検索対象:     
報告書番号:
※ 半角英数字
 年 ~ 
 年

大量ナトリウムの安定化処理に関する技術開発; ナトリウム転換の手法と基礎特性

Development of sodium conversion technology; Method and basic features of sodium conversion process

松本 寿之; 吉田 英一; 鈴木 重哲*; 安 智久*

Matsumoto, Toshiyuki; Yoshida, Eiichi; Suzuki, Shigeaki*; Yasu, Tomohisa*

ナトリウムを冷却材とする高速炉プラントの廃止措置やウランなどの放射性核種を微量に含むナトリウムを使用した試験施設を解体する際に、放射性物質として取り扱うべき大量のナトリウムが発生すると考えられる。このようなナトリウムを放射性廃棄物として直接処分する技術・方法は、国内においてまだ確立していない。そのため、経済性や安全性等を考慮した処分技術の検討・評価を行うことを目的に基礎的な試験研究を実施した。これまでに海外で先行例のある、ナトリウム-水反応によりナトリウムを水酸化ナトリウムに転換する手法を対象に、ナトリウム転換基礎試験装置を用いて試験を実施した。本試験では、液体ナトリウムを水酸化ナトリウム溶液中に注入し水酸化ナトリウムに転換する際の、水酸化ナトリウム溶液の濃度・温度,アトマイジングガス流量の影響を把握した。注入ナトリウム温度200$$^{circ}$$C,注入流速10kg/hを一定とし、アトマイジングガス流量60$$sim$$100NL/min,水酸化ナトリウム温度70$$sim$$100$$^{circ}$$C,水酸化ナトリウム濃度40$$sim$$60wt%の範囲で、ナトリウム転換処理に与える影響を評価した。

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 200$$^{circ}$$C 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, 70-100$$^{circ}$$C 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 70$$^{circ}$$C. 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.

Access

:

- Accesses

InCites™

:

Altmetrics

:

[CLARIVATE ANALYTICS], [WEB OF SCIENCE], [HIGHLY CITED PAPER & CUP LOGO] and [HOT PAPER & FIRE LOGO] are trademarks of Clarivate Analytics, and/or its affiliated company or companies, and used herein by permission and/or license.