What Is the Most Efficient and Safest Method to Generate Electricity?

[russ_watters]

This has some damning figures:

and:

That first bit is kind of misleading because that's the total energy use from all sources, not just electricity. It includes heating and cars, for example. Now, maybe he's talking about replacing everything with electricity, but note that heating is not replaced at a 1:1 ratio. A heat pump allows you to get the same amount of heat for perhaps 1/3 as much energy input. Similarly, an electric car is much more efficient than a gas powered car. So an all electric world would use substantially less power than that estimate.

Second, 1 nuclear plant a day may sound like a big number, but we live in a big world. Though it has slowed a bit from its peak, China alone was turning-on a new coal plant better than once every 4 days until a few years ago. That's just one country and one source of energy! The world most certainly has built large power plants at a rate of one a day before and though nuclear is harder than other sources, it is something that can be done. France as a country went all nuclear for electricity over a period of 20 years -- there is no reason other countries can't do it too.

 

[Ryan_m_b]

Second, 1 nuclear plant a day may sound like a big number, but we live in a big world. Though it has slowed a bit from its peak, China alone was turning-on a new coal plant better than once every 4 days until a few years ago. That's just one country and one source of energy! The world most certainly has built large power plants at a rate of one a day before and though nuclear is harder than other sources, it is something that can be done. France as a country went all nuclear for electricity over a period of 20 years -- there is no reason other countries can't do it too.

I've looked this up before and don't remember finding much informative but I wonder how mass production would affect the economics of nuclear power. AFAIK nuclear power stations are built to order and in countries like the UK we've only built them once in a long while (though I think we build some magnox reactors in ~5 years once). If you wanted to build a whole load of reactors at once, or at least over a small time scale, then presumably mass production would bring the unit cost down somewhat.

 

[russ_watters]

I think the news reports I read look like a snapshot, and it was misleading. They met half of demand with solar, but it was a low demand time. It is a bit difficult (apples to oranges) to compare power plant maximum capacities and what is being run.

Well, sorry, but that would be a pretty useless stat.

The yellow line for solar does show the story of increased installation. And you absolutely have to build capacity for peak demand, and the coal/nuclear plants will remain the main backstop for that peak. It looks like for the last decade, the only significant capacity they are adding is in Wind, Solar, and Other (hydroelectric?). The German goal is 80% of electricity from renewable sources. It may be that they will have a surplus coal plant capacity remaining idle.

IMO, Germany's goal is unrealistic. Currently they are not replacing all of the power they are shutting down, they are buying it from adjacent countries.

I would say the electricity from solar in Germany is NOT insignificant. If you look at power capacity, it is still a very small fraction of the installed power production infrastructure. But it is used at 100% capacity available, which actually makes it more significant than you might otherwise expect.

I'm sorry, but you have that exactly backwards. Because solar only runs during sunny days and at peak when the sun is overhead, it runs at perhaps a 15% capacity factor, which is much lower than most other sources. Nuclear tends to run above 90%. That said, the graph I provided was in energy, not power (but be wary of news articles reporting/comparing solar by capacity: they are misleading). Still, I challenge you to try to calculate the fraction of the energy generated by solar: the number is so small, it is tough to read off the graph accurately!

The US, this summer, is likely to reach the milestone of solar energy providing 1% of our energy over the course of a month (probably this month), after which it will go back down again until next year. When I say "insignificant", 1% is about enough to start paying attention even if it doesn't make much of a real difference. The Department of Energy still has to report "other renewable" energy sources on a separate graph/table from the primary sources because they are too small to read on the same graph. That's a sign of irrelevance, to me.

 

[russ_watters]

I've looked this up before and don't remember finding much informative but I wonder how mass production would affect the economics of nuclear power. AFAIK nuclear power stations are built to order and in countries like the UK we've only built them once in a long while (though I think we build some magnox reactors in ~5 years once). If you wanted to build a whole load of reactors at once, or at least over a small time scale, then presumably mass production would bring the unit cost down somewhat.

Agreed. And if we're going to talk about all of the world's energy, we need to consider all of the worlds energy in the comparison: [google] If a random car manufacturing plant can output 1,000 cars a day at 100 kW each, that's the equivalent of one nuclear plant every 10 days(at a cost of $200 million). So the goal of one nuclear plant a day could be served by just 10 auto manufacturing plant scale facilities (rough order of magnitude estimate).

[edit: also, while the guy said "plant" and I've continued using the word, I think he means "reactor". In the US, the average nuclear plant has about 3 reactors.

 

[zoobyshoe]

That first bit is kind of misleading because that's the total energy use from all sources, not just electricity. It includes heating and cars, for example.

It says current global power consumption is 15 terawatts, so I think he's only referring to electricity, not gasoline or heat.

Second, 1 nuclear plant a day may sound like a big number, but we live in a big world. Though it has slowed a bit from its peak, China alone was turning-on a new coal plant better than once every 4 days until a few years ago. That's just one country and one source of energy! The world most certainly has built large power plants at a rate of one a day before and though nuclear is harder than other sources, it is something that can be done. France as a country went all nuclear for electricity over a period of 20 years -- there is no reason other countries can't do it too.

The thing is, though, this would be ongoing: non-stop. A new nuclear power plant would have to come online somewhere every day, and there would eventually be a huge backlog of them undergoing the 20 year decommissioning with a new one added to that every day for as long as we used nuclear. It wouldn't just be a temporary bug push. And, as it said earlier in the article, there are only so many sites in the world suitable for a nuclear power plant:

Land and location:Onenuclear reactorplant requires about 20.5 km2(7.9 mi2) of land to accommodate the nuclear power station itself, its exclusion zone, its enrichment plant, ore processing, and supporting infrastructure. Secondly, nuclear reactors need to be located near a massive body of coolant water, but away from dense population zones and natural disaster zones. Simply finding 15,000 locations on Earth that fulfill these requirements is extremely challenging.

Once you get 15,000 nuclear power plants built, you only have enough viable uranium to operate them for 5 years:

Uranium abundance:At the current rate of uranium consumption with conventional reactors, the world supply of viable uranium, which is the most common nuclear fuel, will last for 80 years. Scaling consumption up to 15 TW, the viable uranium supply will last for less than 5 years. (Viable uranium is the uranium that exists in a high enough ore concentration so that extracting the ore is economically justified.)

So, you'd have to extract it from seawater, and we don't currently have a good way to do that. If we did, we would render the concentration unusable in 30 years. There's thorium, and breeder reactors, but any kind of reactor requires things besides the nuclear fuel, things that are not limitless:

Exotic metals:The nuclear containment vessel is made of a variety of exotic rare metals that control and contain the nuclear reaction: hafnium as a neutron absorber, beryllium as a neutron reflector, zirconium for cladding, and niobium to alloy steel and make it last 40-60 years against neutron embrittlement. Extracting these metals raises issues involving cost, sustainability, and environmental impact. In addition, these metals have many competing industrial uses; for example, hafnium is used in microchips and beryllium by the semiconductor industry. If a nuclear reactor is built every day, the global supply of these exotic metals needed to build nuclear containment vessels would quickly run down and create a mineral resource crisis. This is a new argument that Abbott puts on the table, which places resource limits on all future-generation nuclear reactors, whether they are fueled by thorium or uranium.

So, this Abbot fellow paints a pretty damning picture for those who think we can just convert everything to nuclear when the fossil runs out.

 

[Ryan_m_b]

AIUI we could also reprocess the nuclear waste we currently have to produce more fuel as we're rather inefficient at using it these days. Uranium levels aside I don't think we'll ever need to have an all nuclear world given how renewable energy is a very good option for large regions (solar in equatorial countries, places like Brazil have loads of hydro, Iceland loads of geo etc).

 

[zoobyshoe]

AIUI we could also reprocess the nuclear waste we currently have to produce more fuel as we're rather inefficient at using it these days. Uranium levels aside I don't think we'll ever need to have an all nuclear world given how renewable energy is a very good option for large regions (solar in equatorial countries, places like Brazil have loads of hydro, Iceland loads of geo etc).

Right. That particular author is addressing people who are unconcerned about using up fossil fuels because they believe we can just switch everything to nuclear, and it will last forever.

 

[russ_watters]

Here's the original article:
http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=6021978

It is really bad and really disappointing for IEEE.

First:

It says current global power consumption is 15 terawatts, so I think he's only referring to electricity, not gasoline or heat.

That's an American-layman-centric view due to our use of the English system for everything except electricity: kW and kWh are power and energy, period, and do not imply electricity.

2012 global primary (see what "primary" means below) energy consumption from all sources was 155,505 TWh, which works out to 17.8 TW:
https://en.wikipedia.org/wiki/World_energy_consumption

Original source is here, but it is a dense read:
http://www.iea.org/publications/freepublications/publication/WEO2012_free.pdf (page 69 is a good start)

Second, that is primary energy, not the electrical energy itself:

In 2008, the world total of electricity production and consumption was 20,279 terawatt-hours (TWh). This number corresponds to an average consumption rate of around 2.3 terawatts continuously during the year. The total energy needed to produce this power is roughly a factor 2 to 3 higher because a power plants' efficiency of generating electricity is roughly 30–50%. The generated power is thus in the order of 5 TW. This is approximately a third of the total energy consumption of 15 TW.

https://en.wikipedia.org/wiki/Electric_energy_consumption

Why does that matter? Because if you use natural gas for heat, you might get 95% efficiency, but if you use natural gas to make electricity, to make heat with electrical resistance, you might only get 35% efficiency. That's the issue I was highlighting previously. So:

The article erroneously compares primary energy to secondary energy, so they are high by a factor of three. Specifically, if a nuclear plant is about 33% efficient, that means a 1 GWh electrical output is provided by a 3 GWh nuclear heat input. Worse, due to the improved efficiency of heat pumps and electric cars, a pretty significant fraction of the energy will be saved in the switch - as much as 2/3 for those uses.

Third, why set a goal so high to begin with? Fossil fuels are depletable, but wind, solar and hydro aren't. Even the most ardent proponent of nuclear power (me?) wouldn't suggest we tear down the Hoover Dam. In the US, my starting goal for nuclear would merely be to triple it, to eliminate fossil fuel electricity and start to dig into what would be needed for all-electric heat and cars. That's an eminently feasible goal (See: France).

For the other issues:
His accident rate is a combination of bad math and bad analysis. To get a number like 11 "full or partial core-melt" requires treating all of the 2012 Japanese reactor failures as separate accidents, counting early research reactors (not commercial reactors) and counting accidents that caused only minor damage. A more reasonable count would be 3 major accidents, destroying 5 reactors (Fukushima alone lost 3 reactors). Obviously, since the Fukushima reactor failures were all triggered by the same event, you cannot extrapolate that to a rate for separate events.

Even worse, he assumes that that rate is going to be the same, forever. That is widly unrealistic, probably by somewhere between a factor of 10 or 100. The obvious comparison is with plane crashes. The worst year (globally) for commercial plane crashes was 1972, when 55 planes crashed. In 2014, 12 crashed. But people fly about 7x more today than they did in 1972, so the accident rate is actually 1/32nd what it was in 1972. That is an entirely engineering-dirven improvement.
http://www.cnn.com/interactive/2014/07/travel/aviation-data/

We already know nuclear power has gotten safer: the worst accident, Chernobyl, is not possible today and shouldn't have been possible even then, but the USSR ran a known flawed design. Such an accident was not possible in countries with more mature industries like France or the US (or even Japanese) and I don't think there are any reactors left with similar designs.

Frankly, the article reeks of bad anti-nuclear activism. Whether it is dishonest or just misinformed I don't know, but I don't have much sympathy for errors that always lean in the same direction. Much of the rest is the same wrong, recycled anti-nuclear rhetoric we've seen for decades (such as the storage and proliferation red-herrings, plus he threw in some peak oilism for good measure). It's so bad I'm loath to keep going, but a couple more that you asked about specifically:

1. Fuel: we have a once-through fuel cycle because it is cheap and the fuel is plentiful. Bad math on how many plants we need aside, if it starts getting scarce, we can just start recycling it: we are a long, long way from needing to get it from water, even if we build plants by the thousands.

2. Waste: Waste is a non-existent issue, or, rather, is a fully political issue. Most nuclear waste isn't even really waste (see #1) and the waste that is can be stored basically anywhere. The idea of needing 100,000 years of stable geological storage is a fools-errand set up for political reasons to keep nuclear power down. We've been storing the waste locally for 50 years and all that is really needed is more storage for those places that are filling-up. Perhaps a central facility, located, literally, anywhere would be nice, but it isn't a limiting factor.

3. Land use: What? See solar, wind and hydro. This is a non-issue for nuclear. And the number itself is at least intentionally misleading for that too, by a factor of 10, since it includes not just the plant, but off-site support facilities like the processing plant that have different constraints and are probably not additive. The plant near me (2 reactors) is 30 miles from the center of Philadelphia and covers about half a square mile of ground. 15,000 reactors totals 3,700 sq mi at that rate. That's 100-1000 times less than what would be required of solar.

4. Rare metals and environmental impact of mining them: What? That's troglodyte talk (literally). Every industry depletes resources and damages the environment. The whole point of nuclear is that it does less of that than, say, coal. That argument is nothing short of lets-go-back-to-living-in-caves "environmentalism".

 

[russ_watters]

Right. That particular author is addressing people who are unconcerned about using up fossil fuels because they believe we can just switch everything to nuclear, and it will last forever.

Do any such people exist? That on it's own is a really bad strawman - a star-trek style limitless energy utopia (he actually says "nuclear utopia" ). Let's start smaller, with replacing our coal power with nuclear and then see where we are in 30 years or so.

 

[tom aaron]

Do any such people exist? That on it's own is a really bad strawman - a star-trek style limitless energy utopia (he actually says "nuclear utopia" ). Let's start smaller, with replacing our coal power with nuclear and then see where we are in 30 years or so.

Re uranium supplies. It's a grey area. I first came to Canada in the 1970's because of a job involved in field exploration for Uranium and other resources in the High Arctic and then in Nova Scotia. We did seminal mapping and there was a general high concentration of uranium ore. However, none of his was developed due to an eventual decrease in demand ( thus the closing of Uranium City).

That was my last experience with hard rock geology before moving into paleontology. So, I know very little about uranium deposits. However, I'd 'guess' that with demand, exploration would pick up and potential large deposits developed.

Back to the real world. Nuclear energy is on wobbly legs. A big issue is not only acceptability but viable nuclear technology infrastructure. A lot of it is gone...non existent. Along with nuclear plants, China is also developing incredible infrastructure...this is also France's forte. If the USA was to 'declare' the building of a hundred plants tomorrow it would largely be a paper declaration...much (not all)of the nuclear infrastructure is gone. That generation has retired and the new generation is working for apple perfecting Itune downloading.

 

[jim hardy]

Along with nuclear plants, China is also developing incredible infrastructure.

Can this be so, they're making half the world's steel now?

I think we've awakened a sleeping giant.

 

[russ_watters]

Nuclear energy is on wobbly legs. A big issue is not only acceptability but viable nuclear technology infrastructure. A lot of it is gone...non existent. Along with nuclear plants, China is also developing incredible infrastructure...this is also France's forte. If the USA was to 'declare' the building of a hundred plants tomorrow it would largely be a paper declaration...much (not all)of the nuclear infrastructure is gone. That generation has retired and the new generation is working for apple perfecting Itune downloading.

You say "infrastructure" but it sounds like you are describing "expertise". Assuming I'm reading you correctly, I agree: it will take decades just to build-up the expertise to ramp-up production to be able to build (for example) a hundred plants at a time (10 being completed a year for 10 years of construction). It's a huge problem.

Fortunately(?), we'd need at least a decade after making the decision before anything can happen anyway. "Somebody" would need to develop a/the new, standard, reactor for mass production and production facilities would need to be designed and built. This would also slowly build back up the expertise base as people are brought-in to work on the systems.

Fortunately, my understanding is that the nuclear portion of a power plant is not a huge fraction of the plant: much of construction of a plant is just regular steam/water piping, steel framing and concrete. So while building that many new plants at once may take a million people, the vast majority need not have nuclear power expertise.

Note, in my now 10 year old "Fix the US Energy Crises" thread, I said 5 years of design and 5 years per plant to build, though still a total of 10 per year. That's probably overly ambitious timewise, but the output ends up roughtly the same. Though it is all moot until someone decides to pull that trigger. Still, it is tough to accept for someone who was born after Apollo, that we could get to the moon in 10 years, at a time before computer aided design, but can't design/build a nuclear plant in 10 years (much less design and produce a new fighter jet in 20 years!).

 

[mheslep]

t says current global power consumption is 15 terawatts,...

That's the commonly used figure for the all-in, global primary rate: electricity, heat, transportation, everything. The total energy figure drops significantly if everything, especially transportation, is theoretically converted to electric power because of the efficiency improvement.

 

[mheslep]

Can this be so, they're making half the world's steel now?

China also now burns more than half the world's coal.

 

[mheslep]

This has some damning figures:

The author lacks a sense of scale. Currently, a new coal, gas, or oil electric plant (500 MW equivalent) is built globally every 1.3 days (i.e. 131 GW new fossil fuel capacity in 2013), which doesn't include all the biomass, hydro, or nuclear plants coming online every day.

 

[zoobyshoe]

O.K. Let me just digest one thing at a time:

The article erroneously compares primary energy to secondary energy, so they are high by a factor of three. Specifically, if a nuclear plant is about 33% efficient, that means a 1 GWh electrical output is provided by a 3 GWh nuclear heat input. Worse, due to the improved efficiency of heat pumps and electric cars, a pretty significant fraction of the energy will be saved in the switch - as much as 2/3 for those uses.

So, you're saying that currently only 5 TW of the 15 TW consumed is in the form of electrical energy. And were we to do the whole 15 as electrical energy, we would only have to generate 1/3 of the remaining 10, about 3.333 TW, instead of the whole 10. Am I understanding you correctly?

 

[Ryan_m_b]

O.K. Let me just digest one thing at a time:

So, you're saying that currently only 5 TW of the 15 TW consumed is in the form of electrical energy. And were we to do the whole 15 as electrical energy, we would only have to generate 1/3 of the remaining 10, about 33.333 TW, instead of the whole 10. Am I understanding you correctly?

You're a decimal point out but I believe that's the point yes. It would be quite a challenge to switch to all electric, cars and trains not so much but airplanes and ships would be difficult. Of course they could be replaced overtime, reintroduce the airship and build far greater continental train networks (like China's proposed new Silk Road that could connect it all the way to Europe with freight train links). We could even build a 21st century version of the NS Savannah and try to get commercial nuclear shipping back on the agenda.

 

[zoobyshoe]

You're a decimal point out...

DOH! I fixed it.

but I believe that's the point yes. It would be quite a challenge to switch to all electric, cars and trains not so much but airplanes and ships would be difficult. Of course they could be replaced overtime, reintroduce the airship and build far greater continental train networks (like China's proposed new Silk Road that could connect it all the way to Europe with freight train links). We could even build a 21st century version of the NS Savannah and try to get commercial nuclear shipping back on the agenda.

You have any estimate of how much of the 15 TW is used by planes and ships? I'm curious.

 

[tom aaron]

The author lacks a sense of scale. Currently, the year builds a new coal, gas, or oil electric plant (500 MW equivalent) every 1.3 days (i.e. 131 GW new fossil fuel capacity in 2013), which doesn't include all the biomass, hydro, or nuclear plants coming online every day.

The future is bright for coal the rest of this century, especially in the big growth economies such as China and India. It will be 'the' fuel for producing electricity. A positive for coal is that it doesn't have a geopolitical variable. The big reserves are in Australia, Russia, China, Brazil, Canada, the USA.

 

[mheslep]

The future is bright for coal the rest of this century, especially in the big growth economies such as China and India. It will be 'the' fuel for producing electricity. A positive for coal is that it doesn't have a geopolitical variable. The big reserves are in Australia, Russia, China, Brazil, Canada, the USA.

Increasing coal use a century out seems unlikely. Even current figures indicate a limited outlook. Gas is replacing coal in the US (down 18%/10 years), and now even in China coal consumption for electricity seems to have finally peaked, http://www.reuters.com/article/2015/03/26/china-coal-idUSL3N0WL32720150326Add in the coal emission harms, trends toward carbon pricing, and the innovations ongoing in nuclear power (small modular, http://www.world-nuclear.org/info/Current-and-Future-Generation/Fast-Neutron-Reactors/, and molten fuel) and I don't see an outcome other that decline of coal fired electricity past, say, 2040, if that.SMR:

Small modular reactors offer the advantage of lower initial capital investment, scalability, and siting flexibility at locations unable to accommodate more traditional larger reactors. They also have the potential for enhanced safety and security.

http://www.world-nuclear.org/info/Current-and-Future-Generation/Fast-Neutron-Reactors/

The BN-800 from OKBM Afrikantov and SPbAEP, is a new more powerful (2100 MWt, 864 MWe gross, 789 MWe net) FBR [Fast Breeder Reactor], which is actually the same overall size and configuration as the BN-600. The first (and probably only Russian one) is Beloyarsk 4, which started up in mid-2014.

Premature deaths from PM due to coal combustion:

A new study has revealed the staggering cost of China’s dependence on coal to power its economy: 670,000 deaths in one year alone. ... the study found that tiny particulate pollutants, especially those smaller than 2.5 micrograms (known as PM2.5), were linked to 670,000 premature deaths from four diseases – strokes, lung cancer, coronary heart disease and chronic obstructive pulmonary disease – in China in 2012...

 

[russ_watters]

So, you're saying that currently only 5 TW of the 15 TW consumed is in the form of electrical energy

Consumed for electrical energy: The 5 TW of consumed nuclear fuel (per hour) is converted to about 2.3 TW of electricity.

And were we to do the whole 15 as electrical energy, we would only have to generate 1/3 of the remaining 10, about 3.333 TW, instead of the whole 10. Am I understanding you correctly?

It probably isn't quite that low because not all of the other energy used is used for transportation or low temperature heating. Transportation is about 25% of the total (3.8 TW) and I'm going to guess that low temperature heating applications that could use heat pumps are another 25%. That means 1/3 of 7.6 = 2.5 TW. That leaves 15-7.6-5=2.4 TW unaccounted for and let's assume that's high temperature heat. So the total generated electricity to be an all-electric world would be about 2.3+2.5+2.4 = 7.2 TW.

You have any estimate of how much of the 15 TW is used by planes and ships? I'm curious.

According to the wiki, 20% of the total is transportation. I'll take a stab at it and say planes and ships are probably 10% of transportation, or 0.3 TW.

 

[russ_watters]

It would be quite a challenge to switch to all electric, cars and trains not so much but airplanes and ships would be difficult. Of course they could be replaced overtime, reintroduce the airship and build far greater continental train networks (like China's proposed new Silk Road that could connect it all the way to Europe with freight train links). We could even build a 21st century version of the NS Savannah and try to get commercial nuclear shipping back on the agenda.

If we reaaaaly want to go as nuclear/electric as possible, I think a great many big ships could be nuclear powered. Airplanes, though, are going to be a big problem.

 

[zoobyshoe]

Consumed for electrical energy: The 5 TW of consumed nuclear fuel (per hour) is converted to about 2.3 TW of electricity.

Ah, O.K.

It probably isn't quite that low because not all of the other energy used is used for transportation or low temperature heating. Transportation is about 25% of the total (3.8 TW) and I'm going to guess that low temperature heating applications that could use heat pumps are another 25%. That means 1/3 of 7.6 = 2.5 TW. That leaves 15-7.6-5=2.4 TW unaccounted for and let's assume that's high temperature heat. So the total generated electricity to be an all-electric world would be about 2.3+2.5+2.4 = 7.2 TW.

Sticking just to how many TW of nuclear fuel will be consumed, what would that figure be after conversion to an all-electric world? Your original statement was that it won't be one-to-one because electric cars and heat pumps are more efficient. So, I'm looking for your estimate of the reduced consumed TW.

 

[russ_watters]

Sticking just to how many TW of nuclear fuel will be consumed, what would that figure be after conversion to an all-electric world? Your original statement was that it won't be one-to-one because electric cars and heat pumps are more efficient. So, I'm looking for your estimate of the reduced consumed TW.

Nuclear power is about 30% efficient, so an all-electric world of 7.2 TW requires an input of about 22 TW of nuclear fuel.

 

[tom aaron]

If we reaaaaly want to go as nuclear/electric as possible, I think a great many big ships could be nuclear powered. Airplanes, though, are going to be a big problem.

Cimmercial nuclear ships are not being built and will not be built for some time. They are not viable economically or practically.

 

[zoobyshoe]

Nuclear power is about 30% efficient, so an all-electric world of 7.2 TW requires an input of about 22 TW of nuclear fuel.

I'm very confused. I thought you started with 15 TW to get to the 7.2 TW. Working backward, it doesn't seem you could get greater than 15 TW and it should be less with your previously proposed savings by electric car and heat pump.

 

[russ_watters]

I'm very confused. I thought you started with 15 TW to get to the 7.2 TW. Working backward, it doesn't seem you could get greater than 15 TW and it should be less with your previously proposed savings by electric car and heat pump.

The author of the article mixed together input and output (primary and secondary) and I guess I haven't untangled it enough for you yet: He said you'd need 15 TW of output (which would be 45 TW of input), but based on current usage you need 7.2 TW of output (22 TW of input).

In other words, he said you'd need 15,000 nuclear reactors (at 45 GW input to get 15 GW output) but you'd really need only 7,200 reactors (22 GW input, 7.2 GW output).

 

[zoobyshoe]

The author of the article mixed together input and output (primary and secondary) and I guess I haven't untangled it enough for you yet: He said you'd need 15 TW of output (which would be 45 TW of input), but based on current usage you need 7.2 TW of output (22 TW of input).

In other words, he said you'd need 15,000 nuclear reactors (at 45 GW input to get 15 GW output) but you'd really need only 7,200 reactors (22 GW input, 7.2 GW output).

Regardless of what he said I though you were starting with 15 TW of input to get 7.2 TW output. That's what is confusing me.

 

[russ_watters]

Regardless of what he said I though you were starting with 15 TW of input to get 7.2 TW output. That's what is confusing me.

Essentially yes: I calculated 7.2 TW of output from 15 TW of input, based on my efficiency and usage assumptions/data.

The world doesn't care much about the input. Indeed, for renewable sources we generally don't even consider the input at all, since it is free and eternal. The world cares about the output. What I did, that matters for his analysis, was correct his output number (for a start). The fact that the input number goes up as a result appears to be tripping you up, but it isn't really all that important. On a day-to-day basis, we really don't care much about the input of a nuclear plant.

 

[zoobyshoe]

Essentially yes: I calculated 7.2 TW of output from 15 TW of input, based on my efficiency and usage assumptions/data.

O.K. So what you're saying is that, in the switch from current power generation to all nuclear/electric, we would have to consume more than 15 TW to get the same 7.2 TW output. Consumption would be more like 22TW.

The world doesn't care much about the input. Indeed, for renewable sources we generally don't even consider the input at all, since it is free and eternal. The world cares about the output. What I did, that matters for his analysis, was correct his output number (for a start). The fact that the input number goes up as a result appears to be tripping you up, but it isn't really all that important. On a day-to-day basis, we really don't care much about the input of a nuclear plant.

But uranium is non-renewable, so it is important. This goes to his claim that, were we to be generating the current output exclusively by nuclear we'd use up all the viable uranium in 5 years. That was my original question: how long will supplies of nuclear fuels last? If he's overestimated consumption by a factor of 3, as you say, that means we actually would have 15 years of an all nuclear/electric world before the viable uranium got used up. Not better enough to be worth correcting him, IMO. "The world," as you put it, "doesn't care about" ten more years. The world is looking for the longest lasting possible energy source. Should we invest so much in something that's just going to be fossil fuels all over again?

 

[russ_watters]

O.K. So what you're saying is that, in the switch from current power generation to all nuclear/electric, we would have to consume more than 15 TW to get the same 7.2 TW output. Consumption would be more like 22TW.

Yes.

But uranium is non-renewable, so it is important.

We're still a very long way from getting to that issue, given all the other related problems in the paper. For example, can I keep the Hoover Dam or do we have to replace that with nuclear power too?

In any case, you still aren't hearing me on why the thermal energy input itsn't important to the discussion. It will become more apparent at the end of this post.**

This goes to his claim that, were we to be generating the current output exclusively by nuclear we'd use up all the viable uranium in 5 years. That was my original question: how long will supplies of nuclear fuels last? If he's overestimated consumption by a factor of 3, as you say, that means we actually would have 15 years of an all nuclear/electric world before the viable uranium got used up. Not better enough to be worth correcting him, IMO. "The world," as you put it, "doesn't care about" ten more years. The world is looking for the longest lasting possible energy source. Should we invest so much in something that's just going to be fossil fuels all over again?

Output, right. So anyway, after I put numbers to it, he over-estimated - using his logic - by a factor of 2, not 3. But so much of the rest of the logic is bad that I still wouldn't consider 7.2 TW as a good starting point for the discussion. However, since we are on it, here's a source for the calculation of longevity, using his logic:

According to the NEA, identified uranium resources total 5.5 million metric tons, and an additional 10.5 million metric tons remain undiscovered—a roughly 230-year supply at today's consumption rate in total.

http://www.scientificamerican.com/article/how-long-will-global-uranium-deposits-last/

Currently, we have about 440 reactors. If we needed 7200, that's 440/7200*230= 14 years under current usage patterns. So that's roughly where his math comes from.

But:

Further exploration and improvements in extraction technology are likely to at least double this estimate over time.

Using more enrichment work could reduce the uranium needs of LWRs by as much as 30 percent per metric ton of LEU. And separating plutonium and uranium from spent LEU and using them to make fresh fuel could reduce requirements by another 30 percent. Taking both steps would cut the uranium requirements of an LWR in half.

So combining those two yields an additional factor of 4: now we're at 56 years.

Second, fuel-recycling fast-breeder reactors, which generate more fuel than they consume, would use less than 1 percent of the uranium needed for current LWRs.

An additional factor of 100: now we're at 5,600 years and we haven't even brought seawater into the discussion yet.

**Notice that nowhere in the post did I reference the thermal input energy of the nuclear fuel. It's very much like discussing a car's fuel efficiency in terms of miles per gallon: the usage is given in units of volume (mass for uranium) per output, so we can skip the step of calculating (by efficiency or heat capacity per gallon/ton) the input heat.

 

[zoobyshoe]

Second, fuel-recycling fast-breeder reactors, which generate more fuel than they consume, would use less than 1 percent of the uranium needed for current LWRs.

An additional factor of 100: now we're at 5,600 years and we haven't even brought seawater into the discussion yet.

O.K. Nothing gets good until breeder reactors are brought in. Then the outlook is fantastic.

What's the problem? Why aren't all nuclear reactors breeder reactors? That's an unbelievable extension of the fuel. If we had even 500 years of that, much less 5000, I'd call that "nuclear utopia."

 

[russ_watters]

O.K. Nothing gets good until breeder reactors are brought in. Then the outlook is fantastic.

What's the problem? Why aren't all nuclear reactors breeder reactors?

My understanding is that it is all about money. Once-through reactors are cheaper to build/operate.

My concern is whether the spent one-through fuel can be reprocessed and then re-used in a breeder reactor. I don't want the next 50 years of current usage to deplete what we have so much that we end up running out because we used it wrong. Someone else will have to answer that though.

Edit: Gotta love PF: When Googling "why aren't breeder reactors used more", the first hit is a PF thread discussing it:
https://www.physicsforums.com/threads/why-arent-more-breeder-reactors-being-built.509686/

 

[zoobyshoe]

My understanding is that it is all about money. Once-through reactors are cheaper to build/operate.

My concern is whether the spent one-through fuel can be reprocessed and then re-used in a breeder reactor. I don't want the next 50 years of current usage to deplete what we have so much that we end up running out because we used it wrong. Someone else will have to answer that though.

I looked through the wiki article on breeder reactors and they explain fairly well why they're not in use. You can have a look.

I agree about the next 50 years. It seems to me they ought not to be building and using any non-breeder reactors. Because they get so much more energy out of the fuel they also vastly cut down on the long-term accumulation of waste, and that has impressed many green people (according to the wiki).

Here in California the wiki says 1/5 of the electricity is nuclear. That comes from just two nuclear plants. It seems to me that from 1/5 to 1/2 of the electricity being nuclear would be a manageable level.

However, I read the article on nuclear decommissioning, and that seems to be a farce. The old plants are just sitting there for decades. They aren't cleaning them out. Part of every plant's profit is supposed to be put aside to pay for the cost of dismantling them, so it should not be a matter of money. And there should be no such thing as "entombment." Old nuclear plants can't be allowed to accumulate if people want nuclear for the long haul.

Given that, with the right usage, nuclear could last thousands of years, that objection is tentatively taken care of. A big potential fly in the ointment is accidents. Fukushima, I've been reading, played havoc with Japan's economy, not to mention the worldwide uranium market. Japan reacted by taking all their nuclear offline. A bigger potential fly is countries like Iran, who say they want nuclear power but are almost certainly going to use it to also make bombs. They're simply not going to not make bombs. Every one who can has. They won't be any different. Since breeder reactors can produce weapons grade products, it seems to me no one should be building any breeder reactors.

Contradiction intended. The upside is wonderful, the downside is horrible.

 

[Ryan_m_b]

Cimmercial nuclear ships are not being built and will not be built for some time. They are not viable economically or practically.

Actually they may be economical, one of the reasons the NS Savannah was decomissioned is because of how cheap shipping fuel was back then, apparently even by the 70s fuel costs had risen enough that Savannah would have been cheaper:
https://en.wikipedia.org/wiki/NS_Savannah#Economics_of_nuclear_propulsion