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naraburns  nihil supernum  2yr ago (text post)   3078 thread views

Friday Fun Thread for November 4, 2022

Be advised; this thread is not for serious in depth discussion of weighty topics (we have a link for that), this thread is not for anything Culture War related. This thread is for Fun. You got jokes? Share 'em. You got silly questions? Ask 'em.

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I’ve recently become quite enamoured with the idea of offshore nuclear power, as laid out in this presentation.

The benefits seem quite numerous:

  • the possibility of mass producing standardised power stations at significantly reduced cost

  • export business model

  • reducing the risks posed by tsunamis and earthquakes

  • sidestepping the NIMBY problems that normally emerge with these kind of projects

Anyone here able to point out why this is likely to be a terribly stupid idea in practice?

If you're interested in doing more research on this, there's a company called Karpowerships doing it with marine diesel barges (now with the option of running off delivered LNG).

One big difference is that they moor in port and don't have to pay crews to live on ships. Paying the oil rig wage premium to nuclear techs would be expensive, especially since the ones who enjoy living on boats probably stayed in the navy lol.

It's also much cheaper to build stuff that sits in a sheltered port: the substations on karpower's barges look like regular land ones with some anti-rust paint.

"Built in a shipyard and transported to the site: reduced construction cost and time"

"Quick and cost-effective decommissioning in a centralized shipyard"

That has to be someone who has never in their career dealt with a US shipyard. I mean, an argument could be made that the US would have to develop a better industrial base and new shipyards for this, as an added perk, which I am 100% on board with (I unironically stan NS Savannah), but as-is? Yeah, those two statements aren't happening.

They don't specifically say "US shipyard." In theory you could quite easily order Westinghouse ap1000s from China; they're already building half a dozen of them, so all the nuclear paperwork bullshit has been taken care of.

Makes you think: maybe the question isn't "is a floating power plant more cost-effective than a land-based one," it's actually "could a floating power plant from a place that can actually build things be more cost-effective than a land-based powerplant that can't be built at all"?

https://en.wikipedia.org/wiki/Akademik_Lomonosov exists, and it's a vanity project. 70 megawatts of electricity is a pittance. A fossil fuel power plant in Kostroma produces 3600 megawatts. And caviar.

What is we tried to scale it up? The main building of Smolensk NPP (3000 MW) is about 650 metres long and 150 metres wide. Prelude FLNG is 488 by 74, three times smaller. So a 1000 MW plant is probably the biggest floating NPP we can build right now, even if we somehow ignore the whole problem of squeezing in a substation, which needs a lot of open space and won't like ocean spray at all.

Smolensk NPP size is irrelevant, it's a RBMK-type reactor which is large compared to any other type of nuclear reactor. Water-water reactors are a lot smaller.

That's an important correction. I checked Rostov NPP instead (since it uses VVER), every one of its units is 205 by 136m for 1 megawatt of power. Again, one Prelude FLNG-sized barge.

I wouldn't necessarily say that it's a vanity project. The mobility is huge. Being able to float it to where it's needed and not have to ship in fossil fuels?

Shipping fossil fuels is a solved problem, especially if you need just 70MW. That's 90 thousand tonnes of coal, or 900 hoppers, or 18 smallish freight trains.

One advantage kinda minimizes the other, sadly; it's cheapest to ship fossil fuels to the same places a power barge can go. A combined cycle gas power barge that could refuel directly from an LNG carrier would have much higher power-to-displacement, be massively cheaper, and give more load-following capacity to 3rd world grids in brownout-prone places like South Africa and California. Nukes aren't great at that. (Edit: Karpowerships is doing exactly this in Dakar(?) now, but with natgas diesel conversions instead of turbines)

There's already some of those on the market by Siemens, iirc. Older power barges used big multi-fuel diesels.

On the other other hand, the low cost of gas turbines makes putting them ashore absolutely trivial. It takes a place as dysfunctional as Lebanon or Dominica to make a long term power barge lease a more viable alternative. And serving those places is risky, as Karpowership discovered with their Lebanon contract going unpaid.

Offshore geothermal ocean thermal power is interesting as well.

They're seriously glossing over the difficulty and expense of making compact steam turbines for use at sea. For one thing turbine halls are, what, twice the size of the reactor building itself? They've squeezed them into a much smaller space in the diagrams. I'll post it on Navalgazing to see what they think.

It's pretty common for nuclear concepts from the Good Idea Fairy to ignore the non-nuclear stuff.

Luckily there are still naval steam turbines made, but buying gear designed for the US navy isn't going to be easy or cheap (forget buying them on Alibaba lol), and I'm not sure what modifications would be needed for running them off commercial boilers using low-enrichment fuel rather than the 94% bomb-grade stuff military reactors use. The pressures are going to be different, I imagine.

And rather than transmission, I'd be worried about the costs of designing and maintaining very compact transformer equipment rated for use at sea. Nobody makes that afaik. (Edit: I was wrong about this, as there are power barges in use, but I don't know how wrong. Looking up what they cost would tell you a lot about how practical a nuclear one is.)

At least there's precedent: back in the 30s the US moored some of its turbo-electric carriers off California to provide power. This is literally just changing the heat source.

One thing I didn't see anything about in that presentation was transmission, i.e. how they plan on getting the power from the station to the onshore grid. While the station itself can float transmission towers would have to be fixed in place, and the cost of doing this for however many miles out these would be could possible undo any savings from the construction of the plant itself. Another concern is that using the ocean as a heatsink could cause heat pollution in the area around the plant. This wouldn't be so bad for one plant but several plants scattered at regular intervals could potentially cause problems. I'm generally pro-nuclear but I tend to be skeptical of too-good-to-be-true proposals.

Maybe don't move the power, move aluminium, ammonia , cryptocurrency, and other high energy manufactured products onshore.

I know very little about electrical transmission, but my understanding is that it isn’t likely to be a huge problem. There appears to be a number of existing subsea interconnectors that transmit large amounts of power over long distances.

Heating of the local area is a really interesting point that I’m not sure of the implications!

I'd love to see nuclear implemented at all, so if we have to put them out at sea then so be it. I'm a layman when it comes to this, but I guess there's the risk of contamination going directly into the sea if things go wrong. That said, we've detonated nuclear bombs over the oceans in testing before so it's probably not an existential problem, and we still run the risk of ocean contamination with traditional power sources via oil spills.

I don't think this will change the minds of many who aren't on board with nuclear already. Most of them oppose it on concerns of safety or the supposed permanence of the waste. I suspect there is a large group against nuclear because it can address power sustainability without fundamentally restructuring our economic and social system, but this is getting close to CW thread territory so I don't want to get into that.

That said, we've detonated nuclear bombs over the oceans in testing before so it's probably not an existential problem

There's also two US nuclear subs (Scorpion and Thresher) at the bottom of the sea, with no contamination.

We... dont talk about the Russian subs down there.

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