STUDY ON EXTRACTION-2 IN ACCELERATOR MASS SPECTROMETRY MEASUREMENT OF 236U.

This study extracts UF2- ions from UF4 sample material for the first time so as to improve the measurement accuracy and sensitivity for accelerator mass spectrometry (AMS) measurement of 236U. Compared to the commonly used UO-/U02 (or U308) combination, the UF2-/UF4 approach brings a higher beam current of extracted U-containing ions and lower interference from U isotopes (235U in particular). The UF4 prepared with the procedures developed in this work can provide a higher ratio of F-/O- and therefore lower interference from O-containing 235 U and 238 U molecular ions, compared with that from the UF4 made by conventional liquid-phase reaction. The AMS experiment was carried out on. the AMS system at China Institute of Atomic Energy (CIAE), where only a simple surface barrier detector was used to record ions and a reference 236U sample with a 236U/238 U ratio of 10-10 was analyzed. The result shows that the measurement sensitivity of the UF2-/UF4 approach is lower than 10-10 and that the reference 236U sample result is in agreement with the reference value within the uncertainty limits, with the relative uncertainty only 4%. In comparison, the measurement sensitivity of the UO-I U308 combination approach is 10-9 and it cannot give a concrete value for the same reference sample using the same AMS system. If the sophisticated 500-ps-resolution time-of-flight detection system is used in combination with the UF2-/UF4 approach, a sensitivity of 10-13 (or lower) is expected. [ABSTRACT FROM AUTHOR]