P2 topic 5 Flashcards
(71 cards)
fission reactions
take place in a nuclear reactor to generate electricity on a large scale
what happens in a fission reaction?
a slow-moving neutron is absorbed by a uranium-235 nucleus, making it unstable; the new nucleus splits into two smaller daughter nuclei and 2 or more fast moving neutrons; energy is released as the kinetic energy of the daughter nuclei and the neutrons
how can fission reactions be triggered?
by bombarding uranium-235 nuclei with neutrons
chain reaction
a process in which an enormous amount if energy is produced when neutrons from previous fission reactions go on to produce further uncontrolled fission reactions
how do nuclear power stations create energy?
most nuclear power stations use uranium or plutonium as fuel for the reactions; a large amount of energy, in the form of KE of the neutrons and the daughter nuclei is released in fission reactions; KE turned into heat and used to boil water to mane steam; steam powers turbines
why is disposal of nuclear waste a major concern?
for daughter nuclei produced in fission reactions can remain active for thousands of years
what are the four main components of a reactor?
fuel rods, coolant, moderator and control rods
fuel rods
contain pellets of nuclear fuel in the form of uranium dioxide
coolant
removed the thermal energy produced in the fission reactions in the reactor core, so it can be used to heat water to create steam to power generator turbines (in a water-cooled reactor)
moderator
surrounds the nuclear fuel rods and slows down the fast-moving neutrons-slow-moving neutrons have a greater chance of reacting with uranium nuclei than fast-moving neutrons
control rods
can be lowered into the reactor to absorb the neutrons and so slow down the fission reactions and control the chain reactions
fusion reactions
cause the energy generated by the Sun and the stars
critical mass
a chain reaction can only be sustained by a large amount of uranium-235- in small amounts, too many neutrons will escape and not take part in fission reactions; the minimum mass of a fissile material required to sustain a chain reaction
what is the energy released in fission reactions used by?
nuclear reactors to produce energy
nuclear fusion
a nuclear reaction in which two smaller, lighter nuclei join or fuse together to produce one larger nucleus, creeping vast amounts of energy- the fusing together of hydrogen nuclei to produce helium nuclei
what is needed for nuclear fusion to take place?
extremely high temperatures
what is the energy source that keeps our Sun and other stars burning?
the fusion of hydrogen and other lighter nuclei
isotopes of hydrogen
deuterium and tritium
who were the scientists who claimed to have carried out cold fusion?
Stanley Pons and Martin Fleischmann in 1989
cold fusion
an invalidated theory that proposed nuclear fusion occurring at room temperature- the scientists claimed that their experiment had produce vast amounts of thermal energy
why were Pons and Fleischmann criticised by other scientists?
their announcement gained worldwide publicity- but they had not published enough technical details of their experiment for other scientists to reproduce their results
what do the majority of scientists think about cold fusion?
they reject the theory, as it couldn’t be validated by reproducing the experiment
why are fusion reactions more difficult to trigger than fission reactions?
hydrogen nuclei (protons) are positively charged and therefore repel one another
how can you improve the changes of a fusion reaction taking place?
You can increase the speed at which the nuclei move
