An optimum rankine power cycle for the lithium-cooled TITAN-I reversed-field-pinch reactor

A thermal power cycle for the TITAN-I fusion reactor is presented. TITAN is a compact, high-power-density (neutron Wall loading of 18 MW/m2) reactor based on the reversed-field-pinch (RFP) confinement concept. TITAN-I incorporates a fusion power core design with liquid lithium as the coolant and breeder, and vanadium alloy (V-3Ti-1Si) as the structural material.The total thermal power of TITAN-I is 2918 MWt. Of this total thermal power, 736 MWt is removed by the first-wall coolant, 29 MWt by the divertor coolant and the remaining 2153 MWt by the blanket coolant. The inlet temperature of the primary coolant is 320 °C. The exit temperatures are 440 °C, 540 °C and 700 °C for the first-wall, divertor and blanket coolants, respectively. Coolants from the first wall and divertor are mixed upon exit which gives the first-wall/divertor mixed exit temperature of 442 °C. The blanket coolant is kept separate. The coolant flow rates in the first-wall, divertor and blanket circuits are 1464, 31 and 1352 kg/ s, respectively. Liquid lithium is also chosen as the secondary coolant in the intermediate heat exchangers. Several power cycle modifications are considered. The selected power cycle has two components — one for the conversion of the thermal power in the first-wall and divertor coolants, and the other for conversion of the thermal power in the blanket coolant which is at much higher thermal potential. The power cycle for the first wall and divertor is a non-reheat, superheat Rankine cycle with 4 stages of regenerative feed-water heating. The pressure and temperature of the throttle steam are 10.7 MPa and 396 °C, respectively. This results in a gross thermal efficiency of 37.3%. The power cycle for blanket is a Rankine cycle with 2-stage reheat and 7 stages of regenerative feed-water heating. The throttle steam conditions are 565.6 °C and 21.4 MPa. The gross thermal efficiency for this cycle is 46.5%. The overall gross thermal efficiency of the lithium-cooled TITAN reactor is 44%. All the power cycle analyses are done by the code PRESTO developed at Oak Ridge National Laboratory in the United States.