MoltexFLEX scientists publish new graphite research

Warrington, UK (6th February 2024) – A team of scientists working for British advanced nuclear technology developer MoltexFLEX has published new research on how graphite interacts with the molten salt used in the company’s revolutionary FLEX reactor.

The team, working together with scientists at the University of Manchester’s Nuclear Graphite Research Group (NGRG), used X-ray micro CT scanners to investigate how tiny amounts of molten salt infiltrated pores within standard industrial grades of graphite – the first time such scanning has been used for this purpose.

Graphite is a vital component of the FLEX reactor and many other nuclear reactor designs as it is used to moderate the behaviour of neutrons and control the fission process. MoltexFLEX is aiming to use commercially available grades of graphite as part of the company’s ethos of using ‘off-the-shelf’ materials. This will make it easier to mass produce FLEX reactors while keeping costs low.

The research, which was conducted at MoltexFLEX’s Warrington laboratory and the University of Manchester, involved exposing samples of graphite to the molten salt coolant used in the FLEX design. The samples were immersed in the salt within sealed stainless steel containers for 30 days at temperatures above 750°C – the operating temperature of the FLEX reactor.

“The results were very much as we predicted,” said MoltexFLEX Senior Metallurgist Dr Ciara Fox, who was part of the research team. “This research is a very promising first stage on the path to predicting and controlling the behaviour of molten salt infiltration within the graphite. It’s an important stepping stone in developing a technique that will allow us to do that.”

MoltexFLEX has been working in partnership with the NGRG on graphite-related research for more than three years. The NGRG team, led by Professor Abbie Jones, has a huge amount of expertise in graphite research and is internationally recognised in this field.

“We have very much enjoyed working with the NGRG on this project and look forward to working with them again in the future,” Dr Fox added.

The research paper, which is open access, is published in the journal Materialia and can be viewed here:

The work described in the paper was undertaken with the help of a grant from the Henry Royce Institute of Advanced Materials (Royce). The award is part of the Industrial Collaboration Programme (ICP), a Royce initiative that seeks to boost research, development and innovation activities across the UK. 

Study citation:

Xun Zhang, Alex Theodosiou, William Bodel, Phil Quayle, Ciara Fox, Chris Hankinson, Chris Morgans, Abbie N. Jones: “Tracking the infiltration of molten salt into graphite using time-lapse X-ray micro-computed tomography”. Materialia, Volume 33, 2024,
102016, ISSN 2589-1529, (

Image caption: images (a) and (c) show 2D virtual slices of a sample of graphite before (a) and after (c) exposure to molten salt at temperatures of over 750°C. Images (b) and (d) show 3D sections of the region highlighted by the yellow rectangle in (a) and (c). Image (b) shows the structure of pores within the graphite sample, and image (d) shows pores containing salt after exposure highlighted in red. The purple area is the large void visible within the highlighted area in (a) and (c). (Image copyright MoltexFLEX)

About MoltexFLEX     
MoltexFLEX, a subsidiary of Moltex Energy Limited, is based in Warrington, UK. It is developing the FLEX molten salt reactor – an advanced small modular design which together with the GridReserve® molten salt thermal energy storage system delivers clean, flexible, and low-cost electricity and high-temperature heat. MoltexFLEX plans to have the first FLEX reactor operational around the turn of the decade. For more information, visit

Media inquiries:   
Rob Loveday   
Communications Officer, MoltexFLEX   
+44 1925 974760 / +44 7815 866313    

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