Survey of environmental gamma radiation around Itu (Sao Paulo State, Brazil)

The measurement results of Itu intrusive suite natural radioactivity are presented. This regions consist of 4 granitic intrusive bodies, as determined through radiometric methods. The contour maps of K(%), U(ppm) and Th(ppm) concentrations of this region are plotted using Kriging grid method. From these concentrations and using the conversion factors, the outdoor air absorbed dose rates at 1 m from the ground are estimated and the isodose rate map presented. The 145 n Gy/h average value has been obtained, and the minimum and maximum values were respectively 28 and 381 n Gy/h. The maximum value was found near Itupeva city at NE of the Intrusive Suite. (author). 20 refs., 4 figs., 1 tab