Nuclear Reactors, Materials, and Waste Sector

Welcome to another week of Chem-Sect. This week, I will be covering nuclear reactors and everything associated with it and how it is an integral part of our environment.

Overview of this Sector

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From the power reactors that provide electricity to millions of Americans, to the medical isotopes used to treat cancer patients, the Nuclear Sector covers most aspects of America’s civilian nuclear infrastructure. The Nuclear Sector-Specific Agency within the Department of Homeland Security is responsible for coordinating the security and resilience of the Nuclear Sector.

Nuclear Energy

Did you know that nuclear energy is by far America’s largest source of clean, emission-free electricity? Yes. According to the Nuclear Energy Institute (NEI), nuclear energy produces no greenhouse gases or air pollutants. In fact, the nuclear industry has a commitment to the environment which extends to protecting natural wildlife as well as their habitats.

Nuclear reactor and power plants is an industry which aid compliance to the Clean Air Act of 1970. It sets the standards to improve the nation's air quality. Using more nuclear energy gives states additional flexibility in complying with clean-air requirements. However, the potential vulnerability of some nuclear power plants and reactors to premature retirement creates a major threat to the attainment of CO2 reduction goals.

Nuclear Reactor Plants

Courtesy of Tennessee Valley Authority

What exactly is a nuclear reactor? Well, it can be defined as a system which contains and controls continual nuclear chain reactions. These reactors are used for generating electricity, moving extremely enormous, heavy, and dense equipment such as aircraft carriers and submarines. These reactors also produce medical isotopes for the purpose of imaging and to treat cancer as well as a foundation for scientists to conduct research.

The process of creating nuclear energy is quite interesting. First, the fuel to generate nuclear power is made up of heavy atoms which split when they absorb neutrons. Next, these neutrons are then placed into a large reactor tank along with a small neutron source. Once inside, the neutrons begin a chain reaction where each atom that splits, releases more neutrons which cause additional atoms to split. And each time an atom splits, it releases large amounts of energy in the form of heat. This heat is then transported out of the reactor by a liquid coolant (i.e. water). Finally, the coolant heats up to a high degree and then transfers into a turbine to spin the reactor’s generator or drive shaft. All in all, nuclear reactors are just a fancy term for heat sources.

The Five Major Components of a Nuclear Reactor

1. The Reactor Core

The reactor core consists all of the all of the nuclear fuel and generates all of the heat. It comprises a low-enriched uranium of approximately five percent of Uranium-235 (U-235). The core is also comprised of control systems and structural materials containing hundreds of thousands of individual fuel pins. See illustration to the left.

2. The Coolant
The coolant is the material that passes through the core. It transfers heat from the fuel into a turbine which may be water (most common), liquid sodium, helium, or some other type of element.

3. The Turbine Engine
The turbine transfers heat from the coolant forming electricity which is very similar to fossil-fuel plant.

4. The Containment Shell

Courtesy of davidjohnstewart.com

The containment is the structure that separates the reactor from the environment. These are usually dome-shaped structures that are made of high-density, steel-reinforced concrete. See figure to the right.

5. The Cooling Towers
The cooling towers are a necessity required by nuclear plants to dump excess heat that otherwise cannot be converted into energy due to laws of thermodynamics (the relationship between heat and energy). These are the hyperbolic icons of nuclear energy and emit only clean water vapor.


Reactor System Illustration


Courtesy of the NRC

The image on the left shows a nuclear reactor heating up water and spinning a generator to produce electricity. It captures the essence of the system well. The water coming into the condenser and then going right back out would be water from a river, lake, or ocean. It goes out the cooling towers. As you can see, this water does not go near the radioactivity, which is in the reactor vessel.


Common Questions

Here are just a few of the most commonly asked questions about nuclear energy…

Q. How does nuclear energy compare to other power sources?
A. A single uranium fuel pellet the size of a pencil eraser contains the same amount of energy as 17,000 cubic feet of natural gas, 1,780 pounds of coal or 149 gallons of oil.

Q. Does nuclear energy produce greenhouse gases?
A. There are no emissions of carbon dioxide, nitrogen oxides and sulfur dioxide during the production of electricity at nuclear energy facilities. Nuclear energy is the only clean-air source of energy that produces electricity 24 hours a day, every day.

Q. Is nuclear energy considered a renewable energy source?
A. A renewable energy source uses an essentially limitless supply of fuel, whether wind, the sun or water. Nuclear energy is often called a sustainable energy source, because there is enough uranium in the world to fuel reactors for 100 years or more.

 

Are you interested in more? Then check out this clip:
 

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References:

DHS. (2017, July 11). Nuclear Reactors, Materials, and Waste Sector Resources. Retrieved from

        Homeland Security: https://www.dhs.gov/nuclear-sector-resources

Duke Energy. (2016). Nuclear Energy in 60 Seconds: Environmental Benefits. Retrieved from

        YouTube: https://youtu.be/6PO7uHCahFY

NEI. (2017). FAQ About Nuclear Energy. Retrieved from Nuclear Energy Institute:

         https://www.nei.org/Knowledge-Center/FAQ-About-Nuclear-Energy

Touran, N. (2016). What is a Nuclear Reactor? Retrieved from What Is Nuclear:

         https://whatisnuclear.com/articles/nucreactor.html