On the Use of Thin Natural Uranium Film Dosimetry in Mineral Dating by the Fission Track Method

One important step of the experimental procedure used in the dating of minerals by the Fission Track Metod (FTM) is the thermal neutron irradiation of the mineral to be dated. Since the beginning of FTM, a well - accepted neutron dosimetry has not been found, being this matter intensively discussed in many papers. The employment of thin natural uranium films as neutron dosimeter is an opportune alternative because, in this case, only the U-235 (n.fission) reaction takes place both inside the dosimeter and the mineral to be dated. We observed that the thin uranium films made by us present uranium content (N',) that, is constant for N', ≥ 2 x 10" cm² and decreases with time for N', ≤10" cm². This fact imposes some restrictions to the direct employment of our fiIms as neutron dosimeters in FTM; however, they can be used indirectly, i e. to calibrate other natural uranium loaded dosimeters, like CN1 and CN2 Corning glasses , which are being crescently employed in FTM in the last years.