(Commonwealth) _ Moltex Energy, a UK-based nuclear power and energy storage company, has commissioned a unique rheometer to test the viscosity and density of molten salts at temperatures up to 1,000°C. The company, in partnership with scientific instruments manufacturer Anton Paar, installed the rheometer inside a climate-controlled inert gas glove box at the MoltexFLEX laboratory in Warrington, Cheshire. The innovative test rig is now operational and has started providing data.
Rheometers are devices used to measure the viscosity and density of different materials at varying temperatures. MoltexFLEX is using its new rheometer to test the fluoride salts that the company plans to use as the fuel and coolant for its novel FLEX reactor.
The FLEX reactor relies on natural convection rather than pumps to circulate the molten salt coolant, and this is sensitive to viscosity and density. Therefore, accurate information on these parameters at different temperatures is vital, said MoltexFLEX lead chemist Phil Quayle. This one-of-a-kind installation will go a long way towards delivering a FLEX reactor this decade.
There is little available information on how the kinds of fluoride salts used in the FLEX reactor behave at high temperatures. Few companies and research institutions have investigated their density and viscosity, as this data is difficult to gather reliably. The salt can easily become contaminated by oxygen and water, which affects its material properties. Installing the rheometer inside the glove box, which is filled with pure nitrogen gas, solves this problem and enables MoltexFLEX’s scientists to obtain accurate results. The team has calibrated the rheometer with lower-temperature chloride salts and is now generating viscosity data for the FLEX salts.
Bringing the rheometer capability in-house is a huge step forward in MoltexFLEX’s analytical capability. It enables them to “try fast and learn fast”. They can rapidly develop experimental protocols and generate good data sooner, according to Quayle.
The team from Anton Paar has been fantastically supportive in making this installation possible, said MoltexFLEX research chemist Dr James Moffat, who led the rheometer commissioning process.
As far as MoltexFLEX and Anton Paar know, no-one in the UK has installed a high-temperature rheometer inside a climate-controlled environment like this, believes chemist Beth Mapley, who is developing procedures for use with surrogate uranium fluoride fuel salt.
The FLEX reactor is a revolutionary design that aims to provide safe, clean, and cost-effective nuclear power. It uses a molten salt fuel that is already in a liquid state, meaning it cannot melt down in the same way as traditional solid fuel. The fuel is also contained within a tank that can withstand the highest temperatures, making it virtually leak-proof.
The FLEX reactor also has a unique cooling system that relies on natural convection rather than pumps, making it simpler and safer than traditional designs. The coolant, a fluoride salt mixture, absorbs the heat generated by the nuclear reaction and rises naturally due to its lower density, where it is then cooled in a heat exchanger and returns to the reactor to repeat the cycle.
MoltexFLEX’s innovative design has garnered interest from around the world, with the company securing funding from several sources, including the UK government’s Advanced Modular Reactor program. The company aims to have a demonstration reactor operational by the early 2030s, with full-scale commercial deployment soon after.
The commissioning of the rheometer is a significant step towards achieving that goal. The ability to measure the viscosity and density of the fuel and coolant accurately is essential to ensure the reactor’s safe and efficient operation. The rheometer will also allow MoltexFLEX to explore different fuel and coolant mixtures and their properties, providing valuable information.
