Topic 5.4: Fission Questions

Uranium-238 has a binding energy per nucleon of about 7.6 MeV.

What is its total binding energy?

Which property must the material of a control rod have?

The graph shows how the binding energy per nucleon varies with nucleon number.

On the graph, mark with an X the position of oxygen-16.

State what is meant by the mass defect of a nucleus.

A uranium-235 nucleus absorbs a neutron and splits:

²³⁵U + n → ¹⁴⁰Xe + ⁹⁴Sr + x n

What is x?

In which component do fast neutrons lose most of their kinetic energy, so that uranium-235 can capture them?

In a thermal fission reactor, what does the moderator do?

Suggest why splitting light nuclei, such as carbon-12, does not release energy.

The graph shows how the binding energy per nucleon varies with nucleon number.

On the graph, mark with an X the position of uranium-235.

A uranium-235 nucleus absorbs a slow neutron and splits into barium-141 and a krypton nucleus with proton number 36, releasing three neutrons.

State the nuclear equation, including the nucleon number of the krypton.

A uranium-235 nucleus absorbs a slow neutron and splits into xenon-140 (Z = 54) and strontium-94 (Z = 38).

State the nuclear equation for this fission.

A plutonium-239 nucleus absorbs a neutron and splits:

²³⁹Pu + n → ¹³⁶Xe + ¹⁰²Zr + x n

What is x?

Which part of a reactor makes fission of uranium-235 more likely by slowing the neutrons?

State what is meant by induced nuclear fission.

Sketch a graph of binding energy per nucleon (vertical axis) against nucleon number (horizontal axis) for naturally occurring nuclei.

On your sketch, mark the approximate position of the most stable nuclei.

Suggest why a star's core stops releasing energy by fusion once its core is iron.

Gold and uranium are found on Earth.

Suggest why they cannot have been produced by the fusion that powers an ordinary star's core.

The graph shows how the binding energy per nucleon varies with nucleon number.

On the graph, mark with an X the position of iron-56.

Neutrons carry no charge, yet they are held inside nuclei.

State the force responsible.

State the force that holds protons and neutrons together in a nucleus.