Could High H98-Factor Commercial Tokamak Power Plants Use Nb–Ti Toroidal Field Coils? [dataset]

In large engineering applications, materials that can fail by brittle fracture are avoided if there are practical, ductile alterna-tives. In recent years, advances in the experimental control and shaping of fusion energy plasmas have produced confinement times that are longer than the accepted IPB98(y,2) values (i.e. higher H98-factors). Detailed understanding of these enhancements in H98-factor is not available, but values as large as 1.5 - 1.8 may be possible [1, 2]. If such high values are reliably realized, they will enable such a large reduction in the magnetic field required from the toroidal field (TF) coils that ductile Nb-Ti be-comes a possible superconducting materials choice for TF fusion energy magnets. In this paper we investigate what values of enhanced H98-factor are required to enable the commercial use of Nb-Ti TF coils in tokamaks. We have investigated the use of Nb-Ti TF coils in an ITER-like geometry, for a 500 MW net electricity producing tokamak using the PROCESS systems code [3, 4]. If we use present day Nb-Ti conductors, the minimum H98-factor required for practical power plants is 1.5. For Nb-Ti cable with a critical current density in-creased by a factor of five, the minimum falls to H98 ≈ 1.4. With this improvement for an H98 = 1.5, aspect ratio 3.1 (i.e. ITER-like geometry) tokamak, we find the cost of base-load electricity is ~ 42 % greater than if Nb3Sn is used and about 1.4 times that of a typical fission power strike price (scaled up to 2.5 GWe net electricity).

在大型工程应用中，若存在实用的韧性替代材料，则会避免使用可能发生脆性断裂的材料。近年来，聚变能等离子体实验控制与成形技术的进步使得约束时间超过了公认的IPB98(y,2)值（即更高的H98因子（H98-factors））。目前对H98因子增强的详细机制尚不清楚，但可能达到1.5-1.8的数值[1,2]。若能可靠实现如此高的数值，则可大幅降低环向场（TF）线圈所需的磁场强度，从而使韧性铌钛（Nb-Ti）成为聚变能TF磁体的潜在超导材料选择。本文研究了要实现铌钛TF线圈在托卡马克中的商业应用，需要达到何种增强的H98因子值。我们利用PROCESS系统代码[3,4]，针对一座净发电量为500兆瓦的托卡马克，研究了在类ITER几何结构中使用铌钛TF线圈的情况。若使用当前的铌钛导体，实用电站所需的最低H98因子为1.5。对于临界电流密度提高5倍的铌钛电缆，该最小值降至H98≈1.4。对于H98=1.5、径宽比3.1（即类ITER几何结构）的托卡马克，经此改进后我们发现，其基荷电力成本比使用铌三锡（Nb3Sn）时高约42%，约为典型裂变发电平准化成本（fission power strike price）的1.4倍（按净发电量2.5吉瓦换算）。