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Matsumoto, Toshiyuki; Oura, Masato*; Yato, Yasuo*
JAEA-Research 2007-049, 73 Pages, 2007/07
JAEA-Research-2007-049.pdf:40.32MB
A large amount of sodium containing radioactive waste will come up at the time of final shutdown/ decommission of FBR plant. The radioactive waste is managed as solid state material in a closed can in Japan. As for the sodium, there is no established method to convert the radioactive sodium to solid waste. Further, the sodium is highly reactive. Thus, it is recommended to convert the sodium to a stable substance before the solidification process. One of the stabilizing methods is conversion of sodium into sodium hydroxide solution. These stabilization and solidification processes should be safe, economical, and efficient. In order to develop such sodium disposal technology, nonradioactive sodium was used and a basic experiment was performed. Waste-fluid Slag Solidification method was employed as the solidification process of sodium hydroxide solution. Experimental parameters were mixing ratio of the sodium hydroxide and the slag solidification material, temperature and concentration of the sodium hydroxide. The best parameters were obtained to achieve the maximum filling ratio of the sodium hydroxide under a condition of enough high compressive strength of the solidified waste. In a beaker level test, the solidified waste was kept in a long term and it was shown that there was no change of appearance, density, and also the compressive strength was kept at a target value. In a real scale test, homogeneous profiles of the density and the compressive strength were obtained. The compressive strength was higher than the target value. It was shown that the Waste-fluid Slag Solidification method can be applied to the solidification process of the sodium hydroxide solution, which was produced by the stabilization process.
Matsumoto, Toshiyuki; Yoshida, Eiichi; Suzuki, Shigeaki*; Yasu, Tomohisa*
JAEA-Technology 2007-035, 35 Pages, 2007/03
JAEA-Technology-2007-035.pdf:23.9MB
In the future, a large amount of sodium (Na) containing radioactive wastes must be processed at the time of final shutdown/ decommissioning of FBR plant or radioactive sodium facilities in Japan. Therefore, its disposal technology should be established in consideration of economical efficiency, safety, etc. In the existing technology, since the method of processing sodium directly into radioactive waste is not established, conversion of sodium into chemically stable material can be considered. Then, basic experiments in which sodium was injected at 10 kg/h into solution of sodium hydroxide (NaOH) were conducted, with the improved Sodium Conversion Test Apparatus (SCOT). The conditions of NaOH solution were temperature of 100
C, and NaOH concentration of 45-50 wt%. Consequently, the injected sodium reacted completely in the NaOH solution, and NaOH temperature, NaOH concentration, etc. were controlled properly. It validated that the system of this apparatus was appropriate. Moreover, in case sodium is injected into NaOH solution, a nozzle blockades sometimes. Therefore, the methods to eliminate the cause of nozzle blockage were examined.
Matsumoto, Toshiyuki; Yoshida, Eiichi; Suzuki, Shigeaki*; Yasu, Tomohisa*
JAEA-Research 2007-038, 32 Pages, 2007/03
JAEA-Research-2007-038.pdf:5.06MB
Decommissioning of a sodium cooled fast reactor or an experimental facility which used radioactive sodium will bring a lot of radioactive sodium. However, technology to deal with such the radioactive sodium and decommission is not well established in Japan. Then, basic experimental study has been carried out in order to find and estimate an economic and safety process of the radioactive sodium decommission. There were some examples in overseas to convert the sodium into sodium hydroxide via sodium-water reaction. This method was examined by a basic sodium conversion test apparatus. In the experiment, liquid metal sodium was injected into the sodium hydroxide. Influences of temperature and concentration of the sodium hydroxide were investigated. Nitrogen gas was injected into the sodium hydroxide as atomizing gas in order to protect the sodium injection nozzle and also to mix the sodium. Then the gas flow rate was also varied to see the desired effects. Injected sodium temperature and mass flow rate were fixed at 200C and 10kg/h, respectively. The atomizing gas flow rate, the temperature and concentration of the sodium hydroxide were varied in ranges of 60-100 l/min, 70-100C and 40-60wt%, respectively. The influences of these parameters on the sodium conversion reaction were evaluated. The experiments showed that increase of the atomizing gas resulted in stable injection of the sodium and also larger reaction area. The temperature of the sodium hydroxide had small influences on the reaction, however, the sodium injection nozzle tended to choke up when the temperature was less than 70C. The lower concentration resulted in larger temperature fluctuation and also enlarged the reaction area. Unstable reaction, for example, sudden increase of reaction rate due to excess sodium, was not found under the conditions above listed ranges and stable sodium conversion was confirmed.
Nakayama, Fusao*; Enokido, Yuji*; Yoshida, Eiichi; Matsumoto, Toshiyuki; Hasebe, Shinichi
JNC TN9420 2005-001, 115 Pages, 2005/03
JNC-TN9420-2005-001.pdf:9.24MB
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Matsumoto, Toshiyuki; Yoshida, Eiichi; Suzuki, Shigeaki*; Yasu, Tomohisa*
no journal, ,
no abstracts in English