MANTA: A Negative-Triangularity NASEM-compliant fusion pilot plant

Abstract

The MANTA (Modular Adjustable Negative Triangularity ARC-class) design study investigated how negative-triangularity (NT) may be leveraged in a compact, fusion pilot plant (FPP) to take a "power-handling first" approach. The result is a pulsed, radiative, ELM-free tokamak that satisfies and exceeds the FPP requirements described in the 2021 National Academies of Sciences, Engineering, and Medicine report "Bringing Fusion to the U.S. Grid"[1]. A self-consistent integrated modeling workflow predicts a fusion power of 450 MW and a plasma gain of 11.5 with only 23.5 MW of power to the scrape-off layer (SOL). This low PSOL together with impurity seeding and high density at the separatrix results in a peak heat flux of just 2.8 MW/m2. MANTA's high aspect ratio provides space for a large central solenoid (CS), resulting in ~15 minute inductive pulses. In spite of the high B fields on the CS and the other REBCO-based magnets, the electromagnetic stresses remain below structural and critical current density limits. Iterative optimization of neutron shielding and tritium breeding blanket yield tritium self-sufficiency with a breeding ratio of 1.15, a blanket power multiplication factor of 1.11, toroidal field coil lifetimes of 3100 ± 400 MW-yr, and poloidal field coil lifetimes of at least 890 ± 40 MW-yr. Following balance of plant modeling, MANTA is projected to generate 90 MW of net electricity at an engineering fusion gain of ~2.4. Systems-level economic analysis estimates an overnight cost of US$3.4 billion, meeting the NASEM FPP requirement that this first-of-a-kind be less than US$5 billion. The toroidal field coil cost and replacement time are the most critical upfront and lifetime cost drivers, respectively.