What Is a Nuclear Microreactor?

https://www.energy.gov/ne/articles/what-nuclear-microreactor

by rbanffy • 5 years ago

134 180 5 years ago

I watched a video about the economics of nuclear reactors and the main focus was that the time it takes to break even is much longer for nuclear reactors if compared to coal and natural gas. Couldn't something like those microreactors solve that problem?

pydry• 5 years ago

In theory but they're still vaporware.

economusty• 5 years ago

That's the goal smaller safer and economies of scale, PowerPoint size reactor complexes are rarely built and are one off designs with high level similarities.

Symmetry• 5 years ago

The main issue is that the first thing you have to do is secure your financing then you're paying interest on your loans over the near decade it takes for the regulatory approval apparatus to do its thing. If this allows you to get approval for a one reactor site with the right to expand to 24 more reactors of a given design without re-approval it might be very significant.

ansible2• 5 years ago

The other issue is that each nuclear reactor site is effectively unique. So there's whole piles of paperwork that need to be checked and re-checked to ensure that all procedures and everything is correct and up-to-date.

With small modular reactors and similar, all the critical bits are made on a production line, and completely standardized. This will drastically reduced the paperwork and training needed to operate it safely.

baybal23• 5 years ago

Couldn't something like those microreactors solve that problem?

No, they will actually make the problem worse.

Maybe it was a somewhat valid idea 40 years ago, but bot today.

jedberg• 5 years ago

I wonder if it would be feasible for a neighborhood to get together and get one of these for everyone to share. In theory 1MW powers about 400 homes. Or for a new development to put one in and tout "free electricity for 50 years" as benefit of the development.

Or a condo complex getting one with their condo fees.

So many possibilities.

Gracana• 5 years ago

I can just imagine going to that HOA meeting:

Here's the plan for the reactor installation. Does it look good to everyone?

Yes.

Okay, next item: What color shall we paint the bike shed?

wmf2• 5 years ago

No, you have to use up the whole meeting with the bike shed then slip in the nuclear reactor at the very end.

mmaurizi• 5 years ago

This is a great model, because then the neighborhood can use the reactor waste-heat for district heating!

drran2• 5 years ago

And they can use it for hundreds of years! With time, every home can get it own waste reactor with waste heat for heating!

Future is here, it just unevenly distributed.

godelski14• 5 years ago

Which is actually really important because heating and cooling are big contributors to climate that aren't as obvious as electricity and transportation.

kube-system• 5 years ago

I think the more immediate use cases will be industrial. These sound like exactly the power requirements of a data center.

godelski14• 5 years ago

Combine it with the data centers being placed under water. Now you got a big heat sink too.

pdoconnell• 5 years ago

There's actually interesting issues with how property paid for through mortgages are impacted by nuclear regulations. I recall something deep in my mortgage about how (I think) the nuclear regulatory control act placed restrictions on local use vis a vis nuclear energy.

lwhi17• 5 years ago

Why do people not get as excited by the prospect of renewable energy?

sthnblllII3• 5 years ago

These compact reactors will
smaller design concepts will
Most designs will

Sounds like these are goals not accomplishments.

rocqua• 5 years ago

Are they hinting at e.g. the option of using these for a similar blackout to the recent Texas one. Just ship in as many of these "on demand" and handle momentary demand spikes.

NortySpock2• 5 years ago

An adequate on-site water supply to boil for the turbine is probably going to the limiting factor for "mobile microreactor" designs

ceejayoz• 5 years ago

The infographic indicates the installation turnaround as weeks/months, so it wouldn't work in those scenarios.

NortySpock2• 5 years ago

"1-20 megawatts of thermal energy"

Large reactors are usually 4GW thermal power converting to 1 GW electric, so you're going to get, I don't know, 10%-25% electrical conversion efficiency out of this, so 0.1MW to 5MW of electrical power.

On the plus side you can probably dual-use this to run communal home heating systems, maybe even hot water.

It'd be great for cold-climate towns (or space-colony applications) provided you can get some funding together.

endymi0n• 5 years ago

...which plays in the same league as any large and modern wind turbine.

Minus the proliferation risk of somebody stealing this comparatively small reactor and builds a dirty bomb with it - oh, and you still have to dismantle it and store safely for millenia after use.

No, thanks... looks to me like nuclear is dead in the water.

ArkanExplorer• 5 years ago

A wind turbine doesn't spin 24/7. You'd need a Wind Turbine + a very large battery.

The waste heat from a mini nuke is also perfect for district heating.

throwaway8943452• 5 years ago

Minus the proliferation risk of somebody stealing this comparatively small reactor and builds a dirty bomb with it - oh, and you still have to dismantle it and store safely for millenia after use. No, thanks... looks to me like nuclear is dead in the water.

The proliferation risk seems like a valid concern, but that we have to store radioactive material for millennia isn't a valid criticism of nuclear in general because we already have to store nuclear material and the costs associated with storing more waste are marginal (if you can safely store a little nuclear waste then you can safely store a lot of it).

zackees2• 5 years ago

minus the proliferation risk of somebody stealing this comparatively small reactor and builds a dirty bomb with it

Using that logic, we should stop production of ammonia fertilizer.

and you still have to dismantle it and store safely for millenia after use.

The fact is that the entire worlds nuclear waste can be contained in about one swimming pool, which can be placed in the middle of a mountain or some other geologically stable area. You can't say that about coal, or wind (junk turbines that can't be recycled), or solar. The death rate per terawatt-hour of generated nuclear is far less than any other fuel source.

The idea that Nuclear is a dead end has been made popular by pop culture from the 1970's and bad science driven by an agenda to keep everyone on a globalized fossil fuel monopoly run by the military industrial complex.

Deaths per terawatt-hours comparison chart: https://www.statista.com/statistics/494425/death-rate-worldw...

ChuckMcM6• 5 years ago

Hey we know what is going to be the hot product to buy for bitcoin miners :-)

I was thinking about data centers (20 - 50MW) and a "farm" of them to provide N+1 redundancy would be an interesting thing. 99% carbon neutral as well.

rthomas62• 5 years ago

This goes along with the coronal mass ejection risk story that was on the front page a day or two ago. Is a nationwide electric grid even a good idea anymore? Yes, it's more efficient, but it's also more fragile, in that a failure in critical infrastructure can cause nationwide blackouts.

Imagine if most places had a microreactor, a small fossil fuel generator, renewable + storage, or some combination of these, and each small to medium sized community of homes had their own. Things would go wrong all the time on the small scale, but there would be no such thing as a nationwide blackout.

notJim• 5 years ago

This is interesting, because usually I see nationwide grids being touted as MORE resilient, not less. The idea is if power is knocked out in one area, you can still get it from elsewhere. This came up a lot during the Texas situation.

rthomas62• 5 years ago

Texas is what I would still consider a "nationwide" power grid. I was thinking of something very very decentralized, like individual neighborhoods. It wouldn't completely solve what happened in Texas, but blackouts would be contained to small areas for hopefully shorter amounts of time, as failure in one area would have no effect on other areas, and individual neighborhoods could probably coordinate and conserve power usage as needed better than an entire state.

godelski14• 5 years ago

I think there's a balance. You want a slight surplus in your local area and connected so you can pump it somewhere else when that somewhere else goes down. Though IIRC Texas has far more problems than just not being connected (also far more than just renewables either, which was a big talking point).

wmf2• 5 years ago

Smaller grids like Texas are more susceptible to weather events though.

thereare5lights• 5 years ago

Are there examples of how a failure at a power plant could affect the national grid?

As mentioned by another comment, one advantage of a national power grid is the ability to transfer power from other places during power failures. But I'm not sure how a power failure would affect the rest of the grid.

akiselev• 5 years ago

Are there examples of how a failure at a power plant could affect the national grid?

A failure at any single power plant is very unlikely to cause cascading failures in the rest of the grid because one power plant usually can't generate enough power relative to its grid.

Gross oversimplification but all of the power plants in a national grid are essentially coupled together [1] as a giant circuit made up of a ton of electromagnets - the generators converting coal/natgas powered steam or water/wind to electricity. These electromagnets are all operating at the same frequency in phase with each other which literally means that the generators spin in sync at ~60hz. These generators are often (usually?) heavy turbines with a lot of angular momentum so normally when you connect a power plant, it stays in phase just due to the sheer inertia of the rest of the grid because power follows phase [2].

When the phase changes suddenly - like when connecting a generator that is out of phase with the grid - all that inertia of the generator essentially slams into the electromagnetic force generated by the incoming current. If the rest of the grid (of hundreds/thousands of other generators) produces significantly more power, it'll just destroy the connecting one as if you brought a turbine powered jet engine to an instantaneous dead stop - the momentum of the blades will literally rip them off of the shaft. However, if the newly connected generators are producing a significant amount of power relative to the rest of the grid, like when a corona mass ejection hits or a large islanded subgrid is poorly reconnected, the resulting differential can generate a wave (again, gross simplification) that travels through the grid with enough power to destroy every single generator connected to it.

A single power plant just can't generate enough power to do damage to the rest of the grid [3] but if a natural disaster severed the connection between two regions of a grid and they drift out of phase, they must be carefully reconnected because they might have enough power to seriously damage other power plants.

[1] Some parts of a grid might be separated by HVDC which in effect isolates the parts

[2] Power flows from the faster generators to the slower ones, speeding them up until they hit equilibrium.

[3] There are exceptions depending on grid topology, but generally grids are designed to avoid them

epistasis• 5 years ago

A better national grid for renewables will be hugely redundant, with few single points of failure, because renewables are distributed throughout geography.

If something takes out that sort of infrastructure, it's probably going to take out the local micro reactor too.

Existing solutions for micro grids are getting super cheap too, if we didn't already have tons of transmission built out, starting a grid from scratch today would probably include not only far less transmission, but far more storage, which also hugely increases resiliency.

Having tons of storage and solar right behind the meter, by which I mean 10%-40% of buildings, would hugely increase the resiliency of the grid, if utilities would embrace the Information Age build bottom-up infrastructure in addition to top-down.

Terr_• 5 years ago

IANAElectrician, but IIRC the biggest problem isn't the grid size per se, but how grid operation requires always matching the amount of power coming from all producers and the amount being used by all consumers. Like a tightly-sealed water-pipe system where the pressure is uniform throughout, and too much pressure pops things, while too little won't go anywhere.

So it's a coordination problem, and ideally you'd have a big-grid which can be arbitrarily partitioned (and recombined) to ensure producer-consumer matching as you get more and more of each involved again.

It's one of the few cases where the phrase "smart home" doesn't make me cringe: Imagine a neighborhood of houses in a brownout situation all coordinating to dim the lights and space out their high-energy usage, like running refrigerator compressors.

Animats• 5 years ago

Sounds like a TRIGA reactor.[1]

Those work fine, but are not cost-effective power sources. They're more for isotope production.

There's a Russian reactor in this category, the RITM-200.[2] It's a land-based version of their current generation icebreaker power plant. This is one of the very few "small modular reactors" that actually exists. There are about 30 proposed designs.

Here's the first real power reactor in that category. From 1957. [3]

[1] http://www.ga.com/triga/

[2] https://en.wikipedia.org/wiki/RITM-200

[3] https://archive.org/details/FirstPri1957

amelius• 5 years ago

Are these reactors also used in nuclear-powered submarines?

baybal23• 5 years ago

Yes, the smallest one in existence is a submarine reactor once designed to power underwater spy gear

mikewarot2• 5 years ago

What if we socialized production of these, turned them out in quantity, to be owned and monitored by the Department of Energy, in order to increase national security.

giantg22• 5 years ago

How would that increase security?

andrewljohnson• 5 years ago

I think the parent comment is saying we are dependent on foreign oil and this will alleviate that.

mikewarot2• 5 years ago

By distributing the production of electricity more evenly across the grid, preventing large scale outages, and reducing our need for fossil fuels.

Teknoman117• 5 years ago

Made me think of a seemingly abandoned LLNL project for what is in effect an autonomous breeder cycle reactor that serves as a 30 year 100 MWe nuclear battery.

https://en.wikipedia.org/wiki/Small,_sealed,_transportable,_...

shadowgovt• 5 years ago

... a miserable pile of secrets.

stuff4ben• 5 years ago

I for one would love a molten salt reactor in everyones backyard. https://www.forbes.com/sites/llewellynking/2020/10/13/new-de... Maybe a scaled down version that could be deployed in communities thereby decentralizing electrical generation and distribution.

ChuckMcM6• 5 years ago

I'm pretty excited about these. It takes nuclear in a new direction. What disappoints me though is that of the people doing this research that I've contacted, none of them are reaching out to the "other side" (things you would pump the heat into) here. A packaged closed cycle steam turbine system for electricity generation, for example, would be an excellent add-on here.

The Navy has some great small turbine systems (although they typically use the ocean as a big thermal sink for their re condensers), and the folks who design geothermal plants could have a role here if they wanted, but so far not much work there that has appeared in the sources I tend to scan.

As a result I'm concerned that these things with hit the market with no "shovel ready" plans to put them into production, and the lag between that and when you can put them in production will kill the reactor developers. I have seen it in other industries and it hurts to watch it unfold.

semi-extrinsic• 5 years ago

OTOH, power generation from industrial waste heat is an increasingly hot topic these days. Whether steam turbine or organic Rankine cycle, finding something compatible in the 1-10 MW scale should be quite straightforward.

sroussey• 5 years ago

https://www.radiantnuclear.com/

ChuckMcM6• 5 years ago

I like these guys but get annoyed at the 1kWH == 1 Typical House. While a case can be made that over a 24h period a house may consume 24kWh the fact is that "typical" houses burst to anywhere between 5kW and 10kW depending on appliances (AC + Freezer compressor + Oven baking a roast and boom you're at 10kW) As a result if you hook a thousand houses to a 1MW reactor you're going to get a crap ton of brownouts.

lwhi17• 5 years ago

I've just read through the comments, and can't really see anyone else making this point .. so I'm assuming it will be unpopular.

Why is nuclear the silver bullet that will save us?

Logically, renewable and storage on a microlevel seems to make more sense.

With nuclear .. no matter how advanced the tech is now, I can't see how we're not robbing Peter to pay back Paul.

The waste will be around for longer than we are. We have no solution other than 'lock it up'.

Accidents do — and most like will — happen. How will increasing the volume of reactors not increase this risk?

sparker72678• 5 years ago

I think it's more akin to putting out a structure fire with water. You stop the immediate threat and save lives and some property.

And while some property damage will result because it's all getting soaked, it's still better to have something left than nothing, and while an un-burnable building would be nice, it doesn't exist yet.

whatshisface• 5 years ago

Qualitatively, every choice is equal, because a qualitative argument can't distinguish between a big problem plus a small benefit and a big benefit plus a small problem. Quantitatively, you can make rational decisions. So, the answer to your questions are, "how much will building more reactors increase the accident risk," and "how much nuclear waste will be produced in the course of normal operation?"

godelski14• 5 years ago

Why is nuclear the silver bullet that will save us?

I'm not sure many people make this argument. Although the people that do are very vocal. But they are wrong. The general consensus around nuclear is that it adds to the number of solutions we can use. Considering the inhomogeneous nature of climate and regions nuclear may have advantages in certain areas, whereas other areas it may be unnecessary. Anyone claiming "one size fits all" is just selling snake oil. Essentially the argument comes down to "why time one hand behind your back when trying to solve an extremely important and challenging problem?"

As for waste, it isn't as big of a deal as you might think. Though this is more difficult to understand without an expertise in the subject matter. Mostly this is due to the complexity of understanding the different types of waste, amounts, and the vastly different levels of radiation in those waste products. Most of these conversations are akin to people talking about rocket science without knowing Newtonian mechanics. Just listen to the experts and see what they are saying. You're on HN, so I trust you can understand the nuance that scientists use, though I know that sometimes this can get confusing to the public. Like how "disagreement" isn't much of a disagreement but more quibbling over minor details.

ChuckMcM6• 5 years ago

Why is nuclear the silver bullet that will save us?

Because you can generate power without adding CO2 to the air, or other pollutants. It works 24/7/365 and it requires no new "science" to produce.

However, the root of your question appears to me to be founded in some misconceptions you have about nuclear power. It isn't uncommon because the information in most popular press articles about nuclear power is over 50 years old.

To put that in perspective, imagine arguing the utility of an electric car when your data point is gas at 30 cents a gallon (the price in 1965[1])?

But to talk about nuclear power with current data about how you would design a power plant (and these are the new designs we're talking about), the risks of them leaking any radioactivity, and the risk to people should that radio activity leak and it makes our decision to keep building fossil fuel plants look pretty stupid. It really does turn the whole question on its head.

Nuclear is demonstrably cleaner, safer, lower risk, and potentially lower cost (although how do you price the cost of destroying the planet right?) than any other baseload technology. It even surpasses hydroelectric in terms of externalized costs of habitat destruction.

But I recognize that if you base your analysis on an idea that any new nuclear plant would be identical to the ones at Fukishima (built in 1967) or Chernoybl (built in 1972) it does seem odd that we would want more of that.

[1] https://www.energy.gov/eere/vehicles/fact-888-august-31-2015...

Ericson23142• 5 years ago

The other replies handle the large issue now, but let me go point by point.

Why is nuclear the silver bullet that will save us?

Not supposed to be that, as others said.

The waste will be around for longer than we are. We have no solution other than 'lock it up'.

If we sacrifice a Cubic mile to save the planet that's a god trade. Paul is a lot bigger than Peter here.

Accidents do — and most like will — happen. How will increasing the volume of reactors not increase this risk?

The Tsunami was far worse than the meltdown; I am afraid people's fear-memory often conflates the two. I'm willing to admit the official stats with Chernobyl might be a coverup, but still, tons of poor people around the globe get sick or die from perhaps-illegal fossil fuel pollution. It's not a worse coverup than environment justice issues in the US.

The annoyance here among pro-nuclear people is that other thing's problems get to slip underneath the radar, but nuclear's don't.

storage

Consider storage will require tons of lithium. The ecological damage from that mining will also be catastrophic, and the ecosystems might take as long to recover.

I'm not saying we shouldn't do lithium-ion batteries. We have little choice we're going to need more. Same thing with nuclear. Same thing with not decommissioning dams as soon as we like.

The fact is with all routes, avoiding ecological collapse will cause local environmental issues. What irks people is the singling out of nuclear, as if other things didn't have issues too, and other essential systems (like top soil) repair as slowly as some radioactive isotopes degrade.

parineum2• 5 years ago

Many view fission as a stop gap to fusion. I also think the scale of nuclear waste is vastly over estimated by the general populace.

Generally, it produces very little waste in terms of spent fuel[1] and much of that can be recycled. That does require building newer, modern reactors though.

The waste will be around for longer than we are. We have no solution other than 'lock it up'.

This is another thing that people don't really understand. Radioactivity is viewed as a monolith in pop culture. There's a perception that a radioactive thing will kill you in thousands of years. In reality, the length of time that something is dangerous is inverse to how dangerous it is, ie, the longer it's radioactive, the less deadly it is (and vise versa). Plutonium-239, the long term radioactive byproduct (24,000 years) is not that deadly [2] compared to the much more radioactive cesium-137 and strontium-90 which both have a half life of around 30 years [3].

1. https://www.energy.gov/ne/articles/5-fast-facts-about-spent-... 2. https://en.wikipedia.org/wiki/Plutonium-239#Hazards 3. https://www.nrc.gov/reading-rm/doc-collections/fact-sheets/r...

belorn• 5 years ago

Logically, renewable and storage on a microlevel seems to make more sense.

For northern countries where wind is the primary renewable sources, there does not exist any clean storage that is currently deployed and getting investments. The current "storage" being combined with renewable are fossil fuels, primarily oil and gas. The subsidize for energy stability goes to fossil fuels, the investment for bigger reserve capacity goes to fossil fuels, the national energy plan here in Sweden as an example is fossil fuels for stability and renewable for cheap production.

Lithium batteries as an example are great when the charge cycle and capacity is measured in hours, like for solar. It works, it is cost effective, and it helps reduce the dependency on fossil fuels. For wind you have charge cycles measured in weeks and capacity demand that can last months.

There are a few experimental project (likely heavily subsidized, and none that I can find that operate on buying wind power and reselling it weeks later), but the flow of money goes very distinctly towards fossil fuels right now. Nuclear provide at least an working alternative, and the occasional accident is a much better future than the non-accidental climate change that is occurring right now.

That said, I would prefer if we simple banned fossil fuels as a strategy to provide gird stability and forced the market to decide on storage vs nuclear.

ska3• 5 years ago

Logically, renewable and storage on a microlevel seems to make more sense.

Only assuming technological advances are made that we can't count on. Current day we don't have storage solutions that will do it, and most micro stuff doesn't work well enough to meet current demand anyway....

LargoLasskhyfv2• 5 years ago

There is no waste! Our descendants will regard it as magic/mysterious cultural heritage of long forgotten times, much like we do view the Pyramids of Giza today.

Think of all the opportunities, the tourism...

sthnblllII3• 5 years ago

All excellent questions, these should be addressed every time nuclear is considered.

I'm not sure existing nuclear is all that competitive with renewables+storage, but better designs absolutely could be. Better designs also wouldn't produce long-lived waste, and could also transmute existing long lived waste into short term. This will require R&D.

Increasing the number of wind turbines increases the risk of collisions with aircraft. What level of risk is acceptable to you? That's the question, not "will there be any increase in risk at all".

lgats• 5 years ago

Would these types of systems not be great for drop-in replacements in natural gas electricity generation facilities? Much like natural gas can replace coal through a plant upgrade.

viernullvier• 5 years ago

Not in its current iteration. The biggest advantage of natural gas generators is the possibility to ramp them up and down quickly, making them an ideal choice for peaker plants or load following. For nuclear, on the other hand, the options for throttling the output are quite limited - both physically and economically.

As a mitigation, combining them with battery storage would be an option, but then again it would still be cheaper to use wind or solar instead of nuclear as the source of energy.

instagraham• 5 years ago

"Most designs will require fuel with a higher concentration of uranium-235 that’s not currently used in today’s reactors"

The problem with making such tech mainstream is you'd need impossible levels of security to prevent even one store of such material from being stolen.

doikor3• 5 years ago

Some of the designs are not made to be refueled. In those the fuel gets loaded in at the factory and sealed up. Though in that case they are loaded up with quite a large amount of fuel (like a couple tons of plutonium for a ~30y lifespan)

In such designs you really would only need high security at the factory as stealing fuel from a reactor that is not meant to be opened (you would have to cut into it) and that is on without someone noticing is really really hard.

edit: Would also like to add that such designs are not actively being pursued anymore. The tradeoffs just are not worth it. We know how to securely transport fuel around so that is not that big of an issue really.

nradov2• 5 years ago

That doesn't really reduce security requirements for the reactor itself. It just means you don't have to secure additional fuel in transit.

moralestapia2• 5 years ago

a couple tons of plutonium

Is that a typo? tons?

helmsb• 5 years ago

I once heard that stealing nuclear material from a reactor design like this was akin to stealing a lit bar-b-bq grill by hand. Not impossible but not very easy or practical.

phendrenad2• 5 years ago

My thought is, 30 years isn't enough. In 30 years you need to open the reactor and swap out the fuel, which is too tricky an operation (securing the fuel going in & out) to do cheaply and at scale. 30 years is within the lifetime of most people, so people are hesitant to cause a problem that they'll have to deal with. If these things can be buried in lead & concrete for 60+ years then maybe it'll happen.

AtlasBarfed• 5 years ago

Or with thorium breeding, fuel input is not a big deal, since thorium is pretty much not dangerous.

pjscott• 5 years ago

The micro-reactor designs I looked up generally fell into one of three categories:

1. Very high enrichment fuel because they need fast load-following, e.g. for naval use.

2. Very high enrichment fuel because they're for use in space, and lower mass is better.

3. Reactors for ordinary power use, with fuel that's enriched more than most, but still nowhere near enough to be practically useful for weapons.

An example of #3 is the Westinghouse eVinci micro-reactor, which uses fuel enriched to a little under 20% U-235. Weapons-grade uranium is closer to 90%.

godelski14• 5 years ago

People often confuse the difference in enrichment needed for weapons and reactors. Typically a reactor is 3% where a weapon is 97%. It becomes significantly harder to create that much enriched uranium which is why experts call Iran's production a bluff. Past their agreed levels, but nowhere near enough for weapons. The whole Iran deal relies on this fact actually.

nonameiguess• 5 years ago

Could make a dirty bomb still, but the risk from those is more psychological than real, which is probably why no one has ever tried to do it.

Manuel_D5• 5 years ago

What is the threat model for fuel theft? Weaponizing uranium requires enrichment well above even what maritime reactors use. Note that the difference between 90% enrichment and 99.9% enrichment isn't a factor of 1.1 difference, it's a two-order of magnitude difference - the remaining impurities need to be reduced by a factor of 100, each of those extra nines is another order of magnitude. And even if fuel does get enriched, it requires extensive nuclear physics research and engineering effort to produce a fission device. The only groups proven to be capable of this are state actors, which can set up their own enrichment facilities and have no real reason to steal uranium.

An alternative threat model is not producing a bomb, but dumping radioactive waste in a populated area. While damaging, radiation is a relatively slow killer save for the most intense doses. The amount of damage that it would be able to inflict is minimal relative to the amount of effort requires to break into a nuclear facility and exfiltrate fuel. The question that should be asked is, does this present a larger potential for harm as compared to the same amount of effort put into conventional means of destruction (bombing buildings, shooting up crowded areas)?

cryptonector3• 5 years ago

Enriching HEU to weapons grade is trivial by comparison to enriching natural uranium to even just 20%. Really, the difference in effort needed is enormous. Yeah, you still need centrifuges, but you need many fewer centrifuges and many fewer passes.

Also, you can make a bomb with uranium enriched to much less than weapons grade -- you'll just need a lot more of it compared to weapons grade uranium.

1970-01-01• 5 years ago

See also Small modular reactor: https://en.wikipedia.org/wiki/Small_modular_reactor

dbetteridge2• 5 years ago

So how many decades are we away from something like Naquadah generators?

Is this something that is even possible with our current fuel sources or would it require some currently unavailable fuel.

https://stargate.fandom.com/wiki/Naquadah_generator

azernik2• 5 years ago

Quite far - miniaturization of nuclear reactors is generally quite hard.

We haven't put much effort into miniaturizing terrestrial reactors, and naval reactors have other design concerns which limit, but space reactors are a good gauge of the state of the art. From the (production!) American SNAP reactors of the 60s and the contemporary (production!) Soviet BES-5s, to the current Kilopower design studies and prototypes, there's been basically zero progress in reducing size. Fission has some hard floors on reactor (and bomb) size, because of the logic of criticality.

That design floor for power reactors is quite large - the core itself is usually on the order of 50-75cm long by 20-30cm diameter, but the heat-to-electric conversion machinery and, more importantly shielding, will quadruple or quintuple that length.

And that's with the cheats enabled by space applications, where you only need to shield in the direction of the spacecraft. For general use a similar design would fill a shipping container, like the linked microreactors tend to.

Fusion is maybe a more plausible route to small power sources on the order of decades, because there's a clear parameter to tweak: magnetic field. Better superconductors -> stronger magnetic field -> smaller minimum size.

dbetteridge2• 5 years ago

I appreciate you taking the time to answer rather then just downvoting me :)

Sounds like pretty much what I would have expected in terms of limitations, so we'd need something much more energy dense (Like fusion) and a more compact way to remove the heat and convert it to power.

Enginerrrd• 5 years ago

Quite a few... The issue isn't so much on the nuclear side as it is the size of thermal energy recovery systems. Attempts to miniaturize turbines haven't worked super well, though they have been made since a bottle of fuel has a much greater energy density than most batteries.

NiceWayToDoIT• 5 years ago

Anyone info about the price per MW, availability?

korethr2• 5 years ago

So, do these operate on the same design principles as the various Gen 2 reactor designs that have been involved in nuclear accidents, e.g. Three Mile Island, or Fukushima? I raise this question not out of an anti-nuclear hysteria, but a wondering if the safety issues that seem inherent in those designs are addressed in these micro-reactor designs.

I'm not particularly worried about shutdown mechanisms, but more so about containment of decay heat after an emergency shutdown event. By my understanding, our current reactor designs still produce decay heat for a time after shut down, and that heat still needs to be dealt with. And it was this decay heat and the failure to control it that lead to the Three Mile Island and Fukushima incidents.

Decay heat isn't a concern for naval reactors because 1) they're much smaller than a commercial power reactor, with order(s) of magnitude less output, and 2) they have the ocean to use as a heat sink to prevent overheating. Micro-reactors probably also have the first advantage, with outputs ranging from 1-20 MW. However, 60-1200 kW is still not as easily shrugged off when you don't have an ocean to dump heat into. IME, 60-1200kW is enough to heat steel, if not to melting, to certainly a loss of strength, and that does give me some worry about damage to containment.

So I guess my main concern is thus: Are these things being designed to be able to safely shed their worst-case heat completely passively in an emergency?

If so, awesome, and I look forward to the possibilities these designs open up.

godelski14• 5 years ago

The shutdown mechanisms are specifically about the containment of heat. The problem is generally about a reaction not being shut off. Gen 3 and beyond reactors, which includes these, don't have these problem at all. But neither do Gen 2's, anymore.

But if we're going to talk about the 3 accidents, we should note that they are quite different.

Chernobyl was a positive pressure reactor. Only the Russians were ~~dumb~~interested in building these. Everyone else was afraid because their ability to explode and instead chose reactors that couldn't explode. The accident happened not just because of this, but because the xenon spike and not a great understanding of the science.

TMI had a bunch of things go on at once. Relief valve stuck open but indicating close. Not enough water during SCRAM. Turning off ECCS due to bad indications. Then the hydrogen explosion. Resulting in about a dental x-ray's worth of radiation for a limited number of people. We now have hydrogen absorbers and have upgraded reactors to ensure these events don't happen again. [0] (this channel also talks about all the events).

Fukushima was caused by the largest earthquake and tsunami ever recorded in the region (so lower bounding to 1k year event) and one of the largest ever recorded anywhere. The reactors were designed to withstand quakes and tsunamis. The tsunami and earthquake were much larger than anyone expected to ever happen in the region. Reactor got destroyed and it is hard to track where all the material went, which is why they have the region closed down (background radiation levels aren't so bad, but you don't want to risk consumption of reactor material. Similar to why the surrounding area of Chernobyl is closed).

The reason I bring all these up is because we should note that even Gen 2 reactors have been retrofitted with improvements from these events, and have been this way for a long time.

[0]https://www.youtube.com/watch?v=d0SCf0rxX4E

korethr2• 5 years ago

The shutdown mechanisms are specifically about the containment of heat. The problem is generally about a reaction not being shut off.

Indeed? I was of the understanding that the shutdown mechanisms were specifically for halting the chain reaction, and largely a solved problem with mature tech, and it was containing the decay heat of Gen 2 designs that was the trickier problem.

I am happy to be wrong about the latter, though perhaps not as happy to be wrong about the former.

ncmncm• 5 years ago

These could have been fielded at any time in the last three decades. That they haven't been may be a consequence that they offer relatively little scope for the wholly-legal institutional corruption that has driven nuke power construction throughout its lifetime in the US.

When construction costs are allowed to balloon 4x-10x over quoted cost, the great bulk of that amounts to a conduit from the public purse to private pockets over a decade or more. Projects where that is possible out-compete projects, for backing, that merely promise normal value for money spent. We see this dynamic not just in nuke projects, but in urban transit tunnels, military and manned-space procurement, fusion research, and abortive bullet-train projects.

That we do not see it in most current solar and wind power projects with, instead, costs plummeting well below anything than could ever be matched by nukes, may be a consequence of some combination of the projects' short terms, idealistic contractors, and dead-simple accounting. It will take decades to drive costs back up to where they will be good conduits for corruption. It remains to be seen whether hydrogen projects can be made to serve in such a role, but there is strong demand.

metalman• 5 years ago

Hydro power runs on water,best if its not all full of radiation so you can drink it. Wind power runs on air,be nice if it was a lot cleaner for breathing purposes and real bad if it was all nuked up. Solar power runs on light of a bright sunshiny day,unlike nukes with that deadly glow in the dark Nuklear scnooklear go away.

ska3• 5 years ago

Hydro power runs only where there is enough water moving. Wind power runs only when there is enough wind. Solar power runs only when it's sunny enough, and never at night.

Batteries are not nearly good enough to smooth this out.

So ... all these things are great, but not enough to replace fossils practically at current tech.

chigbo• 5 years ago

Am new

coretx• 5 years ago

This is a utmost clever and when well executed safe way of ditching the waste product from large nuclear powerplants in everyone his backyard. I remember reading about a japanese ( i think Toshiba produced ) microreactor some decades ago only to find out that it ran on ordinary decay and exothermic reactions. Actually nothing but a fancy battery that converts heat into electricity. Not a /reactor/ in the meaning that springs to mind when reading the word.

natmaka• 5 years ago

Nuclear has quite a few major perceived problems: bureaucracy/authoritarianism, uranium (fuel) reserves, capital-intensive projects, risk of accident, proliferation, waste disposal, real decommissioning costs...

One of them is the NIMBY effect, and it may be a show-stopper for such microreactors, which need to be produced in large batches in order to be affordable. I can't imagine how a sufficient amount of them will be accepted by the population. Even maritime underwater versions will probably be rejected.

What Is a Nuclear Microreactor?

Related Stories