Topic 11: Nuclear Radiation

Question 1

Activity

Answer 1

The activity of a radioactive source is the number of nuclei that decay per second, measured in Becquerels (Bq)

Question 2

Alpha radiation

Answer 2

The radiation of a particle containing two protons and two neutrons. It is strongly ionising, slow moving, and positively charged so therefore deflected by a magnetic field

Question 3

Atomic mass unit

Answer 3

1/12 the mass of a carbon-12 nuclei

Question 4

Background radiation

Answer 4

Constant radiation everywhere that is due to radioactive substances in the environment

Question 5

Beta-minus radiation

Answer 5

Radiation consisting of a high-energy electron that is mildly ionising, fast-moving, and negatively charged so therefore deflected by a magnetic field

Question 6

Beta-plus radiation

Answer 6

Radiation consisting of a high-energy positron that is mildly ionising, fast-moving, and positively charged so therefore deflected by a magnetic field in the opposite direction to beta-minus radiation

Question 7

Binding energy

Answer 7

The energy required to split a nucleus into its individual nucleons. The greater the binding energy per nucleon, the more stable the nucleus is

Question 8

Chain reaction

Answer 8

When the fission of one nucleus produces neutrons that cause fission in another nuclei

Question 9

Control rod

Answer 9

A rod that is inserted into a reaction vessel that stops neutrons preventing them from continuing on to cause more fission reactions. These are made from substances that absorb neutrons without fissioning themselves

Question 10

Coolant

Answer 10

A fluid that passes around the reaction vessel and carries away any thermal energy produced by the fission reactions. This thermal energy is used to generate steam and drive generators to produce electricity

Question 11

Cooling pond

Answer 11

A large pool of water that nuclear waste is placed in to allow it to cool to safe temperatures

Question 12

Critical mass

Answer 12

The minimum amount of a fissile substance needed to maintain a chain reaction and a steady flow of fission

Question 13

Decay constant

Answer 13

The probability of a decay occurring per unit time

Question 14

Fuel rod

Answer 14

Contains the fissile material, each rod has many pellets of nuclear fuel which prevents the critical mass of fuel being reaching meaning the reactions are controlled

Question 15

Gamma radiation

Answer 15

High energy photons, it is weakly ionising, travels at the speed of light and has no charge so is not deflected by magnetic or electric fields

Question 16

Half-life

Answer 16

The time taken for half of the radioactive nuclei to decay

Question 17

Moderator

Answer 17

A substance inserted between the nuclear fuel that reduces the speed of neutrons coming from a fission reaction, allowing them to become thermal neutrons that can induce further fission

Question 18

Nuclear fission

Answer 18

The splitting of a large nucleus to produce smaller nuclei, fast-moving neutrons and energy

Question 19

Nuclear fusion

Answer 19

The fusing of two smaller nuclei to form a single nucleus producing a large quantity of energy. Very high temperatures and pressures are needed as well as high magnetic fields to contain the fusing plasma

Question 20

Nuclear waste

Answer 20

The by-product of a nuclear reaction. This waste is no longer undergoing fission that can be used due to the reduced activity, but the waste is still radioactive and will be for thousands of years, so it is stored underground in reinforced containers

Question 21

Mass defect

Answer 21

The difference between the mass of the nuclei and its individual components. If this mass defect is large and positive, then when a nucleus undergoes fission this mass defect is released as energy. If this mass defect is negative, then when two nuclei are fused together, this mass defect is released as energy

Question 22

Spontaneous fission

Answer 22

The process by which a nucleus splits without absorbing a thermal neutron

Question 23

Thermal neutron

Answer 23

A slow-moving neutron that when absorbed by an unstable nucleus causes it to undergo fission