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MMR™ nuclear plant.

Reactor Core

Predictable Power

The reactor core consists of hexagonal graphite blocks containing stacks of FCM™ fuel pellets. The MMR™ reactor core has a low power density and a high heat capacity resulting in very slow and predictable temperature changes. The MMR™ reactor is fueled once for its lifetime.

Helium Coolant

The Most Benign Cooling Medium Available

Helium gas is the MMR™ reactor’s primary coolant. The helium passes through the nuclear core and is heated by the controlled nuclear fission process. The helium then transports the heat away from the core to the Molten Salt System.

The MMR™ reactor uses helium as it is an inert gas; a radiologically transparent, single-phase gas with no flashing or boiling possible. Helium does not react chemically with the fuel or reactor core components. It is easy to accurately measure and control the helium pressure in the reactor.

The FCM™ fuel ensures the helium is clean and free of fission products.

Molten Salt Loop

Intermediate Heat Transfer Loop

The MMR™ plant is simple to operate, and flexible in its outputs. The use of molten salt thermal storage allows for significant flexibility in the supply of both electricity and process heat.

Power Density

1.24 W/cm3

Outlet Temp

630 °C




20 years



The MMR™ energy system consists of two plants, the nuclear plant and the adjacent power plant. The nuclear plant contains the MMR™ reactors including all the equipment required to transport the heat to the adjacent plant. The adjacent power plant contains the equipment that converts heat to electricity or process heat as required.

Simple Operations

Operations are simple with minimal operations and maintenance requirements, and no on-site fuel storage, handling, or processing.

No Active Safety Systems

The plant has no need for active systems to remove heat. Additionally, the plant does not need any outside services, including electrical power, to operate safely.

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The MMR™ facility uses standardized modules. The modules will be assembled, commissioned and tested off-site at our factory.

Easy to Transport

The modules will be sized for standard International Standards Organization shipping containers; this means they can be transported easily by ship, rail or road.

Quick to Build

The modules are transported to the site, and then assembled. The construction of the MMR™ plant is quick, simple, and scalable.

Scalable and Adaptable

Multiple MMR™ reactors can be linked together to provide between 5 and 50 MW of electricity, up to 150 MW of heat, or a combination of the two. The modules can also be combined in different ways for different sites and needs.


Total Non-Proliferation

FCM™ fuel cannot be re-processed, it can only be used to generate heat. FCM™ fuel reactions cannot grow or be forced out of control – FCM™ fuel is secure.

Sealed Core

The MMR™ reactor is sealed for life – the fuel cannot be accessed.

Total Environmental Protection

There is no risk of spills. There are no environmental impacts during accidents. The nuclear fission products are locked in the fuel particles permanently.

Genuine Safety Margin

The fuel safety margin is so large that fission product retention is accomplished entirely by the fuel; no other containment is needed. There are no sudden temperature rises – the reactor controls and switches itself off in all accident conditions.

No External Power or Water Required

The heat generated by the core is removed passively through the natural convection of the the helium. External water and electricity are not needed to cool the reactor.


The MMR™ plant can operate as a stand-alone remote plant.