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Ochi, Kotaro; Barker, E.*; Nakama, Shigeo; Gleizes, M.*; Manach, E.*; Vincent, F.*; Sanada, Yukihisa
Journal of Disaster Research, 19(2), p.429 - 445, 2024/04
There are no clear criteria for standardizing mapping techniques for ambient dose equivalent rate (air dose rate) distributions in different countries. Thus, in this study, manborne, carborne, and airborne radiation surveys were conducted jointly by the Japan Atomic Energy Agency and the French Institute for Radiological Protection and Nuclear Safety in the vicinity of the Fukushima Daiichi Nuclear Power Station to confirm the effectiveness of each organization's monitoring methods. For example, in the manborne survey, the discrepancy between the air dose rates measured by the two institutions was observed depending on whether or not the contribution from radionuclides with different gamma-ray energies was considered when converting the count rates obtained by the detectors to air dose rates. As in this study, comparing mapping techniques among various countries and providing feedback to each other should help to improve the accuracy of zoning scenarios after nuclear accidents.
Nauchi, Yasushi*; Sato, Shunsuke*; Hayakawa, Takehito*; Kimura, Yasuhiko; Suyama, Kenya; Kashima, Takao*; Futakami, Kazuhiro*
Nuclear Instruments and Methods in Physics Research A, 1050, p.168109_1 - 168109_9, 2023/05
Times Cited Count:0 Percentile:0.02(Instruments & Instrumentation)Measurement of neutrons from spent nuclear fuel is performed in this study using the H method, which detects 2.223 MeV rays from neutron capture reaction of hydrogen using a highly pure germanium (HPGe) detector. The detection of the 2.223 MeV ray is affected by intense ray emission from fission products (FPs) because the emission rate of rays from the FP is seven orders of magnitude higher than the emission rate of neutrons. To shield the intense ray from the FP, the HPGe detector is placed off the axis of a collimator, whereas a polyethylene block is placed on the axis. In this geometry, the detector is shielded from the intense rays from the FP, but the detector can measure 2.223 MeV rays from the H reactions in the polyethylene block. The measured count rate of the 2.223 MeV rays is consistent with the expected rate within the statistical error, which is calculated based on the nuclide composition, which is primary Cm, estimated via depletion and decay calculations. Accordingly, the H method is considered feasible to quantify the number of neutron leakage from spent nuclear fuel assembly, which is applicable to certify burn up of the assembly.
Maeda, Makoto; Segawa, Mariko; Toh, Yosuke; Endo, Shunsuke; Nakamura, Shoji; Kimura, Atsushi
Scientific Reports (Internet), 12(1), p.6287_1 - 6287_8, 2022/06
Times Cited Count:2 Percentile:27.65(Multidisciplinary Sciences)Ji, Y.-Y.*; Ochi, Kotaro; Hong, S. B.*; Nakama, Shigeo; Sanada, Yukihisa; Mikami, Satoshi
Health Physics, 121(6), p.613 - 620, 2021/12
Times Cited Count:1 Percentile:15.09(Environmental Sciences)According to the implementing arrangement between JAEA (Japan Atomic Energy Agency) and KAERI (Korea Atomic Energy Research Institute) in the field of the radiation protection and environmental radiation monitoring, the joint measurement has been conducted to assess the radioactive cesium deposition in the ground around the Fukushima Daiichi Nuclear Power Plants (FDNPP). First, mobile gamma-ray spectrometry using backpack survey platform was conducted to assess the distribution of dose rate around specific three survey sites. The carborne survey using gamma-ray spectrometers, as loading inside a vehicle, was successfully conducted to compare measured dose rates in routes from site to site and verify evaluation methods including the attenuation correction.
Muramatsu, Haruka*; Hayashi, Tasuku*; Yuasa, Naoki*; Konno, Ryohei*; Yamaguchi, Atsushi*; Mitsuda, Kazuhisa*; Yamasaki, Noriko*; Maehata, Keisuke*; Kikunaga, Hidetoshi*; Takimoto, Misaki; et al.
Journal of Low Temperature Physics, 200(5-6), p.452 - 460, 2020/09
Times Cited Count:1 Percentile:5.7(Physics, Applied)Takahashi, Fumiaki
Genshiryoku No Ima To Ashita, p.106 - 109, 2019/03
The Atomic Energy Society of Japan has planned to publish a document for public, entitled "Current and tomorrow of atomic energy, -Experiences from the accident at the Tokyo Electronic Power Company Fukushima Dai-ichi NPPs-". The documents give us basics and usages of radiations, in addition to nuclear power plants and the accident at TEPCO Fukushima Dai-ichi NPPs. This manuscript explains interactions and penetrations in material for -rays, -rays, -rays and neutrons. In addition, exposure characteristics that is determined by properties of radiations are expressed here. This manuscript also explains characteristics in internal exposure and countermeasures of radiation protection following the TEPCO accident for Iodine-131 and Cesium-137.
Tanimura, Yoshihiko; Nishino, Sho; Yoshitomi, Hiroshi; Kowatari, Munehiko; Oishi, Tetsuya
Progress in Nuclear Science and Technology (Internet), 6, p.134 - 138, 2019/01
At the severe nuclear accidents like the Fukushima Daiichi Nuclear Power Plant, various radionuclides will be dispersed into the environment and raise the dose rate. The - measurements of ray spectra and identifying radionuclides using the results are important for the radiological protection from both external and internal exposure. For this application a commercially available CdZnTe spectrometer (Kromek GR-1) was characterized at the calibration fields of FRS/JAEA. The angular dependence of the detection efficiency was studied and the efficiency was kept within 15 % degradation in 135 degree incident angle, which covers 85 % of all. The usable dose range was evaluated and the spectrometer could correctly measure the ray spectra below 200 Gy/h.
Makii, Hiroyuki; Nishio, Katsuhisa; Hirose, Kentaro; Orlandi, R.; Lguillon, R.*; Ogawa, Tatsuhiko; Soldner, T.*; Hambsch, F.-J.*; Ache, M.*; Astier, A.*; et al.
Nuclear Instruments and Methods in Physics Research A, 906, p.88 - 96, 2018/10
Times Cited Count:3 Percentile:29.51(Instruments & Instrumentation)We have developed a new setup to measure prompt fission -ray spectra in neutron induced fission up to energies sufficient to reveal the structure associated with giant dipole resonances of fission fragments. The setup consists of multi-wire proportional counters, to detect both fission fragments in coincidence, and two large volume (101.6 mm in diameter and 127.0 mm in length) LaBr(Ce) scintillators, to measure the -rays. The setup was used to obtain the prompt fission -ray spectrum for thermal neutron induced fission of U at the PF1B cold-neutron beam facility of the Institut Laue-Langevin, Grenoble, France. We have successfully measured the -ray spectrum up to energies of about 20 MeV, what extends the currently known -ray spectrum limit to higher energies by approximately a factor of two.
Yamamoto, Takahiro; Ito, Chikara; Maeda, Shigetaka; Ito, Hideaki; Sekine, Takashi
JAEA-Technology 2017-036, 41 Pages, 2018/02
In the experimental fast reactor Joyo, the damaged upper core structure (UCS) was retrieved into the cask in May 2014 The dose rate on UCS surface was quite high due to the activation for over 30 years operation. In order to attain the optimum safety design, manufacture and operation of equipment for UCS replacement, the method to evaluate UCS surface dose rate was developed on the basis of C/E obtained by the in-vessel dose rate measurement in Joyo. In order to verify the evaluation method, the axial gamma-ray distribution measurement on the surface of the cask, which contained UCS, was conducted using a plastic scintillating optical fiber (PSF) detector. This paper describes the comparison results between calculation and measurement as follows. (1) The measured axial gamma-ray distribution on the cask surface had a peak on proper location with considering the cask shielding structure and agree well with the calculated distribution. (2) The C/E of axial gamma-ray distribution on the cask surface was ranged from 1.1 to 1.7. It was confirmed that the calculation for UCS replacement equipment design had a margin conservatively. Then, the results showed that the developed evaluation method for UCS replacement equipment design was sufficiently reliable.
Tomita, Jumpei; Abe, Takuya
JAEA-Research 2016-026, 12 Pages, 2017/03
An analytical method of low-level Ra isotopes in freshwater samples with combination of pre-concentration from large volume of water sample (170 L) using Powdex resin and -ray spectrometry followed by simple coprecipitation of Ra was developed. pre-concentration of Ra by batch method using Powder resin was examined, and it was shown that the amount of the resin required collecting Ra in the water sample could be determined by measuring the electric conductivity (EC) of water sample. It was found that coprecipitation of Ra with barium sulfate could remove more than 96% of potassium that increases the background. The validation of this method was confirmed by the analyses of 170 L of water sample containing the known amount of Ra isotopes with different EC. Among the analyses, the recovery of Ra was 98% in average and detection limits of Ra and Ra were achieved to be approximately 0.3 and 0.5 mBq L, respectively.
Ambai, Hiromu; Nishizuka, Yusuke*; Sano, Yuichi; Uchida, Naoki; Iijima, Shizuka
QST-M-2; QST Takasaki Annual Report 2015, P. 90, 2017/03
The spent fuel stored in the storage pools at the Fukushima Daiichi Nuclear Power Plant of Tokyo Electric Power Company Holdings, Inc. is exposed with the environment containing seawater components, owing to the injection of seawater into the storage pools. Therefore, during reprocessing, it is expected that the spent fuel will be contaminated with seawater components, and the influence of seawater on reprocessing needs to be investigated. We conducted the corrosion tests of the HAW storage tanks under -ray irradiation, and revealed that no significant effect of seawater components was emerged.
Takeuchi, Tomoaki; Otsuka, Noriaki; Tsuchiya, Kunihiko; Tanaka, Shigeo*; Ozawa, Osamu*; Komanome, Hirohisa*; Watanabe, Takashi*; Ueno, Shunji*
Nihon Hozen Gakkai Dai-13-Kai Gakujutsu Koenkai Yoshishu, p.391 - 394, 2016/07
no abstracts in English
Katabuchi, Tatsuya*; Yanagida, Shotaro*; Terada, Kazushi; Iwamoto, Nobuyuki; Igashira, Masayuki*
EPJ Web of Conferences, 93, p.02008_1 - 02008_2, 2015/05
Times Cited Count:0 Percentile:0.16(Physics, Multidisciplinary)Ba has the smallest neutron capture cross section among the stable Ba isotopes. The neutron capture reaction of Ba is dominated by resolved resonances in the astrophysically relevant energy region. Thus, reliable experimental data of the capture cross section are necessary. In the present work, we measured the neutron capture cross section of Ba in the energy region from 15 to 100 keV by the time-of-flight method at the Tokyo Institute of Technology. The capture cross sections were obtained from the pulse height spectra by the pulse-height weighting technique. A comparison of the present results with previous experimental data and evaluated data was made. We also derived -ray spectra by unfolding the pulse height spectra. It was revealed that the shape of -ray spectra strongly depends on neutron energy.
Oshima, Masumi; Toh, Yosuke; Kimura, Atsushi; Ebihara, Mitsuru*; Oura, Yasuji*; Ito, Yasuo*; Sawahata, Hiroyuki*; Matsuo, Motoyuki*
Journal of Radioanalytical and Nuclear Chemistry, 271(2), p.317 - 321, 2007/02
Times Cited Count:11 Percentile:60.92(Chemistry, Analytical)By combining neutron activation analysis with multiple -ray detection, we have proved better sensitivity and resolution for the trace element analysis than the ordinary single -ray detection method. We now try to apply the multiple -ray detection method to the prompt -ray analysis (PGA). We have established a new cold neutron beam line for PGA in Japan Research Reactor, JRR-3M, at Tokai establishment of Japan Atomic Energy Research Institute(JAERI). It consists of a beam shutter, a beam attenuator, a -ray detector array, a sample changer, and a beam stopper. We construct a high-efficiency -ray detector array specially designed for this purpose. Its performance has been evaluated with the Monte Carlo simulation code, GEANT 4.5.0.
Hatsukawa, Yuichi; Toh, Yosuke; Oshima, Masumi; Kimura, Atsushi; Gharaie, M. H. M.
Journal of Radioanalytical and Nuclear Chemistry, 271(1), p.43 - 45, 2007/01
Times Cited Count:3 Percentile:25.42(Chemistry, Analytical)- coincidence of multiple -rays from the radioisotopes produced by neutron capture reactions was measured with a array of 19-Ge detectors with BGO Compton suppressors, GEMINI-II. Using multiparameter spectrometry, high sensitive determination of iridium in geological samples and I-129 in environmental samples were carried out at GEMINI.
Kikuchi, Kenji; Nakamura, Hirofumi; Tsujimoto, Kazufumi; Kobayashi, Kazuhiro; Yokoyama, Sumi; Saito, Shigeru; Yamanishi, Toshihiko
Journal of Nuclear Materials, 356(1-3), p.157 - 161, 2006/09
Times Cited Count:5 Percentile:36.17(Materials Science, Multidisciplinary)A high-energy proton of 580MeV at SINQ target generates almost all constituents through spallation process with hydrogen and helium gases. For the SINQ target hydrogen and helium are generated to hundreds appm H and tens appm He, respectively. However, tritium gas production has not been yet reported. Evaluation of tritium gas generation in the specimens of target 3 was done by calculation. Results were compared with gamma spectrum measurement. Residual tritium measurement was carried by the thermal desorption method. It is found that a release of tritium began over 250C and material included 4 MBq/g. The ratio of residual tritium to generated one is estimated to be less than 20%.
Toh, Yosuke; Oshima, Masumi; Koizumi, Mitsuo; Osa, Akihiko; Kimura, Atsushi; Goto, Jun*; Hatsukawa, Yuichi
Applied Radiation and Isotopes, 64(7), p.751 - 754, 2006/07
Times Cited Count:9 Percentile:53.28(Chemistry, Inorganic & Nuclear)no abstracts in English
Shirasu, Noriko; Kuramoto, Kenichi*; Yamashita, Toshiyuki; Ichise, Kenichi; Ono, Katsuto; Nihei, Yasuo
Journal of Nuclear Materials, 352(1-3), p.365 - 371, 2006/06
Times Cited Count:4 Percentile:30.55(Materials Science, Multidisciplinary)To evaluate irradiation behavior of the ROX fuel, irradiation experiment was carried out using 20% enriched U instead of Pu. Three fuels were prepared; a single phase fuel of YSZ containing UO (U-YSZ), two particle-dispersed fuels of U-YSZ particle in spinel or corundum matrix. The U-YSZ particles were prepared by crashing presintered U-YSZ pellets and by sieving them. These fuels were irradiated in Japan Research Reactor No.3 for 13 cycles, about 300 days. Though many cracks were observed in the pellets by X-ray photographs, significant appearance changes were not observed for all fuel pins. Distribution of typical FPs was analyzed by the scanning over the fuel pin. Non-volatile nuclide remained in the fuel pellet. On the other hand, a part of Cs moved to the gaps between the pellets and to the insulators. Cs and Cs showed different distributions at the plenum. Fuel pellets were taken out from fuel pins without bonding. Spinel decomposition and subsequent restructuring were not observed probably due to low irradiation temperature.
Iwai, Yasunori; Yamanishi, Toshihiko; Isobe, Kanetsugu; Nishi, Masataka; Yagi, Toshiaki; Tamada, Masao
Fusion Engineering and Design, 81(1-7), p.815 - 820, 2006/02
Times Cited Count:15 Percentile:70.33(Nuclear Science & Technology)Solid-polymer-electrolyte (SPE) water electrolysis is attractive in electrolytic process of water detritiation system (WDS) in fusion reactors because it can electrolyze liquid waste directly, but radioactive durability of its ion exchange membrane is a key point. Radioactive durability of Nafion, a typical commercial ion exchange membrane, was experimentally investigated using Co-60 irradiation facility and electron beam irradiation facility at Takasaki Radiation Chemistry Research Establishment of JAERI. Nafion is composed of PTFE (Polytetrafluoroethylene) main chain. However the degradation of its mechanical strength by irradiation was significantly distinguished from that of PTFE and no serious damage was observed for its ion exchange capacity up to 530 kGy, the requirement of ITER. Atmospheric effects such as soaking and oxygen on degrading behaviors were discussed from the viewpoint of radical reaction mechanism. Dependencies of operating temperature and radioactive source are also demonstrated in detail.
Belleguic, M.*; Azaiez, F.*; Dombrdi, Zs.*; Sohler, D.*; Lopez-Jimenez, M. J.*; Otsuka, Takaharu*; Saint-Laurent, M. G.*; Sorlin, O.*; Stanoiu, C.*; Utsuno, Yutaka; et al.
Physical Review C, 72(5), p.054316_1 - 054316_7, 2005/11
Times Cited Count:41 Percentile:89.51(Physics, Nuclear)no abstracts in English