Nuclear Fission Reactions

Essential Standard 2.3

Understand the role of the nucleus in

radiation and radioactivity.

Learning Objective 2.2.6

Compare nuclear fusion and fission

reactions including alpha decay, beta

decay, and gamma decay.

I Can StatementsAt the end of this lesson, you should be

able to say, with confidence:

• I can explain what happens during nuclear

fission reactions

• I can list two uses of nuclear fission.

• I can describe the benefits and drawback

of using nuclear power as an energy

source.

Nuclear ReactionsThere are two types of nuclear reactions:

Nuclear Fusion and Nuclear Fission.

Nuclear Reactions

During nuclear fusion

reactions, smaller particles or

atoms are fused together to

form larger atoms.

During nuclear fission

reactions, larger atoms

split apart into smaller

atoms and neutron

particles.

Nuclear FissionDuring nuclear fission, free neutrons strike an

atom, splitting it into smaller atoms while also

releasing free neutrons.

Chain ReactionThe free neutrons then go on to split other atoms

causing multiple chain reactions.

Use of Nuclear Fission

Nuclear fission is used in

nuclear bombs to set off

uncontrolled chain

reactions.

Nuclear fission is also

used at nuclear power

plant, but in this case

the chain reactions are

controlled .

Nuclear BombsIn a nuclear bomb such as that used on Hiroshima,

uranium is shot at another source of uranium,

triggering a series of uncontrolled chain reactions.

Hiroshima

Nuclear BombsToday’s nuclear bombs are thousands times more

powerful than those dropped on Japan.

The Tsar Bomba,

detonated by the Soviet

Union in 1961, was

3,333 times more

powerful than Little Boy.

Here’s How Much Deadlier Today’s Nukes are Compared to WWII’s

A-Bombs, by Popular Mechanics

Nuclear Power PlantsNuclear fission is also used in nuclear power plants, but

in this case the chain reaction is controlled.

In order to control the

reaction, power plants

provide a source such

as boron and carbon,

to accept the free

neutrons.

The boron carbide compound is placed in long

cylindrical tubes called control rods.

Nuclear Power PlantsThe nuclear power source, usually uranium, is placed

into fuel pellets that are then placed into fuel rods.

The control rods are

lowered between the fuel

rods, when they want to stop

the reaction or lifted when

they want to begin reactions.

Control Rods

Nuclear Reactor

Another way to control the

nuclear reaction is by ensuring

all of the nuclear reactions

take place under water.

All of the nuclear

reactions take place

inside a nuclear

reactor that is

encased in layers of

cement and steel.

Nuclear ReactorThe heat from the nuclear reactions is used to

change water into steam.

The turning of the magnet inside the wire coil

generates electricity.

The steam is then

used to turn a

turbine that is

connected to a

magnet inside a

gigantic wire coil.

Nuclear Reactor WaterThe water that the fuel rods are immersed in is always

kept separate from the water that is turned into steam.

The radioactive water in the diagram is red and yellow

and the water turned into steam is blue. Notice they are

each in separate closed systems.

Source of Steam Water

Nuclear power plants, such

as the Shearon Harris Plant,

in Wake County, NC, are

always built near a body of

water (Lake Jordan).

To cool the steam so it

can be used again,

water from a nearby

body of water is used

to condense the steam

back into water.

Currently, nearly 20% of

all electricity in the

United States is

produced by nuclear

power plants.

Some European

nations, especially

France, use nuclear

power to generate

nearly all of their

electricity.

Nuclear Power Use

France

Benefits of Nuclear PowerNuclear power costs

less to produce than

fossil fuels and is far

more efficient with 90%

of energy being turned

into electricity.

Nuclear power requires less raw material than

fossil fuels. (20 g Uranium = 444 kg Coal)

Benefits of Nuclear Power

Nuclear power is also very clean in that it releases no carbon dioxide that accelerates the greenhouse effect and global climate change.

It also releases no sulfur and nitrogen oxides that

mix with water in the atmosphere to produce acid rain, like coal does.

Benefits of Nuclear PowerOf the other clean energy sources, such as wind

and solar power, nuclear power requires the least

amount of land and is much more reliable.

The largest drawback from

nuclear power is the large

amounts of radioactive

wastes generated.

A typical nuclear power

plant generates 20

metric tons of nuclear

waste each year.

Drawbacks of Nuclear Power

Structure Represents a Metric Ton

Drawbacks of Nuclear PowerThe half-life or Uranium is 4.5 billion years.

The means that of the 20 metric tons, after 4.5

billion years, 10 metric tons will still be left.

Half-life will be covered more in depth during the radioactive decay lesson

Drawbacks of Nuclear PowerA major question becomes where is all of that

radioactive waste going to be stored for such a long

period of time?

Nobody wants

the nuclear

wastes in their

backyard.

Storage of Nuclear WastesCurrently nuclear wastes are stored in steel-line,

concrete pools under about 20 feet of borated

water for 6 years, at the nuclear power plants.

The water keeps the

wastes cool as they

continue to go through

radioactive decay.

Nuclear Waste Storage in Pools

at Nuclear Power Plants

Storage of Nuclear WastesAfter 6 years, the nuclear waste is placed inside

steel canisters that are placed into reinforced

concrete containers, called dry casks.

The dry cask storage

allows the radioactive

wastes to cool off

naturally, while still

protecting the

environment.

Dry Cask Storage at

Nuclear Power Plants.

Periodically, there is talk

about storing all the wastes

underneath Yucca Mountain

in Nevada.

Yucca Mountain

But two-thirds of the people in Nevada oppose the site, mainly

because they don’t even have a nuclear power plant.

The What If? FactorThe United States rigorously maintains their nuclear

power plants and there has never been an actual

issue of nuclear contamination in the United States.

However, there is always the

possibility of nuclear

contamination occurring.

This is most common concern

of people who object to

nuclear power.

In 1986 in the Ukraine part of the Soviet Union, a nuclear reactor underwent a meltdown resulting in radioactive

related deaths, cancer and birth defects.

Chernobyl

But, the Soviet Union wasn’t maintaining the nuclear power plant and they didn’t even warm the people after the

meltdown occurred.

Chernobyl: What Really Happened

FukushimaIn 2011 in Fukushima, Japan, nuclear reactors also

underwent a meltdown after an earthquake and tsunami.

Over 160,000 people were forced to evacuate

their homes.

The End