Nuclear

Nuclear energy has been a hot-button issue for a very long time, both domestically and internationally. It provides a significant portion of the global electricity supply, as you will see in the image below.

Figure 3.12: As you can see, nuclear provides around 11% of global electricity, second only to hydroelectric in terms of carbon-free electricity. Note also that coal is a source of about 39% globally, but around 33% domestically. (Text version of Figure 3.12 [1]. A new window will open.)

Credit: The Shift Project Data Portal [2], CC SA-BY 3.0

Supply

Nuclear energy is non-renewable. Uranium is by far the most-used nuclear fuel. As with other non-renewable fuels, all of the uranium that is on earth now is all that we will ever have, and estimates can be made of the remaining recoverable resources. At current rates of consumption, we will not run out of uranium any time soon. But this depends very highly on a number of variables, including keeping consumption at current levels, technology not advancing, estimates of reserves changing, and so forth.

The World Nuclear Association (WNA), an industry association, provides a very thorough explanation of possible complicating factors [3], but they state that at current rates of consumption, the world has enough reserves to last about 90 years. The Nuclear Energy Agency (NEA [4]), like the WNA,  [4]is effectively an industry group and has a wealth of expertise at its disposal. They indicate that as of 2009, the world had about a 100 year supply of uranium. So it appears that as long as the rate of use does not increase there is a little less than 100 years of nuclear fuel supplies left.

Feasibility

According to the World Nuclear Association, there are 454 operable reactors worldwide with a further 54 under construction [5]. The technology is well known by now, and despite the extreme danger posed by nuclear meltdowns, there have been very few major incidents. You are probably familiar with the Fukushima Daichi meltdown that happened in 2011, and perhaps heard of Chernobyl in Ukraine in 1986 (still the worst nuclear disaster to date), and maybe even Three Mile Island in the U.S. in 1978. Here is a partial list of nuclear accidents [6] in history from the Union of Concerned Scientists (UCS). But putting aside this risk at the moment, nuclear energy has shown itself to be a viable source of electricity, and likely will continue to be used for the foreseeable future. Among other things, nuclear power plants generally have a useful lifetime of around 40-60 years, so we are "locked in" until mid-century at least. 

Sustainability Issues

Nuclear energy is a mixed bag in terms of the question of sustainability. You may recall that nuclear is considered a carbon-free source, and since it is a proven and reliable source, it is seen by many as a good option. Note that despite being considered "carbon-free," nuclear energy results in some lifecycle emissions because of the materials used in mining, building the power plant, and so forth. (Lifecycle emissions are all the emissions generated by all processes required to make an energy source, including things like mining of materials, manufacturing of equipment, and operating equipment.) But according to the National Renewable Energy Laboratory (NREL) [7] it has approximately the same lifecycle emissions as some renewable energy sources.

Figure 3.13: Lifecycle emissions of select energy sources. This chart indicates the average grams of CO₂ emitted per kWh of electricity over the life of each energy source. As you can see, solar photovoltaics, concentrated solar, wind, and nuclear have near-zero emissions (less than 50 g/kWh), while coal averages close to 1,000 g/kWh, which is over 20 times more emissions than most of the other sources in this chart.

Credit: U.S. National Renewable Energy Laboratory [7], public domain

Some other sustainability considerations include:

• Nuclear energy is a very reliable source of electricity, and power plants can operate at near full capacity consistently.
• However, nuclear energy is very expensive in terms of direct costs.
• Since they are so expensive, there is an incentive to keep a plant online for as long as possible to recoup costs, thus people are effectively "locked in" once a plant is built.
• The waste from nuclear reactors can remain dangerous for thousands of years [8], which can result in large externalities.
• There is, of course, the risk of another disaster which, however rare the possibility, could be catastrophic.
• There are also some issues with the equity impacts of uranium, particularly in terms of mining [9]. There is not an easy answer here, as there are reasonable and strong pros and cons.
• Regarding the cost of nuclear: The high up-front cost makes nuclear power one of the most expensive types of electricity available. For a technical discussion of this, feel free to read through this description of the levelized cost of electricity [10] from the EIA, which indicates that over the lifetime of the energy source, nuclear is more expensive than geothermal, onshore wind, solar, hydroelectric, and most types of natural gas plants.

Overall, nuclear is reliable and almost carbon-free but is expensive and non-renewable. Also, because power plants are so expensive to build, once they are built they are generally used for as long as possible, as long as they are still economic. When accidents happen, they can be catastrophic, but they are extremely rare. However, the waste product from nuclear power plants is dangerous for thousands of years, and right now we have no way of safely disposing of it - it is kept in storage, usually at the power plants themselves.