The pumps at AREVA's portion of the water treatment system at Fukushima I Nuclear Power Plant shut down automatically when too much water went through them. TEPCO has been conducting the test run after the Kurion's problem earlier.AREVA's subsystem comes after Kurion's (cesium absorption) which in turn comes after Toshiba's (oil separation). After AREVA's subsystem, the water goes to Hitachi's for desalination.
It was the 6th time since the test run started on June 10 that the system had stopped, as the following Yomiuri article says.
From Yomiuri Shinbun (1:06PM JST 6/21/2011):
東京電力は２１日、福島第一原子力発電所で、再稼働に向け通水試験を行っていた汚染水処理システムが午前７時２０分頃に緊急停止したと発表した。
TEPCO announced on June 21 that the water treatment system for highly contaminated water at Fukushima I Nuclear Power Plant had an emergency shut down at 7:20AM. TEPCO was running the test run in order to resume the full-scale operation.
システムのうち仏アレバ社の沈殿・除去装置で、汚染水を流す主系統につながる薬液注入ラインのポンプ２台が自動停止した。東電はポンプを調整し同日午後、全体の通水試験を再開した。試運転が本格化した１０日以降、トラブルや故障でシステムが停止したのは６回目。
The problem was at AREVA's subsystem for decontamination. Two pumps for the chemical injection line that connects to the main line for the contaminated water were shut down automatically. TEPCO adjusted the pumps, and the test run resumed in the afternoon. It was the 6th time since the test run started on June 10 that the system had stopped because of troubles and malfunctions.
不具合は除染装置につながるポンプで見つかった。薬剤注入ラインに希釈用の水を供給しているが、流す水の量が多すぎて停止したとみられる。東電では流量を調整する。システムは複数の装置の組み合わせで、ア社の装置は薬液や砂を混ぜてセシウムやストロンチウムを沈殿、除去する。
The pumps feed water to the chemical injection line for dilution. They seem to have stopped when too much water went through. TEPCO will adjust the amount of water. The water treatment system is a combination of multiple subsystems, and AREVA's subsystem mixes chemicals and silica to remove cesium and strontium.