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physics (paper one) > nuclear fission and fusion (topic 4) > Flashcards

nuclear fission and fusion (topic 4) Flashcards

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1
Q

the smaller masses may be attracted by the star and become…

A

planets

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2
Q
A

uranium-235

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3
Q

describe what happens to the nucleus of an atom during nuclear fission (2)

A
  • splits into two smaller parts
  • and two/three neutrons
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4
Q
A
  • steam
  • turbine
  • generator
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5
Q
A

protostar
red giant
black dwarf

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6
Q

(protostar, red giant, black dwarf)

A
  • Alpha Centauri A
  • stars same size as Sun form black dwarfs
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7
Q

describe the process of nuclear fission (3)

A
  • uranium nucleus absorbs a neutron
  • nucleus becomes unstable and splits into two two daughter nuclei and several neutrons
  • releases energy in the process
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8
Q

the diagram shows a nuclear fission reactor, label the following parts on the diagram:
- control rod
- moderator
- fuel rod
- shielding
- reactor

A
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9
Q

explain the process of nuclear fusion (2)

A
  • two light nuclei join together / combine
  • to form a heavier nucleus, releasing energy in the process
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10
Q

state the conditions necessary for nuclear fusion to occur (2)

A
  • extremely high temperature
  • high pressure
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11
Q

explain why extremely high temperature and high pressure are needed for fusion to occur (2)

A
  • nuclei are positively charged
  • high temperature and pressure needed to overcome the electrostatic repulsion between nuclei
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12
Q

explain why nuclear fusion is more desireable than nuclear fission (2)

A
  • more energy released per kg of fuel
  • the products of fission are radioactive and need careful disposal (or products of fusion are not radioactive)
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13
Q

nuclear fusion naturally occurs in stars, describe what happens during nuclear fusion (3)

A
  • small nuclei join
  • to produce a larger nucleus
  • releasing energy
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14
Q
  • water
  • concrete
  • proton
  • neutron
  • fuel rods
  • neutrons
  • chain
  • control rods
A
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15
Q
A
  • mass number of 4 above He
  • atomic number of 0 for the neutron
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16
Q

explain why it is difficult to replicate the nuclear fusion of hydrogen on Earth (3)

A
  • hydrogen nuclei are both positively charged
  • need a high speed / high kinetic energy
  • to overcome the electrostatic forces of repulsion
17
Q

compare the similarities and differences between nuclear fission and fusion (3)

A
  • both fission and fusion release energy
  • fission occurs when nuclei split whereas fusion occurs when nuclei join
  • fission products are radioactive / fusion products are not radioactive
18
Q
A
19
Q

describe how the rate of fission can be reduced using a nuclear reactor (2)

A
  • inserting the control rods will slow the rate of fission
  • by absorbing more of the excess neutrons
20
Q

describe what is meant by a chain reaction (3)

A
  • neutron absorbed by uranium nuclei
  • causes it to split into two daughter nuclei and several neutrons
  • neutrons released are absorbed by other uranium nuclei, causing further fission
21
Q
A
  • total number of nucleons on left of arrow = 235 + 1 = 236
  • number of neutrons released = 236 - 92 - 141 = 3 neutrons
22
Q

discuss how radioactive waste is disposed of and potential concerns (3)

A
  • idea of strong containers
  • idea of containers that can’t rust
  • idea that rust-proof containers are difficult/expensive to manufacture
  • reference to security of waste site
  • reference to dilution in sea water
  • reference to leakage into water table
  • store underground (or away from people)
23
Q
A
  • activity halves every half-life
  • activity after 1 half life = 48 kBq
  • activity after 2 half lives = 24 kBq
  • activity after 3 half lives = 12 kBq
  • activity after 4 half lives = 6 kBq
  • activity after 5 half lives = 3 kBq
  • 5 half lives = 5 x 15 million years = 75 million years
24
Q
A
25
Q

describe an advantages and a disadvantage of using nuclear fission power stations compared to coal-fired power stations (2)

A

advantages:
- no greenhouse gases produced OR nuclear doesn’t contribute to global warming
- large amount of energy released from a small amount of fuel
- low fuel cost compared to fossil fuel power plants
disadvantages:
- nuclear power stations are expensive to build
- nuclear fission power stations produce radioactive waste
- risk of nuclear accidents

26
Q

nuclear fission reactors are surrounded by thick concrete shielding, suggest why (2)

A
  • radioactive products release gamma radiation which is harmful
  • shielding absorbs the gamma radiation
  • needs to be thick concrete as gamma is highly penetrating.
27
Q

a nuclear power station converts 35% of the energy from nuclear fission into energy which is transferred electrically through the National Grid, rission reactions release 1000 MJ per second, calculate the power of the energy distributed

A
28
Q

explain with reference to the parts of the nuclear reactor how the rate of fission could be increased to provide a higher output power (2)

A
  • remove control rods
  • to reduce number of excess neutrons absorbed
29
Q

the required output is 700 MW, the nuclear fission power station converts 35% of the energy from fission into useful energy for transmission, calculate the energy released by fission reactions per second to meet this demand

A
30
Q

state two disadvantages of using nuclear fission power stations compared to solar farms (3)

A
  • nuclear fission power stations produce radioactive waste
  • risk of nuclear accidents/meltdowns
  • nuclear power stations are expensive to build
31
Q

state two advantages of using a solar panel farm compared to a coal-fired power station (2)

A
  • solar panels do not produce greenhouse gases
  • solar energy is a renewable resource
32
Q
A
33
Q

describe the purpose of the moderator in a nuclear fission power station (2)

A
  • the moderator slows neutrons down
  • to make it more likely for them to absorbed by uranium nuclei

physics (paper one) (25 decks)

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