THE TITAN-I REVERSED-FIELD-PINCH FUSION-POWER-CORE DESIGN

The TITAN reversed-field-pinch (RFP) fusion-reactor study has two obje ctives: to determine the technical feasibility and key developmental i ssues for an RFP fusion reactor operating at high power density; and t o determine the potential economic operational, safety, and environmen tal features of high mass-power-density (MPD) fusion-reactor systems. Parametric system studies have been used to find cost-optimized design s. The design window for compact RFP reactors includes the range of 10 -20 MW/m2. The reactors are physically small, and a potential benefit of this ''compactness'' is improved economics. The TITAN study adopted 18 MW/m2 in order to assess the technical feasibility and physics lim its for such high-MPD reactors. The TITAN-I design is a lithium self-c ooled design with a vanadium-alloy (V-3Ti-1Si) structural material. Th e magnetic field topology of the RFP is favorable for liquid-metal coo ling. The first wall and blanket consist of single pass poloidal-flow loops aligned with the dominant poloidal magnetic field. A unique feat ure of the TITAN-1 design is the use of the integrated-blanket-coil (I BC) concept. The lithium coolant in the blanket circuit is also used a s the electrical conductor of the toroidal-field and divertor coils. A ''single-piece'' FPC maintenance procedure is used, in which the firs t wall and blanket are removed and replaced by vertical lift of the co mponents as a single unit. This unique approach permits the complete F PC to be made of a few factory-fabricated pieces, assembled on site in to a single torus, and tested to full operational conditions before in stallation in the reactor vault. A low-activation, low-afterheat vanad ium alloy is used as the structural material throughout the FPC in ord er to minimize the peak temperature during accidents and to permit nea r-surface disposal of waste. The safety analysis indicates that the li quid-metal-cooled TITAN-I design can be classified as passively safe, without reliance on any active safety systems. The results from the TI TAN study support the technical feasibility, economic incentive, and o perational attractiveness of compact, high-MPD RFP reactors. Many crit ical issues remain to be resolved, however. The physics of confinement scaling, plasma transport and the role of the conducting shell are al ready major efforts in RFP research. However, the TITAN study points t o three other major issues. First, operating high-power-density fusion reactors with intensely radiating plasmas is crucial. Second, the phy sics of toroidal-field divertors in RFPs must be examined. Third curre nt drive by magnetic-helicity injection must be verified. The key engi neering issues for the TITAN I FPC have also been defined. Future rese arch and development will be required to meet the physics and technolo gy requirements that are necessary for the realization of the signific ant potential economic and operational benefits that are possible with TITAN-like RFP reactors.