Improved experimental evaluation and model validation of a 252Cf irradiator for delayed gamma-ray spectrometry applications.

We present experimental and MCNP modeled results of neutron flux monitoring in an irradiator, which consists of a252Cf sealed source housed in the center of a cubic block of high-density polyethylene. This work is contributing to our development in the delayed gamma-ray spectroscopy non-destructive assay technique for nuclear safeguards and security applications. We evaluated the thermal and resonance flux values using the Westcott foil activation method for two measurement position count rates of 197Au and 115In. Comparisons between the calculated thermal fluxes from measurements and those from MCNP models show deviations of ~20%. However, both the measured and modeled thermal fluxes are two orders of magnitude higher than the fluxes at the resonance peak energies at both measurement positions, demonstrating that the irradiator is sufficient. Furthermore, this work showed that with a252Cf sealed source of a strength of 4.4 × 106 n.s-1, a thermal flux in the range 2-5 × 104 n.s-1.cm-2 is achievable in our compact irradiator making it suitable for active analysis techniques such as DGS.