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Comment by davidu | Hacker News Reader

There are a few startups pitching a "nuclear power station in a shipping container" idea -- and having heard them and done a bunch of reading about the state of nuclear, it's hard to not come away with a complete and strong belief that:

1) It's a really good idea.

2) Nuclear power, more broadly, is probably our best bet to quickly the tide against climate change.

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Nuclear is much more expensive than wind in the UK, and plants take 10yrs+ to build.

https://www.reuters.com/article/us-energy-nuclearpower/nucle... "Nuclear energy too slow, too expensive to save climate: report"

https://www.bbc.co.uk/news/business-41220948 "Two firms said they were willing to build offshore wind farms for a guaranteed price of £57.50 per megawatt hour for 2022-23. This compares with the new Hinkley Point C nuclear plant securing subsidies of £92.50 per megawatt hour."

Perhaps reply addressing my point rather than blindly downvoting :(

We can't possibly know the world that could have been if the subsidies payed out to wind power and solar were split 50%/50% along side nuclear. But I can't imagine we'd be in a worse place. There are so many ideas to explore, e.g. thorium or traveling wave reactors.

Unfortunately it's too late as we need to address carbon emissions now. If we want nuclear, we'll have to invest everything we should have invested over the last 30 years plus continue subsidizing renewables at the current rate.

Nuclear is expensive because of design costs and regulations. Mass production would greatly lower prices. The fact is when I was a nuclear power plant operator the same WOG value you could buy at Home Depot for 10 dollars costs 300 dollars with all the certifications and requirements for safety need in a nuclear plant.

don’t you welcome the spirit of all those pesky regulations?

Those regulations are buying down risk.

Sure, they could buy them from Home Depot without those regulations. But how do they know they were manufactured to spec? How do they know the manufacturer used the correct alloy?

You aren’t paying for “regulations” you’re paying for quality pedigree. This is also why aerospace work is so expensive. The industry has determined the supply risk is too great without a verifiable level of quality. Quality is expensive, but not as expensive as failure in these industries.

In Ontario, Canada we get a large portion of our energy from nuclear. We have a decent amount of wind, but if you click on the "Supply" tab you'll see it is very variable, and gas turbines kick in to pick up the slack:

* http://www.ieso.ca/power-data

Especially evident in the '5-11 Mar' data series.

Meanwhile nuclear chugs along at 10 GW day in and day out.

Eye-ballying it, if we added another 2500 MW of nuclear, then Hydro could probably pick up the slack with regards to the daily variable load in the province.

I'd be curious to know how portable this kind of set up would be: it's the variability of wind (and solar) that's of most concern to me. You have to build back-up capacity for both of them, and it's usually gas turbine.

To be fair, nuclear power plants are base load power generators.

So while the cost for wind power is just 57.5, I wonder how much will be the energy costs for, say a town powered with wind and with nuclear.

We're not going to resolve climate change with one or the other; we need a combination of every clean, non-fossil burning energy tech available.

That's one of these broad "sounds good, but isn't logical" statements.

We don't need "every clean" tech. If we have tech a and tech b and tech a is cheaper and can be scaled up faster, while tech b has a lot of challenges and is clearly more expensive in every situation then we don't need tech b. And I think there's a lot of evidence that in most situations nuclear (particularly new nuclear) is tech b.

If we have tech a and tech b and tech a is cheaper and can be scaled up faster, while tech b has a lot of challenges and is clearly more expensive in every situation then we don't need tech b.

The only problem with that is that theoretical "tech a" doesn't exist. Every energy production technology has some drawback or trade off. Nuclear is expensive, wind and solar don't work all the time, tidal is limited to coast lines, fossil fuel burning makes the climate worse, and so on. In the real world we can't limit ourselves to one single perfect solution.

Meanwhile, China has been investing steadily in nuclear power.

https://en.wikipedia.org/wiki/Nuclear_power_in_China

The UK has a problem with massive costs for infrastructure projects. Somehow projects that one would imagine would take a few guys with a bulldozer and a few loads of concrete end up costing millions.

Hinckley Point is just a larger example of that.

Portable nuclear bypasses that by being able to build in other countries without such extreme costs and import the result.

Large infrastructure projects with massive costs is hardly a UK-specific problem.

I guess instead of waiting a decade or more for a nuclear plant we'll wait a decade or two for these portable nuclear plants to be maybe (if ever) be commercialised.

In the meantime, we've already built the largest wind farms in the world which are proving valuable as the primary source of UK electricity https://electricityproduction.uk

Did we read the same article? To quote:

"Lyman believes that the department’s past efforts have “consistently underestimated”the “spectrum of mission risks posed by these microreactors," mostly around the technical challenges of keeping the radioactive fuel safe and operational in battlefield conditions.

“Fielding these reactors without commanders fully understanding the radiological consequences and developing robust response plans to cope with the aftermath could prove to be a disastrous miscalculation,” warned Lyman."

That might be different for civilian use though. I don't know exactly what "battlefield conditions" means (airdropping it in? bullets hitting it?), but that's likely different if you're just aiming for decentral power generation but have safe ways to deploy and maintain.

It is being funded by the pentagon. It isn't for civilian use.

When considering "battlefield conditions" think along the lines of people with heat seeking missiles and infrared goggles who can easily spot a hot nuclear reactor, and who really want to bring down a base.

Not to mention how complicated it is to operate and maintain a nuclear reactor even if conditions are ideal. The additional training and personnel required to support one of these things... would it really be worthwhile in the end?

"Battlefield conditions" means they need it to run the air conditioning in forward bases in occupied countries. At the moment, this is astonishingly expensive, because it has to be done with fuel trucked in across dangerous supply lines.

https://www.telegraph.co.uk/news/worldnews/northamerica/usa/... : every joule of energy spent on aircon in Afghansitan came from fuel trucked a thousand miles across the Khyber pass, getting shot at along the way. https://www.theguardian.com/world/2008/dec/08/afghanistan-ta...

If you're using enough power to warrant even a small nuclear reactor there's really no use trying to hide your thermals except maybe in a marine environment.

I'd assume it's not about hiding the base, but more about hiding this glowing hot obvious target.

Yes, this is about military use, I understood the comment from davidu to possibly not be focused on military use but about the idea in general, hence the difference between the positive lookout and yours (and the article's).

I'm not saying it isn't a bad idea for certain applications. I'm skeptical of the military application that is currently being pushed. It remains to be seen if one of these would even be plausible in the civilian arena, and the pentagon certainly isn't championing such (not that it should).

All of that just to power AC? Is the risk really worth the reward? Have the consequences of a failure in a military setting been fully considered?

battle conditions same spec for navy reactors on ships as ships generally face combat

Naval nuclear reactors are stored deep within the internal structure of the vessel (i.e. a negligible heat signature from the nuclear reactor is not visible from the outside). The proposed micro-reactor designs will vent the exhaust heat out into the open through an open Brayton cycle (i.e. it'll be really easy to spot).

Ships can be abandoned at sea with little risk because the nuclear material is likely to be unrecoverable. This is not true for reactors on land.

Surely nuclear submarines must dump their heat into the surrounding water - it has to go somewhere?

Sure. But the concern isn't about whether or not a nuclear-powered vessel can be identified as such; that information isn't really concealed, you'll have it as part of the same documentation that lets you ID a ship or submarine by class. The concern is about what happens when somebody drops a couple of mortar bombs on your land-based microreactor, or sets off a buried IED under it, or drives a VBIED into it.

Yes but water makes a very effective heat sink.

Can you explain how you came to the first conclusion wrt shipping container nuclear reactors?

Having studied light bulb nuclear reactors and a few legacy designs, I can't imagine a nuclear reactor cooling system pump fitting into a single 40ft container, let alone the "important" parts like the containment chamber.

Based on this article, they're talking about forward deployments to permanent military bases. That implies that they have a ton of infrastructure already in place to support a shipping container reactor.

Only each of th individual components (reactor vessel, turbine unit, pump unit) has to be container sized so they can be easily transportable and assembled on site. Small reactors fit in a SSBN so why not? Why fully rely on a pump if one can use natural circulation for emergency cooling? Hasn't Fukushima taught us anything?

https://www.world-nuclear.org/information-library/nuclear-fu...

You don't necessarily need a pump. If you sink your reactor into a body of water, it may use the water as both cooling and the mechanism that powers the turbine. Pumpless cycling of heated fluids is the basis for several non-nuclear thermal energy systems such as OTEC.

To quote MIT on the subject:

“It’s very close to the ocean, which is essentially an infinite heat sink, so it’s possible to do cooling passively, with no intervention. The reactor containment itself is essentially underwater.”

http://news.mit.edu/2014/floating-nuclear-plants-could-ride-...

Using the water as a limitless heatsink is also the cooling mechanism for the currently operational Akademik Lomonosov, which is the world's northernmost nuclear power plant. Russia is currently working on far more of them for its arctic drilling operations, and China is currently working on its first.

Stupid question: why do you want to cool a reactor anyway? Isn’t their raison d'être to be hot to generate steam and run a turbine?

Cool may be a bit of a misnomer. you want to transfer energy (as heat) from the reactor to the generator. To do this you pump a fluid in a cycle. It picks up heat at the reactor and drops it off at the turbine/generator. You want the reactor to get hot and stay hot but if you didn't move the heat it would just heat up until it melted and your turbine would sit there motionless and sad.

The moving fluid is called a coolant.

But doesn’t the normal cycle of water to the reactor and then to the turbine move heat? Why do you want to cool separately to taking useful heat energy away?

Nuclear reactors have a heat efficiency of ~33% so you need to dump the remaining somewhere. That is 66% of the heat energy remain after the turbine has removed the possible mechanical energy. Just an annoying factor of Carnot's Law.

If you can do district heating or similar it's all good, but you still need a permanent source of cooling capacity with enough redundancy to cool the reactor in case of an unplanned shutdown.

Increasing temperatures increase steam pressure until a rupture occurs, and the water boils away. The steel reactor vessel and structural elements will then inevitably melt, and the reaction will continue until the molten fuel can spread out enough to lose criticality. This is called a meltdown.

This is why many new reactor designs do not use water as coolant but instead molten salt[0] or inert gas[1], to avoid the risk of steam explosion. This alone does not make those reactors inherently safe but it can help keep radioactive material from being violently spread outside the reactor in the event of catastrophic failure.

[0] https://en.wikipedia.org/wiki/Molten_salt_reactor

[1] https://en.wikipedia.org/wiki/Gas-cooled_reactor

> Increasing temperatures increase steam pressure until a rupture occurs, and the water boils away.

Generally, no. Chernobyl is the biggest example of this happening, but it only happened because the reactor itself was basically exploding anyway.

Steam pressure doesn't build up gradually, generally. Relief valves -even just burst points- are just too simple and robust. The much more common issue is that hot reactor fuel causes water to break down and release hydrogen which accumulates at the top of the reactor and eventually explodes, and then the water boils off.

> Relief valves -even just burst points- are just too simple and robust

I'm not sure you've heard about this[0] accident:

"The accident began with failures in the non-nuclear secondary system, followed by a stuck-open pilot-operated relief valve in the primary system, which allowed large amounts of nuclear reactor coolant to escape."

[0] https://en.wikipedia.org/wiki/Three_Mile_Island_accident

The relief valve worked perfectly, as they said, there was no steam explosion.

Unfortunately too much of the steam was released and the reactor melted.

Uhhh, the valve worked perfectly but released too much steam resulting in a meltdown? Think about this for just a wee bit more.

okay not perfectly as it was stuck open, but it did release the pressure as was said.

But isn’t the water that is being cycled from the reactor to the turbine reducing the temperature? Isn’t cooling the reactor throwing energy away?

As one of the other sibling comments noted, a turbine can extract maybe 33% of the thermal energy if it’s operating at the theoretical maximum Carnot efficiency. The other 66% must be dumped somewhere to avoid accidents.

So what is being cooled is really the backend of the turbine, not the reactor.

Similarily to bikebreaks, it's often better to be safe than most efficient

Thermodynamics. You need a temperature gradient to extract useful work.

If you want a temperature gradient then you want the reactor as hot as you can and the condenser as cool as you can, so I still don’t understand why you want to cool the reactor?

The cooling system is also how you extract energy from the reactor. Anything you do to extract energy will have this effect; if it didn’t you’d have a perpetual motion machine.

The cooling sounds like a side-effect then. The goal isn't to cool for the sake of it. You want the energy out of it. If you just want a cooling system you could spray water onto it and let the steam escape. That'd be an effective cooling system. What people really mean is that they want to usefully extract the energy.

In an ideal reactor, yes. In a real-world reactor the cooling is also essential because you built your reactor out of things with a melting point.

Well, about 10% of the heat a reactor creates is from the radioactive decay of fission products, so even when a reactor is “scrammed” (shutdown, no fission occurring) you need to be able to extract megawatts of heat to keep it stable - hence you need powered pumps, access to water, condensation towers, etc.

Agreed. Actually it has always been a good idea but the costs associated with unlimited liability pushed the industry away from any commercial implementation. Some of the modern ideas, like the traveling wave reactor, have quite a bit going for them.

In a different political climate one could imagine a small reactor feeding a community rather than a substation.

I don't think it is politically possible for civilian use but military use of small reactors is well documented in the Navy.

It can and should be done by the military first because of less red tape involving civillian reactors. If it workd for the military it will also work for civillian operations. One just needs to modularise the reactors and their safety systems and be able to build a scalable solution with up to two dozen modules.

NuScale Power is on a similar path to deliver a working modular reactor by 2025. It uses 65x9 ft, 60 MWe modules. Not quite container sized but still transportable by bardge, train or truck.

3) The more of these I read the worse the vapourware to actual shipped devices gets, and the less likely I believe any of them are to ship.

Wind is our best bet against climate change in the medium term. Turbines built today will just be starting to be obsolete by the time these new nuclear ideas has scaled up.

Oh, and we need to take advantage of the spectacular fall in oil price to put in place a moratorium on new drilling, fracking and shale extraction.

maybe they could get the thorium cycle going for a small scale reactor; that would have the potential to make a big change if the cycle could be adopted to large power stations as well as small ones.

More complicated and still years away. It's the military we're talking about so little non-proliferation concerns there.

- i wonder if they will be evaluating this piece of information.

https://www.eurekalert.org/pub_releases/2020-02/tpu-trd02142...

https://news.tpu.ru/en/news/2020/02/13/35856/

https://www.sciencedirect.com/science/article/pii/S002954932...

Imagine a nuclear reactor for a car engine, always on energy that requires refueling only once about 2.5 years.

On the other hand, imagine a car crash.

30 J/kg absorbed radiation won’t just kill you in <48 hours, it’ll give you seizures and diarrhoea first.

That would make people drive more safely.

I met someone who tried to kill themselves by driving into a wall.

The only way I’d be comfortable living in the same city as a nuclear powered car is when it’s an electric car and the grid it charges from is nuclear powered.

There were designs for this but AFAIU the amount of mass needed for shielding the reactor would make it impractical. Not sure if technology has changed much but presumably the only way to get around this is to reduce radiation as the mass of shielding has more to do with fundamental physics I think.

My understanding (as a lay person) is that metal foams have revolutionized the area of shielding. I would imagine that many designs that were once impractical, may no longer be so given the new light-weight shielding technology.

Interesting, I was not aware of this - the problems I described were from designs in the 1960s

Of course it is. But it is for domain experts to decide what’s best and more promising, not you and me.

So beware of populist politicians banning this and that or trying to revive X. We need those who will set targets (CO2 emissions, costs, etc) and achieve them with the help of professionals.

I think one of the important things I've learned since leaving higher education is that over the past ~50yrs a deep culture of gatekeeping and credentialism has developed which does far more harm than good. People are capable of thinking through problems themselves and are often able to take in high level parameters about a concept and come to a conclusion without a degree or some other signal that they are an "expert".

This type of gatekeeping thinking essentially asserts the world as fixed. It asserts a world in which all possible domains of knowledge are known and only those with some set of credentials in that domain are allowed to speak to that domain. This both limits the possible benefits of multi-disciplinary pursuits but also asserts that there are no and can be no new domains of knowledge. It's very static thinking.

I do not deny the existence of harmful gatekeeping — one of my lecturers at university in 2005-06 insisted that “several megabytes” was too much data to record while I was recording the lecture as non-compressed 44k@16-bit.

That said, my experience is that most people don’t put in the effort required to understand problems like this. I include myself in this, despite being a poly-nerd with an interest in nuclear power.

This way of thinking is so idealist it comes back around on itself. Policymakers do not listen to professionals. Policy is based entirely around fashion. There’s no reason to push against good solutions becoming fashionable.

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