This article describes the feasibility study performed at SCK-CEN on the Self-Interrogation Neutron Resonance Densitometry (SINRD). This non-destructive technique (NDA) is proposed for the safeguards verification of spent nuclear fuel and has the potential to directly quantify the 239Pu inside the fuel. Our approach is to insert a fission chamber in the central guide tube of a PWR 17x17 fuel assembly and to measure the neutron flux in the energy region close to the 239Pu resonance at 0.3 eV. The best measurement conditions are achieved when the fuel is standing in air and is surrounded by a thick layer of polyethylene. We identified the SINRD signature and we found that this ratio is sensitive mostly to the 239Pu content compared to other nuclides.