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X-Energy and Southern Nuclear Team Up for Advanced Reactor R&D

In an innovative partnership tiny X-Energy, a start-up, has teamed with one of America’s biggest nuclear utilities, Southern Co., to collaborate in the development and commercialization of the design of a high temperature gas-cooled reactor.

Two firms which have received individually $40 million cost sharing grants from the U.S. Department of Energy (DOE) for work on advanced nuclear reactor technologies have joined forces. The objective of the partnership is to come up with more options to produce designs with high levels of performance. The firms have set a target to achieve commercial success by the 2030 time frame.

X-Energy and Southern Co. have signed a memorandum of understanding that pools their efforts. What’s interesting about the partnership is that the DOE grants support two very different types of advanced reactors.

The X-Energy start-up is working on a pebble bed high temperature gas cooled reactor. Southern Co. is developing a molten chloride (salt) fast reactor. Both firms bring to the table sets of partners that read like a who’s who of nuclear energy.

X-Energy is working with BWXT, Oregon State University, Teledyne-Brown Engineering, SGL Group, and two DOE labs – INL and ORNL.

Southern has partnerships with TerraPower, the Electric Power Research Institute, Vanderbilt University, and ORNL.

Does Triso Fuel Hold the Keys to the Partnership?

Neither Southern nor X-Energy have explained in their press statements where their R&D work intersects. The potential technological link between the two projects is Triso fuel. Some GEN IV designs of very high temperature molten salt reactors specify the use of it. The pebble bed design depends entirely on Triso fuel.

According to a 2013 report by World Nuclear News, research teams at two US national laboratories ORNL, INL) have found that irradiated carbon-coated Triso fuel particles are even more resistant to extreme temperatures than previously thought, offering potential benefits for reactor safety. TRISO fuel developed and tested at the Idaho National Laboratory was enriched to just over 9% U235.

The pebble bed and molten salt designs share another characteristic, and that is both have a negative temperature coefficient that automatically shuts down the reactor if temperatures get too high. The Integral Fast Reactor, a sodium cooled design, also has this safety feature.

Southern’s Leadership Role with X-Energy

As one the biggest nuclear utilities in the country, Southern has broken new ground for the second time. First, it sought and won a $40 million cost sharing grant from DOE for advanced R&D work. Second, it brought to the table an innovative small startup seeking to leverage its similar DOE grant, and equity investments, with a larger partner and potential customer.

pebble bed
X-Energy’s pebble bed work involves TRISO fuel in the form of 200,000 ceramic clad enriched uranium pebbles inside the reactor pressure vessel. Helium is heated there to very high temperatures and some pebble bed designs have specified outlet temperatures as high as 500C.or more. Some molten salt reactor designs call for temperatures within the primary loop up to  two-to-three times that level.

In addition to the fuel and reactor design issues, X-Energy will also need work on materials which can stand up to the high heat.

MIT’s Department of Nuclear Science and Engineering has a resource web site on pebble bed reactors which provides additional insights into the history of the technology and some of its perceived advantages.

Southern’s work plans to use molten chloride salts as a primary coolant at low pressure. It is a less known version of the molten fluoride salt reactor. TerraPower, one of Southern’s partners, has been exploring options for design of a molten chloride salt reactor since last year when it announced the effort during a nuclear energy conference at ORNL.

MCFR_labelWhile few technical details of the design have been released by Southern Nuclear, this online discussion posted in January 2016 by thorium reactor expert Kirk Sorensen explores some of what’s known about the technology in general. See also this report by Nuclear Engineering International which survey’s current molten salt R&D efforts as of February 2016. In August 2016 MIT Technology Review published a description of molten salt R&D efforts taking place in China.

CEOs Express Confidence in High Stakes R&D

In press statements reported by World Nuclear News, the CEOs of both X-Energy and Southern talked about bringing an advanced nuclear reactor to market.

X-energy CEO Kam Ghaffarian said, “We are thrilled to have Southern Nuclear involved in our project. I founded X-energy in 2009 out of a desire to make a significant and lasting contribution to clean energy generation in the US and around the world. This relationship firmly puts us on that path.”

Southern Nuclear chairman, president and CEO Stephen Kuczynski said, “Our relationship with X-energy builds upon the DOE awards we each received and puts the industry on a strong path to providing clean and safe nuclear enrgy for generations to come.” He added, “We understand fully the time and manpower it will take to bring the first advanced reactor to market and feel confident that pursuing this goal together will best leverage our combined research and commercial operation experience to do so.”

Potential New Business Model for Nuclear Start-ups

The collaboration of so many high profile nuclear energy players on advanced reactor designs adds a new layer of interest to the many entrepreneurial efforts going on elsewhere in the U.S. and Canada. While DOE had emphasized the development of public / private partnerships through its GAIN program at INL, it appears another path is opening for developers, and that is to partner with a major nuclear utility.

The question now becomes whether other large US nuclear utilities will look at Southern’s model and invest in an R&D partnership with an entrepreneurial developer. The benefits to the developer are the deeper pockets of the the utility and a potential customer for its efforts if to makes it to the finish line with a successful NRC safety design review.

Southern CEO Steve Kuczynski has spoken frequently about an objective of the US having 40% of its electricity coming from nuclear reactors by 2040. The firm is building two new Westinghouse 1150 MW AP1000 reactors in Georgia and will complete them to enter revenue service before the end of this decade.

Other large nuclear utilities have expressed interest in small modular reactors (SMRs) which are based on conventi0nal light water reactor technologies and which have a strong case for passing an NRC review.

UAMPS, a Utah electric cooperative, is the first customer for a 50 MW SMR design by NuScale which is slated to be built in Idaho. Up to 12 of the units may eventually be built at the site which is about 50 miles west of Idaho Falls, ID, on the grounds of the Idaho National Laboratory.

At one time TVA was working with B&W to design and license that firm’s 180 MW mPower SMR, but opted instead to seek an NRC early site permit for the Clinch River plant without selecting a specific vendor. B&W has since paired with Bechtel to seek a new customer for its mPower design.

Original Post

Content Discussion

Nathan Wilson's picture
Nathan Wilson on August 29, 2016

The potential technological link between the two projects [X-Energy and Southern Co./Terrapower] is Triso fuel.

That’s a fascinating idea. The Sorensen article which is linked above clearly assumes that the chloride salt will contain dissolved fuel, rather than being a coolant for solid fuel elements, similarly, the 2nd diagram above suggests the same thing. But we must remember that an underlying philosophy of the Terrapower travelling wave reactor is their belief that chemical reprocessing of the used fuel was undesirable: their reactor was to have an internal breeding ratio so high that that the oldest solid fuel elements could be shuffled out of the reactor and discarded without preventing breakeven (the discarded Pu would not be weapons-usable due to poor isotopic quality).

Switching from metallic or metal_clad-oxide fuel to TRISO pebbles has several big advantages: rapid shuffling of the pebbles means that all fuel elements can receive equal burn-up unlike conventional long fuel assemblies which burn-up more in the middle than the ends, TRISO is more likely to withstand the long exposure times that the traveling-wave concept requires (the fuel element must stay in the reactor not just for the burn-up period, but also several years more before that to breed the Pu from natural uranium). An additional advantage to the pebble fuel form is on-line refueling, so a complicate shuffling scheme won’t hurt availability. The extreme high temperature tolerance also allows a stronger negative thermal feedback for the fuel (reactivity of uranium fuel decreases as it gets hotter due to “resonance absorption”). Finally, TRISO pebbles are considered an excellent repository-friendly waste form where direct burial is to be used.

Hops Gegangen's picture
Hops Gegangen on August 30, 2016

I sort of follow what you’re saying, but then my idea of fun is a podcast on bosons and gluons and colored quarks. Now, how do you convince normal people that these new nukes are not the same as the one at Chernobyl? Maybe nuclear is too complicated for a democracy (of sorts).

Dan Yurman's picture
Dan Yurman on August 30, 2016

If you are interested in how a “normal person” learns about nuclear energy, read Gwyneth Cravens book on her experience.

Mark Heslep's picture
Mark Heslep on August 30, 2016

“how do you convince normal people that these new nukes are not the same as the one at Chernobyl”

o In 1947 there was an average of one global commercial air crash per week. “Falling out of the skies” was not a great exaggeration. In 1960 the annual aircraft accident rate was 50 per million departures. Now, the rate is zero to the nearest whole number per million departures, and six of the many aircraft models in service have zero major accidents (A350, 787, A380, 717, 747-8, etc)

o In the decade before the Roebling’s successful cable suspension Brooklyn Bridge, a bridge collapsed in Europe or America about once per month. Now, they don’t.

o In 1900 in the US and Europe, Cholera and Dysentery outbreaks meant one drank the spirits in cities, not the (un-boiled) water. Then came the municipal use of Chlorine in the water and sewers. Now, one can drink the water.


Paul O's picture
Paul O on August 30, 2016

I’m puzzled whether that was a rhetorical question, or a question that signals your own beliefs in spite of your own familiarity with gluons and such?

Could you help by clarifying whether you yourself think that the technology of nuclear plants today is the same as when Chernobyl was built, and whether that would make any difference in your view?

Personally I feel that the public would believe in what the scientists have built and tested, unless their confidence was being undermined by persons or groups with a contrary agenda.

Hops Gegangen's picture
Hops Gegangen on August 31, 2016

Actually, the safety of nuclear isn’t about science, it’s about engineering and project management. Engineering has improved greatly. The first nuclear plants were built either without modern fault tree analysis or without meaningful data on failure rates. Now we have software packages to manage huge fault trees and years of data on parts. So nuclear plants are not only safer, but availability has improved.

Given that every new nuclear plant seems plagued by overruns and delays, I’d say project management is not much improved. Maybe SMRs will make projects more manageable. But I look at something like the Vogtle plant construction and it sounds like a nightmare.

Nathan Wilson's picture
Nathan Wilson on August 31, 2016

I think this business of nuclear delays and cost over-runs is mostly a result of disproportionate attention by the media and also greater transparency. An aggressive schedule is always the cheapest, because people always work more efficiently under slight pressure. But being aggressive also means that some pieces of the project will miss their target dates, often delaying the end date. If you put extra padding in the schedule, and using the padding is painless, people will use it. This is worse for first-of-a-kind projects, so yes, it should get much better as build rates increase.

Regarding public acceptance of safety predictions, that’s the great thing about TRISO fuel. It can really take abuse, and the abuse can be demonstrated in the lab. Similarly, high temperature reactors all can use fully passive shut-down cooling. Compared to sodium-cooled fast reactors (or Gen II LWRs with multiple complicate backup systems), the simple passive safety of salt-cooled TRISO-fueled reactors is much easier to explain to people.

Engineer- Poet's picture
Engineer- Poet on September 1, 2016

Compared to sodium-cooled fast reactors (or Gen II LWRs with multiple complicate backup systems), the simple passive safety of salt-cooled TRISO-fueled reactors is much easier to explain to people.

S-PRISM has sufficient air-cooling to be passively safe.  It’s amazing what an atmospheric-pressure coolant operating at upwards of 500°C will let you do.