The role of nuclear power in a low carbon future

OVERKILL

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Well, underwater slumps can have many many times that much material and cause tsumani's as well.
It's good to know that the reactors can be passively cooled when all else fails...
Aye, that appears to be a quake-related situation as well though, with the underwater landslide as a result of the quake. Still fascinating! Thank you for sharing.
 
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This whole earthquake thing is fascinating unless you are in one of course. In 2013 the island I was on had a 7.2 quake. We were 20km from the epicenter. I will never forget it.

Later on they discovered that the entire island which is just over 1800 square miles in size tilted about one meter upwards to the north. A lot of small fishing ports were suddenly landlocked and they had to redo their pier locations.

We do not see most of what happens in these natural events.
 

OVERKILL

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Nuclear still adds heat to the environment. Still a cause of global warming.
By far the largest source of heat being added to the environment is solar radiation. What a nuke adds doesn't even show up in comparison. Thermal plant thermal emissions are not the cause of global warming/global cooling/climate change. The current theory is that CO2 levels in the environment, when increased, produce a greenhouse effect, which traps more heat (heat delivered by the sun), preventing it from being rejected and overall driving up the temperature of the earth. Of course methane is a far more effective greenhouse gas than CO2, so methane leakage is also a concern.
 
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Nuclear still adds heat to the environment. Still a cause of global warming.
It is interesting how some things humans do have near zero effects on the climate, compared to the sun, stuff like the actual heat produced by humans by burning fossil fuels, or nuclear power plant energy production, is a drop in a pool compared to what the sun does everyday. We have changed the ground surface reflectance and energy absorbance on a large scale with cities and especially tilled farm land in the spring before crops cover it, but that also seems not to be a significant factor in climate change theory.
But we are raising the level of atmospheric CO2 concentration quite rapidly compared to any recent natural sources, which is kind of worrying if you look at the historic CO2 levels compared to the estimated average global temperatures in the ice records... We are rapidly approaching CO2 levels beyond what we think the planet has seen naturally in the last few 100,000 years. Kind of a scary experiment to run, if you ask me!

I guess relatively, switching to all nuclear power and eliminating almost all fossil fuels is less of a risk to mankind overall, IMO...
 
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OVERKILL

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I'm assuming sarcasm here but just in case IIRC the heat released by nukes is in the form of water vapor from the cooling towers.
On plants so equipped. Some are once-through cooling (all of ours) so there's no vapour. The seasonal change in water temperature isn't impacted at all by this, as the great lakes are massive heatsinks.
 
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Going back to the scale of those plants: how well do they scale down? I'm guessing there are some lower limits where efficiency tapers off.

I'm guessing there is nothing to be gained but I'm wondering, given how one kvetches about the state of the grid, would more smaller nukes be better than large centralized ones? The grid wires have to all be connected and running everywhere, but I wonder if more smaller nukes might make the grid more robust.

I'm guessing the paperwork & red tape does not scale thus it's less work to make one big one as opposed to multiple smaller ones across the various NIMBY areas.
 
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The concept with small reactors is not so much to build smaller power plants, but have multiple small reactors at the same site instead of one large one. Small reactors can be constructed in a factory then moved to the site, which is much less expensive than on-site nuclear grade work. Also a small reactor is considered safer in an emergency shutdown. Snce it has a larger ratio of surface area to fuel capacity, "passive cooling" becomes at least theoretically possible.
 

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Ya. There's a reactor NW of Atlanta and boy does the reservoir get warm in the summer

Yeah, it's wild to see the impact the sun/summer and winter has on those water body temperatures. That lake goes from 4.7C to 27.7C seasonally, that's a huge swing!

Thermal differential limit on our nukes (no idea what it is for US OTC plants) is 10C, that is, outlet temp can't exceed inlet temp by any more than 10C. Typical value is 3C at Bruce, which is our largest plant. So, if it's pulling in 4C water from the bottom of Huron, it is discharging at shore at 7C, which is, during the summer, likely colder than the surrounding water, that has been heated by the sun.
 

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Going back to the scale of those plants: how well do they scale down? I'm guessing there are some lower limits where efficiency tapers off.

I'm guessing there is nothing to be gained but I'm wondering, given how one kvetches about the state of the grid, would more smaller nukes be better than large centralized ones? The grid wires have to all be connected and running everywhere, but I wonder if more smaller nukes might make the grid more robust.

I'm guessing the paperwork & red tape does not scale thus it's less work to make one big one as opposed to multiple smaller ones across the various NIMBY areas.
It's a complex topic, so I'll try and simplify it somewhat:

Large units have the following advantages:
- Higher nameplate capacity for a given staff load
- Lower cost output (tied to the above point, lower OPEX)
- Many mature existing designs in a variety of sizes (C6 is around 675MWe for example, EPR is 1,600MWe)

Large units have the following disadvantages:
- Higher CAPEX for construction
- A trip drops a tremendous amount of capacity off the grid, so your grid needs to be setup to deal with that

Small units have the following advantages:
- Faster construction
- Lower CAPEX
- Fewer staff
- A trip drops a much smaller amount of capacity off the grid, making contingency requirements less

Small units have the following disadvantages:
- Incremental capacity additions are small
- More expensive per MW for a given staff load

What Ontario Hydro did here in Ontario was build 4-packs. Multi-unit plants with common turbine halls increased the economy of scale factor and that's how we had previously built coal plants. While our first commercial nuke was a single unit (Douglas Point, 220MWe), the first large-scale setup at Pickering was 4x515MWe units, followed by Bruce A at 4x750MWe units, followed by Pickering B at 4x516MWe units, followed by Bruce B at 4x860MWe, followed by Darlington A at 4x880MWe.

One of the advantages of the above approach is that it minimized the effects of a large single unit loss, because we had a LOT of units. The maximum single unit trip is 880MWe out of a nuclear capacity that was, at the time, about 14,000MWe.

The grid is designed to connect large generators to centres; it uses large transmission corridors to move massive amounts of power from these sites to local distribution. Local distribution itself is not normally setup to have large quantities of embedded generation (this is the issue large quantities of residential solar creates, the grid isn't setup for it). Think of these transmission corridors as backbones. These are much larger and much more robust than local distribution infrastructure and therefore much more resilient.

Transitioning the traditional infrastructure, with limited large backbones, to a more dense spiderweb of "microgrids" with embedded generation will add considerable cost, both in terms of CAPEX, as well as OPEX. Maintaining even larger amounts of transmission is going to make things significantly more expensive.

I expect how we'll see SMR's deployed are in sites similar to how Ontario Hydro built our plants. You'll have a lot of units at a single site, which simplifies management and security and minimizes transmission infrastructure. That's just my take on it however, how it actually bears-out may be quite different.

The first commercial SMR to come online in North America will likely be the MMR at Chalk River, unless the BXWR 300 at Darlington beats it. OPG was well ahead of the game with an active EA and valid site license already, and they are using a cookie-cutter design based on a scaled-down traditional BWR design by GE, so it has the least risk of complication.
 
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