TVFガラス溶融炉の炉抵抗予測に関する数値解析

Numerical Analysis of Historical Change of the Electric Resistance in the TVF Glass Melter

河村 拓己*; 堺 公明

Kawamura, Takumi*; Sakai, Takaaki

東海再処理工場のTVFガラス溶融炉について、白金族元素の堆積検知及び除去を実施する観点から,炉抵抗の測定値などから白金族元素の堆積状況や電流密度分布について推定する手法構築が重要となっている。そのため,本研究では電磁界解析コードMAGNA-FIMによる電場解析を実施し,白金族元素の堆積状況及びガラス温度が炉の抵抗に及ぼす影響特性について評価した。また,TVF1号溶融炉の運転履歴を解析することにより、炉抵抗と白金族元素の堆積状況の推移について評価する手法を検討した。その結果,堆積物と電極の接触がない場合、堆積物の白金族元素濃度及び体積は,炉抵抗に顕著な影響を及ぼさないが,堆積物と電極が接触することにより炉抵抗を大きく低下させることわかった。また,接触がない場合、炉底部の堆積物温度は炉抵抗に大きな影響を及ぼさないが,炉上部のガラス温度は接触の有無にかかわらず炉抵抗に対して感度を有することがわかった。これらの評価に基づき,TVF1号溶融炉の炉抵抗低下の経緯に適合する解析モデルを構築した。運転データの電極間電圧及び炉内温度を入力とするとともに,堆積物は運転バッチごとに徐々に堆積したと推定し,白金族元素の堆積濃度は、直線的に増加すると仮定した。その結果,炉抵抗の推移を概ね再現することができた。これにより,ガラス溶融炉の抵抗値評価による堆積状況推定について見通しを得ることができた。

Concerning to the TVF glass melter in the Tokai reprocessing center, it is being planned to detect the deposition of the platinoid elements in a glass melter and remove them periodically to extend the melter lifetime. Numerical analysis has been performed for the electric resistance evaluation in order to estimate the sedimentation situation and current density distribution from the melter resistance. Electric field analysis was carried out by using MAGNA-FIM code and the influence factors to melter resistance was evaluated concerning to the sedimentation situation and glass temperature. In addition, transition of the sedimentation and melter resistance was estimated from the operation history of the TVF-1 melter. As a result, the followings were obtained. From the evaluation of the influence factors to melter resistance, it turns out that the volume and the platinoid elements concentration of a sediment influence notably to melter resistance when the sediment contacts to electrodes. The sediment temperature at the melter bottom has small sensitivity in case of the contact situation. the glass temperature in the melter upper part, however, has big sensitivity in melter resistance irrespective of the existence of contact. Based on the above sensitivity evaluation, numerical analysis was carried out supposing the sedimentation process which suits to a melter resistance fall during the operation history of the TVF-1 melter. As input conditions, the voltage between electrodes and the temperature in the melter were referred from the operation history data. It was assumed that the platinoid elements concentration in a sediment increased constantly for every operation batch. As a result, the characteristics of melter resistance history was reproduced successfully in general. Thereby, it became prospective to predict the sedimentation situation by using the new resistance analysis model for the glass melter.