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松本 歩; 大場 弘則; 利光 正章; 赤岡 克昭; 若井田 育夫
no journal, ,
To observe the inside of the damaged nuclear reactors in Fukushima Daiichi Nuclear Power Station, a fiber-optic laser-induced breakdown spectroscopy (LIBS) instrument has been developed. Recently, a long pulse laser is expected to avoid the damage of an optical fiber probe and to enable the transmission of higher energy. However, the laser ablation process of solid samples in air with the long pulse has not been clarified enough. In this study, temporal variations of the plasma emission were measured with short and long nanosecond pulses. As a result, the delay time from the pulse irradiation to the plasma generation and the temporal profile of the emission intensity are considerably different depending on the pulse duration. The difference of the plasma formation process during the pulse irradiation may affect the LIBS signal observed after several microseconds.
Ruas, A.; 大場 弘則; 赤岡 克昭; 若井田 育夫
no journal, ,
The laser-induced breakdown spectroscopy (LIBS) is used for the real-time, in situ and remote elemental analysis without any pretreatment. These advantages are very interesting for the post-accident environment analysis inside Fukushima Daiichi Nuclear Power Plant and for monitoring the contaminated aqueous solutions in decommissioning process. Despite the difficulty of using LIBS with liquid samples, the thin-sheet liquid jet can cost-effectively counter balance this issue. The accurate determination of the zirconium concentration, including in aqueous medium, is of prime interest for waste management. In this context, the present study focuses on the zirconium determination in aqueous solutions. The LIBS experimental conditions were optimized, in particular the laser energy and the acquisition delay, to determine the most suited parameters for zirconium analysis in aqueous solution.
若井田 育夫; 大場 弘則; 大場 正規; 松本 歩; Ruas, A.; 利光 正章; 赤岡 克昭; 宮部 昌文
no journal, ,
福島第一原子力発電所廃止措置における炉内分析手法として光ファイバを活用したレーザー誘起発光分光法(ファイバLIBS)を提案し、Zr/U酸化物模擬デブリ試料に適用することで、その場分析への適用の可能性を確かめてきた。より長尺の光ファイバ伝搬における減衰を補償するため、100nsのロングパルスレーザーを導入し、レーザー入力の増大が図れることや、時間積分観測による発光信号の増倍が得られることを確認した。さらに、発光信号の増大を図る目的で、レーザー照射時にマイクロ波を重畳するマイクロ波LIBS法を導入し、大気中においても、約10倍程度の発光量の増加も確かめた。冷却水等に溶存する元素分析については、溶液から液体薄膜を形成し、レーザーを照射することで原子発光を得た。Zr硝酸塩水溶液に適用した結果、ppmオーダーの検出下限が得られることが示された。