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JAEA Reports

Geochemistry research equipment for TRU waste elements

Akai, Masanobu; Ito, Nobuyuki*; Yamaguchi, Tetsuji; Tanaka, Tadao; Iida, Yoshihisa; Nakayama, Shinichi; Inagaki, Shingo*

JAERI-Tech 2004-058, 47 Pages, 2004/09

JAERI-Tech-2004-058.pdf:7.27MB

Geochemistry Research Equipment for TRU Waste Elements has been installed in Back-end Cycle Key Elements Research Facility (BECKY) of Nuclear Fuel Cycle Safety Engineering Research Facility (NUCEF). This equipment is designed to study geochemical behavior of TRU elements and other radionuclides contained in TRU waste (TRU waste elements) and to acquire data for safety assessments of radioactive wastes disposal. The equipment consists of anaerobic glove box systems, aerobic glove box systems equipped with built-in barrier performance testing apparatus, and analytical instruments. This report describes principles, structure, performance and safety designs of each component of the equipment, and results of research performed in the equipment.

JAEA Reports

Experimental investigation of activities and tolerance of denitrifying bacteria under alkaline and reducing condition

Mine, Tatsuya*; Mihara, Morihiro;

JNC TN8430 2000-009, 35 Pages, 2000/07

JNC-TN8430-2000-009.pdf:0.88MB

In the geological disposal system of TRU wastes, nitrogen generation by denitrifying bacteria could provide significant impact on the assessment of this system, because nitrate contained in process concentrated liquid waste might be electron acceptor for denitrifying bacteria. In this study, the activities and tolerance of denitrifying bacteria under disposal condition were investigated. pseudomonas denitrificans as denitrifying bacteria was used. The results showed that Pseudomonas denitrificans had activity under reducing condition, but under high pH condition (PH9.5), the activity of Pseudomonas denitrificans was not detected. It is possible that the activity of Pseudomonas denitrificans would be low under disposal condition.

JAEA Reports

Apparent diffusion coefficients of uranium, neptunium and technetium in compacted bentonite under reducing conditions

*; Nakazawa, Toshiyuki*; Ueta, Shinzo*; Shibata, Masahiro

JNC TN8400 99-069, 41 Pages, 1999/11

JNC-TN8400-99-069.pdf:1.62MB

As a part of the evaluation for the sorption phenomena of nuclides in compacted bentonite, apparent diffusivities for uranium, neptunium and technetium that are redox-sensitive elements, were measured under reducing conditions. Bentonite used was a sodium bentonite, Kunigel V1. Apparent diffusivities were measured by using in-diffusion method (concentration profile method), under the conditions with varying dry densities of compacted bentonite and sorts of the solution used for water saturation of bentonite in diffusion experiments. As a result of the measurements, following ranges of values for apparent diffusivities were acquired. ...

JAEA Reports

Hydrogen absorption of titaniam for nuclear waste container in non-oxidizing condition

Tomari, Haruo*; *; Shimogori, Kazutoshi*; Wada, Ryutaro*; ; Taniguchi, Naoki

JNC TN8400 99-076, 100 Pages, 1999/10

JNC-TN8400-99-076.pdf:45.74MB

Effects of bentonite clay, applied potential, pH, of solution and cathodic polarization time on hydrogen absorption into titanium, which is one of the candidate materials of overpack for high-level radioactive waste container, have been investigated in artificial underground water. Considering the result at various test time and assuming the hydrogen absorption is ruled by the paraboric law, the amount of hydrogen after 1000 years exposure calculated to about 17ppm, which will be absorbed at the applied potential of -0.51 vs. SHE corresponds to equilibrium potential of hydrogen. It seems the assumption of the parabolic law and the test period are proper, because the linear relations were obtained between the amount of absorbed hydrogen and the logarithm of the averaged cathodic current and between the slopes of the lines and a square root of the test time. Titanium seems to have a life over 1000 years in deep underground repository according to assumption that about 500ppm absorbed hydrogen is critical for hydrogen embrittlement of titanium.

JAEA Reports

None

*; Nishimura, Tsutomu*; Fujiwara, Kazuo*; *

PNC TJ1058 98-004, 114 Pages, 1998/03

PNC-TJ1058-98-004.pdf:8.4MB

None

JAEA Reports

None

*; Nishimura, Tsutomu*; Fujiwara, Kazuo*; *

PNC TJ1058 98-005, 58 Pages, 1998/02

PNC-TJ1058-98-005.pdf:1.91MB

None

JAEA Reports

None

Sato, Haruo

PNC TN8410 97-075, 29 Pages, 1997/04

PNC-TN8410-97-075.pdf:1.52MB

In the performance assessment of geological disposal of high-level radioactive waste in Japan, redox condition in deep geological environment is considered to be reducing, and Se is one of the important redox sensitive elements. However, no studies on diffusion of Se in bentonite under reducing conditions have been reported yet. This paper describes the results of apparent diffusion coefficients of Se in compacted sodium bentonite obtained as a function of bentonite density under reducing conditions and discusses its diffusion behaviour. Apparent diffusion coefficients of Se in compacted sodium bentonite, Kunigel V1 (constituent montmorillonite 46 49wt%), were obtained in a range of dry densities of bentonite, 800 1800 kgm $^{-3}$ under reducing conditions (Eh vs. SHE -373 -363mV) at room temperature (23.6 23.7 $^{circ}$ C) by in-diffusion method. All the experiments were carried out in an N $_{2}$ -atmospheric glove box (O $_{2}$ 1ppm) and the reducing conditions of the porewater were maintained by continuous contact between compacted bentonite and reducing solution including 5.7 10 $^{-4}$ M-Na $_{2}$ S $_{2}$ O $_{4}$ through a sintered metal filter. The Eh of reducing solution was continuously monitored. Furthermore, a through-diffusion experiment of Na $_{2}$ S $_{2}$ O $_{4}$ was also carried out at a dry density, 1800 kgm $^{-3}$ in order to check the reducing condition of the porewater. The Eh in the measurement cell was confirmed to be the same as that in the tracer cell. The apparent diffusion coefficients of Se were in the range, 6.110 $^{-11}$ 4.310 $^{-10}$ m $^{2}$ s $^{-1}$ and showed a tendency of slight decrease with increasing dry density of bentonite. The dominant species of Se in the porewater under reducing conditions is predicted to be HSe $^{-}$ , and the apparent diffusion coefficients of HSe $^{-}$ in the bentonite were approximately the same as those of TcO $_{4}^{-}$ ...