How Does Nuclear Energy Work?

In its most basic form, nuclear energy is energy that originates from within the nucleus (core) of an atom. The powerful energy that the atom contains is what holds its dense nucleus together.

Nuclear energy is used to produce electricity that powers our homes and buildings. An estimated 15 percent of the world’s electricity comes from nuclear power. Some nations, such as Lithuania, France, and Slovakia obtain nearly all of their electricity from this energy source [1].

Dark events in the history of nuclear power

Energy generation through nuclear power is a topic with some emotive connotations, not least because of the tragic events associated with the use of the nuclear bomb in Japan during the Second World War. Since then, the use of nuclear energy has also been associated with tragic accidents in Chernobyl, Ukraine, Three Mile Island in Pennsylvania, U.S. and Fukushima, Japan.

In Chernobyl, the radiation released into the environment killed over 50 people, required mass evacuations of thousands of people and caused hundreds of cancer cases. The partial-core meltdown at Three Mile Island did not cause any injuries as very little radiation was released into the environment, but the plant must have been closed, costing the operating company and its investors a lot of money.

In 2011, following a massive black-out caused by a Tsunami in Fukushima, three nuclear reactors lost cooling and the heat from the radioactive decay melted all three cores [2]. In addition to the loss of property, evacuations and many deaths considered “disaster-related”, Greenpeace commissioned a report that argues that this nuclear accident will impact forests, rivers and estuaries for hundreds of years.

Attractive features of nuclear power

Despite the tragic deaths and negative consequences of accidents, nuclear power is considered one of the few energy sources at our disposal that combines three very attractive features:

• Steady stream of cheap energy for the long time.
  One gram of uranium produces the same amount of energy as more than 1.5 tons of coal [3]. So, once a country has invested in the construction of a nuclear power plant, it will keep on generating electricity for at least 40 years at a very low cost.

  According to the MIT Energy Initiative, one kilowatt hour of power from nuclear power plant costs less than two cents [4].

• Energy security if the infrastructure is in place.
  Unlike coal or oil, which come only from a few locations in the world, uranium is found in many diverse locations – diverse both from the geographical and political point of view. This grants easier access of countries to uranium deposits.

  Considering high efficiency of uranium as a fuel, it is also easier to stockpile uranium fuel for many years ahead, which will cover country’s electricity demand for longer periods of time. For comparison, the amount of coal and natural gas needed in one year is so large that majority of countries cannot store more than just a few months’ supply [5].

• A drastically lower level of greenhouse emissions.
  Professor Manfred Lenzen estimates in his research that nuclear energy releases throughout its lifecycle between 10 to 130 grams of carbon dioxide per kilowatt hour of generated power. Similar amount is released by one of the lowest emitters – the wind energy.

  Coal industry, on the other hand, emits between 880 to 1,050 grams per kilowatt hour.

These points might sound wonderful, but like anything in life, our use of nuclear energy is not all roses and fairy dust. Nuclear power plants can produce energy 24/7, but to generate electricity in the first place, the plants need to create a nuclear reaction.

The nuclear energy production process

While the production of nuclear energy may sound like a very complicated process, it is produced through the following basic steps:

• Nuclear energy production takes place within a nuclear reactor or power plant, where electricity takes place in a controlled environment. Within this reactor, atoms of uranium or some other fuel (such as plutonium) are split through a process called nuclear fission.
  
  These split atoms release tiny particles that then cause other atoms of uranium to split in a chain reaction [1]. Such chain reactions produce large amounts of heat through kinetic energy [6].

• The heat created through this process warms a cooling agent that produces steam. Water is typically used for this process, but liquid metal or molten salt may be used instead.

• The steam turns a turbine (or wheels that are turned by a flowing current).

• The turbines power generators or engines that produce electricity [1].

The nuclear energy production process is ultimately not that much different from the processes that occur in other types of power plants. The primary difference between different types of power plants is how the heat is generated.

In a nuclear plant, fission is used to produce the heat that produces steam, turns the turbines, which then run the electricity generators [7]. Fossil fuel plants burn coal, oil or natural gas to generate the heat needed to turn the turbines and then generate electricity [6].

Different types of nuclear power reactors

There are two types of nuclear power reactors: Pressurized Water Reactors (PWRs) and Boiling Water Reactors (BWRs).

Pressurized Water Reactors
PWRs keep the cooling water under sufficient pressure where the water is allowed to turn into steam but never to boil. This steam turns the turbine(s) to power the electricity generator.

Boiling Water Reactors
The water from the reactor and the water that is turned into steam are always kept in separate systems. BWRs allow the heated water to boil and turn to steam, which turns the turbines and power the electricity generator [7].

In both of these types of reactors, the steam is allowed to condense back into water and then it is reused for the same process [6].

Commonly used nuclear fuel

Uranium is the fuel that is most commonly used during the production of nuclear energy. This is because uranium is easy to split apart during the fission process and it can be found in rocks throughout the world.

However, U-235, the type of uranium required for the production of nuclear energy, makes up less than one percent of the existing uranium on Earth [1].

The average nuclear reactor needs approximately 59,000 metric tons (65,000 tons) of U-235 uranium each year. Through the complex re-enrichment and recycling processes, some uranium and plutonium spent nuclear fuel can be reused, which reduces the need for more mining, extracting, and processing [1].

At the end of the nuclear energy production process, radioactive waste is produced. An object is considered to be radioactive when its atomic nuclei are unstable.

Such radioactive materials can be very toxic and result in pollution to the environment and in health problems such as cancers and blood diseases. Therefore, radioactive wastes require proper disposal in an environmentally-sound manner.

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