# Harvesting Nuclear Energy web

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```					Harvesting Nuclear Energy
The Nucleus
•Every atom has a nucleus made up of protons and
neutrons; together they are called nucleons
•Atomic number (Z) = number of protons; all atoms of the
same element must have the same number of protons
•Atomic mass number (A) = number of protons + neutrons
•Isotopes – atoms of the same element that have different
numbers of neutrons
•Nuclear notation:
A = atomic mass number
A
Z   X                   Z = atomic number
X = element symbol
A – Z = # neutrons
Eg. 1 Write beryllium-9 and beryllium-10 using nuclear
notation.
9                 10
4   Be             4   Be
Complete Practice Problem #28 – pg. 503

•Transmutation or radioactive decay is when an atom
spontaneously changes from one element into another
element
•Occurs when the strong nuclear force holding the
nucleus together cannot overcome the electrostatic force
between the positively charged protons
•Can release three kinds of radiation – alpha, beta and
gamma
Alpha Radiation - Occurs when an atom releases an alpha
particle (helium nucleus) – two protons and two neutrons;
Z decreases by 2 and A decreases by 4:

Z
A
P        A 4
Z 2  D  He 2
4

i.e.
235    4     231
92 U 2 He  90Th
Eg. 2 Write a balanced nuclear equation describing the
decay of americium-241 that results in an alpha particle and
another product.

241     4     237
95 Am 2 He  93 Np
Complete Practice Problems # 29, 30, 31 – pg. 506
Beta Radiation - Occurs when a neutron converts itself into
one proton and one electron; the electron is ejected and the
proton stays in the nucleus

P           D 
Z increases by 1:      A            A        0
Z         Z 1       1
i.e.

10       0 10
4 Be  1 e  5 B
Eg. 3 Write a balanced nuclear equation for the beta decay of
carbon-14.
14      0 14
6 C  1 e  7 N
Complete Practice Problems # 32, 33 – pg. 507
Gamma Radiation – is not a stream of charged particles like
alpha and beta radiation, but a stream of gamma photons;
emitted along with alpha or beta decay, or on its own:

0
0
Gamma radiation is extremely harmful to living tissue,
especially to DNA. It is frequently used to kill cancerous cells.
Eg. 3 Write a balanced nuclear equation to describe the
emission of beta and gamma radiation from cobalt-60.

27 Co 0   1 e  28 Ni
60     0      0     60

Complete Practice Problems # 34, 35 – pg. 509
Alpha, beta and gamma radiation are called ionizing
radiation - they can ionize material they penetrate.
Shielding prevents damage by using a material that
absorbs the radiation emitted by an isotope.
Different properties of radiation mean the material that will
shield one type of radiation may not shield another.
Gamma radiation requires several metres of concrete or
can penetrate a piece of paper. Beta radiation can be
stopped by 3 mm of aluminum.
A Geiger counter displays the number of charged particles
and/or photons that have entered the device.
Nuclear Fission
•Reaction used to release energy in CANDU reactors
•Involves splitting the atom by hitting its nucleus with a
neutron
•The nucleus breaks into two smaller nuclei
i.e.
235    1            1     92     141
92 U 0 n       3 0 n  36 Kr  56 Ba

•The kinetic energies of the fission products add up to much
more than the energy released in a chemical reaction
•Used in the first atomic bombs (uncontrolled chain
reaction - exponential increase in products)
•Used to generate electricity: (pg. 510)
1. Nuclear potential energy of isotope is converted to
kinetic energy of fission products and is transferred
as heat to water
2. Water boils and turns to steam
3. Steam turns a turbine
4. Turbine spins a generator
5. Generator produces electricity
Can control the energy released by controlling the neutrons in
the reactor with heavy water or control rods.
Poor control of fission reactions can cause a rapid release of
energy - nuclear meltdown.
Complete Practice Problem # 37 – pg. 512
Mass-Energy Equivalence
Einstein said that mass could be converted to energy and
energy converted to mass according to:
 E =  mc2 (in DB – pg. 8)
E = change in energy
 m = change in mass
c = speed of light (3.00 x 108 m/s)
Only the unaccounted for mass is converted to energy (the
mass that ‘disappeared’).
A small change in mass corresponds to a very large change in
energy.
Eg. 4 See handout.
Nuclear Fusion
•Requires very high temperatures - occurs in the Sun’s core
i.e.       2    2    3     1
1 H 1 H 2 He 0 n  energy

•Two smaller nuclei join to form a larger nucleus, while
simultaneously releasing a lot of energy - like the opposite of
fission
•Deuterium (a heavy isotope of hydrogen) is needed for
fusion and is very plentiful in sea water - making it a
renewable resource
•Currently a lot of research into using fusion to meet energy
demands
Complete Practice Problems # 40, 41 – pg. 517

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