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Physics ATAR > Ionising Radiation and Nuclear Reactions > Flashcards

Ionising Radiation and Nuclear Reactions Flashcards

1
Q

What is the nuclear model

A

Extremely small nucleus, contains 99.9% of atoms mass (Specific type of atom/nuclei) = Nuclide

  • Contains positively charged protons & uncharged neutrons (Nucleons)

Surrounded by negatively charged electrons

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2
Q

What is nuclear stability (Forces holding nuclei together)

A

Electric repulsion of protons, as positively charged protons repel
- Strains nucleus

Strong nuclear force between nucleons, overcomes electrostatic repulsion of protons
- Balance of two forces keeps nucleus stable

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3
Q

What is the notation for different nuclides

A

Atomic Number = n(Protons) in nucleus
Atomic Mass = n(Protons + Neutrons) in nucleus

AZX Notation

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4
Q

What are isotopes

A

Atoms that have same n(Protons), different n(Neutrons)

Same chemical properties

Different physical properties because of different mass number

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5
Q

What is atomic mass unit

A

Unit for relative atomic mass

1 amu = 1/12 mass of Carbon-12 atom

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6
Q

What are radioisotopes

A

Unstable isotopes

Randomly decay by emitting radiation from nucleus to be more stable (electron-Volts)

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7
Q

What are uses of radioisotopes as diagnostic tools

A

Scans of heart, lung, kidneys, gullbladder, thyroid

Diagnoses Heart disease, Alzheimer’s disease, Brain disordes

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8
Q

What are uses of radioisotopes as tumour treatment

A

Targets harmful organ / tissue, stops growth of its cells by damaging it

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9
Q

What is radioactive decay

A

Radioisotopes break down to become stable

  • During process, radiation is released
  • 3 forms; Alpha, Beta, Gamma
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10
Q

What is alpha decay

A

2 protons, 2 neutrons (Helium nucleus)

Posiively charged (+2)

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11
Q

What is properties of alpha decay

A

Low penetrating ability

Range few cm

High ionising ability

10% speed of light

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12
Q

What is beta decay

A

Beta Negative:
- 1 electron, 1 antineutrino
- Negatively charged (-1)

Beta Positive;
- 1 positron, 1 neutrino
- Positively charged

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13
Q

What is properties of beta decay

A

Medium penetrating ability

Medium ionisation ability

Range few m

90% speed of light

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14
Q

What is gamma decay

A

No particle, only high-energy electromagnetic radiation (High frequency light)

No charge

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15
Q

What is properties of gamma decay

A

High penetrating ability

Low ionisation ability

Range unlimited

Speed of light

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16
Q

What are the combinations of radiation

A

Atoms can emit more than one type of radiation at same time

Gamma radiation usually emitted with alpha / beta radiation

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17
Q

How to write nuclear equations

A

Mass, charge conserved

Use chemical symbols for elements

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18
Q

What are spontaneous transmutation reactions

A

Unstable nucleus becomes more stable by spontaneously emitting particle

  • Changes into different element / isotope

Alpha & Beta decay

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19
Q

What are artificial transmutation reactions

A

Managed process, changes 1 nuclide into another

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20
Q

What is decay series

A

Radionuclide decays, daughter nucleus not completely stable, undergoes further decay

  • Eventually stable isotope reached, sequence ends = Decay series
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21
Q

What is radioactive half-life

A

Time it takes for half the atoms in radionuclide sample to decay

  • Unaffected by physical & chemical conditions (Eg. Pressure, Temperature)
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22
Q

What is activity

A

n(Atoms) in sample that decay per second
- Decreases over time, over one-life, activity halves

Can be measured using geiger counter

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23
Q

What is absorbed dose

A

Amount of energy that can be absorbed by 1kg mass of tissue

24
Q

What does effect of radiation on body depend on

A

Quantiy & type of radiation absorbed

Nature of organs, cells, tissues exposed to radiation

Time exposed to radiation (How large)

25
Q

What is ionising radiation

A

Radiation that can ionise cells (Removes / Adds electrons to become charged, ion)

  • Can cause unwanted reactions, damaging / killing cells, or affecting cell division
26
Q

What is dose equivalence

A

Measuring absorbed radiation dose, taking into account type of radiation involved (Measured in Sieverts / Sv)

27
Q

What is quality factor

A

Weighting of damage caused by different types of radiation

28
Q

What does sources of radiation outside the body do

A

Beta & Gamma most dangerous, can reach & be absorbed by cells of organs

Alpha radiation unlikely to reach living cells

29
Q

What does source of radiation inside the body do

A

Alpha radiation most dangerous, strongly absorbed by cells, high ionisation ability

Beta & Gamma radiation unlikely to be absorbed by cells

30
Q

How to monitor radiation at work

A

People working around radiation monitor exposure to radiation for safety

Radiation invisible, cannot be felt, radiation workers wear radiation monitoring badge

  • 3 filters for each type of radiation
  • After worn, film devleoped to determine amount & type of radiation exposed to
31
Q

What is mass defect

A

Difference between mass of nucleus and sum of masses of nucleons

  • Mass of stable nucleus < Sum of masses of protons & neutrons
  • “Missing mass” = Binding energy (Mass-Energy equivalence)
32
Q

What is binding energy

A

Energy required to separate components from nucleus

  • Released when nucleus forms / separates (Hence mass missing)
33
Q

What does the binding energy graph tell us

A

Smaller nuclei undergo fusion
Bigger nuclei undergo fission

More energy per nucleon in fusion released, as greater % mass transformed into energy

34
Q

How to calculate binding energy if mass defect in amu

A

D(Energy) = 931m eV

35
Q

How to calculate binding energy if mass defect in kg

A

D(E) = mc^2

36
Q

What is nuclear fission

A

Atomic nucleus splits into 2 or more pieces

  • Triggered by absorption of neutron

When split: Daughter nuclei

37
Q

What are fissile nuclides

A

Capable of undergoing fission by slow-moving neutrons
- Only high atomic number elements, very few exist naturally

38
Q

What are fissionable & non-fissile nuclides

A

Capable of undergoing fission, by only high-energy neutrons

39
Q

How does fission occur

A

Fissile nuclide absorbs slow / high energy electron

  • Unstable, spontaneously undergoes fission
40
Q

How to calculate fission reactions

A

Use mass defect and binding energy

41
Q

How do chain reactions happen in nuclear fission

A

U-235 undergoes fission (Absorbs neutron), releases two or three neutrons

  • Neutrons absrbed by another U-235 nuclide, triggers another reaction

Mass release of energy in short time

42
Q

What are nuclear fuel

A

Many naturally occuring radioisotopes, like U-238, U-235

Proportion of U-235 too low for chain reaction, is enriched to be nuclear fuel

43
Q

What is critical mass

A

Minimum amount of enriched fissile material in sphere shape required to sustain chain reaction

Shape of nuclear fuel affects capacity to start chain reaction
- Sphere U-355 > Sheet U-235

44
Q

What are the elements of nuclear reactors

A

Fuel Rods

Moderator

Control Rod

Radiation Shield

45
Q

What are fuel rods

A

Long, thin rods containing pellets of enriched uranium

46
Q

What are moderators

A

Material that slows neutrons

So fissile nuclei can absorb neutron

47
Q

What are control rods

A

Material that absorbs neutrons

To control energy release

48
Q

What are radiation shields

A

Thick concrete wall

Prevents neutrons from escaping reactor

49
Q

How to manage low-level nuclear waste

A

From hospitals, industry, laboratories

Tools, clothing, wrapping material

Compacted / Incinerated, buried in sea / land

50
Q

How to manage medium-level nuclear waste

A

Reactor components, chemical sludges, contaminated materials

Solidified in bitumen / concrete, then buried

51
Q

How to manage high-level nuclear waste

A

Contaminated reactor parts

Requires special shielding, stored permanently

52
Q

What is nuclear fusion

A

Two light nucli fuse to form larger nucleus, with release of energy

Mass of reactants > Mass of products

53
Q

How to achieve nuclear fission

A

Difficult to achieve, as both nuclei positively charged
- Electrostatic force of repulsion

2 nuclei slowly approaches, electrostatic force makes them repel
- Can’t get close enough for strong nuclear force to take affect

2 nuclei approach at high speeds, overcomes electrostatic force
- Close enough for strong nuclear force to take effect
= Fusion Reaction

54
Q

How to calculate fusion reactions

A

Calculate using mass defect and binding energy

55
Q

What is needed in nuclear fusion reactors, and why are they better than nuclear fission reactors

A

Energy per nucleon far greater than fission reactions, as greater % mass transformed to energy

High temperature needed for fusion

56
Q
A

Physics ATAR (3 decks)

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