Updated: Jan 28
By Hamilton Steimer
Source: Dan Meyers on Unsplash
If you’ve been paying attention to the news, you might have heard that an energy revolution is underway around the world. Throughout the United States, renewable energy generation has grown monumentally, coal power plants are being shut down, and society is becoming increasingly electric. Although much of the attention and fanfare has been on renewable energy and clean energy technologies, we cannot approach the energy transition without addressing nuclear power. Recent developments in policy and technology regarding this arguably “clean” energy source will have significant ramifications on the climate and our energy system.
This blog post will talk about recent news regarding nuclear power and the basics of how nuclear power works. There will be a secondary blog that will discuss the pros and cons of nuclear power and get more into the nuances of nuclear energy.
New developments in nuclear power
Nuclear power has been around for decades, churning out reliable, emission-free electricity to help meet baseload energy demand in countries around the world. However, there have recently been big shifts in nuclear energy policy and new technological progress that will impact the global climate.
One of them is the latest announcement by Bill Gates’ company TerraPower that it will build its first demonstration nuclear reactor in Kemmerer, Wyoming. The town has historically been dominated by the coal industry, so the project intends to represent how clean energy can ensure a equitable energy transition. Founded in 2008, TerraPower aims to construct a 345 MW Natrium reactor, which it claims will be safer and more affordable. The company will be partnering with the Japan Atomic Energy Agency and Mitsubishi Heavy Industries Ltd to build the plant, and half of the $4 billion price tag will be paid for by the US government.
TerraPower claims its design will be safer, simpler to construct, and much more affordable than traditional nuclear reactor designs. However, others have made similar claims. Currently, the only nuclear reactors actively under construction in the United States are the two nuclear power units at Plant Vogtle in Waynesboro, Georgia. Originally billed as an “evolutionary improvement” over existing reactors, these new reactors have been hampered by years of delays and rising costs. They were first cited to cost $14 billion, with the first reactor to go online in 2016, but the total costs are now believed to be over $26 billion. After another recent delay, the first unit won’t open until sometime in 2022.
While it seems there is potential new life in the nuclear industry in the US and other countries like China and France, other countries, most noticeably Germany, are reconsidering their relationship with nuclear energy and are closing down their nuclear power plants. Just the other week, Germany shut down three of its six remaining active nuclear power plants, with the other plants to go offline by the end of 2022. This has come after years of political debate and unrest in Germany regarding nuclear power. Previously a supporter of nuclear energy, then-Chancellor Merkel reversed her position after the Fukushima disaster in Japan, and the government decided to begin a phaseout of its nuclear power plants that will be completed by the end of the year. Germany has thrown its full support behind solar and wind energy, but its transition to all renewables has produced mixed results, as the country has had to rely more on coal and lignite to meet energy demand when renewables are offline.
An Intro to Nuclear Power
How does it work?
The main purpose of a nuclear reactor is to safely contain and control the nuclear fission process so that the resulting energy can be harnessed in a way to generate clean electricity. Nuclear fission usually involves Uranium-235, which is capable of sustaining a nuclear fission chain reaction. The nuclear fuel needs to have a higher concentration of the U-235 isotope than what is found naturally, so scientists concentrate (or enrich) it to 3 to 5% to be used in the nuclear reactor. Nuclear weapons need the fuel to be enriched to about 90%
The fuel is processed into pellets and stacked together in sealed metal tubes called fuel rods which are clustered together into fuel assemblies and placed within the reactor’s core. The US utilizes light water reactors, meaning normal water is used as booth a coolant and neutron moderator to sustain the chain reaction. Control rods can be inserted into the core to reduce the reaction rate or be removed to accelerate it.
The nuclear fission process generates a lot of heat, which turns water into steam that turns a turbine and generates clean electricity. Nuclear power plants have a capacity factor close to 90%, meaning they are producing electricity almost all the time, except during maintenance and when changing fuel rods. This means that nuclear power plants can provide reliable, clean electricity for the grid!
Nuclear fuel can be used to generate electricity for about 5 years, until it is no longer efficient to use to create electricity. The spent fuel is classified as high-level radioactive waste and must be safely removed and stored to prevent harm to people and the planet. Thankfully, nuclear plants produce very low volumes of radioactive waste. The waste production is so small in fact, that all of the waste produced since the 1950s would only cover a football field to a height of 10 yards, about the same amount of waste coal plants produce every hour.
Unfortunately, the problem with nuclear waste is that it will practically last forever, as the radioactive isotopes have extremely long half-lifes, or time for them to decay by half. While some may decay very rapidly, others will take millenia, such as Plutoniom-239, which has a half-life of 24,000 years. During this time, the waste remains extremely harmful, and it will need to be stored properly to prevent an ecological disaster.
Spent fuel rods are initially cooled and stored in large pools of water, which are reinforced with several feet of concrete and steel. Then after 5-10 years, they are transferred into steel canisters surrounded by concrete called “dry casks.” These casks are designed for long-term storage, and the waste will stay there until a permanent disposal location is identified.
At the moment, there are no permanent disposal facilities for high-level waste in the United States. You may have heard of Yucca Mountain, Nevada which was designated as the permanent storage site for the country’s nuclear waste in the 1980s, but the Department of Energy cancelled the project in 2010.
For more detailed information on nuclear waste, click here.
In the United States, there are two types of light-water reactors: pressurized water reactor and boiling water reactor.
Most of the US-based reactors are pressurized-water reactors. These reactors pump water into the core under higher pressure to prevent the water from boiling. That water is heated up during the fission process, and then pumped through tubes in a heat exchanger, where it heats up water within a separate source to produce steam. The steam is then funneled through a turbine to turn it and generate electricity. The water exposed to the core cycles back to the reactor to be reheated and being the process anew.
Source: US Department of Energy
Boiling water reactors are somewhat similar to pressurized water reactors. Without the high pressure, the water boils and produces steam right within the reactor. The steam is fed directly to the turbine to produce electricity. Afterward, the unused steam is condensed back into water and reused through the system.
Source: US Department of Energy
There are new types of reactors that are expected to be introduced into the market in the coming decades. The designs of these reactors are intended to minimize the volume and management period of radioactive waste, reduce the capital costs of the power plant, and improve the safety and resiliency of the power plant.
Gas-cooled fast reactor
Very high temperature reactor
Super critical water-cooled reactor
Sodium-cooled fast reactor
Lead-cooled fast reactor
TerraPower’s Natrium reactor is a 345 MW sodium fast reactor with molten salt energy storage. The next generation power plant will use liquid sodium as a cooling agent instead of water, which TerraPower claims will promote safety and avoid dangerous build-ups of pressure within the reactor because the sodium can absorb much more heat than water. The design also implements passive cooling, one of the key features missing from Fukushima’s nuclear plant, so the cooling system does not rely on any outside energy source to operate. One of the other key features of this design is that molten salt is heated during the fission process and is stored for later use. When the power plant is connected to the grid, the thermal storage can be utilize to increase the plant’s output to 500 MW of power for more than 5 hours to compensate for drops in power production or renewables’ intermittency. Additionally, the plant should cost much less than a conventional nuclear power plant because of its smaller size and because it does not require the same heavy-duty construction materials since the plant will be operating at lower pressure.
With the plant expected to be built by 2028, we will see it its performance meets TerraPower’s lofty claims in the near future.