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Physics ATAR U1 > 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
What is ionising radiation
Radiation that can ionise cells (Removes / Adds electrons to become charged, ion) - Can cause unwanted reactions, damaging / killing cells, or affecting cell division
26
What is dose equivalence
Measuring absorbed radiation dose, taking into account type of radiation involved (Measured in Sieverts / Sv)
27
What is quality factor
Weighting of damage caused by different types of radiation
28
What does sources of radiation outside the body do
Beta & Gamma most dangerous, can reach & be absorbed by cells of organs Alpha radiation unlikely to reach living cells
29
What does source of radiation inside the body do
Alpha radiation most dangerous, strongly absorbed by cells, high ionisation ability Beta & Gamma radiation unlikely to be absorbed by cells
30
How to monitor radiation at work
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
What is mass defect
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
What is binding energy
Energy required to separate components from nucleus - Released when nucleus forms / separates (Hence mass missing)
33
What does the binding energy graph tell us
Smaller nuclei undergo fusion Bigger nuclei undergo fission More energy per nucleon in fusion released, as greater % mass transformed into energy
34
How to calculate binding energy if mass defect in amu
D(Energy) = 931m eV
35
How to calculate binding energy if mass defect in kg
D(E) = mc^2
36
What is nuclear fission
Atomic nucleus splits into 2 or more pieces - Triggered by absorption of neutron When split: Daughter nuclei
37
What are fissile nuclides
Capable of undergoing fission by slow-moving neutrons - Only high atomic number elements, very few exist naturally
38
What are fissionable & non-fissile nuclides
Capable of undergoing fission, by only high-energy neutrons
39
How does fission occur
Fissile nuclide absorbs slow / high energy electron - Unstable, spontaneously undergoes fission
40
How to calculate fission reactions
Use mass defect and binding energy
41
How do chain reactions happen in nuclear fission
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
What are nuclear fuel
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
What is critical mass
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
What are the elements of nuclear reactors
Fuel Rods Moderator Control Rod Radiation Shield
45
What are fuel rods
Long, thin rods containing pellets of enriched uranium
46
What are moderators
Material that slows neutrons So fissile nuclei can absorb neutron
47
What are control rods
Material that absorbs neutrons To control energy release
48
What are radiation shields
Thick concrete wall Prevents neutrons from escaping reactor
49
How to manage low-level nuclear waste
From hospitals, industry, laboratories Tools, clothing, wrapping material Compacted / Incinerated, buried in sea / land
50
How to manage medium-level nuclear waste
Reactor components, chemical sludges, contaminated materials Solidified in bitumen / concrete, then buried
51
How to manage high-level nuclear waste
Contaminated reactor parts Requires special shielding, stored permanently
52
What is nuclear fusion
Two light nucli fuse to form larger nucleus, with release of energy Mass of reactants > Mass of products
53
How to achieve nuclear fussion
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
How to calculate fusion reactions
Calculate using mass defect and binding energy
55
What is needed in nuclear fusion reactors, and why are they better than nuclear fission reactors
Energy per nucleon far greater than fission reactions, as greater % mass transformed to energy High temperature needed for fusion

Physics ATAR U1 (6 decks)

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