Liquid bismuth loop

The General Electric G-3 ac pump was calibrated (Figs. 2.3-3 and 23-4) in another AISI type-347 stainless steel liquid bismuth loop at 930°F [22], It was operated continuously for over 13,000 hr. 

The loop may be drained into a vessel which can be either the fill tank or a separate drain tank. Piping lines should be sloped to facilitate drainage undrainable pockets should be provided with separate drain lines or, if possible, eliminated. A typical liquid-bismuth loop layout is shown in Fig. 23-6. 

Most fast-spectrum reactors operated around the world use liquid sodium metal as a coolant. Future fast-spectrum reactors may use lead or a lead-bismuth alloy, or even helium, as a coolant. One of the attractive properties of metals as coolants is that they offer exceptional heat-transfer properties in addition, some (but not all) metal coolants are much less corrosive than water. However, because sodium is reactive with air and water, fast-spectrum reactors built to date have a secondary sodium system to isolate the sodium coolant in the reactor from the water in the electricity-producing steam system. The need for a secondary system has raised capital costs for fast reactors and has limited thermal efficiencies to the range of 32 to 38 percent. Novel steam-generator designs, direct gas cycles, and different coolants are options that may eliminate the need for this secondary sodium loop and improve the economics of fast reactors (Lake et al 2002). 

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