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Comment by StillBored | Hacker News Reader

You have to question the assumptions if the basic math at the beginning doesn't even seem right. They claim 440 reactors today need to scale to 15,000. That is a 34x increase.

Yet, https://www.ieer.org/ensec/no-1/glbnrg.html says that 18% of worldwide generation is already nuclear. So, to get to 100% that would be ~5x, not 34x.

So, just that one change pretty much blows most of their argument away, particularly if you assume that simply replacing many of the existing reactors would give a capacity increase due to turbine/heat efficiency improvements now done at modern plants.

So the scare mongering about having to build/replacing a reactor each day sounds like utter bollocks.

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This is probably a confusing on your part between energy consumption and electricity consumption. For a fossil free future we also have to replace fossil fuels used for heating and transportation. It's likely that we won't need a 1:1 replacement (by far) because heating and transportation can be done much more efficiently with electricity (thanks to heat pumps and the efficiency of electric motors).

1. We don't need to replace all fossil fuels to just do better than we're doing now. It'd be a big help to just replace all fossil-fuel power plants, which is what the OP was talking about.

2. Cars and trucks can be powered by electricity in the near-term. Airplanes cannot; we'd need much better battery tech for that to happen. Heating can't be replaced by heat pumps entirely; heat pumps don't work in subfreezing conditions. They have to resort to "auxiliary heat" (electric resistance heating) when it gets too cold. Of course, doing that and just having more nuclear plants is still better than burning hydrocarbons, but it does mean we need more electricity generation.

   heat pumps don't work in subfreezing conditions.

Not with the refrigerants used in retail AC units, which are sub-optimal even for that use when compared with some of the older HCFC's and CFC's. A lot of the current designs also likely ice up, so you need much larger evaporator coils/fields. Then there ends up being the question of what the efficiency looks like.

Anyway, I'm just trying to say, that there is still heat in the air/etc below the freezing point of water, the science says it can work, and if you do a bit of googling you can even find vendors advertising fairly cold weather devices (-27C).

https://daikinatlantic.ca/2019/11/03/what-are-the-best-heat-...

So, making better ones is an engineering problem.

Funny thing about heat pumps.

Right now they primarily use refrigerants that have ~2000 times more GWP than CO2. They need to be refilled every 5-10 years.

My brother had one installed recently. They leaked the entire contents twice due to over tightened connectors. A back of the envelope calculation indicates that his heat pump will emit more GWP gas than if he has just burned natural gas by a wide margin.

Recently I recall reading an analysis that half of the heating since the 70s is attributable from refrigerants.

So while heat pumps are more efficient from am energy standpoint, with current refrigerants they are not helpful for climate change.

I think it may have to do with where you live.

I've been in the same house in south-central USA for 15 years now. It has a heat pump, first I've owned. It provides reliable, inexpensive service. I have only good things to say about the heat pump.

I hope the additional emissions (if that's factual) are offset by the many years of reduced electricity usage (which I am certain is factual.)

Worth noting that your reference is from 1993, and although your argument still stands for a modern reference:

"Around 10% of the world's electricity is generated by about 440 nuclear power reactors" [0]

[0] https://www.world-nuclear.org/information-library/current-an...

Electricity is not everything. Heating and transport eat up much more fossil fuel. That can be replaced by, uh… nuclear-powered electricity and synthetic fuels, I guess? However you do it, it adds a lot to the necessary power budget.

If you use nuclear waste heat for district heating and load follow with steam bypass to make hydrogen or just charge batteries you can cover transportation and heat.

You can't use nuclear waste heat for heating. No one wants to live next door to a nuclear power plant, so you can't feasibly transport the heat to someplace where it can be used. Nuclear plants are always located remotely for a reason.

Bad phrasing. I meant nuclear heat that is usually wasted as thermal discharge. Not from high level nuclear waste.

We do have a few communities heated by nuclear district heat. It can ship about 50km ok

No, I get it. I know you didn't mean using heat from nuclear waste, but from the reactor itself: nuclear reactors do produce an enormous amount of heat. But the same is true of fossil-fuel plants; nuclear plants simply substitute burning fuel with a controlled nuclear reaction to produce heat, which then creates steam, which drives steam turbines. It's a heat engine. The problem I see is that it's hard to transport heat. Putting steam in pipes only works so far; you lose too much heat to the environment because the pipe's insulation isn't perfect. There are places (like university campuses) which heat buildings this way, but they're not transporting that steam hundreds of miles.

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