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Journal Articles

Development of experimental technology for simulated fuel-assembly heating to address core-material-relocation behavior during severe accident

Abe, Yuta; Yamashita, Takuya; Sato, Ikken; Nakagiri, Toshio; Ishimi, Akihiro

Journal of Nuclear Engineering and Radiation Science, 6(2), p.021113_1 - 021113_9, 2020/04

Journal Articles

A New measuring method for elemental ratio and Vickers hardness of metal-oxide-boride materials based on Laser-Induced Breakdown Spectroscopy (LIBS)

Abe, Yuta; Otaka, Masahiko; Okazaki, Kodai*; Kawakami, Tomohiko*; Nakagiri, Toshio

Proceedings of 2019 International Congress on Advances in Nuclear Power Plants (ICAPP 2019) (Internet), 7 Pages, 2019/05

Since the hardness of fuel debris containing boride from B$$_{4}$$C pellet in control rod is estimated to be two times higher as that of oxide, such as UO$$_{2}$$ and ZrO$$_{2}$$, it is necessary to select the efficient and appropriate operation for removal of fuel debris formed in the severe accident of nuclear power plants. We focused on the characteristics of LIBS, an innovative rapid chemical in-situ analysis technology that enables simultaneous detection of B, O, and other metal elements in fuel debris. Simulated solidified melt specimens were obtained in the plasma heating tests (CMMR-0/-2, performed by JAEA) of simulated fuel assembly (ZrO$$_{2}$$ is used to simulated UO$$_{2}$$ pellet, other materials such as stainless steel, B$$_{4}$$C are same as fuel assembly). The LIBS signals of (B/O)/Zr ratio showed good linear relationship with Vickers hardness. This technique can be also applied as in-situ assessment tool for elemental composition and Vickers hardness of metal-oxide-boride materials.

Journal Articles

Uranium waste engineering research at the Ningyo-Toge Environmental Engineering Center of JAEA

Umezawa, Katsuhiro; Morimoto, Yasuyuki; Nakayama, Takuya; Nakagiri, Toshio

Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 6 Pages, 2019/05

In December 2016, the Ningyo-toge Environmental Engineering Center of Japan Atomic Energy Agency (JAEA Ningyo-toge) announced new concept of "Uranium and Environmental Research Platform". As part of the concept, uranium waste engineering research are now undergoing. The objective of the research is to establish the processing technology for safely and reasonable disposal of uranium waste. In particular, estimation of the amount of uranium and harmful substances and development of technologies to reduce their concentration in the waste to the permissive level for the disposal in shallow ground disposal are needed. We are now developing the technologies to reduce the concentration of uranium and harmful substances shown below. (1) Survey on uranium inventory. Uranium waste is now stored in 10-odd thousands of 200 L drums. We are surveying amount and chemical form of uranium in the drums. (2) Development of decontamination technology of metal and concrete waste. We are investigating decontamination methods for metals and concrete contaminated with uranium. (3) Development of technologies to remove, detoxify and fix the harmful substances. We are surveying the types and amounts of harmful substances in waste. In addition, we are investigating the method to remove, detoxify, and fix harmful substances. (4) Measurement technology of uranium radioactivity. We are investigating and examining ways to improve the quantitative accuracy of measurement and shorten the measurement time. (5) Development of uranium removal technology from sludge. We are investigating new processing method to remove uranium from sludge which is applicable for several kind of sludge. The results of these technological developments and environmental research will be reflected to "small-scale field test" and "disposal demonstration test" which are planned for demonstration of the uranium waste disposal technology.

Journal Articles

Environmental research on uranium at the Ningyo-Toge Environmental Engineering Center, JAEA

Sato, Kazuhiko; Yagi, Naoto; Nakagiri, Toshio

Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 6 Pages, 2019/05

no abstracts in English

Journal Articles

The CMMR program; BWR core degradation in the CMMR-3 test

Yamashita, Takuya; Sato, Ikken; Abe, Yuta; Nakagiri, Toshio; Ishimi, Akihiro; Nagae, Yuji

Proceedings of International Conference on Dismantling Challenges; Industrial Reality, Prospects and Feedback Experience (DEM 2018) (Internet), 11 Pages, 2018/10

no abstracts in English

Journal Articles

Development of experimental technology for simulated fuel-assembly heating to address core-material-relocation behavior during severe accident

Abe, Yuta; Yamashita, Takuya; Sato, Ikken; Nakagiri, Toshio; Ishimi, Akihiro; Nagae, Yuji

Proceedings of 26th International Conference on Nuclear Engineering (ICONE-26) (Internet), 9 Pages, 2018/07

Journal Articles

The CMMR program; BWR core degradation in the CMMR-1 and the CMMR-2 tests

Yamashita, Takuya; Sato, Ikken; Abe, Yuta; Nakagiri, Toshio; Ishimi, Akihiro; Nagae, Yuji

Proceedings of 12th International Conference of the Croatian Nuclear Society; Nuclear Option for CO$$_{2}$$ Free Energy Generation (USB Flash Drive), p.109_1 - 109_15, 2018/06

no abstracts in English

Journal Articles

Application of nontransfer type plasma heating technology for core-material-relocation tests in boiling water reactor severe accident conditions

Abe, Yuta; Sato, Ikken; Nakagiri, Toshio; Ishimi, Akihiro; Nagae, Yuji

Journal of Nuclear Engineering and Radiation Science, 4(2), p.020901_1 - 020901_8, 2018/04

A new experimental program using non-transfer type plasma heating is under consideration in JAEA to clarify the uncertainty on core-material relocation (CMR) behavior of BWR. In order to confirm the applicability of this new technology, authors performed preparatory plasma heating tests using small-scale test pieces (107 mm $$times$$ 107 mm $$times$$ 222 mm (height)). An excellent perspective in terms of applicability of the non-transfer plasma heating to melting high melting-temperature materials such as ZrO$$_{2}$$ has been obtained. In addition, molten pool was formed at the middle height of the test piece indicating its capability to simulate the initial phase of core degradation behavior consistent with the real UO$$_{2}$$ fuel Phebus-FPT tests. Furthermore, application of EPMA, SEM/EDX and X-ray CT led to a conclusion that the pool formed consisted mainly of Zr with some concentration of oxygen which tended to be enhanced at the upper surface region of the pool. Based on these results, an excellent perspective in terms of applicability of the non-transfer plasma heating technology to the Severe Accident (SA) experimental study was obtained.

JAEA Reports

Uranium and environmental research platform; Social gathering of uranium and environmental research

Nakayama, Takuya; Yagi, Naoto; Sato, Kazuhiko; Hinoda, Shingo; Nakagiri, Toshio; Morimoto, Yasuyuki; Umezawa, Katsuhiro; Sugitsue, Noritake

JAEA-Review 2018-005, 163 Pages, 2018/03

JAEA-Review-2018-005.pdf:72.95MB

The Ningyo-toge Environmental Engineering Center of JAEA has been working together with local communities for more than 60 years. Through our R&D projects on from uranium exploration to uranium enrichment as a part of the nuclear fuel cycle (i.e., front-end), we have accumulated experiences in the fields of management of uranium related technology. Taking advantage of such our potential, we will start new R&D program on "Research on Uranium and the Environment." In December 2016 we announced our new concept of the "Uranium and Environmental Research Platform" as a framework aimed at contributing to regional and international society through R&D programs (environmental research and uranium waste engineering research) that are needed to steadily carry out decommissioning of uranium handling facilities.

JAEA Reports

Cutting operation of simulated fuel assembly heating examination by AWJ

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.

Journal Articles

Development of non-transfer type plasma heating technology to address CMR behavior during severe accident with BWR design conditions

Abe, Yuta; Sato, Ikken; Nakagiri, Toshio; Ishimi, Akihiro; Nagae, Yuji

Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 7 Pages, 2017/04

Journal Articles

Preparation for a new experimental program addressing core-material-relocation behavior during severe accident with BWR design conditions; Conduction of preparatory tests applying non-transfer-type plasma heating technology

Abe, Yuta; Sato, Ikken; Ishimi, Akihiro; Nakagiri, Toshio; Nagae, Yuji

Proceedings of 24th International Conference on Nuclear Engineering (ICONE-24) (DVD-ROM), 7 Pages, 2016/06

A new experimental program using non-transfer type plasma heating is under consideration in JAEA to clarify the uncertainty on core-material relocation (CMR) behavior of BWR. In order to confirm the applicability of this new technology, authors performed preparatory plasma heating tests using small-scale test pieces (107 mm $$times$$ 107 mm $$times$$ 222 mmh). Based on these preliminary results, an excellent perspective in terms of applicability of the non-transfer plasma heating technology to the SA (Severe Accident) experimental study was obtained. Furthermore, JAEA is preparing for the next step intermediate-scale preparatory tests in 2016 using ca. 50 rods and a control blade that would not only confirm its technical applicability, but also some insights relevant to the issue on CMR itself.

Journal Articles

Hydrogen flux through the heat transfer tube wall in the steam generator of Monju

Doi, Daisuke; Nakagiri, Toshio

Journal of Nuclear Science and Technology, 51(3), p.343 - 349, 2014/03

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

Journal Articles

Demonstration of partially transparent thick metallic sodium in the vacuum ultraviolet spectral range

Daido, Hiroyuki; Suzuki, Yoji; Kawachi, Tetsuya; Fukuda, Takeshi*; Nakagiri, Toshio; Kaku, Masanori*; Kubodera, Masakazu*

Optics Express (Internet), 21(23), p.28182 - 28188, 2013/11

 Times Cited Count:1 Percentile:91.2(Optics)

We describe the direct measurement of actual transmittance of sodium samples with thickness of a 2 mm and 3 mm in a spectral range $$>$$115 nm, resulting in $$>$$50% transmittance of 3 mm thick solid and liquid sodium samples including transmission of a pair of the windows at the wavelength of 120 nm, giving an extinction coefficient of $$sim$$10$$^{-6}$$ to $$sim$$10$$^{-7}$$ which represents the sodium with a few cm thickness to be partially transparent for this wavelength. To confirm the measurement, we perform simple imaging experiments by the ultra-violet light passing through a 8 mm-thick sodium sample to illuminate a mesh as an object, resulting in obtaining a clear image.

Journal Articles

Transmission imaging of sodium in the vacuum ultra-violet spectral range; New application for an intense VUV Source

Daido, Hiroyuki; Suzuki, Yoji; Kawachi, Tetsuya; Fukuda, Takeshi*; Nakagiri, Toshio; Kaku, Masanori*; Kubodera, Masakazu*; Pirozhkov, A. S.

Proceedings of SPIE, Vol.8849, p.884908_1 - 884908_11, 2013/09

no abstracts in English

Journal Articles

Evaluation of hydrogen transport behavior in the power rising test of Japanese prototype fast breeder reactor Monju

Doi, Daisuke; Nakagiri, Toshio

Proceedings of 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference (ICONE-20 & POWER 2012) (DVD-ROM), 6 Pages, 2012/07

no abstracts in English

Journal Articles

The Dependence of equilibrium partition coefficient of cesium and iodine between sodium pool and the inert cover gas on the concentration in the pool

Miyahara, Shinya; Nishimura, Masahiro; Nakagiri, Toshio

Nuclear Engineering and Design, 241(12), p.4731 - 4736, 2011/12

 Times Cited Count:2 Percentile:77.93(Nuclear Science & Technology)

We measured equilibrium partition coefficients of cesium and iodine between liquid sodium pool and the inert cover gas. The obtained empirical equations were consistent with Castleman's theoretical equations. The effect of cesium concentration upon the partition coefficients was consistent with the theoretical values. That of iodine concentration was incompatible with the theoretical consideration due to the formation of dimmer of NaI (Na$$_{2}$$I$$_{2}$$) in the cover gas.

Journal Articles

Lab-scale water-splitting hydrogen production test of modified hybrid sulfur process working at around 550$$^{circ}$$C

Takai, Toshihide; Kubo, Shinji; Nakagiri, Toshio; Inagaki, Yoshiyuki

International Journal of Hydrogen Energy, 36(8), p.4689 - 4701, 2011/04

 Times Cited Count:8 Percentile:74.23(Chemistry, Physical)

A thermo-chemical water-splitting hydrogen production process for sodium cooled FBR is under development based on Westinghouse sulfur process. A unique sulfur trioxide electrolysis is introduced in this process intended for the lowering the reaction temperature around the operation temperature of FBR (500$$sim$$550$$^circ$$C). Key engineering issues for eliminating barriers to industrialization of this process were examined using a laboratory-stage apparatus. Adequacy of the components structure and control method was confirmed from the test results. Further it was found that a continuous hydrogen production system based on this process is achievable.

Journal Articles

The Configuration and electronic state of SO$$_{3}$$ adsorbed on Au surface

Suzuki, Chikashi; Nakagiri, Toshio

Journal of Physics and Chemistry of Solids, 72(1), p.10 - 16, 2011/01

 Times Cited Count:3 Percentile:80.71(Chemistry, Multidisciplinary)

We evaluated the adsorption of SO$$_{3}$$ molecule on the Au (111) surface using the first-principles calculations by a slab model with a periodic boundary condition. We find that there are six stable adsorption configurations on the Au surface, where SO$$_{3}$$ molecules are adsorbed above the three-fold fcc and hcp hallow sites and atop site. In two of these configurations, S and two O atoms are bound to the Pt atoms, and in two other of them, all the three O atoms are bound to Pt surface atoms, and then, S atom is bound to Au surface atom on the atop site and O atoms are situated on the hallow sites. In addition, it is found that molecular orbitals of SO$$_{3}$$ and those of Au surface are hybridized in the active metal d-bands region, that the localized molecular orbitals in SO$$_{3}$$ are stabilized, and that the charge is transferred from Au to S 3p by SO$$_{3}$$ adsorption on Au surface though the other interaction of S and O (bound to Au) component with Au is little. In addition, the bond between S and O bound to Au become weak by SO$$_{3}$$ adsorption on Au surface because the charge polarization to O-Au bond weakens the bond between S and O bound to Au. This interaction is assumed to encourage the breakage of S-O bond.

Journal Articles

Equilibrium partition coefficients of cesium and iodine between sodium pool and the inert cover gas

Miyahara, Shinya; Nishimura, Masahiro; Nakagiri, Toshio

Proceedings of 18th International Conference on Nuclear Engineering (ICONE-18) (CD-ROM), 6 Pages, 2010/05

Equilibrium partition coefficients were experimentally measured using "Transpiration method" for volatile fission products of cesium and iodine between liquid sodium pool and the inert cover gas. The objectives of the experiments are to : (1) Obtain the equilibrium partition coefficients of cesium and iodine at high temperature between 600 and 850 $$^{circ}$$C and (2) Study the dependence of the partition coefficients upon the concentration in the sodium pool. The obtained empirical equations are consistent with Castleman's theoretical equations. The partition coefficients of cesium measured at five different points of mole concentration in the pool were almost consistent with the theoretical values. On the other hand, the measured partition coefficients of iodine increased with the increase in the concentration in the pool and this tendency was incompatible with the theoretical consideration. The reason of this discrepancy might be attributed to the formation of Na$$_{2}$$I$$_{2}$$ in the cover gas.

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