Iodine-129

Iodine-129 (129I) is a long-lived radioisotope of iodine that occurs naturally but is also of special interest in the monitoring and effects of man-made nuclear fission products, where it serves as both a tracer and a potential radiological contaminant.

[3] At least for civil reprocessing plants, special scrubbers are supposed to withhold 99.5% (or more) of the Iodine by adsorption,[3] before exhaust air is released into the environment.

"[3] The Northeastern Radiological Health Laboratory further states that, due to limitations of their measuring systems, the actual release of 129I may have even been higher, "since [129I] losses [by adsorption] probably occurred in the piping and ductwork between the stack and the sampler".

Military isolation of plutonium from spent fuel has also released 129I to the atmosphere: "More than 685,000 curies of iodine 131 spewed from the stacks of Hanford's separation plants in the first three years of operation.

"[11] As 129I and 131I have very similar physical and chemical properties, and no isotope separation was performed at Hanford, 129I must have also been released there in large quantities during the Manhattan project.

As Hanford reprocessed "hot" fuel, that had been irradiated in a reactor only a few months earlier, the activity of the released short-lived 131I, with a half-life time of just 8 days, was much higher than that of the long-lived 129I.

Ice borehole data obtained from the university of Bern at the Fiescherhorn glacier in the Alpian mountains at a height of 3950 m show a somewhat steady increase in the 129I deposit rate (shown in the image as a solid line) with time.

In particular, the highest values obtained in 1983 and 1984 are about six times as high as the maximum that was measured during the period of the atmospheric bomb testing in 1961.