Progress of evaluation of beam coupling impedance reduction for the Eddy-current type septum magnet in J-PARC MR

Kobayashi, Aine*; Toyama, Takeshi*; Nakamura, Takeshi*; Shobuda, Yoshihiro; Ishii, Koji*; Tomizawa, Masahito*; Takeuchi, Yasunao*; Sato, Yoichi*

Proceedings of 19th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.19 - 23, 2023/01

https://www.pasj.jp/web_publish/pasj2022/proceedings/PDF/TUOB/TUOB01.pdf

In the J-PARC main ring, density modulation due to longitudinal beam instability occurs during the debunching process of coasting beams. This leads to the generation of an electron cloud, which in turn causes transverse beam instabilities. The transverse beam instability causes beam loss and the electron cloud is assumed to cause vacuum degradation, both of which hinder the beam intensity enhancement, so it is essential to clarify the causes and countermeasures. In particular, the longitudinal impedance of several hundred MHz has been investigated as relevant, and measures to reduce the impedance of individual devices are underway. The Eddy-current type septum magnet, newly installed this year, was found to have a large impedance by simulation. Therefore, we are investigating a method to reduce the impedance by a flange loaded with SiC radio wave absorber, which can be applied to locations where there is no spatial margin to install a taper. In this report, we will discuss the characterization of SiC to be used in actual devices, impedance simulation reflecting the results of SiC evaluation, and evaluation of the effect of impedance countermeasures by impedance measurement using the wire method, and progress in evaluating the effect on the beam by beam simulation and beam study.

Enhancement of element production by incomplete fusion reaction with weakly bound deuteron

Wang, H.*; Otsu, Hideaki*; Chiga, Nobuyuki*; Kawase, Shoichiro*; Takeuchi, Satoshi*; Sumikama, Toshiyuki*; Koyama, Shumpei*; Sakurai, Hiroyoshi*; Watanabe, Yukinobu*; Nakayama, Shinsuke; et al.

Communications Physics (Internet), 2(1), p.78_1 - 78_6, 2019/07

https://doi.org/10.1038/s42005-019-0165-1

Searching for effective pathways for the production of proton- and neutron-rich isotopes through an optimal combination of reaction mechanism and energy is one of the main driving forces behind experimental and theoretical nuclear reaction studies as well as for practical applications in nuclear transmutation of radioactive waste. We report on a study on incomplete fusion induced by deuteron, which contains one proton and one neutron with a weak binding energy and is easily broken up. This reaction study was achieved by measuring directly the cross sections for both proton and deuteron for Pd at 50 MeV/u via inverse kinematics technique. The results provide direct experimental evidence for the onset of a cross-section enhancement at high energy, indicating the potential of incomplete fusion induced by loosely-bound nuclei for creating proton-rich isotopes and nuclear transmutation of radioactive waste.

Year-round variations in the fluvial transport load of particulate Cs in a forested catchment affected by the Fukushima Daiichi Nuclear Power Plant accident

Matsunaga, Takeshi; Nakanishi, Takahiro; Atarashi-Andoh, Mariko; Takeuchi, Erina; Muto, Kotomi; Tsuzuki, Katsunori; Nishimura, Shusaku; Koarashi, Jun; Otosaka, Shigeyoshi; Sato, Tsutomu*; et al.

Journal of Radioanalytical and Nuclear Chemistry, 310(2), p.679 - 693, 2016/11

AA2015-0821.pdf:3.78MB

https://doi.org/10.1007/s10967-016-4840-3

Particulate Cs in stream water was collected continuously for two years in order to assess the long-term trend of the Cs discharge from the forest environment. Sampling was conducted from December 2011 to December 2013 in a mountainous stream, which received the Cs from the Fukushima Daiichi Nuclear Power Plant accident. A seasonal increase in fluvial transport load of particulate Cs associated with suspended solids (SS) was observed in August and September when rainfall was abundant. The particulate Cs concentration decreased at a faster rate than the rate due to radioactive decay. This decrease might be resulted from redistribution of the easily eroded and polluted soil surface due to heavy rain events such as typhoons. These findings indicate that the particulate Cs load was subject to the inter-annual variations in rainfalls, and decreased gradually over a long period of time due to a decrease in Cs concentration in SS.

Fluvial discharges of particulate and dissolved radiocesium from a forest and its monthly trend

Muto, Kotomi; Atarashi-Andoh, Mariko; Takeuchi, Erina; Nishimura, Shusaku; Koarashi, Jun; Tsuzuki, Katsunori; Nakanishi, Takahiro; Matsunaga, Takeshi

KEK Proceedings 2015-4, p.252 - 257, 2015/11

http://ccdb5fs.kek.jp/tiff/2015/1525/1525004.pdf#page=260

As a result of the Fukushima Daiichi Nuclear Power Plant accident, a large amount of radiocesium released into the atmosphere was deposited in forests. This study estimated the monthly trend in the fluvial discharges of radiocesium from a forest. The study site was a forested catchment in Kitaibaraki City. Radiocesium in river water was collected with a filtration system as both particulate and dissolved components. Filters and columns including dissolved Cs absorbent were replaced every month. The collected suspended solids were sieved into 2000-3000 m, 500-2000 m, 75-500 m, and 75 m fractions. The Cs concentrations in the samples were measured using -ray spectrometry with Ge semiconductor detectors. The Cs discharge increased with the river water discharge. The particulate Cs discharge was dominant in both 2013 and 2014. The Cs discharge rate of the dissolved component increased in winter, when the river water discharge decreased.

A Passive collection system for whole size fractions in river suspended solids

Matsunaga, Takeshi; Nakanishi, Takahiro; Atarashi-Andoh, Mariko; Takeuchi, Erina; Tsuzuki, Katsunori; Nishimura, Shusaku; Koarashi, Jun; Otosaka, Shigeyoshi; Sato, Tsutomu*; Nagao, Seiya*

Journal of Radioanalytical and Nuclear Chemistry, 303(2), p.1291 - 1295, 2015/02

https://doi.org/10.1007/s10967-014-3491-5

An innovative, yet simple method for the passive collection of radioactive materials in river water has been developed and validated. The method employes large filter vessels, containing multiple cartridge filters. River water is led to the system naturally using a drop of the riverbed by hose from upstream. This method makes long-term, unmanned monitoring possible. In addition to regular radioactivity analyses, this method provides an opportunity for the characterization of suspended materials based on its ample collection quantities (more than several tens of grams). This method may also be applicable to sediment-bound chemicals.

Effects of neutron irradiation on microstructures and hardness of stainless steel weld-overlay cladding of nuclear reactor pressure vessels

Takeuchi, Tomoaki; Kakubo, Yuta*; Matsukawa, Yoshitaka*; Nozawa, Yasuko*; Toyama, Takeshi*; Nagai, Yasuyoshi*; Nishiyama, Yutaka; Katsuyama, Jinya; Yamaguchi, Yoshihito; Onizawa, Kunio

Journal of Nuclear Materials, 449(1-3), p.273 - 276, 2014/06

https://doi.org/10.1016/j.jnucmat.2014.01.004

Microstructural changes and hardness of stainless steel weld overlay cladding of reactor pressure vessels subjected to the neutron irradiation with a dose of 7.2 10n cm (E 1 MeV) and a flux of 1.1 10n cm s at 290C were investigated by atom probe tomography and with nanoindentation technique. In order to isolate the effect of the irradiation, we compared the results of the measurements of the irradiated sample with that of the aged one at 300C for the time equivalent to the irradiation. The Cr concentration fluctuation was enhanced in the -ferrite phase of the irradiated sample. In addition, the enhancement of the concentration fluctuation of Si, which was not observed in the aged sample, was observed. The hardening at the -ferrite phase was occurred by both the irradiation and the aging. However, the former was more than that expected from the Cr concentration fluctuation, which suggested that the Si concentration fluctuation and irradiation-induced defects were possible origins of the additional hardening.

Development of Self Powered Gamma Detector (SPGD) with lead emitter

Shibata, Akira; Takeuchi, Tomoaki; Otsuka, Noriaki; Saito, Takashi; Onoda, Shinobu; Oshima, Takeshi; Tsuchiya, Kunihiko

JAEA-Technology 2013-043, 24 Pages, 2014/01

JAEA-Technology-2013-043.pdf:2.76MB

The big tsunami wave caused by the Great East Japan Earthquake triggered station black out of the Fukushima Daiichi Nuclear Power Plant. The schedule until ending of the decommission is shown in the guidance from Japanese government. But the dose rate in the reactor vessel is quite high and it is not possible to specify the position of melted fuel debris by visual inspection. That is one of the most important issues in this process. This report describes the development of Self Powered Gamma Detector (SPGD) for the purpose to specify the position of melted fuel debris and situation in the reactor by measuring rate in the reactor of the Fukushima Daiichi Nuclear Power Plant. The irradiation examinations by changing the parameter of emitters figure were performed and the dependency of SPGD output on emitter shape was summarized.

Study on cleaing solvents using activated alumina in PUREX process

Arai, Yoichi; Ogino, Hideki; Takeuchi, Masayuki; Kase, Takeshi; Nakajima, Yasuo

Proceedings in Radiochemistry, 1(1), p.71 - 74, 2011/09

http://www.oldenbourg-link.com/doi/abs/10.1524/rcpr.2011.0028

Solvent cleanup method using activated alumina was discussed in this study. This method was one of candidate to remove TBP/-dodecane degradation products. The degradation sample of 30% TBP/-dodecane was prepared by irradiation (1.6 MGy) using Co -source. The absorbed dose for sample was almost 1.6 MGy. The degradation products were qualitatively analyzed by gas chromatography-mass spectrometer (GC-MS). After the irradiation, solvent cleanup was performed by activated alumina and the cleanup using alumina was examined by phase separation test with 3M HNO. As the result, it was found that hexane and long-chain alcohols were mainly generated as the n-dodecane degradation products by irradiation, and almost 70% of the TBP/-dodecane degradation products were removed and the phase separation performance were improved by the cleanup using activated alumina.

Technical know-how for modeling of geological environment, 1; Overview and groundwater flow modeling

Saegusa, Hiromitsu; Takeuchi, Shinji; Maekawa, Keisuke; Osawa, Hideaki; Semba, Takeshi

Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.133 - 140, 2010/10

https://doi.org/10.1115/ICEM2010-40062

Studies on grouting performance in Mizunami Underground Research Laboratory (Contract research)

Kawamura, Hideki*; Ando, Kenichi*; Noda, Masaru*; Tanaka, Tatsuya*; Matsuda, Takeshi*; Fujii, Haruhiko*; Hashimoto, Shuji*; Ueda, Tadashi*; Matsui, Hiroya; Takeuchi, Shinji; et al.

JAEA-Technology 2009-081, 182 Pages, 2010/03

JAEA-Technology-2009-081.pdf:28.89MB

Grouting has practical importance for the reduction of groundwater inflow into excavations during construction of underground facilities. Considering the performance assessment of a radioactive waste repository, the performance of the engineered barrier system could be adversely affected by a high pH plume generated from grout. Therefore, a quantitative estimation of the effectiveness of grouting and grout material is essential. This study has been performed in the Mizunami URL being excavated in crystalline rock as a part of the Project for Grouting Technology Development for the Radioactive Waste Repository funded by METI, Japan. The aims were to evaluate the applicability of existing grouting technology and to develop methodology to determine the distribution of grout and change in hydraulic properties of the grouted rock volume. The target rock is the volume of rock around a planned refuge niche where the pre-excavation grouting was performed at 200-m depth from ground surface. After excavation of the refuge niche, ten boreholes were drilled and different kinds of investigations were carried out during and after drilling. The results were integrated and groundwater flow analysis of pre and post excavation grouting conditions were carried out to estimate quantitatively the effect of pre-excavation grouting. The results suggest that current pre-excavation grouting technology is effective for reduction of groundwater inflow into excavations and that hydraulic conductivity of the surrounding rock can be reduced by more than one order of magnitude.