3 Sieverts Per Hour Radiation Leak Halts Water Decontamination At Fukushima Plant

Potent radiation leak halts water decontamination operations at Fukushima plant (Mainichi, August 23, 2011):

Operations to decontaminate highly radioactive water at the crisis-stricken Fukushima No. 1 Nuclear Power Plant came to a 13-hour halt when a section of pipe emitting 3 sieverts of radiation per hour in one decontamination system was discovered, plant operator Tokyo Electric Power Co. (TEPCO) has announced.

According to TEPCO, the high radiation emissions from the pipe section were discovered at just after 7 a.m. on Aug. 22 while workers were doing the first ever change-out of a decontamination system part for absorbing radioactive cesium. Work on the part change was stopped immediately. After washing radioactive mud away from the area, radiation levels dropped, and decontamination operations resumed at about 8:15 p.m., though the delay pushed replacement of the cesium absorption component back to Aug. 23. TEPCO officials apparently still do not know what caused the radiation leak.

The water decontamination system, called “Sally,” was built by electronics and heavy machinery giant Toshiba Corp. There are high expectations for Sally’s performance after two other decontamination systems at the site — one made in the United States and the other in France — continued to have problems and delays.

This is the third time for high radiation emissions to be discovered at the plant in August. On Aug. 1, emissions of 10 sieverts per hour were detected coming from the substructure of exhaust pipes in the No. 1 and 2 reactor housings, while on Aug. 2 emissions of more than 5 sieverts per hour were found in the air conditioning room in the No. 1 reactor building.

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