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JAEA Reports

Analysis of the radioactivity concentrations in low-level radioactive waste generated from JRR-3 and JPDR facilities

Tsuchida, Daiki; Haraga, Tomoko; Tobita, Minoru*; Omori, Hiroyuki*; Omori, Takeshi*; Murakami, Hideaki*; Mitsukai, Akina; Aono, Ryuji; Ishimori, Kenichiro; Kameo, Yutaka

JAEA-Data/Code 2020-022, 34 Pages, 2021/03

JAEA-Data-Code-2020-022.pdf:1.74MB

Radioactive wastes generated from nuclear research facilities in Japan Atomic Energy Agency are planning to be buried in the near surface disposal field. Therefore, it is required to establish the method to evaluate the radioactivity concentrations of radioactive wastes until the beginning of disposal. In order to contribute to this work, we collected and analyzed concrete samples generated from JRR-3 and JPDR. In this report, we summarized the radioactivity concentrations of 22 radionuclides($$^{3}$$H, $$^{14}$$C, $$^{36}$$Cl, $$^{41}$$Ca, $$^{60}$$Co, $$^{63}$$Ni, $$^{90}$$Sr, $$^{94}$$Nb, $$^{rm 108m}$$Ag, $$^{133}$$Ba, $$^{137}$$Cs, $$^{152}$$Eu, $$^{154}$$Eu, $$^{rm 166m}$$Ho, $$^{234}$$U, $$^{238}$$U, $$^{238}$$Pu, $$^{239+240}$$Pu, $$^{241}$$Am, $$^{243}$$Am, $$^{244}$$Cm) which were obtained from radiochemical analysis of the samples.

JAEA Reports

Analysis of the radioactivity concentrations in low-level radioactive waste generated from JPDR and JRR-4

Aono, Ryuji; Mitsukai, Akina; Haraga, Tomoko; Ishimori, Kenichiro; Kameo, Yutaka

JAEA-Data/Code 2020-006, 70 Pages, 2020/08

JAEA-Data-Code-2020-006.pdf:2.59MB

Radioactive wastes which generated from research and testing reactors in Japan Atomic Energy Agency are planning to be buried at the near surface disposal field. Therefore, it is required to establish the method to evaluate the radioactivity concentrations of radioactive wastes by the time it starts disposal. In order to contribute to this work, we collected and analyzed the samples generated from JPDR and JRR-4. In this report, we summarized the radioactivity concentrations of 19 radionuclides ($$^{3}$$H, $$^{14}$$C, $$^{36}$$Cl, $$^{60}$$Co, $$^{63}$$Ni, $$^{90}$$Sr, $$^{94}$$Nb, $$^{99}$$Tc, $$^{rm 108m}$$Ag, $$^{129}$$I, $$^{137}$$Cs, $$^{152}$$Eu, $$^{154}$$Eu, $$^{234}$$U, $$^{238}$$U, $$^{238}$$Pu, $$^{239+240}$$Pu, $$^{241}$$Am, $$^{244}$$Cm) which were obtained from radiochemical analysis of those samples.

JAEA Reports

Analysis of the radioactivity concentrations in low-level radioactive waste generated from Post Irradiation Examination Facility

Mitsukai, Akina; Haraga, Tomoko; Ishimori, Kenichiro; Kameo, Yutaka

JAEA-Data/Code 2019-012, 70 Pages, 2020/02

JAEA-Data-Code-2019-012.pdf:3.86MB

It is necessary to establish practical evaluation methods to determine radioactivity concentration of radioactive wastes which generated from research and testing reactors in Japan Atomic Energy Agency are planning to be buried for the near surface disposal. Therefore, it is required to establish the method to evaluate the radioactivity concentrations of radioactive wastes by the time it starts disposal. In order to contribute to this work, we collected and analyzed the samples generated from Post Irradiation Examination Facility. In this report, we summarized the radioactivity concentrations of 19 radionuclides which were obtained from radiochemical analysis of those samples.

JAEA Reports

Study on the evaluation methodology of the radioactivity concentration in low-level radioactive wastes generated from post irradiation examination facility

Mitsukai, Akina; Haraga, Tomoko; Ishimori, Kenichiro; Kameo, Yutaka

JAEA-Technology 2019-015, 52 Pages, 2019/11

JAEA-Technology-2019-015.pdf:2.46MB

In the future, radioactive waste which generated from nuclear research facilities in Japan Atomic Energy Agency are planning to be buried for the near surface disposal. It is necessary to establish the method to evaluate the radioactivity concentrations of the radioactive wastes. In this work, we studied the evaluation method of radioactivity concentration based on radiochemical analysis data (H-3, C-14, Cl-36, Co-60, Ni-63, Sr-90, Mo-93, Nb-94, Tc-99, Ag-108m, Sn-126, I-129, Cs-137, Eu-152, Eu-154, U-233+234, U-238, Pu-238, Pu-239+240, Pu-241, Am-241, Am-243, Cm-244) which was generated from research facility Hot Laboratory. As a result of examining the application of the scaling factor method, the correlation with Key-nuclide in some nuclides which are Sr-90, I-129, Eu-154, U-233+234, Pu-238, Pu-239+240, Am-241, Cm-244 confirmed by the correlation coefficient and t-test. In the present radiochemical analysis data, the mean activity concentration method can be applied to all nuclides which could not be applied to the scaling factor method H-3, C-14, Cl-36, Ni-63, Mo-93, Nb-94, Tc-99, Ag-108m, Sn-126, Eu-152, U-238, Pu-241 and Am-243. Ni-63, Tc-99, Eu-152 and U-238 could be applied to the scaling factor method with getting several additional data, this study will be continued to review for the practical evaluation method.

JAEA Reports

Analysis of the radioactivity concentrations in low-level radioactive waste generated from JRR-2 and JRR-3 facilities

Haraga, Tomoko; Shimomura, Yusuke; Mitsukai, Akina; Ishimori, Kenichiro; Kameo, Yutaka

JAEA-Data/Code 2019-004, 48 Pages, 2019/10

JAEA-Data-Code-2019-004.pdf:4.67MB

In the future, radioactive wastes which generated from research and testing reactors in Japan Atomic Energy Agency are planning to be buried for the near surface disposal. Therefore, it is required to establish the method to evaluate the radioactivity concentrations of radioactive wastes by the time it starts disposal. In order to contribute to this work, we collected and analyzed the samples generated from JRR-2 and JRR-3. In this report, we summarized the radioactivity concentrations of 19 radionuclides ($$^{3}$$H, $$^{14}$$C, $$^{36}$$Cl, $$^{60}$$Co, $$^{63}$$Ni, $$^{90}$$Sr, $$^{94}$$Nb, $$^{99}$$Tc, $$^{rm 108m}$$Ag, $$^{129}$$I, $$^{137}$$Cs, $$^{152}$$Eu, $$^{154}$$Eu, $$^{234}$$U, $$^{238}$$U, $$^{238}$$Pu, $$^{239+240}$$Pu, $$^{241}$$Am, $$^{244}$$Cm) which were obtained from radiochemical analysis of those samples.

Journal Articles

First ionization potentials of Fm, Md, No, and Lr; Verification of filling-up of 5f electrons and confirmation of the actinide series

Sato, Tetsuya; Asai, Masato; Borschevsky, A.*; Beerwerth, R.*; Kaneya, Yusuke*; Makii, Hiroyuki; Mitsukai, Akina*; Nagame, Yuichiro; Osa, Akihiko; Toyoshima, Atsushi; et al.

Journal of the American Chemical Society, 140(44), p.14609 - 14613, 2018/11

 Times Cited Count:16 Percentile:70.21(Chemistry, Multidisciplinary)

The first ionization potential (IP$$_1$$) yields information on valence electronic structure of an atom. IP$$_1$$ values of heavy actinides beyond einsteinium (Es, Z = 99), however, have not been determined experimentally so far due to the difficulty in obtaining these elements on scales of more than one atom at a time. Recently, we successfully measured IP$$_1$$ of lawrencium (Lr, Z = 103) using a surface ionization method. The result suggests that Lr has a loosely-bound electron in the outermost orbital. In contrast to Lr, nobelium (No, Z = 102) is expected to have the highest IP$$_1$$ among the actinide elements owing to its full-filled 5f and the 7s orbitals. In the present study, we have successfully determined IP$$_1$$ values of No as well as fermium (Fm, Z = 100) and mendelevium (Md, Z = 101) using the surface ionization method. The obtained results indicate that the IP$$_1$$ value of heavy actinoids would increase monotonically with filling electrons up in the 5f orbital like heavy lanthanoids.

Journal Articles

Vacuum chromatography of Tl on SiO$$_{2}$$ at the single-atom level

Steinegger, P.*; Asai, Masato; Dressler, R.*; Eichler, R.*; Kaneya, Yusuke*; Mitsukai, Akina*; Nagame, Yuichiro; Piguet, D.*; Sato, Tetsuya; Sch$"a$del, M.; et al.

Journal of Physical Chemistry C, 120(13), p.7122 - 7132, 2016/04

 Times Cited Count:18 Percentile:63.22(Chemistry, Physical)

A new experimental method "vacuum chromatography" has been developed to measure adsorption enthalpy of superheavy elements, and its feasibility has been examined using short-lived thallium isotopes. The short-lived thallium isotopes were produced at the JAEA tandem accelerator. The thallium ion beam prepared with an on-line isotope separator which ionized and mass-separated the thallium isotopes was injected into an isothermal vacuum chromatography apparatus. A temperature-dependent adsorption property of thallium atom on SiO$$_{2}$$ surface were measured. The adsorption enthalpy of thallium was determined to be 158 kJ/mol. The thallium is a homolog of element 113. Thus, the vacuum chromatography developed in this study enables us to perform chemical experiments for short-lived superheavy elements with half-lives of a order of one second.

Oral presentation

Electrolytic reduction of Mo and W as lighter homologues of seaborgium

Toyoshima, Atsushi; Miyashita, Sunao*; Oe, Kazuhiro*; Kitayama, Yuta*; Lerum, H. V.*; Goto, Naoya*; Kaneya, Yusuke; Komori, Yukiko*; Mitsukai, Akina*; Vascon, A.; et al.

no journal, , 

no abstracts in English

Oral presentation

Measurement of the first ionization potential of nobelium (No, $$Z$$ = 102)

Sato, Tetsuya; Asai, Masato; Kaneya, Yusuke; Tsukada, Kazuaki; Toyoshima, Atsushi; Vascon, A.; Takeda, Shinsaku; Mitsukai, Akina*; Nagame, Yuichiro; Ichikawa, Shinichi; et al.

no journal, , 

In order to determine the IP of the heavy elements, we have developed a novel measurement method based on a surface ionization technique by using a surface ionization ion source coupled to a He/CdI$$_2$$ gas-jet transport system for an Isotope Separator On-Line (ISOL) at the JAEA tandem accelerator facility. In this work, we have determined IP value of No by using the method. In a surface ionization process, an ionization efficiency of an atom depends on its IP. To obtain a relationship between IP and ionization efficiency in present system, we measured ionization efficiencies of various short-lived isotopes. Ionization efficiency of $$^{257}$$No produced in the $$^{248}$$Cm($$^{13}$$C, 4n) reaction was also measured. Measured ionization efficiency of $$^{257}$$No was 0.8%, which yields IP value of No to be 6.6 eV. This value is in a good agreement with the value which has been evaluated by extrapolation from those of the lighter actinide elements, 6.65 eV.

Oral presentation

Measurement of the first ionization energy of nobelium (No, $$Z$$ = 102)

Sato, Tetsuya; Asai, Masato; Kaneya, Yusuke; Tsukada, Kazuaki; Toyoshima, Atsushi; Takeda, Shinsaku; Mitsukai, Akina*; Nagame, Yuichiro; Ichikawa, Shinichi; Makii, Hiroyuki; et al.

no journal, , 

We successfully determined the first ionization energy (IE) of nobelium (No, $$Z$$ = 102) using a short-lived No isotope, $$^{257}$$No produced in the$$^{248}$$Cm($$^{13}$$C, 4n) reaction, based on the IE dependence of the ionization efficiency in a surface ionization process. The IE value of No was evaluated to be 6.6 eV. This value is in a good agreement with the value which has been estimated by an extrapolation from those of the lighter actinide elements, 6.65 eV.

Oral presentation

Developments towards aqueous phase chemistry of transactinide elements

Toyoshima, Atsushi; Oe, Kazuhiro*; Asai, Masato; Attallah, M. F.*; Goto, Naoya*; Gupta, N. S.*; Haba, Hiromitsu*; Kaneko, Masashi*; Kaneya, Yusuke; Kasamatsu, Yoshitaka*; et al.

no journal, , 

Due to short half-lives less than 10 s and extremely low production rates, transactinide elements heavier than seaborgium (Sg) are produced on an atom per hour scale. Therefore, a continuous rapid chemistry assembly is required to study aqueous-phase chemistry of these heaviest elements. In the present study, we started developments of a continuous chemistry assembly. Our first attempt was made in on-line experiments with Mo and W, lighter homologs of Sg, to optimize a chemistry assembly consisting of a newly developed membrane degasser as an interface between gas-jet and aqueous phase, a flow electrolytic column apparatus utilized to control oxidation states of Mo and W ions, and the continuous liquid-liquid extraction apparatus of SISAK for separation. In the conference, present status of the developments will be presented.

Oral presentation

Extraction behavior of Mo and W from H$$_{2}$$SO$$_{4}$$ into toluene with Aliquat336 as model experiments for seaborgium (Sg)

Mitsukai, Akina; Toyoshima, Atsushi; Kaneya, Yusuke; Oe, Kazuhiro*; Sato, Daisuke*; Goto, Naoya*; Tsuto, Shohei*; Komori, Yukiko*; Murakami, Masashi*; Haba, Hiromitsu*; et al.

no journal, , 

We report on the extraction behavior of carrier-free radioisotopes $$^{93m}$$Mo and $$^{181}$$W, which are lighter homologs of Sg, produced at the RIKEN K70 AVF cyclotron, in the H$$_{2}$$SO$$_{4}$$-Aliquat336 system. Results of the extraction experiments showed that the distribution ratios, ${it D}$, of Mo and W decrease up to $$sim$$3 M as increasing [H$$_{2}$$SO$$_{4}$$]. This is probably due to protonation reactions of hydrolyzed Mo and W species. In $$>$$ $$sim$$3 M H$$_{2}$$SO$$_{4}$$, the ${it D}$ values of W and Mo showed sharp increases. Based on the slope analysis separately carried out, it was suggested that hydrolyzed species of [HMO$$_{4}$$]$$^{-}$$ (M = Mo and W) are extracted in less than $$sim$$3 M [H$$_{2}$$SO$$_{4}$$], while anionic sulphate complexes of [MO$$_{2}$$(SO$$_{4}$$)$$_{2}$$]$$^{2-}$$ are formed in more than [H$$_{2}$$SO$$_{4}$$]$$>$$$$sim$$5 M.

Oral presentation

Ion-exchange experiments of Nb and Ta in HF/HNO$$_{3}$$ solution for identification of fluoride species of Db

Toyoshima, Atsushi; Mitsukai, Akina; Murakami, Masashi*; Sato, Daisuke*; Motoyama, Risa*; Oe, Kazuhiro*; Komori, Yukiko*; Haba, Hiromitsu*; Asai, Masato; Tsukada, Kazuaki; et al.

no journal, , 

The purpose of the present study is characterization of fluoride complexes of Db. In this study, we investigated anion-exchange behavior of Nb and Ta, lighter homologs of Db, in 1.0-24 M HF/2.0 M HNO$$_{3}$$ solutions as a model experiment of Db. $$^{95g}$$Nb and $$^{179}$$Ta produced at JAEA tandem accelerator and RIKEN AVF cyclotron, respectively, were prepared as non-carrier-added radiotracers by an ion exchange method. Batch experiments were performed with anion-exchange resin. As a result, distribution coefficients ($${it K}$$$$_{d}$$) of Nb showed a sharp increase at $$>$$ 6 M HF while those of Ta had a monotonic decrease as increasing HF concentration. This suggests that Nb forms fluoride complexes from oxy fluoride one at $$>$$ 6 M HF and Ta exists as fluoride complexes under the conditions. It is expected that chemical species of Db fluorides are characterized in its anion-exchange experiments under the present conditions.

Oral presentation

Extraction behavior of Mo and W into toluene with Aliquat336 from H$$_{2}$$SO$$_{4}$$ solution as model experiments for Sg

Mitsukai, Akina; Toyoshima, Atsushi; Kaneya, Yusuke; Oe, Kazuhiro*; Sato, Daisuke*; Murakami, Masashi*; Komori, Yukiko*; Haba, Hiromitsu*; Asai, Masato; Tsukada, Kazuaki; et al.

no journal, , 

In the present study, extraction behavior of Mo and W was studied in the sulfuric acid - Aliquat336 system as model experiments for the sulfuric complexation of Sg. In the RIKEN AVF cyclotron, batch-wise extraction experiments were performed with $$^{93m}$$Mo with a 6.8 h half-life. Similar batch experiments were carried out also with $$^{181}$$W produced in the JAEA tandem accelerator followed by chemical separation from a target material. As a result, both Mo and W form anionic sulfuric complexes at more than approximately 5 M H$$_{2}$$SO$$_{4}$$, which are extracted into the organic phase as R$$_{2}$$MO$$_{2}$$(SO$$_{4}$$)$$_{2}$$ (R = Aliquat336, M = Mo, W). It is expected that sulfuric complexation of Sg would be clarified under the present conditions.

Oral presentation

Extraction behavior of Mo and W from H$$_{2}$$SO$$_{4}$$ with Aliquat336 as homologues of seaborgium (Sg)

Mitsukai, Akina; Toyoshima, Atsushi; Asai, Masato; Tsukada, Kazuaki; Sato, Tetsuya; Kaneya, Yusuke; Takeda, Shinsaku*; Nagame, Yuichiro; Komori, Yukiko*; Murakami, Masafumi*; et al.

no journal, , 

We have started studying sulphate-complex formation of a transactinide element, seaborgium (Sg). In this study, we report on the extraction behavior of carrier-free radioisotopes $$^{93m}$$Mo and $$^{181}$$W which are lighter homologs of Sg, from aqueous H$$_{2}$$SO$$_{4}$$ solution with amine extractant, Aliquat336, dissolved in toluene by a batch method. These radioisotopes were produced in the $$^{nat}$$Zr($$alpha$$,${it 2}$)$$^{93m}$$Mo and $$^{181}$$Ta(${it d}$,x${it n}$)$$^{181}$$W reactions at the RIKEN K70 AVF cyclotron. Results of the extraction experiments showed that the distribution ratios of Mo and W increase sharply above ~3.0 M H$$_{2}$$SO$$_{4}$$. Based on the slope analysis, it was indicated that anionic sulphate-complex of [MO$$_{2}$$(SO$$_{4}$$)$$_{2}$$]$$^{2-}$$ (M = Mo, W) are formed in $$>$$ 5 M H$$_{2}$$SO$$_{4}$$. These results suggest that the present system is applicable to the extraction of Sg.

Oral presentation

First ionization potentials of heavy actinides

Sato, Tetsuya; Asai, Masato; Kaneya, Yusuke*; Tsukada, Kazuaki; Toyoshima, Atsushi; Mitsukai, Akina*; Takeda, Shinsaku*; Vascon, A.*; Sakama, Minoru*; Sato, Daisuke*; et al.

no journal, , 

The first ionization potential (IP$$_1$$) yields information on valence electronic structure of an atom. IP$$_1$$ values of heavy actinides beyond einsteinium (Es, Z = 99), however, have not been determined experimentally so far due to the difficulty in obtaining these elements on scales of more than one atom at a time. Recently, we successfully measured IP$$_1$$ of lawrencium (Lr, Z = 103) using a surface ionization method. The result suggests that Lr has a loosely-bound electron in the outermost orbital. In contrast to Lr, nobelium (No, Z = 102) is expected to have the highest IP$$_1$$ among the actinide elements owing to its full-filled 5f and the 7s orbitals. In the present study, we have successfully determined IP$$_1$$ values of No as well as fermium (Fm, Z = 100) and mendelevium (Md, Z = 101) using the surface ionization method. The obtained results indicate that the IP$$_1$$ value of heavy actinoids would increase monotonically with filling electrons up in the 5f orbital like heavy lanthanoids.

Oral presentation

Adsorption behavior of lawrencium (Lr) on a tantalum surface

Sato, Tetsuya; Kaneya, Yusuke*; Asai, Masato; Tsukada, Kazuaki; Toyoshima, Atsushi; Mitsukai, Akina*; Osa, Akihiko; Makii, Hiroyuki; Nishio, Katsuhisa; Hirose, Kentaro; et al.

no journal, , 

The ground state electronic configuration of lawrencium (Lr, Z =103) is predicted to be [Rn]$$5f^{14}7s^27p_{1/2}$$, which is different from that of the lanthanide homolog Lu [Xe]$$4f^{14}6s^25d$$ due to strong relativistic effects. According to semi-empirical considerations, volatility of Lr is expected to be higher than that of Lu. We have investigated adsorption behavior of $$^{256}$$Lr, which was produced in the reaction of $$^{249}$$Cf($$^{11}$$B, 4n), on a tantalum (Ta) metal surface using a surface ion-source installed into the isotope separator on-line (ISOL) at the JAEA tandem accelerator facility. The observed adsorption behavior of $$^{256}$$Lr was similar to those of Tb and Lu which have relatively higher adsorption enthalpy on Ta surface. It implies that Lr would have low volatility like such as Lu and Tb.

Oral presentation

Adsorption behavior of lawrencium (Lr, Z = 103) on a tantalum surface

Sato, Tetsuya; Kaneya, Yusuke*; Asai, Masato; Tsukada, Kazuaki; Toyoshima, Atsushi; Mitsukai, Akina*; Osa, Akihiko; Makii, Hiroyuki; Hirose, Kentaro; Nagame, Yuichiro; et al.

no journal, , 

Our experimental results on the first ionization potential measurement of lawrencium (Lr, element 103) have strongly suggested that the Lr atom has a [Rn]$$7s^25f^{14}7p_{1/2}$$ configuration as a result of the influence of strong relativistic effects. The configuration is different from that expected from the lanthanide homologue, lutetium (Lu). According to a semi-empirical consideration, it is expected that the change of the electronic configuration leads higher volatility of Lr than that of Lu. In this work, adsorption behaviors of Lr and various short-lived rare earth isotopes on a tantalum surface were investigated via observation of their surface ionization efficiencies. It was found that Lr would behave like low volatile rare earth elements such as Lu contrary to the semi-empirical expectation.

Oral presentation

Measurement of mass-symmetric spontaneous fission of $$^{259}$$Lr

Asai, Masato; Kamada, Hiroki*; Shigekawa, Yudai*; Tsukada, Kazuaki; Sato, Tetsuya; Toyoshima, Atsushi; Mitsukai, Akina; Nagame, Yuichiro; Nishio, Katsuhisa; Hirose, Kentaro; et al.

no journal, , 

To clarify the fission mechanism of mass-symmetric spontaneous fissions observed around the neutron-rich Fm region, we have measured kinetic energies and mass distribution of spontaneous-fission fragments in this nuclear region precisely. The experiment was performed at the JAEA tandem accelerator facility using an on-line isotope separator (ISOL). The mass-separated $$^{259}$$Lr nuclei were implanted into thin foil, and two fragments of their spontaneous fission were coincidently measured with two Si detectors. The spontaneous fission of $$^{259}$$Lr was found to show a narrow symmetric mass distribution. On the other hand, their total kinetic energy TKE was found to be low, which is apparently different from the high-TKE symmetric fissions observed in the Fm isotopes. This indicates that the fission mechanisms of these two symmetric fissions are different.

Oral presentation

Adsorption of lawrencium (Lr) on a metallic tantalum (Ta) surface

Kaneya, Yusuke*; Tomitsuka, Tomohiro; Sato, Tetsuya; Asai, Masato; Tsukada, Kazuaki; Toyoshima, Atsushi; Mitsukai, Akina; Makii, Hiroyuki; Hirose, Kentaro; Osa, Akihiko; et al.

no journal, , 

26 (Records 1-20 displayed on this page)