Order-of-Magnitude Increase in Tritium Burn Efficiency with Low-Tritium Spin-Polarized Fuel

Spin-polarized deuterium-tritium (D-T) fuel [1] with more D than T [2] increases tritium burn efficiency (TBE) [3] by at least an order of magnitude without compromising fusion power output, compared to unpolarized fuel [4]. Although previous studies show that low tritium fraction enhances TBE [2], this also reduced fusion power. A study is performed for an ARC-like tokamak producing 482 MW of fusion power with unpolarized 51:49 D-T fuel, finding the minimum startup tritium inventory (I_startup) is 0.69 kg. By spin-polarizing half (all) of the fuel and using a 57:43 (61:39) D-T mix, I_startup is reduced to 0.08 (0.03) kg. TBE values of roughly 10-40% could be achieved using low-tritium-fraction and spin-polarized fuel with minimal power loss, lowering tritium startup inventory requirements and reducing on-site tritium. More generally than just for spin-polarized fuels, high plasma performance can increase TBE. This motivates spin-polarized fuels for burning plasmas.

 

[1] Kulsrud, R. M. et al. "Physics of spin-polarized plasmas." Nuclear fusion 26, no. 11 (1986): 1443.

[2] Boozer, Allen H. "The tritium burn-fraction in DT fusion." arXiv preprint arXiv:2106.01304 (2021).

[3] Whyte, D.G. et al, 2023. Tritium burn efficiency in deuterium–tritium magnetic fusion. Nuclear Fusion, 63(12), p.126019.

[4] Parisi, J. F. et al "Simultaneous Enhancement of Tritium Burn Efficiency and Fusion Power with Low-Tritium Spin-Polarized Fuel." arXiv preprint arXiv:2406.05970 (2024).