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🌌 > P6.2 > Flashcards

P6.2 Flashcards

1
Q

Give examples of background radiation:

A
  • radon gas
  • artificial sources - medical uses
  • ground and building
  • food and drink
  • cosmic rays
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2
Q

How does ionising radiation harm living cells and how does it differ with different amounts of radiation?

A
  • some materials = absorb ionising radiation = enters living cells and interacts with molecules
  • molecules ionise to produce charge particles (ions)
  • lower doses of ionising radiation = damage living cells by causing mutations in the DNA = cells did ice uncontrollably = cancer
  • higher doses = kill cells completely = radiation sickness
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3
Q

What effects which radiation is the most dangerous?

A

Depends on where it is

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4
Q

What radiation is the most dangerous outside the body and why?

A
  • beta, gamma

- as they can still get inside to the delicate organs as they can pass through skin

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5
Q

What radiation is the most dangerous inside the body

A
  • alpha source
  • most ionising as they do all their damage in a very localised area
  • beta and gamma are less dangerous as less ionising and gamma will pass straight out without doing much damage
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6
Q

What does irradiation occur?

A
  • occurs when radioactive material is outside your body but the radiation can travel to your body
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7
Q

What is the risk or irradiation and what does it depend on?

A
  • risk of irradiation form a source is how likely that an object will be irradiated by source
  • depends on distance from source and type of radiation source emits
  • distance from source increases= amount of radiation reaching point decreases = irradiation risk lower
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8
Q

Why is the irradiation risk lower for sources that emit alpha radiation ?

A
  • alpha = shorter range compared to gamma

- irradiation risk = lower for source emitting alpha at given distance

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9
Q

When does contamination occur?

A
  • radioactive material is taken on the skin or inside the body
  • internal contamination = can’t be removed
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10
Q

What is the contamination risk?

A
  • how likely the object gets contaminated
  • radioactive source is solid = no risk for object not touching source
  • radioactive source is gas = could move and come into contact with object =increases risk
  • gases = inhaled = contaminates on inside
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11
Q

When an object become contaminated, how is the irridation risk effected?

A
  • contaminated = irradiation risk due to source = high as distance between source and object = small
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12
Q

Which is more longer lasting; irradiation or contamination?

A
  • irradiation = temporary as source is taken away = stops
  • contamination = lasts longer = if original source is taken away = atoms causing contamination are left behind causing more harm
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13
Q

How is the hazard associated with a radioactive source depends on its half life?

A
  • lower activity of radioactive source = safer to be around
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14
Q

If 2 sources with diff half lives have the same number of radioactive nuclei, which will have a lower activity?

A
  • source with longer half life will have a lower activity since the atoms are less likely to decay
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15
Q

If 2 sources with diff half lives have the same activity, which activity will fall faster?

A
  • activity of sample with shorter half life= fall faster than longer half life (if same type of radiation)
  • after a while = source with longer half life = higher activity = more dangerous to be around
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16
Q

What’s important when choosing radioactive source?

A
  • balance between source with higher enough activity to be useful but won’t be dangerous for too long
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17
Q

How do tracers work and what type do radioactive isotopes are used?

A
  • radioactive isotopes = emit gamma radiation
  • injected or ingested (drunk/eaten) to see how parts of the body are working
  • spread through body = progress followed on radiation detector
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18
Q

What type of half life do tracers need?

A
  • relatively short (few hrs) so radioactivity in patient can quickly disappear but long enough to still emit radiation when it reaches the right place
  • if too long (cancer)
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19
Q

What type of sources are used in medical tracer and why?

A
  • gamma (never alpha) sources
  • gamma penetrates tissue, so pass out of body and are detected
  • alpha can’t and is more dangerous inside the body
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20
Q

Which radioisotope is absorbed by a range of organs and has a half life of over 6 hrs?

A

Technicium-99

21
Q

How does radiotherapy work?

A
  • radiation directed carefully at specific dosage - depends on size & type of tumour and size & age of patient= kills cancer cells without damaging too many normal cells
  • a bit of damage is done = makes patient feel ill BUT if cancer is successfully killed off = worth it
22
Q

How can we treat cancer externally?

A
  • gamma rays focused on tumour using narrow beam
  • patient stays still and beam is rotated round them with tumour at centre
  • minimises exposure of normal cells to radiation so the damage to healthy tissue = limited
  • treatment = given in doses of time = healthy cells =repaired/ replaced
23
Q

How can we treat cancer internally?

A
  • implants with beta emitters = placed next to/inside the tumour
  • they damage cells in tumour BUT have short enough range = damage to healthy tissue is limited
  • implant with long half life should be removed = stop radiation killing healthy cells once cancerous= killed BUT if short enough = can be left in
24
Q

How can alpha emitters be used to treat cancer internally?

A
  • alpha emitters = injected into tumour = strongly ionising = lots of damage to cancer but short range so damage to normal tissue = limited
25
Q

What is nuclear fission?

A
  • type do nuclear reaction used to release energy from large unstable nuclei by splitting them into smaller nuclei
  • produces 2 smaller nuclei ( usually radioactive)and 2 or 3 neutrons
26
Q

What isotope of uranium is used in nuclear fission?

A

Uranium - 235

But Uranium - 239 is also fissionable

27
Q

What are the two ways nuclear fission can occur?

A
  • spontaneously (unforced and happens by itself)

- by absorbing a neutron (if nucleus absorb neutron = unstable and splits)

28
Q

What happens to the energy give out during nuclear fission?

A
  • splitting = lots of energy
  • some transferred to kinetic energy store or fission products
  • also extra energy carried away by gamma radiation
29
Q

How can nuclear fission of uranium lead to chain reaction?

A
  • slow moving neutron is absorbed into uranium nucleus
  • makes nucleus unstable =splits
  • each split = spits out 2 or 3 neutrons = might be absorbed by other nuclei causing them to split too = chain reaction
30
Q

What are the problems with chain reactions?

A
  • only occurs if enough nuclei around the first

- small mass of radioactive material means that neutrons will escape = reactions stop

31
Q

How do nuclear power stations use nuclear fission?

A
  • generate electricity from chain reactions using uranium/ plutonium as fuel
  • energy released = used to heat water to make steam = used to drive steam turbine connected to electricity generator
  • energy transferred to surroundings by fission is greater than energy transferred in combustion reactions (coal power stations)
32
Q

How are chain reactions in Nuclear power stations controlled?

A
  • control rods
  • lowered into reactor to absorb additional neutrons to slow down reactions
  • nuclear bomb= no control of fission as no rods so lots of energy transferred quickly = disruptive nature
33
Q

What are the problems with nuclear power and power plants?

A
  • disposal of waste
  • products of fission = highly radioactive and have long half lives
  • difficult and expensive to dispose off safely
  • risk of radiation leaks from plant = major catastrophes like Chernobyl
34
Q

Why is the overall cost of nuclear power high?

A
  • nuclear fuel = cheap
  • overall cost = high due to cost of power plant and final decommissioning
  • dismantling nuclear plant safely = takes decades
35
Q

What is nuclear fusion?

A
  • joining of 2 small atomic nuclei

- 2 light nuclei can join to create a larger nucleus which is more stable

36
Q

What do 2 hydrogen nuclei form to make?

A
  • hydrogen nucleus
37
Q

Which releases more energy, fusion or fission?

A
  • fusion releases a lot of energy
  • more than fission for a given mass of fuel
  • all the energy released in stars comes from fusion
38
Q

Why is energy formed in fusion?

A
  • due to difference in mass between original nuclei and new nucleus
  • total mass of hydrogen nuclei is larger than mass of hydrogen nucleus
  • extra mass is converted into energy and carried away by radiation
  • mass of nuclei before fusion = more than mass of nucleus after fusion
39
Q

Why is fusion better than fission?

A
  • fusion doesn’t create radioactive waste
  • and plenty of hydrogen to use as fuel
  • people try to use fusion reactors to generate electricity
40
Q

Why is the problem with fusion reactors?

A
  • fusion only happens at really high temp - 10 000 000 degrees and high pressure
  • to keep hydrogen in this = need extremely strong magnetic fields
  • only few experimental reactors around (none generating electricity yet)
41
Q

How does fusion happen in the sun?

A
  • hydrogen nuclei (protons) fuse together = form larger nuclei (isotopes of hydrogen/helium)
  • after more fusion reactions they make carbon,oxygen and iron
  • when this happens energy is transferred form nuclear store to heating and EM radiation
42
Q

Why can’t we carry out fusion in a lab?

A
  • hard to get

- repulsion by both protons being positive has to be overcome

43
Q

What happens when 2 protons fuse and hydrogen -2 and -3 fuse?

A
  • 2 protons fuse to make = deuterium/hydrogen - 2 made
  • deuterium can be fused to make tritium/hydrogen -3
  • hydrogen 2 and 3 can fuse = helium nucleus and neutron (more stable than hydrogen isotopes)
44
Q

What is the heaviest element made by fusion?

A
  • Iron

- elements heavier than iron are made in a supernova

45
Q

Why can fusion happen in the sun?

A
  • high temp = increase speed of nuclei

- high Pa = keep nuclei close for fusion

46
Q

How can you measure energy from fusion?

A

E = mc^2
Energy (J) = change in mass (kg) x speed of light ^2
Speed of light = 300 million m/s

47
Q

Why does alpha and gamma gas pose as a risk?

A
  • contamination risk of gas is higher than a solid as it can spread our and be inhaled
  • alpha radiation is most dangerous inside the body and gamma is most dangerous outside the body so it could be damaging due to irradiation and contamination
48
Q

Why should you keep sources as far away as possible?

A
  • the risk of irradiation/ radiation reaching you depends on the distance from the source
  • so the closer you get, the greater the risk

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