Since 2015, the Japan Atomic Energy Agency has been collaborating with the European Commission Joint Research Centre (EC/JRC) to develop active-interrogation non-destructive assay techniques. Of these, the JAEA Integrated Support Center for Nuclear Nonproliferation and Nuclear Security (JAEA/ISCN) has focused Delayed Gamma-ray Spectroscopy (DGS) development for verification of spent nuclear fuel. DGS utilizes neutrons to induce fission in nuclear material followed by a measurement of gamma rays emitted by the decaying short-lived fission products. The primary DGS capability is to evaluate the fissile nuclide composition using ratios of the gamma rays, but have also shown DGS can obtain the fissile mass. This work will describe the project status and prospects of our DGS development and analytic capabilities. We will highlight the expected capabilities and improvements for verifying spent fuel solutions and assemblies, as well as nuclear material of alternative fuel cycles.