Direct search for primordial 244Pu in Bayan Obo bastnaesite

Abstract

The abundances of heavy elements produced in r-process nucleosynthesis in the early solar system need experimental verification. 244Pu could be the heaviest primordial nuclide produced before the formation of the Earth still being detectable today. As recent attempts failed to confirm the discovery of 244Pu signals at a concentration of 1.0 × 10−18 g/g in bastnaesite reported by Hoffman et al. in this study, the total primordial 244Pu in 450 g bastnaesite sample from Bayan Obo ore (China) was measured using ultra-sensitive compact accelerator mass spectrometry (AMS). As no 244Pu signal was detected, an upper limit for the 244Pu in our bastnaesite sample was estimated to be 2.1 × 10−20 g/g at 99% confidence level.