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Fri Aug 9, 2019, 12:38 PM

Determining 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:

Iodine is an essential trace element of mammals. Iodine deficiency can result in irreversible neurological damage and developmental retardation in newborns. The major source of iodine in the terrestrial environment is from atmospheric deposition.(1) Atmospheric iodine has a significant impact on climate through tropospheric ozone depletion and aerosol formation and was observed several times change in recent decades.(1−3) Although some investigations have been carried out by measuring iodine in soil, sediment, and ice cores,(3,4) the sources, transport pathways, and transfer processes of atmospheric iodine in the ecosystem are still not well understood due to its multisources and the difficulties on discrimination of its different sources.

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:

...The Qinghai-Tibet plateau (QTP) has an average altitude of 4000 m and a cold ecosystem with widely distributed permafrost; (19) it is therefore quite sensitive to environmental changes. Meanwhile, this region is also important for the climate and ecosystem of a large area in the world because it acts as the largest fresh water reservoir in Asia including over 2 ื 1011 m3 of glacier resource, 3 ื 1010 m3 of annual runoff, and 1800 lakes. In 1964–1980, 22 atmospheric nuclear tests with the total yield of 22.72 Mt of TNT were conducted at the Lop Nor NWTs site in Northwest China.(20) Due to the prevailing westerlies at Lop Nor, the released 129I from the atmospheric nuclear weapons tests at this site might be transported to the QTP which is located in the 1100 km downwind area of Lop Nor.

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:

Figure 1. Wood disks of PC1 tree (top) and PC2 tree (bottom), showing the annual rings.


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:

Figure 2. Comparison of measured 127I concentrations (a) and 129I/127I ratios (b) in the tree rings in this work with the reported values in other locations.(16,17,23,24)


Ratios recorded with events and practices:



The caption:

Figure 3. Temporal variation of the measured 129I/127I ratios in the tree rings from two sites in the QTP (a, b), in comparison with the reported variation of 129I/127I in atmospheric fallout from Tokyo (a),(27) yield of fission NWTs (c), yield of thermonuclear weapons tests at Lop Nor (d),(20) air releases of 129I from major NFRPs (e), and marine discharges of 129I from NFRPs (f).(33)


Comparison with iodine in Greenland:



The caption:

Figure 4. Variation of iodine (127I) concentration in PC1 and PC2 trees (a), in comparison with the temporal variation of iodine concentrations in ice core in Greenland (b).(3)


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:

A peak of 129I/127I ratios covering 3 years in 1986–1988 ((14.6–18.4) ื 10(9)) in PC1 and 2 years in 1986–1987 ((12.7–13.8) ื 10(9)) in PC2 was observed. Since atmospheric NWTs ceased from 1980 along with the almost steady discharges of 129I from the main NFRPs (air: 13–14 kg/y; marine: 70 kg/y), this might be attributed to the Chernobyl accident on 26th April 1986 with 1.3–6 kg 129I released to the environment.(33) The Chernobyl accident derived radioactive fallout had dispersed to north China through the westerlies, and the level decreased from the northwest toward the east and south.(46) The total β activity in atmospheric fallout collected in Urumchi (1400 km in the northwest of sampling sites, 43ฐ N) and the short-lived radioactive 131I activity in milk were observed to elevate over 50 times compared to the background value.(46,47) A 15-times elevation of the total β activity was also measured in atmospheric fallout in Xi’an (600 km to the east of sampling sites, 33ฐ N).(47) Although no direct monitoring of radioactivity data after the Chernobyl accident is available from the sampling site, it should have received the Chernobyl derived 129I because the sampling site is located between Xi’an and Urumchi. The Chernobyl derived 129I/127I peak was even observed in sediment samples from Jiaozhou Bay in a similar latitude but 1600 km east of the study area.(7) A broad 129I peak in both tree ring profiles (PC1: 3 years; PC2: 2 years) might be contributed to the re-emission of the deposited 129I in the high contaminated soil to the atmosphere in the following 2–3 years.


Fukushima:

No significantly increased 129I/127I value was observed in 2011 (7.1 ื 10 ) compared to 6.9 ื 10 in 2012 and 5.2 ื 10 in 2010 in PC1 rings, indicating an insignificant contribution from the Fukushima accident with about 1.2 kg 129I releases (including 0.35 kg direct marine discharge).(7) The atmospheric releases from the Fukushima accident mainly dispersed eastwards and deposited in the North Pacific Ocean, and the marine discharges including 129I were mainly transported eastwards by the North Pacific current.(48) Although some radionuclides (mainly 131I, 137Cs, and 134Cs) in aerosol samples collected in North China after Fukushima were measurable, the level is much lower compared to those in North America and Europe and at least 2 orders of magnitude lower than that from Chernobyl.(49−51) Therefore, the contribution to the study area is negligible.


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.






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