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Over the years a large number of rock samples were collected by the explorationists of Atomic Minerals Directorate for Exploration and Research (AMD), Department of Atomic Energy from Sambalpur district, Orissa, India. The variation of uranium enrichment with various types of rock in these samples was studied with an aim to help quick reviewing of toposheets in case of newly taken up areas, for uranium exploration. The radioelements U, Th and K determined for these samples are plotted in ternary diagrams for classifying them as being uraniferous or thoriferous with respect to various type of rocks, keeping the total natural content of radioelements (expressed by eU 3 O 8) as a parameter. In this study it is seen that samples of quartzofeldspathic breccia type are enriched in uranium irrespective of their further sub classification and eU 3 O 8 content. Granites are enriched in thorium when eU 3 O 8 < 100 ppm and are enriched in uranium when eU 3 O 8 > 100 ppm. A database prepared for this purpose may be useful for reviewing toposheets in future.

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Indigenously fabricated portable gamma-ray spectrometer (PGRS) is used for the measurement of gamma activity of 214 Bi (1.76 MeV) and 208 TI (2.62 MeV), under field conditions in Mohar area, Shivpuri Distt.(MP). The energies are discriminated by using a Nal (TI) crystal of size 1.75" × 2". PGRS used to map the primordial elemental distributions shows reversals of concentration of thorium and uranium (represented by radium group) in field and lab analysis in many samples, which is attributed to the inhomogenity of distribution of these elements in the area. The concept of difference in the volume of dish shaped field sample and the randomly picked up sample from the field grid point (400 gm in lab analysis) is utilized to interpret the inhomogenity of these elements. However interpretations are based on the assumption that these primordial elements (U, Th) are in secular equilibrium and the terrain has low topographic relief.