Climate scientists have assessed that all coal-fired power plants should be phased out by 2030 in the Organization for Economic Co-operation and Development ( OECD ) countries and by 2050 in the rest of the world.
The logical question is, if climate scientists don’t want us to use fossil fuels, which energy source should serve as the basis for electricity generation?
Although renewable energy is the go-to green energy solution, due to its unreliable nature—wind is not always blowing, the sun is not always shining, etc.—it likely cannot meet the requirements for the main electrical energy source. In this article, let’s discuss nuclear energy as a best possible alternative to fossil fuels, despite its bad reputation in the environmental and human aspects. We’ll also review the various nuclear energy technologies and examine the economics of nuclear sources.
In recent years, one of the world’s loudest discussions is how to moderate the impacts of human activities on the environment—the energy as the most dominant factor affecting the environment. Consequently, the term “greenness of energy supply” has received the most attention in the effort to reduce environmental impacts.
What Does “Green” Mean?
The term “green” should be understood first and consistently applied for all energy solutions. The green energy source has no strict definition, but the widely accepted definition is an energy source with a low environmental impact—such as air pollution, waste generation, etc.—and low greenhouse gases emissions (GHGs).
Nuclear power, just like the renewable sources of energy, does not produce GHGs during power generation. However, some pre-production processes, such as mining, extraction and enrichment of uranium, produce some GHGs that are still much lower when compared to fossil fuels. Solar and wind power require substantive construction materials that need to be mined, extracted and processed. Additionally, wind turbines use rare and limited supply materials, and manufacturing of solar photovoltaics involves highly toxic materials. This full-energy generation process should be considered when evaluating total GHGs. In conclusion, all energy sources generate some GHGs.
The energy sources that use coal have higher emissions than any other energy source. Natural gas has the lowest emissions compared to other fossil fuels, but it still produces significant emissions. When the entire energy production process is considered, nuclear plants are ranking among the lowest emitters, right next to wind and solar power plants. These plants do not produce some of the other emissions associated with fossil fuels gases, such as methane, sulfur or nitrous oxides, organic compounds or toxic heavy metals.
Public Opinion on Nuclear Energy
Generally, the public perceptions of nuclear energy are negative. Nuclear waste is the most prominent disadvantage and the main reason why nuclear power “green” credentials are questionable. The nuclear waste has a quite long life cycle and remains radioactive for thousands of years. It is stored in temporary waste repositories, above-ground facilities to ensure that the waste remains sequestered from the environment.
It is important to mention that only nuclear power generation, unlike all other thermal electricity generation forms, fully regulates all waste preventing pollution. Although, all toxic waste, from all sources, should be managed safely. One must bear in mind that nuclear plant is able to produce a huge amount of energy from a very small amount of fuel, ultimately producing a relatively small amount of waste.
Alternative waste management strategies have already been commercially used. Reprocessing used fuel combined with deep geological disposal is used by France, the United Kingdom and Japan. Uranium and plutonium are separated from other nuclides with 99.7-99.9 percent efficiency. Reprocessed uranium is recycled in light water reactors, reducing the need for uranium mining. An alternative to this method is advanced reprocessing, which involves separating the uranium and plutonium, as well as neptunium, americium and curium.
Nuclear waste management is a hot topic among researchers. The European Center for Nuclear Research (CERN) has demonstrated a clean and safe energy production process by burning the nuclear waste in the thorium reactors. The demonstration proved that long-term nuclear waste, more than a 240,000-year life span, can become short term, less than a 500-year life span.
Another nuclear energy disadvantage are the hazards caused by human error and natural disasters. The Chernobyl disaster in 1986 and a massive tsunami disaster at a power plant in Fukushima in 2011 are the two most obvious examples.
However, the main reasons why nuclear power is still not the main energy source in the world is its high capital costs, complex construction and high financial risks.
The Economics of Nuclear Plants
The generally accepted opinion about nuclear power is that building extraordinarily complicated plants and keeping them safe is extremely expensive. Nuclear power stations are huge construction projects. For example, the overall capital costs of Hinkley Point C nuclear power plant are assumed to be EUR€43 billion with an expected operational lifetime of 60 years.
Nuclear plants are technically complex and must satisfy strict regulation and design requirements. They have steep capital costs—preparation, manufacturing, construction, commissioning, etc.—but competitive operating costs. The capital costs account for at least 60 percent of the nuclear power levelized cost of electricity. The existing nuclear plants operate well with a high degree of predictability, thus the operating costs are usually competitive with a low risk of higher operating cost inflation. Although the uranium price can be unpredictable, its significance on the electricity costs are not substantial since it is only a small part of the total operating cost, approximately 14 percent. Figure 3 illustrates the cost of electricity production by different fuel types. The nuclear energy production cost is competitive to the coal energy and lower than the gas energy.
The greatest advantage of nuclear plants is their ability to generate a colossal amount of energy per reactor. The already mentioned Hinkley Point C nuclear power with two units has an electrical capacity of around 3260 MW, producing 26 TWh per year. It is also an excellent example of how much electricity could be generated by renewable sources, see Figure 4. This figure illustrates that due to the nuclear plant high capacity, it is cost-competitive with renewable energy sources. The renewable energy sources have quite a low capacity per unit. Consequently, numerous units are required to generate the same energy amount as the nuclear plants—capacity of small hydro is max 15 MW, wind onshore 5 MW, etc. By simple calculation, one can demonstrate how many renewable power plants are required to replace one nuclear power plant: 652 wind plants or 217 small hydro plants.
Making Nuclear Energy Cost-efficient
- Nuclear power capital costs could be reduced by:
- Replicating several reactors of the same design
- Standardizing the reactor design and construction in series
- Increasing unit capacity
- Simplifying the designs and incorporating passive safety systems
- Optimizing the safety and design requirements, and starting electricity generation (revenues) at the earliest date
- Manufacturing more reactors components at the factory rather than constructing them on-site
Nuclear experts are deliberating small modular reactors with simplified designs and passive safety systems, which should reduce the level of active safety systems and strict regulations, as well as operating and maintenance costs. Due to their smaller size many safety regulations for heat dissipation are redundant. Those small- and simplified-modular reactors can be built in a factory and transported as completed modules for installation in a plant. This could potentially improve construction efficiency and reduce capital costs.
The nuclear power operation costs could be reduced by:
- Lowering the uranium price (new mine investments)
- Cutting fuel service costs due to technological progress (higher burn-up fuel) or innovations (used fuel management)
- Reducing operation and maintenance cost with optimal regulatory requirements
Capacity Factor
The capacity factor is a major parameter when discussing the electricity generation efficiency. It is the ratio between the actual electricity production and maximum possible electricity output of a power plant over a period of time. A power plant output varies and depends on maintenance issues, weather conditions (e.g. wind and sun availability), fuel costs, etc.
Renewable power generation has a significantly lower capacity factor than baseload power plants, such as nuclear, coal or natural gas, due to the variability of the wind and sun. The baseload power plants—which use fuel sources such as nuclear, coal, natural gas or hydro—can operate continuously, unlike variable resources such as the wind and solar facilities. The figure below illustrates the capacity factors for utility-scale generators from 2018.
Nuclear plants require less maintenance and can operate for longer periods of time before refueling. Hence, the nuclear power generation has 1.5-2 times higher capacity factor than natural gas and coal plants, and 2.5-3.5 times wind and solar plants. In other words, replacing one nuclear plant with 1 GW electricity generation would require three-to-four renewable plants each of 1 GW size.
Commonly Used Nuclear Reactors
Nuclear power plants generate electrical energy by using nuclear fission in which the atoms are split to form smaller atoms that release heat energy. The process heats up water and produces steam used to spin turbines that generate electricity.
Generally, nuclear technology is presented through four generations. Each generation is more advanced than the previous one in terms of performance, costs and safety. Nowadays, the generation II reactors are commonly used while generation IV is currently being researched for commercial applications.
The commonly used reactor types in installed nuclear plants are the Pressurized Water Reactors (PWRs), Boiling Water Reactor (BWRs) and Pressurized Heavy Water Reactor (PHWRs).
PWR type is the most commonly used type of nuclear reactor, around 60 percent of all reactors in the world, which uses U235 of a typically 3-4.5 percent enrichment. This reactor type uses light ordinary water for neutron moderation, which slows down the speed of the neutrons, enabling the fission to take place with U235 at a low enrichment. The water is also used to cool down the reactor. The design includes two separated circuits: primary, water is under high pressure, and secondary, water is at lower pressure. The reactor cooling water and steam for power generation are separate, thus the released steam is radioactive-free.
BWR type uses U235 of a typically 2-4 percent enrichment and accounts for approximately 20 percent of all nuclear reactors. Just like PWR type, it uses light water for neutron moderation and cooling down the reactor. BWR design uses only a single circuit with water under lower pressure. In case a necessary venting occurs, any steam released could contain radioactive products.
PHWRs type, known as CANDU, is mostly used in Canada and India. It represents around 10 percent of all nuclear reactors. This type uses uranium without enrichment at its natural level of around 0.7 percent U235 concentration. Heavy water is used for neutron moderation and cooling down the reactor. Heavy water is made by replacing the ordinary hydrogen atoms, which have only one proton in the nucleus, with heavier hydrogen atoms, which have one proton and one neutron in the nucleus, providing a more efficient fission process. The heavy water flows through pressure tubes filled with uranium. It takes away the reactor heat and transports it to an adjoining circuit to raise steam and drive a turbine-generator. This design allows reactor refueling during operation by isolating individual pressure tubes from the cooling circuit.
The Generation IV reactors are still in the research and development stage. Their first implementation is expected after 2025. Generation IV has six promising new reactor types:
- The Gas-Cooled Fast Reactor (GFR)
- Very-High-Temperature Reactor (VHTR)
- Supercritical-Water-Cooled Reactor (SCWR)
- Sodium-Cooled Fast Reactor (SFR)
- Lead-Cooled Fast Reactor (LFR)
- Molten Salt Reactor (MSR)
The long-term potential of these projects is enormous. The new reactor types should provide numerous benefits, such as:
- Using uranium in a more efficient way, such as using depleted uranium or already “spent” fuel
- Destroying the nuclear waste via transmutation
- Generating hydrogen for transportation and other purposes
- Increasing safety and providing simpler operation
- Providing cost efficiency and decreasing financial risks
To elaborate on the efficiency and power of the Generation IV reactors, one molten-salt reactor designed to consume a ton of uranium per year could supply sufficient hydrogen to fuel 3 million passenger vehicles. The nuclear waste generated in a year would occupy half the volume of a typical refrigerator, and the radioactivity of the waste would diminish to background levels in about 500 years.
Conclusion
Nowadays, nuclear power plants operate more efficiently than in the past, providing low GHGs and secure energy with relatively low operating costs. They can generate a huge amount of energy per reactor providing steady electricity 24/7. Because of the world’s requirement for new generating capacity and green energy sources, nuclear plants have good growth prospects. Just like the renewable energy, nuclear energy sources need government support and subsidies. The governments could implement additional taxes policies for fossil fuel plants and allocate them to green energy sources, such as nuclear power plants. This would make nuclear plants more feasible with the economic benefits to potential investors. The government should also keep in mind that a nuclear plant reduces the energy import dependence of the country. One example of the nuclear energy economic viability is France, which has a longstanding nuclear-based electricity supply system that provides a low electricity price, categorized among the lowest worldwide.
While renewables, carbon capture and various political strategies are more commonly discussed as solutions to climate change, nuclear fission may be the most practical solution based on real engineering.