With Hermes, Kairos Power Offers a New, Timely Path for Advanced Reactors

Source: NEI | Matt Wald | March 5, 2021

In a California lab, the Kairos team evaluates hardware for the prototype pebble bed reactor.

Innovation is key to reducing carbon emissions—climate activists, energy experts and the Biden administration agree.

Progress in nuclear innovation over the past year has established a pipeline of advanced reactor technologies that are set to become available in the late 2020s or early 2030s, with an array of designs and development approaches.

One developer, Kairos Power LLC, won $303 million in funding from the U.S. Department of Energy’s Advanced Reactor Demonstration Program (ARDP) to build a prototype, a step on the way to its full-scale reactor. This novel approach to the development cycle offers an important new path to deliver advanced reactors.

Kairos Is Breaking New Ground, Step by Step

Most new reactor development moves from design to various engineering simulations to testing components and finally becomes a full-sized, steel-and-concrete first-of-a-kind power plant. But, to build its reactor, Kairos Power is following a development model used successfully by SpaceX and other high-tech enterprises: build a little, study and test, and then build again.

The Kairos prototype is called Hermes, from the Greek deity who carries messages and moves quickly between mortals and the gods.

“Demonstrating Hermes confirms you can license it, it confirms you can get it to operate, it confirms that you understand what your costs are and that your supply chain works,’’ said Per Peterson, chief nuclear officer of Kairos. The company will apply for a construction permit this year at a former DOE site in Tennessee.

The process for getting regulatory approval is already well under way as well, with the company submitting “topical reports” to the U.S. Nuclear Regulatory Commission, smoothing the way for licensing. The safety analysis for the prototype is the same as the one for the full-scale reactor, although the commercial reactor will be considerably larger.

The Kairos Design Will Use TRISO Fuel in a New Way

Kairos’ design is a pebble-bed reactor that will use TRISO fuel, super-tough pellets about the size of Ping-Pong balls, that encapsulate uranium in multiple layers of heat-resistant materials. Other developers using TRISO—such as X-energy LLC, another ARDP award winner—will use helium gas to transfer heat, but Kairos will float the TRISO pellets in a salt mixture. Salt is extremely good at absorbing heat.

A Kairos engineer prepares a structural component of the Hermes prototype for durability testing.

The Hermes demonstration will include only the nuclear heat-generating portion; it will not convert the heat to electricity. Hermes will be another opportunity to deploy hardware, make sure it works right and redesign it if necessary before moving on to a full-scale plant.

Making Big Changes to Meet Big Goals

The combination of TRISO fuel and salt coolant will create a very stable reactor that can operate at extremely high temperatures and low pressures. This means the final product will be simpler to build, can change power output easily to match wind and solar, and produces heat that can do a variety of jobs—including help decarbonize heavy industry.

Kairos says that its target market is to replace the power plants running on fossil fuels, many of which were built in the 1990s and will be reaching retirement age in the 2030s.  Plus, for people outside the U.S. without reliable electricity, coal is an attractive energy source, even if it exacerbates the climate challenge.

“Energy poverty is worse for the poor, at least in the short term, than climate change,” said Peter Hastings, Kairos’ vice president of regulatory affairs and quality. Kairos and other reactor developers want to give the developing world a clean alternative, so that we can solve the energy problem while protecting the climate.

It’s the Right Time for Carbon-Free Energy

Kairos is aptly named; it’s another ancient Greek reference, a term meaning “the opportune moment.” With the growing momentum behind eliminating carbon emissions, now is the moment that we need new technologies and new innovative approaches—like the company’s Hermes prototype—to reach a clean energy future.