The document discusses nuclear reactions and power generation from nuclear fission. It describes how uranium-235 can undergo fission when hit by a neutron, releasing energy. This property is harnessed in nuclear reactors, where sustained fission reactions produce heat to generate electricity. The document outlines the basic design of nuclear power plants and discusses safety considerations and different types of reactor designs.

1. Radiation
Nuclear Reactors

2. Nuclear Reactions
 Uranium is a fairly common element on
Earth and was incorporated into the
planet during the planet's formation
 U-238 makes up 99 percent of the
uranium on the planet
 Uranium-235 makes up about 0.7
percent of the remaining uranium found
naturally
 Uranium-235 has an interesting
property

3. Nuclear Reactions
 U-235 decays naturally, just as U-238
does, by alpha radiation
 U-235 also undergoes spontaneous
fission a small percentage of the time
 Fission is defined as “the splitting of an
atom”
 Also, U-235 is one of the few materials
that can undergo induced fission

4. Nuclear Reactions
 If a free neutron runs into a U-235
nucleus, the nucleus will absorb the
neutron without hesitation, become
unstable and split immediately
 The probability of a U-235 atom
capturing a neutron as it passes by is
fairly high
 In a reaction two or three neutrons are
ejected from each fission causing other
fissions to occur

6. Nuclear Reactions
 Theprocess of capturing the neutron
and splitting happens very quickly
 (1 x 10-12 seconds) picoseconds
 An incredible amount of energy is
released, in the form of heat and
gamma radiation, when a single atom
splits
 The energy is released because the
products and the neutrons, together,
weigh less than the original U-235 atom

7. Nuclear Reactions
 The difference in weight is converted
directly to energy at a rate governed by
the equation E = mc2
 a pound of highly enriched uranium
used to power a nuclear submarine or
nuclear aircraft carrier is equal to about
a million gallons of gasoline
 a pound of uranium is smaller than a
baseball and a million gallons of
gasoline would fill a five-story building

8. Nuclear Reactions
 In order for a reactor to work, a sample
of uranium must be enriched , so that it
contains two to three percent or more of
uranium-235
 Weapons-grade uranium is composed
of 90 percent

9. Nuclear Power
 uranium is formed into pellets with
approximately the same diameter as a
dime and an inch long
 These pellets are then placed in rods
that are “super critical” meaning they
would over heat and melt if left alone
 To prevent this, control rods made of a
material that absorbs neutrons are
inserted

10. Nuclear Power
 The depth the rods are inserted into the
uranium, determines the amount of
fission taking place
 All the way in… the reactions stop
 All the way out….the reactions increase
until meltdown occurs
 The uranium bundle acts as an
extremely high-energy source of heat. It
heats the water and turns it to steam

12. Nuclear Power
 The steam drives a steam turbine,
which spins a generator to produce
power
 In some plants the steam contacts other
water and turns it to steam… this way,
the radioactive water never touches the
turbine
 there is little difference between a
nuclear plant and a coal or oil-fired plant
except for the source of the heat used

13. Nuclear Power
 The reactor's pressure vessel is
typically housed inside a concrete liner
that acts as a radiation shield
 the containment vessel is protected by
an outer concrete building that is strong
enough to survive such things as
crashing jet airliners

15. Nuclear Power
 Uranium-235 is not the only possible
fuel for a power plant. Another
fissionable material is plutonium-239

16. Nuclear Power
 Plutonium-239 can be created by U-238
fission, therefore some reactors are
used to make weapons grade plutonium
 If fact, the first reactors every produced
were used for this purpose…. Atomic
bombs
 Research reactors work on the same
principals as power reactors, however
are used for other purposes

17. Nuclear Power
 They can be used to expose materials
to high levels of radiation
 To bombard elements with neutrons to
create new isotopes
 And can be used to work on new
energy possibilities
 How safe are they? Do they hurt the
environment?

18. Nuclear Safety
 Compared with a coal-fired power plant,
nuclear power plants are a dream come
true from an environmental standpoint
 coal-fired power plant actually releases
more radioactivity into the atmosphere
than a properly-functioning nuclear
power plant
 Fossils fuel plants (oil/coal) release
huge amounts of carbon into the
atmosphere, C-14 is radioactive

19. Nuclear Safety
 There are also drawbacks with nuclear
power…
 Mining and purifying uranium has not,
historically, been a very clean process
 Improperly-functioning nuclear power
plants can create big problems i.e. The
Chernobyl
 Spent fuel from nuclear power plants is
toxic for centuries and there is no safe
permanent storage facility for it, yet

20. Nuclear Safety
 Transporting nuclear fuel to and from
plants also poses some risk
 Unfortunately, there are less new
nuclear power plants being constructed
due to these risks
 At some point however, there will be no
more fossil fuel and we will have no
choice but to build more nuclear power
plants

21. Reactor Types
 There are a couple different types of
reactors, all use the same principle of
nuclear fission
 The four types are …
 Graphite Moderated Reactor
 Fast Breeder Reactor (FBR)
Liquid Metal (LMFBR) (most common
type of breeder)

22. Reactor Types
 LightWater Reactor (LWR)
 Heavy Water Reactor (HWR)
 There are two types of light water
reactors
 Boilingwater reactor
 Pressurized water reactor
 Boiling water reactor
 CoolantType - water
 Moderator Type – water

23. Reactor Types
 Fuel - uranium-dioxide (UO2)
 Comments - steam generated inside the
reactor goes directly to the turbine

25. Reactor Types
 Pressurized water reactor
 Coolant Type - water
 Moderator Type – water
 Fuel - uranium-dioxide (UO2)
 Comments - steam is generated outside
the reactor in a secondary heat transfer
loop

27. Reactor Types
 Heavy Water reactors work just like light
water reactors, however, instead of
using water H2O…. Normal hydrogen is
replaced with deuterium H2

28. Reactor Types
 There
are two types of Graphite
moderated reactors…
 Gas Cooled
 Water Cooled
 Gas Cooled
 Coolant Type - gas (carbon dioxide or
helium)
 Moderator Type – graphite
 Fuel -- uranium

29. Reactor Types
 Comments - used in Britain, and France

30. Reactor Types
 Water Cooled Reactors
 Coolant Type – water
 Moderator Type – graphite
 Fuel -- uranium
 Comments - used in USA & former
Soviet Union, e.g. Chernobyl

31. Reactor Types
 Fast Breeder Reactor (FBR)
 Coolant Type – molten liquid sodium
 Moderator Type – none required
 Fuel - plutonium dioxide and uranium
dioxide in various arrangements
 Comments - breeder reactors are
designed to produce more fissile
material than they consume