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589 points atomic128 | 8 comments | | HN request time: 1.111s | source | bottom
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philipkglass ◴[] No.41841019[source]
Based on the headline I thought that this was an enormous capital commitment for an enormous generating capacity, but the deal is with a company called Kairos that is developing small modular reactors with 75 megawatts of electrical output each [1]. 7 reactors of this type, collectively, would supply 525 megawatts (less than half of a typical new commercial power reactor like the AP1000, HPR1000, EPR, or APR1400).

Kairos is in a pretty early stage. They started building a test reactor this summer, scheduled for completion by 2027:

https://www.energy.gov/ne/articles/kairos-power-starts-const...

EDIT: Statement from the official Google announcement linked by xnx below [2]:

Today, we’re building on these efforts by signing the world’s first corporate agreement to purchase nuclear energy from multiple small modular reactors (SMRs) to be developed by Kairos Power. The initial phase of work is intended to bring Kairos Power’s first SMR online quickly and safely by 2030, followed by additional reactor deployments through 2035. Overall, this deal will enable up to 500 MW of new 24/7 carbon-free power to U.S. electricity grids and help more communities benefit from clean and affordable nuclear power.

[1] https://kairospower.com/technology/

[2] https://news.ycombinator.com/item?id=41841108

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ViewTrick1002 ◴[] No.41842094[source]
Would be extremely interesting to the the $/MWh for the deal to understand the viability.

Otherwise similar to the NuScale deal which fell through last autumn.

A PPA like agreement which then only kept rising until all potential utilities had quit the deal.

All honor to Kairos if they can deliver, but history is against them. Let’s hope they succeed.

> NuScale has a more credible contract with the Carbon Free Power Project (“CFPP”) for the Utah Associated Municipal Power Systems (“UAMPS”). CFPP participants have been supportive of the project despite contracted energy prices that never seem to stop rising, from $55/MWh in 2016, to $89/MWh at the start of this year. What many have missed is that NuScale has been given till around January 2024 to raise project commitments to 80% or 370 MWe, from the existing 26% or 120 MWe, or risk termination. Crucially, when the participants agreed to this timeline, they were assured refunds for project costs if it were terminated, which creates an incentive for them to drop out. We are three months to the deadline and subscriptions have not moved an inch.

https://iceberg-research.com/2023/10/19/nuscale-power-smr-a-...

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credit_guy ◴[] No.41842380[source]
> All honor to Kairos if they can deliver, but history is against them.

History is not really against them. Our current reactors (mainly pressurized water reactors) are the way they are because Admiral Rickover determined that PWRs are the best option for submarines. He was not wrong, but civilian power reactors are not the same as the reactors powering submarines.

PWRs are expensive mainly because of the huge pressure inside the reactor core, about 150 times higher than the atmospheric pressure. For comparison, a pressure cooker has an internal pressure about 5 times higher than the atmospheric pressure, and such a cooker can explode with a pretty loud bang.

The Kairos Hermes reactor design is based on a design that was tested in the '60s, the Molten-Salt Reactor Experiment [1]. While such a reactor can be used to burn thorium, Kairos decided to go with the far more conventional approach of burning U-235. The reactor operates at approximately regular atmospheric pressure. This should reduce considerably the construction costs.

Of course, there are unknowns. While the world has built thousands of pressurized water reactors, it has built maybe 10 molten salt reactors. For example one quite unexpected effect in the MSRE was the enbrittlement of the reactor vessel caused by tellurium, which shows up as a fission product when U-235 burns.

The Nuclear Regulatory Commission is a very conservative organization, and they don't have much experience with molten salt reactors because nobody has. It took them 6 years to give NuScale an approval for a pressurized water reactor, design that they knew in and out. My guess is that they will not give Kairos an approval without at least 15 years of testing. But Google's agreement with Kairos is quite crucial to keep this testing going.

[1] https://en.wikipedia.org/wiki/Molten-Salt_Reactor_Experiment

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cyberax ◴[] No.41843113[source]
> The Kairos Hermes reactor design is based on a design that was tested in the '60s, the Molten-Salt Reactor Experiment

MSRs are a costly distraction. They are not viable without literally hundreds of billions in research and development money. That's why all the MSRs startups are failing long before they even start the licensing process.

> For example one quite unexpected effect in the MSRE was the enbrittlement of the reactor vessel caused by tellurium, which shows up as a fission product when U-235 burns.

It was not unexpected. The _main_ issue with MSRs is that they have to contain fluoride salts that release elemental fluorine radicals as a result of radiolysis. So the reactor vessel walls will be eaten up by them, rather rapidly. Especially when reactors are scaled up to a level that makes them practical. And then you have all the fission byproducts that literally include almost all the Periodic Table.

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1. pfdietz ◴[] No.41844000[source]
The Kairos design does not dissolve the fuel in the salt.
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2. cyberax ◴[] No.41844100[source]
OK, that's interesting. And it's far better than MSRs, but it still exposes fluoride salts to radiation. It also is a pebble bed reactor, so it'll have all the problems of pebble beds: cracking pellets, difficulty in fuel reprocessing, more nuclear waste, etc.

But yes, this design might be actually feasible for small reactors. But I bet that it won't be cheaper and it'll be impossible to scale to levels approaching PWRs.

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3. conradev ◴[] No.41845449[source]
The theory, at least, is that making SMRs in a factory allows for a steeper and more sustainable learning curve

> Both Hermes and ETU 3.0 will be built using modular construction techniques, with reactor modules fabricated in Kairos Power's facility in Albuquerque, New Mexico, which will be shipped to Oak Ridge for assembly.

https://www.world-nuclear-news.org/articles/work-begins-on-f...

4. pfdietz ◴[] No.41847460[source]
Fluoride salts by themselves are very radiation resistant, chemically more so than water. The biggest concern would be liberation of elemental fluorine, but if the salt is kept slightly reducing (which one can do in a sterile salt without dissolved uranium) the fluorine instantly reacts back to fluoride. The slightly reduced salt is also preferred to limit corrosion, allowing the vessel and pipes to be made of stainless steel (FLiBe with dissolved uranium needs special more expensive alloys because chromium would dissolve.)

Activation is also low. The two concerns would be traces of tritium from the two-step activation of beryllium (formation of 6He by (n,alpha) reaction, decay of 6He to 6Li, then (n,t) on 6Li), and also formation of 10Be (half life, 1.4 million years, but the thermal neutron capture cross section of 9Be is only 8.5 mb). The chemical toxicity of beryllium would considerably exceed its radiotoxicity, I imagine.

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5. credit_guy ◴[] No.41847664{3}[source]
> traces of tritium from the two-step activation of beryllium

Also from the 6Li absorption of 1 neutron. The Lithium used is almost pure 7Li, at 99.995%. But there is still 50 ppm 6Li in it.

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6. pfdietz ◴[] No.41847881{4}[source]
Yes. The inescapable tritium production from Be sets the lower bound on how pure the 7Li has to be.
7. cyberax ◴[] No.41850355{3}[source]
> The biggest concern would be liberation of elemental fluorine

Yep.

But I'm personally more worried about the pelletized fuel. Pellets are not a great form-factor, and they don't have cladding. Fluoride salts are also far more aggressive than water (mechanically and chemically), so this will limit the maximum specific power of the reactor. So I don't think that something like 1GW molten salt reactor is even possible.

It might be OK if they want to continue using SMRs, though.

> The slightly reduced salt is also preferred to limit corrosion

Sidenote: that's actually not always a great idea. Steel is stainless because it's covered in a film of oxides, and without oxygen it might not be able to form.

This is a problem for the Russian BREST-300 reactor that is cooled by molten lead, they had to do almost 10 years of research to perfect a system that controls the amount of dissolved oxygen in the molten lead. And it's still not clear if they succeeded until the full-scale reactor is built.

In this case, though, I think that they can tune the reducers to react with fluorine preferentially, while still leaving enough oxygen.

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8. pfdietz ◴[] No.41852069{4}[source]
Lead is a rather different case, because liquid lead itself corrodes steel. The oxide layer is needed to protect the steel from the lead. FLiBe by itself does not corrode steel.

https://www.sciencedirect.com/science/article/abs/pii/S00109...