Tag Archives: Nuclear

Your Power Plant Might Have a Drinking Problem

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While at an energy conference (ARPA-E, 2014) I found out that power plants account for 40% of water draw in the US. Simply put, they use a lot of water. The good news is that it doesn't have to be fresh water. Brayton Point, for instance, uses grey water. In other words, it uses water that came from your toilets and sinks that has been reprocessed. Others use saline water from oceans (all water in the oceans is saline, cause it is salt water).

No math this time, just review the math from my thermal power plants post.

Why do power plans needs water? Cooling purposes. The way a turbine works is that high-pressure air has to drive through it. The way this happens is water is flashed to steam. Steam takes 1600x the space at 1 atmosphere compared to water. So it creates a massive pressure differential on one side of the turbine, turning the fans, turning the turbine, and generating electricity. The steam needs to be cooled on the other side to either create the vacuum that drives the pressure differential to turn the turbine, or, if it's a close cycle and the same water is used, to cool the steam back to water. It needs to be water again, otherwise it cannot expand and drive the turbine.

Schematic of a thermal power plant. It needs water to cool the water used to drive the turbine.

Okay. That was complicated. Let's break it down further. This section if very detailed, and most of you will want to skip this paragraph. Here goes: There are two major ways to run a thermal power plant. Combined cycle, and single cycle. Combined cycle is more efficient. How? It uses several turbines to extract energy rather than a single one. Think about it this way: when you have 300 degree celcius steam coming from the coal-burning reactor, it is all steam. There is no water-phase droplets in it. This is called dry steam. It can be directed to special high-efficiency turbines that can extract a lot of energy. The steam then loses pressure and temperature, and some water droplets begin to form. If this mix of steam and water were directed at the same turbine, it would pit and tear at the turbine blades, destroying it. Two things could be done with this steam. Either it could be directed to another turbine, or it may not be reused. The second turbine will be designed differently for steam that is lower pressure and lower temperature. Having multiple turbines like this increases efficiency. Inefficient plants use only one turbine

(everyone else should join back in now) Eventually you end up with a mix of water a steam. As I said before, this has to become water again, so it can expand to steam and drive turbines. Or, if a plant is doing a once-through cycle and expanding water from a stream, it needs to dump the water back into the environment. Dumping near-boiling water into the environment is a terrible idea. That would be a bit of a disaster. So, in either case, you need a lot of water from the environment to cool the water used for the steam cycle in the plant. An alternative scenario is using evaporative cooling towers. They evaporate water, which requires heat to go into the water, which then cools other water. No matter what, cooling a plant requires a lot of water.

So here we come back to the end point. Power plants use an insane amount of water. "Ahh, but Jason," you ask, "these are just thermal power plants. I use solar power. So my plant is water-efficient!"

Not so, I say! Solar plants also use water for cooling and cleaning. And this is from NYT, an ostensibly liberal paper that likes solar. This is because major solar plants use solar thermal, rather than solar PV. Solar PV is pretty much water-free, other than for cleaning mirrors. But that electricity is too expensive to be useful at the grid scale (recall from a prior post that it costs about 3-7 cents to produce a kwh of electricity, but we buy it for 20 cents, so it makes sense for us to put solar panels on our houses at the cost of 20 cents per kwh, while it doesn't make sense for power companies to use solar panels since they mark up prices 3x to get power to us).

How does this compare to coal? In the link above, we have solar power using 1.2 billion gallons a year to produce 500mw of power. Your average coal plant produces 600 watts of power. A once-through plant draws "between 70 and 80 billion" gallons a year. But a closed-cycle plant, the one that uses the same water in the plant and only uses other water for cooling at the end of the power cycle, uses 1.7 to 4 billion gallons a year. So the efficient ones are comparable to solar in water use.

So here we have a chart showing all this:

Water use by power plant type, source 

Note that you can find different graphs using different information sources, but the general point always remains: power plants use a lot of water.

Wind power, however, doesn't use water. Unfortunately, wind power is only available in a few places. How about hydro power? It passively uses water, so it doesn't really count. Great, right?

Not so fast. How much of the US power generation comes from thermal and solar sources? According to the EIA, 87%. I reproduce the info here:

In 2012, the United States generated about 4,054 billion kilowatthours of electricity.  About 68% of the electricity generated was from fossil fuel (coal, natural gas, and petroleum), with 37% attributed from coal.

Energy sources and percent share of  total electricity generation in 2012 were:

  • Coal 37%

  • Natural Gas 30%

  • Nuclear 19%

  • Hydropower 7%

  • Other Renewable 5%Petroleum 1%

    • Biomass 1.42%
    • Geothermal 0.41%
    • Solar 0.11%
    • Wind 3.46%

  • Other Gases < 1%

So yeah. Your power plant has a drinking problem.

thanks for reading!

- Jason Munster

Is Nuclear Power Really the Most Expensive Technology?

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No. It isn't.

Let's explore this more. In a country that already has a well-developed electrical grid / electricity distribution system (sorry, much of Africa), doesn't have ideas based on fear about how dangerous nuclear power is (European and North American countries, +Japan), and doesn't have a terrorism issue (proliferation), nuclear power is the cheapest and least polluting type.

Okay, so where can we find a country that meets this description? How bout Croatia, where some scientists did some probabilistic modeling on this?

From the results of the simulations it can be concluded that the distribution of levelized bus bar costs for the combined cycle gas plant is in the range 4.5–8 US cents/kWh, with a most probable value of about 5.8 US cents/kWh; for coal-fired plants the corresponding values are 4.5–6.3 US cents/kWh and 5.2 US cents/kWh and for the nuclear power plant the corresponding values are in the range 4.2–5.8 US cents/kWh and a most probable value of about 4.8 US cents/kWh.

Let me sum this up. In Croatia, nuclear power is likely going to be the cheapest source. Plus is doesn't pollute and kill people like gas or coal.

Admit it, you needed this.

Why do we face a different situation in the US and Europe? Easy. I've mentioned it before. There is so much concern about the safety of nuclear power that each construction gets mired in legal battles. The legal battles themselves don't cost much. What costs a ton is that these power plants took out $8 billion in loans, meant to be paid back over 10 years. Those loans accrue interest. If legal hurtles slow the construction of the plant down and it takes 15 years instead, those extra 5 years of loans are gonna have several extra billions in interest to pay. Suddenly the cost of power produced goes up.

These costs need to be paid back. The only way to pay back higher than anticipated costs would be to charge more for nuclear power.

So it's safe to say that stalling the construction of a nuclear power plant can effectively prevent it from ever getting built. Now we are in a situation where no one wants to fund a power plant, because the chance of it being slowed and made unprofitable is a bit higher.

Sometimes there are just plain time overruns. The US hasn't build nuclear power plants in years. Our companies barely know how to do it. Our people haven't been trained in colleges and universities to build nuclear power plants. We just don't have the nuclear engineers we would need to make a nuclear renaissance happen, and we'd need several nuclear power plants built before we finally get the hang of it. So there will be a learning curve. Would you want to fund that learning curve? Probably not when natural gas is so cheap in the US.

Are we gonna get there any time soon? Not without a major policy shift. Let's look at planned nuclear power plants worldwide:

Planned nuclear power plants. Image mine, constructed from data available at

Planned nuclear power plants. Image mine, constructed from data available  here

So um... Good job, China. US? Not so much. 32 of the 72 nuclear power plants scheduled to come on-line in the next 5 years are in China. 4 are in the US.

Nuclear power will be more expensive than gas (and coal) power in the US unless 3 things happen:

1. We account for the annual loss of life and increase in asthma and heart disease associated with gas power plants.

2. We start building nuclear power plants now, training a cadre of engineers and speciality construction personnel to finish power plants quickly, safely, properly, and on time (the first few will be finished slowly, behind schedule, but still safe and properly complete, cause lots of eyes will be on them)

3. We continue to build enough of them so that the future ones are build on time and for less expense, driving down the cost of nuclear power to competitive levels (especially when accounting for the external costs of pollution and CO2 from gas and coal).

Thanks for reading!

- Jason Munster

 

Nuclear Power: Savings lives

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Nuclear power has saved over 1.8 million lives by replacing fossil fuel power sources.

A nuclear power plant!

I've mentioned that fossil fuel power plants kill people and shorten lives by emitting not only particulate matter and smog normally associated with pollution, but also NOx (natural gas power plants produce almost no particulate matter, but any time anything is combusted, the combustion process in a nitrogen rich atmosphere (78% on Earth) produces NOx, so natural gas power plants do produce NOx).

Coal fired power plants, even clean ones, belch yuckies into the air.

Shortly after harping on exactly this for several posts, a journal article came out that exonerated my aggressive stance on how nuclear power saves lives rather than ending them through nuclear disasters. Nuclear power has saved over 1.8 million lives, according to this peer-reviewed research. The authors didn't include long-term health ailments and non-death causing heart attacks related to climate change. Only death: full stop. They go on to say that replacing nuclear power with natural gas would cause 400,000 deaths by 2050. Replacing them with coal would cause 7 million. Meanwhile, the best estimates of long-term deaths caused by radiation exposure from the Chernobyl meltdown, mining uranium, and building nuclear power plants stands at about 5,000 No deaths arose from Three Mile Island or Fukushima. What about the radiation that Fukushima is spilling out into the ocean? It's less than 1/20th the radiation levels found in a banana.

I am a banana. Eating one of me makes you ingest more radiation than Fukushima ever will.

I am a banana. Eating one of me makes you ingest more radiation than Fukushima ever will.

Critics are quick to point out that renewables like wind are cheaper and more effective at reducing CO2 emissions than nuclear. Great. Let's build more wind power. Except that there are not sufficiently good places to make wind effectively and cheaply. In an exhaustive (and depressing) article on the state of nuclear energy construction, it is pointed out that Germany has an installed capacity (recall, installed capacity is simply the name-plate power generation of a plant/turbine at best-case scenario) of 76GW of renewable energy. They then compared this to all of France's installed capacity of Nuclear at 63.1 GW. But, as we have talked about, renewables don't always work. While France's nuclear generators put out 407 TWh in 2012, Germany's renewables generated 136 TWh despite their larger capacity.

"Except like Jason's former manager at JPMorgan, I only work under ideal conditions!"

"Except like Jason's former manager at JPMorgan, I only work under ideal conditions!"

Moreover, Germany pledged to phase out nuclear power after Fukushima. What did they replace it with? Not renewables. Coal fired power plants. Meanwhile, as the US expands power generation from natural gas and ceased buying coal from the US, US coal producers are finding a new market for coal in Germany.

So let's look at Fukushima a bit more. Several things are bad about fukushima. First, it melted down when a tsunami overtopped its protective walls. The US Nuclear Regulatory Commission (NRC) had told Japan 20 years ago that their Fukushima walls were too low and they could be overtopped by a very realistic earthquake scenario. And now after the disaster, groundwater contamination with (less than 1/20th of a banana's levels) radiation is all a concern. Guess what? The NRC warned Fukushima to get their groundwater issue under control three years before the Fukushima meltdown.

That's right. The US NRC predicted that Fukushima was going to happen, and told Japan to get their house in order.

NRC: Telling Japan what to do since 1980. "We don't have much of a job to do in the US anymore since we haven't built a power plant in decades"

The US has a nuclear meltdown, too. You know what the consequences were? Pretty much nothing. It cost a billion dollar to clean up. That is a huge sum. But the meltdown was well-handled. And a lot was learned from the meltdown.

My point is, the US has it's matters sorted out when it comes to nuclear safety. And we are good at identifying risks in other parts of the world.

Finally, here's the big one, new reactor designs wouldn't allow for either three mile island or Fukushima to happen. With these new reactors, in the event of mechanical failure of the passive systems, the worst case scenario of the new designs is that it would take 3 full days before even needing to worry about meltdown beginning, leaving plenty of time to deal with the situation.

So yes. There are risks with nuclear. But there are guaranteed deaths with coal and natural gas.

The best solution by far is avoiding building new power plants and to massively increase efficiency and conservation. But people are slow at changing, and we aren't gonna change our lifestyles fast enough in the western world to avoid expansion of power use, and the developing world needs to build a ton of power capacity.

So let's stop being scared of nuclear power, cause it's saving lives rather than costing them.

Thanks for reading,

- Jason Munster

Appendix

Oh, but what is this section? Just a bunch of extra information. Check out how long it takes for various countries to build nuclear reactors:

What are Pakistan and India doing that they can build nukes in 5 years?!?

Average, min, and max times of nuclear plant construction for countries that have built them. Source

Hokay, so. I need to acknowledge the bad parts of nuclear power. The real ones, not the fear-mongering that happens.

First, nuclear power is more expensive than on-shore wind (which is a limited resource, there are not infinite good places to put wind farms), coal, and natural gas. There is no doubt about that. If we switched everything to nuclear, many parts of the US that don't have high electricity prices will experience a rate shock. That is, their electricity bills will rise. But hey, remember what we said earlier about efficiency and conservation being the best way to save lives and to arrest climate change? Slightly higher electricity prices would promote this conservation. The initial rate shock would be a bit of an issue, but I am betting that nuclear power's opponents overstate it.

Second, there is an alternative to nuclear that I want to acknowledge, with a caveat. Renewables can't provide baseload power. But renewables paired with load-following natural-gas fired plants can (recall from a prior article that gas turbine based power plants can spin up very fast, and no other major power plant type can) (we don't count hydro as a major power type because we can't build more hydro in the US, we are tapped [punny]). This is by far better than coal, and better than gas alone. But it still burns gas, which produces CO2 and kills people and causes asthma.

Nuclear Reactors Final

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I am getting bored of this topic, and I want to get to wind-solar-hydro so I can finish up with the energy technology stuff and write varied stuff. So I am going to compress it a lot. If anyone wants to see it expanded, let me know and I will take care of it later.

This post is about breeder reactors, thorium reactors, preventing nuclear proliferation, how the electricity costs stack up to other power plants, and why nuclear power is so expensive.

Nuclear power is expensive because the up-front costs are massive. The cleanest and most efficient coal fired power plants might cost a billion dollars to build. It might take 5 years to build it. Nuclear power plants seem to cost about $8 billion to build with all the safety features they use to prevent nuclear meltdowns (seriously, the new tech is very safe, and it shows in the cost). And they seem to take 8-15 years to build, depending on how much Greenpeace or pretty much every other group tries to stop construction via litigation. In other words, they take out an $8B loan and accrue interest for 8-15 years before they can start paying it back. Stuff costs a lot. Why do it? Cause nuclear waste can be contained, unlike the NOx and CO2 from natural gas and coal plants. Also, South Korea thinks it can build a nuclear plant a nuclear power plant in a short amount of time for only $5 billion. United Arab Emirates decided this was a good idea, and is buying four South Korean nuclear reactors to desalinate water.

Schematic of the South Korean nuclear power plant to be built in the United Arab Emirates, from link above.

The US Energy Administration Administration agrees that nuclear power is now less expensive than it used to be. I have ripped a table straight off their web page that shows it (see, I really am getting lazy in this post).

Table 1. Estimated levelized cost of new generation resources, 2018 
U.S. average levelized costs (2011 $/megawatthour) for plants entering service in 2018
Plant type Capacity factor (%) Levelized capital cost Fixed O&M Variable O&M (including fuel) Transmission investment Total system levelized cost
Dispatchable Technologies
Conventional Coal 85 65.7 4.1 29.2 1.2 100.1
Advanced Coal 85 84.4 6.8 30.7 1.2 123.0
Advanced Coal with CCS 85 88.4 8.8 37.2 1.2 135.5
Natural Gas-fired
Conventional Combined Cycle 87 15.8 1.7 48.4 1.2 67.1
Advanced Combined Cycle 87 17.4 2.0 45.0 1.2 65.6
Advanced CC with CCS 87 34.0 4.1 54.1 1.2 93.4
Conventional Combustion Turbine 30 44.2 2.7 80.0 3.4 130.3
Advanced Combustion Turbine 30 30.4 2.6 68.2 3.4 104.6
Advanced Nuclear 90 83.4 11.6 12.3 1.1 108.4
Geothermal 92 76.2 12.0 0.0 1.4 89.6
Biomass 83 53.2 14.3 42.3 1.2 111.0
Non-Dispatchable Technologies
Wind 34 70.3 13.1 0.0 3.2 86.6
Wind-Offshore 37 193.4 22.4 0.0 5.7 221.5
Solar PV1 25 130.4 9.9 0.0 4.0 144.3
Solar Thermal 20 214.2 41.4 0.0 5.9 261.5
Hydro2 52 78.1 4.1 6.1 2.0 90.3

 

Note that last column is $ per megawatt hour. It is the bottom line cost of producing power from that plant. First, what is dispatchable vs non-dispatchable? Dispatchable means you get it whenever you want it. You can ramp it up or down however you please. Non-dispatchable means that you depend on external factors, like the fickle winds of.. well.. winds?

Tangent! Winds are really just redistribution of energy from the equator to the poles. The sun shines more at the equator, heating it up, and then energy likes to move from areas of high energy to areas of low energy, so it does it using wind. And sometimes hurricanes. So really, wind power is just really inefficient solar power. You know what else is really inefficient (and slow) solar power? Hydrocarbons and coal. Cause they are really just buried plant and algae matter and such. That is tens to hundreds of millions of years old. So, coal and oil are really just really old, slow, and dirty solar power. Tangent done!

Tangent picture? This shows how the equator heats more than the rest of the earth. These extra heat has to redistribute to be more even. Hurricanes start near the equator cause of the heat there, then move away from it. from: http://oceanworld.tamu.edu/resources/oceanography-book/oceansandclimate.htm

Nuclear power is almost as cheap as coal power, and cheaper than clean coal (note, clean coal still produces a ton of CO and NO)! What gives? How is nuclear so inexpensive? Well, we haven't built a nuclear power plant in the US in years. We don't know what it will actually cost. Those are just estimates. Also, people are quite scared of nuclear power. The cost of building nuclear power rises when you have environmentalists and NIMBY folks suing the pants off nuclear power developers. But let's make one thing clear: if the new generation of nuclear power plants are as inexpensive as they are supposed to be, the power is less expensive that all other power plants other than natural gas (note: the US does not have capacity to build more hydro power), and less expensive than even that if you account for NO produced by and methane leaks associated with natural gas power (methane production and transport will always have leaks, and it is 23x as powerful a greenhouse agent as CO2).

Let's look at a few more things on the chart above. Remember when I said natural gas got cheap? Look at how cheap it is to produce power from natural gas on the chart above. Think anyone is building nuclear, solar, or offshore wind when you can build and deploy reliable natural gas power? Somehow, the answer to this is yes. Yes, people are building all these things, despite being expensive. Which is kind of cool.

Before moving away from costs, look at the variable costs. The variable costs are high for everything except renewables and nuclear. Why is this? Cause renewables and nuclear don't really use fuel. Yes, a nuclear plant uses fuel, but it costs almost nothing relative to the labor and the capital costs. All the cost of these is upfront CAPEX (capital expense), and then you get free power.

Finally, lets take a really close look at the variable costs. This link is pretty sweet for those of you interested. It contains variable costs for each power source. You can see that fuel is the bulk of cost of fossil steam plants, but less than a quarter of the total cost of nuclear, and nuclear fuel is 1/4 the price per energy unit than even dirt cheap natural gas.

Enough about costs! Onto breeder reactors!

In the first post I mentioned that one part of nuclear reactions is to give off neutrons. Sometimes instead of a neutron splitting an atom, the atom absorbs it. U-235 is the uranium we use in nuclear reactors. U-238 doesn't produce as much heat, cause it doesn't like to decay as fast, so it isn't viable nuclear fuel. Or is it?! U-238 is like a catcher in baseball. Except it catches neutrons. And then it incorporates them into its nucleus to become U-239. In other words, it really isn't like a catcher in baseball.

The breeder reaction series. From: http://nuclearpowertraining.tpub.com/h1019v1/css/h1019v1_76.htm

What's special about U-239? It decays rapidly through a special type of decay to become neptunium-239 and eventually plutonium 239! This process can extract up to 100x the energy from nuclear fuel. You know what's magic about that? Less nuclear waste produced. Also, you produce a ton of nuclear fuel this way. You can also use thorium-232, which then becomes uranium-233 after absorbing a neutron, which can in turn be used for nuclear fuel. Thorium is very cheap and very abundant. So the plutonium and uranium that is magically created through awesomely manipulating nuclear forces is then used in nuclear thermal reactors to produce power.

Nuclear proliferation!

Having a nuclear power plant does not mean you can make nuclear bombs. Nuclear bombs required U-235 enriched to a very high level. What exactly is enrichment? Natural uranium is less than a few percent U-235, the rest is U-238. The uranium comes as a solid, and is processed by making it dance with a bunch of flourine. UF is produced, which is gasified uranium. The U-238 is slightly heavier than U-235, so it very very slowly settles to the "bottom" if you spin it very fast in centrifuges. Once you have enriched it to somewhere between 5 and 8%, U-235, it is good to go into a reactor and make energy. To make a bomb, you have to enrich it to around 90%. Enriching it further gets exponentionally more difficult. Getting from 50% to 70% is much more difficult than getting it from 10% to 50%. So making bombs is hard.

What about plutonium? Seems like any fool can make plutonium. And in fact, they can! All you have to do it get some U-235, wrap it in U-238, and you have make a breeder reactor in your back yard! This seriously happened. Someone made a breeder reactor in their garage at 17. And this wasn't one of those kids that comes from a brilliant family with a ton of money that goes to work in a world famous lab and 'discovers' a new technique under the watchful eye of one of the most brilliant researchers in the world. This was your every day kid who was just really interested in something.

Except that building a nuclear weapon from plutonium is even more difficult than from uranium. Cause when you make the plutonium, you always get a large amount of another plutonium isotope. The other isotope loves to go critical much earlier than Pu-239. Remember what happens to a potentially critical nuclear reaction when the fuel gets split up? No? Remember what happened to Chernobyl when a small gas explosion spread the core out everywhere? It completely shuts down the critical reaction. In other words, plutonium loves to accidentally blow up to early and just spread itself around without going critical. Not much of a weapon there. How do we have plutonium bombs then? Really smart people made special triggering mechanisms to make this happen. How do they do this? I dunno. If I did, I wouldn't be out in public writing a blog, I'd be doing super secret awesome research somewhere.

Turns out that only the US and a handful of other countries have figured this one out. So while any old fool can make a breeder reactor, the combined science of most nations is not good enough to figure out how to do it.

One last thing. If nuclear power is so difficult, how did so many countries get it? Well, US and Russia developed it. The US gave it to China at some point to balance some power issues with the Soviet Union. The US gave it to several other allies as well. The Soviet union gave it out some, too. China then distributed to crazies like North Korea years later, and Pakistan and India were given it through similar pathways. In other words, it is still pretty difficult to develop.

Hey, I just covered 4 whole things in one post, and managed to get more terrible jokes in. Awesome.

Aww darn, I forgot to include the small amount of original research I did on this topic. Next article

Thanks for reading

-Jason

Nuclear Disasters

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Nuclear meltdowns are scary things. Most people don't understand what a nuclear reaction is. They just know it is big. Three major meltdowns have occurred: Three Mile Island, Chernobyl, and Fukushima. Most people know about the last two; Chernobyl was a true disaster, and Fukushima still is leaking radiation into the ocean. Fukushima in particular would have been easy to prevent at two stages: building a higher protective wall around the plant, and flooding the reactor early. Zero people died in Fukushima and Three Mile. Compare that to the disaster that is 11,000 premature deaths and 24,000 heart attacks per year caused in the US alone by burning coal. Moreover, modern nuclear power plants are designed to prevent these accidents from happening.

Three Mile Island

Three Mile Island occurred in 1979 in PA. A problem began, and human error allowed it to persist. A pressure release valve was stuck open. The valve allowed some irradiated coolant to escape. A poorly trained operator was not familiar with the interface and confused the warning for the loss of coolant (the human-computer interfaces were new and not well designed). When the reactor began to overheat, the control rods were fully inserted. Remnant decay heat persisted, but the chain reaction was halted. Unfortunately, the plant had its emergency cooling pumps shut down for maintenance. You would think that there would be a rule saying that if the emergency cooling pumps were shut down for maintenance, that the plant itself should shut down, right? Well, there was such a rule. It is one the the key rules that the Nuclear Regulatory Commission laid down. The plant was in violation of this key rule.

A series of events followed where the cladding of the nuclear fuel rods melted. Some radioactive gas was released into the environment. The average person living within a 10 mile radius was dosed with about 8 millirem (a measure of radioactivity). This is the equivalent to a single chest x-ray. The average person living in a high altitude city, like Denver, CO, gets 100 extra mrem a year just by being closer to the sun. The average US citizen gets 300mrem a year from the environment. A round-trip flight from New York to Europe will dose you with 3mrem. In other words, this was negligible. The consensus of epidemiological studies since shows no increase in cancer rates from this event.

One a 1-10 screw up scale, this was about a 6. The operators failed to recognize it as a loss-of-coolant event, and allowed the core to overheat. Not a single person died as a result. All the containment methods, which are 1970s technology and design, worked. The only loss was an economic one. To the tune of about $2 billion.

Chernobyl

Location of the Chernobyl plant, and the spread of radiation contamination afterwards

Location of the Chernobyl plant, and the spread of radiation contamination afterwards

Chernobyl. April 26, 1986. A real, unshielded nuclear meltdown occurred. Chernobyl did not have the containment building that most other reactors had. In other words, outside of the reactor pressure vessel, there was nothing to contain leaks or explosions. 31 people died that night, and most serious epidemiological studies indicate the total death toll (counting increased incidences of cancer) has caused about 5000 premature deaths in Europe to date. Total increase in cancer by 2065 is estimated to be about 40,000 (not all of these lead to death). Let's be very clear on this. The worst nuclear disaster in history, which has proven to be avoidable just by building a concrete building around it, will have caused 40,000 cancer-related premature deaths in 80 years. This also happens to be the sum total of deaths caused by nuclear. If you look at actual deaths caused in the US alone by coal in the past 80 years, you are looking at numbers close to 1.6 million (about 20k deaths annually in the 70 years prior to strict limitations in 2004, 11k annually since then). This is a conservative estimate, not accounting for likely increase in death through the years when there were no emissions limitations. The number of heart attacks caused by coal emissions over this period is likely double this. Also compare those 40,000 increased cancer incidences to the literally hundreds of millions of unrelated cancer cases that will have occurred over that same 80 year period in Europe alone. 40,000 compared to 1,600,000, the latter produced in an era of much lower population, is pretty staggering. These numbers speak for themselves. Also compare this to the 17,000 deaths that have occurred from airplanes in the 13 years of 1999-2011.

Now that we know the death toll of Chernobyl, and we have a comparison of other deaths, let's talk about this catastrophic failure. It was a very complicated series of events, one that I could write several posts about. Instead, I will direct you to the Wikipedia article. The short version is that they were running some safety tests. They were instructed by Kiev to hold off their tests by 12 hours, making the test run during the overnight shift instead of the shift that was trained to run the test. At the end of the safety tests, they tried to insert the control rods back into the core. Because of several anomalies caused by having moved the test time, there was a minor explosion in the core as the rods were inserted. They were only 1/3 of the way in, and they broke off, preventing full insertion. Unlike modern control rods, these control rods were made of graphite. Graphite is a good moderator, but it also burns really well at high temperature. The lack of control rods allowed a small nuclear chain reaction to happen. This reaction was self-limiting; the energy from the reaction blew the fuel rods apart, making it so there was not enough uranium in one place to continue the reaction. The explosion, however, ripped through the pressure vessel and allowed atmosphere to come in. Air contains O2. Graphite is carbon. Carbon is what burns in coal to produce heat. The heat of the overheated reactor combined with the influx of oxygen was enough to make the graphite burn. This helped spread out the radioactive material. There was no giant concrete containment structure to contain it (remember how Three Mile island had a containment structure, and it worked? So did Fukushima.). The burning graphite spread radioactive material very far.

On a 1 to 10 scale of screw up, this was a 10. Bad idea to do safety tests.

Fukushima

The reactor that blew. https://share.sandia.gov/news/resources/news_releases/images/2012/Fukushima.jpg

Fukushima is still being studied. The latest reports indicate that people living within the immediate vicinity of the plant received 10mrem dosing. Again, this is the dosage a person gets every 10 days just for living on Earth. There have been no increases in cancer, nor is there expected to be any. There are some serious ecological impacts to be dealt with. There are some regions in the immediate vicinity of Fukushima that won't be able to produce agriculture for as much as 20 years. Other areas are uninhabitable for that amount of time. The region groundwater around Fukushima Daiichi is still contaminated and likely will be until a 100 foot deep wall of concrete and steel is built as a containment wall around it. It still leaks radiation into the ocean today. Nonetheless, no one has died from the incident. It could have easily been prevented in two circumstances. An event like this wouldn't even be possible in a modern nuclear power plant, as we will see.

Fukushima Daiichi's emergency backup generators kicked in after the 9.1 magnitude earthquake shut down the power grid. The ensuing tidal wave washed over the protective barrier of the power plant and inundated the generators. They shut down. The emergency backup batteries lasted 8 hours. Then cooling pumps stopped. This is known as a triple power failure. It is something that had been written about in the past for many plants, with measures taken against in. It was something written about with this particular plant, with no measures taken against it. TEPCO was warned by a governmental agency two years prior to this event that their sea walls were not tall enough.

Fukushima Location. http://www.cdc.gov/niosh/topics/radiation/images/JapanMap.png

What happened next is that the core melted down. They should have flooded the core with seawater and destroyed the reactor (seawater is pretty corrosive), but the plant operator thought they could contain the situation without destroying the reactor. They were wrong, and the consequences were a full nuclear meltdown. Heat and pressure built up and the explosion could not be easily contained. The surrounding area had to be evacuated. Even in all of this mess, no one was exposed to sufficient radiation to matter, and the situation is handled. It is an environmental disaster, yes. But let's compare this to coal fired power plants. Where do you think all that mercury in the fish over the entire planet comes from? Coal fired power plants.

More importantly, the new generation of power plants would prevent this type of event from happening. The emergency cooling water reservoir is contained above the core. In the event of power loss, the water can dump into the reactor using gravity. No Fukushima, no explosion and radiation.

This post is getting long, but before we go, let's visit one point we have touched on. Nuclear power has risks. Coal power has definite consequences. Far more people die from coal than from nuclear power. Grossly more. Nuclear is still scary to most people, and likely not to win the PR battle in the short run. And all these safety features make nuclear power pretty expensive. What are the other options? We haven't discussed hydro yet, nor wind and solar. For now, let's leave it between the big power plants. I personally believe that Fukushima was the last major learning point in nuclear power. Coal power is pretty gnarly, even at its best. Another solution is to use less energy. This is pretty tough one to make happen, and I don't see it happening any time soon. A post far in the future will grapple some of this.

That's all for now. Thanks for reading my longest article to date.

-Jason Munster

Nuclear Power Safety

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Same nuclear power plant as in last post

Nuclear power plant safety has come on a long way. In the first two generations of plants, the engineers were constantly running around to keep the plant running safely. In the newer generation, the engineers main task is to prevent the power plant from shutting itself down. In other words, the plants are designed to shut themselves down safely if someone isn't there telling it not to every few minutes. Sorry, no pictures and no math this time!

Nuclear power plants have melted down. Chernobyl was a disaster. It didn't contain safety measures like a secondary containment vessel. Three mile island and Fukushima are metldowns that were contained. No one died in either three mile island or fukushima, and that no one suffered from radioactivity damage from either event. The protective measures worked. More on this later, though. This post is about these protective measures.

The first safety measure of a nuclear reactor is the control rods. In the prior post, I mentioned that a nuclear reaction occurs when a neutron is given off, which then hits another uranium molecule, causing it to split and give off more neutrons. Control rods moderate this chain reaction. If a neutron hits a control rod molecule instead of another U-235 molecule, that neutron will not participate in and prolong the chain reaction. The control rods can be moved in and out of the reactor. The further in they are, the more likely that they will interfere with the chain reaction. Dropping them in fully can shut down the chain reaction. Pulling them out fully lets the reaction occur rapidly. Control rods can be made of several different materials, each with different properties. This becomes important, because Chernobyl used a type that burned, and Fukushima used a type that makes hydrogen from water under high heat.

The next safety measure is the nuclear pressure vessel. These behemoths have nearly 7 inch thick steel walls. They contain the pressure of the heated water (or other heated material) in the core. In the event of a reactor meltdown, it can contain a low-level meltdown.

The next layer of safety is a giant concrete containment vessel. If the pressure vessel ruptures or melts (yes, a runaway nuclear reaction can melt through the containment vessel), the concrete will contain the blast. It also protects the power plant from outside threats, like small airplanes and jet fighters crashing into it.

A point to ponder: Protecting against a fully loaded passenger aircraft is not in the cards. That being said, most coal fired power plants have 30 day supplies of coal. Or, you know, 280,000 tons of coal. This would be easier for a large airplane to hit, being a giant pile as opposed to a small reactor. This coal is meant to be burnt in controlled conditions where it is entirely burnt all the bad stuff is scrubbed. Burning it outside would be an environmental disaster, and would surely cause more deaths than Fukushima and Three Mile Island (again, 0 for these two incidents). So yeah, a nuclear plant is a target, but so is a coal plant. I really hope writing about this doesn't get me added to some list somewhere.

Getting back on track, most nuclear power plants have an emergency cooling supply that can drown the reactor and cool the reaction. It renders the reactor inoperable, and the reactor will never produce power again, but it can prevent a meltdown. Older generations relied on a series of pumps to pump water in. In the event of total power failure, these won't work. Newer generations have changed this. There is a cistern of water, large enough to drown the entire reactor core, seated above the core. As long as there is electricity applied to the valve, it stays closed and the water stays where it is. In the event of a complete power failure, the valve no longer receives the signal to stay closed. It opens. The cistern of water drains into the reactor, melting it.

The next level of protection is in case of a full meltdown of the core, and a breach of the pressure vessel. Should this happen, there is a massive concrete slab that will catch the molten material and contain it. As in the case above, a massive quantity of water will drop on the material to help cool it. Some of the newest designs even have cooling pipes in the concrete that catches the molten core.

Finally, in the event of too much pressure building up in the concrete protective structure, all new nuclear power plants are required to have filtered vents to release pressure. In other words, if water starts boiling in the reactor and pressure becomes too high, the extra pressure will be released through a vent that will filter our all of the radioactive material.

Clearly all this is very expensive. In fact, the major cost of a nuclear power plant is building things that prevent any problems in the worst-case scenarios. And, as I mentioned before, they work pretty darn well in the case of epic fail meltdown.

So that's about it. The rest of the safety stuff is all related to non-proliferation to terrorist groups, and that is not science stuff, so I am going to ignore it for this post.

Thanks for reading!

-jason munster

Nuclear Power Plants!

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Pretty nuclear power

A nuclear power plant and its cooling towers. Source: nuclear regulatory commission

Excellent news! I figured out inline LaTeX in wordpress, so my equations look even more baller.

If you had to guess how many pounds of coal you needed to equal the power output of a single pound of uranium for a nuclear reactor, what would you guess? 100 pounds? 1000? Try 3,000,000 pounds of coal to equal the energy in one pound of uranium. The energy contained in a nuclear reaction is immense. In a timely fashion, XKCD recently made a post about this:

Seriously. Read it all. And make sure you know what alt text is before you read it

XKCD comic about log scales. More importantly, it shows uranium is gigantically more energetic than coal. Also, note that my coal calculation have more power than his. It's cause I assumed a better burning, cleaner coal in order to be nice to coal. It's old and it's days are numbered, so we should be nice to it, no? Check out xkcd.com

This will be a three part series about nuclear power. This post gives a very brief description of how a nuclear reactor works. The next two will be what happened in Chernobyl and Fukushima, and another on how the newest generation  of nuclear reactors are much more safe than the older ones.

A nuclear power plant is basically your standard steam or thermal power plant. Except that it is surrounded by a ton of protection to prevent or contain explosions and nuclear fallout. Unfortunately, Cold War Russia forgot all this protection, which is why Chernobyl turned into a huge mess. Fortunately, Fukushima did have these protective measures, and no one got lethally dosed. More on this in a future post.

First, some math!

In the coal post, we showed that (extremely high quality) coal contains 34MJ per kg. Let’s figure out how much energy is in a kg of uranium!

Radiation warning symbol. Uranium is radioactive.

Radiation warning symbol. Uranium is radioactive.

We learned as kids that mass and energy are conserved. They are related by Einstein’s equation E=MC^2. When a nuclear reaction happens, the mass of resulting elements are lower than the mass of the starting elements. This energy has to be released as heat. For a nuclear reaction of U-235, ~202 MeV are released (eV is electron-volts, a unit of energy) per atom.

Seriously, how good does this math look right now?

This doesn’t sound like much, considering coal has . Lets continue with maths.

Remember Avogadro’s number? ? It’s the number of molecules to make X grams of a molecule, where X is the atomic mass. It turns out the atomic mass of U-235 is 235. Funny how that works, right?

Hokay.

This is 2.4 million times the energy density of very good coal. It is closer to 3.5 million times the energy density of coal that is typically used to generate electricity.

Nuclear power!

A nuclear power plant is a thermal power plant. It harnesses the heat of a nuclear reaction to create steam.

Uranium-235 decays naturally, releasing the massive amount of energy described above. One of the decay products, a neutron, can hit another U-235, causing that to decay. Each decay produces several neutrons. The process becomes a chain reaction that can grow exponentially.

A chain reaction image courtesy of the Nuclear Regulatory Commission

A chain reaction image courtesy of the Nuclear Regulatory Commission

U-235 is formed into pellets, and then into rods, which are put in the reactor core. The decays produce heat, which is absorbed by water, which then drives the steam cycle. To prevent a runaway reaction, control rods are inserted between the U-235 rods. These control rods absorb neutrons from the nuclear decay. Once absorbed, these neutrons cannot break another U-235. The reaction becomes controlled.

That is pretty much it. There are a ton of safety measures beyond this, however.

These reactions are contained within a reactor pressure vessel. The vessel is designed to contain the reaction. To reduce maintenance, these pressure vessels need to be a single piece. Currently only Japan, Russia, and China have the capability of building the massive pressure vessels needed for nuclear power plants. South Korea will have this capability within the next year.

Another NRC picture. Schematic block diagram of a nuclear reactor. A pressure vessel that is a single piece requires less maintenance.

The pressure vessel is the second line of defense against a reactor meltdown, after the control rods. Outside of this is a huge concrete containment structure that allows the pressure vessel to survive an earthquake, bomb, or airliner crash. It also prevents the escape of nuclear gases in the event of an accident. Chernobyl did not have one of these. All current nuclear powerplants do, making Chernobyl a non-repeating event.

A nuclear plant will produce about 20 metric tons of nuclear waste per year. The waste cools in a pool for spent fuel rods for a couple of years before being mixed with glass and stored in massive concrete cooling structures.

Can Nuclear Power Alone Replace Fossil Fuels? Unfortunately, probably not in the short term.

If the US wanted to replace all of its fossil fuel electricity with nuclear power in the next 20 years, it would have to build a lot of nuclear power plants. The US currently uses more than 250GW of installed capacity of fossil fuels for electricity. If this grows at 3% per year, we will need more than 450GW of power from this source. We would need to build 450 1GW nuclear reactors in 20 years, or nearly one every two weeks. Considering we haven't built a nuclear reactor from start to finish in over four decades, this is not an immediately solution. We have to get on building nuclear right off if we want this to be any sort of solution.

Base load electricity vs Peak Load

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Base load Electricity vs. Peak Electricity

I was writing a post about how a coal fired power plant works, and then realized that I needed to describe more about our electrical power grid and how each power component fits into it. Also, speaking of power grids, there is an excellent game called Power Grid that anyone who knows me should come over and play.

Base load electricity!

Electricity_demand_profile_NE

Pictured above is the electricity demand for an October day in New England. Notice that throughout the middle of the night, the electricity demand is roughly 10GW. Throughout the day it ramps past 15GW. Base load electricity in this case is 10GW. It is the minimum amount of electricity needed at any point. All power plants that provide base load electricity will run 24 hours a day. Base load power plants need to be very reliable so they don’t shut down unexpectedly.

Base load electricity requirements do change throughout the year. During the sweltering summer in southern states, air conditioners are constantly on, drawing more electricity in the summer. In some countries, there is not enough base load electricity to provide electricity in the worst months. In Pakistan, for instance, there will not be viable electricity more than 4 hours per day for several months. We will return to base load electricity soon.

Peak electricity is whatever is above base load. In the above figure, it is the all the extra stuff from 10GW to 15GW. Peaking power presents special challenges, because it can be unpredictable. If the temperature is several degrees warmer in a summer afternoon, the peak electricity requirements can be greater than predicted. Power plants that are capable of ramping up power quickly will compensate for peak electricity demand. “Ramp Rate” is the MW per minute a turbine can spin up at. This ramp rate is important, and we will get back to that almost immediately.

A brief interlude on cost! Base load electricity tends to be pretty cheap. A base load plant will not get paid as much for electricity. Peaking plants are designed to turn on only when electricity is more in demand. This means they get to charge more! A peaking power plant will figuratively not get out of bed in the morning for less than 50% above base load electricity rates.

Okay so here is where things get somewhat more complicated. Some power plants can never be taken offline in short order (think nuclear). Thermal power plants tend to take longer to create enough heat and steam to spin up their turbines, including both coal and nuclear, and some types of natural gas. Anything that takes a long time to spin up is meant for base load power.

A nuclear power plant with the nuclear plant (small rectangle buildings and one cylindrical building) and a cooling tower (big steaming parabolic-shaped tower). Nuclear power plants never shut down, except to change fuel rods.

A nuclear power plant with the nuclear plant (small rectangle buildings and one cylindrical building) and a cooling tower (big steaming parabolic-shaped tower). Nuclear power plants never shut down, except to change fuel rods.

Other types spin up very quickly. For some, like natural gas plants that are designed to deal only with the peak electricity use, a typical turbine can ramp at a massive 20MW per minute (most plants have several turbines, and can ramp at multiples of 20MW!). Why don’t we use these for base load, since they seem so flexible? These fast-ramping systems are not designed to be always-on. They accrue damage if they do not have downtime.

Let’s talk about renewables. A power plant has to produce either base load or peaking electricity on demand to be useful. We have the magic of hydro electricity. It combines a very high ramp rate, and also capable of maintaining base load electricity.  Wind and solar at first seem terrible. They only work when the wind is blowing or when the sun is shining. So they cannot provide either base load or peaking electricity, right? Fortunately, this is not correct. Due to complexities we will discuss in later posts, wind and solar can be installed and paired with each other and with other tech to produce somewhat reliable base load electricity or peak electricity.

One example? When does electricity demand peak in the summer?

If you said when it gets hot and air conditioners work harder and draw more electricity, you are onto something. And it gets hot when the sun shines. Put some solar panels on your roof, and you see your solar panel electricity production rise coinciding with your need for more electricity for house cooling.

Every power plant type has important considerations for peak load vs. base load. As we look at each in turn, it will become apparent how important this distinction is.

One last thing before closing. How do power plants figure out when to turn on? In New England, we have a group called ISO New England. It projects electricity demand based upon yearly trends (people consume a ton of electricity over holidays, and at different time periods!) and upon weather forecasts. Each day, every power plant puts in a bid for how many cents per kilowatt hour they need to turn on. In other words, it’s the figurative “price per kwh to get out of bed.” If demand is projected to rise to such a point that the bid for a plant is met, that plant will turn on once the price hits that. This is confusing. Let’s use an example.

We have three power plants in our imaginary tiny country. Since I keep bringing up this country, I am going to call is JasonLand (for now). JasonLand currently has a coal fired plant, a nuclear plant, and a natural gas plant designed for peaking. The nuclear plant cannot shut down. It will literally bid -$0.50/kwh to  ensure that no matter how low the price is, it will produce electricity. Our coal-fired power plant is baseload, but will shut down on days when it is not needed. It will bid $0.07/kwh. As soon as the price rises above this, it will start up (this is simplified, starting a coal power plant takes a long time). Our peaking gas plant will bid in at $0.11/kwh. Once people get home and need more power, or when it is a really hot day, our peaking gas plant will spin up its turbines rapidly.

So how do these bids work? How much does each plant get paid? As demand rises, price rises, and the power plant earns more for every kwh. Our nuclear power plant will make a small amount in the middle of the night, and make more during the daytime. I’ll leave you to ponder why a power plant would choose to not run until a certain payment threshold is hit.

Because I can’t help myself, let’s close with a tiny bit of math. A realistic price for energy in New England is about $0.15/kwh. To make it easy, let’s convert to $150,000/gwh*. A nuclear plant is about 1gw. It will produce 24 gwh of electricity in a day. That is $3,600,000 in revenue per day. Every week it earns nearly $25 million. I hope at this point any regular reader is beginning to get a sense of how staggering numbers associated with energy use are.

Thanks for reading again!

Jason Munster

*Correction: original post was a factor of 10 short.