Transcript Nuclear Reactors - Health Physics Society

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 which 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 concrete pool lined with
stainless steel to cool off.
Dry Cask Storage
•
At some plants, the pools have
filled up.
•
Some of the fuel that has cooled
off, is moved into big concrete
casks.
•
Eventually, the fuel will be sent to
a federal government facility for
permanent disposal deep under
ground.
•
Spent fuel from San Onofre Unit 1
will soon be stored in this way.
Transportation Safey
• A 120-ton locomotive, speeding at 80
miles an hour, crashed broadside into a
container on a flatbed.
• This photo was taken immediately after
impact.
• The impact demolished the train, but
hardly dented the container.
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. This makes it possible to
put a repository 1,000 feet underground
and still be 800 feet above the water table.
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.
•
The arid mountain ridge is 100 miles
northwest of Las Vegas in the Mojave
Desert.
•
$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, protected by
corrosion-resistant containers.