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Physics > Nuclear Radiation > Flashcards

Nuclear Radiation Flashcards

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1
Q

Why are beta and gamma used as medical tracers

A

They can penetrate the skin and other body tissues

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2
Q

What happens to a tracer

A

It penetrates the body tissues and can be detected externally to monitor its progress

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3
Q

What does the radioactive source in a tracer need to have

A

A short half-life so that you can use less of the radioactive source, but still detect it

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4
Q

Why are alpha particles not useful for medical tracers

A

They would be stopped by the body’s tissues

They are very ionising which is dangerous

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5
Q

what does the nucleus contain?

A

protons and neutrons

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6
Q

what is the atomic number?

A

the number of protons in the nucleus

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7
Q

what is the mass number?

A

the total number of protons and neutrons in the nucleus

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8
Q

what are isotopes?

A

atoms with different numbers of neutrons but the same number of protons

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9
Q

what are the common isotopes?

A

carbon-14 and carbon -12

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10
Q

what kind of process is radioactive decay?

A

random, it is not affected by conditions such as temperature

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11
Q

where does background radiation come from?

A
  • Earth
  • space
  • living things
  • human activity (eg. nuclear waste)
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12
Q

how is ionisation caused?

A

-nuclear radiation bashes into atoms and knocks electrons off them

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13
Q

what is the pattern for ionisation?

A

the further along the radiation can penetrate before hitting an atom and getting stopped, the less damage it will do along the way

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14
Q

how can ionising radiation be detected?

A

with photographic film or a Geiger-Muller detector

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15
Q

what are alpha particles made up of?

A
  • 2 protons and 2 neutrons
  • they are big and slow moving
  • they are strongly ionising
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16
Q

alpha particles are stopped…

A

quickly

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17
Q

alpha particles are…

A

deflected by electric and magnetic fields

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18
Q

what happens to the atomic number when an alpha particle is emitted from the nucleus?

A

it decreases by 2

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19
Q

what happens to the mass number when an alpha particle is emitted from the nucleus?

A

it decreases by 4

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20
Q

what is a beta particle?

A

an electron

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21
Q

how is a beta particle formed?

A

a neutron turns into a proton and an electron

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22
Q

what happens to the atomic number when a beta particle is emitted?

A

it increases by 1

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23
Q

what happens to the mass number when a beta particle is emitted?

A

it stays the same

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24
Q

beta particles are…

A

moderately penetrating and moderately ionising

25
Q

beta particles are…(2)

A

deflected by electric and magnetic fields

26
Q

what are gamma rays?

A
  • very short wavelength electromagnetic spectrum waves
  • they have no mass
  • they are energy
27
Q

gamma rays are…

A
  • weakly ionising
  • they have no charge
  • they are always emitted after an alpha or beta particle has been emitted
  • they are not deflected by electric or magnetic fields
28
Q

what are alpha particles blocked by?

A
  • paper
  • skin
  • a few cm of air
29
Q

what are beta particles blocked by?

A

-thin metal (eg aluminium)

30
Q

what are gamma rays blocked by?

A
  • thin lead

- very thick concrete

31
Q

half-life definition

A

the time taken for half of the radioactive atoms now present to decay

32
Q

half-life definition 2

A

the time taken for the activity (or count rate) to fall by half

33
Q

what is radioactivity measured in?

A

becquerels

34
Q

what is radioactivity measured in?

A

becquerels

35
Q

what are gamma rays used for?

A

industrial tracers

36
Q

how do industrial tracers work?

A
  • squirt the gamma rays into the pipe
  • go along the outside with a detector
  • if there is a crack in the pipe, the detector will show extra-high radiation at that point
37
Q

why cant alpha and beta particles be used for industrial tracers?

A

they would be too easily blocked

38
Q

what do you need to know to work out the age of a sample?

A
  • the amount of radioactive isotope left in the sample

- the half-life of the sample

39
Q

what does uranium eventually decay to become?

A

lead

40
Q

a clue to a rock’s age is…

A

the relative proportions of uranium and lead isotopes

41
Q

how to calculate how old something is using carbon-14

A
  • compare the activity of a sample to living tissue

- this lets you estimate how many half-lives have passed

42
Q

is alpha radiation dangerous?

A

yes, once it gets inside the body

43
Q

why is alpha radiation dangerous?

A
  • it collides with molecules in your cells
  • these collisions cause ionisation
  • lower dosages can cause mutations in cells, which causes them to divide uncontrollably. This can cause cancer
  • higher doses tend to kill cells completely, which causes radiation sickness.
44
Q

how is radiation used to treat cancer?

A
  • using radiotherapy
  • this involves a high dose of gamma rays, carefully directed at the tumour, while minimising the damage to the rest of the body
45
Q

how can you protect yourself from radioactive materials?

A
  • avoid skin contact
  • keep the source pointed away from the body and avoid looking at it
  • store radioactive sources in a sealed lead box whenever they’re not being used
46
Q

what do people regularly working with radioactivity need to do?

A
  • wear lead aprons
  • stand behind lead screens during procedures
  • wear full protective suits
  • use remote controlled robot arms
  • avoid inhaling/touching the radioactive samples
47
Q

what do people regularly working with radioactivity need to do?

A
  • wear lead aprons
  • stand behind lead screens during procedures
  • wear full protective suits
  • use remote controlled robot arms
  • avoid inhaling/touching the radioactive samples
48
Q

nuclear fission

A

the splitting of an atom, which releases energy

49
Q

the fuel that is split up in a nuclear reactor

A

uranium-235

50
Q

what is the ‘fuel’ that is split up in a nuclear reactor?

A

uranium-235

51
Q

what happens when a uranium-235 nucleus splits up?

A

it spits out a number of neutrons

52
Q

what does uranium-235 make when it splits in two?

A

two new daughter nuclei

53
Q

what are the daughter nuclei?

A
  • they are lighter than uranium
  • they are radioactive because they have the ‘wrong’ number of neutrons in them
  • this produces huge amounts of radioactive waste
54
Q

what does a moderator do?

A

it slows down neutrons so that theu can successfully collide with uranium nuclei and sustain the chain reaction

55
Q

what are control rods often made of?

A

boron

56
Q

what do control rods do?

A

they limit the rate of fission by absorbing excess neutrons

57
Q

how is the heat from the reactor carried away?

A

a gas, typically carbon dioxide, is pumped through the reactor

58
Q

what does the gas do after it has carried away the heat from the reactor?

A
  • it is passed through a heat exchanger, where it gives its energy to water
  • this water is heated and turned into steam, which turns a turbine, which turns a generator, which produces electricity

Physics (10 decks)

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