1. IP2.31.4 Nuclear fission © Oxford University Press 2011 Nuclear fission

2. IP2.31.4 Nuclear fission © Oxford University Press 2011  Nuclear fission is the splitting of an atomic nucleus.  Currently all nuclear reactors work by nuclear fission.  Either uranium 235 or plutonium 239 nuclei are split into two smaller nuclei.  The process generates heat energy which is used in the same way as a conventional thermal power station. The heat is used to produce steam which turns turbines, which then turn generators.  The products of fission are usually radioactive. Radioactive waste is one of the major drawbacks of fission reactors.

3. IP2.31.4 Nuclear fission © Oxford University Press 2011  Most reactors use uranium 235.  The uranium nucleus absorbs a neutron and then splits into two smaller nuclei and releases 2 or 3 more neutrons.  These neutrons are then absorbed by other uranium nuclei causing them to split.  This process continues and is called a chain reaction. This is because the reaction is self-sustaining – the neutrons from one reaction cause another reaction to take place forming a link or chain between the reactions.