Energy and Environment

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COURSE CODE (CC 88-167)

ENERGY AND ENVIRONMENT
Part II: Energy and Essential Resources
Chapter 5: Nuclear Power

1.
2.
3.
4.
5.
6.

Working principle
Nuclear reactors
Detection and safety issues
Radioactive wastes treatment
Comparison to other powers
Possible alternatives

1

Do you know?

2

Mass & Atomic Numbers
Isotopes

All of the following are possible sources of
radiation except
a. background radiation from the Earth’s
crust.
b. nuclear waste.
c. medical & dental X-rays.
d. distilled water.

A
Z

X

Symbol

12

13

14

6

6

6

C

Carbon-12

C

C

Carbon-13 Carbon-14

• Mass number (A) =
– No. of __________ + No. of __________ in the nucleus of
an atom

• Atomic number (Z) =
3

– No. of _____________ in the nucleus of an atom
– No. of _____________ in the neutral atom

4

Isotopes

Types of Radiation

• Contain different no. of __________ but the same no.
of __________ & __________
• Behave the same chemically but other characteristics
may differ profoundly



1.
2.
3.



Natural radioactive materials




__ Rays ( 4He/ 4 )
2
2
Made up of

__ Rays (

0
-1

Made up of

particles (Helium nucleus minus 2e–), +2

0
/ -1 e)

particles (Electron), negligible mass

__ Rays ( 0 )
0

Similar to X-rays, No mass, high-energy _____________
_________________ with very short wavelength

Not emitted simultaneously
Have sufficient energy to break chemical bonds, thus
disrupt living organisms

5

6

EM Spectrum Properties

7

8

1. From Mass to Energy


Nuclear Fission & Fusion

Nuclear energy
– Different from burning fuels/other chemical reactions
– Involves changes at the atomic level
– Released from either
1. Fission (A large atom of 1 element is _________________
2 atoms of different elements)
2. Fusion (2 small atoms _________________ a larger atom
of a different element)

9

Fuel Element (235U)

Fission of 235U
• A neutron hits the nucleus of 235U

2 Isotopes

235
92

U

Uranium-235
(143 neutrons)

– Some atoms of 235U undergo radioactive decay &
release neutrons
– These neutrons can hit other 235U atoms, producing
highly unstable 236U
– 236U undergoes fission into lighter atoms (fission
products)

238

U

92

Uranium-238
(146 neutrons)

• Uranium occurs naturally in the Earth’s crust

• More neutrons are given off, releasing lots of
energy

– Exists in 2 isotopes mainly, 238U & 235U

• All nuclear plants use 235U as fuel


235U

readily undergoes fission, but not 238U

10

– This domino effect causes a chain reaction
11

12

Fission Reactions

Amplification

Barium (Ba)

Low energy
(slow) neutrons

Krypton (Kr)

Leads to nuclear explosion!

1. n + 235U → Kr + Ba + ___ n + Energy
92
36
56
or
2. n + 235U → 36Kr + 56Ba + ___ n + Energy
92
13

Control

14

2. Reactor Core
• Fuel rods
– Radioactive spent-fuel rods are replaced with new
ones

• Control rods
– Neutron-absorbing materials slow down the rate of
fission & heat production
Extra neutrons are absorbed in control rods: No amplification! 15

• Inside a water-holding vessel (the moderator &
coolant)
16

Long metal tubes

Type of Nuclear Reactors


(Uranium pellets)

A device allows us to extract energy from
nuclear fission
1. Pressurized-water reactor (2/3 of US power
station)


Employ double loop isolating the pressurized water
from the steam-generating loop that drives the
turbogenerator

2. Boiling-water reactor


Boil the water by circulating it via the reactor

3. Breeder reactor (More advanced)

19

18

Advanced Boiling-Water Reactor

Pressurized-Water Reactor

17

20

238
1
92 U + 0n
(_____________)

Breeder Reactors

239
92 U

• Also named as “fast-neutron” reactor

239
93 Np
(__________)

– U.S. used for military purposes
– France, Russia, Japan...
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