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Nuclear Power Generation is cheapest
source of Electric Power and creates least Pollution to the Environment.
Even Hydro Power creates very high pollution to the Environment.
Advanced Nuclear Reactor are very safe and new technology under
development will make future reactors very safe and environmental
friendly source of Electric Power Generation.
CO2 Generated by Power Plants is
compared for various countries:
Advanced Nuclear Power Reactors
The nuclear power industry has been
developing and improving reactor technology for 50 years and now
preparing for the next generations of reactors. Generation III (and 3+)
are the Advanced Reactors. Generation IV designs are still being
designed and will not be operational till year 2020. Third-generation
reactors have:
• a standardized design for each type to expedite licensing, reduce
capital cost and reduce construction time,
• a simpler and more rugged design, making them easier to operate and
less vulnerable to operational upsets,
• higher availability and longer operating life,
• reduced possibility of core melt accidents,
• minimal effect on the environment,
• higher burn-up to reduce fuel use and the amount of waste,
• burnable absorbers to extend fuel life.
There are several components common to most types of reactors:
• Fuel: Usually pellets of uranium oxide (UO2) arranged in tubes to form
fuel rods. The rods are arranged into fuel assemblies in the reactor
core.
• Moderator: This is material which slows down the neutrons released
from fission so that they cause more fission. It is usually water, but
may be heavy water or graphite.
• Control rods: These are made with neutron-absorbing material such as
cadmium, hafnium or boron, and are inserted or withdrawn from the core
to control the rate of reaction, or to halt it. (Secondary shutdown
systems involve adding other neutron absorbers, usually as a fluid, to
the system.)
• Coolant: A liquid or gas circulating through the core so as to
transfer the heat from it. In light water reactors the moderator
functions also as coolant.
• Pressure vessel or pressure tubes: Usually a robust steel vessel
containing the reactor core and moderator/coolant, but it may be a
series of tubes holding the fuel and conveying the coolant through the
moderator.
• Steam generator: Part of the cooling system where the heat from the
reactor is used to make steam for the turbine.
• Containment: The structure around the reactor core which is designed
to protect it from outside intrusion and to protect those outside from
the effects of radiation in case of any malfunction inside. It is
typically a meter-thick concrete and steel structure.
Most reactors need to be shut down for refuelling, so that the pressure
vessel can be opened up. In this case, refuelling is at intervals of 1-2
years, when a quarter to a third of the fuel assemblies are replaced
with fresh ones.
Inside a nuclear reactor the nuclei of
U-235 atoms split (fission) and, in the process, release energy. This
energy is used to heat water and turn it into steam. The steam is used
to drive a turbine connected to a generator which produces electricity.
Some of the U-238 in the fuel is turned into plutonium in the reactor
core. The main plutonium isotope is also fissile and it yields about one
third of the energy in a typical nuclear reactor. The fissioning of
uranium is used as a source of heat in a nuclear power station in the
same way that the burning of coal, gas or oil is used as a source of
heat in a fossil fuel power plant.
With time, the concentration of
fission fragments and heavy elements formed in the same way as plutonium
in a fuel bundle will increase to the point where it is no longer
practical to continue to use the fuel. So after 12-24 months the 'spent
fuel' is removed from the reactor. The amount of energy that is produced
from a fuel bundle varies with the type of reactor and the policy of the
reactor operator.
Typically, some 36 million kilowatt-hours of electricity are produced
from one tonne of natural uranium. The production of this amount of
electrical power from fossil fuels would require the burning of over
20,000 tonnes of black coal or 8.5 million cubic metres of gas.
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