Nuclear physics: Nuclear Reactors

Question 1

What is the role of fuel rods in a nuclear reactor?

Answer 1

Site of nuclear fission reactions, made of Uranium

Fuel rods contain a higher percentage of U235, which undergoes fission more easily.

Question 2

What are the two main isotopes of natural Uranium?

Answer 2

• U238 (99.28%)
• U235 (0.72%)

U238 requires high-energy neutrons for fission, while U235 undergoes fission more easily.

Question 3

What is the purpose of a moderator in a nuclear reactor?

Answer 3

Slows down neutrons to enable fission

Typical materials include graphite and water.

Question 4

True or false: The neutrons released from nuclear fission travel at 1 x 10^7 m/s.

Answer 4

TRUE

They must be slowed to about 2 x 10^3 m/s to cause further fission.

Question 5

What are thermal neutrons?

Answer 5

Neutrons with kinetic energy similar to moderator atoms (about 0.025 eV at 20°C)

They are slow enough to cause fission.

Question 6

What is the role of coolant in a nuclear reactor?

Answer 6

Carries heat from the moderator to the heat exchanger

Typical materials include carbon dioxide and water.

Question 7

List the factors affecting the choice of materials for coolant.

Answer 7

• Must carry large amounts of heat
• Must be gas or liquid
• Non-corrosive
• Non-flammable
• Poor neutron absorber

These properties help maintain reactor safety and efficiency.

Question 8

What is the function of control rods in a nuclear reactor?

Answer 8

Absorb neutrons to regulate fission reactions

They help maintain a constant power output by controlling the number of fission reactions.

Question 9

Fill in the blank: The coolant moves hot coolant to the _______ to exchange heat.

Answer 9

heat exchanger

This process turns cold water into steam, which can then turn a turbine.

Question 10

What is the significance of enriched Uranium in fuel rods?

Answer 10

Higher percentage of U235 allows more fission reactions

Enrichment increases the efficiency of the nuclear reaction.

Question 11

What happens to the neutrons that leave the reactor without interacting?

Answer 11

They do not contribute to further fission

Some neutrons travel too fast or are absorbed by U238 nuclei.