Molten-Salt Fusion Liquid-Immersion-Blanket Integrated Validation Plan

Report Date: 

March 2021




This report is an integrated validation plan for the development of a flibe (Li2BeF4) fusion blanket for a high-magnetic-field fusion machine such as the Affordable Reliable Compact (ARC) fusion system. The goal is to define what is missing to enable the engineering design of a flibe fusion blanket. Advances in magnet technology enable doubling the magnetic fields in magnetic fusion machines. The size of such machines varies as one over the fourth power of the magnetic field for any given power output. That is, doubling the magnetic field reduces the size of the fusion machine by more than a factor of ten for the same power output. This has a massive beneficial effect on fusion economics; but, it implies that the power density in the blanket increases by an order of magnitude creating new challenges in blanket design.

The fusion blanket has four functions: (1) convert the energy of 14-Mev neutrons into heat for the power cycle, (2) breed sufficient tritium to fuel the fusion machine, (3) provide radiation shielding of the magnets and (4) provide cooling for the first wall that separates the plasma from the blanket. Many blanket designs have been proposed. All incorporate lithium that absorbs neutrons and is converted into tritium and helium. Most blanket designs use solids with cooling provided by water, helium or other coolant. The massive increase in the power density of the ARC fusion blanket enabled by higher magnetic fields makes it difficult to cool solid blankets. There is an alternative, a blanket of liquid flibe salt to avoid most of the cooling challenges. It also enables reduction of the tritium inventory in the blanket that reduces the tritium accident source term; that, in turn, reduces the cost of safety systems required for the plant. There has been limited work on flibe blankets. The development of high-magnetic-field fusion systems may now make such blankets the preferred fusion blanket option.

In its simplest form, the blanket is a tank of flibe salt about a meter thick on all sides of the plasma—sufficient thickness to convert neutrons into tritium, convert the energy of 14-Mev neutrons into heat and shield the magnets. The inner wall of the tank is also the vacuum wall separating the plasma from the blanket. Cold salt is added to the tank and hot salt is sent to the power cycle. The inner wall of the flibe blanket faces the plasma and is cooled by the flibe salt. There are channels near the wall for the flibe salt to enhance cooling of the inner wall.


  • NES

    Nuclear Energy and Sustainability


  • TR

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