Active neutron measurements on fissile material solutions in the presence of heterogeneous and homogeneous neutron poisons

In connection with the necessity of nuclear materials safeguards the first extraction column (HA column) represents a system component of special importance. It allows the advantageous application of neutron monitoring methods for the detection of fissile material, as neutrons can be detected practically unperturbed even in the presence of the strong γ fields in the HA range. In a test set-up for studies on in-line instrumentation allowing the safe dealing with fissile solutions and a strong neutron source, a large-scale measuring programme was executed with a neutron monitoring set-up installed in an α box and completed in 1987 with a reference measurement on uranium-free nitric acid. The measurement principle, experimental programmes and results are described. (orig./RB)