nuclear reactors TYPES AND FEATURES

2. A nuclear reactor is a device to initiate,
and control, a sustained nuclear chain
reaction. The most common use of
nuclear reactors is for the generation
of electrical power ( Nuclear power) and
for the power in some ships (Nuclear
marine propulsion). This is usually
accomplished by methods that involve
using heat from the nuclear reaction to
power steam turbines. There are also
other less common uses of nuclear
reactors, to be discussed later.

3. The first artificial nuclear reactor, Chicago Pile-1, was constructed at the University of
Chicago by a team led by Enrico Fermi in 1942. It achieved criticality on December 2, 1942.
The reactor support structure was made of wood, which supported a pile of graphite
blocks, embedded in which was natural Uranium-oxide 'pseudo spheres' or 'briquettes'.
Shortly after the discovery of fission, Hitler's Germany invaded Poland in 1939,
starting World War II in Europe, and all such research became militarily classified.

4. Reactor Generations
http://www.whitehouse.gov/

5. World Nuclear Power
• 443 Nuclear Reactors
in 30 Countries in
Operation, January
2006
• Provided ~16% World
Production of Energy
in 2003
• 24 Nuclear Power
Plants under
Construction
http://www.insc.anl.gov

6. Classification by use
1.Electricity Nuclear power plants
2.Nuclear propulsion in marine and
Various proposed
forms of rocket propulsion
3.Other uses of heat
i.Desalination.
ii.Heat for domestic and industrial heating.
iii.Hydrogen production for use in a hydrogen
economy.
4.Production type reactors for transmutation of elements
i.Creating various radioactive isotopes, such as americium for use in smoke detectors, and
cobalt-60, molybdenum-99 and others, used for imaging and medical treatment.
ii.Production of materials for nuclear weapons such as weapons-grade plutonium

7. 5.Providing a source of neutron radiation (for example with the pulsed Godiva
device) and
positron radiation(e.g. neutron activation analysis and potassium-argon dating).
6.Research reactor: Typically reactors used for research and training, materials
testing, or the production of radioisotopes for medicine and industry. These are
much smaller than power reactors or those propelling ships, and many are on
university campuses. There are about 280 such reactors operating, in 56 countries.
Some operate with high-enriched uranium fuel, and international efforts are
underway to substitute low-enriched fuel.

8. Clean air
One of the greatest
benefits of nuclear plants is
that they have no smoke
stacks! The big towers many
people associate with nuclear
plants are actually for cooling
water used to make steam.
(Some other kinds of plants
have these towers, too.) The
towers spread the water out so
as much air as possible can
reach it and cool it down. Most
water is then recycled into the
plant. The puffs you see coming
out of a cooling tower are just
clouds of water vapor.

9. Since early 1990s, Russia has been a major source of nuclear fuel to India. Due
to dwindling domestic uranium reserves, electricity generation from nuclear power
in India declined by 12.83% from 2006 to 2008.Following a waiver from
the Nuclear Suppliers Group in September 2008 which allowed it to commence
international nuclear trade, India has signed nuclear deals with several other
countries including France, United States, United
Kingdom,Canada, Namibia, Mongolia, Argentina,Kazakhstan.
In February 2009,
India also signed a $700 million deal with Russia for the supply of 2000 tons
nuclear fuel.

10. Nuclear power is the fourth-
largest source
of electricity in India after thermal,
hydro and renewable sources of
electricity. As of 2010, India has
19 nuclear power plants in
operation generating 4,560 MW
while 4 other are under
construction and are expected to
generate an additional 2,720
MW.India is also involved in the
development of fusion reactors
through its participation in
the ITER project.

12. Currently, nineteen nuclear power reactors produce 4,560.00 MW (2.9% of total installed base).

15. In a fission reactor, large
fissile atomic nucleuses such
as uranium-235 or plutonium-
239 undergo nuclear fission when
they absorb a neutron. The heavy
nucleus splits into two or more
lighter nuclei, releasing kinetic
energy, gamma radiation and free
neutrons; collectively known
as fission products. A kilogram
of uranium-235 (U-235) converted
via nuclear processes contains
approximately three million times
the energy of a kilogram of coal
burned conventionally
(7.2 × 1013
Joules per kilogram of
uranium-235 versus
2.4 × 107
Joules per kilogram of
coal).

16. To turn nuclear fission into electrical energy,
the first step for nuclear power plant operators
is to be able to control the energy given off by
the enriched uranium and allow it to
heat water into steam. Enriched uranium is
typically formed into inch-long (2.5-cm-long)
pellets,
the pellets are arranged into long rods, and the
rods are collected together into bundles. The
bundles are submerged in water inside a
pressure vessel. The water acts as a coolant.
For the reactor to work, the submerged
bundles must be slightly supercritical. Left to its
own devices, the uranium would eventually
overheat and melt.

17. To prevent overheating, control rods made of a material that absorbs neutrons are
inserted into the uranium bundle using a mechanism that can raise or lower the control
rods. Raising and lowering the control rods allow operators to control the rate of the
nuclear reaction. When an operator wants the uranium core to produce more heat, the
control rods are raised out of the uranium bundle (thus absorbing fewer neutrons). To
create less heat, they are lowered into the uranium bundle. The rods can also be
lowered completely into the uranium bundle to shut the reactor down in the case of an
accident or to change the fuel.
The uranium bundle acts as an extremely high-energy source of heat. It heats the water and
turns it to steam. The steam drives a turbine, which spins a generator to produce power
In some nuclear power plants, the steam from the reactor goes through a secondary,
intermediate heat exchanger to convert another loop of water to steam, which drives the
turbine. The advantage to this design is that the radioactive water/steam never contacts the
turbine. Also, in some reactors, the coolant fluid in contact with the reactor core is gas (carbon
dioxide) or liquid metal (sodium, potassium); these types of reactors allow the core to be
operated at higher temperatures.

18. 1.Boiling Water Reactor
In the boiling water reactor (BWR), the water which passes over the reactor core to act
as moderator and coolant is also the steam source for the turbine. The disadvantage of this
is that any fuel leak might make the water radioactive and that radioactivity would reach
the turbine and the rest of the loop.
A typical operating pressure for such reactors is about 70 atmospheres at which pressure
the water boils at about 285 C. This operating temperature gives a efficiency of only 42%
with a practical operating efficiency of around 32%, somewhat less than the Pressurized
Water Reactor

19. 2.Pressurized Water Reactors
In the pressurized water reactor (PWR), the water which passes
over the reactor core to act as moderator and coolant does not
flow to the turbine, but is contained in a pressurized primary loop.
The primary loop water produces steam in the secondary loop
which drives the turbine. The obvious advantage to this is that a
fuel leak in the core would not pass any radioactive contaminants
to the turbine and condenser.
Another advantage is that the PWR can operate at higher pressure
and temperature, about 160 atmospheres and about 315 C. This
provides a higher efficiency than the boiling water reactor , but the
reactor is more complicated and more costly to construct. Most of
the U.S. reactors are pressurized water reactor.

21. This is a reactor design that is cooled by liquid metals like
sodium, NaK, lead, lead-bismuth eutectic are included totally unmoderated,
and produces more fuel than it consumes. They are said to "breed" fuel,
because they produce fissionable fuel during operation because of neutron
capture. These reactors can function much like a PWR in terms of efficiency,
and do not require much high pressure containment, as the liquid metal does
not need to be kept at high pressure, even at very high temperatures. BN-
350 and BN-600 in USSR and Superphénix in France were this type of reactors.
3.Liquid-Metal Fast-Breeder Reactor

22. Pressurized Heavy Water Reactor (PHWR) is a Canadian design (known
as CANDU), these reactors are heavy-water-cooled and -moderated
Pressurized-Water reactors. Instead of using a single large pressure vessel as
in a PWR, the fuel is contained in hundreds of pressure tubes. These reactors
are fueled with natural uranium and are thermal neutron reactor designs.
PHWRs can be refueled while at full power, which makes them very efficient
in their use of uranium (it allows for precise flux control in the core). CANDU
PHWRs have been built in Canada, Argentina, China, India (pre-
NPT), Pakistan (pre-NPT), Romania, and South Korea.
The CANDU Qinshan Nuclear Power Plant
4.Pressurized Heavy Water Reactor (PHWR)

23. These are generally graphite moderated and CO2
cooled. They can have a high thermal
efficiency compared with PWRs due to higher operating temperatures. There are
a number of operating reactors of this design, mostly in the United Kingdom,
where the concept was developed. Older designs (i.e. Magnox stations) are either
shut down or will be in the near future. However, the AGCRs have an anticipated
life of a further 10 to 20 years. This is a thermal neutron reactor design.
Decommissioning costs can be high due to large volume of reactor core.
The Torness nuclear power station— an AGR
5.Gas Cooled Reactor (GCR) and Advanced
Gas Cooled Reactor (AGR)

25. Current nuclear reactors use nuclear fission to generate power. In nuclear fission,
you get energy from splitting one atom into two atoms. In a conventional nuclear
reactor, high-energy neutrons split heavy atoms of uranium, yielding large amounts
of energy, radiation and radioactive wastes that last for long periods of time.
In nuclear fusion, you get energy when two atoms join together to form one. In a
fusion reactor, hydrogen atoms come together to form helium atoms, neutrons and
vast amounts of energy. It's the same type of reaction that powers hydrogen bombs
and the sun. This would be a cleaner, safer, more efficient and more abundant
source of power than nuclear fission.

27. There are several types of fusion reactions. Most involve the
isotopes of hydrogen called deuterium and tritium:
Proton-proton chain - This sequence is the predominant fusion
reaction scheme used by stars such as the sun.
1.Two pairs of protons form to make two deuterium atoms.
Each deuterium atom combines with a proton to form a
helium-3 atom.
2 .Two helium-3 atoms combine to form beryllium-6, which
is unstable.
Beryllium-6 decays into two helium-4 atoms. These
reactions produce high energy particles (protons, electrons,
neutrinos, positrons) and radiation (light, gamma rays).
3.Deuterium-deuterium reactions - Two deuterium atoms
combine to form a helium-3 atom and a neutron.
4.Deuterium-tritium reactions - One atom of deuterium
and one atom of tritium combine to form a helium-4 atom and a
neutron. Most of the energy released is in the form of the high-
energy neutron.

28. Controlled nuclear fusion could in principle be used in fusion power plants to produce power
without the complexities of handling actinides, but significant scientific and technical
obstacles remain. Several fusion reactors have been built, but as yet none has 'produced'
more thermal energy than electrical energy consumed. Despite research having started in the
1950s, no commercial fusion reactor is expected before 2050. The ITER project is currently
leading the effort to commercialize fusion power.

29. Radioactive waste is
a waste product
containing radioactive
material. It is usually the
product of a nuclear
process such as nuclear
fission,etc.
High level radioactive waste is
generally material from the core of the
nuclear reactor or nuclear weapon.
This waste includes uranium,
plutonium, and other highly
radioactive elements made during
fission. Most of the radioactive
isotopes in high level waste emit large
amounts of radiation and have
extremely long half-lives (some longer
than 100,000 years) creating long time
periods before the waste will settle to
safe levels of radioactivity. Some of
the methods being under
consideration for dealing with this
high level waste include short term
storage , long term storage,
and transmutation.

30. Improper
waste
disposal