Radiometric analysis of U3O8 in 140 tonne capacity haultrucks

At the Roessing uranium mine, radiometric analysis of 140 tonne capacity haultrucks is carried out in the pit area by large mobile truck scanning installations employing NaI(TI) scintillation detectors to provide immediate selectivity between loads defined as either ore or waste. The conversion factor from a radiometric count to a U3O8 grade was established initially by comparison with the XRF mill feed grade analyses over a period of one month. The system is analysed with respect to both physical sources of error, such as are introduced by the detection system, sample representation effects, the role of disequilibrium, and mineralogical effects such as the role of Th and K contamination. This analysis indicates, with respect to providing a degree of grade analysis for the total feed material, that an ultimate accuracy of a few percentiles should be obtained. This is shown to be the case in practice by virtue of the comparison between radiometric truck scanning data and mill feed data taken over a period of two years. The radiometric truck scanning system therefore represents a facility and monitoring system which is potentially far more useful than originally conceived