Two-phase MHD energy conversion from buoyancy-driven flows of liquid metal coolant in a fusion reactor

Charles E. Wood*, Chris J. Lawn

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


The present consensus for generating electrical power from a tokamak is to use a well-established energy conversion method: the conversion of heat to electricity through gas or steam turbines. The objective of our research has been to compare alternative methods of conversion. This has culminated in a proposal that utilises two-phase liquid metal magnetohydrodynamic (TPLMMHD) energy conversion in a topping cycle. The resulting power cycle configuration, with the current design specifications for a dual-cooled lithium-lead (DCLL) blanket, involves a high-pressure Brayton cycle that takes helium directly from the blanket, utilises TPLMMHD topping, and includes three low-pressure low-temperature Rankine bottoming cycles. Several studies have been undertaken, including limited small-scale experimental work, and a computer model developed to predict a power output of 22 MWe via TPLMMHD with the circulation of Pb-17Li through a DCLL blanket by buoyancy. This removes the need to pump Pb-17Li and saves an additional 6.3 MWe However, far greater gains than this 28 MWe can come from an increase in the helium pressure in the gas turbines from 8 MPa to 34.5 MPa. The net electric power output for a PPCS model-C plant including our proposal for higher helium pressures is increased from 1480 MWe to 1909 MWe, which yields an increase in overall plant efficiency from 43.4% to 56%. This sensitivity to helium pressures is an important subsidiary outcome of the study.

Original languageEnglish
Article number111288
Number of pages10
JournalFusion Engineering and Design
Early online date13 Nov 2019
Publication statusPublished - 1 Feb 2020


  • Brayton
  • Buoyancy
  • Lithium-lead
  • MHD
  • Topping cycle
  • Two-phase

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