Positron annihilation lifetime spectroscopy investigation of thermal aging effect for the mechanical properties of hydrogen-absorbed tantalum

Ishijima, Yasuhiro; Yokoyama, Kenichi*; Ueno, Fumiyoshi; Abe, Hitoshi

Materials Transactions, 63(4), p.592 - 599, 2022/04

https://doi.org/10.2320/matertrans.MT-M2021244

The effect of thermal aging on the behavior of vacancy-hydrogen (H) cluster generation and the mechanical properties of tantalum (Ta) were investigated by positron annihilation lifetime spectroscopy (PALS) and tensile tests. Based on the PALS results, vacancy clusters that included 8-15 vacancies were generated after aging at and above 200C, and vacancy-H clusters were generated in 3 and 6 h-charged specimens after aging at 300C. The loss of ductility in Ta and crack generation were observed by conducting tensile tests in 6 h H-charged specimens after aging at 200C for 2000 h and in 3 and 6 h H-charged specimens aged at 300C for 2000 h. The reduction of ductility due to thermal aging of Ta was also observed under these thermal aging conditions. These results suggested that vacancy-H cluster generated by dissolved H during thermal aging induced the ductility loss by reducing the dislocation migration during deformation.

Dynamical response of transition-edge sensor microcalorimeters to a pulsed charged-particle beam

Okumura, Takuma*; Azuma, Toshiyuki*; Bennet, D. A.*; Caradonna, P.*; Chiu, I.-H.*; Doriese, W. B.*; Durkin, M. S.*; Fowler, J. W.*; Gard, J. D.*; Hashimoto, Tadashi; et al.

IEEE Transactions on Applied Superconductivity, 31(5), p.2101704_1 - 2101704_4, 2021/08

https://doi.org/10.1109/TASC.2021.3067793

A superconducting transition-edge sensor (TES) microcalorimeter is an ideal X-ray detector for experiments at accelerator facilities because of good energy resolution and high efficiency. To study the performance of the TES detector with a high-intensity pulsed charged-particle beam, we measured X-ray spectra with a pulsed muon beam at the Japan Proton Accelerator Research Complex (J-PARC) in Japan. We found substantial temporal shifts of the X-ray energy correlated with the arrival time of the pulsed muon beam, which was reasonably explained by pulse pileup due to the incidence of energetic particles from the initial pulsed beam.

Deexcitation dynamics of muonic atoms revealed by high-precision spectroscopy of electronic X rays

Okumura, Takuma*; Azuma, Toshiyuki*; Bennet, D. A.*; Caradonna, P.*; Chiu, I. H.*; Doriese, W. B.*; Durkin, M. S.*; Fowler, J. W.*; Gard, J. D.*; Hashimoto, Tadashi; et al.

Physical Review Letters, 127(5), p.053001_1 - 053001_7, 2021/07

https://doi.org/10.1103/PhysRevLett.127.053001

We observed electronic X rays emitted from muonic iron atoms using a superconducting transition-edge-type sensor microcalorimeter. The energy resolution of 5.2 eV in FWHM allowed us to observe the asymmetric broad profile of the electronic characteristic and X rays together with the hypersatellite X rays around 6 keV. This signature reflects the time-dependent screening of the nuclear charge by the negative muon and the -shell electrons, accompanied by electron side-feeding. Assisted by a simulation, this data clearly reveals the electronic - and -shell hole production and their temporal evolution during the muon cascade process.

A Failure investigation of the beam collimator system in the J-PARC 3 GeV rapid cycling synchrotron

Okabe, Kota; Yamamoto, Kazami; Kamiya, Junichiro; Takayanagi, Tomohiro; Yamamoto, Masanobu; Yoshimoto, Masahiro; Takeda, Osamu*; Horino, Koki*; Ueno, Tomoaki*; Yanagibashi, Toru*; et al.

Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.853 - 857, 2017/12

http://www.pasj.jp/web_publish/pasj2017/proceedings/PDF/WEP0/WEP021.pdf

The most important issue is to reduce the uncontrolled beam loss in the high intensity hadron accelerator such as J-PARC proton accelerators. The J-PARC 3 GeV Synchrotron (RCS) has a collimator system which narrows a high intensity beam in the RCS. After startup of RCS in 2007, the collimator system of the RCS worked well. However, in April 2016, vacuum leakage at the collimator system occurred during the maintenance operation. To investigate a cause of the failure, we took apart iron shields of the collimator reducing exposed dose of operators. As a result of inspection, we succeeded to identify the cause of the vacuum leakage failure. In this presentation, we report the failure investigation of the beam collimator system in the RCS.

New precise measurement of muonium hyperfine structure interval at J-PARC

Ueno, Yasuhiro*; Aoki, Masaharu*; Fukao, Yoshinori*; Higashi, Yoshitaka*; Higuchi, Takashi*; Iinuma, Hiromi*; Ikedo, Yutaka*; Ishida, Katsuhiko*; Ito, Takashi; Iwasaki, Masahiko*; et al.

Hyperfine Interactions, 238(1), p.14_1 - 14_6, 2017/11

https://doi.org/10.1007/s10751-016-1381-7

Radiochemical analysis of rubble collected from Fukushima Daiichi Nuclear Power Station

Sato, Yoshiyuki; Tanaka, Kiwamu; Ueno, Takashi; Ishimori, Kenichiro; Kameo, Yutaka

Hoken Butsuri, 51(4), p.209 - 217, 2016/12

https://doi.org/10.5453/jhps.51.209

A large amount of contaminated rubbles were generated by the accident at the Fukushima Daiichi Nuclear Power Station (F1NPS). For safe decommissioning of F1NPS, it is important to evaluate the composition and concentration of radionuclides in the rubbles. In this paper, to characterize the rubbles collected at F1NPS in Unit-1, Unit-2 and Unit-3, radiochemical analysis was operated. As a result of radiochemical analysis, -ray-emitting nuclides Co, Cs and Eu, -ray-emitting nuclides H, C, Sr and Tc, and -particle-emitting nuclides Pu, Am and Cm were detected. In contrast, Nb and Eu concentrations were below the detection limit. Measured radioactive concentrations implied that H, C, Co and Sr concentrations depended on Cs concentration respectively. This analysis was characterized the radioactivity concentrations of the rubbles.

Impact hammer test of ITER blanket remote handling system

Noguchi, Yuto; Maruyama, Takahito; Ueno, Kenichi; Komai, Masafumi; Takeda, Nobukazu; Kakudate, Satoshi

Fusion Engineering and Design, 109-111(Part B), p.1291 - 1295, 2016/11

https://doi.org/10.1016/j.fusengdes.2015.12.040

This paper reports the impact hammer test of the full-scale mock-up of ITER Blanket Remote Handling system (BRHS). Since the BRHS, which is composed of the articulated rail and the vehicle manipulator which travels on the rail deployed in the vacuum vessel, is subjected to the floor response spectrum with 14 G peak at 8 Hz, evaluation of dynamic response of the system is of essential importance. Recently impact hammer testing on the full-scale mock-up of the BRHS was carried out to verify the finite element method seismic analysis and to experimentally obtain the damping ratio of the system. The results showed that the mock-up has a vertical major natural mode with a natural frequency of 7.5 Hz and a damping ratio of 0.5%. While higher structural damping ratios is predicted in a high amplitude excitation such as major earthquake, it was confirmed that the experimental natural major frequencies are in agreement with the major frequencies obtained by elastic dynamic analysis.

Information on ITER project, 49

Moriyama, Setsuko; Ueno, Kenichi

Purazuma, Kaku Yugo Gakkai-Shi, 91(1), p.74 - 75, 2015/01

http://www.jspf.or.jp/Journal/PDF_JSPF/jspf2015_01/jspf2015_01-74.pdf

no abstracts in English

Preliminary assessment for dust contamination of ITER in-vessel transporter

Saito, Makiko; Ueno, Kenichi; Maruyama, Takahito; Murakami, Shin; Takeda, Nobukazu; Kakudate, Satoshi; Nakahira, Masataka*; Tesini, A.*

Fusion Engineering and Design, 89(9-10), p.2352 - 2356, 2014/10

https://doi.org/10.1016/j.fusengdes.2014.02.023

After plasma operation of the ITER reactor, irradiated radioactive dust will accumulate in the vacuum vessel (VV). The In Vessel Transporter (IVT) will be installed in the VV and remove the blanket modules for maintenance. The IVT will be carried back to the Hot Cell Facilities (HCF) after exchanging the blanket, and the IVT itself also needs maintenance. It is considered that the maintenance workers will be exposed to the irradiated radioactive dust attached to the IVT surface. In this study, dust contamination of the IVT is evaluated to assess exposure during maintenance work in the HCF. The IVT contamination scenario is assumed in the ITER project. From plasma shut down until maintenance is performed on the IVT will take 345 days under the ITER project assumption. Under this scenario, the effective dose rate from irradiated radioactive dust was calculated as an infinite plate for each nuclide. As a result, W-181 and Ta-182 were the dominant nuclides for the effective dose rate. If all dust is W-181 or Ta-182, the effective dose rate is about 400 Sv/h and 100 Sv/h respectively. Nevertheless, using the dose limit determined by the ITER project and the estimated maximum maintenance time, the effective dose rate limit was calculated to be 4.18 Sv/h under these limited conditions. To satisfy the dose rate limit, decontamination processes were assumed and the dose rate after decontamination was evaluated.

Latest information on ITER Project, 46

Moriyama, Setsuko; Neyatani, Yuzuru; Ueno, Kenichi

Purazuma, Kaku Yugo Gakkai-Shi, 90(7), p.429 - 430, 2014/07

http://www.jspf.or.jp/Journal/PDF_JSPF/jspf2014_07/jspf2014_07-429.pdf

no abstracts in English