236U in uranium minerals and standards

We have recently extended our accelerator mass spectrometry (AMS) system to the detection of actinides for geophysical applications, taking U-236 as an interesting test case for this class of nuclides. We report on the development of the experimental setup and on preliminary measurements of U-236 in minerals and uranium standards. The isotopic abundance sensitivity is 1 x 10(-11). The natural U-236 abundance of five U-rich minerals were measured to be between 1 and 33 x 10(-11). U-236 is expected to be produced in situ by neutron capture on U-235. Three uranium standards material were measured and showed a large U-236 contamination. (C) 2000 Elsevier Science B.V. All rights reserved.