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Physics > Nuclear Fission and Fusion > Flashcards

Nuclear Fission and Fusion Flashcards

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0
Q

Define binding energy per nucleon

A

The average energy required to remove a nucleon from the nucleus

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1
Q

What is binding energy?

A

The energy required to separate an atom into its component parts

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2
Q

What is activity (Bq)?

A

The number of nuclei of the isotope that disintegrate per second

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3
Q

What is alpha decay?

A

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

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4
Q

What is atomic mass unit?

A

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

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5
Q

What is atomic number?

A

The number of protons in the nucleus of an atom

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6
Q

What is the Avogadro constant?

A

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

6.02 x 10^23

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7
Q

What is background radiation?

A

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

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8
Q

What is beta-minus radiation?

A

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

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9
Q

What is beta-plus radiation?

A

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

Travels no more than 2mm before annihilated

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10
Q

What is binding energy per nucleon?

A

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

E per nucleon = E / mass number

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11
Q

What is a chain reaction?

A

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

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12
Q

What is a steady chain reaction?

A

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

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13
Q

What are control rods?

A

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

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14
Q

What is coolant?

A

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

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15
Q

What is count rate?

A

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

Count rates are corrected by measuring and subtracting the background radiation

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16
Q

What is critical mass?

A

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

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17
Q

What is the decay constant?

A

The probability of an individual nucleus decaying per second

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

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18
Q

What is a decay curve?

A

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

19
Q

What is a dose equivalent (Sv)?

A

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

20
Q

What is electron capture?

A

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)

21
Q

What is an excited state?

A

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

22
Q

What is fission?

A

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

23
Q

What is induced fission?

A

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

24
Q

What are fission neutrons?

A

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

25
Q

What is nuclear fusion?

A

The fusing of light nuclei to form a heavier nucleus

26
Q

What is gamma radiation?

A

Electromagnetic radiation emitted by an unstable nucleus when it becomes more stable

Gamma radiation is the least ionising, but the most penetrative

27
Q

What is ground state?

A

The lowest energy state of an atom (or electron)

28
Q

What is a half life?

A

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

29
Q

What is a heat exchanger?

A

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

30
Q

What is intensity of radiation (Wm-2)?

A

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

31
Q

What is ionising radiation?

A

Radiation that produces ions in the substances it passes through

Destroys cell membranes and damages DNA

32
Q

What is mass defect?

A

The difference between the mass of separated nucleons and the nucleus

33
Q

What Rutherford’s alpha-particle scattering experiment reveal?

A

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

34
Q

What is strong nuclear force?

A

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

35
Q

What is a thermal nuclear reactor?

A

Nuclear reactor which has a moderator in the core

36
Q

Define the alpha particle

A

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

37
Q

Define annihilation

A

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

38
Q

Define braking radiation

A

X-rays produced when electrons are decelerated

39
Q

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

A

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

40
Q

Why has so little anti-matter been created?

A

Needs a large amount of energy to produce anti matter.

41
Q

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

A

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

42
Q

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

A

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

43
Q

Explain the role of control rods in nuclear reactor

A

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

44
Q

Explain the role of fuel rods in a nuclear reactor

A

Fuel rods contain the uranium

45
Q

Explain the role of the moderator in a nuclear reactor

A

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

Physics (9 decks)

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