Dynamics of radiocaesium within forests in Fukushima; Results and analysis of a model inter-comparison

Hashimoto, Shoji*; Tanaka, Taku*; Komatsu, Masabumi*; Gonze, M.-A.*; Sakashita, Wataru*; Kurikami, Hiroshi; Nishina, Kazuya*; Ota, Masakazu; Ohashi, Shinta*; Calmon, P.*; et al.

Journal of Environmental Radioactivity, 238-239, p.106721_1 - 106721_10, 2021/11

https://doi.org/10.1016/j.jenvrad.2021.106721

This study was aimed at analysing performance of models for radiocesium migration mainly in evergreen coniferous forest in Fukushima, by inter-comparison between models of several research teams. The exercise included two scenarios of countermeasures against the contamination, namely removal of soil surface litter and forest renewal, and a specific konara oak forest scenario in addition to the evergreen forest scenario. All the models reproduced trend of time evolution of radiocesium inventories and concentrations in each of the components in forest such as leaf and organic soil layer. However, the variations between models enlarged in long-term predictions over 50 years after the fallout, meaning continuous field monitoring and model verification/validation is necessary.

Isotope shift and hyperfine structure measurements on triple resonance excitation to the autoionizing Rydberg state of atomic strontium

Iwata, Yoshihiro; Miyabe, Masabumi; Akaoka, Katsuaki; Wakaida, Ikuo

Journal of Quantitative Spectroscopy & Radiative Transfer, 275, p.107882_1 - 107882_9, 2021/11

https://doi.org/10.1016/j.jqsrt.2021.107882

Following the accident at TEPCO's Fukushima Daiichi Nuclear Power Station, an isotope-selective analysis method using laser resonance ionization has been developed for strontium-90. In this study, the isotope shifts and hyperfine structure constants of stable isotopes were measured for two schemes expected to have high isotopic selectivity, and the isotope shifts of strontium-90 were evaluated using the King plot analysis. The measured strontium-90 optical isotopic selectivities ranged from to , which are sufficient for analysis of real samples.

Impact of extreme typhoon events on the fluvial discharge of particulate radiocesium in Fukushima Prefecture

Nakanishi, Takahiro; Oyama, Takuya; Hagiwara, Hiroki; Sakuma, Kazuyuki

Journal of Coastal Research, 114(SI), p.310 - 314, 2021/10

https://doi.org/10.2112/JCR-SI114-063.1

The two huge typhoons in 2019, Hagibis and Bualoi, caused enormous flood damage to Fukushima. On the basis of field observations over 6 years in Ukedo River near the Fukushima Nuclear Power Plant, sediment and Cs discharges from the river catchment were quantitatively evaluated. Approximately 90% of annual sediment and Cs discharges in 2019 was occupied during the typhoons Hagibis and Bualoi events. This sediment discharge was almost twice than the discharge during the largest ever flood event since the Fukushima nuclear accident, caused by typhoon Etau in September 2015. However, Cs discharge during Hagibis and Bualoi events was two-thirds that of Etau event, because the particulate Cs concentration in river water decreased during the observation period. Moreover, Cs discharge during two typhoon events in 2019 accounted for only 0.1% of the catchment Cs deposition and the impact of radiocesium to the coastal area was extremely limited.

Validity of the source term for the Fukushima Dai-ichi Nuclear Power Station accident estimated using local-scale atmospheric dispersion simulations to reproduce the large-scale atmospheric dispersion of Cs

Kadowaki, Masanao; Furuno, Akiko; Nagai, Haruyasu; Kawamura, Hideyuki; Terada, Hiroaki; Tsuzuki, Katsunori; El-Asaad. H.

Journal of Environmental Radioactivity, 237, p.106704_1 - 106704_18, 2021/10

https://doi.org/10.1016/j.jenvrad.2021.106704

The source term of Cs for the Fukushima Daiichi Nuclear Power Station (FDNPS) accident was estimated from the results of local-scale atmospheric dispersion simulations and measurements. To confirm the source term's validity for reproducing the large-scale atmospheric dispersion of Cs, this study conducted hemispheric-scale atmospheric and oceanic dispersion simulations. In the dispersion simulations, the atmospheric-dispersion database system Worldwide version of System for Prediction of Environmental Emergency Dose Information (WSPEEDI)-DB and oceanic dispersion model SEA-GEARN-FDM were used. Compared with the air concentrations of Cs measured by the Comprehensive Nuclear-Test-Ban Treaty Organization, overall, the WSPEEDI-DB simulation reproduced the measurements with some overestimation. Furthermore, the deposition amounts of Cs was investigated using concentrations of Cs in seawater. The simulated seawater concentrations of Cs were underestimated regionally in the North Pacific. The overestimation and underestimation could be improved without contradiction between the air and seawater concentrations of Cs using more realistic precipitation in atmospheric dispersion simulations. This shows that the source term validated in this study could reproduce the spatiotemporal distribution of Cs because of the FDNPS accident in both local and large-scale atmospheric dispersion simulations.

Feasibility study of the one-dimensional radiation distribution sensing method using an optical fiber sensor based on wavelength spectrum unfolding

Terasaka, Yuta; Watanabe, Kenichi*; Uritani, Akira*; Yamazaki, Atsushi*; Sato, Yuki; Torii, Tatsuo; Wakaida, Ikuo

Journal of Nuclear Engineering and Radiation Science, 7(4), p.042002_1 - 042002_7, 2021/10

https://doi.org/10.1115/1.4048841

For the application in the measurement of the high dose rate hot spots inside the Fukushima Daiichi Nuclear Power Station (FDNPS) buildings, we propose a novel one-dimensional radiation distribution sensing method using an optical fiber sensor based on wavelength spectrum unfolding. The proposed method estimates the incident position of radiation to the fiber by the unfolding of the wavelength spectrum output from the fiber edge using the fact that the attenuation length of light along the fiber depends on the wavelength. Because this method measures the integrated light intensity, this method can avoid the problem of counting loss and signal pile-up, which occurs in the radiation detector with pulse counting mode under high dose rate field. Through basic experiments using the ultraviolet light source and Sr/Y radioactive point source, basic properties of source position detection were confirmed.

Radiocesium in Shiitake mushroom; Accumulation in living fruit bodies and leaching from dead fruit bodies

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

Chemosphere, 279, p.130511_1 - 130511_10, 2021/09

https://doi.org/10.1016/j.chemosphere.2021.130511

Cesium (Cs) accumulation by Shiitake was investigated to contribute to the elucidation of radiocesium-cycling mechanisms in forest environments. The results demonstrate that Shiitake non-specifically accumulates Cs while accumulating the essential element K and provide evidence that no selective Cs accumulation (or binding) sites exist within the Shiitake fruit body. Furthermore, the present results show that most accumulated Cs quickly leaches out from the dead fruit body with exposure to water. The leached Cs was largely adsorbable on clay minerals, suggesting that the Shiitake fruit body likely contains Cs in the cation form.

A BWR control blade degradation observed in situ during a CLADS-MADE-02 test under Fukushima Dai-Ichi Unit 3 postulated conditions

Pshenichnikov, A.; Kurata, Masaki; Nagae, Yuji

Journal of Nuclear Science and Technology, 58(9), p.1025 - 1037, 2021/09

https://doi.org/10.1080/00223131.2021.1906777

Development of the multi-cubic -ray spectrometer and its performance under intense Cs and Co radiation fields

Kaburagi, Masaaki; Shimazoe, Kenji*; Kato, Masahiro*; Kurosawa, Tadahiro*; Kamada, Kei*; Kim, K. J.*; Yoshino, Masao*; Shoji, Yasuhiro*; Yoshikawa, Akira*; Takahashi, Hiroyuki*

Nuclear Instruments and Methods in Physics Research A, 1010, p.165544_1 - 165544_9, 2021/09

https://doi.org/10.1016/j.nima.2021.165544

The number of nuclear facilities being decommissioned has been increasing worldwide, in particular following the accident of the Tokyo Electric Power Company Holdings' Fukushima Daiichi Nuclear Power Station in 2011. In these nuclear facilities, proper management of radioactive materials is required. Then, A -ray spectrometer with four segmentations using small volume CeBr scintillators with a dimension of was developed. The four scintillators were coupled to a multi-anode photomultiplier tube specific to intense radiation fields. We performed the -ray exposure study under Cs and Co radiation fields. Under the Cs radiation field, the relative energy resolution at 1375 mSv/h was the relative energy resolution at 1375 mSv/h was 9.20.05%, 8.00.08%, 8.00.03%, and 9.00.04% for the four channels, respectively.

Steam oxidation of silicon carbide at high temperatures for the application as accident tolerant fuel cladding, an overview

Pham, V. H.; Kurata, Masaki; Steinbrueck, M.*

Thermo (Internet), 1(2), p.151 - 167, 2021/09

https://doi.org/10.3390/thermo1020011

Rapid analysis of Sr in cattle bone and tooth samples by inductively coupled plasma mass spectrometry

Koarai, Kazuma; Matsueda, Makoto; Aoki, Jo; Yanagisawa, Kayo*; Terashima, Motoki; Fujiwara, Kenso; Kino, Yasushi*; Oka, Toshitaka; Takahashi, Atsushi*; Suzuki, Toshihiko*; et al.

Journal of Analytical Atomic Spectrometry, 36(8), p.1678 - 1682, 2021/08

https://doi.org/10.1039/D1JA00086A

Rapid analysis of Sr in bone and tooth samples of cattle were achieved by an inductively coupled plasma mass spectrometry (ICP-MS) coupled with mass shift and solid phase extraction techniques. Limit of detection (LOD) in the ICP-MS measurement of 0.1 g samples was lower than that of the radioactivity measurement. Analytical time of the ICP-MS method was reduced from 20 days to 11 hours, compared with the radiometric method. Therefore, the ICP-MS method can be rapid and useful procedure of Sr in small bone and tooth samples derived from terrestrial animals.