Neutron diagnostics of the premises of the destroyed unit at the Chernobyl nuclear power plant by use of CR-39 track detectors and boron converters

Neutron detectors containing boron as a converter, CR-39 plastic as a track detector and water as a neutron moderator have been applied for the neutron diagnostics of the premises of the destroyed unit at the Chernobyl nuclear power plant. Theoretical (3.8 x 10-2 tracks per neutron) and experimental (5.1 x 10-3 tracks per neutron) assessments of the detector sensitivity to thermal neutrons were carried out. Values of the neutron flux density within a range of 1-92 neutrons cm-2 s-1 were detected on the premises of the destroyed unit. It is assumed that the (α, n) reactions for oxygen and spontaneous fission are the most effective fast neutron sources within the unit. (author)