p6.2 Flashcards
done all flashcards, in line with spec
define nuclear fission
the splitting of a large parent nucleus into two smaller daughter nuclei, with the release of energy and 2 or 3 neutrons
what causes most nuclear atoms to undergo fission
usually hit with a slow-moving neutron + the unstable nucleus absorbs a neutron
why does radioactive decay not occur with large unstable nuclei?
as it would not make the nucleus stable (does not release enough energy)
what does the term fissile mean?
when an atom can be made to undergo fission
how do nuclear power stations prevent a nuclear meltdown?
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)
what is a nuclear chain reaction?
process in which neutrons released during a fission event go on to produce further fission events
what happens during an uncontrolled chain reaction? (and give an example when that happens)
- every neutron from each fission event goes on to produce further fission events
- energy released at exponential rate
- nuclear bomb
what are fissionable isotopes of an element?
isotopes which can be made unstable, but they themselves are stable (AND CAN UNDERGO NUCLEAR FISSION)
if you add neutrons to any heavy nuclei, will it become unstable?
no, they must be fissionable isotopes (so can be made unstable)
give one example of a fissionable material
uranium-235
why must there be a material that absorbs neutrons in a nuclear reactor?
- no material to absorb neutrons = an uncontrollable reaction occurs
- energy released at exponential, increasing rate
- very dangerous, lead to an explosion
define what nuclear fusion is
the joining of two small parent nuclei into a larger daughter nucleus, with the release of energy
where does nuclear fusion occur?
and how
in stars
- 2 light nuclei (ie. hydrogen) forced together at high speeds + form heavier nuclei (ie. helium)
advantages of nuclear fusion?
- 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
disadvantages of nuclear fusion?
- building reactors is very difficult/not viable
