIF is a unique facility that can provide high doses of gamma radiation to large test objects. GIF provides high-fidelity simulation of nuclear radiation environments for materials and component testing. It can produce a wide range of gamma radiation environments using cobalt-60 sources. It can irradiate objects as small as electronic components or as large as an army tank. The GIF provides in-cell dry irradiations in three test cells and in-pool submerged irradiations.
