Nuclear technology considerations and neutronics for the ST-E1 fusion power plant
- 1Tokamak Energy Ltd
- 2Oak Ridge National Laboratory
Abstract
This paper presents Tokamak Energy’s pre-concept design of ST-E1, a low aspect ratio tokamak fusion reactor. Efficacy of radiation shielding in protecting the high temperature superconducting magnets systems is a major driver dictating tokamak size, plant lifetime, and balance of plant. It is crucial that neutronics and material considerations are incorporated into plant design from the earliest design stages and comprehensively taken into account across all areas through the systems engineering framework. At Tokamak Energy, a dedicated workflow for plant-scale neutronics simulations has been developed using G4Tokamak, an in-house application based on the Geant4 toolkit. This workflow enabled faster and more efficient design iterations, and its results were verified through benchmarking against MCNP. A four-part shielding architecture, comprising of the centre column, vacuum vessel, outboard horizontal and vertical elements, was designed to balance neutronics performance, thermal management, structural demands, and cost. The shielding system, at this pre-concept stage, demonstrates the feasibility of limiting the neutron flux to the magnet systems to support a full power life of 30 years, and limiting the nuclear heating of the cold mass within cryogenic cooling capacity. Activation studies highlight maintenance and long-term waste management challenges, with non-reduced activation ferritic martensitic steels and plasma facing components showing the highest activation. Collectively, these results establish a comprehensive neutronics and materials framework, baseline core shielding design for ST-E1, and demonstrate its readiness for progression to detailed concept development.
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BibTeX
@article{chandrasekhar2026nuclear,
title = {{Nuclear technology considerations and neutronics for the ST-E1 fusion power plant}},
author = {K. Chandrasekhar and C.L. Wilson and Samara M. Levine and Sandeep Irukuvarghula and V. Godhani and Jonathan David Naish and Ariel Márquez and Michael J. Loughlin},
journal = {Nuclear Fusion},
year = {2026},
month = jul,
doi = {10.1088/1741-4326/ae63e2},
url = {https://doi.org/10.1088/1741-4326/ae63e2},
note = {CC BY},
}
RIS
TY - JOUR
TI - Nuclear technology considerations and neutronics for the ST-E1 fusion power plant
AU - K. Chandrasekhar
AU - C.L. Wilson
AU - Samara M. Levine
AU - Sandeep Irukuvarghula
AU - V. Godhani
AU - Jonathan David Naish
AU - Ariel Márquez
AU - Michael J. Loughlin
PY - 2026
DA - 2026/07/10
JO - Nuclear Fusion
DO - 10.1088/1741-4326/ae63e2
UR - https://doi.org/10.1088/1741-4326/ae63e2
AB - This paper presents Tokamak Energy’s pre-concept design of ST-E1, a low aspect ratio tokamak fusion reactor. Efficacy of radiation shielding in protecting the high temperature superconducting magnets systems is a major driver dictating tokamak size, plant lifetime, and balance of plant. It is crucial that neutronics and material considerations are incorporated into plant design from the earliest design stages and comprehensively taken into account across all areas through the systems engineering framework. At Tokamak Energy, a dedicated workflow for plant-scale neutronics simulations has been developed using G4Tokamak, an in-house application based on the Geant4 toolkit. This workflow enabled faster and more efficient design iterations, and its results were verified through benchmarking against MCNP. A four-part shielding architecture, comprising of the centre column, vacuum vessel, outboard horizontal and vertical elements, was designed to balance neutronics performance, thermal management, structural demands, and cost. The shielding system, at this pre-concept stage, demonstrates the feasibility of limiting the neutron flux to the magnet systems to support a full power life of 30 years, and limiting the nuclear heating of the cold mass within cryogenic cooling capacity. Activation studies highlight maintenance and long-term waste management challenges, with non-reduced activation ferritic martensitic steels and plasma facing components showing the highest activation. Collectively, these results establish a comprehensive neutronics and materials framework, baseline core shielding design for ST-E1, and demonstrate its readiness for progression to detailed concept development.
SN - 0029-5515
SN - 1741-4326
ER -