Journal of Nuclear Fuel Cycle and Environment
Online ISSN : 2186-7135
Print ISSN : 1884-7579
ISSN-L : 1343-4446
Volume 11, Issue 1
Displaying 1-4 of 4 articles from this issue
Research Article
  • Shinya Nagasaki, Kenichiro Okamoto, Satoru Tanaka, Yoshiko Haruguchi, ...
    2004 Volume 11 Issue 1 Pages 3-10
    Published: 2004
    Released on J-STAGE: March 31, 2013
    JOURNAL FREE ACCESS
      In order to understand the fixation mechanism of IO3- in ettringite, we studied the desorption behavior of IO3- from the IO3- sorbed ettringite and the IO3- type synthesized ettringite which was prepared by using IO3- instead of SO42-. Desorption behavior of IO3- was discussed by using distilled water, KOH (pH10.6) solution, 20 mM-K2SO4+KOH (pH10.6) solution, 20 mM-K2SO3+KOH (pH10.6) solution, and ettringite equilibrium solution, and it was found that the ettringite-like structure was preserved during the desorption reactions and that desorption fractionation of IO3- was about 1 to 7 % of total amounts of IO3- sorbed in ettringite. Change in the lattice constants of ettringite-like structure was evaluated for the the IO3- sorbed ettringite when IO3- was desorbed by 0.4 M-K2SO4+KOH (pH10.6) solution for one day, and the good correlation between the lattice constant change and the desorption amount of IO3- was observed.
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Technical Report
  • Takeshi Ishikura, Kenji Takahashi, Hiroyuki Ueki, Daiichiro Oguri
    2004 Volume 11 Issue 1 Pages 11-20
    Published: 2004
    Released on J-STAGE: March 31, 2013
    JOURNAL FREE ACCESS
      A large quantity and various level of radioactive waste is arisen due to nuclear power plant decommissioning. Minimizing radioactive waste is, therefore, vital in reducing the burden to the radioactive waste disposal site capacity. The authors have developed a technique to fill low level radioactive molten metal as filler in thin waste disposal containers. This is termed the “radioactive metal casting process for thin container”. Demonstration tests using actual scale containers consist of 3 themes, i.e., conditions to properly fill molten metal in the container with pre-placed metal, thinning container material with support of heat removal blocks, and metal impurity limit mixed in raw waste metal. As a result, it was demonstrated that the casting process can achieve a good fill ratio with no harmful loss to the pre-placed metal and no harmful distortion to the container or shielding layer, when the filler metal was poured into the container with a proper layout of heat removal blocks at the proper temperature.
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  • Takeshi Ishikura, Jun-ichi Takahashi, Yuichi Shoji, Toshiki Fukui
    2004 Volume 11 Issue 1 Pages 21-28
    Published: 2004
    Released on J-STAGE: March 31, 2013
    JOURNAL FREE ACCESS
      A large amount of low-level radioactive waste metal will be generated from a nuclear power plant decommissioning. Disposal of the radioactive waste must be a burden to the disposal facility, therefore reducing the disposal volume must be important issue to solve. Toward minimizing the volume of radioactive waste, the authors developed a new technique to separate cobalt and nickel elements (not nuclide) from radioactive metal, especially for activated metal, thereby to lower radioactivity concentration of the metal. Screening tests and demonstration tests were implemented. In the screening tests, three kinds of processes were compared on the performance in small-scale apparatus and the Oxygen Sparging Process was seen to have most feasible performance. In the demonstration tests, the prototype apparatus of the Oxygen Sparging Process demonstrated that it could separate cobalt from carbon steel with a decontamination factor of 100 and with an iron recovery ratio of 60% in proper process conditions.
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  • Takeshi Isogai, Takashi Jintoku, Hiroshi Sasamoto
    2004 Volume 11 Issue 1 Pages 29-36
    Published: 2004
    Released on J-STAGE: March 31, 2013
    JOURNAL FREE ACCESS
      We have been developping techniques for measuring the chemical compositions of porewaters in compacted bentonite as a function of time. The present emphasis of this development effort is on pH measurements, which were carried out in the present study using low-decolorant pH test papers and high-absorbancy pads embedded in compacted bentonite (Kunigel-V1®=100%) having dry densitie of 1.6g/cm3. The experiments were conducted in a controlled-atmosphere glove box (O2 (g) ≦1 ppm) using distilled water, synthesized seawater and a low-alkaline cement porewater (i.e., HFSC: High Flyash contained Silica fume Cement) as initial solutions. The pH of the distilled water and synthesized seawater was adjusted to pH 9 by adding NaOH solution. Distilled water was reacted with crushed HFSC to produce a solution representing low-alkaline cement porewater (pH≒11).
      The measured pH profiles based on this technique vary temporally and spatially. The variation of pH profiles depends on bentonite density and initial solution chemistry. In compacted bentonite contacted with distilled water, most of the profile did not vary significantly (pH=8.0 to 9.0) during the experiment, but the pH of porewaters near the infiltration interface slightly decreased (pH=7.5~8.5 → pH=7.0~8.0). In the experiment using synthesized seawater, the pH values were roughly constant at the interface between 6.5 and 7.0, but the pH of porewaters further away from the interface slightly decreased with time (pH=6.5~7.0 → pH=6.0~6.5). Like the experiment with involving distilled water, the pH of porewaters contacted with HFSC solution further away from the interface were roughly constant between 8.5 and 10.0, but the pH of porewaters near the infiltration surface significantly decreased with time from pH=9.5 to pH 7.5~8.5.
      The pH values measured are reasonably consistent with values measured by an alternative technique using pH-indicator with spectrophotometer, and are also consistent with the results of mineral-water equilibrium modeling. This favorable comparison suggests that this technique can be used with confidence to obtain accurate measurements of the pH of bentonite porewaters.
      Preliminary thermodynamic calculation using geochemical code PHREEQC suggests that the pH decrease near the infiltration interface observed in experiments using distilled water can be due to partial oxidation of trace amounts of pyrite in Kunigel-V1®.
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