Reactor critical extrapolation monitoring system and method

A critical extrapolation monitoring system and method for a reactor belong to the technical field of reactors. The system comprises two neutron source components which are loaded in a reactor core and are symmetrically distributed, a first source range neutron detector and a second source range neutron detector which are arranged close to the neutron source components, and a third source range neutron detector and a fourth source range neutron detector which are arranged far away from the neutron source components. The method comprises the steps of carrying out critical safety supervision based on the counting rates of the first source range neutron detector and the second source range neutron detector when the reactor core is in a deep subcritical state; along with the introduction of the positive and negative reactivity operation into the reactor core, the subcritical degree is continuously reduced, and after the third source range neutron detector and the fourth source range neutron detector have effective counting rates, critical safety supervision is carried out based on the counting rates of the first source range neutron detector, the second source range neutron detector, the third source range neutron detector and the fourth source range neutron detector; and when the reactor core reaches a critical state, stopping introducing the positive reaction operation to the reactor core. The invention can effectively monitor the critical safety of the reactor core, can more accurately predict the critical state of the reactor core and ensure that the reactor can safely and controllably reach the critical state.