Neutron self-shielding in hydrogenous samples

Measurements performed in the past to determine sensitivity enhancements (later identified as neutron density increases) in PGNAA as a function of hydrogen concentration in slab-shaped samples are described. The results are compared to the results of Monte Carlo computations. It is concluded that, like H2O, D2O can also cause substantial neutron density increases. In one concentrated salt solution, however, D2O seems to cause a neutron density decrease that cannot be explained from the macroscopic neutron scattering and absorption cross sections in the model used.