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Journal Articles

Identification and quantification of a $$^{60}$$Co radiation source under an intense $$^{137}$$Cs radiation field using an application-specific CeBr$$_3$$ spectrometer suited for use in intense radiation fields

Kaburagi, Masaaki; Shimazoe, Kenji*; Kato, Masahiro*; Kurosawa, Tadahiro*; Takahashi, Hiroyuki*

Journal of Nuclear Science and Technology, 10 Pages, 2022/02

 Times Cited Count:0 Percentile:0.02(Nuclear Science & Technology)

Journal Articles

Design and actual performance of J-PARC 3 GeV rapid cycling synchrotron for high-intensity operation

Yamamoto, Kazami; Kinsho, Michikazu; Hayashi, Naoki; Saha, P. K.; Tamura, Fumihiko; Yamamoto, Masanobu; Tani, Norio; Takayanagi, Tomohiro; Kamiya, Junichiro; Shobuda, Yoshihiro; et al.

Journal of Nuclear Science and Technology, 32 Pages, 2022/02

 Times Cited Count:0 Percentile:0.02(Nuclear Science & Technology)

In the Japan Proton Accelerator Research Complex, the purpose of the 3 GeV rapid cycling synchrotron (RCS) is to accelerate a 1 MW, high-intensity proton beam. To achieve beam operation at a repetition rate of 25 Hz at high intensities, the RCS was elaborately designed. After starting the RCS operation, we carefully verified the validity of its design and made certain improvements to establish a reliable operation at higher power as possible. Consequently, we demonstrated beam operation at a high power, namely, 1 MW. We then summarized the design, actual performance, and improvements of the RCS to achieve a 1 MW beam.

JAEA Reports

Study on the evaluation method to determine the radioactivity concentration in radioactive waste on Oarai Research and Development Institute (FY2020)

Asakura, Kazuki; Shimomura, Yusuke; Donomae, Yasushi; Abe, Kazuyuki; Kitamura, Ryoichi; Miyakoshi, Hiroyuki; Takamatsu, Misao; Sakamoto, Naoki; Isozaki, Ryosuke; Onishi, Takashi; et al.

JAEA-Review 2021-020, 42 Pages, 2021/10

JAEA-Review-2021-020.pdf:2.95MB

The disposal of radioactive waste from the research facility need to calculate from the radioactivity concentration that based on variously nuclear fuels and materials. In Japan Atomic Energy Agency Oarai Research and Development Institute, the study on considering disposal is being advanced among the facilities which generate radioactive waste as well as the facilities which process radioactive waste. This report summarizes a study result in FY2020 about the evaluation method to determine the radioactivity concentration in radioactive waste on Oarai Research and Development Institute.

Journal Articles

Development of the multi-cubic $$gamma$$-ray spectrometer and its performance under intense $$^{137}$$Cs and $$^{60}$$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

 Times Cited Count:0 Percentile:0.02(Instruments & Instrumentation)

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 $$gamma$$-ray spectrometer with four segmentations using small volume CeBr$$_{3}$$ scintillators with a dimension of $$5 times 5 times 5$$ $$rm{mm}^3$$ was developed. The four scintillators were coupled to a multi-anode photomultiplier tube specific to intense radiation fields. We performed the $$gamma$$-ray exposure study under $$^{137}$$Cs and $$^{60}$$Co radiation fields. Under the $$^{137}$$Cs radiation field, the relative energy resolution at 1375 mSv/h was the relative energy resolution at 1375 mSv/h was 9.2$$pm$$0.05%, 8.0$$pm$$0.08%, 8.0$$pm$$0.03%, and 9.0$$pm$$0.04% for the four channels, respectively.

Journal Articles

Gamma-ray spectroscopy with a CeBr$$_3$$ scintillator under intense $$gamma$$-ray fields for nuclear decommissioning

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

Nuclear Instruments and Methods in Physics Research A, 988, p.164900_1 - 164900_8, 2021/02

 Times Cited Count:3 Percentile:84.28(Instruments & Instrumentation)

An increasing number of nuclear facilities have been decommissioned worldwide following the 2011 accident of the TEPCO' Fukushima Daiichi Nuclear Power Station. During the decommissioning, radioactive materials have to be retrieved under proper management. In this study, a small cubic CeBr$$_3$$ spectrometer with dimensions of 5 mm $$times$$ 5 mm $$times$$ 5 mm was manufactured to perform $$gamma$$-ray spectroscopy under intense $$gamma$$-ray fields. Furthermore, thanks to a fast digital process unit and a customized photomultiplier, the device could perform $$gamma$$-ray spectroscopy at dose rates of over 1 Sv/h. The energy resolution (FWHM) at 662 keV ranged from 4.4% at 22 mSv/h to 5.2% at 1407 mSv/h for a $$^{137}$$Cs radiation field. Correspondingly, at 1333 keV, it ranged from 3.1% at 26 mSv/h to 4.2% at 2221 mSv/h for a $$^{60}$$Co radiation field, which suggested to realize $$gamma$$-ray assessment of $$^{134}$$Cs, $$^{137}$$Cs, $$^{60}$$Co, and $$^{154}$$Eu at dose rates of over 1 Sv/h.

Journal Articles

Safety enhancement approach against external hazard on JSFR reactor building

Yamamoto, Tomohiko; Kato, Atsushi; Chikazawa, Yoshitaka; Hara, Hiroyuki*

Nuclear Technology, 206(12), p.1875 - 1890, 2020/12

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

This paper gives a detailed evaluation of the countermeasures for the external hazards and severe accidents that could impact the 2010 JSFR design building by lessons learned from the Fukushima Daiichi Nuclear Power Plant (Fukushima I NPP) accident.

Journal Articles

Diffusion and sorption behavior of HTO, Cs, I and U in mortar

Akagi, Yosuke*; Kato, Hiroyasu*; Tachi, Yukio; Sakamoto, Hiroyuki*

Progress in Nuclear Science and Technology (Internet), 5, p.233 - 236, 2018/11

A large amount of radioactive contaminated concrete will be generated from the decommissioning in the Fukushima Dai-ichi Nuclear Power Plant (NPP). For developing the plans of decommissioning and waste management including decontamination and disposal, it is important to estimate radionuclides inventory and concentration distribution in the concrete materials. In this study, effective diffusivities (De) and distribution coefficients (Kd) of HTO, Cs, I and U in OPC mortar were measured by through-diffusion and batch sorption experiments. De values derived were in the sequence of HTO, I, Cs, U, implying that cation exclusion effects may be important mechanisms in OPC mortar. Kd values derived by batch tests were higher by more than one order of magnitude than the diffusion-derived Kd values, indicating that crushing of samples had a strong influence on sorption. Diffusion and sorption mechanisms in OPC mortar were evaluated to predict the penetration behavior of these radionuclides.

Journal Articles

New scintillation type beam loss monitor to detect spot area beam losses in the J-PARC RCS

Yoshimoto, Masahiro; Harada, Hiroyuki; Kato, Shinichi; Kinsho, Michikazu; Okabe, Kota

Proceedings of 6th International Beam Instrumentation Conference (IBIC 2017) (Internet), p.461 - 465, 2018/03

In the J-PARC RCS, a large fraction of our effort has been concentrated on reducing and managing beam losses to achieve 1MW high power proton beam operation. Standard beam loss monitor (BLM), which is installed outside of the magnet in every cell of beam optics and detect the beam loss at wide area in each cell, is insufficient to investigate finer beam loss mechanism in the ring. Thus we developed new scintillation type BLM to detect the beam loss at spot area on the vacuum chamber inside the magnet. The new BLM has separating structure a photomultiplier (PMT) from a plastic scintillator and connecting with optical fibres. Because small plastic scintillator is installed on the vacuum chamber directly, it has capability to have high sensitivity for localized spot area beam loss. On the other hand, the PMT can precisely be operated without being affected by magnetic field by keeping the PMT from the magnet. The new BLM leads the RCS to achieve the stable high power beam operation. In this presentation, we report the detail of the performance of the new BLM.

Journal Articles

Laser storage ring with high power for realization of laser stripping injection

Harada, Hiroyuki; Yamane, Isao*; Saha, P. K.; Suganuma, Kazuaki; Kinsho, Michikazu; Irie, Yoshiro*; Kato, Shinichi

Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.684 - 688, 2017/12

The high-intensity proton accelerator adopts a charge exchange injection scheme, which injects with exchanging from negative Hydrogen ion to proton by using carbon foil. This scheme can realize high intensity proton beam but the uncontrolled beam losses are caused by scattering between beams and the foil. Additionally, the collision may occur the foil beak. Therefore, a new injection scheme for higher intensity is needed as an alternative to the foil. In the J-PARC 3GeV RCS, we newly propose and develop a laser stripping injection scheme. However, it is necessary that laser power is two order higher than latest laser one. To realize this big issue, we develop the laser storage ring, which can provide laser pulse of high repetition rate by recycling one. In this presentation, we will introduce the laser stripping injection scheme and describe the concept of the laser storage ring with high repetition rate and report the current status.

Journal Articles

Recent progress of J-PARC RCS beam commissioning; Efforts for realizing a high-intensity low-emittance beam

Hotchi, Hideaki; Harada, Hiroyuki; Kato, Shinichi; Okabe, Kota; Saha, P. K.; Shobuda, Yoshihiro; Tamura, Fumihiko; Tani, Norio; Watanabe, Yasuhiro; Yoshimoto, Masahiro

Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.95 - 99, 2017/12

no abstracts in English

Journal Articles

Struggle to suppress radio-activation due to multi-turn charge exchange beam injection with stripper foil and its issues

Yoshimoto, Masahiro; Kato, Shinichi; Okabe, Kota; Harada, Hiroyuki; Kinsho, Michikazu

Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.877 - 881, 2017/12

It is key issue to reduce the level of the radio-activation of the devices in high power proton accelerator, to achieve MW class high power beam operation. The 3 GeV Rapid Cycling Synchrotron (RCS) of the Japan Proton Accelerator Research Complex (J-PARC) adopted a beam collimation system which aims to localize the beam loss at the collimators and to reduce the level of residual doses at the other devices. However, relatively high residual doses are detected in not only the beam collimator area but also a vicinity of the stripper foil. The results of previous work, measurements of the detailed residual dose distribution and simulations of the radio-activation by the PHITS, indicate that the high level residual dose around the stripper foil is caused by secondary particles due to nuclear reaction at the foil. In order to suppress the secondary particles from foil, we try hard to reduce the number of foil hitting particles during the beam injection period. As a result, the level of the radio-activation around the foil can be decreased. At the same time, new beam loss monitor to detect the secondary particles from the foil is developed. In this presentation, we report the secondary particles detections and estimations of number of the foil hitting particles. In addition, we discuss the reduction of the radio-activation.

Journal Articles

Status of proof-of-principle experiment for 400 MeV H$$^{-}$$ stripping to protons by using only lasers in the 3-GeV RCS of J-PARC

Saha, P. K.; Harada, Hiroyuki; Yamane, Isao*; Kinsho, Michikazu; Miura, Akihiko; Okabe, Kota; Liu, Y.*; Yoshimoto, Masahiro; Kato, Shinichi; Irie, Yoshiro*

Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.866 - 870, 2017/12

Journal Articles

Achievement of a low-loss 1-MW beam operation in the 3-GeV rapid cycling synchrotron of the Japan Proton Accelerator Research Complex

Hotchi, Hideaki; Harada, Hiroyuki; Hayashi, Naoki; Kato, Shinichi; Kinsho, Michikazu; Okabe, Kota; Saha, P. K.; Shobuda, Yoshihiro; Tamura, Fumihiko; Tani, Norio; et al.

Physical Review Accelerators and Beams (Internet), 20(6), p.060402_1 - 060402_25, 2017/06

 Times Cited Count:22 Percentile:89.6(Physics, Nuclear)

The 3-GeV rapid cycling synchrotron (RCS) of the Japan Proton Accelerator Research Complex (J-PARC) is the world's highest class of high-power pulsed proton driver, aiming for an output beam power of 1 MW. The most important issues in realizing such a high-power beam operation are to control and minimize beam loss for maintaining machine activations within permissible levels. In RCS, numerical simulation was successfully utilized along with experimental approaches to isolate the mechanism of beam loss and find its solution. By iteratively performing actual beam experiments and numerical simulations, and also by several hardware improvements, we have recently established a 1-MW beam operation with very low fractional beam loss of a couple of 10$$^{-3}$$. In this paper, our recent efforts toward realizing such a low-loss high-intensity beam acceleration are presented.

Journal Articles

Realizing a high-intensity low-emittance beam in the J-PARC 3-GeV RCS

Hotchi, Hideaki; Harada, Hiroyuki; Kato, Shinichi; Okabe, Kota; Saha, P. K.; Shobuda, Yoshihiro; Tamura, Fumihiko; Tani, Norio; Watanabe, Yasuhiro; Yoshimoto, Masahiro

Proceedings of 8th International Particle Accelerator Conference (IPAC '17) (Internet), p.2470 - 2473, 2017/06

For this past year, RCS beam tuning was focused on realizing a high-intensity low-emittance beam required from the downstream facility. The extraction beam emittance including its tail part was successfully decreased by optimizing transverse injection painting, and tune and chromaticity manipulations, where bipolar sextupole field patterns were newly introduced to simultaneously achieve emittance growth mitigation at the early stage of acceleration and beam instability suppression after the middle stage of acceleration. This paper presents the recent experimental results, together with detailed discussions for the emittance growth and its mitigation mechanisms.

Journal Articles

Development of a method of safety assessment for geological disposal considering long-term evolution of geological and topographical environment by uplift and erosion

Wakasugi, Keiichiro; Yamaguchi, Masaaki; Koo, Shigeru*; Nagao, Fumiya; Kato, Tomoko; Suzuki, Yuji*; Ebashi, Takeshi; Umeki, Hiroyuki*; Niibori, Yuichi*

Nihon Genshiryoku Gakkai Wabun Rombunshi, 16(1), p.15 - 33, 2017/03

This study provides a method of safety assessment for the geological disposal of HLW to evaluate the effects of uplift and erosion which are widespread phenomena identified on regional and global scales, and are more or less difficult to avoid in Japan. This method enables to deal with different uplift rate and erosion rate, and to evaluate repository depth, the time required for a repository to reach the weathered zone and surface of the ground, and the number of waste packages eroded as a function of time by using a landform evolution model. Based on trial analysis, the result shows that the maximum dose in the Base Case (uplift rate: 0.3 mm/y) is less than the targeted criterion suggested by the international organization even if the repository reaches the ground surface. Furthermore, the diversifying effect on timing the waste packages to reach to weathered zone due to heterogeneity on altitude of bottom of weathered zone reduces one order magnitude of result of the existed dose assessment. The new method is applicable to evaluate safety of geological disposal based on realistic phenomena of uplift and erosion and to quantify a safety margin and robustness of the disposal system.

Journal Articles

Field test around Fukushima Daiichi Nuclear Power Plant site using improved Ce:Gd$$_{3}$$(Al,Ga)$$_{5}$$O$$_{12}$$ scintillator Compton camera mounted on an unmanned helicopter

Shikaze, Yoshiaki; Nishizawa, Yukiyasu; Sanada, Yukihisa; Torii, Tatsuo; Jiang, J.*; Shimazoe, Kenji*; Takahashi, Hiroyuki*; Yoshino, Masao*; Ito, Shigeki*; Endo, Takanori*; et al.

Journal of Nuclear Science and Technology, 53(12), p.1907 - 1918, 2016/12

 Times Cited Count:28 Percentile:96(Nuclear Science & Technology)

The Compton camera was improved for use with the unmanned helicopter. Increase of the scintillator array from 4$$times$$4 to 8$$times$$8 and expanse of the distance between the two layers contributed to the improvements of detection efficiency and angular resolution, respectively. Measurements were performed over the riverbed of the Ukedo river of Namie town in Fukushima Prefecture. By programming of flight path and speed, the areas of 65 m $$times$$ 60 m and 65 m $$times$$ 180 m were measured during about 20 and 30 minutes, respectively. By the analysis the air dose rate maps at 1 m height were obtained precisely with the angular resolution corresponding to the position resolution of about 10 m from 10 m height. Hovering flights were executed over the hot spot areas for 10-20 minutes at 5-20 m height. By using the reconstruction software the $$gamma$$-ray images including the hot spots were obtained with the angular resolution same as that evaluated in the laboratory (about 10$$^{circ}$$).

Journal Articles

Laser storage ring with high power for realization of laser stripping injection

Harada, Hiroyuki; Saha, P. K.; Yamane, Isao*; Kato, Shinichi; Kinsho, Michikazu; Irie, Yoshiro*

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.983 - 986, 2016/11

The high-intensity proton accelerator adopts a charge exchange injection scheme, which injects with exchanging from negative Hydrogen ion to proton by using carbon foil. This scheme can realize high intensity proton beam but the uncontrolled beam losses are caused by scattering between beams and the foil. Additionally, the collision may occur the foil beak. Therefore, a new injection scheme for higher intensity is needed as an alternative to the foil. In the J-PARC 3GeV RCS, we newly propose and develop a laser stripping injection scheme However, it is necessary that laser power is two order higher than latest laser one. To realize this big issue, we develop the laser storage ring, which can provide laser pulse of high repetition rate by recycling one. In this presentation, we will introduce the laser stripping injection scheme and describe the concept of the laser storage ring with high repetition rate.

Journal Articles

Improvement of the IPM for the high-intensity beam profile measurement in the J-PARC RCS

Kato, Shinichi; Harada, Hiroyuki; Hatakeyama, Shuichiro; Kawase, Masato; Yamamoto, Kazami; Kinsho, Michikazu

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1089 - 1093, 2016/11

In the J-PARC RCS, the residual gas ionization profile monitor (IPM) is adopted for the nondestructive detection of the 1D transverse distribution of the circulating proton beam. The IPM mainly consists of the divided electrodes generating the external electric field and the detection unit. For the profile measurement, the residual gas ionized by the beam is transported to the detection unit by the external transverse electric field and amplified by the Multi-Channel Plate (MCP) as the electron. After that, these electrons are detected and the 1D distribution is reconstructed. To improve IPM performance, some updates have been performed continuously such as the optimization of the electric field potential and the introduction of the new MCP which has the gradual gain response to the applied voltage. As a result, the IPM shows intended performance in the beam commissioning with the low current condition. However, the distribution cannot be measured in the high current condition such as over 100 kW because the noise increases and hides the signal. To solve this problem, we investigated the source of this noise and examined measures. To compare the simulation and the noise measurement results, we identified the cause of the noise as the electric field from the beam. Therefore, we developed additional electrode component to shield that field based on the simulation result. This component will be installed in 2016 summer. It is expected that the noise is reduced to be 1/100 compared with present one by the new component and the distribution measurement can be performed in the high current condition.

Journal Articles

1 MW beam tuning for beam loss mitigation in the J-PARC 3 GeV RCS

Hotchi, Hideaki; Harada, Hiroyuki; Kato, Shinichi; Kinsho, Michikazu; Okabe, Kota; Saha, P. K.; Shobuda, Yoshihiro; Tamura, Fumihiko; Tani, Norio; Watanabe, Yasuhiro; et al.

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.61 - 65, 2016/11

After the RF power supply upgrade, the J-PARC 3-GeV RCS restarted a 1-MW beam test in October 2015. In the beam test in October, we successfully removed longitudinal beam loss by beam loading compensation as well as minimized space-charge induced beam loss by injection painting. In addition, in this beam test, beam instability was also well suppressed by controlling the tune and the chromaticity. Furthermore, in the following beam test, the transverse painting area was successfully expanded by introducing both quadrupole correctors and anti-correlated painting scheme, by which a foil scattering part of beam loss during charge-exchange injection was further reduced. By these recent efforts, the 1-MW beam operation is now estimated to be established within a permissible beam loss level. This paper presents recent progresses of 1-MW beam tuning with particular emphasis on our approaches to beam loss issues.

Journal Articles

Secondary sodium fire measures in JSFR

Chikazawa, Yoshitaka; Kato, Atsushi*; Yamamoto, Tomohiko; Kubo, Shigenobu; Ohno, Shuji; Iwasaki, Mikinori*; Hara, Hiroyuki*; Shimakawa, Yoshio*; Sakaba, Hiroshi*

Nuclear Technology, 196(1), p.61 - 73, 2016/10

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

JSFR adopts double boundary for all sodium components. However, design measures are investigated for the secondary sodium fire inside the reactor building, which might be assumed as design extension conditions (DECs). Candidates of sodium fire measures in the secondary sodium systems such as sodium drain, nitrogen injection, pressure release valve, catch pan and leak sodium drain system have been compared from the view point of safety. Wide range of sodium fires in the steam generator room and air cooler have been analyzed evaluating performances of the candidate sodium fire measures.

315 (Records 1-20 displayed on this page)