p6.2 Flashcards

done all flashcards, in line with spec

1
Q

what is the difference between small and large nuclei when they are unstable?

A

small nuclei = radioactive decy (emit alpha, beta, gamma radiation)

large nuclei = nuclear fission
(break apart into two nuclei)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

define nuclear fission

A

the splitting of a large parent nucleus into two smaller daughter nuclei, with the release of energy and neutrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what causes most nuclear atoms to undergo fission

A

usually hit with a neutron + the unstable nucleus absorbs a neutron

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

why does radioactive decay not occur with large unstable nuclei?

A

as it would not make the nucleus stable

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what does the term fissile mean?

A

when an atom can be made to undergo fission

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

how do nuclear power stations prevent a nuclear meltdown?

A

have control rods which absorb surplus neutrons so energy is generated at a steady rate
(so only one neutron from each fission event can produce another fission event)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is a nuclear chain reaction?

A

process in which neutrons released during a fission event go on to produce further fission events

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what happens during an uncontrolled chain reaction? (and give an example when that happens)

A
  • every neutron from each fission event goes on to produce further fission events
  • energy released at exponential rate
  • nuclear bomb
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what are fissionable isotopes of an element?

A

isotopes which can be made unstable, but they themselves are stable

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

if you add neutrons to any heavy nuclei, will it become unstable?

A

no, they must be fissionable isotopes (so can be made unstable)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

give one example of a fissionable material

A

uranium-235

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

why must there be a material that absorbs neutrons in a nuclear reactor?

A
  • no material to absorb neutrons = an uncontrollable reaction occurs
  • energy released at exponential, increasing rate
  • very dangerous, lead to an explosion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

define what nuclear fusion is

A

the joining of two small parent nuclei into a larger daughter nucleus, with the release of energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

where does nuclear fusion occur?

and how

A

in stars

- 2 light nuclei (ie. hydrogen) forced together at high speeds + form heavier nuclei (ie. helium)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

advantages of nuclear fusion? 4

A
  • no radioactive waste produced (forms stable nuclei)
  • fuel needed is available in water (ie. hydrogen - from electrolysis)
  • fusion produces a lot more energy than fission
  • no greenhouse gases produced
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

disadvantages of nuclear fusion?

A
  • building reactors is very difficult/not viable
17
Q

why is nuclear fusion currently not viable?

A

more heat energy is required to make nuclei overcome repulsive forces + fuse than is released from fusion

18
Q

why are stars able to carry out fusion easily?

A

have very high temperatures + very high pressures

high pressure due to strong gravitational pull

19
Q

why is nuclear fusion so hard?

A

all nuclei have the same positive charge, and so they repel each other (very hard for them to join)

20
Q

why are high temperatures and pressures needed for nuclear fusion?

A

temp = nuclei moving at high speeds

pressure = keeps nuclei close enough to fuse

21
Q

where does the energy come from in nuclear fusion?

A
  • when two smaller nuclei fuse, the mass of the larger one is slightly smaller than the total mass of the smaller nuclei
  • so the ‘missing mass’ is transformed into energy (by the equation e = mc^2)
  • and released as radiation
22
Q

how does nuclear fusion release so much energy?

A

as the speed of light is very large, and when substituted into the equation e=mc^2, it can produce a huge amount of energy

23
Q

similarities of nuclear fusion and fission

A
  • both produce more energy than fossil fuels

- both involve the use of nuclei

24
Q

differences of nuclear fusion and fission

A

FUSION

  • two small nuclei to a larger one
  • more energy released than in fission
  • no dangerous waste is produced
  • needs high pressure + temp

FISSION

  • large unstable nuclei break apart
  • only needs a neutron to start reaction
  • produces dangerous radioactive waste as by-product
25
what is the difference between contamination and irradiation?
contamination - radioactive material is injested/taken in irradiation - when you are exposed to radiation from an external source
26
how do doctors use radiation?
inject patients with radioactive isotopes (to see if objects functioning correctly) - radiation is detected by a gamma camera
27
is contamination or irrigation more dangerous?
contamination, as it lasts for a longer period of time (more ionising radiation)
28
why are radioactive materials dangerous to the body, but low radiation is not?
as the body can repair itself from small doses of radiation | ie. everyday due to background radiation
29
what kind of half life must a tracer have in medicine?
not too short = decay before using gamma camera not too long = tracer emits radiation for a long time + harms body cells greatly
30
what can a gamma knife be used for?
gamma radiation onto a cancer tumour only (healthy cells = low dose)
31
why do doctors use gamma radiation instead of alpha or beta radiation?
as it has the least ionising power (from within the body), and would pass straight through the atom, and pose the least harm to the patient
32
why is alpha radiation the most dangerous if contaminated with it?
as it is strongly ionising, and so would damage body cells greatly
33
what forms of radiation are the most dangerous if from an external source?
gamma and beta, as they have a longer range and can penetrate the skin and damage cells
34
hazards of contamination?
cannot remove radioactive material from inside you
35
does using radioactive cosmetics contaminate or irridate you?
contaminate as it is on your skin, and is absorbed (later is inside your body)
36
how do the hazards assocaited with radioactive material differ according to the half-life involved?
- longer half life - means it releases radiation for longer - so can ionise cells repeatedly + damage them