高速増殖炉用抵抗方式ナトリウム温度計測システム

A Novel non-intrusive resistance thermometer for sodium in fast breeder reactor

山崎 弘郎*; 本多 敏*; 上田 雅司 ; 遠藤 昭*; 笛木 学*

Yamasaki, Hiro*; Honda, Satoshi*; Ueda, Masashi; Endo, Akira*; Fueki, Manabu*

高速増殖炉は、輸入に依存するウラニウム資源を有効に活用できるため、日本のエネルギー事情に適した動力炉として期待されている。一方、同炉の炉心では、熱出力密度が著しく大きいために、冷却材として熱伝達特性が優れた液体ナトリウムが使用される。本論文は液体ナトリウムの温度を管路の外側から電気抵抗方式により計測する新しい温度計測手法について、理論的解析,数値シミュレーション,試作検討結果などを述べたものである。

A non-intrusive temperature sensing system is proposed. It is developed for temperature measurement of liquid sodium coolant in fast breeder reactor. Liquid sodium is used as coolant due to high heat flux density in the reactor core. In this paper, the results of our feasibility study by 2-dimensional numerical simulation, small size experimental test done by Japan Atomic Energy Agency Oarai Institute, and theoretical analysis are described. The basic principle of temperature measurement is resistant thermometry of liquid sodium. The resistivity of liquid sodium is quite lower than that of the stainless steel (SUS304), which is used in the pipe wall. The resistivity temperature coefficient of liquid sodium(0.337%/deg) is higher than that of stainless steel(0.0865%/deg). If we feed electric current perpendicular to the axis of flow pipe, the current penetrates the pipe wall and flow across the liquid. The current concentrates the liquid sodium, only small portion of the current flows along the pipe wall. The electric potential distribution is almost dominated by resistivity of sodium. The potential distribution can be measured along the out side of the pipe wall. The potential difference between two fixed points on the pipe wall indicates the resistivity of sodium So the sodium temperature can be measured by potential difference. Measurement accuracy of 5C is obtained in experimental tests. Better estimation data are obtained by theoretical analysis using three dimensional model.