# Energy a la Einstein

Mass can be converted into energy with a yield governed by the Einstein relationship:

E=mc2

where c = the speed of light. The yield from converting one kilogram is

E=(1 kg)(3 x 108)2= 9 x 1016 joules

The energy consumption for one U.S. citizen for one year is about

 1 US year* = 5 x 1011 Joules Fuel requirement

So one kilogram of mass conversion could supply the needs of about 180,000 U.S. citizens for one year, or the needs of a city of one million for over two months.

* This amount will be used as a comparison unit when discussing
energy production by nuclear fission and nuclear fusion.
Index

Fission concepts

 HyperPhysics***** Nuclear R Nave
Go Back

# How Much Fuel per U.S. Citizen?

To supply the yearly average of 5 x 1011 joules per U.S. citizen per year (used as a reference unit ) would require:

However, direct mass conversion is not possible on a large scale. A fraction of the mass can be converted to energy by:

Nuclear fission: the breaking up of heavy nuclei.
or
Nuclear fusion: the combining of light nuclei.
Index

Fission concepts

 HyperPhysics***** Nuclear R Nave
Go Back

# Nuclear Fission Reactors

Current uses of nuclear energy must rely on nuclear fission, a less-than-ideal energy source, since nuclear fusion has yet to be harnessed for electricity generation. The heat from the nuclear fission is used to:

This usually done in a Boiling Water Reactor (BWR) or a Pressurized Water Reactor (PWR), but there are other options such as the fast breeder reactor.

Index

Fission concepts

 HyperPhysics***** Nuclear R Nave
Go Back

# Nuclear Electricity Generation

At the end of 1989 there were 416 nuclear fission power plants operating worldwide, producing about 17% of the worlds electricity. 130 more were in design or construction stages. The U.S. nuclear energy program is the world's largest with 108 operating plants with 100, 000 MW capacity, providing some 20% of the country's electricity in 1989. Coal provides about 55% of the country's electricity, natural gas (9%), oil (6%), and hydropower (9%).

Nuclear electricity generation became unpopular in the United States after the accident at Three Mile Island in 1979. No new orders for nuclear power plants have been placed in the US since the mid 1970s.

Index

Fission concepts

 HyperPhysics***** Nuclear R Nave
Go Back