Modelling a chain reaction in the classroom

Although there is no explicit requirement within the National Curriculum for England to teach about nuclear fission and chain-reactions, at least one board, the Northern Examinations and Assessment Board, does include this topic in its Science Double Award syllabus for 2001 and 2002: Nuclear reactors use a process called nuclear fission. When an atom with a very large nucleus is bombarded with neutrons: the nucleus splits into two small nuclei; further neutrons are released which cause further nuclear fission resulting in a chainreaction; the new atoms which are formed are themselves radioactive. (NEAB, 2001: 76).