NUCLEAR ENERGY

Adam Smalley

Objectives

Describe how neutrons produced in a fission reaction may be used to initiate further fission reactions (chain reactions)

Distinguish between controlled nuclear fission (power production) and uncontrolled nuclear fission (nuclear weapons)

Describe what is meant by fuel enrichment Describe the main energy transformations that

take place in a nuclear power station Discuss the role of the moderator and the control

rods in the production of controlled fission in a thermal fission reactor

Objectives (Cont)

Discuss how neutron capture by a nucleus of uranium-238 (238U) results in the production of a nucleus of plutonium-239 (239Pu)

Describe the importance of plutonium-239 (239Pu) as a nuclear fuel

Discuss safety issues and risks associated with the production of nuclear power

Outline the problems associated with producing nuclear power using nuclear fusion

Solve problems on the production of nuclear power

Nuclear Fission

CONTROLLED UNCONTROLLED

Fuel Enrichment

Fuel needed: uranium-235 Most abundant isotope: uranium-238 Solution: Induced fission!

Chain Reactions

https://www.youtube.com/watch?v=vjqIJW_Qr3c

Energy Transformations- Water is heated by heat energy created through nuclear fission- Energy is lost to surroundings- Steam turns a turbine (heat energy transformed into kinetic energy)- Energy is lost to friction- Turbine powers a generator- Energy is lost to friction- Energy is transformed into electrical energy

Moderator & Control Rods

Moderator surrounds the fuel rods

Usually graphite or water.

Helps slow down the neutrons by having them collide with the atoms of the moderator

Control rods absorb excess neutrons

Can be removed/added as needed

Plutonium

Fast neutrons produced in a fission reaction may be used to bombard uranium-238 and produce plutonium-239

This isotope does not occur naturally

Plutonium (Cont)

Importance of these reactions is that non-fissionable material (uranium-238) is being converted to fissionable material (plutonium-239) as the reactor operates.

The plutonium-239 can be used as nuclear fuel in other reactors (or in nuclear weapons)

Problems with Nuclear Reactors

Radioactive waste hard to dispose of Major public health hazard should

‘something go wrong’ Problems associated with uranium mining

(radioactive dust particles) Possibility of producing materials for

nuclear weapons

Nuclear Fusion

It’s not yet possible to get more energy than is initially put into a fusion reaction.

Also at the high temperatures, plasma develops and must be kept in a magnetic chamber.

Problems

13 a, b