Ten years after the NPP accident at Fukushima; Review on fuel debris behavior in contact with water

Grambow, B.; Nitta, Ayako; Shibata, Atsuhiro; Koma, Yoshikazu; Utsunomiya, Satoshi*; Takami, Ryu*; Fueda, Kazuki*; Onuki, Toshihiko*; Jegou, C.*; Laffolley, H.*; et al.

Journal of Nuclear Science and Technology, 59(1), p.1 - 24, 2022/01

https://doi.org/10.1080/00223131.2021.1966347

Effect of bacterial siderophore on cesium dissolution from biotite

Kimura, Tatsuki*; Fukutani, Satoshi*; Ikegami, Maiko*; Sakamoto, Fuminori; Kozai, Naofumi; Grambow, B.*; Yoneda, Minoru*

Chemosphere, 276, p.130121_1 - 130121_7, 2021/08

https://doi.org/10.1016/j.chemosphere.2021.130121

The adsorption of cesium (Cs) on biotite and dissolution of Cs from Cs-bearing biotite using a siderophore were investigated aiming to contribute to the elucidation of radiocesium migration mechanisms in the soil environment. Cs was adsorbed on a hardly weathered biotite powder sample. A siderophore was extracted and purified from the bacterial culture medium, and the purified siderophore was used in five consecutive dissolution experiments of the biotite samples. The major components of the biotite (Al, Fe, and Mg) were dissolved almost stoichiometrically, strongly suggesting that the siderophore selectively dissolves the broken edges of the biotite. The Cs adsorbed on the broken edges was dissolved rapidly as the siderophore dissolved the broken edges, and then, the Cs adsorbed on the outer planar surface of the biotite particles was slowly dissolved.

Study on coordination structure of Re adsorbed on Mg-Al layered double hydroxide using X-ray absorption fine structure

Tanaka, Kazuya; Kozai, Naofumi; Onuki, Toshihiko; Grambow, B.

Journal of Porous Materials, 26(2), p.505 - 511, 2019/04

https://doi.org/10.1007/s10934-018-0634-z

In this study, we utilized X-ray absorption fine structure spectroscopy to clarify the coordination structure of Re in Mg-Al LDH as a surrogate of Tc. Adsorption experiments of ReO on calcined and uncalcined Mg-Al LDHs were conducted in aqueous solutions with different concentrations of NaCl, NaNO, and NaSO. Calcined Mg-Al LDH showed much higher adsorption than uncalcined one. The adsorption of ReO was reversible, and decreased with increasing concentration of competing anions like Cl, NO, or SO. Analysis of Re L-edge extended X-ray absorption fine structure indicated that ReO was adsorbed as an outer-sphere complex on Mg-Al LDH. The observed Re adsorption-desorption behavior, which was sensitive to the presence of competing anions, was consistent with the formation of outer sphere-complex.

Complexation of Eu(III), Pb(II), and U(VI) with a glycoprotein; Microbial transformation of heavy elements in the aquatic environment

Kozai, Naofumi; Sakamoto, Fuminori; Tanaka, Kazuya; Onuki, Toshihiko; Sato, Takahiro*; Kamiya, Tomihiro*; Grambow, B.

Chemosphere, 196, p.135 - 144, 2018/04

https://doi.org/10.1016/j.chemosphere.2017.12.154

Transformation of heavy elements by microbes such as bacteria and fungi has been an intense research subject; however, little is known about that of protozoa. This study investigated interaction of a representative protozoa, , with heavy elements (Eu(III), Pb(II), U(VI)). Non-destructive elemental analysis by micro-PIXE hardly detected those elements on living cells after sorption experiments but clearly detected on the cells that were killed with a fixative beforehand. Chromatographic analysis of aquatic species of those heavy elements after the sorption experiments revealed a fraction of those elements bound to a glycoprotein dissolved from the cell surface of living cells to form soluble pseudocolloid. These findings suggest that complexation of heavy elements with the dissolved surface glycoprotein reduced the sorption of those heavy elements on living cells.

Accumulation of Cs by shiitake cultivated in mushroom bed

Guido-Garcia, F.; Kozai, Naofumi; Sakamoto, Fuminori; Grambow, B.

no journal, , 

We aimed to improve the understanding of the mechanisms by which mushrooms can accumulate radiocesium within the fruit body.Cesium-137 is one of the most common fission products of uranium in nuclear reactors and was widely spread during the Fukushima incident in 2011. Nowadays, Cs is one of the main concerns in terms of contamination due to its half-life (30.1 y) and prevalence in forests. Here, cesium is accumulated by different organisms such as animals, plants and fungi. Specifically for fungi, some species have been identified that can accumulate Cs efficiently. Mushrooms are of special interest because the ingestion of contaminated species can lead to internal exposure of radioactivity. In this context, understanding the mechanisms by which cesium is accumulated by mushrooms is of particular interest and not yet fully understood. Moreover, the mechanisms by which Cs is released back into soil after mushrooms die has not been fully investigated either. In this research, we aim to improve the understanding of Cs uptake by comparing its behavior to another cation (K). For this, shiitake mushrooms were used as a model organism and exposed to Cs and K under laboratory conditions. Samples of fruit body were taken at different time points and their radioactivity analyzed by Ge detector to evaluate the uptake at different maturity stages. The results of these experiments will be shown and discussed.

Organic acids production as a possible mechanism of uptake of Cs by mushrooms

Guido-Garcia, F.; Sakamoto, Fuminori; Kozai, Naofumi; Grambow, B.

no journal, , 

Cs was released from FNPP in 2011 and is one of the main concerns due to its half-life and prevalence in forests. Here, Cs can be taken and accumulated by different organisms, e.g. mushrooms. This can result in mobilization through the environment. Elucidating the mechanisms by which cesium is taken from soil by mushrooms is key to understand its environmental behavior. In soil, Cs can be tightly fixed to clay minerals thus its bioavailability is poor. Organic acids and siderophores produced by mushrooms may remove Cs from mineral surfaces making it bioavailable. To assess this, different strains of fungi were chosen from a ~1000 collection that has been previously tested for Cs accumulation capacity. Organic acids were analyzed by GC-MS and HPLC-ICP-MS from different strains with different accumulating capacities. These were then tested in cesium desorption experiments using key minerals, and compared to a commercial siderophore.

Upward migration of radiocesium in soil via abiotic process

Sakamoto, Fuminori; Kozai, Naofumi; Guido-Garcia, F.; Kimura, Tatsuki; Grambow, B.

no journal, , 

Soil microorganisms are known to remove a fraction of tightly fixed radiocesium and make it bioavailable. In this study, we attempted to nondestructively recover available radiocesium from soil using microorganisms instead of plants. Microbial activity was tested to form bioavailable radiocesium by the comparing the addition of nutrients and microbicide. Powdered minerals, a water absorbent material, and paper towels were packed in a fine mesh cloth bag (mineral bag) with a size of 50 cm 50 cm. The radiocesium concentration analysis revealed that the surface soil contained approximately 0.3-1.2 Bq/g. The mineral mat was replaced with a new one every two weeks. Two control experiments were established: one with 1 L of nutrient solution to activate microorganisms, and another with sodium hypochlorite aqueous solution to suppress microbial activity. These solutions were added every week. After eight weeks, radiocesium concentrations of the top soil and in the soil core were measured. The accumulative radiocesium concentration in the four mats after eight weeks was within 4.210 and 9.010 Bq, indicating that the mats indeed absorbed radiocesium from soil. The driving force of upward migration of radiocesium is thought to be soil water flow due to continuous water absorption from soil by the mat and evaporation from itself. These results suggest that cesium upward migration flow along with water is a behavior expected to happen in the environment.

Cs uptake by lentinula edodes (shiitake) mushrooms

Guido-Garcia, F.; Sakamoto, Fuminori; Kozai, Naofumi; Grambow, B.; Devid, K.*

no journal, , 

The uptake of Cs by fungi has been thought to be similar to the uptake of K due to their chemical similarities. In this research we aimed to evaluate the impact of different concentrations of K in Cs uptake during mushrooms growth, as well as determine the spatial distribution of both within fruit bodies. Lentinula edodes (shiitake) was used as a model organism due to their capacity to produce fruit body. Preliminary results have shown that the concentrations of Cs in the obtained mushroom samples from mushroom bed did not show any clear relationship to the different concentrations of added K. Higher concentrations of Cs were observed in pileus than in stem, consistently. The results of Cs and K mapping did not show a significant spatial variation. This result suggest that Cs and K are distributed evenly, and that there is no specific or selective binding site for cesium.

Adsorption of Ba and Sr on Mn oxide produced by Coprinopsis urticicola strain Mn-2

Tanaka, Kazuya; Kozai, Naofumi; Yamaji, Keiko*; Masuya, Hayato*; Grambow, B.

no journal, , 

Radium-226 is of serious concern in Ningyo-toge Environmental Engineering Center because its radioactive concentration in mining wastewater exceeds the effluent standard. In this study, we examined Ba and Sr adsorption on biogenic Mn oxide as a preliminary surrogate for Ra adsorption. Both Ba and Sr show the dependence of adsorption on NaCl concentration. Overall, Ba gave an order of magnitude higher Kd values than Sr. Adsorption behavior of Ra would be similar to that of Ba in terms of ionic radius. Barium showed Kd value greater than 10 mL/g in 10 mM NaCl solution, similar to the ionic strength of the fresh water system in the Ningyo-toge center. Therefore, it is expected that the biogenic Mn can work effectively for removal of Ra from mining wastewater.