A neutron detector module comprising a distribution of proportional counters positioned in a defined array. Each of the proportional counters includes a supply of a neutron sensitive gas for reacting with neutrons, and this reaction generates ionizing reaction products. The proportional counters include a multitude of tubes, and each of the tubes has a diameter between 0.50 inch and 1.00 inch. The neutron detector module comprises further a multitude of electrical conductors; and each of the conductors is positioned in one of the proportional counters, and the ionizing reaction products generate electric current pulses in the electrical conductors.