Fukushima Daiichi Nuclear Plant Weekly Review

A disconnected hose recently flooded part of the unit 3 turbine building at Fukushima Daiichi, while a robot has begun to search for leaks in the containment structure of unit 2.

Recent developments related to the Japanese nuclear plant blacked out by last year's earthquake and tsunami include:

Unit 2 Torus Piping Surveyed

Tokyo Electric Power Co. has deployed a four-legged robot to the base of unit 2 to search for leaks in pipes that connect the reactor pressure vessel to the torus. The Asahi Shimbun reported that the first inspection on Tuesday surveyed one of eight pipes but did not locate the source of highly radioactive water seeping into the unit's basement. It was the first detailed inspection of the area, and the search will continue next week.

Leak inside Unit 3 turbine building. Source: TEPCOHose Leaks at Unit 3

Also on Tuesday, a worker discovered water accumulating on the west side of the first floor of unit 1's turbine building. According to a TEPCO release, the leak amounted to 15 cubic meters of water with concentrations of cesium 137 measured at 74 becquerels per cubic centimeter. The water did not flow out of the building, TEPCO reported. Subsequent investigation located a disconnected section of hose that ran to a fire hydrant. The hose had earlier been used in a pressure test.  

Tighter Evacuation Thresholds Proposed

Japan's new nuclear regulator on Thursday proposed nuclear evacuation standards that are twice as cautious as those recommended by the International Atomic Energy Agency. Draft standards by the Nuclear Regulation Authority call for immediate evacuations in areas with radiation detected at 500 microsieverts per hour in the event of an accident, the Yomiuri Shimbun reported, compared to 1,000 microsieverts per hour in the IAEA's recommendations. Evacuations would be mandatory within a week in areas exceeding 20 microsieverts per hour, compared to the IAEA's 100 microsievert standard. A panel of experts will now review the proposal, which is scheduled to be finalized by the end of the year. 

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