P7.7/P7.8 - Fission and Fusion reactions Flashcards
induced fission
-nucleus of a fissionable atom
-struck by neutron + absorbs it
-nucleus splits
-energy released
-other neutrons emitted
spontaneous fission
-involves no neutrons
Fission releases
- several neutrons at high speed
-gamma radiation
-KE in fission neutrons / fragment nuclei
Chain reaction
-emits 2 neutrons
-causes other nuclei to split
-fission neutrons = more fission events
fission neutrons produce
steady rate of energy in core
-chain reaction
Fission fuel
-enriched uranium
-non fissionable uranium (238) and 2% fissionable U(235)
non fissionable nuclei change into
heavier nuclei instead
Reactor core
-contains fuel rods
control rods
water
-made up of thick steel
Steel for core? and concrete walls
-withstands high temps and high pressures
-concrete prevents radiation escaping
Fusion reaction
-2 smaller nuclei fuse
-1 larger nuclei
-releases energy (converted from mass)
-energy = radiation
hen does fusion occur
-high temps
-high pressures
-if mass of nucleus is 55 or less
Sun
-75% hydrogen
-25% helium
-made from plasma
plasma
-bare nuclei
-no electrons
-fuse when collide = release energy
2 protons fuse =
heavy H and other particles
2 more protons collide with H =
heavier nuclei
2 heavier nuclei of H collide =
4 HE
-KE and other particles emitted
Fusion reactors
-plasma heated at high pressure/temp
Why must the fusion reactor resemble conditions of the sun
-nuclei will repel = same charge
-conditions = faster = overcome + fuse
how is the plasma heated in a fusion reactor
electric current
magnetic field in fusion reactor
-prevents plasma from touching sides
-cooling off = stops reaction
Pros of fusion
-fuel is available = H in sea
-Helium product = non radioactive gas (harmless)
-Energy may generate electricity
Cons of fission
-fuel is only available in some places in the world
-produces nuclear waste
Background radiation is
-radon gas
-travelled through ground rock
-emits alpha particles - health hazard
why store radioactive waste undergorund
-prevents contamination
-radiation causes cancer
short half life means
-emits lots of radiation in a short amount of time
-dangerous
Activity decreasing when storing underground
-hazards decrease with time