It is an exciting time for nuclear energy. While nuclear energy is the most productive zero-carbon energy source, development of new reactors has been rather stagnant over the past few decades. Now that carbon emissions are a looming concern, a whole new generation of companies and reactor designs are being proposed that will address many of the lingering (though overstated) concerns remaining about nuclear energy. These companies are one of our best shots at being able to provide cheap, clean abundant energy.
An interesting player in this new generation of nuclear companies is Transatomic Power. Transatomic is still working on a production scale reactor, but I think that their proposed design is exciting enough to merit a look.
For the uninitiated, nuclear reactors may seem like space magic, but in fact they work (almost) every other generator of electricity: A medium (water) is heated up to boiling, it creates steam and turns a turbine, which generates electricity. In the case of gas generators, gas is used to heat the water. Coal generators, coal. Nuclear generators, nuclear material. What makes these methods of electricity generation different is the qualities of the heating method. Wind is intermittent, coal is pollutant (particulates and CO2), gas emits CO2 and so forth. Nuclear emits no airborne pollutants, but the fission process can irradiate things in the surroundings. Unconsumed nuclear material can also be quite dangerous.
So what makes the Transatomic Power design different?
The first difference is that the fuel is a liquid made by suspending the radioactive material in a salt. This salt is solid at room temperature, but will flow at high temperatures. This replaces the fuel rods that we all know and love so well from the Simpsons intro sequence.
Liquid fuel has a number of benefits, not least of all being that it allows for the introduction of a passive safety feature called a freeze valve. As part of the primary loop of the reactor, there is a valve that is held shut with frozen fuel, which has to be electrically cooled. As long as electricity is being delivered to this valve, all is well. In the case of a failure, electricity would be cut to the valve and it would melt, emptying the fuel into a cooling pool. In short, the conditions that lead to a failure also initiate the safety procedure. This would have avoided the Fukushima situation where a secondary system was required (and failed) to enact the safety protocol.
Reactors have to be maintained in a certain state called “criticality.” This means, essentially, that there is a chain reaction occurring, allowing the reactor operate continuously. To achieve this, a moderator must be used, which slows the reaction enough so that it can be useful. Water is an effective moderator and is used for many reactor designs, including the Light Water Reactor. The problem, as one can guess, is that superheated, radioactive water can easily become superheated, radioactive steam and cause problems. Transatomic gets around this by using a zirconium hydride moderator, no water necessary. This means that the water that does exist in the Transatomic Reactor is quite separate from the radioactive process, eliminating the danger of radioactive steam escaping the system.
Light Water Reactors have to be operated at a very high pressure. This leads to all sorts of difficulties in fabrication and operation. The Transatomic Power design is operated at atmospheric pressure, drastically reducing the chance of failure and potentially reducing the cost of fabrication.
This reactor design is extremely exciting because it addresses many of the concerns that exist with nuclear energy, namely: safety, waste, proliferation and cost. The passive safety features of this reactor design will prevent a Fukushima-type “Beyond Design Basis” disaster. The enrichment of the reactor can be as low as 1.8% (as compared to a conventional 20%), meaning that Transatomic can actually burn existing nuclear waste, allowing us to use our stockpiles of nuclear waste as fuel! This low enrichment level also puts to rest fears of proliferation, since such low enrichment levels are not more weaponizable than, say, a truck full of gas. Finally, the lower pressure, the low enrichment levels and the modular design mean that a Transatomic Power reactor should be able to find cost efficiencies over Light Water Reactors.
Finally, there’s something cool about the fact that this initiative is mostly funded by Peter Thiel’s Founder’s Fund, as opposed to a clunky government research program. This alone gives me hope that we might actually see some of these designs powering our Jetsons-style robot maids for years to come.