The RBMK-1000 reactor used in Chernobyl nuclear power station
The RBMK-1000 is a type of pressure
tube reactor designed in the former Soviet Union, which uses ordinary
boiling water as the coolant and graphite as the moderator.
Boiling water acts as a coolant
and also provides the steam used to drive the turbines. The coolant
system of the reactor consisted of two circuits. Water flows through the
coolant circuit I to the fuel channels, where it is boiled by the
uranium fuel inside the pressure tubes, producing steam to feed two 500
MW turbines via the coolant circuit II.
The graphite moderator
is to slow down neutrons to make them more efficient in producing
fission in the fuel. The graphite core of the reactor is about 7 m high
and about 12 m in diameter, composing holes for 1661 fuel channels and
211 control rods. The power of the reactor is controlled by raising or
lowering the control rods, which, when lowered, absorb neutrons and
reduce the fission rate.
RBMK-1000
has potential safety hazards due to its design defects. At low power
output, the reactor becomes unstable and is prone to sudden power
surges. Three safety systems, including an emergency core cooling
system, the requirement for a minimum operation at an electric power of
200 MW, and a minimal insertion of 30 control rods, are included in the
operating procedures.
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