Natrium employs hot, liquid sodium as a coolant, and dispenses with the moderator entirely.This is another idea that dates back to the 1950s, but one which has never been widely deployed.Yet sodium offers several advantages as a coolant, says Chris Levesque, TerraPower's boss.The liquid sodium's high temperature―around 500°C― makes the reactor more efficient.At the same time, liquid sodium is much less corrosive to pipes than hot water.And though the water in LWRS is pumped through at high pressure, Natrium is designed to operate at close to atmospheric pressure.That means pipes, containment buildings and the like can be less beefy without affecting safety.TerraPower reckons its reactor needs only 20% of the concrete required by an LWR of equivalent power, which helps keep down costs.The firm's second big idea is its moltensalt energy-storage system. Inspiration for this came from the solar-power industry, says Mr Levesque.Solar-thermal systems (in contradistinction to the more familiar photovoltaic ones that generate electricity directly) have, for several years, used similar tanks to store excess solar energy harvested during the day.
