7.3 Nuclear Reactions

By: HULKAnd Bruce Banner

Nuclear Fission

• Generate power from nuclear fission• Split heavy nucleus into 2 lighter nuclei,

subatomic particles and energy• Large amount of energy released which

generate electrical power in nuclear reactor• No more coal and natural gas• Produce radioactive waste that must be

stored safely for long time or more Bruce Banners become HULK

Nuclear Reactions• In nuclear reactions, the nuclei of

atoms change• Protons, neutrons, electrons or

gamma rays can be released (stay away from gamma rays)

• Unlike chemical reactions, in nuclear reactions, mass can be converted into energy• Small changes in mass result in

large changes in energy (E = mc2 where c = the speed of light)

Induced Nuclear Reactions

• Nuclear reactions don’t only happen naturally through radioactive decay

• When HULK SMASH nucleus with alpha particles, beta particles, gamma rays or neutrons HULK induce nuclear reaction

Subatomic Particle Symbols

• Here are is the standard atomic notation for some subatomic particles:

• Proton = Hydrogen-1 nucleus = • Neutron = • Electron = Beta Particle = • Alpha particle = Helium nucleus =

Rules for Writing Nuclear Equations

• Sum of mass numbers on each side are equal

• Sum of charges (atomic numbers) on each side are equal:

Nuclear Fission of Uranium-235

• The main reaction in fission nuclear weapons and in Canadian nuclear power plants

• It has the following nuclear equation

• The uranium-235 nucleus absorbs a neutron briefly becoming uranium-236 which is unstable so it decays into two smaller nuclei releasing 3 neutrons and energy

Chain Reactions• Uranium-235 fission release 3 neutrons

which can go start other fission reactions which release more neutrons to start more reactions and so on.

• This process where one reaction starts next, called chain reaction

• Chain reactions in nuclear reactor must be controlled (like Bruce Banner anger) or risk of releasing radiation or explosions

• Enrico Fermi used cadmium rods to absorb neutrons in first reactor and control chain reaction

CANDU Reactors

• CANDU stands for CANadian Deuterium Uranium

• Deuterium is an isotope of hydrogen with a proton and neutron in nucleus

• CANDU reactors use uranium fission to create heat which boils water, generating steam which turns turbines to produce electricity

Hazardous Wastes

• CANDU reactor fuel is bundles of rods with uranium pellets

• Each used for 15 months• Used ones very radioactive

– Stored in water pools for 10 years– Then transferred to shielded

storage containers so scientists don’t become like HULK

Nuclear Fusion

• HULK SMASH two light nuclei to form one heavy nucleus

• Happens at core of sun where hydrogen-2 and hydrogen-3 SMASH and form helium

• Need high pressure and temperature• Release massive amounts of energy

– Fusion in sun create light and heat in human world

Fusion vs. Fission

• Light nuclei SMASH to form heavy nucleus

• Release lots of energy if created nucleus as light or lighter than iron

• Products not radioactive a I

• Cannot yet be used to generate electrical power

• Use in nuclear weapons if enough heat and pressure from fission reaction a I a I a

• Heavy nuclei split apart a I a

• Releases lots of energy if the parent is heavier than iron

• Daughter isotopes are often radioactive

• Used to generate electrical power

• Used in nuclear weapons itself or to generate the heat and pressure for a fusion reaction

Video

http://www.youtube.com/watch?v=FU6y1XIADdg

Quiz1. What is the standard atomic notation for a proton?

2. What is the major difference between a chemical and nuclear reaction?

3. What do you call a nuclear reaction caused by bombarding a nucleus with

subatomic particles?

4. What is a chain reaction?

5. What do CANDU reactors use as fuel?

6. What happens to used CANDU reactor fuel bundles?

7. Fission or Fusion

a) Used for electrical power generation

b) Joining of two lighter nuclei

c) Occurs in our sun

d) Often creates radioactive products

e)

Answers

1.

2. In nuclear reactions, nuclei change, in chemical reactions, changes only

occur in the electron shells

3. Induced Nuclear Reaction

4. An ongoing process in which one fission reaction initiates the next reaction

5. Uranium (bundles of rods with uranium pellets)

6. They are stored in water pools for 10 years then transferred to shielded

storage containers

7. a) Fission

b) Fusion

c) Fusion

d) Fission

e) Fission