7.3 – Nuclear Reactions
Nuclear Fission
Nuclear _____________ is the splitting of a more massive nucleus into two less massive nuclei,
subatomic particles, and energy. Heavy ______________ tend to be unstable because of the repulsive
forces between all the _____________. When nuclei break apart, there is a large release of
_____________. We can use this energy to help supply electricity.
Nuclear reactors do help reduce the need for fossil fuels such as __________ or __________________,
but they do produce radioactive waste that needs to be stored properly for a long time. There is also a
concern that nuclear material could be used for making _______________________.
Nuclear Reactions
A nuclear reaction is a process in which an atom’s ____________ changes by gaining or releasing
______________ or _____________. A nuclear reaction can release one, two, or all three types of
subatomic particles, as well as gamma rays. However, in nuclear reactions, a small change in mass results
in a large release of energy.
Nuclear Equations for Induced Nuclear Reactions
There are other types of nuclear reactions besides _____________ decay (alpha, beta and gamma
radiation) we have learned about. Scientists are able to make a nucleus ________ so that it will undergo a
nuclear reaction immediately. This is called an ____________, or forced, nuclear reaction. A reaction is
induced by __________________ a nucleus with alpha or beta particles, or gamma rays.
When a nitrogen-14 nucleus is bombarded with an alpha particle, a fluorine-18 nucleus is produced, which then decays into
oxygen-17 and a proton.
Subatomic particles can be written in the following ways:

A proton (hydrogen nucleus) can be written as _______ or _______.

An electron (beta particle) can be written as _______ or _______.

A helium nucleus (alpha particle) can be written as _______ or _______.

A neutron can be written as _______.
Nuclear Fission of Uranium-235
One kind of _____________ that can happen is a _____________ colliding with a nucleus. The nuclear
fission of uranium-235 is the main nuclear reaction in both fission-style nuclear weapons and in Canadian
nuclear power plants. The equation for the fission of uranium-235 is:
1
0n
+ 23592U → 9236Kr + 14156Ba + 310n + energy
When the neutron hits U-235, it produces the very unstable U-236, which immediately decays into two
smaller nuclei, releasing several _____________ and a lot of energy. These neutrons that are released can
trigger even more nuclear reactions in nearby atoms.
The ongoing process in which one reaction initiates the next reaction is called a ____________________.
The number of fissions and the amount of energy released can lead to a violent nuclear explosion.
A Nuclear Chain Reaction…
Keeping the chain reaction going in a nuclear power plant, while not allowing it to get out of control,
requires precise monitoring. Much of the concern about nuclear power plants focuses on the harm that
could be caused by losing control of the nuclear reactions taking place inside the reactor.
CANDU Reactors
Canadian nuclear reactors are called ______________ reactors, which stands for CANadian Deuterium
Uranium reactor. _________________ is an isotope of hydrogen that is twice as heavy, as it has both a
proton and a neutron in its nucleus. The design of CANDU is among the safest in the world, as it can be
shut down immediately if there is a problem. Nuclear power plants and fossil-fuel burning plants are
similar in that they both produce a lot of __________. The heat is used to __________________, which
is in turn used to run a _______________ that produces electricity.
Hazardous Wastes
The fuel used to produce heat in a CANDU reactor is in the form of bundles of rods containing
________________________. Each nuclear fuel bundle stays in the reactor for about ______ months.
Used fuel bundles are highly radioactive when they are removed from the reactor, so they are stored in
___________ pools for about ______ years before they can be transferred to shielded, above-ground dry
storage bunkers.
The bundles remain hazardous for thousands of years, and must be kept separate from the natural
environment. Most countries with nuclear programs, including Canada, plan to store the hazardous
wastes far underground. Some countries have plans to reprocess the waste to recover useful substances.
Nuclear Fusion
_____________ is the process in which two low-mass nuclei join together to produce a more massive
nucleus. This is the type of reaction the _______ and other stars do. There must be sufficient heat and
pressure to get this type of reaction to happen. A huge amount of ____________ is released when fusion
reactions take place.