Nuclear power plant

NUCLEAR POWER PLANT
A.N.KHUDAIWALA (L.M.E) G.P.PORBANDAR

• Define and apply the concepts ofDefine and apply the concepts of mass numbermass number,, atomic numberatomic number,,
andand isotopesisotopes..
• Define and apply concepts ofDefine and apply concepts of radioactive decayradioactive decay andand nuclear reactionsnuclear reactions..
• Calculate theCalculate the mass defectmass defect and theand the binding energy per nucleonbinding energy per nucleon for afor a
particular isotope.particular isotope.
• State the variousState the various conservation lawsconservation laws, and discuss their application for, and discuss their application for
nuclear reactions.nuclear reactions.

All of matter is composed of at least three fundamental particles
(approximations):
All of matter is composed of at least three fundamental particles
(approximations):
ParticleParticle Fig.Fig.SymSym MassMass ChargeCharge SizeSize
The mass of the proton and neutron are close, but they are about 1840 times theThe mass of the proton and neutron are close, but they are about 1840 times the
mass of an electron.mass of an electron.
ElectronElectron ee--
9.11 x 109.11 x 10-31-31
kgkg -1.6 x 10-1.6 x 10-19-19
CC ∼∼
ProtonProton pp 1.673 x 101.673 x 10-27-27
kg +1.6 x 10kg +1.6 x 10-19-19
C 3 fmC 3 fm
NeutronNeutron nn 1.675 x 101.675 x 10-31-31
kgkg 00 3 fm3 fm

Beryllium AtomBeryllium Atom
Compacted nucleus:Compacted nucleus:
4 protons4 protons
5 neutrons5 neutrons
Since atom is electri-callySince atom is electri-cally
neutral, there must be 4neutral, there must be 4
electrons.electrons.
4 electrons4 electrons

AA nucleonnucleon is a general term to denote a nuclear particle - that is, either ais a general term to denote a nuclear particle - that is, either a
proton or a neutron.proton or a neutron.
TheThe atomic numberatomic number ZZ of an element is equal to the number of protons in theof an element is equal to the number of protons in the
nucleus of that element.nucleus of that element.
TheThe mass numbermass number AA of an element is equal to the total number of nucleonsof an element is equal to the total number of nucleons
(protons + neutrons).(protons + neutrons).
The mass number A of any element is equal to the sum of the atomic
number Z and the number of neutrons N :
A = N + Z

A convenient way of describing an element is by giving its mass number andA convenient way of describing an element is by giving its mass number and
its atomic number, along with the chemical symbol for that element.its atomic number, along with the chemical symbol for that element.
A convenient way of describing an element is by giving its mass number andA convenient way of describing an element is by giving its mass number and
its atomic number, along with the chemical symbol for that element.its atomic number, along with the chemical symbol for that element.
[ ]A Mass number
Z Atomic numberX Symbol=
For example, consider beryllium (Be): 9
4 Be

Lithium AtomLithium Atom
N = A – Z =N = A – Z = 7 - 37 - 3
A =A = 7; Z = 3;7; Z = 3; NN = ?= ?
Protons: Z = 3Protons: Z = 3
neutrons:neutrons: NN = 4= 4
Electrons:Electrons: Same as ZSame as Z
7
3 Li

IsotopesIsotopes are atoms that have the same number of protons (are atoms that have the same number of protons (ZZ11= Z= Z22), but a), but a
different number of neutrons (N). (different number of neutrons (N). (AA11 ≠≠ AA22))
Helium - 4Helium - 4
4
2 He
Helium - 3Helium - 3
3
2 He Isotopes ofIsotopes of
heliumhelium

Because of the existence of so many isotopes, the termBecause of the existence of so many isotopes, the term
elementelement is sometimes confusing. The termis sometimes confusing. The term nuclidenuclide is better.is better.
A nuclide is an atom that has a definite mass number A and
Z-number. A list of nuclides will include isotopes.
The following are best described as nuclides:The following are best described as nuclides:
3
2 He 4
2 He 12
6 C 13
6 C

OneOne atomic mass unitatomic mass unit (1 u)(1 u) is equal to one-twelfth of the mass of theis equal to one-twelfth of the mass of the
most abundant form of the carbon atom--most abundant form of the carbon atom--carbon-12carbon-12..
Atomic mass unit: 1 u = 1.6606 x 10-27
kg
Common atomic masses:
Proton: 1.007276 u Neutron: 1.008665 u
Electron: 0.00055 u Hydrogen: 1.007825 u

2 8
; 3 x 10 m/sE mc c= =
Recall Einstein’s equivalency formula for m and E:Recall Einstein’s equivalency formula for m and E:
The energy of a mass of 1 u can be found:The energy of a mass of 1 u can be found:
EE = (1 u)= (1 u)cc22
== (1.66 x 10(1.66 x 10-27-27
kg)(3 x 10kg)(3 x 1088
m/s)m/s)22
E = 1.49 x 10-10
J OrOr E = 931.5 MeV
When converting amu toWhen converting amu to
energy:energy: 2 MeV
u931.5c =

NUCLEAR FUEL
Nuclear fuel is any material that can be consumed
to derive nuclear energy. The most common type of
nuclear fuel is fissile elements that can be made to
undergo nuclear fission chain reactions in a nuclear
reactor
The most common nuclear fuels are 235U and
239Pu. Not all nuclear fuels are used in fission chain
reactions

NUCLEAR FISSION
When a neutron strikes an atom of uranium, the uranium splits
ingto two lighter atoms and releases heat simultaneously.
Fission of heavy elements is an exothermic reaction which can
release large amounts of energy both as electromagnetic radiation
and as kinetic energy of the fragments

NUCLEAR CHAIN REACTIONS
A chain reaction refers to a process in which neutrons released
in fission produce an additional fission in at least one further
nucleus. This nucleus in turn produces neutrons, and the process
repeats. If the process is controlled it is used for nuclear power
or if uncontrolled it is used for nuclear weapons

U235 + n fission + 2 or 3 n + 200 MeV→
If each neutron releases two more neutrons, then the
number of fissions doubles each generation. In that case,
in 10 generations there are 1,024 fissions and in 80
generations about 6 x 10 23 (a mole) fissions.

Nuclear Fission

Nuclear FusionThe combining of atomic nuclei to form a larger
atom is called fusion
Nuclear fusion occurs in the sun where hydrogen
atoms fuse to form helium
4 H + 2 0
e-
 He + energy1
1
-1 2
4

Nuclear Fusion

A chain reaction can only occur if the starting
material has enough mass to sustain a chain
reaction. This amount is called the critical mass.
Nuclear Fission is what occurs in Nuclear
Reactors and Atomic Bombs.
The Nuclear reactor is a controlled fission
reaction, the bomb is not.

Review
Nuclear fission:
A large nucleus splits into several
small nuclei when impacted by a
neutron, and energy is released in
this process
Nuclear fusion:
Several small nuclei fuse
together and release
energy.

Piecing Together a Reactor
1. Fuel
2. Moderator
3. Control Rods
4. Coolant
5. Steam Generator
6. Turbine/Generator
7. Pumps
8. Heat Exchanger
A.N.KHUDAIWALA (L.M.E)
G.P.PORBANDAR

90U (2 ppm)
4.5∙109
yr
90Th (6 ppm)
14.05∙109
yr
238 239
92 94U Pu
99.5%
→
235
92 U
0.7%
Fuels
Natural Elements
233
U
7∙108
yr
Artificial Nuclides
239
Pu
24∙103
yr

Between thorium (Z=90) and bismuth (Z=83), the isotope with the longest half-
life is 226
Ra (T½=1600 years), and therefore there are no fuel candidates, quite
apart from the issue of fissionability. Uranium and Thorium are the only natural
elements available for use as reactor fuels. In addition, 233
U and 239
Pu can be
produced from capture on 232
Th and 238
U in reactors. Of fissile materials, only U
is both fissile and found in nature in useful amounts.

Fuels
Few ”natural” nuclides that can be used as reactor fuels
Uranium (Z=92). This is the main fuel in actual use, especially 235
U which is fissile.
In addition, 238
U is important in reactors, primarily as a fertile fuel for 239
Pu
production, and 233
U could be used as a fissile fuel, formed by neutron capture in
232
Th.
Protactinium (Z=91). The longest-lived isotope of Pa ( 231
Pa) has a half-life of 3.3
x104
yr, and therefore there is essentially no Pa in nature. Further, there is no
stable A =230 nuclide that could be used to produce 231
Pa in a reactor.
Thorium (Z=90). Thorium is found entirely as 232
Th, which is not fissile (for thermal
neutrons). It can be used as a fertile fuel for production of fissile 233
U.

Moderators
1H
Widely
used
H2O or
D2O
2He
Not used
Gas →
Press.
3
He absorbs
3Li
Not used
6
Li
absorbs
4Be
Was
used
9
Be toxic,
expensiv
e
5B
Impossible
10
B
absorbs
6C
Widely used
Must be
pure
No use to consider Z > 6
Only D2O and C can be used with Unat

Moderators
Hydrogen (Z=l). The isotopes 1
H and 2
H are widely used as moderators, in the
form of light (ordinary) water and heavy water, respectively.
Helium (Z=2). The isotopes 3
He and 4
He are not used, because helium is a gas,
and excessive pressures would be required to obtain adequate helium densities
for a practical moderator. Moreover 3
He absorbs neutrons very strongly (see
lecture about detectors)
Lithium (Z=3). The isotope 6
Li (7.5% abundant) has a large neutron-absorption
cross section, making lithium impractical as a moderator.
Beryllium (Z=4). 9
Be has been used to a limited extent as a moderator, especially
in some early reactors. It can be used in the form of beryllium oxide, BeO.
Beryllium is expensive and toxic.

Coolants
Function – transfer heat
Objective: power density, temperature
Limitations: in PWR: below saturation T, Tin=293, Tout
= 315; in LMFBR, ΔT=140; in HTGR, ΔT=500.
After shutdown
Coolant is either gas or liquid: H2O, D2O, He, CO2,
Na, Na-K, Pb, Pb-Bi.
Coolant is moderator
Classification: LWR, HWR, GR, LMR

Coolants
•The main function of the coolant in any generating plant is to transfer energy from
the hot fuel to the electrical turbine, either directly or through intermediate steps
•. During normal reactor operation, cooling is an intrinsic aspect of energy transfer.
• In a nuclear reactor, cooling has a special importance, because radioactive
decay causes continued heat production even after the reactor is shut down and
electricity generation has stopped.
• It is still essential to maintain cooling to avoid melting the reactor core, and in
some types of reactor accidents (e.g., the accident at Three Mile Island) cooling is
the critical issue.
•The coolant can be either a liquid or a gas. For thermal reactors, the most
common coolants are light water, heavy water, helium, and carbon dioxide.
•The type of coolant is commonly used to designate the type of reactor. Hence, the
characterization of reactors as light water reactors (LWRs), heavy water reactors
(HWRs), and gas-cooled reactors (GCRs).

• Control materials are materials with large thermal neutron-absorption
cross sections, used as controllable poisons to adjust the level of
reactivity.
• They serve a variety of purposes:
• To achieve intentional changes in reactor operating conditions, including
turning the reactor on and off
• To compensate for changes in reactor operating conditions, including
changes in the fissile and poison content of the fuel
• To provide a means for turning the reactor off rapidly, in case of
emergency

PWR. The pressurized water reactor accounts for almost two-thirds of all
capacity and is the only LWR used in some countries, for example, France,
the former Soviet Union, and South Korea.
BWR. The boiling water reactor is a major alternative to the PWR, and both
are used in, for example, Sweden, the United States and Japan.
PHWR. The pressurized heavy water reactor uses heavy water for both the
coolant and moderator and operates with natural uranium fuel. It has been
developed in Canada and is commonly referred to as the CANDU. CANDU
units are also in operation in India and are being built in Romania and South
Korea.

32
3232
Classification of reactorsClassification of reactors
Classification of reactors by purpose:
Power reactors
Research reactors
Material test reactors
Propulsion reactors
Production reactors
Space reactors
Radiation Protection Workshop-Cairo Univ.- NSPA - 15 Jan - 2 Feb, 201218 January 2012

33
3333
Classification of reactors (Cont)
Classification of reactors by
neutron spectrum:
Thermal spectrum
Fast spectrum

34
3434
Classification of reactors by coolant
Light water
Heavy water
Gas
Liquid metal

35
3535
Classification of reactors by moderator:
Light water reactors
Heavy water reactors
Graphite moderated reactors

Basic Diagram of a PWR
http://www.nrc.gov/

Boiling Water Reactor (BWR)
Direct Boiling
10% Coolant = Steam
Similar Fuel to PWR
Lower Power Density
than PWR
Corrosion Product
Activated in Core
Higher Radiation Field
GE – ABWR
1350 MWe
(3926 MWt)
UO2 Fuel
60 – yr Service Life
Internalized Safety and
Recirculation Systems

38
3838
Classification of reactors by fuel type

39
3939
Classification of reactors by fertile fuel type

40
4040
Classification of reactors by fissile fuel balance:
Converter reactors
Breeder reactors
Fuel self-sustained (sustaining) reactors

Basic Diagram of a BWR
http://www.nrc.gov/

Classifications of Reactors
Thermal Reactors and Fast Reactors
Reactors designed to operate with slow, thermalized neutrons (to take
advantage of increase of cross-sections with neutron energy decrease) are
termed thermal reactors. However, it is also possible to operate a reactor with
”fast” neutrons, at energies in the neighborhood of 1 MeV or higher. These
reactors are called fast-neutron reactors or just fast reactors. The only
prominent example of a fast reactor is the liquid-metal breeder reactor.
Homogeneous and Heterogeneous Reactors
All reactors used today for power generation are HETEROGENEOUS, i.e. fuel,
coolant and/or moderator are physically different entities with non-uniform and
anisotropic composition.

STEAM GENERATORS
Steam generators are heat exchangers used to convert
water into steam from heat produced in a nuclear reactor
core.
Either ordinary water or heavy water is used as the
coolant.

STEAM TURBINE
A steam turbine is a mechanical device that extracts
thermal energy from pressurized steam, and converts it
into useful mechanical
 Various high-performance alloys and superalloys have
been used for steam generator tubing.

COOLANT PUMP
The coolant pump pressurizes the coolant to pressures
of the orderof 155bar.
The pressue of the coolant loop is maintained almost
constant with the help of the pump and a pressurizer unit.

FEED PUMP
Steam coming out of the turbine, flows
through the condenser for condensation and
recirculated for the next cycle of operation.
The feed pump circulates the condensed
water in the working fluid loop.

CONDENSER
Condenser is a device or unit which is used to condense
vapor into liquid.
The objective of the condenser are to reduce the turbine
exhaust pressure to increase the efficiency and to recover
high qyuality feed water in the form of condensate & feed
back it to the steam generator without any further
treatment.

COOLING TOWER
Cooling towers are heat removal devices used to transfer
process waste heat to the atmosphere.
Water cirulating throughthe codeser is taken to the
cooling tower for cooling and reuse

ADVANTAGES
Nuclear power generation does emit relatively low amounts of
carbon dioxide (CO2). The emissions of green house gases and
therefore the contribution of nuclear power plants to global
warming is therefore relatively little.
This technology is readily available, it does not have to be
developed first.
It is possible to generate a high amount of electrical energy in
one single plant

DISADVANTAGES
The problem of radioactive waste is still an unsolved one.
High risks: It is technically impossible to build a plant with
100% security.
The energy source for nuclear energy is Uranium. Uranium is a
scarce resource, its supply is estimated to last only for the next 30
to 60 years depending on the actual demand.

DISADVANTAGES
Nuclear power plants as well as nuclear waste could be
preferred targets for terrorist attacks..
During the operation of nuclear power plants,
radioactive waste is produced, which in turn can be used
for the production of nuclear weapons.

What is a CANDU reactor?
CANDU stands for Canada Deuterium
Uranium. Deuterium is another name for heavy
water, which occurs naturally in all bodies of
water. In Lake Huron, it occurs one part in
every 7,000. Once extracted, heavy water is 10
per cent heavier than ordinary water due to an
extra neutron in its nucleus giving it added
weight.
Developed in Canada, the first CANDU reactor
came on line in 1962. There are now 22
CANDU reactors in Canada and 17 abroad.

CANDU Reactor
Heavy-water moderator
Natural-uranium dioxide fuel
Pressure-tube reactor
CANDU is a PHWR

CANDU
 Natural-uranium fuel
 Heavy-water moderator &
coolant
Coolant physically separated
from moderator
 Small/Simple fuel bundle
PWR
 Enriched-uranium fuel
 Light-water moderator/coolant
 No separation of coolant from
moderator
 Large, more complex fuel
assembly

Where were the first nuclear
power stations sited and when?
Issues:Issues:
distance from urban centres
access to national grid
good water supply for cooling
absence of natural hazards
transport links
proximity to both civil airports and military
installations

Distance from urban centres and access to the national
grid
Early on, everyone knew that radiation was dangerous. Most
of those alive could remember what happened to Japan when
the H-bombs were dropped and the devastating after effects.
So long as there were concerns about the safety of nuclear
power plants, it was felt that it was essential that they were as
remote as possible from the big cities.
However, in terms of cost and efficiency this had a downside.
Remote areas would not have the heavy duty transmission
lines necessary to take all the electricity generated by the
power station to the grid.
The only feasible way to get it there was by carrying it in huge
ugly pylons that stretch far over the country in a visually
intrusive way.
These remote areas were often near National Parks. The
National parks did not appreciate their presence.

Distance from urban centres and
access to the national grid
But generally the overhead power transmission is very reliable, although
overhead power lines are vulnerable to:
 lightning strikes;
 high winds;
 heavy snowfall.
But the cost of burying and the difficulty in repairing underground cables
if things did go wrong meant that this means of transmitting electricity
almost impossible.
Another problem is that electricity does loose power over distance. So the
electricity from these remote sites did not provide as much energy to the
public as electricity from a power station nearer to centres of population.
So once a design was tested and deemed to be safe, the inclination was to
build the ones that came after closer to centres of population. This cut
down on the number and cost of transmission lines and was a more
efficient use of the electricity.
But when any new technology was developed, the tendency was again to
go for the remoter sites.

Good water supply for cooling
Because of the heat generated by the process, often
more than by coal or gas fired stations, there was a
need for vast quantities of water to carry out the
cooling process.
Cooling towers had been used for coal fired power
stations.
Bigger, tall more intrusive versions would have
required for nuclear power, provide the site was near
enough to a good water supply, like a large river for
example.
The other solution was to put the power station near
the sea, where no cooler tower would be needed. The
sea would always bring in more water to cool the
steam down.

Transport links
For both the building and maintenance of nuclear power
stations, good transport links were a priority.
All nuclear power stations have a rail link, often a side line
from a main line not too far away and very often the roads
have had to be reinforced to take the heavy loads that enter
and leave the power station.
These are massive structures to build, which need very heavy
machinery and vast quantities of raw materials to build them.
Once on-line, the fuel rods which are radioactive have to be
changed regularly. This was the main use of the railway. It
was not acceptable to take these in and out by road as there
could accidents or even terrorism attacks were considered.

Proximity to both civil airports and
military installations
Whilst the buildings that house the nuclear power
stations are extremely strong, aircraft crashing into
them or stray shells falling nearby was not something
the authorities wished to happen.
So military training grounds nearby was a definite
NO.
As 75% of all accidents to planes happen close to
take-off or landing, nuclear power plants could not
be sited under the landing or take-off paths of major
airports.

Absence of natural hazards
Release of radio active materials was the main worry,
so the buildings containing the process could not be
allowed to be damaged by natural hazards, such as
earthquakes, fault lines, floods.
In addition places which liable to high winds,
extremes of temperature or drought, all of which in
excess cause land movements also had to be watched
out for.
However, now that sea levels are rising due to global
warming, this could be problems for those power
stations built near the sea.

•Recently nuclear power has entered many discussions as world energy needs
rise and oil reserves diminish.
•Most opponents of nuclear power point to two main arguments: meltdowns and
nuclear waste.
•Nuclear waste is any form of byproduct or end product that releases
radioactivity.
•How to safely dispose of nuclear waste is pivotal for the continued operation of
nuclear power plants, safety of people living around dump sites, and prevention
of proliferation of nuclear materials to non-nuclear states.

Classifications
Nuclear waste is segregated into several
classifications.
Low level waste is not dangerous but sometimes
requires shielding during handling.
Intermediate level waste typically is chemical
sludge and other products from reactors.
High level waste consists of fissionable elements
from reactor cores and transuranic wastes.
Transuranic waste is any waste with transuranic
alpha emitting radionuclides that have half-lives
longer than 20 years.

Low Level Waste
LLW
Low level waste is any waste that could be from a
high activity area.
90% volume of waste
It does not necessarily carry any radioactivity.
Split into four catagories: A, B, C, and GTCC.

Intermediate Level Waste
ILW
Intermediate level waste requires shielding when
being handled.
Dependent on the amount of activity it can be buried
in shallow repositories.
Not recognized in the United States.

High Level Waste
HLW
High level waste has a large amount of radioactive
activity and is thermally hot.
95% of radioactivity
Current levels of HLW are increasing about 12,000
metric tons per year.
Most HLW consists of Pu-238, 239, 240, 241, 242, Np-
237, U-236

Transuranic Waste TRUW
Transuranic waste consists of all waste that has
radionuclides above uranium.
TRUWs typically have longer half-lives than other
forms of waste.
Typically a byproduct of weapons manufacturing.
Only recognized in the United States.

Waste Management (LLW)
There are several
options available for
the disposal of LLW
due to its lack of
radioactivity.
Waste Isolation Pilot
Plant
On-site disposal
Map of WIPP Facility

Treatment (LLW)
Filtration
Ion Exchange
Evaporation
Incineration
Compaction
Solidification
Typical LLW treatment facility.

Treatment
Most common initial treatment of waste is
vitrification.
Waste is first mixed with sugar and then passed
through a heated tube to de-nitrite the material.
This material is then fed into a furnace and mixed with
glass.
The molten glass mixture is poured into steel cylinders
and welded shut.

Treatment (Cont.)
Mid level active waste is commonly treated with ion
exchange
Process reduces the bulk volume of radioactive
material.
Typically, mixed with concrete for a solid storage
form.

Treatment (Cont.)
Synroc is a new method for storing nuclear waste
developed in 1978 by Ted Ringwood.
Attempts to hold radioactive material in a crystalline
matrix.
Currently in use for military waste management at
Savannah River Site.
Can hold 50%-70% volume of waste.

Deep Geological Repository
Most common method
for handling nuclear
waste.
Typically kept separate
from actual plants and
buried far below ground.
First used in 1999 in the
US.
Current research is
focusing on Yucca
Mountain.
Yucca Mountain Site

Reuse of Nuclear Waste
Research is being performed to find uses for nuclear
waste.
Caesium-137 and strontium-90 already used in
industrial applications.
Some waste can be used for radioisotope
thermoelectric generators (RTGs).
Overall can reduce total HLW but not eliminate it.

Nuclear Plant Future
The countries of the world are each planning their own
course of nuclear plant development or decline
Nuclear power is competitive with natural gas
It is non-polluting
It does not contribute to global warming
Obtaining the fuel only takes 5% of the energy output
Plant licenses have been extended from 20 years to an
additional 20 years

Nuclear Plant Future
Newer designs are being sought to make them more
economical and safer
Preapproval of a few designs will hasten development
Disposal of high level radioactive waste still being
studied, but scientists believe deep burial would work
Because they are have large electrical output, their cost
at $2 billion is hard to obtain and guarantee with banks
Replacing plants may be cheaper using the same sites
and containment vessels

78A.N.KHUDAIWALA (L.M.E) G.P.PORBANDAR

Nuclear power plant

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