In which section of a nuclear reactor does nuclear fission occur? a. reactor vessel b. heat exchanger c. condenser d. cooling tower

Option A, Reactor vessel

Explanation:

The components of nuclear plant have following function –  

a)Heat Exchanger – A heat exchanger allows heat transfer between two liquids without establishing any contact between them

b)Condenser -  A condenser is a cooling unit where a hot gas is converted into liquid

c)Cooling tower – They are used to transfer heat that has been generated during different process of nuclear power plant to atmosphere

d)Nuclear reactor vessel – The fuel rods are placed inside the nuclear reactor immersed in some liquid to carry out nuclear  fission reaction.  

Thus, option A is correct