Liquid decontamination using acidic electrolyzed water for various uranium-contaminated steel surfaces in dismantled centrifuge

Sakasegawa, Hideo; Nomura, Mitsuo; Sawayama, Kengo; Nakayama, Takuya; Yaita, Yumi*; Yonekawa, Hitoshi*; Kobayashi, Noboru*; Arima, Tatsumi*; Hiyama, Toshiaki*; Murata, Eiichi*

Progress in Nuclear Energy, 153, p.104396_1 - 104396_9, 2022/11

https://doi.org/10.1016/j.pnucene.2022.104396

When dismantling centrifuges in uranium-enrichment facilities, decontamination techniques must be developed to remove uranium-contaminated surfaces of dismantled parts selectively. Dismantled uranium-contaminated parts can be disposed of as nonradioactive wastes or recycled after decontamination appropriate for clearance. previously, we developed a liquid decontamination technique using acidic electrolyzed water to remove uranium-contaminated surfaces. However, further developments are still needed for its actual application. Dismantled parts have various uranium-contaminated surface features due to varied operational conditions, inhomogeneous decontamination using iodine heptafluoride gas, and changes in long-term storage conditions after dismantling. Here, we performed liquid decontamination on specimens with varying uranium-contaminated surfaces cut from a centrifuge made of low-carbon steel. From the results, the liquid decontamination can effectively remove the uranium-contaminated surfaces, and radioactive concentrations fell below the target value within twenty minutes. Although the required time should also depend on dismantled parts' sizes and shapes in their actual application, we demonstrated that it could be an effective decontamination technique for uranium-contaminated steels of dismantled centrifuges.

Research and development on waste management for the Fukushima Daiichi NPS by JAEA

Koma, Yoshikazu; Ashida, Takashi; Meguro, Yoshihiro; Miyamoto, Yasuaki; Sasaki, Toshiki; Yamagishi, Isao; Kameo, Yutaka; Terada, Atsuhiko; Hiyama, Toshiaki; Koyama, Tomozo; et al.

Proceedings of International Nuclear Fuel Cycle Conference; Nuclear Energy at a Crossroads (GLOBAL 2013) (CD-ROM), p.736 - 743, 2013/09

Fukushima Daiichi Nuclear Power Station (F1NPS), TEPCO, was severely damaged with the hydrogen explosions caused by losing their cooling functions due to the earthquake and the tsunami occurred on March 11, 2011. Radioactive wastes generated from the current FINPS and future their decommission and demolition are greater huge amount than those from general reactors and nuclear fuel facilities. Toward accomplishing safe and reasonable management of the wastes, great effort of R&Ds has been strongly required and performed in bringing together the knowledge and experience of all of Japan. This report outlines the current status of the R&Ds performed in JAEA.

Status and plan of ageing management technical evaluation on nuclear power stations

Suzuki, Masahide; Nishiyama, Toshiaki*

Hozengaku, 9(4), p.2 - 8, 2011/01

http://ci.nii.ac.jp/naid/40018274415

no abstracts in English

Precise and accurate determination of plutonium by controlled-potential coulometry and its uncertainty evaluation

Yamamoto, Masahiko; Ishibashi, Atsushi; Nagayama, Tetsuya; Surugaya, Naoki; Kurosawa, Akira; Hiyama, Toshiaki

JAEA-Technology 2010-040, 28 Pages, 2010/12

JAEA-Technology-2010-040.pdf:0.97MB

Precise analysis of plutonium is necessary for material control and safeguards in nuclear facility. Thus, controlled-potential coulometry, which yields absolute results and high precision, was applied for the determination of plutonium. The coulometry system and sample pretreatment procedures were optimized following ISO12183:2005. Plutonium sample prepared from NBL CRM-126 Pu metal was measured and agreed well with certified value. For spike preparation of isotope dilution mass spectrometry (IDMS), plutonium solution was prepared from MOX powder. Plutonium content was 15.5995 mgPu/g. The uncertainty was calculated by ISO/BIPM Guide to the Expression of Uncertainties in Measurements. The relative expanded uncertainty was 0.023% with confidence interval of 95%. The results were in good agreement with those obtained by IDMS. Thus the proposed coulometry method was successfully applied for the determination of plutonium at the highest level of precision and accuracy.

Extraction chromatographic separation of trivalent minor actinides using Hex-BTP/SiO-P resin

Surugaya, Naoki; Sano, Yuichi; Yamamoto, Masahiko; Kurosawa, Akira; Hiyama, Toshiaki

Nuclear Energy and the Environment; ACS Symposium Series 1046, p.131 - 139, 2010/10

Simple determination of Sr in highly radioactive liquid waste by alkaline precipitation separation/liquid scintillation counting technique

Onuma, Takashi; Surugaya, Naoki; Hiyama, Toshiaki

Bunseki Kagaku, 58(7), p.633 - 638, 2009/07

https://doi.org/10.2116/bunsekikagaku.58.633

An analytical method with a liquid scintillation counting technique for the determination of Sr in the presence of other elements was developed by deriving a calculation formula to remove their influence. Generally the analysis of Sr is performed using the radioactive equilibrium of a generation process of Y with Sr separated from a sample. In this study, a new disintegration calculating formula that enable us remove influences by the coexistence nuclides to analyze Sr in highly radioactive liquid wastes of spent-fuel reprocessing plants was derived and the formula was validated by experimental approaches. It was found that Sr was analyzed without any influences when a sample contains nuclides that have a long half life and radioactive equilibrium is small enough compared with a generation of Y. The relative standard deviation of the analysis by the proposed method was equal to or less than 3%.

Automated gravimetric sample pretreatment using an industrial robot for high-precision determination of plutonium by isotope dilution mass spectrometry

Surugaya, Naoki; Hiyama, Toshiaki; Watahiki, Masaru

Analytical Sciences, 24(6), p.739 - 744, 2008/06

https://doi.org/10.2116/analsci.24.739

A robotized sample preparation method for the determination of Pu, which is recovered by extraction reprocessing of spent nuclear fuel, by isotope dilution mass spectrometry is described. The automated system has a six-axis industrial robot, whose motility is very fast, accurate and flexible, installed in a glove box. The automation of the weighing and diluting steps enables operator-unattended sample pretreatment for highly precise analyses of Pu in aqueous solutions. By the developed system, Pu concentration in HNO medium was successfully determined with a set of subsequent mass spectrometric measurements. The relative uncertainty in determining the concentration of Pu by isotope dilution mass spectrometry using this system for sample pretreatment was estimated to be less than 0.1 rel.% (=2), which is equal to that expected of a talented analyst. The operation time required was the same as that by a skilled operator.

Preparation, certification and validation of a stable solid spike of uranium and plutonium coated with a cellulose derivative for the measurement of uranium and plutonium content in dissolved nuclear fuel by isotope dilution mass spectrometry

Surugaya, Naoki; Hiyama, Toshiaki; Verbruggen, A.*; Wellum, R.*

Analytical Sciences, 24(2), p.247 - 252, 2008/02

https://doi.org/10.2116/analsci.24.247

A stable solid spike for the measurement of uranium and plutonium content in nitric acid solutions of spent nuclear fuel by isotope dilution mass spectrometry has been prepared at the European Commission Institute for Reference Materials and Measurements in Belgium. The spike contains about 50 mg of uranium with a 19.838% U enrichment and 2 mg of plutonium with a 97.766% Pu abundance in each individual ampoule. The dried materials were covered with a thin film of cellulose acetate butyrate as a protective organic stabilizer to resist shocks encountered during transportation and to eliminate flaking-off during long-term storage. It was found that the cellulose acetate butyrate has good characteristics, maintaining a thin film for a long time, but readily dissolving on heating with nitric acid solution. The solid spike containing cellulose acetate butyrate was certified as reference material IRMM-1027f with certified quantities: U and Pu amounts and uranium and plutonium amount ratios, and was validated by analyzing spent fuel dissolver solutions of the Tokai reprocessing plant in Japan.

Determination of plutonium in highly radioactive liquid waste by spectrophotometry using neodymium as an internal standard for safeguards analysis

Taguchi, Shigeo; Surugaya, Naoki; Sato, Soichi; Kurosawa, Akira; Watahiki, Masaru; Hiyama, Toshiaki

JAEA-Technology 2006-040, 76 Pages, 2006/07

JAEA-Technology-2006-040.pdf:5.23MB

A spectrophotometric determination using neodymium as an internal standard has been developed for safeguards verification analysis of plutonium in highly radioactive liquid waste which is produced by the reprocessing of spent nuclear fuel. The method offers reduced sample preparation and analysis time compared to isotope dilution mass spectrometry. It uses neodymium as an internal standard, which allows for determining an index for the authentication of the analytical operation and the instrument conditions. The sample was mixed with a known amount of neodymium as an internal standard. Subsequently, plutonium was quantitatively oxidized to Pu(IV) by the addition of Ce(IV). Plutonium concentration was calculated from a relation between Nd(III)/Pu(VI) molar extinction coefficient ratio and their absorbance ratio. The expanded uncertainty of the repeated analysis of plutonium (n=5) was found to be 15mgL (confidence interval 95%) for a highly radioactive liquid waste sample (173mgL). The determination limit was calculated to be 6mgL (ten fold's the standard deviation). This method was validated through comparison experiments with isotope dilution mass spectrometry. The analytical results of plutonium in highly radioactive liquid waste using this method were agree well with values obtained using isotope dilution mass spectrometry. The proposed method was successfully applied for the independent on-site safeguards analysis at the Tokai Reprocessing Plant.nt on-site safeguards analysis at the Tokai Reprocessing Plant.

Energy spectra of electrons induced by MeV atom clusters

Kudo, Hiroshi*; Iwasaki, Wataru*; Uchiyama, Rumi*; Tomita, Shigeo*; Shima, Kunihiro*; Sasa, Kimikazu*; Ishii, Satoshi*; Narumi, Kazumasa; Naramoto, Hiroshi; Saito, Yuichi; et al.

Japanese Journal of Applied Physics, Part 2, 45(22), p.L565 - L568, 2006/06

https://doi.org/10.1143/JJAP.45.L565

The first observation of the energy distribution of electrons emitted from solids bombarded by MeV atom clusters is reported. In the backward direction, using graphite and Si bombarded by C and Al (n 8), an appreciable suppression of electron emission has been observed at electron energies lower than 10 eV. Electron yield per atom decreases with increasing n, and becomes less than 50% at n 3, relative to the case of n = 1. The experimental results cannot be explained in terms of projectile stopping cross sections nor by the clearing-the-way effect. It is probable that the suppressed electron emission is a result of the suppression of the transport or surface transmission of the produced low-energy electrons, rather than of the suppression of ionization.