|
PLANT DESCRIPTION
The
Karachi Nuclear Power Plant reactor consists of a cylindrical vessel,
the calandria, which contains heavy water moderator and 208 fuel
channels.
The
moderator, which surrounds the fuel channels, slows down neutrons to
permit fission chain reaction. Adjustment of the moderator level or
volume by reactor regulating computer controls the rate of heat
generated in the reactor. A full calandria provides full power output;
release of the moderator to the dump space shuts down the reactor.
The
natural uranium fuel bundles become hot from the nuclear chain reaction.
Heavy water coolant surrounding the fuel is pumped through the primary
circuit to the steam generators where it gives up its heat to ordinary
water which is converted to steam. This steam is directed under pressure
to a steam turbine and coolant is then pumped back to the reactor on a
continuing cycle. The motion of steam turbine is used to rotate a
conventional electric generator. The resulting electrical energy
produced is sent through power transmission lines to Karachi. The
exhaust steam from the steam turbine passes to a condenser and the
resultant water is pumped back to the steam generators.
A
pressurized helium circuit holds the heavy water moderator at the
required level in the calandria to maintain the nuclear fission of the
uranium. The calandria is enclosed by a thick concrete vault of light
water-to ensure that it remains constantly submerged. The circulation of
water is maintained in the vault, the concrete and the water act as
shields against radiation. The water serves the purpose of cooling the
vault as well.
The
heat from main steam condenser, turbine lubricating oil and
demineralized water is removed through sea water. The demineralized
water extracts heat from reactor auxiliary system equipments and all
coolers associated with conventional systems. The fire water system also
utilizes sea water.
The
ventilation system is designed to provide cooling to all areas of the
Plant. It recovers heavy water from boiler room atmosphere and controls
the air borne radioactivity, in particular tritium, to flow from lower
contamination zones to higher contamination zones. The radioactivity is
controlled to an acceptable limit before being released from the
building to the atmosphere via the stack.
The
reactor protection system is designed to protect the reactor and the
general public by tripping the reactor in case of process malfunctions.
It consists of three identical channels and actuation of any two
channels causes a reactor trip. The shutdown of reactor is achieved by
dumping the moderator in the dump space of the calandria in less than
0.5 seconds.
|
