Experimental determination of uranium and thorium in Allchar ore

In addition to its production in the 205Tl(ν,e-)205Pb reaction 205Pb can be produced in the Allchar mine by other reaction chains which are initiated by cosmic rays, and by alpha particles from the decay chains of uranium and thorium present in the lorandite and other ores found in the mine. We have measured the uranium and thorium concentrations in lorandite, realgar and marcasite samples from the mine by observing fission fragments produced in neutron induced fission. The fragments were recorded in Makrofol KG film and the measurement technique has a good level of sensitivity. Excellent discrimination against other radiations is obtained. (orig.)