What is the exact role of delayed neutron in reactor operation?
Crucial role of delayed neutron: Prompt neutrons have a lifetime of ms. They grow exponentially once fission starts. We need to control it, otherwise reactor will reach supercritical state. It can be controlled by using control rod. But control rods cannot be inserted within fraction of second or within a second. But within a second the no. of neutron shall increase dangerously. If control rod is inserted before starting the fission, chain reaction shall not be able to reach criticality (if there is only prompt fission neutron).