How can the chain length of silicons be controlled during their synthesis?

In a nuclear reactor the chain reaction is carried out under controlled conditions. Name the material that is used as control rods in a nuclear reactor.

In a nuclear reactor the chain reaction is carried out under controlled conditions. Average energy of a neutron produced in fission of (^235_92)U nucleus is ..

In a nuclear reactor the chain reaction is carried out under controlled conditions. Write down the reactions involved in the conversion of (^238_92)U to (^239_92)Pu Put in a nuclear reactor.