Distribution and settling behavior of americium-241 in the tropical East Pacific

Kinoshita, Norikazu*; Nagaoka, Mika; Nakanishi, Takashi*

Science of the Total Environment, 753, p.142087_1 - 142087_10, 2021/01

https://doi.org/10.1016/j.scitotenv.2020.142087

The distribution of the anthropogenic radionuclide americium-241 (Am), a decay product of Pu discharged from atmospheric tests of nuclear weapons, was investigated to resolve its horizontal and vertical migration in the Tropical East Pacific. We analyzed Am concentrations in seawater samples collected in 2003. On comparing the Am concentrations with the previously determined concentrations of Pu in the same samples, the vertical profiles of Am were found to be similar to those of Pu. At some stations, the maximum concentration of Am occurred 100-200 m deeper than that of Pu. The Am/Pu ratios in the North Pacific and South Pacific were comparable to one another, and were typical of the ratio for the Pacific. The Am distribution was influenced by the water mass at depths below 400 m. The Am data support the view there is a current flowing at depths of 400-3000 m from the North Pacific through the equator to the South Pacific. In addition, the Am vertical profile was explained by using a box model that considers the decay of Pu and adsorption and scavenging by suspended particles. The different depths for the maximum concentrations of Am and Pu observed at some stations were well explained by the model and by the distribution of CaCO particles. The residence time of Am in the Pacific was also estimated by using the model.

Shielding experiments under JASMIN collaboration at Fermilab, 4; Measurement and analyses of high-energy neutron spectra in the anti-proton target station

Matsuda, Norihiro; Kasugai, Yoshimi; Sakamoto, Yukio; Nakashima, Hiroshi; Matsumura, Hiroshi*; Iwase, Hiroshi*; Kinoshita, Norikazu*; Hirayama, Hideo*; Yashima, Hiroshi*; Mokhov, N.*; et al.

Journal of the Korean Physical Society, 59(2), p.2055 - 2058, 2011/08

https://doi.org/10.3938/jkps.59.2055

It is important to obtain neutron spectra and its intensity on shielding experiment. Deduction of high-energy neutron spectra were done using fitting and unfolding methods based on the shielding data obtained at the anti-proton (pbar) target station in Fermilab. The neutron spectra for fitting method is useful to be easily obtained and the values gave reasonable results compared with nuclear data. Therefore, that for unfolding methods included inconsistency. Furthermore, the deduced neutron spectra were verified through the calculation analyses by PHITS code.

Shielding experiments under JASMIN collaboration at Fermilab, 3; Measurement of high-energy neutrons penetrating a thick iron shield from the antiproton production target by Au activation method

Matsumura, Hiroshi*; Kinoshita, Norikazu*; Iwase, Hiroshi*; Toyoda, Akihiro*; Kasugai, Yoshimi; Matsuda, Norihiro; Sakamoto, Yukio; Nakashima, Hiroshi; Yashima, Hiroshi*; Mokhov, N.*; et al.

Journal of the Korean Physical Society, 59(2), p.2059 - 2062, 2011/08

https://doi.org/10.3938/jkps.59.2059

In an antiproton production (Pbar) target station of the Fermi National Accelerator Laboratory (FNAL), the secondary particles produced by bombarding a target with 120-GeV protons are shielded by a thick iron shield. In order to obtain experimental data on high-energy proton accelerator facilities, we indirectly measured 100-MeV neutrons at the outside of the iron shield. The measurement was performed by using the Au activation method coupled with a low-background -ray counting system. As an indicator for the neutron flux, we determined the production rates of 8 spallation nuclides (Au, Pt, Ir, Os, Hf, Lu, Lu, and Yb) in the Au activation detector. The measured production rates were compared with the theoretical production rates calculated using PHITS. We proved that the Au activation method can serve as a powerful tool for indirect measurements of 100-MeV neutrons that play a vital role in neutron transport.

Shielding experiments at high energy accelerators of Fermilab, 2; Spatial distribution measurement of reaction rate behind the shield and its application for Moyer model

Yashima, Hiroshi*; Kasugai, Yoshimi; Matsuda, Norihiro; Matsumura, Hiroshi*; Iwase, Hiroshi*; Kinoshita, Norikazu*; Mokhov, N.*; Leveling, A.*; Boehnlein, D.*; Vaziri, K.*; et al.

Progress in Nuclear Science and Technology (Internet), 1, p.48 - 51, 2011/02

https://doi.org/10.15669/pnst.1.48

The shielding experiment was performed at the anti-proton production target station in Fermi National Accelerator Laboratory. Aluminum, Bismath, Niobium, Copper and Indium samples were placed behind the shields. After irradiation, induced activities of samples were measured by using HPGe detector. The spatial distribution of reaction rate of samples which were placed behind the iron and concrete shields were obtained. The measured data shows that the reaction rates on the outer surfaces of the iron and concrete shields increases toward the downstream of the target. The obtained reaction rates were also fitted to Moyer's formula, and the attenuation lengths for iron and concrete shields were obtained.

Experimental studies of shielding and irradiation effects at high energy accelerator facilities

Nakashima, Hiroshi; Sakamoto, Yukio; Iwamoto, Yosuke; Matsuda, Norihiro; Kasugai, Yoshimi; Nakane, Yoshihiro; Masukawa, Fumihiro; Mokhov, N.*; Leveling, A.*; Boehnlein, D.*; et al.

Nuclear Technology, 168(2), p.482 - 486, 2009/11

BB2007-3640.pdf:0.22MB

https://doi.org/10.13182/NT09-A9229

Experimental studies of shielding and radiation effects have been started using 120-GeV proton synchrotron at Fermi National Accelerator Laboratory (FNAL) under collaboration between FNAL and Japan. The first campaign of the experiment was carried out at the Pbar target station and Numi experimental station at FNAL, using antiproton and neutrino production targets irradiated by 120-GeV protons. The generated secondary particles passing through steel, concrete and rock were measured by activation methods as well as by other detectors such as scintillator with a veto counter, phoswich detector and a Bonner ball counter on trial. Preliminary experimental results are presented.

Adsorption of Db and its homologues Nb and Ta, and the pseudo-homologue Pa on anion-exchange resin in HF solution

Tsukada, Kazuaki; Haba, Hiromitsu*; Asai, Masato; Toyoshima, Atsushi; Akiyama, Kazuhiko*; Kasamatsu, Yoshitaka; Nishinaka, Ichiro; Ichikawa, Shinichi; Yasuda, Kenichiro; Miyamoto, Yutaka; et al.

Radiochimica Acta, 97(2), p.83 - 89, 2009/02

https://doi.org/10.1524/ract.2009.1577

Anion-exchange chromatography of element 105, dubnium (Db), produced in the Cm(F, 5n)Db reaction is investigated together with the homologues Nb and Ta, and the pseudo-homologue Pa in 13.9 M hydrofluoric acid (HF) solution. The distribution coefficient (K) of Db on an anion-exchange resin is successfully determined by running cycles of the 1702 chromatographic column separations. The result clearly indicates that the adsorption of Db on the resin is significantly different from that of the homologues and that the adsorption of anionic fluoro complexes of these elements decreases in the sequence of Ta Nb Db Pa.

Elution curve of Rutherfordium (Rf) in anion-exchange chromatography with hydrofluoric acid solution

Toyoshima, Atsushi; Haba, Hiromitsu*; Tsukada, Kazuaki; Asai, Masato; Akiyama, Kazuhiko; Nishinaka, Ichiro; Nagame, Yuichiro; Saika, Daisuke*; Matsuo, Keishi*; Sato, Wataru*; et al.

Journal of Nuclear and Radiochemical Sciences, 5(2), p.45 - 48, 2004/12

https://doi.org/10.14494/jnrs2000.5.45

no abstracts in English

Anion-exchange behavior of element 105, Db, in HF/HNO media

Kasamatsu, Yoshitaka; Toyoshima, Atsushi; Asai, Masato; Tsukada, Kazuaki; Haba, Hiromitsu*; Ishii, Yasuo; Tome, Hayato; Nishinaka, Ichiro; Akiyama, Kazuhiko*; Kikunaga, Hidetoshi*; et al.

no journal, , 

Dubnium-262 was produced in the Cm(F, 5) reaction at the JAEA tandem accelerator. Adsorption of Db on the anion-exchange resin was investigated in 0.89 M HF/0.3 M HNO solution. The anion-exchange behavior of Nb, Ta, and Pa as homologues of Db was also examined in details in HF/HNO solutions. From the comparison of those results, we found that the adsorption of Db on the anion-exchange resin is considerably weaker than that of Ta and is relatively similar to those of Nb and Pa in the studied conditions.

Adsorption of element-105 (Db) on anion-exchange resin in HF/HNO solutions

Kasamatsu, Yoshitaka; Toyoshima, Atsushi; Asai, Masato; Tsukada, Kazuaki; Haba, Hiromitsu*; Ishii, Yasuo; Tome, Hayato; Nishinaka, Ichiro; Akiyama, Kazuhiko*; Kikunaga, Hidetoshi*; et al.

no journal, , 

Dubnium-262 was produced in the nuclear reaction of Cm(F,5n)Db using the JAEA Tandem accelerator. The reaction products were rapidly transported to the chemistry laboratory and the anion-exchange behavior of Db in HF/HNO media was investigated with an on-line rapid ion-exchange apparatus. Based on the comparison of the behavior of Db with that of its homologues (Nb, Ta, and Pa), the fluoride complex formation of Db was discussed.

Shielding experiments at high energy accelerators of FERMI, 9; Deduction of high energy neutron spectra

Kasugai, Yoshimi; Yashima, Hiroshi*; Matsuda, Norihiro; Kinoshita, Norikazu*; Matsumura, Hiroshi*; Iwase, Hiroshi*; Nakashima, Hiroshi; Sakamoto, Yukio; Hirayama, Hideo*; Ishibashi, Kenji*; et al.

no journal, , 

On the shielding experiment, started on 2007, as collaborative research with Fermilab using high energy proton accelerators, the measurement of reaction rate distributions in the antiproton target station has been carried out. Reaction rates were measured with activation method. Using the reaction rate data, neutron spectra at each measurement position were deduced by means of nonlinear least square method; a shape of the neutron spectrum between 5 and 100 MeV was expressed as a fitting function with 5 fitting parameters, whose values were determined at a minimum of values for the reaction rates. In the presentation, systematics of the variation of neutron spectra in the shield will be discussed.