How does a nuclear power plant work?

Як працює атомна електростанція?

Learn how does a nuclear power plant work, what are the different types of nuclear reactors, and understand the basic principles of nuclear power.

At its fundamental essence, nuclear power involves the process of atom splitting to heat water, activate turbines, and produce electrical energy.

Illustration: A neutron bombards a uranium atom, releasing more neutrons and starting a chain reaction / Photo:
Illustration: A neutron bombards a uranium atom, releasing more neutrons and starting a chain reaction / Photo:

During fission, a neutron strikes a uranium atom, releasing more neutrons and starting a chain reaction.

Principles of nuclear energy

Atoms resemble miniature solar systems in structure. The nucleus, located at the atom’s center, is orbited by electrons.

The nucleus is composed of densely packed protons and neutrons. Hydrogen, the lightest element, contains a single proton, while uranium, the heaviest naturally occurring element, has 92 protons.

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Binding the atom’s nucleus is an immensely powerful force, regarded as “nature’s strongest force.” When bombarded by neutrons, the nucleus can undergo fission, splitting into fragments. This phenomenon is harnessed due to the relatively weak atomic force binding large uranium atoms, making them suitable for fission.

Within nuclear power plants, neutrons collide with uranium atoms, initiating their splitting. As this occurs, neutrons are emitted, which then collide with other atoms, setting off a chain reaction. This reaction is moderated by “control rods” designed to absorb neutrons.

Within the core of nuclear reactors, the fission of uranium atoms yields energy that heats water to approximately 520 degrees Fahrenheit. This heated water is subsequently utilized to drive turbines, which, in turn, are connected to generators generating electricity.

Extraction and Processing of Nuclear Fuel

Uranium, though not abundant – constituting only two parts per million in the Earth’s crust – is a rich energy source due to its radioactivity. A kilogram of uranium holds as much energy as three million kilograms of coal.

Radioactive elements naturally decay, losing their radioactivity over time, a period referred to as “half-life.” U-238, the prevalent form of uranium, boasts a half-life of 4.5 billion years.

Uranium is found in various geological formations, including seawater. Yet, for it to serve as fuel, its concentration must exceed one hundred parts per million (0.01 percent) within the host rock.

Uranium mining techniques resemble those of coal mining, involving both open-pit and underground operations. Environmental impacts are comparable, with the added concern that uranium mine tailings possess radioactivity. Groundwater contamination may stem from not only heavy metals in mine waste but also residual traces of radioactive uranium. A significant portion of uranium mining employees engage in post-mining site cleanup.

Uranium exists in two primary forms: U-235 and U-238. While natural uranium is over 99 percent U-238, U-235 is the variant utilized in power generation. U-238 can also be converted into fissionable plutonium.

Following mining, uranium ore undergoes processing to concentrate it into usable fuel. The resulting uranium oxide (U3O8) is shaped into small pellets, organized into rods, and assembled into fuel assemblies destined for the reactor core.

How does a nuclear power plant work: Nuclear Reactors

Two primary reactor types are pressurized water reactors (PWRs) and boiling water reactors (BWRs). In a boiling water reactor, depicted above, water undergoes boiling to produce steam, subsequently driving a turbine for electricity generation.

How does a nuclear power plant work: Pressurized water reactors (PWRs) / Photo:
How does a nuclear power plant work: Pressurized water reactors (PWRs) / Photo:

Pressurized water reactors maintain the core’s water under pressure to prevent boiling. Heat is transferred to external water via a heat exchanger, causing it to boil and generate steam, which powers a turbine. This approach separates the boiling water from the fission process, preventing radioactivity.

Once steam propels the turbine, it cools and condenses back into water. Some plants employ river, lake, or ocean water for cooling, while others rely on cooling towers.

How does a nuclear power plant work: Boiling water reactors (BWR) / Photo:
How does a nuclear power plant work: Boiling water reactors (BWR) / Photo:

Hourglass-shaped cooling towers are a common sight at many nuclear plants. For every unit of electricity produced, about two units of waste heat are released.

Commercial nuclear plants range in size from about 60 megawatts for early-generation plants to over 1,000 megawatts. Numerous plants host multiple reactors.

Certain reactor designs use alternative coolants like heavy water or gases (e.g., helium) for heat removal. Liquid metals or sodium are also employed in some plants, including a now-defunct high-temperature gas-cooled reactor in Colorado.

Nuclear Waste Management

We’ve delved into how does a nuclear power plant work, but what about the management of nuclear waste?

Up until the mid-1970s, there were intentions to reprocess used uranium to create fresh fuel.

However, the fact that reprocessing yields plutonium – a material that can be utilized in nuclear weaponry – along with economic challenges compared to using new uranium fuel, led to the abandonment of these reprocessing plans.

Numerous nations have established sites for nuclear waste disposal.

Concurrently, radioactive waste is stored at the nuclear power plants where it’s generated. Commonly, it’s stored in spent fuel pools, large tanks lined with steel that use electricity to circulate water. When these pools reach capacity, certain fuel rods are shifted to sturdy steel and concrete casks for enhanced safety.

In addition to spent fuel, the plants themselves contain radioactive waste, necessitating disposal after closure. The decommissioning of nuclear power plants can be immediate or postponed for several years to allow radiation levels to decrease. A substantial portion of the plant’s materials fall under the category of “low-level waste,” and they can be stored in less secure locations.

Evolution of Nuclear Energy

The fundamentals of nuclear power were outlined by physicists during the early 20th century. In 1939, German scientists identified nuclear fission, sparking a race with American counterparts to harness its formidable power for weapon creation.

Through the concentrated endeavors of the Manhattan Project, the atomic bomb was developed by 1945 and used to devastate Hiroshima and Nagasaki at the close of World War II.

Post-war, the prospect of “vast atomic power” emerged as a potential energy source.

In the late 1950s, the exploration of nuclear power for commercial electricity generation commenced, beginning in England. The Dresden Nuclear Power Plant in Morris, Illinois, marked the initiation of commercial reactor operations in the United States in 1960. Meanwhile, the Shippingport plant in Pennsylvania was operational in 1957 but remained non-commercial.

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Decline in U.S. Nuclear Energy Popularity

Following financial losses, manufacturers ceased providing turnkey plants. By the 1970s, around 200 plants were constructed, under construction, or planned. Yet, multiple factors converged to terminate the nuclear upsurge.

Firstly, cost overruns unveiled the genuine expense of nuclear power plants. As utilities embarked on constructing plants with distinct designs and minimal technological familiarity, coupled with the “design-as-you-build” approach, immense cost overruns ensued.

Construction spanned years, leaving utilities with substantial investments prior to operational launch.

Secondly, energy prices escalated considerably in the 1970s due to factors like the OPEC oil embargo, coal industry labor disputes, and natural gas shortages. These elevated prices spurred enhanced energy efficiency and diminished demand.

After years of a 7% annual electricity demand growth, the rate dwindled to 2% in the late 1970s. Given the significant scale of nuclear power plants, often exceeding 1000 MW each, reduced demand expansion led to underutilization, exacerbating utility debt.

Thirdly, surging energy prices corresponded to elevated inflation rates and lending rates. Utilities burdened by nuclear plant-related debts encountered amplified interest rates, necessitating electricity price hikes.

State public utility commissions, once indifferent to utility finances amid tariff reductions, turned their attention to utility decisions about power plant investments.

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Fourthly, public utility commissions hesitated to shift all investment costs to ratepayers. In New York, the commission ruled that a quarter of the Shoreham nuclear power plant costs were not “prudent,” leading to a $1.35 billion loss for utility shareholders. Investors grew cautious of substantial, high-risk nuclear power investments.

Fifthly, public opposition to nuclear power surged in the 1970s, with anti-nuclear protests centered on nuclear plants. By influencing siting and licensing decisions, anti-nuclear groups, alongside state and local governments, obstructed or postponed plant construction.

In 1979, the Three Mile Island nuclear plant reactor core meltdown marked the latest issue in a series. Increased scrutiny from the Nuclear Regulatory Commission compelled alterations to plant designs mid-construction.

While proponents blame governmental regulation for the industry’s predicament, the federal government remained a steadfast supporter. It was only after the Three Mile Island incident that regulatory oversight was intensified.

By the 1980s, the nuclear industry faced serious turmoil. No new plant orders emerged after 1978, and orders made since 1973 were canceled. In 1985, Forbes magazine reported that sample construction costs for 35 ongoing plants were six to eight times higher than initial estimates, and construction durations had doubled from six to twelve years.

The magazine labeled nuclear power as “the most monumental managerial debacle in business history.” Ultimately, between 1972 and 1990, more plants were canceled than constructed – 120 in total.


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