Can
you imagine a coal or gas based power plant to generate more coal or
gas in the end, than what it has burnt in generating power? This is
something that is not in the realm of possibility for sure. When we
generate power using fossil fuels, we end up producing only mountains
of ash and some bye product gases.
Yet
there are power generating systems that can breed more fuel than they
consume. Because of this they are called as Fast breeder reactors or
FBR. What Physical processes are actually involved in the working of
such a reactor? We all know that conventional nuclear reactors use
fissionable Uranium-235 isotope as the basic fuel. However it so
happens that in nature only 0.7 % of all Uranium mineral deposits
contain Uranium-235, whereas 99.3 % Uranium that is found in nature
is of Uranium 238 isotope, which is non fissionable.
Under
appropriate operating conditions, the neutrons given off by fission
reactions can "breed" more fuel from otherwise
non-fissionable isotopes. The most common breeding reaction is that
of plutonium-239 from non-fissionable uranium-238. The term "fast
breeder" refers to the types of configurations which can
actually produce more fissionable fuel than they use. This scenario
is possible because the non-fissionable uranium-238 is 140 times more
abundant than the fissionable U-235 and can be efficiently converted
into Pu-239 by the neutrons from a fission chain reaction.
Kalpakkam
is a small town in Tamil Nadu state of India, situated on the
Coromandel Coast, 70 kilometers south of Chennai. Madras Atomic Power
Station located at Kalpakkam is a comprehensive nuclear power
production, fuel reprocessing, and waste treatment facility that also
includes plutonium fuel fabrication for fast breeder reactors (FBRs).
It is also India's first fully indigenously constructed nuclear power
station. It has two units of 220 MW capacity each. The first and
second units of the station went critical in 1983 and 1985
respectively. It was here in Kalpakkam, that the first experimental
Fast Breeder Test Reactor (FBTR) was jointly designed and constructed
by the Indira Gandhi Center for Atomic Research (IGCAR) and Bhabha
Atomic Research Center (BARC). The reactor designed to generate 13.2
MW of electrical power went critical in 1985 and is being operated
since then. The FBTR is a liquid metal fast breeder reactor based on
the French "Rapsodie" design. The reactor uses a
plutonium-uranium mixed carbide fuel and liquid sodium as a coolant.
The fuel is an indigenous mix of 70 percent plutonium carbide and 30
percent uranium carbide. Plutonium for the fuel is extracted from
irradiated fuel in the Madras power reactors and reprocessed in
Tarapur. Anyone, who knows little bit of chemistry would know that
all these materials, particularly Sodium are extremely dangerous to
handle. Readers would be able to appreciate, the complexity of such
type of reactors easily and the fact that fabrication of gigantic
PFBR components involves highly complex technology.
Indian
nuclear scientists began construction of a much larger Prototype of
500 MW Fast Breeder Reactor (PFBR) at Kalpakkam in 2004. The reactor
was supposed to go critical in 2010. However because of technical
difficulties this did not happen so far. The Indira Gandhi Centre for
Atomic Research (IGCAR), Kalpakkam, has designed and developed the
technology for the PFBR. It is expected that the loading of 1,750
tonnes of liquid sodium into seven loops in the reactor will commence
in two weeks from now. Mr. Prabhat Kumar, is the chairman and
Managing Director of Bharatiya Nabhikiya Vidyut Nigam Limited
(BHAVINI), a public sector undertaking of the Department of Atomic
Energy (DAE). He is in charge of commissioning of the reactor. He
says that most of the piping and instrumentation is ready and stands
energized. Instruments and sensors have been connected to the Control
Room. And results of the tests done so far are encouraging. Most of
the support systems are fully commissioned and operating
satisfactorily. They include raw water system, service water system,
air mask system, nitrogen system, argon system etc. All the
electrical systems including the switch-yard and battery banks are
operational. Dummy fuel has been loaded in the reactor
It is
expected that this 500-MW Prototype Fast Breeder Reactor (PFBR)
would be commissioned before March 2015. It is going to be a quantum
jump for Kalpakkam engineers to move from a 13.2 MW reactor to this
giant, which will produce 500 MW of electrical power.
19
July 2014
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