A system for the prediction and determination of the subcritical multiplication condition

In this paper a system is described that allows to calculate and predict th e subcritical multiplication condition of a nuclear reactor The system is d ivided into two different modules. The first module enables the calculation of the subcritical multiplication factor (1/M) from the data acquired by t he neutron detectors of the external nuclear detection system. The second m odule, based on the solution of the multigroup diffusion equation, allows t he theoretical prediction of the subcritical multiplication factor which is useful to anticipate the 1/M factor. The system is a very important tool t hat helps the operators during the start-up of a nuclear power reactor.