The local area distribution and relocation of radioactive cesium deposited in trees after the 2011 tsunami-related accident at the Fukushima Daiichi Nuclear Power Plant (FDNPP) have been studied by measuring the spatial distribution of cesium on/in trees by autoradiography analysis. Samples of trees were collected from places located between 4 and 55 km from FDNPP approximately 2, 8, 20, and 22 months after the accident. The autoradiography analyses of Cryptomeria japonica, Torreya nucifera, and Thujopsis dolabrata var. hondae samples collected approximately 2 and 8 months after the accident showed that radioactive Cs was mainly distributed as spots on the branches and leaves of the trees emerged before the accident, and was detected in negligible amounts in new branch and leaves that emerged after the accident. On the contrary, radioactive Cs was detected at the outermost tip of the branches in the trees collected 20 months after the accident. Morus alba samples collected 22 months after the accident contained radioactive Cs inside and outside their stems, even though no radioactive Cs was detected in their roots, strongly suggesting that a certain amount of radioactive Cs was translocated from the outside to the inside of stems. These results indicate that the distribution of radioactive Cs deposited on/in the trees gradually changes with time (scale: year).
Radon therapy has long been performed for pain- and oxidative-stress-related diseases in Bad Gastein (Austria) and Misasa (Tottori). We carried out some animal experiments to clarify the mechanism underlying the effects of the therapy. The findings indicated that radon inhalation has antioxidative effects. For example, radon inhalation suppressed liver functional disorder and oxidative damage following carbon tetrachloride administration in mice. In addition, the anti-inflammatory effect through the enhancement of the antioxidative function, which suppresses inflammatory pain, was also obtained. From these findings, the possibility of health promotion by radon is suggested.
A newly developed liquid waste treatment system using an “emulsion flow” extractor has been applied to actual uranium-containing liquid wastes that originated from the decontamination of used gas centrifuges at Ningyo-toge Environmental Engineering Center of Japan Atomic Energy Agency. The emulsion flow extractor performs efficient liquid-liquid extraction by supplying solutions without additional stirring or shaking. The solvent used in this system is an isooctane solution containing TnOA and 1-octanol, which is effective in the selective extraction of uranium, without the formation of the third phase, from dilute sulfuric acid solutions containing a large amount of Fe. With the use of this system, 90% or more of uranium is extracted from actual and simulated decontamination liquid wastes under such mild emulsion flow conditions that fine drops of organic phases do not leak outside the apparatus.
In the Fukushima-Daiichi nuclear power plant accident, a large amount of sea water was introduced into reactor pressure vessels. Not only sodium chloride but also several minor elements contained in sea water, such as K, Ca, Mg, and S, possibly reacted with degraded fuel debris or molten corium. Considering possible chemical reactions, various concerns, such as volatilization of fission products, characterization of fuel debris, and formation of corrosive gases are pointed out. Thermodynamic evaluation can give useful information on the general tendency of these sea-water effects. The volatility of Cs, Sr, and Te is potentially increased owing to the change in stable chemical species. Corrosive gases, such as HCl and H2S, are possibly generated from sea water heated at high temperatures. These phenomena are predicted to be varied by changing the oxygen potential.
The feasibility of the Bunsen reaction using an ionic liquid (IL) containing iodide ions as the solvent was experimentally examined to improve the thermal efficiency of a thermochemical water-splitting iodine-sulfur (IS) process for hydrogen production using a high-temperature gas-cooled reactor (HTGR) by increasing the hydrogen iodide (HI) concentration in the Bunsen reaction. The solubility of the reactants of the Bunsen reaction, iodine (I2) and sulfur dioxide (SO2), in the IL was measured to confirm the feasibility of the reaction. 1-Butyl-3-methylimidazolium iodide ([bimi][I]) showed an I2 solubility of 4.78 mol/mol at room temperature, which was 2.47 times higher than that in hydriodic acid. [bimi][I] also showed a high SO2 solubility of 3.42 mol/mol, which was 125 times higher than that in water. The feasibility of the Bunsen reaction using the IL was confirmed in terms of the increases in I2 and SO2 concentrations in the Bunsen reaction. The HI concentration in the hydriodic acid in the Bunsen reaction using [bimi][I] was preliminary examined at room temperature, ambient pressure, and reactant composition of IL:I2:SO2:H2O=0.25-0.5:0.51-2.1:1.0:1.0 (molar ratio). The maximum HI concentration was 24.5 mol% (=69.8 wt%), which was higher than that obtained by the conventional Bunsen reaction.
A method was presented to estimate radionuclide concentration in plume using the pulse height distribution measured by a LaBr3 scintillation detector and its calculated response to radionuclides in plume with egs5. Radionuclide concentration was estimated from the ratio between the peak count rates corresponding to each radionuclide in the measured pulse height distribution on an expressway on March 15 and in the calculated one from each radionuclide in plume using the egs5 Monte Carlo code. The pulse height distribution reconstructed based on the estimated concentrations agrees well with the measured one at the time that the contribution from radionuclides deposited on a ground surface is negligible.