the speed of the neutrons is slowed down through the use of a moderator. Less
than 1% of all natural uranium on Earth is U-235. Uranium that has been
processed to separate out U-235 is known as “enriched” uranium. Nuclear
weapons contain 85% or more of U-235 whereas nuclear power plants contain
about 3%. The half-life (the time taken for the radioactivity to fall to half its
original value) is 700 million years.
U-238
U-238 is the most common (99.3%) isotope of uranium and has a half-life of 4.5
billion years. When hit by a neutron, it eventually decays into Pu-239, which is
used as a fuel in fission reactors. Most depleted uranium is U-238.
Pu (plutonium)-239
Pu-239 has a half-life of 24,000 years. It is produced in breeder reactors from U-
- Plutonium fission provides about one-third of the total energy produced in a
typical commercial nuclear power plant. Control rods in nuclear power plants
need to be changed frequently due to the buildup of Pu-239 that can be used for
nuclear weapons. International inspections of nuclear power plants monitor the
amount of Pu-239 produced by power plants.
NUCLEAR POWER
As of 2017, 30 countries worldwide were operating 449 nuclear reactors for
electricity generation, with 60 new nuclear power plants under construction,
providing 11% of the world’s energy requirements. The use of nuclear energy as
a source for producing electricity in the United States started during the 1960s
and increased rapidly until the late 1980s. Reasons for its decline included cost
overruns, higher-than-expected operating costs, safety issues, disposal of nuclear
wastes, and the perception of it being a risky investment. However, due to
electricity shortages, fossil fuel price changes and fluctuations, newer and safer
technology, and global warming, there is a renewed interest in and demand for
nuclear power plants.