Simulation of induced three-fold coincidences with HEU shielded by cadmium and lead at different depths inside the 0.2 g.cm⁻³ iron cargo. The y position of HEU is the distance along the tagged neutron beam. The origin of the coordinate system (0, 0, 0) is the center of the cargo container and (0, −110, 0) is the position (in cm units) close to the container wall, near the neutron generator and detector panel 1 (see Fig. 34).