Knowledge of the melting of lead (shielding material) in enclosures is of great importance in the design of transportation packages. An experimental investigation is carried out to study the melting of lead contained in a stainless steel cuboid. The size of the cuboid is 50 mm x 50 mm x 60 mm. Side vertical wall is maintained at a constant heat flux boundary condition. Visualisation of solideliquid interface movement during melting of lead is carried out using neutron radiography at beamline E12 in CIRUS reactor in BARC. The beamline flux is 10⁶ Neutrons/cm² s. Neutron radiography is a non-intrusive method for the characterization of melt front of melting of opaque materials. This method demonstrates dynamic capture of the progress of solideliquid interface under the effects of natural convection in a non-intrusive manner. FLUENT is used as a numerical tool for the estimation of transient molten fraction and transient Nusselt number. Enthalpyeporosity method is employed for numerical investigation. Variation of molten fraction with time computed by numerical methodology compares reasonably well with those of experimental results. A correlation for average Nusselt number is suggested based on the numerical results and scale analysis.