Nuclear Fission & Fusion Flashcards

All 23 cards in this deck

What is nuclear fission?

The splitting of a large and unstable nucleus into two smaller nuclei.

Name two nuclear fuels used in fission.

Uranium and plutonium.

In a fission reaction, what is emitted by the nucleus as it splits?

Two or three neutrons plus gamma rays.

True or false? Spontaneous fission of an unstable nucleus is common.

False. Spontaneous fission is rare — usually the unstable nucleus must first absorb a neutron.

What type of energy do all of the products of a fission reaction have?

Kinetic energy (they move apart), and energy is released by the reaction.

What are the steps in a nuclear fission event?

e.g. fission of a uranium nucleus in a reactor

1. A neutron is absorbed by the uranium nucleus, making it unstable.
2. The nucleus splits into two smaller nuclei, roughly equal in size, which have kinetic energy.
3. Two or three neutrons plus gamma rays are emitted and energy is released.

What is a chain reaction in nuclear fission?

Neutrons released by one fission are absorbed by other nuclei, causing further fissions that release more neutrons.

Which particles released by fission keep a chain reaction going?

Neutrons.

Why is the chain reaction controlled in a nuclear reactor?

To control the energy released.

What kind of chain reaction causes the explosion of a nuclear weapon?

An uncontrolled chain reaction.

True or false? The chain reaction inside a nuclear reactor is uncontrolled.

False. It is controlled in a reactor; only in a nuclear weapon is it uncontrolled.

What are the steps by which a chain reaction is set up?

e.g. in a reactor containing uranium

1. A uranium nucleus absorbs a neutron and undergoes fission.
2. Two or three neutrons are emitted.
3. These neutrons are absorbed by other uranium nuclei, causing further fissions.

On a diagram of a single fission event, how many neutrons should be shown leaving the splitting nucleus?

Two or three.

True or false? On a fission diagram the two product nuclei should be drawn as one large nucleus and one very small nucleus.

False. The two smaller nuclei are roughly equal in size.

How is the release of energy shown on a nuclear fission diagram?

By gamma rays (wavy arrows) leaving, and by the product nuclei and neutrons moving away with kinetic energy.

What are the steps to draw a diagram of one fission event?

e.g. a uranium nucleus absorbing a neutron

1. Draw a neutron with an arrow moving into the large uranium nucleus.
2. Draw two smaller nuclei of roughly equal size moving apart.
3. Draw two or three neutrons and gamma rays leaving.

What are the steps to draw a diagram showing a chain reaction?

e.g. starting with one neutron and uranium nuclei

1. Draw the first fission: neutron in, two smaller nuclei and two or three neutrons out.
2. Draw arrows taking those neutrons into further uranium nuclei.
3. Show each of those nuclei splitting and releasing more neutrons.

What is nuclear fusion?

The joining of two light nuclei to form a heavier nucleus.

What happens to the total mass of the particles during nuclear fusion?

It decreases — some of the mass is converted into the energy of radiation.

True or false? Nuclear fusion is the joining together of two atoms.

False. It is the joining together of two nuclei.

How do fission and fusion differ in the nuclei involved?

Fission: one large, unstable nucleus splits into two smaller nuclei. Fusion: two light nuclei join to form a heavier nucleus.

True or false? Both nuclear fission and nuclear fusion release energy.

True. Both processes release energy, though by different changes to the nuclei.

True or false? In nuclear fusion a nucleus must first absorb a neutron.

False. Neutron absorption starts fission; fusion needs two light nuclei to join.