Q2 Fig 22.27 shows the basic structure of a nuclear reactor. (i) What is meant by fission? (6)
Shielding
(ii) Describe how a chain reaction occurs in the fuel rods. (9)
(iii) Uranium-235 undergoes fission when struck slow neutrons, barium-141 and krypton-92, nuclei are emitted along with three neutrons.Write a nuclear reaction to represent the reaction. (12)
(iv) A nuclear reactor contains (i) control rods, (ii) moderator, (iii) heat exchange. Give the function of any two of these.
Fuel rod Moderator Coolant Fig 22.27
(v) What is the purpose of the shielding? Name a material that is used as shielding. (vi) Give one advantage and one disadvantage of fission reactors as a source of energy. (vii) Give two precautions that should be taken when storing radioactive materials.
Q3 What is radioactivity? Certain isotopes are more radioactive than others.What are isotopes?
One such radioactive material is Radium-219, whose chemical symbol is . Radium-219 is an alpha emitter, decaying into polonium.The isotope of polonium in this decay chain is itself unstable and can decay into astatine-215.
219Rn 86
(i) What do the numbers 86 and 219 represent in the symbol for Radium-219? (ii) Write down the equation to represent this decay of radium into polonium. (iii) What type of emission allows polonium to transmutate into astatine? Describe an experiment to demonstrate the ionising effect of radioactivity. Give two practical applications of radioactivity.
(6) (9) (4)
(12) (6)
Name an instrument used to measure radioactivity. Describe the principle of operation of this instrument. (7)
Q4 The Sun is currently the only fusion reactor we make practical use out of. All manmade nuclear-powered generators are based on fission rather than fusion. There are efforts being made by physicists worldwide to build nuclear power plants using fusion reactors. Even though it has thus far proved uneconomical to produce energy using fusion-powered generators, many fusion reactions have been carried out. In one of the reactions, two isotopes of hydrogen (deuterium which has an atomic mass of 2 and tritium with an atomic mass of 3) combine to form one isotope of helium with the release of one neutron.
