ABSTRACT
We have seen that, if the neutron multiplication factor of a reactor assembly keff < 1, the chain reaction cannot be sustained. However, if a source of neutrons is introduced inside the multiplying medium, the initial neutron number is multiplied by a factor which can be very large. Since neutrons are associated with an equivalent number of fissions, a large energy could be produced with a subcritical system, provided a neutron source is available.
