Analysis of particles containing alpha-emitters in stagnant water at torus room of Fukushima Dai-ichi Nuclear Power Station's Unit 2 reactor

Yomogida, Takumi; Ouchi, Kazuki; Oka, Toshitaka; Kitatsuji, Yoshihiro; Koma, Yoshikazu; Konno, Katsuhiro*

Scientific Reports (Internet), 12(1), p.7191_1 - 7191_10, 2022/05

https://doi.org/10.1038/s41598-022-11334-1

Particles containing alpha () nuclides were identified from sediment in stagnant water at the torus room of the Fukushima Dai-ichi Nuclear Power Station (FDiNPS)'s Unit 2 reactor. Several uranium-bearing particles were identified by SEM observation. These particles contained Zr and other elements which constituted fuel cladding and structural materials. The U/U isotope ratio in the solid fractions that included U particles was consistent with the nuclear fuel in the Unit 2 reactor, which indicated that the U particles had been derived from nuclear fuel. The particles with alpha-emitters detected by alpha track analysis were several tens to several hundred m in size. The EDX spectra showed that these particles mainly comprised iron, which indicated Pu, Am, and Cm were adsorbed on the Fe-baring particles. This study clarifies that the major morphologies of U and other -nuclides were differed in the sediment of stagnant water in the torus room of FDiNPS's Unit 2 reactor.

Measures of closing report of outside waste storage pits; Separate Volume Part I; Photographs sbout improvement step of outside waste storage pits

Yoshida, Michihiro; Suzuki, Satoshi*; Sukegawa, Yasuhiro*; Miyo, Hiroaki

JNC TN8440 2000-021, 180 Pages, 2000/10

JNC-TN8440-2000-021.pdf:42.37MB

At outside waste storage pits, containers for storage of wastes corroded and were flooded, and it was confirmed on August 26, 1997. Confirmation of contamination of the pits outskirts, installation of sheets to prevent rainwater from flowing into the pits, drawing stay water were executed, promptly. Design and authorization works of the work house and waste treatment devices to take out wastes of the pits were executed too. After construction of the work house, taking out wastes of the pits started, and finished on April 10, 1998. Investigations of the inflow point of rainwater and leak of stay water were executed next. The results were reported to Science and Thechnology Agency (STA), adjoining authorities on December 21, 1998. After decontamination of the pits inner walls to background level of the radioactivity which included general concrete, control area was removed, and the pits were closed by concrete. Measures of closing of the pits were prepared from the middle of August, 1999, and dismantlement of unnecessaly instruments started. Decontamination of the pits started fiom the beginning of September, 1999. The above works finished on June 30, 2000. After decontamination of the pits, STA, adjoining authorities confirmed the circumstances. Work pouring concrete into the pits was executed three times (three levels), and finished on August 31, 2000. In addition to above, the amount of concrete poured into the pits was about 1,200 m. This report compiled the photographs of the works from confirmation of stay water at August, 1997 by finish of measures of closing of the pits at September, 2000.

Consideration for long-term storage of a spent zeolite adsorption vessel,7; Experiment flushing salt component on actual flow rate in a spent zeolite adsorption vessel, SARRY

Sato, Hiroyuki; Terada, Atsuhiko; Kato, Chiaki; Yamagishi, Isao; Ikeda, Akira*; Okita, Takeshi*

no journal, , 

As a part of consideration for long-term storage of a spent zeolite adsorption vessel in the Fukushima No.1 nuclear power plant, experiment flashing salt component (5,000 ppm in chloride ion) in vessel was carried out using actual sized model of SARRY adsorption vessel.

Migration behavior of radioactive nuclides to structural materials in accumulated water at Fukushima Daiichi Nuclear Power Station, 1; Migration behavior of Cs, Sr, Ni

Aihara, Haruka; Shibata, Atsuhiro; Nomura, Kazunori

no journal, , 

no abstracts in English

Analysis of alpha radionuclide in the contaminated water at the torus room of unit #2 reactor of Fukushima Daiichi NPS, 2; Analysis of alpha-emitting nuclides of solid components by ICP-MS

Ouchi, Kazuki; Yomogida, Takumi; Oka, Toshitaka; Kitatsuji, Yoshihiro; Koma, Yoshikazu; Konno, Katsuhiro*

no journal, , 

In order to grasp the existence state of -nuclides contained as particulate solids in the contaminated water, -nuclide concentrations in the solids and the filtrate which classified according to particle size using filters with pore sizes of 10, 1, 0.1 and 0.02 m were quantitatively analyzed by ICP-MS. Reactor-derived U was detected in the particulate solids in the contaminated water, and most of them settled deeply as coarse particles of 10 m. U existing in the water as fine particles and ions was also confirmed.

Analysis of alpha radionuclide in the contaminated water at the torus room of unit #2 reactor of Fukushima Daiichi NPS, 1; Outline of the state analysis of alpha radionuclides containing in the solid component

Kitatsuji, Yoshihiro; Ouchi, Kazuki; Yomogida, Takumi; Oka, Toshitaka; Nitta, Ayako; Hinai, Hiroshi; Koma, Yoshikazu; Konno, Katsuhiro*

no journal, , 

In order to clarify the chemical species of alpha nuclides in the contaminated water of the Fukushima Daiichi Nuclear Power Station, sludge was classified by particle size. The concentration of alpha radioisotope was measured and the particles were investigated. Most alpha particles were larger than 10 micrometers and settled at the bottom of the torus chamber.

Fe analysis of radio-particle in the contaminated water at Fukushima Daiichi NPS with Mssbauer spectroscopy

Ouchi, Kazuki; Nakada, Masami; Yomogida, Takumi; Oka, Toshitaka; Koma, Yoshikazu; Kitatsuji, Yoshihiro

no journal, , 

In order to understand the existence state of radio-particle contained in the retained water at Fukushima Daiichi NPS, the chemical species of Fe which is the main constituent element of radio-particle were analyzed with Mssbauer spectroscopy. Most Fe was found to be -form Fe(III) oxyhydroxide. Since this species is formed in the coexistence of chloride ion, it is a reasonable in the environment containing chloride ion at the same level as seawater.

-emitting nuclides analysis of the stagnant water including sediments in Fukushima Daiichi NPS, 2; Detection of fine particle containing -emitters by SEM-EDX and alpha Track

Yomogida, Takumi; Ouchi, Kazuki; Morii, Shiori; Oka, Toshitaka; Kitatsuji, Yoshihiro; Koma, Yoshikazu; Konno, Katsuhiro*

no journal, , 

To investigate the morphology of -nuclides in solid fraction of the stagnant water in the Fukushima Dai-ichi nuclear Power Station's Unit 3 reactor, we tried to detect particles containing -nuclides by scanning electron microscopy-X-ray detection (SEM-EDX) and the alpha track method. As a result of SEM-EDX observation, several sub-m to 10 m size particles containing U were identified. The particles containing alpha emitters were identified by alpha-track method. These particles with few hundred m in diameter were mainly composed of iron.

-emitting nuclides analysis of the stagnant water including sediments in Fukushima Daiichi NPS, 3; Chemical state analysis of -emitting nuclide particles obtained from unit #3 stagnant water sludge

Usui, Akane; Yamaguchi, Yukako; Sekio, Yoshihiro; Maeda, Koji; Koma, Yoshikazu; Konno, Katsuhiro*

no journal, , 

no abstracts in English

-emitting nuclides analysis of the stagnant water including sediments in Fukushima Daiichi NPS, 11; Dissolution of fine particles and -emitting nuclides by immersing in an acid solution

Yomogida, Takumi; Morii, Shiori; Oka, Toshitaka; Koma, Yoshikazu; Kitatsuji, Yoshihiro

no journal, , 

Most of -emitting nuclides in sediment of stagnant water exist as iron particles and U particles. An attempt was made to selectively dissolve iron particles by immersion in an acid solution and investigate the abundance of -nuclides in these particles. Most of the uranium in the sediment is present on iron particles like other alpha nuclides, and the proportion of uranium present as U particles is estimated to be 5% or less.