Investigation of effects of nano interfacial phenomena on dissolution aggregation of alpha nanoparticles by using micro nano technologies (Contract research); FY2022 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Tokyo Institute of Technology*

JAEA-Review 2024-022, 59 Pages, 2024/09

JAEA-Review-2024-022.pdf:4.27MB

The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") in FY2022. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2022, this report summarizes the research results of the "Investigation of effects of nano interfacial phenomena on dissolution aggregation of alpha nanoparticles by using micro nano technologies" conducted in FY2022. To ensure the safety of retrieval and storage management of nuclear fuel debris generated by the Fukushima Daiichi Nuclear Power Station accident, understanding of dissolution-denaturation behavior of the fuel debris alpha particles is one of the most crucial issues. This research aims to create novel microfluidic real-time measurement device for elucidating dissolution, aggregation, and denaturation processes of metal oxide nanoparticles under various solution environments, and clarify their nano-size and interfacial effects.

UO dissolution in bicarbonate solution with HO; The Effect of temperature

McGrady, J.; Kumagai, Yuta; Kitatsuji, Yoshihiro; Kirishima, Akira*; Akiyama, Daisuke*; Watanabe, Masayuki

RSC Advances (Internet), 13(40), p.28021 - 28029, 2023/09

https://doi.org/10.1039/D2RA08131H

Upon nuclear waste canister failure and contact of spent nuclear fuel with groundwater, the UO matrix of spent fuel will interact with oxidants in the groundwater generated by water radiolysis. Bicarbonate (HCO) is often found in groundwater, and the HO induced oxidative dissolution of UO in bicarbonate solution has previously been studied under various conditions. Temperatures in the repository at the time of canister failure will differ depending on the location, yet the effect of temperature on oxidative dissolution is unknown. To investigate, the decomposition rate of HO at the UO surface and dissolution of U in bicarbonate solution (0.1, 1, 10 and 50 mM) was analysed at various temperatures (10, 25, 45 and 60 C). At [HCO] 1 mM, the apparent equilibrium concentration of U decreased with increasing temperature. This was attributed to the formation of U-bicarbonate species at the surface and a change in the mechanism of HO decomposition from oxidative to catalytic. At 0.1 mM, no obvious correlation between temperature and U dissolution was observed, and thermodynamic calculations indicated this was due to a change in the surface species. A pathway to explain the observed dissolution behaviour of UO in bicarbonate solution as a function of temperature was proposed.

Potential bacterial alteration of nuclear fuel debris; A Preliminary study using simulants in powder and pellet forms

Liu, J.; Dotsuta, Yuma; Sumita, Takehiro; Kitagaki, Toru; Onuki, Toshihiko; Kozai, Naofumi

Journal of Radioanalytical and Nuclear Chemistry, 331(6), p.2785 - 2794, 2022/06

https://doi.org/10.1007/s10967-022-08324-y

Remnant nuclear fuel debris in the damaged nuclear reactors at the Fukushima Daiichi Nuclear Power Plant (FDNPP) has contacted the groundwater containing microorganisms for over ten years. Herein, we report the possibility of bacterial alteration of fuel debris. We investigated the physical and chemical changes of fuel debris simulants (FDS) in the powder and pellet forms via exposure to two ubiquitous bacteria, Pseudomonas fluorescens and Bacillus subtilis. In the experiments using FDS composed of the powders of Fe(0), solid solution of CeO and ZrO, and SiO, Ce, Zr, and Si were hardly dissolved, while Fe was dissolved, a fraction of the dissolved Fe was present in the liquid phase as Fe(II) and Fe(III), and the rest was precipitated as the nano-sized particles of iron (hydr)oxides. In the experiment using P. fluorescens and FDS pellet pieces prepared by melting the Fe(0) particles and solid solution of CeO and ZrO, the bacteria selectively gathered on the Fe(0) particle surface and made corrosion pits. These results suggest that bacteria in groundwater corrode the iron in fuel debris at FDNPP, change fuel debris into porous one, releasing the nano-sized iron (hydr)oxide particles into the water.

The Kinetics and mechanism of HO decomposition at the UO surface in bicarbonate solution

McGrady, J.; Kumagai, Yuta; Watanabe, Masayuki; Kirishima, Akira*; Akiyama, Daisuke*; Kitamura, Akira; Kimuro, Shingo

RSC Advances (Internet), 11(46), p.28940 - 28948, 2021/08

https://doi.org/10.1039/D1RA05580A

Thorium oxide dissolution in HNO-HF mixture; Kinetics and mechanism

Simonnet, M.; Barr, N.*; Drot, R.*; Le Naour, C.*; Sladkov, V.*; Delpech, S.*

Radiochimica Acta, 107(4), p.289 - 297, 2019/04

https://doi.org/10.1515/ract-2018-3052

Effects of OH activity and temperature on the dissolution rate of compacted montmorillonite under highly alkaline conditions

Sawaguchi, Takuma; Tsukada, Manabu; Yamaguchi, Tetsuji; Mukai, Masayuki

Clay Minerals, 51(2), p.267 - 278, 2016/05

https://doi.org/10.1180/claymin.2016.051.2.12

The dependences of the dissolution rate of compacted montmorillonite on activity of OH (a-) and temperature (T) were investigated. The dissolution rate of montmorillonite () in compacted pure montmorillonite, which was formulized as = 10 (a-) e, was higher than that in the compacted sand-bentonite mixtures: = 3500 (a-) e. The difference can be explained by considering the decrease in a- in the mixtures accompanied by dissolution of accessory minerals such as quartz and chalcedony. The dissolution rate model developed for pure montmorillonite is expected to be applied to bentonite mixtures if quantification of the decrease in a- is achieved somehow.

Effects of -radiation on a direct disposal system for spent nuclear fuel, 1 Review of research into the effects of -radiation on the spent nuclear fuel, canisters and outside canisters

Kitamura, Akira; Takase, Hiroyasu*

Journal of Nuclear Science and Technology, 53(1), p.1 - 18, 2016/01

https://doi.org/10.1080/00223131.2015.1018362

Not only geological disposal of vitrified waste generated by spent fuel (SF) reprocessing, but also the possibility of disposing of SF itself in deep geological strata (hereinafter "direct disposal of SF") may be considered in the Japanese geological disposal program. In the case of direct disposal of SF, the radioactivity of the waste is higher and the potential effects of the radiation are greater. Specific examples of the possible effects of radiation include: increased amounts of canister corrosion; generation of oxidizing chemical species in conjunction with radiation degradation of groundwater and accompanying oxidation of reducing groundwater; and increase in the dissolution rate and the solubility of SF. Focusing especially on the effects of -radiation in safety assessment, this study has reviewed research into the effects of -radiation on the spent nuclear fuel, canisters and outside canisters.

Rapid dissolution techniques with microwave heating devices for solidified products made from non-metallic wastes by plasma melting

Haraga, Tomoko; Kameo, Yutaka; Nakashima, Mikio

Bunseki Kagaku, 55(1), p.51 - 54, 2006/01

https://doi.org/10.2116/bunsekikagaku.55.51

A relatively large quantity of sample solutions have to be prepared for radiochemical analysis of solidified products yielded by plasma melting treatment of non-metallic radioactive wastes. In order to dissolve the solidified products sample rapidly, dissolution method with microwave heating devices was applied. In a conventional method only by external heating with various mixtures of acids (HNO, HF, HClO and HSO), a 0.1 g amount of the sample was dissolved with difficulty. However, applying the microwave assisted dissolution method, a 1 g amount of the sample was completely dissolved in a shorter time. Thereby the time for dissolution procedures was shortened less than a one-tenth. The present dissolution method was successfully applied to the blast furnace slag as a reference material to determine main elements with good precision.

Comparison of the corrosion behavior of austenitic and ferritic/martensitic steels exposed to static liquid Pb-Bi at 450 and 550 C

Kurata, Yuji; Futakawa, Masatoshi; Saito, Shigeru

Journal of Nuclear Materials, 343(1-3), p.333 - 340, 2005/08

https://doi.org/10.1016/j.jnucmat.2004.07.064

In order to study effects of temperature and alloying elements on corrosion behavior in liquid Pb-Bi which will be used for an accelerator driven system (ADS), corrosion tests of various steels were conducted under static liquid Pb-Bi condition. The tests were performed in oxygen-saturated liquid Pb-Bi at 450C and 550C for 3000h. Oxide films were formed during corrosion at 450C and 550C. Corrosion depth of steels decreased at 450C with increasing Cr content of steels. Austenitic stainless steels containing Ni didn't exhibit appreciable dissolution of Ni and Cr at 450C. The thick ferrite layer produced by dissolution of Ni and Cr was found in JPCA and type 316ss at 550C. For this reason the corrosion depth of austenitic stainless steels, JPCA and type 316ss became large. A Si-added austenitic stainless steel showed good corrosion resistance at 550C because a protective oxide film formed on the steel prevented dissolution of Ni and Cr into liquid Pb-Bi.

Electrochemical behaviors of PuN and (U, Pu)N in LiCl-KCl eutectic melts

Shirai, Osamu; Kato, Tetsuya*; Iwai, Takashi; Arai, Yasuo; Yamashita, Toshiyuki

Journal of Physics and Chemistry of Solids, 66(2-4), p.456 - 460, 2005/02

https://doi.org/10.1016/j.jpcs.2004.06.040

Electrochemical behaviors of PuN and (U, Pu)N in the LiCl-KCl eutectic melt containing UCl and PuCl at 773 K were investigated by cyclic voltammetry. The electrochemical dissolution of PuN and (U, Pu)N began nearly at -1.0 V vs. the Ag/AgCl reference electrode. The rest potentials of PuN and (U, Pu)N were observed at about 0.15 V more negative potential than that of UN since the equilibrium potential of UN is about 0.15 V more positive than that of PuN. In the cyclic voltammogram measured by using (U, Pu)N as the working electrode, a steep rise of the positive current was observed at more positive potential than -0.4 V in analogy with the cyclic voltammogram measured by using UN as the working electrode. In addition, there were two anodic current waves in the voltammogram with (U, Pu)N, though the wave form was not clear. This indicates that UN and PuN would be dissolved independently irrespective of formation of the solid solution, (U, Pu)N.