Environmental Engineering Reference
In-Depth Information
The energy released by nuclear fission is large compared to the energy produced
in the burning of such fuels, which is why it is possible to generate large quantities
of electricity with small amounts of uranium. For example, 1 kg of uranium
“burned” in a nuclear reactor can produce 50,000 kWh, while 1 kg of coal can pro-
duce only 1 kWh (
Table 6.1
).
Of the uranium found in nature only 0.7% can be used in a nuclear reactor. Put
another way, only 7 out of every 1,000 atoms of uranium are “useful” for the pro-
duction of energy. For this reason the preparation of nuclear fuel requires a com-
plex “fuel cycle,” beginning with the extraction and purification of uranium salts,
and then to their conversion to a gas and the “enrichment” of the uranium into the
fissionable isotope
235
U. Once enriched uranium rods are prepared, they constitute
the core of the nuclear reactors for electricity production.
The coolant in a reactor takes away the heat generated in the fission process,
limiting the temperature rise in the rectors. It also transfers the heat to the power
unit, where the electricity is generated.
There are basically two types of nuclear reactors: boiling water reactors (BWR),
which produce vapor inside the reactor, and pressurized water reactors (PWR),
which pressurize hot water (rather than boiling it) while removing the heat.
In 2010, there were 442 reactors worldwide, producing 14% of the world's elec-
tricity. Out of these, 104 are in the United States, 50 in France, 54 in Japan, 32 in
the Russian Federation, 21 in South Korea, and 17 in Germany. In the United States
they represented 19% of the total generated electricity and in France approximately
80%. The remaining reactors are installed in developing countries, mainly in China
