The first Indian research reactor, APSARA, was uti lized for various R&D programmes from 1956 until its shut down in 2009. The biological shield of the reactor developed residual activity due to neutron irradiation during the operation of the reactor. Dose rate mapping and in-situ gamma spectrometry of the concrete structures of the reactor pool were carried out. Representative concrete samples collected from various locations were subjected to high-resolution gamma spectrometry analysis. ⁶⁰Co and ¹⁵²Eu were found to be the dominant gamma-emitting radionuclides in most of the locations. ¹³³Ba was also found in some of the concrete structures. The separation of ³H from concrete was achieved using an acid digestion method and beta activity measured using liquid scintillation count ing. The depth profile of radionuclide spe cific activity in the concrete wall of the shielding corner was also studied. Specific activities of the radionuclides were found to de crease exponentially with depth inside the concrete walls. This study would be helpful in bulk waste management during the decommissioning of the reactor.