Download 1.6--NOTES--Detecting Radiation Nuclear Rxtns

2.3: Detecting
Radioactivity,
Nuclear Reactions
2/1/17
SPS3. Students will distinguish the characteristics and components of radioactivity.
a. Differentiate among alpha and beta particles and gamma radiation. b. Differentiate between
fission and fusion. c. Explain the process half-life as related to radioactive decay. d. Describe
nuclear energy, its practical application as an alternative energy source, and its potential problems.
Part I: Detecting Radioactivity
• because you can’t see or feel radiation (alpha or beta particles or
gamma rays), you must use special instruments to detect them.
• each of these tools detects the ions produced by the radioactive
particles as they collide with matter, not the radiation itself.
• cloud chamber = a small glass box full of
tiny droplets of water vapor (like fog).
•A radioactive source placed inside
the box will produce ions in the
air as the isotopes knock electrons
off the air molecules.
•Water condenses around these ions,
forming trails of droplets that
indicate radioactivity.
• cloud chamber = a small glass box full of
tiny droplets of water vapor (like fog).
•A radioactive source placed inside
the box will produce ions in the
air as the isotopes knock electrons
off the air molecules.
•Water condenses around these ions,
forming trails of droplets that
indicate radioactivity.
•alpha particles leave a short, thick
https://www.youtube.com/watch?
trail in a cloud chamber
v=e3fi6uyyrEs cloud chamber
•beta particles leave a long, thin trail
• bubble chamber = similar to the cloud chamber, only filled with
superheated liquid instead. Ions cause small bubbles to form in the
liquid as it boils, leaving trails of bubbles behind.
• bubble chamber = similar to the cloud chamber, only filled with
https://www.youtube.com/watch?v=gNgHl2FkswE Geiger
superheated liquid instead. Ions cause small bubbles to form in
https://www.youtube.com/watch?v=mbNGbJ60hoA
sound
the liquid
as it boils, leaving trails of bubbles behind.
•Geiger counter = a device the size of a microphone filled with gas
and connected to a meter. Ions stripped from the gas are picked
up by a wire, converted to electrical current, and then converted
to audible clicks. The speed at which the counter clicks indicates
the amount of
radiation present.
In the cloud chamber video,
what was the material that
looked like white tubes
placed under the chamber?
dry ice Why was it there?
_______
to cool down the vapor
(so you can see the trails)
Describe what a Geiger
counter sounds like:
a series of audible clicks
(more clicks =
more radiation present)
• bubble chamber = similar to the cloud chamber, only filled with
superheated liquid instead. Ions cause small bubbles to form in
the liquid as it boils, leaving trails of bubbles behind.
•Geiger counter = a device the size of a microphone filled with gas
and connected to a meter. Ions stripped from the gas are picked
up by a wire, converted to electrical current, and then converted
to audible clicks. The speed at which the counter clicks indicates
the amount of
radiation present.
Part II: Sources of Radiation
• background radiation = low-level
radiation emitted by naturally occurring
isotopes in the rocks, soil, water, and the
atmosphere, as well as building materials
(bricks, concrete, wood).
•as a result, all plants and animals
contain some small amounts of these
isotopes (such as 14C).
• largest source of background rad. is
radon gas (Rn):
•comes from the natural decay of 238U in Earth’s crust
•Rn itself emits alpha particles as it decays
•Rn seeps into houses through basement walls in contact with
soil
•Rn seeps into houses through
basement walls in contact with soil
• cosmic rays produce radioactive isotopes
when they hit molecules in the upper
levels of the atmosphere. Lower levels
absorb most of this radiation.
• exposure to background rad. varies with
a person’s location, the materials their
house is constructed from, and the
altitude at which they live.
What is the largest
source of background
radiation for most
people?
radon gas (Rn)
What protects us from
most radiation from
cosmic rays?
the atmosphere
•Rn seeps into houses through
basement walls in contact with soil
• cosmic rays produce radioactive isotopes
when they hit molecules in the upper
levels of the atmosphere. Lower levels
absorb most of this radiation.
• exposure to background rad. varies with
a person’s location, the materials their
house is constructed from, and the
altitude at which they live.
Part III: Nuclear Reactions
• there are two basic types of nuclear reactions: fission and fusion.
• fission = the process of splitting a nucleus into several smaller
nuclei.
Part III: Nuclear Reactions
https://www.youtube.com/watch?v=1
U6Nzcv9Vws
nuclear
reactor
• there are two basic types of nuclear
reactions:inside
fission
and fusion.
• fission = the process
of splitting a nucleus
into several smaller
nuclei.
• when a neutron is
fired at a 235U nucleus,
it absorbs the neutron,
becomes unstable,
and splits, producing 2 new nuclei and several more neutrons in the
process, as well as a tremendous amount of energy.
• the energy produced comes from a slight loss of mass during the
reaction.
• the mass is converted to energy through Einstein’s famous
equation:
• the mass is converted to energy through Einstein’s famous
equation:
E = mc2
•E = energy (measured in joules)
•m = mass (measured in kilograms)
•c = the speed of light
(3.0 x 108 m/s)
•100 trillion joules of
energy can be
produced from 1 gram
of mass!
• the neutrons released in
a fission reaction can
trigger chain reactions.
• chain reaction = series of repeated fission reactions caused by the
release of neutrons in each reaction.
•uncontrolled chain
reactions can be very
destructive, releasing
enormous amounts of
energy in an instant.
•controlled chain
reactions use materials
to
absorb the extra
neutrons so that the
reaction takes place at
a constant rate.
•critical mass = amount of material required so that each fission
reaction produces approx. 1 more fission reaction.
•critical mass = amount of material required so that each fission
reaction produces approx. 1 more fission reaction.
•fusion = nuclear reaction
involving 2 nuclei with low
masses combining to form
one nucleus of larger mass.
•fusion can only take place
at extremely high temperatures (millions of C),
since the particles must be
moving extremely fast to be able to react.
•temps like this can be found in the center of stars, such as our
Sun.
•fusion can only take place
at extremely high temperatures (millions of C),
since the particles must be
moving extremely fast to
be able to react.
•temps like this can be
found in the center of stars,
such as our Sun.
•fusion reactors have not yet been built yet on Earth.
•fusion reactions also release a tremendous amount of energy
(E = mc2).
https://www.youtube.com/watch?v=
W1ZQ4JBv3-Y fusion in the sun
https://www.youtube.com/watch?v=t7FvxN_gkt4
Nuclear energy basics, issues
The nuclear reaction that
splits large nuclei into 2
smaller nuclei is
(fission, fusion).
(Controlled, Uncontrolled)
nuclear reactions take
place in nuclear reactors in
power plants.
Metaphor for a chain
reaction:
spreading secrets (your
friend tells 2 people, they
each tell 2 people, etc.)
•fusion can only take place
at extremely high temperatures (millions of C),
since the particles must be
moving extremely fast to
be able to react.
•temps like this can be
found in the center of stars,
such as our Sun.
•fusion reactors have not yet been built yet on Earth.
•fusion reactions also release a tremendous amount of energy
(E = mc2).
https://www.youtube.com/watch?v=
W1ZQ4JBv3-Y fusion in the sun
https://www.youtube.com/watch?v=t7FvxN_gkt4
Nuclear energy basics, issues