Primary result of ~(236)U measurement with accelerator mass spectrometry at CIAE

The rare isotope ~(236)U has a half-life of 2.342(3)×10~7 years, and is produced principally by thermal neutron capture on ~(235)U. The isotopic atom ratio of ~(236)U/~(238)U depends on the integral thermal neutron flux received by the material of interest. ~(236)U is potentially useful as a "fingerprint" for indicating the presence of neutron-irradiated uranium usually originating from nuclear activity. By extracting negative molecular ion UO~- from the uranium oxide target, simulating the ~(236)U~(16)O~- beam transport with ~(238)U~(16)O~- and ~(208)Pb_2~(16)O~- pilot molecular ion beam, transporting the ~(236)U-containing ion beam with a high resolution injection magnet analyzer and electrostatic analyzer system, and finally identifying and detecting ~(236)U with a time-of-flight detector (TOF), a method for AMS (Accelerator Mass Spectrometry) measurement of ~(236)U was established on the HI-13 Accelerator AMS system at China Institute of Atomic Energy.