Natural uranium needs to be enriched to increase the proportion of ²³⁵U. Suggest a technique that would determine the relative abundances of ²³⁵U and ²³⁸U.

Explain how ²³⁵U fission results in a chain reaction, including the concept of critical mass.

Suggest one reason why there is opposition to the increased use of nuclear fission reactors.

mass spectrometry/mass spectroscopy/MS

Accept “analysis of radiation emitted”.

[1 mark]

critical mass: mass required so that «on average» each fission/reaction results in a further fission/reaction

Any two for [2 max]:

neutron captured by «²³⁵U» nucleus

fission/reaction produces many neutrons/more than one neutron

if these cause further fission/reaction a chain reaction occurs

Accept “minimum mass of fuel needed for the reaction to be self-sustaining”.

Accept answers in the form of suitable diagrams/equations.

[3 marks]

produce long lived/long half-life radioisotopes/radioactivity

OR

could be used to produce nuclear weapons

OR

«nuclear» accidents/meltdowns can occur

Accept “long lived/long half-life radioactive waste”.

[1 mark]