| Due to the good neutronics,thermal hydraulics and safety characteristics of lead-based coolants,Lead-based Nuclear Energy Systems(LNESs)have generated great interest in the research field of international advanced nuclear energy systems,including the lead and lead-bismuth cooled fission reactors and the Lithium Lead(LiPb)cooled fusion reactors.Based on the high boiling point characteristics of the lead-based coolant,the core outlet temperature of the LNESs can reach above 500?.Therefore,the LNESs have the potential to achieve high power generation efficiency.Recently,the power generation system based on lead and lead-bismuth cooled fission reactors and LiPb cooled fusion reactors have performance in the range of?40%and?46%,respectively.Under the same core outlet temperature condition,improving the power generation efficiency by optimizing the scheme and parameters of the power generation system is of excessive significance for improving the economics of LNESs.The conceptual design and optimization of the steam Rankine power generation system of Lead-cooled Fast Reactor(LFR)and the Helium-gas(He-gas)cooled Brayton power generation system of the LiPb cooled fusion reactor have been carried out in this workA conceptual design of power generation system with two reheaters has been proposed for a 400 MWth LFR with lead inlet and outlet temperature from the core about 400? and 500?,respectively.Three different schemes of power generation system have been design and named as Schematics ?,? and ?.The thermal efficiency of Schematic-? with two reheaters was 44.3%and higher than Schematic-? and ?;one reheater with bleed-off steam from the supply line of the first regenerator and main supply line,respectively.The thermal efficiency was influenced by the number of reheaters(with bleed-off steam at different positions).The optimized temperature of feed water at the inlet of the reactor was 360? with a flow rate of 237 kg/s,the outlet temperature of the reactor was 558?,optimized turbine pressure was 22 MPa and the condenser back pressure was 0.004 MPa,respectively.The efficiency and net power of the plant were increased with the part load.The results showed that efficiency of the plant was increased by as much as ranges from 49.5%to 52.3%at the optimized parameters of the power generation system of LFRThe design of the Steam Generator(SG)utilizes the Bayonet-tube based technology with steel T91 as a structural material for the LFR.The heat extraction capacity of single SG is 50 MW and the total number of tubes is 510.The temperature of steam at the outlet is increased by 16?,the efficiency of the plant is increased by 1%and the power generated by the plant is increased by?6-7 MW for the increase of feed water temperature 5? each time,ranges between 335? and 356?.The heat transfer is increased about 8 MWth for the every increase in mass flow rate 5 kg/s of feed water.A modified design of the power generation system with concept of two-stage expansions named Schematic-?,which work on the bases of He-gas cooled Brayton cycle has been proposed for the Dual-coolant LiPb(DLL)blanket of FDS-II to increase the power generation efficiency of the system than the previous design.Total extraction of the blanket was 21 MW,He-gas temperature and pressure at the exit of intermediate heat exchanger was 680? and 8 MPa.The engineering equation solver tool was used to calculate the performance of the system.More than one expansion stage is very effective as compared with either splitting the flow equally for the expansion in two turbines or a single-stage expansion.The thermal efficiency of the Schematic-? was 51%,which was 4%higher than the previous designs.The optimum pressure ratio was 3.41 to obtain the maximum thermal efficiency of 65.3%.An intermediate heat exchanger with a corrugation structure has been proposed to increase the power generation efficiency and the safety of fusion reactor system.The corrugated structure of Compact Heat Exchanger(CHE)with SiCf/SiC composite has higher 11.4%heat transfer rate as compared to that with ODS steel.According to the design parameters of the DLL,corrugated structure of the CHE increased the effectiveness and overall heat transfer coefficient up to 19.8%and 25.1%at the LiPb velocity of 0.099 m/s and increased up to 26.2%and 33.0%,when the velocity of LiPb was decreased to 0.012 m/s as compared to that of flat structure of compact heat exchanger.An efficient and reliable experimental setup of the power generation system for LNES can be developed based on this study.The optimum number of reheaters for Rankine cycle and number of expansion stages for the Brayton cycle should be considered properly to increase the performance of the system.The parameters of the power generation system can be optimized by using this study as a reference. |
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