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Ishijima, Yasuhiro; Ueno, Fumiyoshi; Abe, Hitoshi
Materials Transactions, 63(4), p.538 - 544, 2022/04
Times Cited Count：0 Percentile：0(Materials Science, Multidisciplinary)The time dependence of the corrosion behavior of tantalum (Ta), which is used in nuclear fuel reprocessing equipment, in sodium hydroxide (NaOH) solutions was investigated by immersion tests, and the mechanism of the time dependence was examined via surface observations and electrochemical measurements. The immersion tests were conducted at room temperature with NaOH concentrations ranging from 1 to 7 mol/L for immersion periods of 24 to 168 h. The corrosion rate increased with the NaOH concentration but peaked with the immersion period and then decreased. The time to peak of the corrosion rate was shorter with higher NaOH concentration. The X-ray diffraction (XRD) patterns and Raman spectra of the surfaces of the specimens immersed in the 7 mol/L NaOH solution for more than 48 h showed Na
Ta
O
formation. The polarization resistance decreased with immersion time for all NaOH concentrations up to about 24 h after immersion. Thereafter, the polarization resistance increased with immersion time in 7 mol/L NaOH solution and remained almost constant in the other NaOH concentrations. Findings suggested that the change in the corrosion rate was affected by the film formation during immersion, since the time dependence of the polarization resistance and the sum of film resistance and charge transfer resistance had the same tendencies. The precipitation film was mainly NaTaO formed by the dissolution of the passivity film on Ta.
Ishijima, Yasuhiro; Ueno, Fumiyoshi; Abe, Hitoshi
Zairyo To Kankyo, 70(6), p.192 - 198, 2021/06
The time dependence of corrosion behavior on tantalum used in nuclear fuel reprocessing equipment in sodium hydroxide solution was investigated by immersion corrosion tests, and the mechanism of aging change was discussed from surface observations and electrochemical measurements. The immersion tests were carried out at room temperature with NaOH concentrations ranging from 1 to 7 mol/L and immersion times ranging from 24 to 168 hr, respectively. The corrosion rate increased with NaOH concentration, but peaked with immersion time and then decreased. The time to peak of corrosion rate was shorter with higher NaOH concentration. The SEM observations and Raman analysis at the surface of the specimens that were cleaned and weighed after the immersion test did not show any film formation. On the other hand, the polarization resistance showed a constant value or an increase after a decrease immediately after immersion. It is suggested that the change in corrosion rate is affected by the formation of film by immersion, since the value of polarization resistance is almost the same as the sum of film resistance and charge transfer resistance. The film was considered to be mainly NaTaO formed by the dissolution of Ta.
Yamamoto, Masahiko; Do, V. K.; Taguchi, Shigeo; Kuno, Takehiko; Takamura, Yuzuru*
Journal of Radioanalytical and Nuclear Chemistry, 327(1), p.433 - 444, 2021/01
Times Cited Count：0 Percentile：0.01(Chemistry, Analytical)A simple, practical, and reliable analytical method for determination of Na, K, Ca, Sr, and Ba by liquid electrode plasma optical emission spectrometry is developed. Appropriate emission lines for quantification, interferences from co-existing elements, and effect of measurement conditions with cell damage have been investigated. The spike and recovery tests using actual sample have been performed for method validation, and negligible sample matrix effect has been observed. Consequently, the method is successfully applied to several radioactive wastes. The obtained data have been agreed well with data from computer calculation and inductively coupled plasma optical emission spectrometry within 10% difference.
Sano, Yuichi; Ambai, Hiromu; Takahatake, Yoko
Aichi Shinkurotoron Hikari Senta 2017-Nendo Kokyoto Riyo Seika Hokokusho (Internet), 1 Pages, 2018/00
In order to elucidate the mechanism of corrosion in the reprocessing process and propose a method for suppressing corrosion, the effect of coexisting substances on the chemical form of Ru in nitric acid solution containing seawater components was evaluated. The result of XAFS measurement for Ru showed the structural change around a Ru atom due to the interaction with chloride ion, which will suppress the corrosion promoting action of Ru in nitric acid solution.
Tachimori, Shoichi; Suzuki, Shinichi; Sasaki, Yuji
Nihon Genshiryoku Gakkai-Shi, 43(12), p.1235 - 1241, 2001/12
Times Cited Count：29 Percentile：87.17(Nuclear Science & Technology)no abstracts in English
Oda, Yoshihiro; Funasaka, Hideyuki; Wang, X.*; Obara, Kenji*; Wada, Hitoshi*
JNC TY8400 2000-002, 47 Pages, 2000/03
JNC-TY8400-2000-002.pdf:2.53MB
no abstracts in English
; ; Nomura, Kazunori; ; Washiya, Tadahiro*; Koizumi, Masumichi
PNC TN1600 93-004, 119 Pages, 1993/11
None
Yamato, Aiji; Sasaki, Noriaki; ; Miyahara, Kaname;
PNC TN1100 94-003, 355 Pages, 1993/11
Radioactive waste management research programs inevitably include laboratory solubili and sorption studies to provide data for radionuclide transport model. Estimation of lubility strongly depends on the reliability of thermodynamic data (e.g., carbonato-colexes) and may also depend on kinetic data on alteration of solubility limiting solid ases. Existing sorption data may include some kind of retardation mechanisms to be excded (e.g., precipitation). To develop these fundamental data, we must also consider a rge number of radioactive elements, a large number of factors (e.g., pH, Eh, complexinligands) in the repository environmentg, and numerous solid and aqueous species of radnuclides along with the many absorbents. Therefore, a systematic approach and researchlan are needed for obtaining and evaluation thermodynamic and sorption constants. The cus of this session was on thermodynamic data for aqueous species and solid phases imptant to the geological disposal system, on kinetic data
Yamato, Aiji; Sasaki, Noriaki; ; Miyahara, Kaname
PNC TN1100 94-002, 85 Pages, 1993/11
Nuclear energy is the second largest source of electric power in the United States. Tdate, nuclear power plants produced over twenty percent of the nation's electricity. Aof August 1991, there were 112 nuclear power reactors in the United States, and two mo were being built. By the year 2000, approximately 40,000 metric tons of nuclear wasteill be in temporary storage at reactor sites throughout the coutry. That amount is twi the amount that currently exists. In order to handle such waste, as well as the addedolume to be produced after the year 2000, the U. S. Department of Energt (DOE) is in t process of developing the waste management system that was authorized by the U. S Coness in 1987. The authorized system is illustrated in Figure 1. To summarize, spent nucar fuel from commercial power reactors will be accepted by the DOE at the reactor siteand transported to a monitored retrievable storage (MRS) facility for temporary storagand preparation for permanent disposal in a gelogic rep
Odo, Toshihiro;
PNC TN9420 92-005, 83 Pages, 1992/04
This report introduces the nuclear instrumentation system and major R&D (research and development) activities using radiation measurement techniques in Experimental Fast Reactor "JOYO". In the introduction of the nuclear instrumentation system, following items are described; (1)system function (2)roles as a reactor plant equipment (3)specifications and charactelistics of neutron detectors, (4)construction and layout of the system. For reactor dosimetry at various irradiation tests and surveillance tests, multi-foil method employed in "JOYO", neutron fluence evaluation using activation foils and HAFM (Helium Accumulation Fluence Monitor) under development are described briefly. The failed fuel detection system and some experimental equipments using radiation measurement techniques are also introduced here with main results obtained by a series of fuel failure simulation experiments. In addition, following R&Ds are picked up as some examples based on radiation measurement technology; (1)burn-up measurement of spent fuel subassembly (2)measurement and evaluation of radiation source distributions (radioactive corrosion products)
*; Shirahashi, Koichi; Kubota, Masumitsu
JAERI-M 89-168, 25 Pages, 1989/11
no abstracts in English
Umezawa, Hirokazu
Nihon Genshiryoku Gakkai-Shi, 16(7), p.361 - 364, 1974/07
no abstracts in English
Genshiryoku Kogyo, 13(4), p.23 - 28, 1967/00
no abstracts in English
Kumagai, Yuta
no journal, ,
Uranium oxides in contact with water dissolves when exposed to ionizing radiation. The dissolution is induced by oxidation due to products of the water radiolysis such as hydrogen peroxide. This oxidative dissolution process has particular importance in deep geological disposal of spent nuclear fuels, because it dominates the release of radionuclides from the UO
fuel matrix to the underground environment. Similarly, the uranium oxidation is expected to have a key role in long-term degradation of fuel debris generated in severe accidents in nuclear power plants. Here, our recent studies of radiation-induced dissolution of UO and also (U, Zr)O, which is one of typical solid phase found in the fuel debris will be reported.
