TerraPower’s Natrium: Combining A Fast Neutron Reactor With Built-In Grid Level Storage

Most new nuclear fission reactors being built today are of the light water reactor (LWR) type, which use water for neutron moderation into thermal neutrons as well as neutron capture. While straightforward and in use since the 1950s in commercial settings, they are also essentially limited to uranium (U-235) fuel. This is where fast neutron reactors are highly attractive.

Fast neutron reactors can also fission other fissile elements, covering the full spectrum of neutron cross sections. TerraPower’s Natrium reactor is one such fast reactor, and it’s the world’s first fast reactor that not only targets commercial use, but also comes with its own grid-level storage in the form of a molten salt reservoir.

The upshot of this is that not only can these Natrium reactors use all of the spent LWR fuel in the US and elsewhere as their fuel, but they should also be highly efficient at load-following, traditionally a weak spot of thermal plants.

TerraPower and its partners are currently looking to build a demonstration plant in Wyoming, at the site of a retiring coal plant. This would be a 345 MWe (peak 500 MWe) reactor.

Why Natrium is Exciting

Render of the demonstration TerraPower Natrium plant. (Source: TerraPower)

As mentioned in the introduction, the Natrium reactor can use not just U-235 as its fuel. This is a property of the neutrons used in the reactor. As a refresher, the water used in current commercial fission reactors acts as a moderator on the neutrons that are produced during a nuclear fission chain reaction, effectively slowing them down. This makes the resulting thermal (‘slow’) neutrons fall right within the neutron cross section for U-235 and a few other elements (e.g. Pu isotopes), but incapable of fissioning most transuranics and actinides.

Over time the build-up of those transuranic and actinide isotopes ‘pollute’ the fuel in an LWR to the point where the nuclear chain reaction is far less efficient than with ‘fresh’ fuel rods. This is the point where an LWR is refueled (generally on a 2-year cycle), and the spent fuel rods are stored or reprocessed. In the latter case the problematic isotopes are removed via chemical processes as a lot of U-235 fuel remains in these fuel rods.

Since Natrium uses sodium as its coolant instead of water (the reason behind its name), it can use fast neutrons as well as thermal neutrons. As a result any isotope in the fuel that’s fissile can become part of the nuclear chain reaction, allowing this reaction to proceed until no further fissile elements remain in the fuel. This includes the U-238 that makes up a large percentage of uranium fuel.

Natrium reactors could thus run on the spent fuel stored in cooling pools at LWRs around the country and only produce small amounts of short-lived waste. This is essentially the culmination of decades of research in US test reactors like the EBR-II and FFTF and similar in scope to Russia’s BN-series of fast reactors. TerraPower has teamed up with Centrus for the production of the High-Assay, Low-Enriched Uranium (HALEU) fuel for the Natrium reactor.

In addition to these reactor designs, Natrium also adds an on-site energy storage in the form of molten salt that can bump up the reactor’s electrical output from 345 MWe to 500 MWe for about 5.5 hours. This would make it possible to flexibly cover peaks in demand.

Still a Long Road Ahead

An overview of the NRC’s tasks and responsibilities.

Before anyone is allowed to build or operate a nuclear plant in the US it has to go through the Nuclear Regulatory Commission (NRC). A panel of experts will analyze, comment on, and require changes to offered designs until they are confident that that all regulations are adhered to and all relevant questions answered. I covered this process in detail previously.

For TerraPower’s Natrium this certification process can be followed via its public page. This tells us that Natrium is currently in the pre-application stage. Once the application has been finalized and submitted, Phase 1 of the Safety Evaluation Report (SER) can commence, which will then go through another few phases before resulting in the final SER (FSER), which will be used for the rulemaking, at which point the Natrium design will be allowed for new construction in the US.

With that approval in hand, the NRC would still have to approve the construction of each individual Natrium reactor, involving more safety reports, and in order to also be allowed to turn the reactor on and operate it commercially, even more safety reviews and reports would be involved. This makes the claim by TerraPower (on e.g. their Fact Sheet) of the Natrium design being available for commercial use (i.e. construction of new plants) by the late 2020s seem believable.

Cue the Competition

Cut-away model of the BREST-300 reactor. (Source: Rosatom)

Perhaps most telling is that TerraPower isn’t the sole company seeking to commercialize a fast neutron reactor. In Russia, Rosatom along with nuclear fuel manufacturer TVEL have announced the start of construction of the BREST-OD-300 lead-cooled reactor. Like the Natrium design, this is a Generation IV fast neutron reactor, but it uses lead as coolant instead of sodium, which is beneficial in terms of heat transfer capacity as it has a higher melting point than sodium.

BREST-OD-300 is designed to have on-site fuel processing capacity, to keep a closed uranium fuel cycle within the plant’s grounds. Alongside this reactor type, Rosatom is also looking to build a number of sodium-cooled BN-1200 fast reactors which build upon the research done with the BN-350, BN-600, and BN-800 reactors since the 1970s. So far, two BN-1200s are scheduled for construction in Russia.

In China, the CFR-600 has been under construction since 2017. Much like in Russia, the idea is to run these fast reactors alongside LWRs in a complementary manner. Meanwhile in India, its PFBR is scheduled to be put online by 2021, when it will be used primarily to transmute (breed) U-233 from thorium as part of India’s thorium-based fuel cycle.

It’s clear that the demand for commercial fast reactors exists, and that TerraPower’s Natrium reactor might be the US’s best bet to be a part of this market.

Adding Grid Level Storage

Where TerraPower’s Natrium reactor is different from the competition is that it focuses not so much on the traditional role of thermal plants which involves getting as much steam or equivalent to a turbine to generate electricity. Instead, the heat from the reactor’s core is led away using the sodium coolant and stored in multiple large, insulated tanks. This is similar to how Concentrated Solar Power (CSP) with thermal storage works.

Overview of the thermal energy transfer in the Natrium reactor design. (Source: TerraPower)

This stored heat energy can then be used as needed to spin an electric generator, heat buildings, and so on. By decoupling the processes of generating the thermal energy and using it for generating electricity and so on, the electrical output of such a nuclear plant can be varied dynamically depending on the needs of the grid. This leads TerraPower to advertise Natrium as the ideal firm power compliment to a grid with a lot of variable renewable energy (VRE) like solar and wind.

Currently VRE-heavy grids rely on simple-cycle combustion turbines (SCCT) which have no waste heat recovery. While a lot faster to spin up and down than combined cycle turbines (CCGT), a CCGT plant will have a thermal efficiency of over 60%, whereas a simple-cycle plant will be generally just over 30%, with worse efficiencies while idling, such as when they are standing by to cover surges in demand.

The Broader Picture

The world today grapples with the realization that the sooner we rid ourselves of fossil fuels, the better off we’ll be. Yet right now the overwhelming majority of our daily energy use for transport (even with electric vehicles) and such still comes from fossil sources. In US states like California, natural gas makes up the overwhelming majority of its in-state sources of electricity using its over 200 natural gas plants. These are a combination of SCCT and CCGT plants.

With the rapid increase in the deployment of VRE, it’s important to provide grid-level storage and peaker plants which can respond rapidly to both the naturally fluctuating demand for power, as well as the variable input from these VRE sources. This is one area where something like TerraPower’s Natrium design may make a lot of sense, especially considering that it removes the ‘nuclear waste’ argument that is often used against new nuclear.

Regardless of how things play out in the USA, it seems clear that many countries are ready to embrace fast neutron reactors for commercial purposes. It still remains to be seen whether TerraPower’s concept of thermal storage in combination with a nuclear plant will stick, however. It too trades some thermal efficiency for convenience, which may or may not be worth it in the long run and might be better covered by e.g. battery storage alongside a traditional thermal plant design.

66 thoughts on “TerraPower’s Natrium: Combining A Fast Neutron Reactor With Built-In Grid Level Storage

  1. Sodium cooling has been tried before, with the fast breeder reactors of hte 1960s and 1970s. I don’t think any survive in operation. A leak in a PWR is pretty horrible, but a leak of molten sodium is horrific.

    1. Error: Google failed to return an expected code

      Not retyping my comment. Google login always fails.

      Article says it doesn’t sodium…
      “Since Natrium doesn’t sodium as its coolant instead of water”

      I though sodium was safer due to it becoming a solid without heat and it’s not an explosive / expansive gas.

      1. Solid room temperature sodium can just about spontaneously ignite. The melted stuff is pretty much guarantee to do so. This makes sodium oxide that when combined with water, gives you sodium hydroxide, which is plenty nasty. Just keep the whole reactor building flooded with argon to be safe.

        1. Sodium is an alkali metal it is in the same part of the periodic table as Lithium, Potassium, Rubidium, Caesium and Francium. Sodium will burn in air or it will self ignite and explode in water (or ice).
          (ref: https://www.youtube.com/watch?v=IaP3lGfa2n0 <- Periodic Table of Videos ; Sodium Underwater)
          (ref: https://www.youtube.com/watch?v=7IT2I3LtlNE <- Periodic Table of Videos ; Sodium )

          But no matter were you build a oil/coal/gas/fission/fusion power plant it still needs to be near a very large body of water to maximise the efficiency of the turbines (ref: Carnot cycle). You have a source of heat (fission) so you need an equally large source of cold (water). So there will be water, there is pretty much always water when a turbine is used to generate energy. So the system needs to be designed that the molten/solid sodium never comes into direct contact with oxygen and water (liquid or steam*).

          *Although technically steam is used but only with nitrogen or carbon dioxide to removed or deactivate residual sodium during decommissioning of a sodium based system.

        2. Nevermind that – conventional reactor fuel is in the form of oxides, which are hardly soluble and the radioactive leaks don’t spread out from where they fall. MSR fuel is in the form of salts, which are easily soluble. In an accident, any containment leak will result in an absolute disaster.

        1. And since we’re not even soldering with lead any more, what else are you going to do with it?

          Besides, core material contaminating your lead coolant? Let it solidify, it’s shielded in place! Whereas core material in your sodium coolant, as soon as the sodium combusts or reacts with water, you’ve got radioisotopes swimming in liquid caustics. I know which one I’d rather clean up..

  2. Oh SuperPhenix try to come back from the dead!

    It’s first use was to burn Pu239 from retired nuclear bombs, then MOX with is a blend of Pu239 and uranium. Then the final goal would have been to burn refined spend combustible from other reactors (As it was Areva milking cow).
    The whole idea was DOA: uranium price were too low to be competitive.

  3. “Since Natrium doesn’t sodium as its coolant instead of water…”
    This “sodium” there is weird. Something is off with this sentence…
    (Not native english speaker here, bust still…)

        1. I’ve noticed the verbisationallnessing for awhile now, and there’s a secondary problem with just sticking extra endings on a word – usually when there’s a cromulent much shorter word.

          1. In German this practice is legit. Also stacking words together for a new one. Very helpfull for describing things exactly. But not that easy for foreigners.

    1. Though I’m all for verbing anything, jokes aside, I’m guessing that’s supposed to be “Since Natrium uses sodium as it’s coolant instead of water…” :)

      1. We have a saying in Nashville: “Ain’t no noun that can’t be verbed.” (Southerners also seem to like double negatives, although this one seems to have three…)

        Imagine my surprise, in Nanjing China, learning classical Chinese, that they didn’t even _distinguish_. You can “red” something, and we all know what you mean. Super useful for poetry, and saves you from having to think of exactly what verb describes the noise that a gong makes — it gongs.

  4. I totally agree that this is better than fossil fuels for grid power.

    That said, I’ve yet to see an analysis of the difference between renewables vs. fission that compare net energy released as “new” heat (as it relates to global climate change). Capture solar, use it to run an AC unit, motors, etc. and the net heat impact seems small. But traditional fission reactions use a refined material that (I think?) otherwise doesn’t add significant heat in their natural form/ore.

    Back of the napkin math, based on googling how many joules of energy were released at Hiroshima, how many joules the average US home uses, the number of homes in the US, and converting that into how many ‘hiroshima equivalents’ of fission it would take /each day/ to run the US (assuming grid fossil fuels are all replaced with fission, and renewables were to remain a small percent of production). I sure hope my math (or my logic) is wrong, because intuitively that many daily ‘Hiroshima equivalents’ ( net heat only, not radiation) would have to have a measurable impact on global climate too. Again, better than fossil fuels and greenhouse gases, but it does make me want to go out and buy some solar panels!

    If someone here has the technical knowledge to fix my math or logic (or, independently confirm it), please do- again, not my area of expertise, I’m just passionately curious about how much additional heat fission “creates” and the potential impact.

    Maybe extra heat just radiates faster from the planet into space (especially if greenhouse gases are reduced)?

    1. Kinda see where you were getting at.

      The problem with climate change isn’t exactly that we’re “warming” the planet as in we are generating heat. It warms itself up spontaneusly with heat from the sun and with heat from natural fission ocurring under the tectonic plates (uranium, pretty heavy, accumulates on the nucleus, then fission).

      The problem is that we produce things that prevent the system from self regulating it’s temperature to a livable level. Greenhouse gases and CFC and alike prevent heat from radiating away from earth.

      Every proccess is inherently inefficient, so, even your mitocondria will produce waste heat. We do generate a big amount of heat into the ambient with all our tech. But it’s just a drop on the oean.

      The big question is, how much do we pollute to construct, operate and maintain each of these electricity sources?
      If fission has lower greenhouse emission and ambiental degradation per joule of electricity generated than others, then we should be going all out with it, as long as eonomics allow.

      We should be considering end-to-end when thinking about this, so, all the way from the amount of concrete used, through the fuel manufacturing (for the ones that use fuel, unlike solar and eolic) up to the operation itself, like waste disposal and whatnot.

      It’s a very complicated subject that has been on discussion since ever and is a bit above my league to bring up numbers, but luckly there are ones that dedicate themselves to analyse this. I don’t have any external links to the relevant studies, but be sure to do a seach around, you will find very good readings from the academics and all kinds of movements.

      1. “The problem with climate change isn’t exactly that we’re “warming” the planet as in we are generating heat. ”

        No, the problem with climate change is that a greenhouse gas changes a multiplier on the *total* heat received by the planet (which is ~170 PW) while its generation produces a miniscule amount of power (on the ~TW scale). Effectively, anything that produces a greenhouse gas to generate power is ludicrously inefficient.

        Renewables and nuclear only change the total heat balance at the TW scale, so they’re a drop in the bucket. If we completely eliminated greenhouse gas emission, we *still* likely wouldn’t have to worry about the effect on Earth’s heat balance from our power generation. The next thing after that would probably be effects on the Earth’s albedo from cultivated lands.

        But that’s totally negligible. Adding TW of heat input to the Earth warms it up by less than a milli-kelvin.

    2. I don’t have any numbers for this but my intuition says replacing burning fossil fuels with nuclear would be a similar amount of heat generated unless nuclear is massively more or less efficient, so no effect there.

      1. This type of reactor is less efficient for output energy. The majority of efficiency comes to play with the cost of supply and it’s spent fuel.
        They can reuse the spent fuel that is sitting in storage casks, with a half life in the thousands of years before it’s stable. They can actually get paid to take the waste and use it for some extra profit. The final waste is said to have a 25 year shelf life.
        Basically breeders are known for not being efficient but as a waste disposal plant, they can make money.

    3. My gut feeling that it doesn’t matter (hardly) at all.
      The earth constantly radiates heat into space (and is heated up by the sun and from within). How much depends on the composition of the atmosphere. More heat generated means more heat radiated away.

      The only problem is that we change the atmosphere, thereby changing the proportion of heat that radiates into space w.r.t. received and generated.

    4. “Capture solar, use it to run an AC unit, motors, etc. and the net heat impact seems small. But traditional fission reactions use a refined material that (I think?) otherwise doesn’t add significant heat in their natural form/ore.”

      Well, I mean, it’s more complicated than that. Panels effectively have a near-zero albedo in terms of reflection, so they effectively absorb everything (either as heat or as electricity), and the Earth’s surface does reflect a fair amount of light. But typically panels are on ground, which isn’t that reflective normally. Although if you put them in the desert, that’d be a much bigger increase in heat load. A “super simple” estimate would say you’re generating ~50W/m^2 on average when the sun’s up (assuming “averaged” energy input of 340 W/m^2, assuming “typical” cloud cover bouncing 80 W/m^2 of that away, and a ~20% efficiency) but adding 260 W/m^2 to the Earth’s atmosphere (again same as above). However with the panel not there, you’d typically be adding ~240 W/m^2, meaning you’re only “net” adding about 20W for every 50W generated. (Again, over highly reflective surface, this would be way worse, like ~140W for every 50W generated for desert sand).

      Which looks awesome compared to a nuclear plant at ~1/3 efficiency, which seems like it would add 150W for every 50W generated. However the “waste heat” there doesn’t have to be dumped to the atmosphere directly at all. But still, if you were *really* worried about overall heat balance, panels strategically placed could be a really good idea.

      So your “instincts” in some sense are right.

      Except… this is all totally and completely pointless. Humans generate tens of TW, but the planet receives like ~170 PW of solar radiation, and absorbs ~120 PW of it (and in thermal balance, reradiates 120 PW). Our impact on the “heat balance” of the planet from *energy generation* is utterly pointless. In fact, we’ve got a bigger effect on Earth’s heat balance due to cities and roads than from heat generation, because any multiplier on that “120 PW” is *huge*.

      And, of course, our *biggest* effect is, of course, greenhouse gas, because that’s a direct multiplier on the “120 PW reradiated” number.

    5. Fission is as renewable as anything that exists on Earth, and it’s scalable to levels that none of the other energy sources is. If we need to roll out petawatts’ worth of fission reactor capacity. we know how to do that. Seeing as turning the carbon we’ve dumped into the atmosphere into solids in time to matter for us as a species will require those petawatts’ capacity, it’s a wonderful thing. What it isn’t is intermittent. https://en.wikipedia.org/wiki/Nuclear_power_proposed_as_renewable_energy

      1. Uh… what?

        While *terawatts* of generated power isn’t a big deal for Earth’s overall heat balance,*petawatts* of additional heat generation is a *completely* different story. Even a single additional petawatt dumped into the atmosphere would likely pump things by a good fraction of a degree. And even if you assume carbon capture’s totally efficient (all power goes into carbon fixation) – which it isn’t – nuclear plants would generate twice as much waste power as electrical generated. Which would be a *big* challenge, and certainly not what any of our current plants do.

  5. after reading this article i still had questions, so i looked them up. i wanted to know how you use fast neutrons, when they interact so poorly with traditional LWR fuel. i was wondering if there was a neutron reflector or something. it looks like what they do instead is highly-enrich the fuel so that it reacts anyways. breeder reactors start out with highly-enriched fuel and then add a small quantity of non-enriched fuel which is then transmuted into something as reactive as pre-enriched fuel. i’m not clear if this proposal is a breeder reactor or not.

    so basically the problem is that it requires expensive and complicated fuel management, which seems like it would produce its own waste stream.

    1. Yeah, the 1960’s called: They do not, under any circumstances, want their alkali metal cooled breeder or molten salt thermal storage technologies back.

      It makes it sound like replacing water with sodium gives the neutrons magical properties. It’s more that if you enrich the fuel 5 times higher, and swap the water for something much less safe, you can run in a less stable regime with higher neutron efficiency. It is a breeder, but the plan is to keep the fuel in and hopefully burn up some of the byproducts and as much of the fertile (it’s not fissile) U-238 as possible. The goal is reduced reprocessing and waste.

      We are 50 years on with material science. Also, maybe this thing isn’t as politically toxic as it was.

  6. None of the systems are going to fly, because it’s too easy to make fissionable radioactives with them. Either for direct nuclear weapons, or toxic and radiation enhanced conventional explosives.

    I often wonder whether efforts like these are meant to make the founders wealthy well leaving a great many investors in the hole.

    1. It’s not an openly exportable technology (though deals can be made) but if we can develop this for the US and some EU countries then China may develop their own version (or maybe copy our design via IP theft). Dangerous or not, we badly need to reduce emissions and this could be what is needed to do that.

        1. please start a list of people (households really) that want the same. If there’s a windless night, you’ll be the 1st to be disconnected to keep the grid from failing.

          Renewables fail to provide stable power. Batteries are NOT a solution, not on the scale that would be needed. At this point even 50% renewables in the mix is unattainable, not without repeated large scale blackouts.

          Nuke plants are clean if you give them a chance to be.

          1. “Windless night” assumes that the only sources of wind power are local. This is generally not the case, there are many on a regional grid. By the way, the Texas problem wasn’t due to wind, but to cold temperature shutting down _all_ modes of power production, no mode had been prepared for it.

          2. Not really. The US grid is not like the UK national grid that can shuttle power from wherever to wherever.

            The US grid works more like a bucket chain, where adjacent areas supply each other to push power down the line. This is because it’s very inefficient to transmit power over many hundreds of miles. The average transmission distance from a power plant to a consumer is within 200 miles. Even if Texas was connected to the neighbors, the demand right across the borders would be equally high and there would be nothing to spare for Texas, because there wouldn’t have been enough transmission capacity within the neighboring states to supply that power from elsewhere.

          3. > but to cold temperature shutting down _all_ modes of power production

            80% of the nuclear power capacity stayed online.
            80% of the wind power capacity went offline.

          4. (Damn the HaD comment system – it seems it ate my comment. Grrr.)
            Sorry to say this is pure and simple FUD.

            Of course load shedding is a risk in mismanaged grids. However, done properly it’s not a problem, also not long-term. This is not some arm-chair expert opinion either, but it’s being implemented in real-life right now.

            Germany has had a 45.4% renewables fraction in 2020 [1], and there have been no load-shedding events leading to wide-spread power outages as you predict [2]. This is despite Germany’s grid not actually being so well optimised, the NIMBYs over here have been blocking much-needed new north-south HVDC lines connecting the off-shore wind parks of the windy north to the industrial centres.

            The problem these days is actually the polar opposite: there have been times of significant renewables over-production that exceeded not only demand but also export capabilities. This led to negative electricity prices, which sounds great but usually doesn’t lead to you being paid to turn on the washing machine. It rather distorts the energy market in many problematic ways, some of which though are connected to Germany’s renewable energy incentive schemes [3].

            The rising electrical vehicle production will mitigate this in the future, as LOADS of battery power are connected to the grid. It’s not even necessary to feed the batteries back into the grid (possible but the technologies currently rolled out can’t do this), even just a adaptive pricing scheme incentivising charging your car in off-peak/high-supply times and avoiding peak-load/low-supply will help a lot to manage the load. Cars and chargers rolled out now already could do that.

            All that said: I agree nukes-done-well are not the devil’s work people, in particular here in Germany, make it out to be. The problem is for mainly political reasons we stopped developing nukes-done-well and are stuck with current technologies without a long-term solution for waste management. However even with this caveat, Germany quitting nuclear head-over-heels was a big mistake, as solving climate change is critical on much shorter time-scales.

            [1] https://www.erneuerbare-energien.de/EE/Navigation/DE/Service/Erneuerbare_Energien_in_Zahlen/Zeitreihen/zeitreihen.html
            (Government website with open-access statistics. Reports are also available in English)
            [2] own observation from non-thawed fish in the freezer after multiple “windless nights” here in Germany
            [3] https://energypost.eu/negative-electricity-prices-lockdowns-demand-slump-exposes-inflexibility-of-german-power/

        2. Although not as bad as fossil fuel, renewables do have some bad problem with emissions, after all, aluminum for the eolic tower don’t come already processed from mother earth and silicon processing for solar panels is a pretty nasty proccess that can do more harm than good. Solar has it worse, since panel eficiency decay with time, and pretty fast. CO2 reclamation is a pretty good candidate to help reverse already changed climate, but renewables aren’t mature and reliable enough for what we need.

          Fusion might be after all, all we need, but still miles away from maturity. Renewables have the downside of being subject to local conditions to be disponible, and even if they can surpass demand during peak generation times, there’s no good storage disponible. Fission, radioactive waste, radioactive explosion danger, slow reaction to grid demand changes.

          1. Aluminum, glass, and doped silicon are readily recycled into new panels, and the energy cost of fabrication generally is paid back within 4 years while modern panels last 25 years. Modern panels don’t degrade so fast, either – most new ones guarantee at least 90% of yield after 25 years.

          2. Another unsolved problem with renewables is just what to do with turbine blades once they’ve reached their EOL. The current method of “out of sight out of mind” isn’t sustainable (they literally bury them here in the US Midwest). Apparently the bird problem is solved just by painting one blade black. But there’s still a political cost. These things aren’t silent, and there’s legitimate complaints about their constant rhythmic blade noise from those living near them. Some don’t mind, but there’s plenty that do. Large wind farms also alter the wind patterns to the lee and no one knows precisely what that means for regional and global wind patterns.

            I’m aware we as a civilization must do something to manage climate change, but we can’t be going into solutions blindly as if they were our saviors without understanding and, if necessary, mitigating the problems they cause as well at the same time we embrace those technologies. Otherwise our grandchildren will not only damn us for fossil fuels, they’ll damn us for destroying the environment while trying to fix the environment blindly.

      1. I don’t think export is really the issue. It’s more a matter of having very many sources of fissile or bio-absorbed radioactives all over our own country. So many that it’s pretty much a sure thing that some will fall into the wrong hands.

    2. Molten salt reactors put out certain gases we’re not allowed to mention, which results in contamination of everything they contact. That’s an unsolved problem of all these designs.

    3. For toxic dirty bombs it really doesn’t matter at all what radioactive source is used, and there are a vast number of options there, some relatively available, and all will do the job. And in many ways chemical assaults are better – no need for massive shielding to make it safe and smuggleable, and for many toxic chemical gasses they can be distributed violently by the same chemical process that made them (and can be made from many common chemicals too)..

      As for the refining element, big deal – just because it could be a nuclear weapon doesn’t mean it will be, there are other uses beyond making things turn to glass violently, and a nation only wants to maintain so many warheads, its expensive and unnecessary…

      And the potential for misuse doesn’t and shouldn’t mean we can’t use such technologies – by that argument your basic fertiliser, diesel and petrol should have always been outlawed, or at the very least never let out of highly secure facilities – as they can make a real mess if you choose to make them do so, and unlike radioactive material are difficult to track and trace the source of, so any abuse might well go unpunished – and the threat of a violent, bloody, pointless death for you and all your loved ones when you get caught is a pretty good motivator to keep a lid on anything that easy to trace – just give your proxy war terrorists some AK’s and IED’s…

      1. There’s a pretty clear difference of scale between fertilizer, diesel, and petrol, AKs, and IEDs vs. a fission bomb, or even a chemical bomb with bio-absorbed radioactives.

        1. Don’t disagree, but a fission bomb won’t be used outside of WWW3, nor will the rarer nasties a reactor can create – its all too easily traceable, and nobody would take that risk, even one insane nutter in charge isn’t going to get themselves and everything else around turned to glass. Where readily available radioactive stuff can be.

          The point being new reactors are not a major threat to world stability, won’t make a blind bit of difference to world in that sense as there are already enough WMD’s in the world more are not needed… Depressing as that is.

          1. Unfortunately man has time and again proven that he really is just a glorified hairless ape. There will always be nutters more than happy to die for a cause. Agree that fission devices wont likely become an issue, but, making dirty bombs is trivial if you have access to radioactive materials and suitably brainwashed volunteers (seems to me that this type of Sodium reactor has plenty of various isotopes in high concentrations, heck, just solidifying some of the fuel containing sodium and storing it in oil until dropped into a bucket would make a minor but functional dirty bomb).

            Imagine 5 dirty bombs going off during new years eve in New York in the most densely packed locations. The psychological blow to victims and their loved ones would be staggering. Not to mention the bystanders exposed to radiation by inhalation and exposure to radioactive casualties. Luckily it wouldnt take many such terrorist attacks before neutron monitors would be installed in all public spaces in major cities.

          2. Very true Antti, if it happened it would be awful, but its not hard to make it happen now if you really want to, there is a great deal of radioactive stuff even in the off the shelf civilian world… With all the Nuclear Physics labs, industrial processes etc there are yet more sources of radioactive stuff. Its not hard to get radioactive stuff as it stands, so a radioactive dirty bomb could be done now easily enough… Having yet more sources really won’t make much odds, and being a more highly watched and regulated industrial use getting at this source should be harder..

            The hard part with a dirty bomb isn’t getting the radiation source, or even an explosive to distribute it. The hard part is building it without killing yourself too soon, moving it without setting off radiation detectors, or needing masses of shielding. Its just not worth the effort when a chemical attack is about as deadly, probably actually more so, and in many cases common products can just be mixed to create their own rapid and toxic gas generation reaction, so you don’t even need to distribute it by explosive – Its safer for you, easier to transport, can even be assembled at the attack site and will be more than unpleasant enough for the scumbags to beat their chests and claim a victory…

  7. The basic problem of molten salt reactors still remain unsolved: they put out radioactive Xenon gas.

    Xenon is a neutron poison that slows the reactor down. In a molten salt reactor, Xenon is continuously “sparged” out by bubbling helium through the molten salt, which is part of the reason why they can burn the fuel completely – but it also means you get a steady stream of radioactive gas leaving the reactor. The Xenon further decays into radioactive Caesium and Iodine which are the most troublesome parts of nuclear fallout because they’re readily bio-absorbed and accumulated. As a gas, Xenon gets everywhere and radioactively contaminates everything it contacts because it has a short half-life of just a few hours.

    So where do you put it?

    1. The natrium reactor is not a molten salt nuclear reactor. It is fueled by solid rods of uranium.

      The solid uranium rods heat the coolant (molten sodium metal).

      The coolant is cycled though a heat exchanger, where it heats molten salt, which in turn goes nowhere near the radiation.

      The molten salt is used for thermal storage, or for thermal power generation.

  8. every sodium or NaK alloy cooled reactor has had problems with coolant leaks quickly turning into localized fires. Not sure I want to be around a place that stores literal tons of molten sodium…

    1. If I remember the Wikipedia article correctly, when reflecting neutrons, the heavier the atomic nucleus, the fewer collisions needed to slow it to thermal neutron speed.

      So, I’d assume that heavier atom’s are worse neutron reflectors when used in a fast neutron reactor.

      I’d also assume that resultant isotopes and their decay products play a factor.

    2. former soviet union/Russia built a few lead-bismuth cooled ones…namely the Alfa class nuclear subs in the 70s and now they should be finishing a 300MW electrical output testing one in Tomsk. This will be a precursor to a 1.2GW electrical one…
      There are substantial material and engineering challenges to using lead.

      btw the Alfa class were the hot-rods of nuclear subs, capable of sustaining an insane 41 knots while submerged, fastest subs ever built to this day. All this because of the much more powerful and yet more compact and lighter reactor.

    3. I think that one of the daughter products would be a mercury vapour, but since it is a gas I’m sure that could be removed by a cold trap (or distillation of some kind). I guess one worry might be a mercury amalgam forming with other daughter products inside the pipes potentially leading to one or more solid plugs of metal forming inside the cooling system (think of density mercury amalgam fillings) I guess you could switch to a backup cooling system when required, and then flush the offline cooling system and refill it fresh clean, radioactively cold, newly mined/recycled lead.

  9. I like the idea of this. Though there is a caveat that the efficiency will be lower for this system when the temperature of the coolant is lower sue to pulling power from the storage. But all the time it’s full, max temp could be used (given perfectly insulating asbestos substitute). More power plants should have huge vats of super hot sodium kicking about for the benefit of us all.

    Have long thought anything with a turbine should have a mandated flywheel stuck on the end to add to grid stability. Brute force is good.

  10. The Fast Flux Test Facility (liquid sodium test reactor) ran successfully at Hanford WA from 1982-1992 to accumulate detailed data on how they work, and to solve engineering challenges. We have a huge worldwide experience with liquid sodium reactors and they can be built to run safely and efficiently.

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