[kragen]

Hey, aren't you the guy who was saying that solar-powered electric freight trains would only be able to run at night? https://news.ycombinator.com/item?id=26240032

I agree that nuclear waste is probably a manageable problem, but not for the reasons you say. "Zero risk" is not a thing that actually exists anywhere ever. "Bedrock with no aquifer" is a thing that exists, but it's not what you're looking for: the rockhead under a desert, for example, is bedrock with no aquifer, and it's commonly very porous and water-permeable. What you want is impermeable rock that will stay that way, like a salt deposit, which is indeed pretty safe—many salt domes have successfully kept petroleum or natural gas from leaking to the surface for 300 million years or more.

The special difficulty of nuclear waste is not that it's especially toxic—far more toxic materials certainly exist, even commonplace materials like hydrofluoric acid, hydrazine, and tetraethyllead. But if you pour hydrofluoric acid on the ground in most places, it becomes completely nontoxic within a few minutes. Hydrazine loses most of its toxicity if you just set it on fire, although burning it to totally nontoxic materials requires a little more care. Tetraethyllead also loses most of its toxicity when you burn it, though the resulting lead compounds were still toxic enough to cause a worldwide crime wave lasting decades.

What's special about nuclear waste is that no such simple means of detoxification exists. The only way to detoxify nuclear waste is with another nuclear reactor—and that's not only in need of additional development to bring it from the laboratory to production, it's also commonly prohibited because of proliferation concerns.

The real risk with nuclear waste, though, is not that disposing of it safely is rocket science; it's that the people who are in charge of it in countries like the US are the same ridiculous bumbling assclowns who've bungled the covid pandemic so badly. (Did you know that, though China was vaccinating college students last July, 1000 people a day are dying from covid in the US?) Have you read about the cat-litter explosion at WIPP? https://en.wikipedia.org/wiki/Waste_Isolation_Pilot_Plant#20... Someone used "an organic cat litter" in place of "inorganic cat litter" to immobilize the nuclear waste, so it caught on fire.

Fortunately, all of this is moot; as I said, nuclear energy is now so much more expensive than solar energy that there's no longer any reason to use it except in a few special niches, and that's unlikely to change for decades. Enjoy your Video Toaster.

[sir_bearington]

The comment said that solar powered trains would only be able to run at night if wind generation is sufficient to power them in the absence of solar power - at least not without massive amounts of storage to account for this intermittency.

Regardless, I'm not sure why the inability to detoxify waste is such a concern. First of all, we do have the ability to reclaim >95% of it through reprocessing. This isn't detoxification per-se, but does represent a sizeable reduction in the amount of waste. And the remaining waste is stored underground. The danger of uranium entering the water supply already exists from naturally occurring uranium. The additional risk presented by waste buried in a known location, with no groundwater contamination risk is zero. Sure, if you want to be pedantic, it's not exactly zero: some nefarious group could dig it up and use it as a weapon. But any group with that level of capability could easily deal more damage through conventional means - so for all intents and purposes the risk is zero.

[kragen]

Aha, thanks for clearing that up.

I think probably trains will have an easier time carrying batteries than electric cars do: a one-tonne diesel internal-combustion-engine car might get (in medieval units) 40 miles per gallon of fuel, while diesel freight trains routinely get 480 miles per tonne-gallon. Teslas need to recharge about every 500 miles, so we should expect battery-powered electric freight trains with the same battery mass fraction as a Tesla to need to swap batteries roughly every 6000 miles or 10000 km. A night train making it through the night isn't going to be a problem.

If that's true, then why haven't batteries already replaced diesel engines in diesel-electric locomotives? I suspect it's a matter of battery costs and network effects. A gallon of diesel is 146 MJ, so a tonne-mile on a freight train costs 300 kJ, or 189 kJ/tonne/km in non-medieval units. Lead-acid batteries only give you roughly 20 kJ/US$, and low-power lithium-ion batteries are usually more like 10 kJ/US$. You get a multiplier of about 3 because diesel engines are typically about 35% efficient and electric motors are about 95% efficient, so you only need 70 kJ/tonne/km. But 500 km of range would still cost you 175 grand of lead-acid batteries for every 100-tonne railroad car in the train, which more than doubles the cost of the train. If you use lithium-ion instead, it's twice that: US$350k a car. So, expect this to take a significant amount of investment, and therefore take a couple of decades—if it happens at all, because quite possibly it's all-around cheaper to use cheap solar energy to produce ammonia or hydrocarbons and burn those on the train.

The inability to detoxify waste is a concern because detoxifying is what we normally do with hazardous waste. Learning to handle hazardous waste in a different way is risky and will involve some accidents. I mean, it already has.

[kragen]

> The comment said that solar powered trains would only be able to run at night if wind generation is sufficient to power them in the absence of solar power

To be perfectly fair, while that's presumably what you meant—and it's a sensible point—what you said was, "making it so that trains only run at night and on windy days".

[sir_bearington]

Yes, trains can only run at night when it's also windy. I'm not sure how you arrive at the conclusion that solar powered trains can only run at night, short of willful misinterpretation.

[kragen]

Well, if something runs only at night and on windy days, that means it runs at night, regardless of whether there is wind, and that it runs on windy days—which might mean "24-hour periods that have a lot of wind", thus also including the night, or "non-night periods that have a lot of wind", due to the semantic ambiguity of the English word "day". In this case, though, the ambiguity doesn't matter; it comes to the same thing. But the meaning is different from your intended meaning.

A different way of stating the meaning of "only at night and on windy days" is "always, except in the daytime when it isn't windy". But of course the daytime when it isn't windy is precisely when it's actually possible to run solar-powered trains without batteries, at least if you run overhead powerlines or a third rail down the whole train track.

What you meant was "trains run at night only on windy days", which could also be validly phrased (at the cost of some ambiguity) as "trains only run at night on windy days". But the extra "and" that you inserted in the middle of the phrase made it impossible to read the phrase as having your intended meaning. Perhaps you hadn't noticed the extra "and" when I quoted it in my earlier comment above, accounting for your confusion. Or perhaps you just don't speak English very well. Which is okay! I'm a second-language speaker too, and it's hard at times! But it's not a valid reason to accuse people of willfully misinterpreting you.

[sir_bearington]

Why on earth would it make sense to think that someone is saying solar powered trains only run at night? I'm a native English speaker so I don't think you're in any position to try and lecture me.

It's absolutely a valid reason to accuse you of willful misinterpretation, especially when you bring this up more than a month later in an unrelated topic. Your reply was downvoted with good reason.

[kragen]

I brought it up precisely because what you were saying didn't make sense, because what you were saying in this thread didn't make sense either. The reason I thought you were saying what you, in fact, said, even though it wasn't what you meant, was that it appeared on this website under your name.

It seems like you have a long history of not worrying about whether the things you're saying don't make sense, and you're continuing it. Instead of responding, "Oh, I see what you mean, you're right, I actually did say the opposite of what I meant—thank you for giving me the opportunity to clarify and taking so much time to explain at such great length what was in the end very simple and obvious," you're responding with some kind of chimpanzee status hierarchy nonsense about being "lectured" and what "position" I'm in. Instead of responding, "Oh, you're right about the 'bedrock with no aquifer' thing, that was totally wrong and didn't actually make sense," you just ignored it.

I guess you're just trying to score some kind of points rather than learn what is true and help others do the same?