Nuclear Power Stations Flashcards
what is the most common nucleus used in fission reactios
uranium-235
what is a thermal neutron
a slow moving neutron
what happens when the uranium nucleus absorbs the neutron
- it becomes unstable
- causing it to break up into pieces
what pieces does it break up into
- 2 daughter nuclei
- and usually 3 fast moving neutrons
why do the neutrons need to be slow moving when coming into contact with a uranium nucleus
- so that they are absorbed by the nucleus
- if theyre too fast they will simply pass through them
- meaning no reaction occurs
what is a moderator
- a material used in a nuclear reactor
- to slow fast-moving neutrons to thermal speeds
what are examples of a moderator
water or graphite
why is a moderator needed
- for the fast moving neutrons ejected from a fission can be slowed
- so when they reach the next fuel rod they can be absorbed
what does this repeated sequence of fission eventually create and why
- a chain reaction
- because one neutron causes the release of two more
- which will each do the same to the next nucleus
what is used to control this chain reaction
control rods
what do control rods do
- they absorb excess neutrons from the reactions
- in order to control the chain reaction
if there is a failure in the control rod system when they have been lowered in the reactor on an electromagnetic support, what happens
- gravity pulls them down completely into the reactor core
- where they absorb all neutrons
- hence shutting the reaction down
for examples sake, how many neutrons would a boron control rod absorb per fission in order to maintain a constant fission rate and why
- if three neutrons are released per fission
- it will need to absorb two
- so that only one neutron will be resulting is fissions
- therefore keeping the fission rate constant