Liquid tin could cool down fusion reactors

The discovery has led the research team to develop a liquid metal tin divertor, which is an advanced heat-removal component of fusion reactors.

The process is possible due to the chemical compatibility between high-temperature liquid metal tin (Sn) and reduced activation ferritic martensitic, a candidate structural material for fusion reactors. 

Fusion is a potential source of almost limitless clean energy but is currently only carried out in experiments as it has proved difficult to harness. However, there are hopes that it could become a safe and clean alternative source of energy in the not-too-distant future.

Divertors are fundamental components of fusion reactors, as they are used to gasify impurities in the plasma and send the gas to an exhaust pump. Usually, divertors are solid, made of a block of metal. 

During the operation of a fusion reactor, some of the structural components of the divertor are exposed to extremely large heat loads – at the same level as the space shuttle when entering the atmosphere. This means that the material used for the construction of solid divertors needs to be heat-resistant. 

However, researchers have recently considered the concept of a liquid metal divertor which protects the divertor from plasma by covering its structural material with a liquid metal that possesses excellent cooling performance, such as tin. 

Tin's vapour pressure at high temperatures is lower than that of other liquid metals, which means it is difficult to evaporate even if it is heated by plasma and reaches a high temperature. It also possesses the advantage of the evaporated metal being less likely to mix with the plasma.

However, the corrosion of structural materials is a technical issue that has concerned some researchers.

 “Although liquid metal tin is an excellent coolant with a variety of properties, it has the drawback of corroding structural materials. By clarifying the corrosion mechanism, we hope to promote the use of liquid metal tin not only for fusion energy but also for solar thermal power plants,” said Associate Professor Masatoshi Kondo of the Tokyo Institute of Technology. 

The team's findings, published in the journal Corrosion Science, aim to advance the study of corrosion of liquid metal tin to assist in the development of highly reliable advanced heat-receiving equipment for fusion reactors.

Earlier this week, the fusion industry witnessed a major breakthrough as scientists were able to produce more energy than was consumed during a fusion energy reaction. 

In addition to the construction of the tokamak (ITER), in collaboration with seven of the world's leading countries and regions (Japan, EU, United States, South Korea, China, Russia, and India), fusion development by the private sector is also accelerating.

In the last 12 months, funding for commercial fusion projects has more than doubled, with fusion companies raising more than $2.83bn (£2.39bn) in funding, an increase of 139 per cent from 2021, according to a recently published report by the Fusion Industry Association.