Thorium molten salt breeder reactor as waste burner using heavy water as moderator

Presentation by Copenhagen Atomics to the 2022 Progrès Nucléaire webinar

[@gerrtryks2944]

You're presentations are fantastic; except,when will the first MSBR will be ready

[@mikeprice5838]

I first thought the guy at the very first of the video was John Stewart.

[@tintin_999]

FLiTh energy would be a name that gets more attention as it looks like "filth energy". Stardust Energy would be a nicer name.

[@deaddocreallydeaddoc5244]

I want a Molten Salt Reactor small enough to run my home. Any chance you'd consider producing them?

[@JonathanSchattke]

Easy enough, just get a license :P Smallest core I have modeled was a bulb 30 cm across.

[@user-gg8we2ot4b]

Promising, this nuclear reactor can run with different fuels including spent nuclear waste from LWRs. What is the safety mechanism in place to address a nuclear meltdown?

[@charlespoole2320]

No paradigm shift. If Thorium proves economical, there will be a mix of PWRs, Thorium, and other types for a long time.

[@dobotube]

It's conceivable that thorium could be more attractive in MSRs than in LWRs where Thermal breeding still requires periodic refueling.

[@tintin_999]

Given that you have a heavy water moderator, can the reactor be run on un-enriched uranium?

[@putinscat1208]

No. The purpose of the moderator is to turn fast neutrons into thermal neutrons. Natural uranium can be fissioned with fast neutrons. I do not know how efficient this is. Fast neutron reactors can burn waste as well.

[@dobotube]

@@putinscat1208 Heavy water reactors can run on unenriched uranium, lookup CANDU. But I doubt this one can.

[@dobotube]

I doubt this reactor can do that with all that Thorium around gobbling up neutrons.

[@putinscat1208]

@@dobotube The main problem with thorium is, it takes about 27 days for half of it to become U233. So it has to be fed into a reactor, filtered for remaining thorium, and fed in again. You are right that if it sits continuously, other products will probably appear because of neutron captures. Which is exactly what happens to current fuel rods. Fast reactors are the way to go. They produce much less waste, but they are a tad more complicated.

[@deaddocreallydeaddoc5244]

Congratulations! I always thought that it would be a European country that got this going before the U.S. due to the sluggish and resistant NRC bureaucracy.

[@chapter4travels]

That is being kind to the NRC.

[@bocckoka]

please make sure that your speaker has an appropriate mic setup. a basic headset would have been better

[@YellowRambler]

How is the concerns regarding the possible hydrogen production from the heavy water addressed?

[@peterolsen9131]

it would just bubble out with the gaseous fission products [krypton, xenon , ect] trapped for decay time [ about a month] then safely released or used in industry

[@paulmobleyscience]

@@peterolsen9131 Safely released? You mean daily Normalized discharges of effluents...

[@peterolsen9131]

@@paulmobleyscience did umiss the decay time and trapped bit in that sentence? fission gasses decay quickly to stable normal elements in about a month [ several half lives ] to the same ones that exist in the atmosphere, or are you just fearmongering?

[@paulmobleyscience]

@@peterolsen9131 Fear mongering? How many people did I say were going to die as a result? Everyone? Did I say everyone needs to run for their lives? Or maybe it was when I said all the animals in the area are going to perish? No that's right I didn't say any of those things....so who's actually afraid here? No I didn't "umiss" what you said I just know better than the half-life assessment of the probabilistic nature of nuclear physics and is humans first introduction to quantum mechanics...almost like using the Schrodinger equation on elements with more than one electron and choosing a wavefunction out of an infinite amount of wavefunctions of which breaks conservation of energy...

[@LFTRnow]

@@paulmobleyscience Which discharges are you concerned about? Tritium (radioactive hydrogen) is basically harmless at most levels and occurs naturally. It also could be captured and sold as it is valuable in several industries. The weak beta emission (max 18 keV) is particularly weak which is one reason it is basically harmless, even when released as tritiated steam. This is done by nuclear plants all the time due to the generation of minute quantities.

[@yngvesognen1092]

What about tritium?

[@carrdoug99]

How (why) are you using (heavy) water as a moderator in a molten salt reactor? Is it just to avoid graphite rod replacement every four or so years? (Your pump lasts ten). Seems like you're unnecessarily adopting the very medium that is involved with all four of the nuclear accidents to date. You say you have a system that deals with the accidental conversion of water to steam. Is it walk away safe?

[@Grobocopatel]

Why is easy: heavy water is the best moderator there is in terms of neutron economy, significantly better than graphite; and being liquid it's also not subject to swelling due to neutron irradiation. They also said their heavy water isn't pressurized, which makes sense given the salt neither is (the mechanical barrier in between would otherwise have to resist the dP). So leaking molten salt into the heavy water would pollute it with radioisotopes and boil it, but the steam would be produced at ~atmospheric pressure. As long as the steam can be condensed, it's plausible no overpressure will occur. And finally, how much heat is dumped into the heavy water during an accidental leak will depend on whether a salt plug is formed or not -again, the low pressure difference makes self-sealing plausible.

[@carrdoug99]

@@Grobocopatel thank you. So it is walk away safe.

[@Grobocopatel]

@@carrdoug99 It'll depend on how they manage emergency cooling of the heavy water really, so I wouldn't know. During normal operation they need to cool the heavy water anyway (thermalizing neutrons from MeV to a fraction of an eV heats up the moderator) but if it's a pumped flow system, using it also to cool during an accident wouldn't make it 'walk away safe'. If they plan to use a natural flow condenser to dumping heat into a water pool (i.e. like GEH's BWRX-300 will do) then it could certainly be. But without them disclosing more details on the design, can't say.

[@carrdoug99]

@Grobocopatel cool. Thank you so much. If they incorporate a freeze plug into their design, that would address the molten salt side of the safety equation, right?

[@Grobocopatel]

@@carrdoug99 Not really. As I understand it, the freeze plug conceptually works by melting under both loss of outside power conditions and plant shutdown, i.e. when there's no electrical power available from either behind or beyond the switchyard. Under those conditions*, the primary circuit will increase in temperature and melt the freeze plug, which also isn't actively kept cold anymore. Fuel is then dumped into a subcritical configuration where some passive mechanism, such as natural draft convection of air, takes care of decay heat removal indefinitely. But here we are talking about an accident event where the barrier separating the molten salt and the heavy water is compromised (i.e. a salt tube rupture or similar) and get into direct contact. A freeze plug won't diminish the likelihood of such an event nor mitigate its consequences. Personally, I'm not a fan of freeze plugs as a reliable safety feature. The time scale of an accident has to be commensurate with the characteristic time of fuel drainage. And the salt is potentially getting more viscous as it approaches lower temperatures down the drain and starts to form a slurry, so it's conceivable the line could get clogged along the way. A nice to have, but not something to rely on. (*) Either because the design keeps the fuel in a critical configuration all the time, as in an MSR with salt surrounded by moderator and no shutdown rods or neutron poisons, or because of plain old decay heat even after fission is stopped completely.

[@paulmobleyscience]

The issue with MSRs is the Tellurium embrittlement or segregation. Stronger more expensive alloys must be used and an additive just to get them to last longer than 4 years and why they were shelved back in the 60s. Thorium reactors are not Thorium reactors....they are Thorium decay chain reactors where Th232 must be transmutated to U233 so in fact they are still Uranium reactors. Calling them a Thorium reactor is a fallacy

[@LFTRnow]

it is not a fallacy because the input fuel is thorium. You are correct (as is explained) that the Th232 is transmuted to U233 to be the actual energy generation but you don't mine U233 from the ground (too bad too). As for tellurium embrittlement, I'm curious where you are hearing that. There is a very interesting video where corrosion was discussed by the ORIGINAL TEAM that worked at ORNL on the MSRE. They seemed to think that corrosion was not an issue when discussing their work. It is at ENH-jd6NhRc. I am aware of research that is ongoing regarding corrosion concerns. My quick search did not find anything about tellurium, but it did show that there are ways to mitigate corrosion, such as their example of adding lithium (see Q73c9LXr1tE). The video is 5 min long and is a presentation from ASM International.

[@paulmobleyscience]

@@LFTRnow Thorium is not fissle.....

[@paulmobleyscience]

@@LFTRnow As for Tellurium embrittlement or segregation...its why they were shelved in the 60s to begin with because they wouldn't last as long as water cooled reactors and thats just a fact. Add the issue of the graphite expansion/contraction issue and they are a complete waste of money and time

[@MrRolnicek]

@@paulmobleyscience U238 isn't fissile either and yet it is the majority fuel in most reactors. But I would also like to hear about the Tellurium thing. All I heard from every source ever (and I do search around for this stuff a lot) goes against that claim. So please, let us know your sources or how to find them at least. But it is strange, if the people who worked at Oakridge say they were shelved for different reasons and corrosion is managable and the people shelving them also said it's for different reasons I really do wonder who was it exactly that says it's for Tellurium embrittlement reasons.

[@paulmobleyscience]

@@MrRolnicek Of course U238 isn't fissle otherwise it's what would be used. In fact U238 neutron captures and exactly why the naturally occuring U235 does not chain in nature as it does in our reactors and exactly why most actinides are synthetic and not found in any measurable quantities in nature. But U238 is still Uranium even though U235 is the fissle material which is also Uranium...not a completely different name like "thorium" reactors which are actual Uranium reactors being that's the fuel used. As far as Tellurium embrittlement in the 60s that's what caused them to stop with the first expuremental reactor because at the grain boundry layer it was interacting with the nickle in the alloy. That's when the expuremental reactor was shut down due to the corrosion and not until the 70s which is where you see them using different alloys in the press release that you more than likely seen but there are many public releases from ORNL well before the 1978 release which is what you more than likely seen. I'm not here to hold your hand just because you have no clue there is more than one single published release of information on the Tellurium embrittlement issue. Take a long walk off a short pier and you can shove your attitude straight up your kester

[@JonathanSchattke]

Why should he start off with a lie? Not a good look, Copenhagen. CANDU can totally do thorium fuel cycle, that's the entire premise behind the Indian Heavy Water solid fuel program. Also, Shippingport demonstrated very very slight breeding with Thorium.

[@kurtisengle6256]

If you install the reactor in the hole it will eventually be buried in, you can skip the entire idea of handling used nuclear reactors. Dig it up up a half millenium and recycle it THEN.

[@davidwilkie9551]

"What is Spin?", ..of logarithmic condensation-coordination Truth of Eternity-now Interval Conception Superposition-point Singularity Positioning, or E=mC² e-Pi-bifurcation quantization, entangled cause-effect fields of relative-timing motion. Change the memes, genes and political schemes that deny Actuality of QM-TIMESPACE.

[@stevewilson5546]

This is an utterly rediculous idea. Water boils at 100C. Molten salt operates at 750C to 1,000C, which is well beyond the operating temperature of a pressurized water reactor. The core of a PWR is filled with water pressurised to 150 atmospheres, allowing the water to reach 325°C without boiling. The pressure of water would be much higher at 750C, making the system a time bomb waiting to explode. The result would be far worse than Chernobyl or Fukushima, spreading highly radioactive waste far and wide.

[@AximandTheCursed]

This is not a PWR, and the water is not pressurised, in fact it is not mixed in with the molten salt but run through insulated tubes in the reactor in a similar configuration to what graphite rods would be in a conventional PWR, also, the negative temperature coefficient and low pressure configuration in an MSR means that if the reactor is ever ruptured, the loss of mass from the core results in a sub-critical mass, and the escaped mass will solidify and cool passively, containing it in a way that would not be possible in a PWR. So, no, it will not spread radioactive waste very far at all, in fact it is self-containing.