Nuclear Reactors

Health Physics Society - Power Reactor Section

Radiation Science Education

Location of Operating Nuclear Reactors

Think of a Tea Kettle

The fission process creates heat that produces steam in a secondary water system. The steam turns a turbine-generator which produces electricity.

HOW A NUCLEAR REACTOR WORKS

Three Barriers to Contain Radiation

Defense In Depth

• 48” concrete containment building

• 35” concrete shield

• 8” steel reactor vessel

• solid nuclear fuel inside steel tubes

How Used Fuel is Removed

What Happens to Used Fuel?

• Nuclear reactors split atoms of uranium which creates heat. This process is called fission.

• Uranium in a nuclear reactor comes in the form of ceramic pellets.

• Only one of the uranium isotopes fission, U-235. New fuel contains about 5% U-235, the rest is U-238.

• When most of the U-235 has split, the used-up or “spent fuel” is stored in a large pool to cool off.

Dry Cask Storage

• After the fuel has “cooled”, it is moved into concrete casks.

• Eventually, the fuel will be sent to Yucca Mountain for permanent disposal deep under ground.

Transportation Safety

• A 120-ton locomotive, speeding at 80 miles an hour, crashed broadside into a container on a flatbed.

• The impact demolished the train, but hardly dented the container.

Transportation Container

• Used nuclear fuel: ceramic pellets encased in steel tubes.

• Used nuclear fuel cannot explode.

• Used nuclear fuel does not burn.

Yucca Mountain

• Volcanic eruptions created Yucca Mountain about 10 million years ago.

• Over the ages, layers of volcanic ash compressed and consolidated into a hard rock called tuff.

• There is very little rainfall, most of which quickly runs off the surface or evaporates.

• The water table under Yucca Mountain is extremely deep.

Permanent Disposal

• Yucca Mountain is federally owned land that borders the Nevada Test Site.

• More than 900 atomic weapon blasts have been conducted at the Nevada Test Site, mostly underground.

• $2 billion dollars have been spent on scientific investigation of the geology and hydrology of the site.

• Spent fuel will be stored 1000 feet below under ground, 800 feet above the water-table, protected by corrosion-resistant containers.