Airborne emission of enriched uranium at Tokai-mura, Japan

A new strategy for characterisation of airborne uranium contamination based on elemental/isotopic analysis of tree bark is described. Bark samples col lected at Tokai-mura (Japan) were subjected to high sensitivity ICP mass sp ectrometric analysis; for control purposes, samples from the remote Yakushi ma island (Southern Japan) and central Tokyo were also analysed. The uraniu m contents of tree bark for Tokyo and Yakushima were of similar magnitude t o that at Tokai-mura (U, 0.01-1.0 mug/g - all samples), however, there were marked differences in isotope ratio values between the sites. Whereas natu ral uranium isotope ratio values (U-235/U-238, 0.0072) were observed for Ya kushima and Tokyo, non-natural and natural signatures (U-235/U-238, 0.00697 -0.01448) were realised at Tokai-mura. These findings are consistent with t he release of enriched uranium at Tokai-mura. (C) 2001 Elsevier Science B.V . All rights reserved.