Describe the construction and working of a nuclear reactor with a labelled diagram.
How to lay out the answer. Follow the frame, then write it in your own words.
1 · Define it. A device that keeps a controlled, self-sustained fission chain reaction going to produce heat.
2 · Describe the core. Fuel rods of uranium in a moderator (heavy water or graphite), with control rods of cadmium or boron.
3 · Give each job.
Moderator slows neutrons
Control rods absorb extra neutrons
Coolant carries heat away
Reflector returns escaping neutrons
4 · Describe the power cycle. Hot coolant boils water in a heat exchanger; steam spins a turbine and generator; a condenser returns the water.
5 · Draw the reactor. [Diagram: core with fuel rods, moderator and control rods inside a concrete shield; coolant loop with pump to heat exchanger; steam to turbine, generator and condenser]
6 · Describe the safety features. Steel pressure vessel, thick concrete shield and an air-tight building.
7 · Real life. India's PHWRs use natural uranium with heavy water as moderator and coolant.
8 · Close in one line. So, fission heat is turned into electricity just as coal heat is in a thermal power station.
Scoring tip: The diagram carries a big share of the 5 marks: label the fuel, moderator, control rods, coolant, heat exchanger, turbine and shield.
