Nuclear Technology / Volume 182 / Number 2 / May 2013 / Pages 235-241
Regular Technical Paper / Special Issue on the Symposium on Radiation Effects in Ceramic Oxide and Novel LWR Fuels / Reprocessing
This study extracts UF-2 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-/UO2 (or U3O8) combination, the UF-2/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 235U and 238U 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/238U ratio of 10-10 was analyzed. The result shows that the measurement sensitivity of the UF-2/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- /U3O8 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 UF-2/UF4 approach, a sensitivity of 10-13 (or lower) is expected.