nuclear fission Flashcards
(13 cards)
how does a chain reaction of nuclear fission occur
slow neutrons collide with unstable uranium nucleus making it even more unstable and releasing energy, splitting into daughter nuclei and releasing fast moving neutrons that hit other uranium nuclei which split etc
what’s fissile nuclei
uranium nuclei
what are control rods
arranged to absorb neutrons so for every two or three neutrons that are released from a fission reaction, only one (approx) goes on to produce further fission
effect of lowering and raising metal rods
lowered to absorb more neutrons
raised so fewer are absorbed and reaction speeds up
what does the moderator do
slow down fast moving neutrons as it absorbs it and allows more to be available to the uranium
how do u stop the reaction
by dropping all the control rods into the reactor
how is the half life from nuclear fission high and what does this mean
as the waste products (daughter nuclei) are radioactive with large range of half lives so the products will stay reactive for 100/1000s of years so it’s difficult to safely dispose
what is nuclear fusion
2 light nuclei (eg hydrogen) collide and fuse to create a heavier larger nucleus (helium)
what are the conditions needed for nuclear fusion and what does this make it difficult for
high pressure and temperature
to build fusion reactors
why can only high energy (from high temp) nuclei make nuclear fusion
as 2 positively charged nuclei repel eachother so they have to get close to overcome large force
where does nuclear fusion occur naturally
in stars
why do fission reactors need thick walls
to absorb gamma radiation and neutrons and prevent it being released outside
does nuclear fission or fusion have longer half life radioactivity waste
fission
