Speciation on the reaction of uranium and zirconium oxides treated under oxidizing and reducing atmospheres

Uehara, Akihiro*; Akiyama, Daisuke*; Ikeda, Atsushi; Numako, Chiya*; Terada, Yasuko*; Nitta, Kiyofumi*; Ina, Toshiaki*; Takeda-Homma, Shino*; Kirishima, Akira*; Sato, Nobuaki*

Journal of Nuclear Materials, 559, p.153422_1 - 153422_11, 2022/02

https://doi.org/10.1016/j.jnucmat.2021.153422

Penetration factor and indoor deposition rate of elementary and particulate iodine in a Japanese house for assessing the effectiveness of sheltering for radiation exposures

Hirouchi, Jun; Takahara, Shogo; Komagamine, Hiroshi*; Kato, Nobuyuki*; Matsui, Yasuto*; Yoneda, Minoru*

Journal of Radiological Protection, 41(3), p.S139 - S149, 2021/09

https://doi.org/10.1088/1361-6498/ac025b

Sheltering is one of the countermeasures for protection against radiation exposures in nuclear accidents. The effectiveness of sheltering is often expressed by the reduction factor, that is the ratio of the indoor to the outdoor cumulative radioactivity concentrations or doses. The indoor concentration is mainly controlled by the air exchange rate, penetration factor, and indoor deposition rate. The penetration factor and indoor deposition rate depend on the surface and opening materials. We investigated experimentally these parameters of I and particles. The experiment was performed in two apartment houses, three single-family houses, and chambers. The obtained penetration factor ranged 0.3 1 for particles of 0.3 1 m and 0.15 0.7 for I depending on the air exchange rate. The indoor deposition rate for a house room ranged 0.007 0.2 h for particles of 0.31 m and 0.21.5 h for I depending on floor materials.

Effect of grain boundary on the friction coefficient of pure Fe under the oil lubrication

Adachi, Nozomu*; Matsuo, Yasutaka*; Todaka, Yoshikazu*; Fujimoto, Mikiya*; Hino, Masahiro*; Mitsuhara, Masatoshi*; Oba, Yojiro; Shiihara, Yoshinori*; Umeno, Yoshitaka*; Nishida, Minoru*

Tribology International, 155, p.106781_1 - 106781_9, 2021/03

https://doi.org/10.1016/j.triboint.2020.106781

Rapid tritium analysis for marine products in the coastal area of Fukushima

Kuwata, Haruka*; Misono, Toshiharu; Fujiwara, Kenso; Takeishi, Minoru; Manabe, Sachi*; Kitamura, Akihiro

Radiation Environment and Medicine, 9(1), p.28 - 34, 2020/02

http://crss.hirosaki-u.ac.jp/rem_archive/radiation-environment-and-medicine-vol-9-no-1

The analysis of tritium in aquatic biota is one of the most important research areas in Fukushima. The conventional method for measuring the concentration of tritium consists of complicated pretreatment procedures and requires skillful techniques as well as a significant amount of time. Consequently, there are only a few reports on tritium monitoring data in marine products from the coast of Fukushima. In this study, we measured the Tissue Free Water Tritium (TFWT) and Organically Bound Tritium (OBT) in flounders collected from the coast of Fukushima to examine the impacts of the nuclear accident on aquatic biota. The study was done for a period of 4 years; from 2015 to 2018. The conventional method of analysis was firstly used, after which the method was modified by improving the freeze-drying and combustion water recovery processes. Results from both methods show that the most of the concentrations of the TFWT and OBT in the flounder were below the detection or quantitative limit. The effect of the nuclear accident on humans, through internal exposure, was also examined and found to be negligible. Although some uncertainties exist due to the short cut of the processes, the modified version could be considered an effective and practical approximate method.

Characterisation of colloidal silica for rock grouting under saline groundwater

Tsuji, Masakuni*; Okihara, Mitsunobu*; Nakashima, Hitoshi*; Saito, Akira*; Aoyagi, Kazuhei; Sato, Toshinori

Dai-47-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koenshu (Internet), p.266 - 271, 2020/01

As engineering technique for geological disposal, a lot of advancement development of the grout technology has been performed. But the design, construction method in consideration of the properties of matter acquisition and mechanism of the hardening that assumed a seawater condition bottom is non-establishment. As we carried out the knowledge under saline water, the basic properties acquisition, the penetration properties acquisition, a study revue based on such situation.

Characterisation of colloidal silica grout under saline groundwater; Penetration theory and injection tests in a fracture test system

Martikainen, J.*; Tsuji, Masakuni*; Schatz, T.*; Nakashima, Hitoshi*; Okihara, Mitsunobu*; Aoyagi, Kazuhei; Sato, Toshinori

Proceedings of the Nordic Grouting Symposium 2019 (Internet), 13 Pages, 2019/09

This paper shows a result of the part of the study on characterisation of penetration of the colloidal silica grout (CSG) under saline groundwater, aiming to understand the impact of salinity on grout penetration by verifying the improved penetration theory with laboratory tests. This theory was proposed to add a time factor to the existing penetration theory of Funehag, especially under the saline groundwater conditions. A series of grout injection tests by the fracture test system were performed. The CSG of one European and Japanese were injected in the system, filled with the five different groundwater simulants. All no-flow tests were successful, resulting in the formation of relatively homogeneous gelled zones. Based on the analysis of acquired , it was found that as an alternative method, designing a longer gel time by multiplying the inverse value of can be proposed to attain the required penetration. Although the results were fruitful, further investigation is necessary to develop this penetration theory.

Development of compact high field pulsed magnet system for new sample environment equipment at MLF in J-PARC

Watanabe, Masao; Nojiri, Hiroyuki*; Ito, Shinichi*; Kawamura, Seiko; Kihara, Takumi*; Masuda, Takatsugu*; Sahara, Takuro*; Soda, Minoru*; Takahashi, Ryuta

JPS Conference Proceedings (Internet), 25, p.011024_1 - 011024_5, 2019/03

https://doi.org/10.7566/JPSCP.25.011024

Recently, neutron scattering experiments have been rapidly progressed under high magnetic field. In the J-PARC, proto-type compact pulse magnet system with the power supply, the coil and the sample stick has been developed. Basic specifications of the power supply are as follows; maximum charged voltage with capacitor is 2 kV, maximum current is 8 kA, repetition rate is a pulse per several minutes and pulse duration is several msec. Maximum magnetic field in the coil is more than 30 Tesla. The sample stick is designed for Orange-Cryostat. In this presentation, We report the details of the pulsed magnet system and the performance of it on neutron scattering experiments at MLF beam line (HRC).

Estimation of radiocesium dietary intake from time series data of radiocesium concentrations in sewer sludge

Pratama, M. A.; Takahara, Shogo; Munakata, Masahiro; Yoneda, Minoru*

Environment International, 115, p.196 - 204, 2018/06

https://doi.org/10.1016/j.envint.2018.03.009

Latest rock grouting technologies under sea water in Nordic countries and Japan

Tsuji, Masakuni*; Okihara, Mitsunobu*; Nakashima, Hitoshi*; Sato, Toshinori; Aoyagi, Kazuhei

Proceedings of 6th East Asia Forum on Radwaste Management Conference (EAFORM 2017) (Internet), 6 Pages, 2017/12

Regarding the engineering technology, the rock grouting has been recently studied as one of the most important technologies. Although the cement grout has not been reported to be affected by the sea water, the latest grouting material called colloidal silica grout is known to be sensitive to the saline water. The mechanism of its affection by sea water is not clear and its grouting methodology in such condition is not yet established either. Therefore, we studied on the latest grouting technologies for geological disposal in Nordic countries and Japan by article survey and a grouting workshop. As a result, it was found that the approach for countermeasures in grouting under sea water is different between Japan, Sweden, and Finland, which are based respectively on the mixture, on the design method, and on the controlling method. It seems that the best solution against this problem is to establish a hybrid and optimal grouting methodology under sea water by combining each country's developed grouting technology in the near future for saline condition, which is respectively based on mixing, design, and controlling method.

Experimental observation of temperature and magnetic-field evolution of the 4 states in CeFe revealed by soft X-ray magnetic circular dichroism

Saito, Yuji; Yasui, Akira*; Fuchimoto, Hiroto*; Nakatani, Yasuhiro*; Fujiwara, Hidenori*; Imada, Shin*; Narumi, Yasuo*; Kindo, Koichi*; Takahashi, Minoru*; Ebihara, Takao*; et al.

Physical Review B, 96(3), p.035151_1 - 035151_5, 2017/07

AA2017-0611.pdf:0.36MB

https://doi.org/10.1103/PhysRevB.96.035151

We revisit the delocalized character of the 4 states of CeFe in the ferromagnetically ordered phase by X-ray magnetic circular dichroism (XMCD) in X-ray absorption spectroscopy (XAS) with improved data quality using single crystals. Surprisingly, the Ce XMCD spectral shape changes significantly as a function of temperature and applied magnetic field, with no concomitant changes in the spectral shape of the Ce XAS as well as the Fe XAS and XMCD. This unusual behavior is characterized by the states in a 4 configuration mixed into the ground state. Such extreme sensitivity of the Ce 4 states to the external perturbations can be related to the magnetic instability toward an antiferromagnetic phase in CeFe. Our experimental data presented here provide valuable insights into the underlying physics in strongly-hybridized ferromagnetic Ce compounds.