This work aims to understand the precipitation behaviour of nanoscale precipitates in 17-4PH grade martensitic stainless steel as a function of aging time and temperature.17-4PH is used in safety critical components in the chemical, oil and gas and nuclear industry but has driven concerns over the long term stability of the precipitate population. We propose to investigate the evolution of these precipitates using small angle neutron scattering (SANS) on a series of thermally aged samples. The information obtained from SANS, would be used to further understand the strengthening mechanism in steels and also to develop a nondestructive technique (NDT) using magnetic Barkhausen noise for detecting precipitate evolution and embrittlement in nuclear structural components as part of our involvement in the EU NOMAD horizon 2020 which aims at long-term operation of existing nuclear power plants.