Episode 93 | Trending TRISO | X-energy
Following the 2011 Fukushima incident, researchers around the world have been working to develop "walk-away safe" nuclear reactors.
Maryland-based X-energy has been exploring one of those solutions. Since 2009, they have been developing a commercial TRISO (TRi-structural ISOtropic) fuel, which does not contain any metal. Instead, uranium is encapsulated in silicon carbide and embedded in graphite "pebbles." These tennis ball-sized pebbles cannot melt.
My guest, Darren Gale, is X-energy's VP—Commercial Operations. He compares TRISO to both Oxide fuels, the industry standard, and Metal fuel, which are extremely efficient and have a promising future.
"The difference here is we are not having to use metal," he says. "The heat that is generated is higher than the melting point of a metal. It isn't higher than the melting point of graphite."
Another huge benefit is the reactor design X-energy is developing would not require lengthy refueling outages. Conventional nuclear plants today require at least a month-long outage every 18-24 months.
Instead, X-energy would employ a feed-tube, "fuel handling system." Each pebble can be pulled out of the reactor, tested for burn-up, and potentially sent back into the reactor.
X-energy also plans to use helium as a intermediary between the reactor and the steam generator. This eliminates the potential for water to stop cooling the reactor, leading to the formation of free hydrogen, which was disastrous for Fukushima.
Darren believes this TRISO design would be better-suited for a new plant rather than a retrofit on an existing facility. "[Only] if it was so difficult to license a new site somewhere…it's not just a matter of changing out the fuel," he says, adding a retrofit would likely involve fuel handling, storage, safety systems, and a new helium system.
X-energy is exploring several business options with their TRISO fuel technology, including conventional nuclear fuel, a mobile option, solutions for space, and small modular reactors.
The afternoon we sat down was about a day after NuScale finally received their Design Approval from the Nuclear Regulatory Commission. That should hopefully pave the way for companies like X-energy, with their own take on these smaller reactor designs, to get approval as well.
"There's not the angst of that first time through it," says Darren. "[NRC] has been through a review process of something that's not the typical."
At the time of this interview, X-energy was preparing their own permit with the NRC, and collecting requirements from potential customers. Their current plans for a plant would involve (4) 80-megawatt Xe-100 Reactors.
"That seems to be the ideal size for this small reactor market, talking with the utilities," says Darren." "They need enough electricity for whatever they're doing to make it worth their while for all the effort you’ve got to make to get that type of electricity."
To help reach that destination, X-energy has been working closely with the Department of Energy and has already received funding for it's TRISO fuel development.
"I've been in the industry 36 years, seen a lot of ups and downs," says Darren." "The exciting thing for me would be setting the stage for my kids and grandkids. This plant, when it gets built, to set the stage for next hundred years maybe, and support the world energy demand, that's a very exciting part of this."
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