Nuclear Fission and Fusion

Question 0

Define binding energy per nucleon

Answer 0

The average energy required to remove a nucleon from the nucleus

Question 1

What is binding energy?

Answer 1

The energy required to separate an atom into its component parts

Question 2

What is activity (Bq)?

Answer 2

The number of nuclei of the isotope that disintegrate per second

Question 3

What is alpha decay?

Answer 3

Change in an unstable nucleus when it emits an alpha particle, consisting of 2 protons and 2 neutrons.

It is absorbs by paper, and has a range of a few centimetres and is the most ionising

Question 4

What is atomic mass unit?

Answer 4

The unified atomic mass constant, 1/12th of the mass of an atom of carbon-12, equal to 1.667 x 10^-27kg

Question 5

What is atomic number?

Answer 5

The number of protons in the nucleus of an atom

Question 6

What is the Avogadro constant?

Answer 6

The number of atoms in 12g of Carbon-12, used to define the mole.

6.02 x 10^23

Question 7

What is background radiation?

Answer 7

Radiation due to naturally occurring radioactive substances in the environment and cosmic radiation

Question 8

What is beta-minus radiation?

Answer 8

B- emitted (and an antineutrino) by an unstable neutron-rich nucleus.

It is easily absorbed by aluminium, has a range of a few centimetres, and less ionising that alpha radiation, but more than gamma

Question 9

What is beta-plus radiation?

Answer 9

B+ (and neutrino) emitted by an unstable proton-rich nucleus

Travels no more than 2mm before annihilated

Question 10

What is binding energy per nucleon?

Answer 10

The average work done per nucleon to separate a nucleon into its constituent parts

E per nucleon = E / mass number

Question 11

What is a chain reaction?

Answer 11

A series of reactions in which each reaction causes a further reaction

In an nuclear reactor, each fission event issue to a neutron colliding with a U nucleus, which splits and releases 2-3 further neutrons

Question 12

What is a steady chain reaction?

Answer 12

One neutron on average from each fission event causes a further fission event

Question 13

What are control rods?

Answer 13

Rounds made from a neutron absorbing substance (Cadmium) that are moved in or out of the core of a nuclear reactor to control the rate of nuclear fission events

Question 14

What is coolant?

Answer 14

A fluid that is used to prevent a machine from overheating

In a nuclear reactor, the coolant is pumped through the core to transfer thermal energy to a heat exchanger

Question 15

What is count rate?

Answer 15

The number of counts per unit time detected by a Geiger Muller tube

Count rates are corrected by measuring and subtracting the background radiation

Question 16

What is critical mass?

Answer 16

The minimum mass of the fissile isotope in a nuclear reactor necessary to produce a chain reaction

Question 17

What is the decay constant?

Answer 17

The probability of an individual nucleus decaying per second

The constant for an isotope that appears in the equation
A = lambda x N.

Question 18

What is a decay curve?

Answer 18

An exponential decrease curve showing how the mass or activity of a radioactive isotope decreases with time

Question 19

What is a dose equivalent (Sv)?

Answer 19

The energy that would need to be absorbed per unit mass of matter

Question 20

What is electron capture?

Answer 20

A proton rich nucleus captures an inner shell electron, to change it into a neutron (neutrino emitted, and X-ray photon emitted when inner shell full)

Question 21

What is an excited state?

Answer 21

An atom (or electron) not in it’s ground state

Question 22

What is fission?

Answer 22

The splitting of a U or Pu nucleus into approximately equal fragments

Question 23

What is induced fission?

Answer 23

Fission caused by an incoming neutron colliding with a U or Pu nucleus

Question 24

What are fission neutrons?

Answer 24

Neutrons released when a nucleus undergoes fission and which may collide with nuclei to cause further fission

Question 25

What is nuclear fusion?

Answer 25

The fusing of light nuclei to form a heavier nucleus

Question 26

What is gamma radiation?

Answer 26

Electromagnetic radiation emitted by an unstable nucleus when it becomes more stable Gamma radiation is the least ionising, but the most penetrative

Question 27

What is ground state?

Answer 27

The lowest energy state of an atom (or electron)

Question 28

What is a half life?

Answer 28

The time taken for the mass of a radioactive isotope to halve the initial mass or for its activity to halve — time taken for the number of nuclei to halve

Question 29

What is a heat exchanger?

Answer 29

Hot coolant is pumped through this to cause water to turn into steam to drive turbines

Question 30

What is intensity of radiation (Wm-2)?

Answer 30

The radiation energy per second per unit area at normal incidence to the surface

Question 31

What is ionising radiation?

Answer 31

Radiation that produces ions in the substances it passes through Destroys cell membranes and damages DNA

Question 32

What is mass defect?

Answer 32

The difference between the mass of separated nucleons and the nucleus

Question 33

What Rutherford's alpha-particle scattering experiment reveal?

Answer 33

It demonstrated every atom contains a positively charges nucleus which is much smaller than the atom

Question 34

What is strong nuclear force?

Answer 34

Force that holds the nucleons together. Range of 2-3fm, and below 0.5fm, it is repulsive

Question 35

What is a thermal nuclear reactor?

Answer 35

Nuclear reactor which has a moderator in the core

Question 36

Define the alpha particle

Answer 36

A particle comprising of two protons and two neutrons ejected from the nucleus during radioactive decay

Question 37

Define annihilation

Answer 37

The process when a particle and antiparticle interact and their combined mass is converted to energy via E = mc^2

Question 38

Define braking radiation

Answer 38

X-rays produced when electrons are decelerated

Question 39

Why is it difficult to contain anti-hydrogen atoms, compared to anti-protons?

Answer 39

Atoms are not charged- magnetic/ electric fields have no effect.

Question 40

Why has so little anti-matter been created?

Answer 40

Needs a large amount of energy to produce anti matter.

Question 41

What happens to a capacitor when a switch is closed completing a circuit with it, a resistor and a cell?

Answer 41

The capacitor charges up gathering negative charges on one plate, repelling the negative charges on the othe plate giving that plate a positive charge. This happens over a period of time. Eventually all charges are stored n the capacitor

Question 42

How do neutral particles appear in an image taken from a bubble chamber?

Answer 42

No tracks, ot visible at all until it decays (decays into charged particles).

Question 43

Explain the role of control rods in nuclear reactor

Answer 43

Control rods absorb some of the neutrons The control rods are inserted into the reactor so as to allow, on average, one neutron from the previous reaction to cause subsequent fission

Question 44

Explain the role of fuel rods in a nuclear reactor

Answer 44

Fuel rods contain the uranium

Question 45

Explain the role of the moderator in a nuclear reactor

Answer 45

The moderator slows down fast moving neutrons and therefore lowers their KE Slow moving neutrons have a greater chance of causing fission and sustaining a chain reaction