A helium-cooled blanket design of the low aspect ratio reactor

An aggressive low aspect ratio scoping fusion reactor design (C.P.C. Wong, R. Cerbone, E.T. Cheng, R.L. Miller, R.D. Stambaugh, Proc. of 17th IEEE/NPS S Symp. on Fusion Engineering, pp. 1053) indicated that a 2 GW(e) reactor c an have a major radius as small as 2.9 In resulting in a device with compet itive cost of electricity at 49 mill/kWh. One of the technology requirement s of this design is a high performance high power density first wall and bl anket system. A 15 MPa helium-cooled, V-alloy and stagnant LiPb breeder fir st wall and blanket design was utilized. Due to the low solubility of triti um in LiPb, there is the concern of tritium migration and the formation of V-hydride. To address these issues, a lithium breeder system with high solu bility of tritium has been evaluated. Due to the reduction of blanket energ y multiplication to 1.2, to maintain a plant Q of > 4, the major radius of the reactor has to be increased to 3.05 m. The inlet helium coolant tempera ture is raised to 430 degreesC in order to meet the minimum V-alloy tempera ture limit everywhere in the first wall and blanket system. To enhance the first wall heat transfer, a swirl tape coolant channel design is used. The corresponding increase in friction factor is also taken into consideration. To reduce the coolant system pressure drop, the helium pressure is increas ed from 15 to 18 MPa. Thermal structural analysis is performed for a simple tube design. With an inside tube diameter of 1 cm and a wall thickness of 1.5 mm, the lithium breeder can remove an average heat Aux and neutron wall loading of 2 and 8 MW/m(2), respectively. This reference design can meet a ll the temperature and material structural design limits, as well as the co olant velocity limits. Maintaining an outlet coolant temperature of 650 deg reesC, one call expect a gross closed cycle gas turbine thermal efficiency of 45%. This study further supports the use of helium coolant for high powe r density reactor design. When used with the low aspect ratio reactor conce pt a competitive fusion reactor can be projected at 51.9 mill/kWh. (C) 2000 Elsevier Science S.A. All rights reserved.