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Journal Articles

Effect of dissolved oxygen concentration on dynamic strain aging and stress corrosion cracking of SUS304 stainless steel under high temperature pressurized water

Hirota, Noriaki; Nakano, Hiroko; Fujita, Yoshitaka; Takeuchi, Tomoaki; Tsuchiya, Kunihiko; Demura, Masahiko*; Kobayashi, Yoshinao*

The IV International Scientific Forum "Nuclear Science and Technologies"; AIP Conference Proceedings 3020, p.030007_1 - 030007_6, 2024/01

https://doi.org/10.1063/5.0192888

Dynamic strain aging (DSA) and intergranular stress corrosion cracking (intragranular SCC) occur in high temperature pressurized water simulating a boiling water reactor environment due to changes in dissolved oxygen (DO) content, respectively. In order to clearly understand the difference between these phenomena, the mechanism of their occurrence was summarized. As a result, it was found that DSA due to intragranular cracking occurred in SUS304 stainless steel at low DO $$<$$ 1 ppb, while DSA was suppressed at DO 100 to 8500 ppb due to the formation of oxide films on the surface. On the other hand, when DO was increased to 20000 ppb, the film was peeled from the matrix, O element diffused to the grain boundary of the matrix, resulting in intergranular SCC. These results are indicated that the optimum DO concentration must be adjusted to suppress crack initiation due to DSA and intergranular SCC.

Journal Articles

Extraction of $$^{99}$$Mo hot atoms made by a neutron capture method from $$alpha$$-MoO$$_{3}$$ to water

Quach, N. M.*; Ngo, M. C.*; Yang, Y.*; Nguyen, T. B.*; Nguyen, V. T.*; Fujita, Yoshitaka; Do, T. M. D.*; Nakayama, Tadachika*; Suzuki, Tatsuya*; Suematsu, Hisayuki*

Journal of Radioanalytical and Nuclear Chemistry, 332(10), p.4057 - 4064, 2023/10

https://doi.org/10.1007/s10967-023-09125-7
 Times Cited Count：0 Percentile：0.01(Chemistry, Analytical)

Technetium-99m ($$^{99m}$$Tc) is the most widely used medical radioisotope in the world and is produced from molybdenum-99 ($$^{99}$$Mo). Production of $$^{99}$$Mo via the neutron capture method draws attention as an alternative to fission-derived $$^{99}$$Mo due to non-proliferation issues, but the specific radioactivity of $$^{99}$$Mo is extremely low. In this work, a porous $$alpha$$-MoO$$_{3}$$ wire was prepared as an irradiation target in order to improve the specific activity by extracting $$^{99}$$Mo. Porous $$alpha$$-MoO$$_{3}$$ wire is synthesized from Mo metal wire by a two-step heating procedure. The hot atom effect of $$^{99}$$Mo was confirmed by activity and isotope measurements of the porous $$alpha$$-MoO$$_{3}$$ wire after neutron irradiation and the water used for extraction. In term of the extraction effectiveness, the effectiveness of $$^{99}$$Mo extraction in the porous $$alpha$$-MoO$$_{3}$$ wire was comparable to that of commercial $$alpha$$-MoO$$_{3}$$ powder.

JAEA Reports

Study on molybdenum adsorption properties of alumina-based adsorbents and their application to $$^{99}$$Mo/$$^{rm 99m}$$Tc generators using the (n,$$gamma$$) method (Thesis)

Fujita, Yoshitaka

JAEA-Review 2023-010, 108 Pages, 2023/08

JAEA-Review-2023-010.pdf:6.62MB

$$^{rm 99m}$$Tc (technetium-99m) is the most widely used radioisotope in radiopharmaceutical and is decayed from the parent nuclide $$^{99}$$Mo (molybdenum-99). Most of $$^{99}$$Mo is generated as one of the fission products of uranium, but recently, from the viewpoint of nuclear security and nuclear nonproliferation, a uranium-free $$^{99}$$Mo production method is desired. One such method is the (n,$$gamma$$) method, in which $$^{98}$$Mo is irradiated by neutrons. However, since the specific activity of $$^{99}$$Mo produced by this method is extremely low, it is necessary to improve the Mo adsorption and $$^{rm 99m}$$Tc elution property of alumina (Al$$_{2}$$O$$_{3}$$), which is used as a Mo adsorbent, to apply this method to the $$^{99}$$Mo/$$^{rm 99m}$$Tc generator, a device for separation and concentration of $$^{rm 99m}$$Tc from $$^{99}$$Mo. Therefore, the objective of this thesis is to elucidate the parameters effective for improving the performance of alumina for the practical use of the $$^{99}$$Mo/$$^{rm 99m}$$Tc generator using the (n,$$gamma$$) method, and to contribute to the development of alumina columns that may be applicable to low specific activity $$^{99}$$Mo. In this study, alumina with different starting materials was prepared and its applicability as Mo adsorbent for $$^{99}$$Mo/$$^{rm 99m}$$Tc generator was evaluated. The effects of crystal structure and specific surface area of alumina on Mo adsorption properties were clarified, and the Mo adsorption mechanism was elucidated based on the results of surface analysis of alumina. In addition, $$^{rm 99m}$$Tc elution properties and $$^{rm 99m}$$Tc solution quality were evaluated using MoO$$_{3}$$ irradiated in the Kyoto University Research Reactor (KUR), and a new column shape with potential application to generators was proposed based on the experiment results of alumina columns designed for current generators.

Journal Articles

$$beta$$-MoO$$_{3}$$ whiskers in $$^{99}$$Mo/$$^{rm 99m}$$Tc radioisotope production and $$^{99}$$Mo/$$^{rm 99m}$$Tc extraction using hot atoms

Ngo, M. C.*; Fujita, Yoshitaka; Suzuki, Tatsuya*; Do, T. M. D.*; Seki, Misaki; Nakayama, Tadachika*; Niihara, Koichi*; Suematsu, Hisayuki*

Inorganic Chemistry, 62(32), p.13140 - 13147, 2023/08

https://doi.org/10.1021/acs.inorgchem.3c02125
 Times Cited Count：0 Percentile：0.01(Chemistry, Inorganic & Nuclear)

Technetium-99m ($$^{rm 99m}$$Tc) is one of the most important radioisotopes for diagnostic radio-imaging applications. $$^{rm 99m}$$Tc is a daughter product of the $$^{99}$$Mo isotope. There are two methods used to produce $$^{99}$$Mo/$$^{rm 99m}$$Tc: the nuclear fission (n,f) and the neutron capture (n,$$gamma$$) methods. Between them, the (n,f) method is the main route, used for approximately 90% of the world's production. However, the (n,f) method faces numerous problems, including the use of highly enriched uranium, the release of highly radioactive waste, and nonproliferation problems. Therefore, the (n,$$gamma$$) method is being developed as a future replacement for the (n,f) method. In this work, $$beta$$-MoO$$_{3}$$ whiskers prepared by the thermal evaporation method and $$alpha$$-MoO$$_{3}$$ particles were irradiated in a nuclear reactor to produce $$^{99}$$Mo/$$^{rm 99m}$$Tc via neutron capture. The irradiated targets were dispersed into water to extract the $$^{99}$$Mo/$$^{rm 99m}$$Tc. As a result, $$beta$$-MoO$$_{3}$$ whisker yielded higher $$^{99}$$Mo extraction rate than that from $$alpha$$-MoO$$_{3}$$. In addition, by comparing the dissolved $$^{98}$$Mo concentrations in water, we clarified a prominent hot-atom of $$beta$$-MoO$$_{3}$$ whiskers. This research is the first demonstration of $$beta$$-MoO$$_{3}$$ being used as an irradiation target in the neutron capture method. On the basis of the results, $$beta$$-MoO$$_{3}$$ is considered a promising irradiation target for producing $$^{99}$$Mo/$$^{rm 99m}$$Tc by neutron capture and using water for the radioisotope extraction process in the future.

Journal Articles

Study on $$^{rm 99m}$$Tc separation/concentration technology from $$^{99}$$Mo by (n, $$gamma$$) method

Fujita, Yoshitaka; Hu, X.*; Takeuchi, Tomoaki; Takeda, Ryoma; Fujihara, Yasuyuki*; Yoshinaga, Hisao*; Hori, Junichi*; Suzuki, Tatsuya*; Suematsu, Hisayuki*; Ide, Hiroshi

KURNS Progress Report 2022, P. 110, 2023/07

https://www.rri.kyoto-u.ac.jp/PUB/report/PR/ProgRep2022/ProgressReport2022.pdf#page=125

no abstracts in English

Journal Articles

Production of diagnostic $$^{99}$$Mo/$$^{99m}$$Tc by PWR

Nasu, Takuya*; Fujita, Yoshitaka

Enerugi Rebyu, 42(10), p.15 - 18, 2022/09

no abstracts in English

Journal Articles

Radiochemical research for the advancement of $$^{99}$$Mo/$$^{rm 99m}$$Tc generator by (n, $$gamma$$) method, 4

Fujita, Yoshitaka; Seki, Misaki; Ngo, M. C.*; Do, T. M. D.*; Hu, X.*; Yang, Y.*; Takeuchi, Tomoaki; Nakano, Hiroko; Fujihara, Yasuyuki*; Yoshinaga, Hisao*; et al.

KURNS Progress Report 2021, P. 118, 2022/07

https://www.rri.kyoto-u.ac.jp/PUB/report/PR/ProgRep2021/ProgressReport2021_online.pdf#page=134

no abstracts in English

Journal Articles

Development of stabilization treatment technology for radioactive aluminum waste

Seki, Misaki; Fujita, Yoshitaka; Fujihara, Yasuyuki*; Zhang, J.*; Yoshinaga, Hisao*; Sano, Tadafumi*; Hori, Junichi*; Nagata, Hiroshi; Otsuka, Kaoru; Omori, Takazumi; et al.

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 29(1), p.2 - 9, 2022/06

https://doi.org/10.3327/jnuce.29.1_2

no abstracts in English

Journal Articles

Mechanisms responsible for adsorption of molybdate ions on alumina for the production of medical radioisotopes

Fujita, Yoshitaka; Niizeki, Tomotake*; Fukumitsu, Nobuyoshi*; Ariga, Katsuhiko*; Yamauchi, Yusuke*; Malgras, V.*; Kaneti, Y. V.*; Liu, C.-H.*; Hatano, Kentaro*; Suematsu, Hisayuki*; et al.

Bulletin of the Chemical Society of Japan, 95(1), p.129 - 137, 2022/01

https://doi.org/10.1246/bcsj.20210249
 Times Cited Count：8 Percentile：76.16(Chemistry, Multidisciplinary)

In this work, the mechanisms responsible for the adsorption of molybdate ions on alumina are investigated using in-depth surface analyses carried out on alumina specimens immersed in solutions containing different molybdate ions at different pH values. The obtained results reveal that when alumina is immersed in an acidic solution containing molybdate ions, the hydroxyl groups present on the surface are removed to generate positively charged sites, and molybdate ions (MoO$$_{4}$$$$^{2-}$$ or AlMo$$_{6}$$O$$_{24}$$H$$_{6}$$$$^{3-}$$) are adsorbed by electrostatic interaction. Alumina dissolves slightly in an acidic solution to form AlMo$$_{6}$$O$$_{24}$$H$$_{6}$$$$^{3-}$$, which is more easily desorbed than MoO$$_{4}$$$$^{2-}$$. Furthermore, the enhancement in the Mo adsorption or desorption property may be achieved by enriching the surface of the alumina adsorbent with many -OH groups and optimizing Mo solution to adsorb molybdate ions on alumina as MoO$$_{4}$$$$^{2-}$$ ions. These findings will assist researchers in engineering more efficient and stable alumina-based adsorbents for molybdenum adsorption used in medical radioisotope ($$^{99}$$Mo/$$^{99m}$$Tc) generators.

Journal Articles

Dynamic properties on $$^{99}$$Mo adsorption and $$^{rm 99m}$$Tc elution with alumina columns

Fujita, Yoshitaka; Seki, Misaki; Sano, Tadafumi*; Fujihara, Yasuyuki*; Suzuki, Tatsuya*; Yoshinaga, Hisao*; Hori, Junichi*; Suematsu, Hisayuki*; Tsuchiya, Kunihiko

Journal of Physics; Conference Series, 2155, p.012018_1 - 012018_6, 2022/01

https://doi.org/10.1088/1742-6596/2155/1/012018

Technetium-99m ($$^{rm 99m}$$Tc), the daughter nuclide of Molybdenum-99 ($$^{99}$$Mo), is the most commonly used radioisotope in radiopharmaceuticals. The research and development (R&D) for the production of $$^{99}$$Mo by the neutron activation method ((n, $$gamma$$) method) has been carried out from viewpoints of no-proliferation and nuclear security, etc. Since the specific activity of $$^{99}$$Mo produced by the (n, $$gamma$$) method is extremely low, developing Al$$_{2}$$O$$_{3}$$ with a large Mo adsorption capacity is necessary to adapt (n, $$gamma$$)$$^{99}$$Mo to the generator. In this study, three kinds of Al$$_{2}$$O$$_{3}$$ specimens with different raw materials were prepared and compared their adaptability to generators by static and dynamic adsorption. MoO$$_{3}$$ pellet pieces (1.5g) were irradiated with 5 MW for 20 min in the Kyoto University Research Reactor (KUR). Irradiated MoO$$_{3}$$ pellet pieces were dissolved in 6M-NaOH aq. In dynamic adsorption, 1 g of Al$$_{2}$$O$$_{3}$$ was filled into a PFA tube ($$phi$$1.59 mm). The $$^{99}$$Mo adsorption capacity of Al$$_{2}$$O$$_{3}$$ specimens under dynamic condition was slightly reduced compared to that under static condition. The $$^{rm 99m}$$Tc elution rate was about 100% at 1.5 mL of milking in dynamic adsorption, while it was around 56-87% in static adsorption. The $$^{99}$$Mo/$$^{rm 99m}$$Tc ratio of dynamic condition was greatly reduced compared to that of static condition. Therefore, the $$^{rm 99m}$$Tc elution property is greatly affected by the method of adsorbing Mo, e.g., the column shape, the linear flow rate, etc.

Journal Articles

Radiochemical research for the advancement of $$^{99}$$Mo/$$^{rm 99m}$$Tc generator by (n, $$gamma$$) method, 3

Fujita, Yoshitaka; Seki, Misaki; Namekawa, Yoji*; Nishikata, Kaori; Daigo, Fumihisa; Ide, Hiroshi; Tsuchiya, Kunihiko; Sano, Tadafumi*; Fujihara, Yasuyuki*; Hori, Junichi*; et al.

KURNS Progress Report 2020, P. 136, 2021/08

no abstracts in English

Journal Articles

Effect on $$^{99}$$Mo-adsorption/$$^{99m}$$Tc-elution properties of alumina with different surface structures

Fujita, Yoshitaka; Seki, Misaki; Sano, Tadafumi*; Fujihara, Yasuyuki*; Kitagawa, Tomoya*; Matsukura, Minoru*; Hori, Junichi*; Suzuki, Tatsuya*; Tsuchiya, Kunihiko

Journal of Radioanalytical and Nuclear Chemistry, 327(3), p.1355 - 1363, 2021/03

AA2020-0805.pdf:0.77MB

https://doi.org/10.1007/s10967-021-07616-z
 Times Cited Count：3 Percentile：45.99(Chemistry, Analytical)

We prepared three types of Al$$_{2}$$O$$_{3}$$ with different surface structures and investigated $$^{99}$$Mo-adsorption/$$^{99m}$$Tc-elution properties using [$$^{99}$$Mo]MoO$$_{3}$$ that was irradiated in the Kyoto University Research Reactor. Al$$_{2}$$O$$_{3}$$ adsorbed [$$^{99}$$Mo]molybdate ions in solutions at different pH; the lower was the pH, the higher was the Mo-adsorption capacity of Al$$_{2}$$O$$_{3}$$. The $$^{99m}$$Tc-elution properties of molybdate ion adsorbed Al$$_{2}$$O$$_{3}$$ were elucidated by flowing saline. Consequently, it was suggested that $$^{99}$$Mo-adsorption/desorption properties are affected by the specific surface of Al$$_{2}$$O$$_{3}$$ and $$^{99m}$$Tc-elution properties are affected by the crystal structure of Al$$_{2}$$O$$_{3}$$.

Journal Articles

Radiochemical research for the advancement of $$^{99}$$Mo/$$^{rm 99m}$$Tc generator by (n,$$gamma$$) method, 2

Fujita, Yoshitaka; Seki, Misaki; Namekawa, Yoji*; Nishikata, Kaori; Kato, Yoshiaki; Sayato, Natsuki; Tsuchiya, Kunihiko; Sano, Tadafumi*; Fujihara, Yasuyuki*; Hori, Junichi*; et al.

KURNS Progress Report 2019, P. 157, 2020/08

https://www.rri.kyoto-u.ac.jp/PUB/report/PR/ProgRep2019/ProgressReport2019_online.pdf#page=173

no abstracts in English

Journal Articles

Radiochemical research for the advancement of $$^{99}$$Mo/$$^{rm 99m}$$Tc generator by (n,$$gamma$$) method

Fujita, Yoshitaka; Seki, Misaki; Namekawa, Yoji*; Nishikata, Kaori; Kimura, Akihiro; Shibata, Akira; Sayato, Natsuki; Tsuchiya, Kunihiko; Sano, Tadafumi*; Fujihara, Yasuyuki*; et al.

KURNS Progress Report 2018, P. 155, 2019/08

https://www.rri.kyoto-u.ac.jp/PUB/report/PR/ProgRep2018/KURNS_Progress_Report2018_web.pdf

no abstracts in English

Journal Articles

Biomolecule-assisted synthesis of hierarchical multilayered boehmite and alumina nanosheets for enhanced molybdenum adsorption

Saptiama, I.*; Kaneti, Y. V.*; Yuliarto, B.*; Kumada, Hiroaki*; Tsuchiya, Kunihiko; Fujita, Yoshitaka; Malgras, V.*; Fukumitsu, Nobuyoshi*; Sakae, Takeji*; Hatano, Kentaro*; et al.

Chemistry; A European Journal, 25(18), p.4843 - 4855, 2019/03

https://doi.org/10.1002/chem.201900177
 Times Cited Count：15 Percentile：55.35(Chemistry, Multidisciplinary)

The effective utilization of various biomolecules for creating a series of mesoporous boehmite ($$gamma$$-AlOOH) and gamma-alumina ($$gamma$$-Al$$_{2}$$O$$_{3}$$) nanosheets with unique hierarchical multilayered structures is demonstrated. The nature and concentration of the biomolecules strongly influence the degree of the crystallinity, the morphology, and the textural properties of the resulting $$gamma$$-AlOOH and $$gamma$$-Al$$_{2}$$O$$_{3}$$ nanosheets, allowing for easy tuning. The hierarchical $$gamma$$-AlOOH and $$gamma$$-Al$$_{2}$$O$$_{3}$$ multilayered nanosheets synthesized by using biomolecules exhibit enhanced crystallinity, improved particle separation, and well-defined multilayered structures compared to those obtained without biomolecules. More impressively, these $$gamma$$-AlOOH and $$gamma$$-Al$$_{2}$$O$$_{3}$$ nanosheets possess high surface areas up to 425 and 371 m$$^{2}$$/g, respectively, due to their mesoporous nature and hierarchical multilayered structure. When employed for molybdenum adsorption toward medical radioisotope production, the hierarchical $$gamma$$-Al$$_{2}$$O$$_{3}$$ multilayered nanosheets exhibit Mo adsorption capacities of 33.1$$sim$$40.8mg-Mo/g.

Journal Articles

Development of novel alumina adsorbent applying mesoporous process

Fukumitsu, Nobuyoshi*; Yamauchi, Yusuke*; Saptiama, I.*; Ariga, Katsuhiko*; Hatano, Kentaro*; Kumada, Hiroaki*; Fujita, Yoshitaka; Tsuchiya, Kunihiko

Isotope News, (760), p.15 - 18, 2018/12

no abstracts in English

Journal Articles

Neutron irradiation effect of high-density MoO$$_{3}$$ pellets for Mo-99 production

Fujita, Yoshitaka; Nishikata, Kaori; Namekawa, Yoji*; Kimura, Akihiro; Shibata, Akira; Sayato, Natsuki; Tsuchiya, Kunihiko; Sano, Tadafumi*; Fujihara, Yasuyuki*; Zhang, J.*

KURRI Progress Report 2017, P. 126, 2018/08

http://www.rri.kyoto-u.ac.jp/PUB/report/PR/ProgRep2017/Progress_Report2017_web.pdf#page=139

no abstracts in English

Oral presentation

Development of high performance Mo adsorbents

Fukumitsu, Nobuyoshi*; Yamauchi, Yusuke*; Saptiama, I.*; Ariga, Katsuhiko*; Hatano, Kentaro*; Kumada, Hiroaki*; Fujita, Yoshitaka; Tsuchiya, Kunihiko

no journal, , 

no abstracts in English

Oral presentation

Development of effective adsorbent for Molybdenum

Fukumitsu, Nobuyoshi*; Yamauchi, Yusuke*; Saptiama, I.*; Ariga, Katsuhiko*; Hatano, Kentaro*; Kumada, Hiroaki*; Fujita, Yoshitaka; Tsuchiya, Kunihiko

no journal, , 

no abstracts in English

Oral presentation

Mo adsorption and $$^{99m}$$Tc elution properties of alumina using (n, $$gamma$$)$$^{99}$$Mo

Fujita, Yoshitaka; Seki, Misaki; Sano, Tadafumi*; Suzuki, Tatsuya*; Kitagawa, Tomoya*; Nishikata, Kaori; Matsukura, Minoru*; Tsuchiya, Kunihiko

no journal, , 

no abstracts in English

37 (Records 1-20 displayed on this page)