Chemistry Nuclear Fission/Fusion 12.02

What substances are used a nuclear moderators in a nuclear reactor?

• liquid sodium and water

• plutonium and neptunium

• cadmium or other metal

• carbon and water

Which of the following processes produces nuclei of lower mass than the reactants?

• fusion

• fission

• both a and b

• neither a nor b

The process that changes the identity and number of protons in a nucleus is

• transmutation.

• fission.

• fusion.

• all of the above.

In reactors, the role of the moderator is to

• slow down neutrons.

• absorb energy.

• absorb neutrons.

• accelerate neutrons.

Which of the following statements is correct?

• The product of nuclear reactions is safe because the radioisotope is used up.

• Water can be used to slow down neutrons in a nuclear reactor.

• Carbon control rods absorb neutrons in a nuclear fission reaction.

• Energy must be added to a nuclear reactor to initiate a chain reaction.

What does neutron absorption accomplish in a nuclear reactor?

• It increases the rate of heat absorption.

• It recycles the fuel.

• It speeds up the reaction.

• It slows down the reaction.

What device uses controlled nuclear fission to produce new radioactive substances and energy?

• synchrotron

• nuclear reactor

• linear acclerator

• nuclear bomb

Which statement about nuclear reactions is not true?

• In fission, the total mass of the reactants equals the total mass of the products.

• Heat and light in the sun are produced by hydrogen fusion reactions.

• In fission, nuclei are split and in fusion, nuclei are combined.

• Nuclear power plants use fission of uranium.

How long do spent fuel rods remain dangerously radioactive?

• Spend fuel rods remain radioactive for several years after the fuel is exhausted.

• It takes tens of thousands of years for the radioisotopes in the rods to decay to safe levels.

• It is impossible to determine how long it will take for the radioisotopes to decay because they last too long.

• The rods are no longer radioactive because the radioisotopes are used up.

If the particle that starts a nuclear reaction is also one of the products, the process is a

• nuclear fusion.

• chain reaction.

• neutron bombardment.

• neutron emission.