2. About one – sixth off the world’s electricity is generated by nuclear
power plants over 435 of them are currently in operation around the globe.
The nuclear power plant stands on the border between humanity’s greatest
hopes and the deepest fears for the future.
Nuclear power plant have an important role in our country. Why? Just
because it can easily provide electrical energy to produce light, to entertain
us while watching television, etc. And it does not contribute to carbon
emissions, simply no carbon dioxide (CO2) is given out, therefore it does not
cause global warning.
A nuclear power plant is a (given) place where people make
electricity using heat from nuclear reactions. The plant also has machines
which remove heat from the reactor to operate of steam turbine and
generator to make electricity. Nuclear power plants are usually near water
to remove the heat the reactor makes. But what happens inside a nuclear
power plants to such marvels?
3. Nuclear Power Plants produce to controlled air pollutions such
as sulphur and particulates or greenhouse gases. The use of nuclear
energy in place of other energy sources helps to keep the air
clean, presence the earth’s climate avoid ground level ozone
formation and prevent acid rain. Of all energy sources, nuclear
energy has perhaps the lowest impact on the environment
specially in relation to kilowatts produced because nuclear power
plants do not emit harmful gases, require relatively, small area and
effectively minimize or negative other impacts. In other words,
nuclear power plant is the most “ecologically efficient” provides of
all energy sources. Why? Because it produces the most electricity in
relation to its minimal environment impact.
4. HISTORY
As of 16 January 2013, the IAEA report there are 439 nuclear
power reactors in operation operating in 31 countries. Nuclear
power plants are usually considered to be base load stations,
since fuel is a small part of the cost of production.
Electricity was generated by a nuclear reactor for the first
time ever on September 3, 1948 at the X-10 Graphite
Reactor in Oak Ridge, Tennessee in the United States, and was
the first nuclear power plant to power a light bulb. The second,
larger experiment occurred on December 20, 1951 at the EBR-
I experimental station near Arco, Idaho in the United States. On
June 27, 1954, the world's first nuclear power plant to generate
electricity for a grid started operations at the Soviet city
of Obninsk. The world's first full scale power station, Calder Hall in
England opened on October 17, 1956.
5. Nuclear power was considered as a solution to the 1973
oil crisis, in which the Philippines was affected. The Bataan
Nuclear Power Plant was built in the early 1980s but never went
into operation because it sits on a tectonic fault and volcano.
The Fukushima nuclear disaster gave pause to efforts to revive
the plant.
6. The Philippine Nuclear Power Plant started in 1958 with
the creation of the Philippine Atomic Energy Commission
(PAEC) under a regime of martial law, Philippine
President Ferdinand Marcos in July 1973 announced the
decision to build a nuclear power plant. This was in response
to the 1973 oil crisis, as the Middle East oil embargo had put a
heavy strain on the Philippine economy, and Marcos
believed nuclear power to be the solution to meeting the
country's energy demands and decreasing dependence on
imported oil.
7. Construction on the Bataan Nuclear Power Plant began
in 1976. Following the 1979 Three Mile Island accident in
the United States, construction on the BNPP was stopped,
and a subsequent safety inquiry into the plant revealed over
4,000 defects. Among the issues raised was that it was built
near major earthquake fault lines and close to the then
dormant Pinatubo volcano.
By 1984, when the BNPP was nearly complete, its cost
had reached $US2.3 billion. Equipped with
a Westinghouse light water reactor, it was designed to
produce 621 megawatts of electricity.
8. Marcos was overthrown by the People Power
Revolution in 1986. Days after the April 1986 Chernobyl
disaster, the succeeding administration of President Corazon
Aquino decided not to operate the plant. Among other
considerations taken were the strong opposition from Bataan
residents and Philippine citizens.
The government sued Westinghouse for overpricing and
bribery but was ultimately rejected by a United States court.
Debt repayment on the plant became the country's biggest
single obligation. While successive governments have looked
at several proposals to convert the plant into an oil, coal, or
gas-fired power station, these options have all been deemed
less economically attractive in the long term than simply
constructing new power stations.
9. A nuclear power plant is a thermal power station in
which the heat source is a nuclear reactor. As is typical in all
conventional thermal power stations the heat is used to
generate steam which drives a steam turbine connected to
a generator which produces electricity. As of
16 January 2013, the IAEA report there are 439 nuclear power
reactors in operation operating in 31 countries.
Nuclear power plants are usually considered to be base
load stations, since fuel is a small part of the cost of
production.
10.
11.
12.
13.
14. Pressurized Water Reactor
- Pressurized Water Reactors (also known as PWRs) keep
water under pressure so that it heats, but does not boil. This
heated water is circulated through tubes in steam
generators, allowing the water in the steam generators to
turn to steam, which then turns the turbine generator. Water
from the reactor and the water that is turned into steam are
in separate systems and do not mix.
15. Boiling Water Reactor
- In Boiling Water Reactors (also known as BWRs), the
water heated by fission actually boils and turns into steam to
turn the turbine generator. In both PWRs and BWRs, the steam
is turned back into water and can be used again in the
process.
19. A Nuclear Reactor produces and controls the release
of energy from splitting the atoms of uranium.
The only purpose of a nuclear power plant is to
produce electricity. To produce electricity, a power
plant needs a source of heat to boil water which
becomes steam. The steam then turns a turbine, the
turbine an electrical generator, and the generator
produces electricity.
20. BATAAN NUCLEAR POWER PLANT
The bataan nuclear power plant (BNPP) is located at
napot point, within the municipality of morong, bataan. The
plant is similar in design concept with the krsko Nuclear Power
Plant in Yugoslavia.. The BNPP employs a westing house –
designed pressurized water reactor, light – water moderated
and having a two – loop primary cooling system. The reactor
core uses a 16 x 16 array of fuel assemblies supplied by
westing house. The reactor is designed to operate at a power
level of 1,876 mwt (megawatts thermal) equivalent to a
maximum net electrical output of 621 MWE (megawatts
electric)
21. 1. WHY DO WE NEED NUCLEAR POWER PLANT?
In late 1973, the first world oil crisis erupted. The price of
crude oil more than quadrupled from US.$2.55 per barrel in
April 1973 to US $10.84 per barrel in December 1974 and at
the same time, OPEC imposed a partial oil embargo to the
Philippines. With the Philippines 95% dependent on imported
oil for its commercial energy consumption, the crisis has
unfolded the country’s absolute vulnerability to drastic
changes in the international oil market.
22. In January 1974, the country needed non-oil energy projects for
immediate implementation to relieve the grim possibility facing Luzon.
Evaluation of existing or indigenous sources of energy needed to meet
the projected power demand was undertaken. We were only starting to
explore geothermal potential in commercial quantities, the first live well
being struck only in November 1974. The 50 MW Pantabangan Multi-
Purpose project which was being constructed, was upgraded to 100 MW
and the hydro power potentials of other Luzon rivers were looked into.
The country’s coal reserves have not yet been established. Minable
reserves were established only in 1980 in Semirara Island. Thus, the only
viable alternative source of bulk energy seemed to be nuclear power
which has been the subject of almost 20 years of exhaustive studies
undertaken by both local and foreign experts. Nuclear power, along
with geothermal, coal and hydro will be vital in reducing the country’s
heavy dependence on high-priced and unreliable imported fuel oil. It
will improve the country’s supply of electricity which is vital to a
developing economy.
23. 2. FACILITIES
- BNPP has the following principal plant
structures: (a) the reactor containment
building; (b) the turbine building; (c) the
auxiliary building complex; (d) the fuel handling
building; (e) the intake structure; and (f) the
ultimate heat sink.
24. 2.1 REACTOR CONTAINMENT BUILDING
- This building contains the containment which is enclosed by a
concrete shield building. The containment is a free-standing cylindrical steel
shell with a hemispherical dome and elliptical bottom designed to withstand
maximum temperature and pressure expected from the steam produced if all
water in the primary system were expelled into the containment. The
containment is normally slightly below atmospheric pressure, so that leakage
through the containment walls would at most times be inward from the
surroundings. Inside the containment structure, the reactor and other nuclear
steam supply system components are shielded with concrete. In addition, a
containment spray system and a containment recirculation and associated
cooling system are provided to remove post-accident heat. The concrete
shield building surrounding the containment provides biological protection
against radiation during normal and accident conditions. The building also
provides volume space or sealed containment for radioactive releases from
the containment during normal and abnormal operation.
25. 2.2 TURBINE BUILDING
- This building contains the low and high pressure
steam turbines, the electrical generator and all the
power-conversion related equipment.
26. 2.3 AUXILIARY BUILDING COMPLEX
- The building complex includes the control
building, the component cooling building, the diesel
generator building, the intermediate building and the
auxiliary building.
27. 2.4 FUEL HANDLING BUILDING
- The fuel handling building is an integral
part of the auxiliary building complex. It
contains the spent fuel pool which is lined with
stainless steel to prevent leakage of water.
28. 2.5 INTAKE STRUCTURE
- The intake structure is situated along the shoreline of
the South China Sea within the nuclear plant perimeter. The
structure contains traveling water screens, the circulating
water pumps, and auxiliary service equipment, providing
waste heat removal function. This structure is connected by a
reinforced concrete intake tunnel to the main condenser
water boxes and turbine plant auxiliary heat exchangers via
valved piping connections. The main condenser water boxes
and turbine plant auxiliary heat exchangers are connected
by a reinforced concrete discharge tunnel, via valved piping
connections, to the sealwell, and then to the South China
Sea.
29. 3. IMPORTANT COMPONENT OF A NUCLEAR POWER PLANT
3.1 Core – It’s the focal
point of the reactor,
where fuel is contained
and nuclear fission
reactions take place.
30. 3.2 Fuel –is made of small
enriched uranium oxide
rods, stacked so as to form
cylinders, approx. 4 metres
long and with a diameter
of about one centimetre.
These rods are wrapped in
metal sheathes (steel or
zirconium alloy), which
allow heat to pass through
while blocking the
radioactive elements
produced by fission.
31. 3.3 Moderator – This
is a material placed
in the reactor to
slow down the
neutrons produced
by fission, in order to
reach the most
suitable speed
allowing the chain
reaction to
continue.
32. 3.4 Heat-transfer fluid (or coolant) - This fluid (liquid or gas) cools the core
and carries outside the heat that is produced there. The most commonly
used fluid is water, but some types of reactors use different fluids (heavy
water, molten sodium, carbon dioxide, helium and other fluids).
33. 3.5 Control rods – These are rods
used in specific materials (silver,
indium, cadmium or boron carbide)
to control fission inside the core.
Since they absorb neutrons, they are
capable of controlling the chain
reaction which - depending on how
deep down the rods are inserted into
the core - can be accelerated,
slowed down or even stopped, thus
changing the capacity of the
reactor. Indeed, if necessary, the
reactor can be immediately
stopped when they are fully inserted.
34. 3.6 Vessel – The
large steel recipient
containing the core,
the control rods and
the heat-transfer
fluid.
35. 4. SYSTEMS
- The conversion to electrical energy takes place
indirectly, as in conventional thermal power plants. The heat
is produced by fission in a nuclear reactor (a light water
reactor). Directly or indirectly, water vapor (steam) is
produced. The pressurized steam is then usually fed to a multi-
stage steam turbine. Steam turbines in Western nuclear
power plants are among the largest steam turbines ever.
After the steam turbine has expanded and partially
condensed the steam, the remaining vapor is condensed in
a condenser. The condenser is a heat exchanger which is
connected to a secondary side such as a river or a cooling
tower. The water is then pumped back into the nuclear
reactor and the cycle begins again. The water-steam cycle
corresponds to the Rankine cycle.
36. 4.1 NUCLEAR REACTORS
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 electric energy and for
the propulsion of ships.
The nuclear reactor is the heart of the plant. In its central
part, the reactor core's heat is generated by controlled nuclear
fission. With this heat, a coolant is heated as it is pumped
through the reactor and thereby removes the energy from the
reactor. Heat from nuclear fission is used to raise steam, which
runs through turbines, which in turn powers either ship's
propellers or electrical generators.
37. 4.1.1 Mechanism of Nuclear Reactor
- An induced nuclear fission event. A neutron is absorbed by the
nucleus of a uranium-235 atom, which in turn splits into fast-moving lighter
elements (fission products) and free neutrons. Though both reactors
and nuclear weapons rely on nuclear chain-reactions, the rate of reactions in
a reactor occurs much more slowly than in a bomb.
4.1.2 Fission
- When a large fissile atomic nucleus such as uranium-235 or plutonium-
239 absorbs a neutron, it may undergo nuclear fission. The heavy nucleus
splits into two or more lighter nuclei, (the fission products), releasing kinetic
energy, gamma radiation, and free neutrons. A portion of these neutrons
may later be absorbed by other fissile atoms and trigger further fission events,
which release more neutrons, and so on. This is known as a nuclear chain
reaction.
38. 4.1.3 Heat Generation
- The kinetic energy of fission products is converted to thermal
energy when these nuclei collide with nearby atoms.
The reactor absorbs some of the gamma rays produced during
fission and converts their energy into heat.
Heat is produced by the radioactive decay of fission products
and materials that have been activated by neutron absorption. This
decay heat-source will remain for some time even after the reactor is
shut down.
A kilogram of uranium-235 (U-235) converted via nuclear
processes releases approximately three million times more energy than
a kilogram of coal burned conventionally (7.2 × 1013 joules per kilogram
of uranium-235 versus 2.4 × 107 joules per kilogram of coal).
39. 4.1.4 Cooling
- A nuclear reactor coolant — usually water but sometimes a gas or a
liquid metal (like liquid sodium) or molten salt — is circulated past the reactor
core to absorb the heat that it generates. The heat is carried away from the
reactor and is then used to generate steam. Most reactor systems employ a
cooling system that is physically separated from the water that will be boiled
to produce pressurized steam for the turbines, like the pressurized water
reactor. But in some reactors the water for the steam turbines is boiled directly
by the reactor core, for example the boiling water reactor.
4.1.5 Reactivity Control
- The power output of the reactor is adjusted by controlling how many
neutrons are able to create more fissions.
Control rods that are made of a neutron poison are used to absorb neutrons.
Absorbing more neutrons in a control rod means that there are fewer neutrons
available to cause fission, so pushing the control rod deeper into the reactor
will reduce its power output, and extracting the control rod will increase it.
40. 4.1.6 Electrical Power Generation
- The energy released in the fission process generates
heat, some of which can be converted into usable energy. A
common method of harnessing this thermal energy is to use it
to boil water to produce pressurized steam which will then
drive a steam turbine that turns an alternator and generates
electricity.
41. 4.2 STEAM TURBINE
The purpose of the steam turbine is to convert the heat contained in
steam into mechanical energy. The engine house with the steam turbine is
usually structurally separated from the main reactor building. It is so aligned to
prevent debris from the destruction of a turbine in operation from flying
towards the reactor.
In the case of a pressurized water reactor, the steam turbine is
separated from the nuclear system. To detect a leak in the steam generator
and thus the passage of radioactive water at an early stage, an activity meter
is mounted to track the outlet steam of the steam generator. In contrast,
boiling water reactors pass radioactive water through the steam turbine, so
the turbine is kept as part of the control area of the nuclear power plant.
42. 4.2.1 Blade and Stage Design
- Steam turbines are made in a variety of sizes ranging from
small 0.75 kW units used as mechanical drives for pumps,
compressors and other shaft driven equipment, to 1,500,000kW
turbines used to generate electricity. Steam turbines are widely
used for marine applications for vessel propulsion systems. In
recent times gas turbines, as developed for aerospace
applications, are being used more and more in the field of
power generation once dominated by steam turbines.
- Turbine blades are of two basic types,
blades and nozzles. Blades move entirely due
to the impact of steam on them and their
profiles do not converge. This results in a steam
velocity drop and essentially no pressure drop
as steam moves through the blades. A turbine
composed of blades alternating with fixed
nozzles is called an impulse turbine, Curtis
turbine, Rateau turbine, or Brown-Curtis turbine.
Nozzles appear similar to blades, but their
profiles converge near the exit. This results in a
steam pressure drop and velocity increase as
steam moves through the nozzles. Nozzles
move due to both the impact of steam on
them and the reaction due to the high-velocity
steam at the exit. A turbine composed of
moving nozzles alternating with fixed nozzles is
called a reaction turbine or Parsons turbine.
Schematic diagram outlining
the difference between an impulse and
a 50% reaction turbine
43. 4.2.2 Steam supply and exhaust conditions
- Condensing turbines are most commonly found in electrical power plants.
These turbines exhaust steam from a boiler in a partially condensed state, typically
of a quality near 90%, at a pressure well below atmospheric to a condenser.
- Non-condensing or back pressure turbines are most widely used for process
steam applications. The exhaust pressure is controlled by a regulating valve to suit
the needs of the process steam pressure. These are commonly found at refineries,
district heating units, pulp and paper plants, and desalination facilities where large
amounts of low pressure process steam are needed.
- Reheat turbines are also used almost exclusively in electrical power plants. In
a reheat turbine, steam flow exits from a high pressure section of the turbine and is
returned to the boiler where additional superheat is added. The steam then goes
back into an intermediate pressure section of the turbine and continues its
expansion.
- Extracting type turbines are common in all applications. In an extracting
type turbine, steam is released from various stages of the turbine, and used for
industrial process needs or sent to boiler feed water heaters to improve overall cycle
efficiency. Extraction flows may be controlled with a valve, or left uncontrolled.
- Induction turbines introduce low pressure steam at an intermediate stage to
produce additional power.
A low-pressure steam turbine
working below atmospheric
pressure in a nuclear power
plant
44. 4.2.3 Casing or shaft arrangements
- These arrangements include single casing, tandem
compound and cross compound turbines. Single casing units
are the most basic style where a single casing and shaft are
coupled to a generator. Tandem compound are used where
two or more casings are directly coupled together to drive a
single generator. A cross compound turbine arrangement
features two or more shafts not in line driving two or more
generators that often operate at different speeds. A cross
compound turbine is typically used for many large
applications.
45. 4.2.4 A Two – flow Turbine Rotors
- The moving steam imparts both
a tangential and axial thrust on the
turbine shaft, but the axial thrust in a
simple turbine is unopposed. To maintain
the correct rotor position and
balancing, this force must be
counteracted by an opposing force.
Either thrust bearings can be used for
the shaft bearings, or the rotor can be
designed so that the steam enters in the
middle of the shaft and exits at both
ends. The blades in each half face
opposite ways, so that the axial forces
negate each other but the tangential
forces act together. This design of rotor is
called two-flow, double-axial-flow,
or double-exhaust. This arrangement is
common in low-pressure casings of a
compound turbine.
A two-flow turbine rotor. The
steam enters in the middle of the
shaft, and exits at each end,
balancing the axial force.
46. 4.3 GENERATOR
- The generator converts
kinetic energy supplied by
the turbine into electrical
energy. Low – pole AC
Synchronous generators of
high rated power are used.
47. 4.3.1 Dynamo
- A dynamo is an electrical generator that
produces direct current with the use of a
commutator. Dynamos were the first electrical
generators capable of delivering power for
industry, and the foundation upon which many
other later electric-power conversion devices
were based, including the electric motor, the
alternating-current alternator, and the rotary
converter. Today, the simpler alternator
dominates large scale power generation, for
efficiency, reliability and cost reasons. A
dynamo has the disadvantages of a
mechanical commutator. Also, converting
alternating to direct current using power
rectification devices (vacuum tube or more
recently solid state) is effective and usually
economic.
48. 4.3.2 Alternator
- Without a commutator, a dynamo becomes an alternator, which is a
synchronous singly fed generator. Alternators produce alternating current with
a frequency that is based on the rotational speed of the rotor and the
number of magnetic poles.
- Automotive alternators produce a varying frequency that changes
with engine speed, which is then converted by a rectifier to DC. By
comparison, alternators used to feed an electric power grid are generally
operated at a speed very close to a specific frequency, for the benefit of AC
devices that regulate their speed and performance based on grid frequency.
Some devices such as incandescent lamps and ballast-operated fluorescent
lamps do not require a constant frequency, but synchronous motors such as in
electric wall clocks do require a constant grid frequency.
-Typical alternators use a rotating field winding excited with direct
current, and a stationary (stator) winding that produces alternating current.
Since the rotor field only requires a tiny fraction of the power generated by
the machine, the brushes for the field contact can be relatively small. In the
case of a brushless exciter, no brushes are used at all and the rotor shaft
carries rectifiers to excite the main field winding.
49. 4.3.3 Induction Generator
- An induction generator or asynchronous generator is a
type of AC electrical generator that uses the principles
of induction motors to produce power. Induction generators
operate by mechanically turning their rotor faster than the
synchronous speed, giving negative slip. A regular AC
asynchronous motor usually can be used as a generator, without
any internal modifications. Induction generators are useful in
applications such as minihydro power plants, wind turbines, or in
reducing high-pressure gas streams to lower pressure, because
they can recover energy with relatively simple controls.
To operate an induction generator must be excited with a
leading voltage; this is usually done by connection to an
electrical grid, or sometimes they are self-excited by using phase
correcting capacitors.
50. 4.3.4 MHD Generator
- A magneto hydrodynamic generator directly extracts
electric power from moving hot gases through a magnetic field,
without the use of rotating electromagnetic machinery. MHD
generators were originally developed because the output of a
plasma MHD generator is a flame, well able to heat the boilers
of a steam power plant. The first practical design was the AVCO
Mk. 25, developed in 1965. The U.S. government funded
substantial development, culminating in a 25 MW
demonstration plant in 1987. In the Soviet Union from 1972 until
the late 1980s, the MHD plant U 25 was in regular commercial
operation on the Moscow power system with a rating of 25 MW,
the largest MHD plant rating in the world at that time. MHD
generators operated as a topping cycle are currently (2007) less
efficient than combined cycle gas turbines.
51. 4.3.5 Homopolar Generator
- A homopolar generator is a DC electrical
generator comprising an electrically conductive
disc or cylinder rotating in a plane perpendicular
to a uniform static magnetic field. A potential
difference is created between the center of the
disc and the rim (or ends of the cylinder), the
electrical polarity depending on the direction of
rotation and the orientation of the field. It is also
known as a unipolar generator, acyclic
generator, disk dynamo, or Faraday disc. The
voltage is typically low, on the order of a few volts
in the case of small demonstration models, but
large research generators can produce hundreds
of volts, and some systems have multiple
generators in series to produce an even larger
voltage. They are unusual in that they can
produce tremendous electric current, some more
than a million amperes, because the homopolar
generator can be made to have very low internal
resistance.
Faraday disk, the first
homopolar generator
52. 4.3.6Excitation
- An electric generator or electric motor that uses field coils rather than
permanent magnets requires a current to be present in the field coils for the device to
be able to work. If the field coils are not powered, the rotor in a generator can spin
without producing any usable electrical energy, while the rotor of a motor may not
spin at all. Smaller generators are sometimes self-excited, which means the field coils
are powered by the current produced by the generator itself. The field coils are
connected in series or parallel with the armature winding. When the generator first
starts to turn, the small amount of remanent magnetism present in the iron core
provides a magnetic field to get it started, generating a small current in the armature.
This flows through the field coils, creating a larger magnetic field which generates a
larger armature current. This "bootstrap" process continues until the magnetic field in
the core levels off due to saturation and the generator reaches a steady state power
output.
Very large power station generators often utilize a separate smaller generator
to excite the field coils of the larger. In the event of a severe widespread power
outage where islanding of power stations has occurred, the stations may need to
perform a black start to excite the fields of their largest generators, in order to restore
customer power service.
53. A small early 1900s 75 kVA direct-driven power station AC alternator, with a
separate belt-driven exciter generator.
54. 4.3.7 Electrostatic Generator
- An electrostatic generator, or electrostatic
machine, is a mechanical device that produces static
electricity, or electricity at high voltage and low continuous
current. The knowledge of static electricity dates back to
the earliest civilizations, but for millennia it remained merely
an interesting and mystifying phenomenon, without a
theory to explain its behaviour and often confused with
magnetism. By the end of the 17th Century, researchers
had developed practical means of generating electricity
by friction, but the development of electrostatic machines
did not begin in earnest until the 18th century, when they
became fundamental instruments in the studies about the
new science of electricity. Electrostatic generators operate
by using manual (or other) power to transform mechanical
work into electric energy. Electrostatic generators develop
electrostatic charges of opposite signs rendered to two
conductors, using only electric forces, and work by using
moving plates, drums, or belts to carry electric charge to a
high potential electrode. The charge is generated by one
of two methods: either the triboelectric effect (friction) or
electrostatic induction. A Van de Graaff generator,
for class room demonstrations
55. Suppose that the conditions are as in the figure,
with the segment A1 positive and the segment B1
negative. Now, as A1 moves to the left and B1 to the
right, their potentials will rise on account of the work
done in separating them against attraction. When A1
and neighboring sectors comes opposite the segment
B2 of the B plate, which is now in contact with the
brush Y, they will cause a displacement of electricity
along the conductor between Y and Y1 bringing a
negative charge, larger than the positive charge in A1
alone, on Y and sending a positive charge to the
segment touching Y1. As A1 moves on, it passes near
the brush Z and is partially discharged into the external
circuit. It then passes on until, on touching the brush X,
has a new charge, this time negative, driven into it by
induction from B2 and neighboring sectors. As the
machine turns, the process causes exponential
increases in the voltages on all positions, until sparking
occurs limiting the increase.
56. 4.3.8 Wimshurst Machine
- The Wimshurst influence machine is
an electrostatic generator, a machine for
generating high voltages developed
between 1880 and 1883 by
British inventor James Wimshurst (1832–1903).
It has a distinctive appearance with
two large contra-rotating discs mounted in a
vertical plane, two crossed bars with metallic
brushes, and a spark gap formed by two
metal spheres.
57. 4.3.9 Van De Graff Generator
- A Van de Graaff generator is an electrostatic
generator which uses a moving belt to accumulate very
high voltages on a hollow metal globe on the top of the
stand. It was invented by American physicist Robert J. Van de
Graaff in 1929. The potential difference achieved in modern
Van de Graaff generators can reach 5 megavolts. The Van
de Graaff generator can be thought of as a constant-current
source connected in parallel with a capacitor and a very
large electrical resistance, so it can produce a visible
electrical discharge to a nearby grounding surface which
can potentially cause a "spark" depending on the voltage.
58. 4.4 COOLING SYSTEM
- A cooling system removes heat from the reactor core and transports it
to another area of the plant, where the thermal energy can be harnessed to
produce electricity or to do other useful work. Typically the hot coolant is used
as a heat source for a boiler, and the pressurized steam from that boiler
powers one or more steam turbine driven electrical generators.
4.5 SAFETY VALVES
- In the event of an emergency, two independent safety valves can be
used to prevent pipes from bursting or the reactor from exploding. The valves
are designed so that they can derive all of the supplied flow rates with little
increase in pressure. In the case of the BWR, the steam is directed into the
condensate chamber and condenses there. The chambers on a heat
exchanger are connected to the intermediate cooling circuit.
59. 4.6 FEEDWATER PUMP
- The water level in the steam generator and nuclear reactor is
controlled using the feedwater system. The feedwater pump has the task of
taking the water from the condensate system, increasing the pressure and
forcing it into either the steam generators (in the case of a pressurized water
reactor) or directly into the reactor vessel (for boiling water reactors).
4.7 EMERGEMCY POWER SUPPLY
- The emergency power supplies of a nuclear power plant are built up by
several layers of redundancy, such as diesel generators, gas turbine generators
and battery buffers. The battery backup provides uninterrupted coupling of the
diesel/gas turbine units to the power supply network. If necessary, the
emergency power supply allows the safe shut down of the nuclear reactor. Less
important auxiliary systems such as, for example, heat tracing of pipelines are
not supplied by these back ups. The majority of the required power is used to
supply the feed pumps in order to cool the reactor and remove the decay
heat after a shut down.
60. 5. HOW DOES A NUCLEAR POWER PLANT
PRODUCE ELECTRICITY?
- A nuclear power plant is basically steam power that is
fuelled by a radioactive element, like uranium. The fuel is
placed in a reactor and the individual atoms are allowed to
split apart. The splitting process, known as fission, releases
great amounts of energy. This energy is used to heat water
until it turns to steam.
From here, the mechanics of a steam power plant take
over. The steam pushes on turbines, which force coils of wire
to interact with a magnetic field. This generates on electric
current.
61. ENVIRONMENT / ECONOMIC EFFECT
- Nuclear power plant is a
controversial subject and multi –
billion dollar investments ride on the
choice of an energy source.
Nuclear power plants typically have
high capital costs. But low direct fuel
costs, with the costs of fuel
extraction, processing, use and sent
fuel storage internalized costs.
On the other hand
construction or capital costs, aside
measures to mitigate global
warning such as a carbon fax or
emissions trading, increasingly
favour the economics and nuclear
power.
63. ADVANTAGES
Nuclear power plants don't require a lot of space - they have to be
built on the coast, but do not need a large plot like a wind farm.
It doesn't contribute to carbon emissions - no CO2 is given out - it
therefore does not cause global warming.
It does not produce smoke particles to pollute the atmosphere.
Nuclear energy is by far the most concentrated form of energy - a lot
of energy is produced from a small mass of fuel. This reduces transport
costs - (although the fuel is radioactive and therefore each transport
that does occur is expensive because of security implications).
It is reliable. It does not depend on the weather. We can control the
output It is relatively easy to control the output - although the time
factor for altering power output is not as small as for fossil fuel stations.
It produces a small volume of waste
64. DISADVANTAGES
• Disposal of nuclear waste is very expensive. As it is radioactive it has
to be disposed of in such a way as it will not pollute the
environment.
• Decommissioning of nuclear power stations is expensive and takes
a long time. (In fact we have not ever decommissioned one!)
• Nuclear accidents can spread radiation producing particles over a
wide area, This radiation harms the cells of the body which can
make humans sick or even cause death. Illness can appear or strike
people years after they were exposed to nuclear radiation and
genetic problems can occur too. A possible type of reactor disaster
is known as a meltdown. In a meltdown, the fission reaction of an
atom goes out of control, which leads to a nuclear explosion
releasing great amounts of radioactive particles into the
environment. See Chernobyl.
65. BASIC TERMS, CONCEPTS, AND DEFINITIONS
RELATED TO NUCLEAR ENERGY
• Chernobyl: A nuclear power plant in Russia that suffered a meltdown in 1986.
The accident released a significant amount of radioactive material into the
air, causing the deaths of several dozen people in the following months and
resulting in an estimated 4,000 cases of terminal cancer in people as far
away as North America.
• Fuel Rods: Hollow rods filled with uranium pellets, which are lowered into vats
of water prior to the introduction of the neutrons that cause fission. Fuel rods
are used in most nuclear power plants.
• Meltdown: An accident in which the fuel in a nuclear reactor overheats and
melts the containment structures in the plant.
• Nuclear Fission: The process of splitting an atom by introducing a neutron
into the atom's nucleus, thus creating two lighter atoms and producing heat.
• Uranium: A common element, synthesized in stars, which has been present in
the earth since its formation and exists in rocks, soil, and water.
66. CURRENT ISSUES
Problems of Nuclear Reactors
Concerns about the safety of nuclear fission reactors include the
possibility of radiation-releasing nuclear accidents, the problems
of radioactive waste disposal, and the possibility of contributing
to nuclear weapon proliferation.
Although most technical analyses have rated nuclear electricity
generation as comparable in safety to coal-powered generation, the
low public confidence in nuclear power has blocked further
development of nuclear power in the United States. No new nuclear
power plants have been ordered since the Three Mile Island accident,
and some partially completed projects have been abandoned. As of
1990 about 20% of electricity in the U.S. was generated by nuclear
plants, compared to about 75% in France.
67. Reactor Accidents
The nuclear accident at Chernobyl was the worst
nuclear accident to date, spewing about 100 million Curies of
radioactive material into the environment. By contrast, the
accident at Three Mile Island released only some 15 Curies.
Though its health effects were minimal, Three Mile Island did
perhaps irreparable damage to the level of public
confidence in nuclear reactors for electric power production
in the United States.
Preceding these two high-profile accidents are a
number of nuclear accidents with radiation release. These
include accidents at the Fermi I reactor near Detroit, at the
NRX reactor at Chalk River, Canada, at
the Windscale reactor in England, and the SL-1 Reactor
at Idaho Falls.
68. Radioactive Waste Disposal
The nuclear fission of uranium-235 produces large quantities of
intermediate mass radioisotopes. The mass distribution of these
radioisotopes peaks at about mass numbers 95 and 137 , and most of
them are radioactive. The most dangerous for environmental release
are probably cesium and strontium because of their intermediate half-
lives and propensity for reconcentration in the food chain.
When spent fuel assemblies are removed from nuclear reactors,
they are transported to "swimming pool" storage facilities to dissipate
the heat of decay of short-lived isotopes as well as for isolation from the
environment. The long term disposal of these wastes remains a major
problem. It was assumed that these wastes would be encased in glass
and placed in geologic disposal sites in underground salt domes. The
site at Yucca Mountain was chosen as a first site, but both technical
and political problems have thus far blocked its implementation.
69. Nuclear Weapons Proliferation
One concern about nuclear reactors is that the fuel
could be diverted for the production of nuclear weapons.
While the the uranium fuel is enriched to only 3-5% and could
not easily be further separated to the >90% U-235 needed to
produce a bomb, the spent fuel elements contain plutonium-
239. The plutonium could be separated chemically and
diverted to nuclear weapons production. Security concerns
about the plutonium has thus far blocked any reprocessing of
fuel from nuclear power plants.
A similar concern exists for fast breeder reactors, where
the breeding process produces plutonium-239 for future
generations of reactors.
70. CONCLUSION
Nuclear power is an efficient and volatile method of creating
electricity using controlled nuclear fission, or, less
commonly, nuclear fusion. Most nuclear power plants create energy by
submerging uranium molecules in water and then inducing fission in the
molecules. This process heats the water, which is transformed into
pressurized steam that turns a turbine powering a generator,
creating energy. Some nuclear plants use plutonium or thorium instead
of uranium, while others fuse hydrogen atoms to create helium atoms, a
process that also causes heat and, subsequently, energy. However,
uranium fission is overwhelmingly the most popular form of creating
nuclear power because the element is more common than plutonium
or thorium.
Nuclear power plants produce no controlled air pollutants, such
as sulfur and particulates, or greenhouse gases. It is important to our
lives because it can easily provide electrical energy and no carbon
dioxide is given to cause global warning not just like other power station
or electrical commissioning.
71. REFERENCE
• The word of physics. Philippine edition. Vern J. Ostdiek. Donald J. Bord
• www.world-nuclear.org/info/current-and-future-Generationandfuture-
generation/outline-historyofnuclear-energy
• http://en.m.Wikipedia.org/wiki/nuclear-power
• http://en.m.Wikipedia.org/wiki/batan-nuclear-power-plant
• http://www.duke-energy.com/about-enegy/generating-
electricity/nuclear-how.asp
• YouTube/Canadian/Nuclear Safety Commission
• http://zidbits.com/tag/nuclear-power/
• http://en.Wikipedia.org/wiki/Nuclear-reactor
http://en.Wikipedia.org/wiki/Electricgenerator
72. Member:
Leader: MONTEALTO, JAYSON L.
Secretary: AGOJO, DULCE
Other Member:
MACARANAS, CRIS L.
GADIN, JAY
ARGANA, KELVIN
LUISTRO, CHRISTIAN
LOJO, GERALD
BSCS 2A(N)
MASANGKAY, JEE-AN MAE
HERNANDEZ, MARY JANE
BERIÑA, MARK ANTHONY
PEZA, ROXANNE
LAGO, LINDSAY LOU FELRAE L.
