Preliminary Investigation on the Rapid and Direct AMS Measurement of I-129 in Environmental Samples without Chemical Separation

摘要

Accelerator mass spectrometry (AMS) is the most sensitive method for measuring I-129 in environmental samples available today, with a detection limit of about 10(-15) for I-129/I-127. A drawback of the technique is the time-consuming chemical separation required to prepare AMS targets from raw samples. This step significantly limits applications requiring rapid analyses and large numbers of samples, for example, in monitoring studies associated with nuclear accidents. This work introduces a direct method for I-129 measurements by AMS that does not require chemical separation. In this approach, stable iodine (I-127) is added to a matrix of niobium (Nb) powder and mixed with dried raw sample. This mixture is pressed directly into a sputter target for AMS analysis. Two types of environmental samples have been tested in this work, seaweed and sediment. No anomalous behavior was noted in the Cs+ sputtering behavior of the targets prepared from these materials. The I-129/I-127 ratios and I-129 concentrations measured by this rapid method were found to be in agreement with reported values that used a conventional AMS method for the same material. Based on our findings, we expect that such rapid measurements can be applied to a wide variety of materials, in addition to seaweed and sediment, as long as the sputtering-induced adverse effects do not prevent the stable operation of the ion source. The method is especially useful for screening large numbers of samples before more precise analyses are made.