Advantages of DT operation in the compact, high-field tokamaks

The proposed SPARC device is a compact (R ~ 1.6 m), high-field (B ~ 12 T) tokamak designed to achieve Q > 2 and demonstrate fusion break-even with a high power output ~100 MW. In order to achieve this mission, SPARC will conduct deuterium-tritium plasma operations, becoming the third tokamak (after JET and TFTR) to operate with tritium fuel. SPARC’s small size leads to a relatively short current relaxation time, which enables the physics equilibrium of net-gain plasmas in short (~10 s) pulses. Such short pulses reduce by orders of magnitude two critical operational challenges: the total neutron fluence to device components and the on-site and in-vessel tritium inventories. In particular, the significantly reduced tritium inventories predicted for SPARC (~10g) are on par with JET and TFTR during their tritium phases. Thus, SPARC intentionally by design takes advantage of the large body of knowledge generated during the operation of both devices, placing SPARC much closer in terms of nuclear challenges to previous DT fusion devices and providing demonstrated and relevant precedents in permitting, device operations, nuclear systems, health physics and safety, and decommissioning and disposal.