[cyberax]

Small modular reactors have almost nothing but disadvantages compared to the good old large-scale PWRs.

The ONLY advantage of SMRs is that they are easier to build because only a handful of companies in the _world_ possess technology to build reactor vessels for large-scale PWRs. And none of them are in the US.

[pstuart]

We have yet to see, as they've yet to truly enter the market.

So far, the record's not been good for large plants -- they tend to go way over budget and schedule. Case in point: Vogtle.

[Animats]

NuScale's price has already gone 60%-70% over budget, and they haven't even built anything yet.[1]

[1] https://oilprice.com/Alternative-Energy/Nuclear-Power/Are-Sm...

[pstuart]

The factors cited were inflation and higher interest rates, which are going to be universally applicable.

Cost overruns at Vogtle and others had inflation as a partial factor but the bigger issues, per the DOE:

"Work began with incomplete designs and managers repeatedly failed to realistically schedule tasks. Experienced workers were in short supply and defective work often had to be redone. Workers quit for other jobs and the COVID-19 pandemic led to high absenteeism."

So a pass on Covid impact but the rest is the result of building a huge bespoke power plant. SMRs change all of that to units of mass production.

I'm sure there's still issues to solve there but if nuclear has a future competing against low cost renewables then that SMRs seem to be the only way forward.

[cyberax]

Rosatom is exporting nuclear power plants within budget and (mostly) on time.

It's simply a question of expertise and experience. The US and Europe have ignored nuclear power for so long, that most expertise was lost long ago. And each new nuclear power plant becomes a unique snowflake.

[cinntaile]

Nobody in the western world is going to buy Russian power plants any time soon.

[cyberax]

Of course. Russia needs to be isolated.

I'm just saying that it's _possible_ to construct reactors within reasonable timeframes. Russia and China can do that, so can other countries.

[fodkodrasz]

That is mostly because there are no more large scale nuclear investments, lot of knowhow has been lost, everything is custom built now on every level of implementation (which SMRs promise to solve), and because people care about the initial investments, not for the TCO. Oh, and politically motivated NIH red-tape for getting some votes on the cost of whole society.

[cinntaile]

Nuclear benefits from stable output, but the world we're in doesn't require stable output so the economics become difficult.

[fodkodrasz]

This is not true.

[cinntaile]

You really refuted my argument there.

[kwhitefoot]

You didn't make an argument, you merely stated something that the respondent disputes. There is a very stable base load in most countries that can be well provided with nuclear. This is especially the case when there are good interconnections between neighbouring countries.

[fodkodrasz]

I'm simply tired of wasting time on renewable-energy-battery-storage fan service. We need stable power output.

[asynchronous]

Since they’re small they can be placed far closer to urban hubs and other places that suck electricity. The last design plans I saw one could fit within a single city block, buried under ground with only 1 story exposed.

[cyberax]

> The last design plans I saw one could fit within a single city block, buried under ground with only 1 story exposed.

This is a completely unrealistic plan, designed to lure investors.

An SMR meltdown will produce enough radioactive contamination to make a small city unlivable, at least for a while. So you'll need a full containment building. You'll need emergency generators, coolant pumps, etc.

Then you have a question of security, an easily accessible reactor will provide a great target for terrorism. So you'll need a perimeter around it with armed guards.

Then there's a question of control. A working reactor requires at least two trained nuclear engineers on duty at all times. So each reactor will likely need around 15 highly specialized engineers. That will have to live within a commuting distance.

Sounds bad already. But that's not all. There's also a question of inspections, something like the NRC can be reasonably expected to regulate several hundred reactors. They are not prepared to inspect many thousands of reactors. And the last thing I personally want is a "self-regulating" nuclear industry.

Any _realistic_ SMR power plant will look just like a regular large nuclear plant, except that it'll have multiple reactor units instead of just one large reactor.

[kwhitefoot]

There are designs for modular reactors that are inherently safe. Using subcritical reactors and a particle beam. See Aker Solutions: https://www.neimagazine.com/features/featureaker-s-ads-uses-...

Haven't seen any news from them recently though.

[cyberax]

They are not "inherently safe". Reactors that produce power (in large quantities) are dangerous because fission products are radioactive, and they produce energy even after the chain reaction stops. So once cooling is lost, these fission products can melt through the reactor vessel and escape the confinement.

Also, accelerator-driven reactors are just bonkers. They make no freaking sense for power generation. They are being investigated because they can produce very energetic neutrons, in quantities that are large enough to transmute some long-lived nuclear waste.

[kwhitefoot]

Are you implying that they do not produce more energy than they consume? Conventional commercial reactors release only a tiny fraction of the energy available in the fuel. Accelerator driven reactors make it possible to release more of it. They can also make effective use of thorium.

[cyberax]

No. I'm implying that they are completely impractical.

You need to have a system with cryogenic superconducting magnets and high vacuum within centimeters from a reactor producing at least hundreds of megawatts of power (if not gigawatts) within a volume of several cubic meters. You're basically constructing a fusion reactor at this point.

Oh, and parts of your accelerator close to the reactor will become activated, so you won't be able to do maintenance. ITER (the fusion reactor project) is planning to solve this problem using robots.

Fission reactors solve this by using VERY THICK pipes made of special steel, with careful inspection of every single weld. So once the vessel and its connections are placed, they stay inside the shielded area until it's time to decommission the reactor.