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Journal Articles

Liquid decontamination using acidic electrolyzed water for various uranium-contaminated steel surfaces in dismantled centrifuge

Sakasegawa, Hideo; Nomura, Mitsuo; Sawayama, Kengo; Nakayama, Takuya; Yaita, Yumi*; Yonekawa, Hitoshi*; Kobayashi, Noboru*; Arima, Tatsumi*; Hiyama, Toshiaki*; Murata, Eiichi*

Progress in Nuclear Energy, 153, p.104396_1 - 104396_9, 2022/11

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

When dismantling centrifuges in uranium-enrichment facilities, decontamination techniques must be developed to remove uranium-contaminated surfaces of dismantled parts selectively. Dismantled uranium-contaminated parts can be disposed of as nonradioactive wastes or recycled after decontamination appropriate for clearance. previously, we developed a liquid decontamination technique using acidic electrolyzed water to remove uranium-contaminated surfaces. However, further developments are still needed for its actual application. Dismantled parts have various uranium-contaminated surface features due to varied operational conditions, inhomogeneous decontamination using iodine heptafluoride gas, and changes in long-term storage conditions after dismantling. Here, we performed liquid decontamination on specimens with varying uranium-contaminated surfaces cut from a centrifuge made of low-carbon steel. From the results, the liquid decontamination can effectively remove the uranium-contaminated surfaces, and radioactive concentrations fell below the target value within twenty minutes. Although the required time should also depend on dismantled parts' sizes and shapes in their actual application, we demonstrated that it could be an effective decontamination technique for uranium-contaminated steels of dismantled centrifuges.

JAEA Reports

Separation/removal of steel surface coating film by laser cleaning

Yamane, Ikumi; Takahashi, Nobuo; Sawayama, Kengo; Nishiwaki, Hiroki; Matsumoto, Takashi; Ogawa, Jumpei; Nomura, Mitsuo; Arima, Tatsumi*

JAEA-Technology 2021-038, 18 Pages, 2022/02

JAEA-Technology-2021-038.pdf:1.61MB

We have dismantled uranium enrichment facilities in Ningyo-toge Environmental Engineering Center since their operation finished in 2001, and the total amount of metallic wastes is estimated to be about 130 thousand tons. Eighty percent of them can be disposed as nonradioactive waste (NR), but there are some steel parts possibly uranium-contaminated. We need removing painted surface of such steels and radiologically surveying to dispose them as NRs. Though painted surfaces have been conventionally removed through hand working with grinders, this manual work requires installation of green house, protective clothing, and full-face mask, in order to prevent dispersion and inhalation of airborne dusts. We desire further developments of surface cleaning techniques to reduce time, cost, workload, and secondary waste generation caused by excessive grinding. Therefore, in this study, we focused on the laser cleaning technology used for the separation and removal of paint films at construction sites. In order to improve the coating separation and removal technology for NR objects, we evaluated the coating separation and removal performance of NR steel surface by laser cleaning system, observed the coating scattering behavior by high-speed camera and investigated the coating recovery method, evaluated the laser separation and removal performance of steel surface powder, and thermodynamically evaluated the uranium compounds on steel surface. We additionally evaluated the feasibility of laser cleaning techniques in our works basing on these results, and discussed future work plans for further developments of laser cleaning techniques.

Journal Articles

Study on decontamination of steel surface contaminated with uranium hexafluoride by acidic electrolytic water

Nakayama, Takuya; Nomura, Mitsuo; Mita, Yutaka; Yonekawa, Hitoshi*; Bunbai, Misako*; Yaita, Yumi*; Murata, Eiichi*; Hosaka, Katsumi*; Sugitsue, Noritake

Proceedings of 2019 International Congress on Advances in Nuclear Power Plants (ICAPP 2019) (Internet), 8 Pages, 2019/05

Clearance of contaminated metal is important for recycling and volume reduction of radioactive waste. Among applicable decontamination technologies, immersion method with ultrasonic cleaning is considered to be effective for metal materials having various shapes. in this study is to demonstrate decontamination of carbon steel contaminated by uranium hexafluoride to the target level for clearance (less than 0.04 Bq/cm$$^{2}$$), and minimize secondary waste. In this test, acidic electrolytic water, dilute hydrochloric acid, dilute sulfuric acid and ozone water with various pH and redox potential were used as decontamination solutions to be tested. We found that acidic electrolytic water is effective solution for decontamination of carbon steel contaminated by uranium hexafluoride. It could be decontaminate less than target level for clearance, and reduced secondary waste relatively.

Journal Articles

Technique for recovering uranium from sludge-like uranium-bearing wastes using hydrochloric acid

Ohashi, Yusuke; Nomura, Mitsuo; Tsunashima, Yasumichi; Ando, Shion; Sugitsue, Noritake; Ikeda, Yasuhisa*; Tanaka, Yoshio

Journal of Nuclear Science and Technology, 51(2), p.251 - 265, 2014/02

 Times Cited Count:8 Percentile:53.55(Nuclear Science & Technology)

Sludge-like uranium-bearing wastes generated from uranium refining and conversion R&D facilities are stored at the Ningyo-toge Environmental Engineering Center. We have proposed an aqueous process for recovering uranium from spent filter aid and CaF$${_2}$$ precipitate using hydrochloric acid. The distributions of the dissolved species in the sample solutions at different pH levels were calculated using the chemical equilibrium modeling system. Calculated results of fluorine contents of recovered uranium were compared with the experimental results. The fluorine content in the recovered uranium decreased as the aluminum concentration of the solution increased. On the other hand, uranium of spent filter aid was recovered selectively. The size of the particles of recovered uranium tends to decrease with increasing pH in the precipitation treatments. Also, the uranium concentration of the precipitate generated by the neutralization of the barren solution falls below 1 Bq/g.

Journal Articles

High-temperature X-ray imaging study of simulated high-level waste glass melt

Okamoto, Yoshihiro; Nakada, Masami; Akabori, Mitsuo; Komamine, Satoshi*; Fukui, Toshiki*; Ochi, Eiji*; Nitani, Hiroaki*; Nomura, Masaharu*

Denki Kagaku Oyobi Kogyo Butsuri Kagaku, 81(7), p.543 - 546, 2013/07

 Times Cited Count:6 Percentile:18.03(Electrochemistry)

The molten state of simulated high-level waste glass and the behavior of ruthenium element in the melt were investigated by using synchrotron radiation based X-ray imaging technique. Melting, generating and moving of bubbles, condensation and sedimentation of ruthenium element were observed dynamically in continuous 12-bit gray-scale images from the CCD camera. X-ray intensity was obtained easily by digitizing gray-scale values in the image. The existence of ruthenium element is emphasized as a black color in the CCD image at X-ray energy higher than the Ru K-absorption edge. Position sensitive imaging X-ray absorption fine structure (XAFS) measurement was also performed to clarify the chemical state of ruthenium element in the melt.

Journal Articles

High-temperature X-ray imaging study of simulated high-level waste glass melt

Okamoto, Yoshihiro; Nakada, Masami; Akabori, Mitsuo; Komamine, Satoshi*; Fukui, Toshiki*; Ochi, Eiji*; Nitani, Hiroaki*; Nomura, Masaharu*

Proceedings of 4th Asian Conference on Molten Salt Chemistry and Technology & 44th Symposium on Molten Salt Chemistry, Japan, p.47 - 52, 2012/09

The molten state of the simulated high-level waste glass and the behavior of ruthenium element in the melt were investigated by using synchrotron radiation based X-ray imaging technique. Melting, generating and moving of bubbles, condensation and sedimentation of ruthenium element were observed dynamically in continuous 12-bit gray-scale images from the CCD camera. The existence of ruthenium in the X-ray CCD image was emphasized over the energy of Ru K-absorption edge. X-ray intensity was obtained easily by digitalizing gray-scale values in the image. Position sensitive imaging X-ray absorption fine structure (XAFS) measurement was performed to clarify the chemical state of ruthenium element in the melt.

Journal Articles

Synchrotron radiation-based X-ray imaging study of ruthenium in simulated high-level waste glass

Okamoto, Yoshihiro; Nakada, Masami; Akabori, Mitsuo; Shiwaku, Hideaki; Komamine, Satoshi*; Fukui, Toshiki*; Ochi, Eiji*; Nitani, Hiroaki*; Nomura, Masaharu*

Nihon Genshiryoku Gakkai Wabun Rombunshi, 11(2), p.127 - 132, 2012/06

Distribution and the chemical state of Ru element in the simulated high-level waste glass were examined by using the synchrotron radiation based X-ray imaging technique. In this technique, a direct X-ray CCD camera is used in place of an ion chamber. Position sensitive X-ray absorption spectra were obtained by analyzing gray scale in images of the X-ray CCD camera. At first, we measured a test sample containing RuO$$_2$$ and Ru metal powder. We successfully obtained information on the Ru distribution in the sample. In addition, the chemical state (oxide or metal ?) of each small Ru-rich spot was evaluated by the corresponding position sensitive XAFS spectrum. The imaging XAFS technique was applied to some simulated high-level waste glass samples. The Ru distribution of the glass sample and their chemical state were confirmed by image analyses. It can be seen that Ru element scattered in the glass sample exists as oxide RuO$$_2$$.

Journal Articles

A New measurement of the astrophysical $$^8$$Li(d,t)$$^7$$Li reaction

Hashimoto, Takashi; Ishiyama, Hironobu*; Watanabe, Yutaka*; Hirayama, Yoshikazu*; Imai, Nobuaki*; Miyatake, Hiroari; Jeong, S.-C.*; Tanaka, Masahiko*; Yoshikawa, Nobuharu*; Nomura, Toru*; et al.

Physics Letters B, 674(4-5), p.276 - 280, 2009/04

 Times Cited Count:6 Percentile:43.52(Astronomy & Astrophysics)

The excitation function of the $$^8$$Li(d,t)$$^7$$Li reaction was directly measured using $$^8$$Li beams at E$$_{mathrm{cm}}$$ = 0.3, 0.4, 0.5, 0.7, 0.8, 1.0, 1.1, and 1.2 MeV with CD$$_2$$ targets. The beam energies covered the Gamow peaks for 1$$sim$$3$$times$$10$$^9$$ K. Large cross sections were observed at around E$$_{mathrm{cm}}$$ = 0.8 MeV, implying a resonance state located at 22.4 MeV in $$^{10}$$Be. The present astrophysical reaction rate is higher in one order magnitude than the presently adopted rate at around 1$$times$$10$$^9$$ K.

Journal Articles

A New measurement of the astrophysical $$^8$$Li($$alpha$$, n)$$^{11}$$B reaction

Ishiyama, Hironobu*; Hashimoto, Takashi; Ishikawa, Tomoko*; Watanabe, Yutaka*; Das, S. K.*; Miyatake, Hiroari; Mizoi, Yutaka*; Fukuda, Tomokazu*; Tanaka, Masahiko*; Fuchi, Yoshihide*; et al.

Physics Letters B, 640(3), p.82 - 85, 2006/09

 Times Cited Count:32 Percentile:85.01(Astronomy & Astrophysics)

The excitation function of the $$^{8}$$Li($$alpha$$,n)$$^{11}$$B reaction was measured while identifying the final state event by event in the region of E$$_{rm{cm}}$$ = 0.7 - 2.6 MeV using a highly efficient detector system and a low-energy $$^8$$Li beam. The results are much improved both in statistics and precisions, and show smaller cross sections than those of previous measurements by a factor of more than 2 in the low-energy region of E$$_{rm{cm}}le$$ 1.5 MeV. A resonance-like structure is found at around E$$_{rm{cm}}$$ = 0.85 MeV.

Journal Articles

A New measurement of the $$^8$$Li($$alpha$$,n)$$^{11}$$B reaction for astrophysical interest

Das, S. K.*; Fukuda, Tomokazu*; Mizoi, Yutaka*; Ishiyama, Hironobu*; Miyatake, Hiroari*; Watanabe, Yutaka*; Hirayama, Yoshikazu*; Tanaka, Masahiko*; Yoshikawa, Nobuharu*; Jeong, S.-C.*; et al.

AIP Conference Proceedings 847, p.374 - 376, 2006/07

no abstracts in English

Journal Articles

Production of a low-energy radioactive nuclear beam with high purity using JAERI-RMS

Ishiyama, Hironobu*; Ishikawa, Tomoko*; Hashimoto, Takashi; Watanabe, Yutaka*; Hirayama, Yoshikazu*; Imai, Nobuaki*; Miyatake, Hiroari; Tanaka, Masahiko*; Fuchi, Yoshihide*; Yoshikawa, Nobuharu*; et al.

Nuclear Instruments and Methods in Physics Research A, 560(2), p.366 - 372, 2006/05

 Times Cited Count:7 Percentile:47.55(Instruments & Instrumentation)

Thanks to the nature of inverse transfer-reactions, low-energy radioactive nuclear beams in light neutron-rich region were produced. The mass-separation and velocity-separation of the JAERI recoil mass-separator help to form high purity beams. The beams of $$^8$$Li, $$^{12}$$B, and $$^{16}$$N-RNBs are utilized to the experiments, so far, with those beam intensities and purities of 1.4$$times$$10$$^4$$ pps and 99$$%$$, 7.8$$times$$10$$^3$$ pps and 98$$%$$, and 4.7$$times$$10$$^3$$ pps and 98.5$$%$$, respectively.

Journal Articles

Gated multiple-sampling and tracking proportional chamber; New detector system for nuclear astrophysical study with radioactive nuclear beams

Hashimoto, Takashi; Ishiyama, Hironobu*; Ishikawa, Tomoko*; Kawamura, Takashi*; Nakai, Koji*; Watanabe, Yutaka*; Miyatake, Hiroari; Tanaka, Masahiko*; Fuchi, Yoshihide*; Yoshikawa, Nobuharu*; et al.

Nuclear Instruments and Methods in Physics Research A, 556(1), p.339 - 349, 2006/01

 Times Cited Count:32 Percentile:89.13(Instruments & Instrumentation)

A new type of three dimensional tracking and proportional gas counter has been developed. Adopting a gating-grid system, performance of the detector becomes stable under the injection rate of charged particles less than 4$$times$$10$$^4$$ pps. It is a useful detection system for astrophysical experiments using radioactive nuclear beams, since the efficiency is so high as 100 %.

Journal Articles

Precision hfs of $$^{126}$$Cs($$T$$$$_{1/2}$$ = 1.63 m) by ABMR

Pinard, J.*; Duong, H. T.*; Marescaux, D.*; Stroke, H. H.*; Redi, O.*; Gustafsson, M.*; Nilsson, T.*; Matsuki, S.*; Kishimoto, Yasuaki*; Kominato, K.*; et al.

Nuclear Physics A, 753(1-2), p.3 - 12, 2005/05

 Times Cited Count:4 Percentile:36.01(Physics, Nuclear)

The hfs separation $$Deltanu$$ of $$^{126}$$Cs($$T$$$$_{1/2} = 1.63$$ m) in the 6s $$^2$$S$$_{1/2}$$ ground state was obtained in a precision measurement near zero magnetic field by means of atomic beam magnetic resonance with laser optical pumping on-line with the CERN-PSB-ISOLDE mass separator. The result, $$Deltanu = 3629.514(0.001)$$ MHz, corrects significantly a previous published value from a high-field experiment. With our result, the precision of the nuclear magnetic moment, $$mu(^{126}$$Cs)$$sim 0.776 mu_N$$, is now limited by the influence of extended nuclear structure on the hfs (the Bohr-Weisskopf effect).

JAEA Reports

Stability of Uranium Complexes in Supercritical Fluids and their Effective Recovery(The joint research report about precedence basic engineering research)

Tomiyasu, Hiroshi*; Nomura, Mitsuo; Yamazaki, Hitoshi; Hayashibara, Kenichi

JNC TY6400 2004-004, 18 Pages, 2004/07

JNC-TY6400-2004-004.pdf:0.65MB

This study has been performed to establish a method to recover uranium from uranium containing NaF and CaF2 wastes without forming any secondary wastes. For this purpose the use of supercritical carbon dioxide was primarily considered. Although TBP has been generally used with supercritical carbon dioxide to extract uranium, the use of TBP was ruled out in the present study because of the formation of secondary wastes due to phosphorous oxides. Among a variety of ligands, we have choused acetylacetone as a ligand for the extraction of uranyl ion. Acetylacetone is a strong chelate ligand, which dose not gives any solid residual after vaporization. As a matter of fact, our experimental result indicates that acetylacetone is a stronger ligand for uranyl ion compared with TBP., because uranyl TBP complex is replaced by acetylacetonate resulting in the formation of acetylaetonate complex. Experiments were carried out to recover uranium from the NaF waste by use of supercritical carbon dioxide containing acetylacetone, and it was found that uranium was only partly extracted to carbon dioxide phase. This might be attributed to the strong uranium fluoride complexes and also to the distribution of uranium to the inside of NaF pellets. In order to recover uranium from the NaF waste, another method was also carried out as follows: dissolve NaF waste by hot water, then add NaOH to the solution as to form the precipitation of uranium hydrolyzed species, where uranium can be recovered at high yield using centrifugation, and finally the addition of ethanol yields the NaF powder. In conclusion, the recovery of uranium from fluoride wastes seems to be difficult by the method using supercritical carbon dioxide; however, we have established a new method to recover both uranium and NaF in high yield.

JAEA Reports

Recovery and Reuse of Uranium from Radioactive Carbon Dioxide (The joint research report about precedence basic engineering research)

Aihara, Masahiko*; Yanai, Shinjiro*; Shimazaki, Yohei*; Nomura, Mitsuo; Yamazaki, Hitoshi; Hayashibara, Kenichi

JNC TY6400 2004-003, 93 Pages, 2004/07

JNC-TY6400-2004-003.pdf:2.19MB

To run the nuclear fuel cycle safely, new treatment and disposal technologies of radioactive waste from the cycle must be developed. Super critical CO2 extraction attracts attention as a technology to recover the uranium in low level solid waste. In this paper it is proposed that use of carbonation of calcium oxide and decarbonation of calcium carbonate for the system which recovers and reuses high pressure carbon dioxide discharge form the super-critical process. Conducting the cycle reaction experiment at the high pressure of carbon dioxide with the calcium oxide absorbent, the reaction velocity analysis, the structural analysis of solid reactant, the numerical analysis of the reaction characteristic and the recover-reuse process were discussed. The rate of carbonation at about 2MPa was most rapid with the stable reaction conversion of about 0.4 through 5 cycles. In the range of these experiment conditions The solid reactant was observed consisting of about 1-10 mm particles of the aggregate of minute grains. It was found that a blockade of the void between the grains after carbonation at high pressure CO2 caused the reduction of conversion and rate of carbonation. The heat consumption of CO2 recovery for the recover-reuse system was estimated by use of the reaction analysis data.

Oral presentation

Study of astrophysical ($$alpha$$,n) reactions on light neutron-rich nuclei using low-energy radioactive nuclear beams

Hashimoto, Takashi; Mitsuoka, Shinichi; Ichikawa, Shinichi; Ikezoe, Hiroshi; Miyatake, Hiroari; Ishiyama, Hironobu*; Watanabe, Yutaka*; Hirayama, Yoshikazu*; Imai, Nobuaki*; Tanaka, Masahiko*; et al.

no journal, , 

no abstracts in English

Oral presentation

Direct measurements of astrophysical nuclear reaction rates on light neutron-rich nuclei at TRIAC and JAEA-RMS

Miyatake, Hiroari; Ishiyama, Hironobu*; Watanabe, Yutaka*; Hirayama, Yoshikazu*; Imai, Nobuaki*; Tanaka, Masahiko*; Yoshikawa, Nobuharu*; Jeong, S.-C.*; Fuchi, Yoshihide*; Nomura, Toru*; et al.

no journal, , 

no abstracts in English

Oral presentation

Direct measurement of the $$^{8}$$Li(d,t)(d,p)(d,$$alpha$$) reaction cross sections

Hashimoto, Takashi; Ishiyama, Hironobu*; Hirayama, Yoshikazu*; Watanabe, Yutaka*; Imai, Nobuaki*; Miyatake, Hiroari; Jeong, S.-C.*; Yoshikawa, Nobuharu*; Tanaka, Masahiko*; Nomura, Toru*; et al.

no journal, , 

no abstracts in English

Oral presentation

A Systematic study of astrophysical nuclear reaction rates via $$^8$$Li

Miyatake, Hiroari; Ishiyama, Hironobu*; Watanabe, Yutaka*; Hirayama, Yoshikazu*; Imai, Nobuaki*; Tanaka, Masahiko*; Yoshikawa, Nobuharu*; Jeong, S.-C.*; Fuchi, Yoshihide*; Nomura, Toru*; et al.

no journal, , 

A systematic study of astrophysical reaction rates on light neutron-rich nuclei using low-energy radioactive nuclear beams (RNB) is in progress at the tandem facility of Japan Atomic Energy Agency (JAEA). Direct measurements of reaction rates of $$^8$$Li($$alpha$$, n)$$^{11}$$B, $$^{12}$$B($$alpha$$, n)$$^{15}$$N and, $$^8$$Li(d, p), (d, t), (d, $$alpha$$), (p, $$alpha$$) have been carried out. Measured excitation functions and obtained reaction rates will be presented. Possible r-process path via $$^8$$Li at each temperature during r-process and the influence of r-process abundance will be discussed.

Oral presentation

Direct measurement of astrophysical $$^8$$Li(d,t)$$^7$$Li reaction

Hashimoto, Takashi; Miyatake, Hiroari; Mitsuoka, Shinichi; Nishio, Katsuhisa; Sato, Tetsuya; Ichikawa, Shinichi; Osa, Akihiko; Matsuda, Makoto; Ishiyama, Hironobu*; Watanabe, Yutaka*; et al.

no journal, , 

no abstracts in English

35 (Records 1-20 displayed on this page)