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Okumura T, Yamaguchi N, Suga H, Takahashi Y, Segawa H, Kogure T. Reactor environment during the Fukushima nuclear accident inferred from radiocaesium-bearing microparticles. Sci Rep 2020; 10:1352. [PMID: 31992831 PMCID: PMC6987194 DOI: 10.1038/s41598-020-58464-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Accepted: 01/15/2020] [Indexed: 11/25/2022] Open
Abstract
Radiocaesium-bearing microparticles (CsMPs), which are substantially silicate glass, were formed inside the damaged reactor and released to the environment by the Fukushima Dai-ichi Nuclear Power Plant accident in March 2011. The present study reports several valuable findings regarding their composition and structure using advanced microanalytical techniques. X-ray absorption near-edge structure of Fe L3-absorption indicated that the oxidation state of the iron dissolved in the glass matrix of the CsMPs was originally nearly divalent, suggesting that the atmosphere in which the CsMPs were formed during the accident was considerably reductive. Another major finding is that sodium, which has not been recognised as a constituent element of CsMPs thus far, is among the major elements in the glass matrix. The atomic percent of Na is higher than that of other alkali elements such as K and Cs. Furthermore, halite (NaCl) was found as an inclusion inside a CsMP. The existence of Na in CsMPs infers that seawater injected for cooling might reach the inside of the reactor before or during the formation of the CsMPs. These results are valuable to infer the environment inside the reactor during the accident and the debris materials to be removed during the decommissioning processes.
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Affiliation(s)
- Taiga Okumura
- The University of Tokyo, Department of Earth and Planetary Science, Graduate School of Science, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
| | - Noriko Yamaguchi
- Institute for Agro-Environmental Sciences, NARO, 3-1-3 Kannondai, Tsukuba, Ibaraki, 305-0864, Japan
| | - Hiroki Suga
- The University of Tokyo, Department of Earth and Planetary Science, Graduate School of Science, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Yoshio Takahashi
- The University of Tokyo, Department of Earth and Planetary Science, Graduate School of Science, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Hiroyo Segawa
- National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki, 305-0044, Japan
| | - Toshihiro Kogure
- The University of Tokyo, Department of Earth and Planetary Science, Graduate School of Science, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
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Okumura T, Yamaguchi N, Dohi T, Iijima K, Kogure T. Inner structure and inclusions in radiocesium-bearing microparticles emitted in the Fukushima Daiichi Nuclear Power Plant accident. Microscopy (Oxf) 2019; 68:234-242. [PMID: 30721986 DOI: 10.1093/jmicro/dfz004] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Revised: 12/24/2018] [Accepted: 01/15/2019] [Indexed: 11/12/2022] Open
Abstract
Radiocesium-bearing microparticles (CsMPs), consisting substantially of silicate glass, were released to the environment during the Fukushima Daiichi Nuclear Power Plant accident in March 2011. Since the CsMPs were formed inside the damaged reactors during the accident, we investigate the inner structures of several CsMPs by transmission electron microscopy to understand the events within the reactors. Elemental mapping of the CsMPs shows a distinct radial distribution of Cs with a higher concentration near the surface of the CsMPs, implying that Cs was in a gaseous state in the reactor atmosphere and diffused into the glass matrix after formation of the glass particles. In some CsMPs, Zn and Fe also showed a similar radial distribution to Cs, suggesting that those elements may have diffused outward where Cs was abundant. In addition, submicron crystals were present as inclusions in several of the CsMPs and were identified as chromium spinels ((Fe2+,Zn)(Cr,Fe3+)2O4), acanthite (Ag2S), molybdenite (MoS2) and hessite (Ag2Te). The spinels contained ferrous iron (Fe2+), suggesting that the atmosphere inside the reactors was reductive to some extent. Also, boron was not detected in the glass matrix of the CsMPs despite using electron energy-loss spectroscopy, indicating that most of the control rods made of B4C might have created a eutectic alloy without vaporization. These detailed investigations of the inner structures in the CsMPs may offer information on the damaged reactors that are difficult to access because of the high radiation fields.
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Affiliation(s)
- Taiga Okumura
- Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan
| | - Noriko Yamaguchi
- Institute for Agro-Environmental Sciences, NARO, 3-1-3 Kannondai, Tsukuba, Japan
| | - Terumi Dohi
- Fukushima Environmental Safety Center, Sector of Fukushima Research and Development, Japan Atomic Energy Agency, 10-2 Fukasaku, Miharu-machi, Tamura-gun, Fukushima, Japan
| | - Kazuki Iijima
- Fukushima Environmental Safety Center, Sector of Fukushima Research and Development, Japan Atomic Energy Agency, 10-2 Fukasaku, Miharu-machi, Tamura-gun, Fukushima, Japan
| | - Toshihiro Kogure
- Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan
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Rai VN, Rajput P, Jha SN, Bhattacharyya D, Raja Shekhar BN, Deshpande UP, Shripathi T. Effect of gamma irradiation on X-ray absorption and photoelectron spectroscopy of Nd-doped phosphate glass. JOURNAL OF SYNCHROTRON RADIATION 2016; 23:1424-1432. [PMID: 27787248 DOI: 10.1107/s1600577516014399] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Accepted: 09/09/2016] [Indexed: 06/06/2023]
Abstract
X-ray absorption near-edge structure (XANES) and X-ray photoelectron spectroscopy (XPS) of Nd-doped phosphate glasses have been studied before and after gamma irradiation. The intensity and the location of the white line peak of the L3-edge XANES of Nd are found to be dependent on the ratio O/Nd in the glass matrix. Gamma irradiation changes the elemental concentration of atoms in the glass matrix, which affects the peak intensity of the white line due to changes in the covalence of the chemical bonds with Nd atoms in the glass (structural changes). Sharpening of the Nd 3d5/2 peak profile in XPS spectra indicates a deficiency of oxygen in the glasses after gamma irradiation, which is supported by energy-dispersive X-ray spectroscopy measurements. The ratio of non-bridging oxygen to total oxygen in the glass after gamma radiation has been found to be correlated to the concentration of defects in the glass samples, which are responsible for its radiation resistance as well as for its coloration.
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Affiliation(s)
- V N Rai
- Indus Synchrotron Utilization Division, Raja Ramanna Centre for Advanced Technology, Indore 452013, India
| | - Parasmani Rajput
- Atomic & Molecular Physics Division, Bhabha Atomic Research Center, Trombay, Mumbai-400085, India
| | - S N Jha
- Atomic & Molecular Physics Division, Bhabha Atomic Research Center, Trombay, Mumbai-400085, India
| | - D Bhattacharyya
- Atomic & Molecular Physics Division, Bhabha Atomic Research Center, Trombay, Mumbai-400085, India
| | - B N Raja Shekhar
- Atomic & Molecular Physics Division, Bhabha Atomic Research Center, Trombay, Mumbai-400085, India
| | - U P Deshpande
- UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452001, India
| | - T Shripathi
- UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452001, India
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Liu Z, Stevens-Kalceff MA, Riesen H. Effects of Postannealing on the Photoluminescence Properties of Coprecipitated Nanocrystalline BaFCl:Sm3+. J Phys Chem A 2013; 117:1930-4. [DOI: 10.1021/jp3118105] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Zhiqiang Liu
- School of Physical, Environmental and Mathematical Sciences, The University of New South Wales, UNSW Canberra (ADFA),
Canberra, ACT 2600, Australia
| | - Marion A. Stevens-Kalceff
- School of Physics and Electron
Microscope Unit, Mark Wainwright Analytical Centre, The University of New South Wales, Sydney, NSW 2052, Australia
| | - Hans Riesen
- School of Physical, Environmental and Mathematical Sciences, The University of New South Wales, UNSW Canberra (ADFA),
Canberra, ACT 2600, Australia
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