MoltexFLEX turns up the power on FLEX reactor development

Warrington, UK (11th September 2023) – Advanced nuclear energy developer MoltexFLEX has reached a watershed in the development of its small modular FLEX reactor that will see the UK-based company move to the next level, from the pre-concept science phase into accelerated product and project delivery.

In doing so, the company will expand its operations and has significantly refined the design of the innovative FLEX molten salt reactor – delivering a 50% boost in power output, while maintaining previous targets for overnight capital cost and cost per MWh.

Despite the recent increases in commodity prices around the world, the FLEX reactor is still able to generate electricity for less than £30/MWh when used as a source of baseload power.

“We have firmly established the core aspects of the FLEX concept as we ramp up engineering design,” said MoltexFLEX Head of Engineering Chris Hankinson. “More work will be undertaken over the coming months to further refine and finally freeze the design, and this will then be taken forward to create our first-of-a-kind reactor.”

While the underlying technology of MoltexFLEX’s passively safe reactor remains essentially unchanged, these design evolutions represent significant improvements. The work provides more certainty about the company’s ability to deliver on its cost targets, reinforces the underpinning science, and sets MoltexFLEX on the road toward delivering its prototype FLEX reactor around the turn of the decade.  

The main changes to the FLEX design include an increase in power output from 40MWth/16MWe as originally envisaged to 60MWth/24MWe, made possible by optimisation of the core design and the fuel pin material.

The refuelling schedule has also been adjusted to account for the fact that the FLEX reactor will now use 5% low-enriched uranium (LEU) instead of 6% LEU. This change will increase the reactor’s global deployability and harness the existing fuel supply chain.

“The science and engineering of the FLEX reactor has moved on apace,” said MoltexFLEX CEO David Landon. “The work we have completed further boosts our confidence in the design and economics of the FLEX reactor, and our ability to deliver a first reactor ready for global roll-out through the 2030s.”

More detailed technical information about how the FLEX reactor’s design has evolved can be found at

About MoltexFLEX 

MoltexFLEX is a subsidiary of Moltex Energy Limited, with its headquarters in Warrington, UK. It has developed the FLEX reactor – an advanced nuclear reactor which delivers clean, low-cost and reliable energy that complements renewables such as wind and solar. MoltexFLEX plans to have its first reactor operational by 2029. For more information, visit

Media inquiries:
Rob Loveday
Communications officer
+44 7815 866313

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