On November 5, 2009, we received a directive document from the Nuclear and Industrial Safety Agency of the Ministry of Economy, Trade and Industry requiring us to investigate on improper connection of the drainpipes at our nuclear power stations, in response to the leakage of water including tritium due to improper drainpipe connection occurred at Unit 1 of Fukushima Daini Nuclear Power Station on October 28, 2009 and the improper drainpipe connection found at Unit 1 of Kashiwazaki-Kariwa Nuclear Power Station on November 4, 2009.

In accordance with the directive document, we have investigated on improper connection of the radioactive waste treatment system pipes at our nuclear power stations, and submitted a summarized report (including investigation results and countermeasures) to NISA on February 2, 2010.

On the same day, we received a directive document^* "Improper connection of the radioactive waste treatment system drainpipes at Fukushima Daiichi Nuclear Power Station, Fukushima Daini Nuclear Power Station and Kashiwazaki-Kariwa Nuclear Power Station (Direction)" from NISA.

According to the directive document, we have summarized the root cause of the matter and recurrence prevention measures, and submitted it to NISA on July 29, 2012. (Previously announced on November 5 and 11, 2009, February 2, July 29, 2010.)

Corrective measures were implemented on the drainpipes where improper connection was found in consideration of the timing of the regular inspection, and all the corrective measures have been implemented in February 2011. Today, we have submitted a summarized report to NISA regarding the corrective measures implemented on the total of 30 locations where improper connection was found.

Though we initially intended to submit the summarized report soon after the completion of corrective measures implementation, it has been postponed due to the Tohoku-Chihou-Taiheiyou-Oki Earthquake which occurred on March 11, 2011.

Attachment
"Corrective Measures Implementation for Improper Connection of the Radioactive Waste Treatment System Pipes at our Nuclear Power Stations"（PDF 245KB）

* Directive document
"Improper connection of the radioactive waste treatment system drainpipes at Fukushima Daiichi Nuclear Power Station, Fukushima Daini Nuclear Power Station and Kashiwazaki-Kariwa Nuclear Power Station (Direction)" (January 25, 2010, NISA No.2)

The aforementioned documents are available only in Japanese. We apologize for the inconvenience this may cause.