Nuclear reactors Flashcards
A thermal nuclear reactor in a nuclear power station contains _____ of _____ which are evenly placed in a ______ known as the _____ remotely to keep workers as far away from the ______ as possible.
fuel rods of uranium
steel vessel
reactor core
radiation
Coolant =
= water at high pressure in PWR (Pressurised Water Reactor) or CO2
The reactor core contains ______ and a _____ as well as the _____ and is connected by
The reactor core contains control rods and a coolant as well as the fuel rods and is connected by a means of steep pipes to a heat exchanger.
A pump is used to force the _____ through the______ (where it is _____) and through the ______ where it is used to ______ to drive the _____ that ____the_______ in the power station.
coolant reactor core heated heat exchanger raise steam turn electricity generators
The reactor is described as a thermal nuclear reactor because
s
the fission neutrons are slowed down to a kinetic energy roughly equal to the kinetic energy of the moderator molecules
Thermal neutrons =
slowed down fissionable neutron
Enriched uranium =
done by a centrifuge
uranium with an increased proportion of U-235 so it is more fissile
98% non fissionable U-238 and 2% U-235 unlike the 1% found naturally
Fission occurs when
U-235 absorbs a low energy/speed neutron forming the very unstable U-236 that splits forming two daughter nuclei and releasing 2-3 neutrons with very high kinetic energy
In order to cause a chain reaction, fission neutrons need to… so that…
be slowed down significantly to cause further fission so that the U-235 can absorb them otherwise they would be too fast.
How are the fission neutrons slowed down
the fuel rods are surrounded by a moderator made from graphite or water so that the neutrons are slowed down by repeated elastic collisions with the moderators atoms.
One important property of moderator
similar mass to neutrons so more efficient in slowing neutrons down
Explain the water’s role in a PWR and how a chain reaction is caused
In the Pressurised Water Reactor, the water in the reactor core acts as the moderator as well as acting as a coolant. The neutrons elastically collide with the hydrogen atoms in the water molecules (due to their similar masses) causing them to transfer most of their kinetic energy to the water molecules which then heat up and produce steam while the low speed neutrons induce further fission with the U-235 isotope causing a chain reaction to occur.
Two types of moderators
Water
Graphite core
5 parts of a nuclear reactor
Diagram
1) Moderator (water)
2) fuel rods
3) control rods
4) pump
5) cool water
6) steam
7) concrete case
How does the water coolant end up in the enivronment
Once the water is turned into steam, the steam produced drives a turbine that further drives a generator and excess hot steam is transferred to a cooling tower where it is condensed and reused or released into the environment as water vapour
