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Journeau, C.*; Molina, D.*; Brackx, E.*; Berlemont, R.*; Tsubota, Yoichi
Journal of Nuclear Science and Technology, 61(9), p.1239 - 1247, 2024/09
Times Cited Count：3 Percentile：53.66(Nuclear Science & Technology)CEA has manufactured a series of Fukushima Daiichi fuel debris simulants, either with depleted uranium oxide or with hafnium oxide as a surrogate of UO
. In ex-vessel compositions resulting from an interaction between corium and concrete, the oxidic phase density becomes lighter than that of the metallic phase, which segregates at the bottom. Three of these metallic phases have been mechanically cut at CEA Cadarache with handsaw and with core boring tool in FUJISAN facility. It appeared that two of these metallic blocks were extremely hard to cut (one from a fabrication with uranium oxide, the other from a simulant block) while the last one was more easily cut. The similarities and differences in metallographic analyses (SEM-EDS and XRD) of these three metal blocks will be presented and discussed. This experience provides useful learnings in view of the cutting and retrieval of fuel debris from Fukushima Daiichi
Porcheron, E.*; Leblois, Y.*; Journeau, C.*; Delacroix, J.*; Molina, D.*; Suteau, C.*; Berlemont, R.*; Bouland, A.*; Lallot, Y.*; Roulet, D.*; et al.
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR2022) (Internet), 5 Pages, 2022/10
One of the important challenges for the decommissioning of the damaged reactors of the Fukushima Daiichi Nuclear Power Station (1F) is the fuel debris retrieval. The URASOL project, which is undertaken by a French consortium consisting of ONET Technologies, CEA, and IRSN for JAEA/CLADS, is dedicated to acquiring basic scientific data on the generation and characteristics of radioactive aerosols from the thermal or mechanical processing of fuel debris simulant. Heating process undertaken in the VITAE facility simulates some representative conditions of thermal cutting by LASER. For mechanical cutting, the core boring technique is implemented in the FUJISAN facility. Fuel debris simulants have been developed for inactive and active trials. The aerosols are characterized in terms of mass concentration, real time number concentration, mass size distribution, morphology, and chemical properties. The chemical characterization aims at identifying potential radioactive particles released and the associated size distribution, both of which are important information for assessing possible safety and radioprotection measures during the fuel debris retrieval operations at 1F.
Journeau, C.*; Molina, D.*; Brackx, E.*; Berlemont, R.*; Tsubota, Yoichi
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR2022) (Internet), 5 Pages, 2022/10
CEA has manufactured a series of Fukushima Daiichi fuel debris simulants, either with depleted uranium oxide or with hafnium oxide as a surrogate of UO. In ex-vessel compositions resulting from an interaction between corium and concrete, the oxidic phase density becomes lighter than that of the metallic phase, which segregates at the bottom. Three of these metallic phases have been mechanically cut at CEA Cadarache with handsaw and with core boring tool in FUJISAN facility. It appeared that two of these metallic blocks were extremely hard to cut (one from a fabrication with uranium oxide, the other from a simulant block) while the last one was more easily cut. The similarities and differences in metallographic analyses (SEM-EDS and XRD) of these three metal blocks will be presented and discussed. This experience provides useful learnings in view of the cutting and retrieval of fuel debris from Fukushima Daiichi.
Zhou, Q.*; Saito, Takumi*; Suzuki, Seiya; Yano, Kimihiko; Suzuki, Shunichi*
Journal of Nuclear Science and Technology, 58(4), p.461 - 472, 2021/04
Times Cited Count：12 Percentile：72.22(Nuclear Science & Technology)Collaborative Laboratories for Advanced Decommissioning Science; The University of Tokyo*
JAEA-Review 2020-043, 116 Pages, 2021/01
JAEA-Review-2020-043.pdf:7.74MB
The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") in FY2019. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2018, this report summarizes the research results of the "Development of the technology for preventing radioactive particles' dispersion during the fuel debris retrieval" conducted in FY2019. In this study, a technique to effectively suppress the scattering of fine particles has been developed, and as a result of experiments, a method of spraying with water mist was found to be an effective and applicable method for improving aerosol removal efficiency and removal rate. As a method of solidifying fuel debris to suppress fine particle scattering during cutting, geopolymer was evaluated for its strength, thermal conductivity and cutting powder. In addition, flow status of geopolymer and the temperature distribution inside RPV covered by geopolymer were simulated.
Tamura, Koji*; Toyama, Shinichi
Nihon Genshiryoku Gakkai-Shi ATOMO
, 62(5), p.268 - 271, 2020/05
The laser cutting technology is expected to be a promising candidate for the decommissioning measure of nuclear facilities, because it has a lot of advantage such as its high controllability and excellent suitability to remote handling by robot arm, etcetera. This report describes the recent result from laser cutting technology development for thick steel materials summarizing the cutting demonstration of 300 mm thick steels and dummy pressure vessel, the analysis of cutting condition of thick steel cutting, the observation of cutting process, remote controlled cutting system, the cutting in pile of steels by the system, and countermeasure for fume produce by cutting process.
Abe, Yuta; Nakagiri, Toshio; Watatani, Satoshi*; Maruyama, Shinichiro*
JAEA-Technology 2017-023, 46 Pages, 2017/10
JAEA-Technology-2017-023.pdf:8.01MB
This is a report on Abrasive Water Jet (AWJ) cutting work carried out on specimen, which was used for Simulated Fuel Assembly Heating Examination by Collaborative Laboratories for Advanced Decommissioning Science (CLADS) molten core behavior analysis group in February 2016. The simulated fuel assembly is composed of Zirconia for the outer crucible/simulated fuel, stainless steel for the control blade and Zircaloy (Zr) for the cladding tube/channel box. Therefore, it is necessary to cut at once substances having a wide range of fracture toughness and hardness. Moreover, it is a large specimen with an approximate size of 300 mm. In addition, epoxy resin has high stickiness, making it more difficult to cut. Considering these effects, AWJ cutting was selected. The following two points were devised, and this specimen could be cut with AWJ. If it was not possible to cut at one time like a molten portion of boride, it was repeatedly cut. By using Abrasive Suspension Jet (ASJ) system with higher cutting ability than Abrasive Injection Jet (AIJ, conventional method) system, cutting time was shortened. As a result of this work, the cutting method in Simulated Fuel Assembly Heating Examination was established. Incidentally, in the cutting operation, when the cutting ability was lost at the tip of the AWJ, a curved cut surface, which occurs when the jet flowed away from the feeding direction, could be confirmed at the center of the test body. From the next work, to improve the cutting efficiency, we propose adding a mechanism such as turning the cutting member itself for re-cutting from the exit side of the jet and appropriate traverse speed to protect cut surface.
Maruyama, Shinichiro*; Watatani, Satoshi*
Mitsui Sumitomo Kensetsu Gijutsu Kenkyu Kaihatsu Hokoku, (15), p.107 - 112, 2017/10
It is essential to estimate characteristics and forms of fuel debris for safe and reliable removing at the decommissioning of the Fukushima Daiichi Nuclear Power Plant (1F). For the estimation, melting behavior of fuel assembly in the accident is being researched. To proceed the research, the fuel debris were need to cut, and the abrasive water jet (AWJ) which had enough results for cutting ceramic material or mixed material of zirconium alloy and stainless. The test results demonstrated that AWJ could cut the fuel assembly and accumulated the cutting data which will be subservient when removing the fuel debris in future.
Iwamoto, Hiroki; Nishihara, Kenji; Iwamoto, Yosuke; Hashimoto, Shintaro; Matsuda, Norihiro; Sato, Tatsuhiko; Harada, Masahide; Maekawa, Fujio
Journal of Nuclear Science and Technology, 53(10), p.1585 - 1594, 2016/10
Times Cited Count：19 Percentile：80.98(Nuclear Science & Technology)Nakamura, Yasuyuki; Iwai, Hiroki; Tezuka, Masashi; Sano, Kazuya
JAEA-Technology 2015-055, 89 Pages, 2016/03
JAEA-Technology-2015-055.pdf:17.54MB
It was reported that Fukushima Daiichi Nuclear Power Station (1F) had lost the cooling function of the reactor by the Tohoku Earthquake. It is assumed that the core internals became narrow and complicated debris structure mixed with the molten fuel. In consideration of the above situations, the AWJ cutting method, which has features of the long work distance and little heat effect for a material, has been developed for the removal of the molten core internals through cutting tests for 3 years since FY 2012. And it was confirmed that AWJ cutting method is useful for the removal of the core internals etc. The results in FY 2012 were reported in "R&D of the fuel debris removal technologies by abrasive water jet cutting technology (JAEA-Technology 2013-041)" and this report summarizes the results of FY 2012, 2013 and 2014 in this report. It was confirmed the possibility to apply the removal work of the fuel debris and the core internals.
Shoji, Tsugio; Fukui, Yasutaka; Ueda, Takiho
JAEA-Technology 2015-035, 70 Pages, 2016/01
JAEA-Technology-2015-035.pdf:8.07MB
The plasma jet cutting technology (Max output current is 250A) is developed for the dismantling of nuclear facilities in Oarai Research and Development Center. The plasma jet cutting technology is applicable to take out the debris. The plasma jet torch (Max output current is 600A) was produced for this application. This torch is available for the cutting of thick core internal materials in water. The ability of taking out debris and core internal material has been confirmed.
pink mutants through ion beam irradiationZaiton, A.*; Affrida, A. H.*; Shakinah, S.*; Nurul Hidayah, M.*; Hase, Yoshihiro; Ono, Yutaka
JAEA-Review 2014-050, JAEA Takasaki Annual Report 2013, P. 108, 2015/03
Yokoyama, Sumi; Noguchi, Hiroshi; Kurosawa, Naohiro*
Hoken Butsuri, 40(4), p.376 - 384, 2005/12
A computer code named ACUTRI has been developed to assess tritium doses due to inhalation to the general public. ACUTRI can calculate the radiological impact of tritium gas (HT) and tritiated water (HTO) released accidentally to the atmosphere. The models in this code consist of a tritium transfer model including the oxidation of HT to HTO and the reemission of HTO from soil to the atmosphere and a dose calculation model. The atmospheric dispersion of the primary HT and HTO plumes and secondary HTO plume, which is reemitted from soil to the atmosphere, is calculated by using the Gaussian plume model. In this calculation, it is possible to analyze statistically on meteorology in the same way as a conventional dose assessment method according to the meteorological guideline of the Nuclear Safety Commission of Japan. Tritium concentrations in air and their resultant doses were calculated using the ACUTRI code under some conditions. In order to validate the model, calculations were compared with experimental results.
Yonetani, Yoshiteru
Chemical Physics Letters, 406(1-3), p.49 - 53, 2005/04
Times Cited Count：54 Percentile：84.27(Chemistry, Physical)We report that a severe artifact appeared in molecular dynamics simulation of bulk water using the long cut-off length 18 AA ; Our result shows that increasing the cut-off length does not always improve the simulation result. Moreover, the use of the long cut-off length can lead to a spurious result. It is suggested that the simulation of solvated biomolecules using such a long cut-off length, which has been often performed, may contain an unexpected artifact.
Minehara, Eisuke; Hajima, Ryoichi; Iijima, Hokuto; Kikuzawa, Nobuhiro; Nagai, Ryoji; Nishimori, Nobuyuki; Nishitani, Tomohiro; Sawamura, Masaru; Yamauchi, Toshihiko
Proceedings of 27th International Free Electron Laser Conference (FEL 2005) (CD-ROM), p.305 - 308, 2005/00
The JAERI high power ERL-FEL has been extended to the more powerful and efficient free-electron laser (FEL) than 10kW for nuclear energy industries, and other heavy industries like defense, shipbuilding, chemical industries, environmental sciences, space-debris, and power beaming and so on. In order to realize such a tunable, highly-efficient, high average power, high peak power and ultra-short pulse FEL, we need the efficient and powerful FEL driven by the JAERI compact, stand-alone and zero boil-off super-conducting RF linac with an energy-recovery geometry. Our discussions on the ERL-FEL will cover the current status of the 10kW upgrading and its applications of non-thermal peeling, cutting, and drilling to decommission the nuclear power plants, and to demonstrate successfully the proof of principle prevention of cold-worked stress-corrosion cracking failures in nuclear power reactors under routine operation using small cubic low-Carbon stainless steel samples.
Yamakawa, Koji*; Chimi, Yasuhiro; Ishikawa, Norito; Iwase, Akihiro*
Journal of Alloys and Compounds, 370(1-2), p.211 - 216, 2004/05
Times Cited Count：1 Percentile：11.85(Chemistry, Physical)The migration of hydrogen in Pd-1at.% Fe-H and Pd-1at.% Ag-H alloys is investigated by electrical resistivity measurement around 50 K. The disordered hydrogen atoms are introduced by electron irradiation with 0.5 MeV electrons below 15 K. The disordered atoms order by migration of hydrogen atoms during the heating-up of the specimens. The recovery curves of electrical resistivity have two sub-stages for electron irradiated specimens and one stage for fast cooled specimens. The migration energy of hydrogen is obtained from the kinetic analysis of the resistivity change due to the ordering, using the cross-cut method for the electron irradiated specimen and fast cooled specimen. The obtained value of the migration energy for the low temperature stage is smaller than that for the high temperature stage. The value for the high temperature stage is similar to the energy for the case of fast cooling. The difference between the hydrogen atoms disordered by irradiation and that by fast cooling is discussed for Pd based alloys.
Oka, Kiyoshi
Reza Kenkyu, 31(9), p.612 - 617, 2003/09
no abstracts in English
Katayama, Yoshinori; Inamura, Yasuhiro
Journal of Physics; Condensed Matter, 15(1), p.S343 - S350, 2003/01
Times Cited Count：16 Percentile：59.97(Physics, Condensed Matter)Combination of synchrotron radiation sources and large volume presses enable us to make in-situ observations of structural change in liquids and glasses at high pressures up to several GPa and high temperatures up to 1500K. A number of methods, X-ray diffraction, XAFS, density measurement by means of X-ray absorption, viscosity measurements by means of radiography, are now applicable for this purpose. We have systematically studied elemental liquid and found that a characteristic structural change occurs in a narrow pressure-temperature range in liquid selenium. Moreover we have found a sudden structural change in liquid phosphorus. Experimental results on phosphorus support a view that the change is a first-order liquid-liquid transition. In the talk, results of current attempt to detect sudden structural change in silica glass will be presented. A preliminary result of X-ray diffraction study on liquid water under high-pressure will be also reported.
Kakudate, Satoshi; Shibanuma, Kiyoshi
Kensa Gijutsu, 7(11), p.28 - 33, 2002/11
no abstracts in English
Noguchi, Hiroshi; Yokoyama, Sumi*
KURRI-KR-80, p.50 - 56, 2002/08
no abstracts in English
