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Physics Additional > Topic 5 > Flashcards

Topic 5 Flashcards

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0
Q

Characteristics of beta particles

A

Move quite fast
Quite small
Negative charge
Moderately ionising

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1
Q

Characteristics of alpha particles

A 
Relatively big
Heavy
Slow moving
Strong positive charge
Strongly ionising
Don't penetrate far into particles
HELIUM nuclei
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2
Q

Characteristics of gamma

A

Weakly ionising

Penetrate a long way into materials

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3
Q

Chain reaction of Nuclear fission

A
  • slow-moving neutron absorbed by nucleus
  • nucleus becomes unstable and splits
  • 2 daughter nuclei atoms produced
  • 2 or 3 neutrons given out
  • these neutrons hit other uranium atoms, causing them to split
  • this is a chain reaction
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4
Q

How are chain reactions slowed in reactors?

A

Uranium fuel rods placed in a moderator to capture and slow down the fast moving neutrons

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5
Q

How to limit the rate of fission in a reactor

A

Control rods (often made of boron) lower the rate of fission by absorbing excess neutrons.

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6
Q

Are isotopes stable or unstable?

A

Some are stable (Carbon-12) but most are UNSTABLE (Carbon-14)

Unstable means it will give off radiation

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7
Q

What happens when a nucleus is unstable?

A

It emits radiation spontaneously and randomly to try and stabilise it. This process is called decay.

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8
Q

What are the three types of ionising radiation

A

Alpha -
Beta -
Gamma

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9
Q

Ionising radiation disadvantages

A

Mutations
Cell death
Cancer

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10
Q

Describe alpha

A

Most ionising
Has a short range
2 protons and 2 neutrons (helium nucleus)
Charge: +2

STOPPED BY: paper, skin

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11
Q

Describe beta

A

Medium ionising power
Medium range
Fast moving electron
Charge: -1

STOPPED BY: thin aluminium

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12
Q

Describe gamma

A

Low ionising power
Low range
Electromagnetic wave
Charge: none

STOPPED BY: lead, concrete

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13
Q

What is fission?

A

The process of splitting a large atom into two smaller bits whilst releasing lots of energy

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14
Q

What happens in fission

A

Neutron absorbed into parent nucleus
Parent nucleus becomes unstable and splits
Daughter nucleus’ given out as well as 2 or 3 neutrons
These neutrons can go and fission other nuclei, leading to a chain reaction

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15
Q

What keeps the reactor safe

A

Control rods

16
Q

What is the job of a control rod. Why is it used

A

Controls the rate of FISSION

If too much fission is happening the reactor can overheat and melt

17
Q

How do control rods work in a reactor

A

The control rods can be lowered to absorb neutrons. They are made of particular isotope or material (ie boron or silver) that can absorb neutrons without becoming radioactive themselves

18
Q

How does a moderator work in a reactor?

A

It slows down the neutrons emitted from fission reactions

19
Q

Why are moderators used to keep reactors safe

A

If the neutrons are moving to fast they won’t be absorbed by other nuclei to create fission

20
Q

How do moderators work in reactors to keep them safe?

A

The fuel rods are generally placed in or surrounded by the moderator. Water is the most common moderator, although another example is graphite.

21
Q

What three things keep the reactor safe during fission

A

Control rods (ie made of boron or silver)
Moderator (ie water/graphite)
Coolant

22
Q

What is the job of the coolant in a reactor

A

Keeps down the temperature of the reaction

23
Q

Why are coolants used?

A

Without something to take heat away, the heat generated by the reaction could cause a melt-down

24
Q

How does a coolant keep a reactor safe?

A
  • The coolant material (usually water) is pumped into the reactor where it heats up.
  • It is then cooled by heating a separate supply of water (which is used to turn the turbine).
  • It condenses and is pumped round again.
25
Q

What is fussion?

A

The opposite of fission - joining together very small nuclei to make a larger one.

It released even more energy than fission (it’s how the Sun gets its power).

26
Q

What conditions are needed for fusion to occur?

A
  • Very high temperature (higher than sun)

- Very high pressure

27
Q

Why is fusion difficult?

A

Because it needs such a high temperature and pressure due to electrostatic repulsion. We cannot wait (like the Sun can) for fusion to happen over thousands of years, so it needs to be hotter so that fusion occurs quicker

28
Q

What two types of hydrogen jump start fusion

A

Deuterium (hydrogen with 1 neutron) and Tritium (2 neutrons)

This reactions makes energy, helium neutrons and protons and neutrons

29
Q

Why do scientists have to use extremely strong magnets in fusion?

A

To accelerate and contain plasma which they use to ignite fusion

Physics Additional (9 decks)

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