Containment building facts for kids

A containment building is a very strong structure built around a nuclear reactor. Its main job is to keep radiation safely inside, even if something goes wrong with the reactor. Think of it as the last protective shield that stops radiation from getting into the environment (the air, water, and land around us).

These buildings come in different sizes and shapes. They are made from strong materials like steel and concrete. The exact type of containment building depends on the kind of reactor, when it was built, and what the power plant needs.

For example, the Chernobyl accident was very serious partly because the Soviet RBMK reactors at that power plant did not have containment buildings. However, the explosion was so powerful that even a containment building might not have stopped all the radiation from escaping.

How Nuclear Reactors Are Protected

Nuclear power plants have many safety features. They are designed with several layers of protection to keep people and the environment safe. This is often called "defense in depth."

Nuclear power reactor defense layers

Here are the main layers of defense for a nuclear reactor:

• First layer: The uranium oxide fuel itself. This material is a solid ceramic, which means it's very stable and doesn't easily release radioactive particles.
• Second layer: The fuel rods. The uranium fuel is sealed inside long, thin tubes made of a special metal called zirconium alloy. These tubes are airtight.
• Third layer: The reactor pressure vessel. This is a very thick steel container that holds the reactor core and the fuel rods. It's designed to withstand high pressure.
• Fourth layer: The containment building. This is the large, strong building that surrounds the entire reactor and its main systems. It's built to be pressure-resistant and airtight.
• Fifth layer: The exclusion zone. This is a special area of land around the power plant where no one is allowed to live. It provides an extra buffer in case of any release.

Images for kids

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  NRC drawing of the containment building from a pressurized water reactor

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  Reactor Unit 3 (right) and Unit 4 (left) of Fukushima Daiichi on 16 March 2011. Three of the reactors overheated, causing meltdowns which released radioactive material out of the containments.

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  If the outward pressure from steam in a limiting accident is the dominant force, containments tend towards a spherical design, whereas if weight of the structure is the dominant force, designs tend towards a can design. Modern designs tend towards a combination.

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  NRC image of the Containment area inside a Containment building.

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  Three Mile Island was an early PWR design by Babcock & Wilcox, and shows a 'can' containment design that is common to all of its generations

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  A more detailed image for the 'can' type containment from the French Brennilis Nuclear Power Plant

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  The twin PWR reactor containments at the Cook Nuclear Plant in Michigan

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  A German plant exhibiting a nearly completely spherical containment design, which is very common for German PWRs; it is a double-containment with an inner steel shell

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  The former German BWR-unit Krümmel; the steel containment is within the reactor building on the right

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  A typical two-unit US-BWR at the Brunswick Nuclear Generating Station; the containments (Mark I) are within the cubical shield buildings too

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  Modern plants have tended towards a design that is not completely cylindrical or spherical, like this containment within the blue painted reactor building of the Clinton Nuclear Generating Station

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  The Bruce B Generating Station, showing a large vacuum building (left) serving 4 separate units that have a BWR-like shield building around them individually

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  Qinshan phase III consists of two CANDU units where the containment system is autonomous for each unit

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  A single unit of the Pickering Nuclear Generating Station, showing a slightly different shape from a typical PWR containment, which is mostly due to the larger footprint required by the CANDU design. The vacuum building can be seen partly obscured on the right.

See also

In Spanish: Edificio de contención para niños