Challenging studies by accelerator mass spectrometry for the development of environmental radiology; Status report on the analysis of Sr and Cs by AMS

Honda, Maki; Martschini, M.*; Wieser, A.*; Marchhart, O.*; Lachner, J.*; Priller, A.*; Steier, P.*; Golser, R.*; Sakaguchi, Aya*

JAEA-Conf 2022-001, p.85 - 90, 2022/11

https://doi.org/10.11484/jaea-conf-2022-001

Accelerator mass spectrometry (AMS) is an analytical method that combines mass spectrometry with a tandem accelerator, which has been used mainly in nuclear physics experiments. AMS is used to measure radionuclides with half-lives of 10-10 years. For radionuclides with half-lives of this order, the method of measuring their mass is 10-10 times more sensitive than measuring their activity. Because of this advantage, AMS has been widely applied in Earth and planetary sciences, atomic energy research, and other fields. Among the various studies, Wallner et al. (2021, 2016) have achieved excellent work in Earth and planetary sciences. For example, they have attained the ultra-sensitive analysis of Fe and Pu in environmental samples. These are radionuclides produced by rapid-neutron-capture (r-process) nucleosynthesis. Our recent work shows that a new AMS system (VERA, University of Vienna), which combines laser isobaric separation and a typical AMS system, has been successfully applied to the ultra-sensitive determination of Sr and Cs in environment. For Sr in environmental samples, the -ray measurement by the milking of the daughter nuclide Y is still the principal method, which takes 3-6 weeks. The new AMS method has a detection limit of 0.1 mBq, which is comparable to that of -ray measurement, with a more straightforward chemical treatment than -measurement. Our achievement demonstrates that AMS can be a practical new method for determining Sr in the environment.

Variation of half-life and internal-conversion electron energy spectrum between U oxide and fluoride

Shigekawa, Yudai*; Kasamatsu, Yoshitaka*; Yasuda, Yuki*; Kaneko, Masashi; Watanabe, Masayuki; Shinohara, Atsushi*

Physical Review C, 98(1), p.014306_1 - 014306_5, 2018/07

https://doi.org/10.1103/PhysRevC.98.014306

The nuclear half-life of U has been reported to vary depending on the chemical environment. In this study, both the half-life and the internal-conversion (IC) electron energy spectrum were measured for U with identical chemical environments for the first time. U oxide and fluoride samples were subjected to these measurements, and clear differences in the half-life and the energy spectrum between these samples were observed. The peaks in the energy spectra were identified with the relativistic density functional theory calculation, and the molecular orbital states of the U oxide and fluoride estimated from the energy spectra and the calculation qualitatively explained the difference in the half-lives between the samples.

Analysis of ambient-dose-rate trends in Fukushima; Ecological half-life, effect of snow covering

Saegusa, Jun; Yoda, Tomoyuki; Murakami, Mitsuhiro; Takeishi, Minoru

Kankyo Hoshano Josen Gakkai-Shi, 5(2), p.79 - 93, 2017/06

After the Fukushima Daiichi Nuclear Power Plant (NPP) accident in March 2011, environmental radiation monitoring works have been continuously conducted throughout the Fukushima prefecture of Japan. Five-year transitions of ambient dose rates at 15 locations 20-60 km away from the NPPs were precisely analyzed to investigate their chronological change. Measured dose rates were successfully fitted into a function consisting of a factor reflecting the physical decay of radiocesium and the other component such as the weathering effect. The ecological half-lives derived from the function ranged from 3 to 27 years (average 10 years). The radiation shielding effect by snow covering was also studied with the obtained functions. Due to the effect, dose rates were lowered by 15-50% by 20-cm-deep snow covering, and the ambient doses integrated over the five years were found to decrease by up to 7% compared to those without the snow covering that can be predicted from the fit function.

Prediction of ambient dose equivalent rates for 30 years after the Fukushima accident and its technological development

Kinase, Sakae

Nihon Genshiryoku Gakkai-Shi ATOMO, 58(6), p.362 - 366, 2016/06

https://doi.org/10.3327/jaesjb.58.6_362

no abstracts in English

Changes in ambient dose equivalent rates around roads at Kawamata town after the Fukushima accident

Kinase, Sakae; Sato, Satoshi; Sakamoto, Ryuichi*; Yamamoto, Hideaki; Saito, Kimiaki

Radiation Protection Dosimetry, 167(1-3), p.340 - 343, 2015/11

https://doi.org/10.1093/rpd/ncv275

Research and development activities for accelerator driven system at JAERI

Tsujimoto, Kazufumi; Sasa, Toshinobu; Nishihara, Kenji; Oigawa, Hiroyuki; Takano, Hideki*

Proceedings of International Conference on Physics of Fuel Cycles and Advanced Nuclear Systems; Global Developments (PHYSOR 2004) (CD-ROM), 8 Pages, 2004/04

The Japan Atomic Energy Research Institute (JAERI) is developing an Accelerator Driven System (ADS) for transmutation of nuclear waste such as minor actinide (MA) and long-lived fission product (LLFP). To study and evaluate the feasibility of ADS by physical and engineering viewpoints, the Transmutation Experimental Facility (TEF) is proposed under a framework of J-PARC (Japan Proton Accelerator Research Complex) project. The TEF consists of two facilities named as Transmutation Physics Experimental Facility (TEF-P) and ADS Target Test Facility (TEF-T). The TEF-P consists of a zero-power critical assembly which is operated with a low power proton beam to research the reactor physics and the controllability of ADS. The TEF-T is a facility for material irradiation and partial mockup of beam window which can accept a maximum 600MeV-200kW proton beam into the Pb-Bi eutectic target. The purposes, experimental items and the specifications of the facilities are described.

Half-life of Pu and -decay energy of Np

Nishio, Katsuhisa; Ikezoe, Hiroshi; Mitsuoka, Shinichi; Sato, Kenichiro; Lin, C. J.

Physical Review C, 68(6), p.064305_1 - 064305_6, 2003/12

https://doi.org/10.1103/PhysRevC.68.064305

We observed two -decay chains starting from Pu in the reaction of S+Pt, and the half-life was measured to be 1.1 s for the first time. This contradicts the literature value of 4 ms as an upper limit, although the -decay energy agrees with each other. The present half-life follows the Geiger-Nuttall curve for even-even Pu isotopes, showing the dominant -decay branch. In this reaction, six decays of Np were firstly observed. The average -particle energy was 709761 keV. The evaporation residue cross sections of Pu, Np and U are reproduced by a statistical model calculation.

Systematics of cluster decay modes

Poenaru, D. N.; Nagame, Yuichiro; Gherghescu, R. A.*; Greiner, W.*

Physical Review C, 65(5), p.054308_1 - 054308_6, 2002/05

https://doi.org/10.1103/PhysRevC.65.054308

no abstracts in English

None

; *; *

JNC TN8200 2001-001, 42 Pages, 2001/01

JNC-TN8200-2001-001.pdf:3.16MB

None

Influence of naturally-occurring heterogeneous complex-forming materials on the migration behavior of actinides in the geosphere (III)

Tochiyama, Osamu*

JNC TJ8400 2000-044, 53 Pages, 2000/02

JNC-TJ8400-2000-044.pdf:1.41MB

To estimate the polyelectrolyte effect and the effect of the heterogeneous composition of humic acids, the complex formation constants of Eu(III) and Ca(II) with Aldrich humic acid and polyacrylic acid were obtained, for Eu(10 to 10 M) by solvent extraction with TTA and TBP in xylene, for Ca (10M) with TTA and TOPO in cyclohexane and for Ca(10M) by using ion-selective electrode. By defining the apparent formation as = [MR]/([M][R]), where [R] denotes the concentration of dissociated functional group, [M] and [MR] denote the concentration of free and bound metal ion and pcH is defined as-log[H], the values of log have been obtained at pcH 4.8 - 5.5 in 0.1 - 1.0M NaClO and NaCl. Log of Eu-humate varied from 5.0 to 9.3 and that of Ca-humate from 2.0 to 3.4..For both humate and polyacrylate, log increased with pcH or with the degree of dissociation. The increase in the ionic strength O.1 to 1.0 M decreased the log, the decrease in log of Eu(III)-humate is 1.6, that of Eu(III), polyacrylate 0.7, that of Ca(II)-humate 1.9 and that of Ca(II)-polyacrylate 1.2. While the increase in the metal ion produced no effect on log of polyacrylate, log of humate decreased. Depending on the concentration of Eu(III), the coexistence of Ca(II) reduced log of humate by 0 to 0.8. The dependence of log of humate on the metal ion concentration suggests the coexistence of strong and weak binding sites in the hmnic acid.