Performance of Accelerator Mass Spectrometry for I-129 using AgI-AgCl carrier-free coprecipitation

I-129 has been successfully applied as tracer in environmental, geological, and oceanographic research. For samples with low stable iodine concentration and ultra low level I-129, the sample preparation technique to separate iodine prior to AMS measurement has been a bottleneck, limiting the applicability of I-129 We have reported a carrier-free method, using coprecipitation, to avoid the potential introduction of I-129 through the use of stable iodine carrier iodine. In this work, the detection limit and the analytical uncertainty of this method are investigated and minimum sample amount required to obtain reliable analytical results are estimated. The method is validated with a series of samples in ranges of known iodine concentrations and I-129/I-127 ratios. The results confirm our previous conclusion that an AMS target containing 5.0 mu g iodine can be used for analyzing samples with I-129/I-127 &gt; 10(-12), and that for samples with I-129/I-127 &lt; 10(-13) more than 25 mu g iodine is necessary.</p

Analysis and environmental application of I-129 at the Xi'an Accelerator Mass Spectrometry Center

The newly established 3 MV Accelerator Mass Spectrometry (AMS) facility in Xi&#39;an, with an instrument background of 2 x 10(-14) for I-129/I-127 ratio, provides efficient analytical capability to carry out I-129 environmental tracing studies. Chemical separation methods of iodine from different types of samples have been established at the Xi&#39;an AMS Center, including solvent extraction and combustion followed by extraction or coprecipitation depending on sample types. A carrier free method for iodine separation and AMS measurement of ultra low level I-129 in samples with low total iodine concentration has been established, which can be used for analysis of geological samples for I-129 dating. Some environmental samples collected in China have been analyzed using the developed methods. The analytical results show I-129/I-127 ratios of (0.9-1.1) x 10(-10) for seawater collected adjacent to a nuclear power plant, and (3.02 similar to 5.43) x 10(-19) for soil samples collected in a less than 10 km area surrounding the NPP. These values are not significantly different from those measured in remote areas, reflecting a safe nuclear environment in terms of I-129 level.</p

I-129 level in seawater near a nuclear power plant determined by accelerator mass spectrometer

(129)I concentration in the seawater samples near a nuclear power plant was determined in the Xi&#39;an Accelerator Mass Spectrometer (AMS) Center. Isotope dilution method was used via addition of excessive amount of stable iodine ((127)I) in the sample before separation, and iodine in the seawater was separated by solvent extraction, and the back extracted iodine in iodide form was precipitated as Agl, which was used as AMS target for (129)I measurement. (125)I tracer was added to monitor the recovery of iodine in the whole separation process. (129)I/(127)I ratios in the prepared target were determined by AMS. The concentration of (127)I in seawater samples was determined by inductively coupled plasma mass spectrometry. The results show that the (129)I/(127)I atomic ratios in the seawater range from 8.29 x 10(-11) to 9.45 x 10(-10), approximately one order of magnitude higher than that in seaweed collected in the pre-nuclear era, but fall in the environmental level of global fallout.</p