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In terms of how they interact with the neutrons in a fission reactor, distinguish between a moderator and a control rod. - Leaving Cert Physics - Question (i) - 2021
Question (i)
In terms of how they interact with the neutrons in a fission reactor, distinguish between a moderator and a control rod.
Worked Solution & Example Answer:In terms of how they interact with the neutrons in a fission reactor, distinguish between a moderator and a control rod. - Leaving Cert Physics - Question (i) - 2021
Step 1
Moderator
Answer
A moderator is a substance in a fission reactor that slows down neutrons, increasing the probability of further fission reactions. By reducing the speed of the neutrons, the moderator allows them to be captured more easily by fissile material, such as uranium-235 or plutonium-239. Common materials used as moderators include water, heavy water, and graphite.
Step 2
Control Rod
Answer
A control rod, on the other hand, is designed to absorb or stop/block neutrons. Control rods are made from materials such as boron, cadmium, or hafnium, which have high neutron absorption cross-sections. By inserting or withdrawing control rods from the reactor core, operators can regulate the fission reaction and maintain safety by controlling the reactor's power output.