|
|
►Nuclear Energy:
Nuclear power is strong is Europe
with about forty-two percent of their energy produced by fission.
Nuclear generation provides about 17% of world electricity, avoiding the
emission of up to 2.3 billion tonnes of carbon dioxide annually. France
produces 76% and Lithuania produces 85.6% of its energy by nuclear
fission In the United States, people are antinuclear because of 3 Mile
Island in 1979 and Chernobyl in 1986. However, many experts say that it
is a safe, clean,
and reliable source of energy. Nuclear Fission produces no greenhouse
gases, but does produce highly toxic radioactive wastes.
Heat is produced in a nuclear reactor when neutrons strike Uranium atoms
causing them to fission in a continuous chain reaction. Control
elements, which are made of materials that absorb neutrons, are placed
among the fuel assemblies. When the control elements, or control rods as
they are often called, are pulled out of the core, more neutrons are
available and the chain reaction speeds up, producing more heat. When
they are inserted into the core, more neutrons are absorbed, and the
chain reaction slows or stops, reducing the heat.
Most commercial nuclear reactors use ordinary water to remove the heat
created by the fission process. These are called light water reactors.
The water also serves to slow down, or "moderate" the neutrons. In this
type of reactor, the chain reaction will not occur without the water to
serve as a moderator. In the United States, two different light-water
reactor designs are currently in 10
use, the Pressurized Water Reactor (PWR) and the Boiling Water Reactor (BWR).
In a PWR, the heat is removed from
the reactor by water flowing in a closed pressurized loop.
The heat is transferred to a second water loop through a heat exchanger.
The second loop is kept at a lower pressure, allowing the water to boil
and create steam, which is used to turn the turbine generator and
produce electricity.
Afterward, the steam is condensed into water and returned to the heat
exchanger.
|
Nuclear Energy -
Page 1/2