A Company Named Apollo Plans to Offer a Subcritical Fusion-Fission Nuclear Reactor – What is this?

April 6, 2017 – Nuclear reactions come in three flavours: subcritical, critical and supercritical. Current fission reactors fit the second category by definition. Mind you the critical reaction is controlled by containing the chain within a small and controlled environment. The initiation of the chain releases neutrons from the uranium atoms and these neutrons strike other atoms causing subsequent neutron releases. By placing physical control substances in the path of the chain reaction, the fission remains critical rather than becoming supercritical, a uranium bomb. In subcritical nuclear fission, only a limited number of neutrons during fission contribute to the chain with many of them escaping. On April 1, 2017, Apollo Fusion announced it was going to build a hybrid fission-fusion nuclear power plant. The company filed a patent application back in 2015 that it intends to use in creating their new energy power generating technology.

The former Vice President of Alphabet X research lab, Mike Cassidy, heads up this new Apollo project. States Cassidy, “we’re working on revolutionary hybrid reactor technology with fusion power to serve safe, clean, and affordable electricity to everyone.” On the company website, it describes the technology as “designed for zero-consequence outcomes to loss of cooling or loss of control scenarios.” In other words, no meltdowns.


Mike Cassidy, former Alphabet executive, heads up Apollo Fusion effort to build a hybrid fusion-fission nuclear power plant.


Cassidy believes a safe nuclear option needs to be part of the energy mix as the planet decarbonizes. He told Bloomberg in an interview on April 3, 2017,  “Environmentalists have struggled for a while over whether nuclear power is good or bad. I think most of the more thoughtful environmentalists now view nuclear as good. If you can find a way to do nuclear power that doesn’t have the downsides, the risky, runaway meltdowns, or things like that, it’s a real win for the planet.”

The idea of a subcritical hybrid reactor, one that doesn’t produce a sustained chain reaction would be highly desirable in a world thirsting for fossil fuel replacements in an effort to combat climate change. This zero consequence design would be relatively inexpensive compared to the megaproject fission-based nuclear power plants of the past and the ITER fusion technology that has absorbed billions of dollars in investment so far without achieving success.

How would a hybrid fusion-fission reactor work?

It would combine fissile materials such as uranium 235 with non-fissile ones like deuterium or thorium. It could even use the uranium contained within spent fuel rods, the waste product of current fission reactors, as its fusion fuel source. Apollo has hinted that it will use deuterium as the fission material. The reaction begins with the initiation of fusion generating high-energy fast neutrons. The fast neutrons trigger a fission reaction within the subcritical deuterium mass. Deuterium, which is also known as heavy water, is highly abundant. A chain reaction within a mass of it would never reach criticality. Hence the claim of zero consequences and emissions free.

The design wouldn’t require a large high energy plasma containment vessel with super-cooled magnets operating at near absolute zero. And the footprint for an Apolllo hybrid fusion-fission reactor would be a fraction of the size of ITER and other fusion technologies under development. In fact, Apollo intends to offer various flavours of its reactors, scaling from as small as a 5 Megawatts to power a single neighbourhood or a factory, to a 1 Gigawatt installation to keep the lights and heat on for an entire city.

Cassidy has indicated that Apollo already has a first customer but as of yet has not revealed who it is. All we know so far is that the first plant will not be built in the United States.




Len Rosen lives in Toronto, Ontario, Canada. He is a researcher and writer who has a fascination with science and technology. He is married with a daughter who works in radio, and a miniature red poodle who is his daily companion on walks of discovery. More...