Science
Related: About this forumDetermining the Flux of Anthropomorphic Iodine From Nuclear Power Plant Radioiodide Releases.
The paper I'll discuss in this post is this one: Atmospheric Iodine (127I and 129I) Record in Spruce Tree Rings in the Northeast Qinghai-Tibet Plateau
Only two elements in the 5th period of the periodic table are essential to life, Molybdenum, because of its role in nitrogen fixation enzymes, and iodine.
The overwhelming bulk of fission products produced in nuclear reactors, from natural spontaneous decay of terrestrial uranium, and nuclear weapons tests, are in the 5th period of the periodic table which stretches from rubidium to xenon. In the 4th period only selenium, bromine, and krypton are present in appreciable amounts, and the radioactivity associated with only one of these three elements is of any concern - bromine in used nuclear fuel is not particularly different than natural bromine, and selenium-79 is produced in very low yields; the isotope of "concern" being krypton-85. (In general, "concern" about nuclear materials can border on Trumpian scale stupidity; the loss of life from commercial radioactivity is dwarfed by the loss of life from things nuclear energy can easily replace. In the 6th period, cesium and barium and the first half of the lanthanides (up to around gadolinium) are significant fission products, but again, the bulk of fission products are 5th period elements.
Molybdenum, really a wonderful element, when obtained from used nuclear fuel after a few weeks of cooling is not particularly different than mined molybdenum and although the high energy to mass ratio of nuclear fission means that commercial quantities of this element obtained from used nuclear fuel will never be significant, there is no particular reason that it couldn't be utilized for normal commercial uses.
Natural iodine is mostly the stable I-127 isotope, this isotope being the only stable isotope. Iodine-131, has a short half life, about 8 days, meaning that its release to the environment is generally a serious matter, since it has a high specific activity. This isotope was of significant concern in the Chernobyl and Fukushima events, since iodine is a volatile element which is easily transported in the environment. The high activity of I-131 is also exploited for medical use, ironically most prominently in the treatment of thyroid cancer and certain hyperthyroid conditions.
Iodine also has a relatively long lived isotope, I-129, which has a half-life of 15.3 million years, an isotope is naturally present in the environment from the spontaneous decay of natural uranium (primarily in the oceans), but whose presence in the environment has risen significantly, largely because of the reprocessing of used nuclear fuels in Europe, an activity which, by the way, I enthusiastically support although it is subject to huge processing improvements.
From the cited paper's introduction:
129I, a long-lived radioisotope of iodine (T1/2 = 15.7 Ma), has been released to the environment by human nuclear activities, including nuclear fuel reprocessing plants (NFRPs), nuclear weapons tests (NWTs), and nuclear accidents (NAs). The anthropogenic 129I (NFRPs: 7400 kg; NWTs: 150 kg; NAs: 7.2 kg) has highly overwhelmed the natural inventory in surface environment (250 kg, with a prenuclear 129I/127I atomic ratio of 1.5 × 10^(12)).(5,6) Due to the unique source of anthropogenic 129I, volatile properties and biophilic characteristics of iodine, the anthropogenic 129I has been widely applied as an environmental tracer for investigation of regional radioactive sources and the related atmospheric transport pathways by determination of 129I preserved in time-serial samples (sediment, ice core, and coral samples).(6−12) However, due to the insufficient resolutions of sediment samples caused by low deposition rates in many locations, the sampling difficulties, and specified locations of ice cores and coral samples, they are not sufficient for the investigation in large areas, especially in midlow latitude terrestrial environments.
Tree ring is an excellent time-serial material to monitor past climate changes as well as anthropogenic activities due to its wide distribution, easy access, annual resolution, accurate chronology, and environmental sensitivity,(13) which might preserve the environmental radioactivity information both in the prenuclear and nuclear age and in different locations. Dendrochemistry based on stable isotopic composition and elements concentrations in annual rings as retrospective proxy data has been successfully used to investigate the past environmental change, such as past temperature and precipitation (δ18O, δ13C, etc.),(13) and the anthropogenic release of toxic elements to the atmosphere (Pb, Cd, Hg, etc.)...
From this text we can see that the bulk of I-129 released into the environment, estimated to be about 7.4 tons, comes from the rerprocessin of nuclear fuels.
By the way, this radioactive iodine has more or less been deliberately released to the environment to save money, which in my opinion is probably a good thing, since it very unlikely that spending money to contain it forever would save lives, since it is very unlikely that the release of iodine-129 has killed anyone, but even if I am wrong, and it has killed someone, the ratio of the number of people killed by such releases is dwarfed by the number of lives saved because dangerous fossil fuel waste was not released. It is immoral and stupid to argue that spending millions upon millions of dollars to save one or two lives, whether or any lives lost are subject to irrational fetishes, is worthwhile when the same amount of money spent otherwise could save thousands of lives.
In any case, the anthropomorphic release of I-129, as the authors note, is an excellent tracer.
Later in the introductory text they note:
This work aims to investigate the sources, transport pathways, and transfer of atmospheric iodine in the QTP by determining 127I and 129I in tree rings of spruce. The feasibility of using tree rings of spruce to record the temporal variation of iodine isotopes in the atmosphere will be investigated in order to obtain a historic record of 129I and 127I levels in the atmosphere; this is useful for reconstruction of the levels of radioactive fallout and providing a fundamental database for regional environmental change research.
(Lop Nor is the site of the Chinese nuclear weapons test site; China was one of the last countries to conduct open air nuclear weapons tests.)
The analytical portion of the text is quite interesting inasmuch as it says something about radioactivity and iodine. Because the half-life of I-129 is so long, and thus its specific activity so low, and because the ratio of it to naturally occurring (and essential iodine is so low, parts per ten billions) the I-129 is not detected by its radioactivity but rather by the use of a very sensitive mass spectrometer, the Agilent 8800 ICP/MS. These instruments have sensitivity on the order of parts per trillion, as well as a wide dynamic range, meaning that they can easily pickup the signals of iodine-129 and iodine-127 without too much difficulty.
This demonstrates why the release of I-129 is a trivial matter from a human (and animal) health perspective.
Some pictures from the paper:
The caption:
The total iodine in the tree species in each year represented by a tree ring and the ratio of radioactive iodine to stable iodine:
The caption:
Ratios recorded with events and practices:
The caption:
Comparison with iodine in Greenland:
The caption:
Some comments on those nuclear accidents that raise such a bugaboo, even though the massive death toll from the normal operations of dangerous fossil fuel plants, don't even justify a fart's worth of intelligence:
Chernobyl:
Fukushima:
Now, in my position, as a person who claims that nuclear energy and only nuclear energy is sustainable enough to address climate change and the massive death toll associated with dangerous fossil fuel waste, I am sure that some of what is written above will upset a certain set of people who actually are not even knowledgeable enough about nuclear issues to know how much knowledge they actually lack on the subject, but my purpose is not to address these people, since they are clearly beyond hope.
For the record, I believe there is good reason to recover iodine from used nuclear fuels, assuming that we can get more used nuclear fuel, something which, in my view, as a scientist, is an urgent imperative for humanity to accomplish, which is not to say that humanity is wise enough, collectively to do so. Ignorance is more powerful than it has been at any time in the last 70 years, and the situation is getting worse not better.
By the way, the authors have determined that the flux of anthropomorphic natural iodine has increased significantly in the last half a century, apparently by an order of 3. There's no surprise there. If anything marks our generation, it is our profligate use of the elements in the periodic table, with no regard whatsoever for the needs of future generations.
I wish you a pleasant weekend.