Sankei Shimbun dated January 19, 2012 published an article "TEPCO left out the disconnection of emergency power supply for Fukushima nuclear data transmission equipment four months before the earthquake". Other newspapers published similar articles.
Facts are as below:
Disconnected and left out the power supply from the emergency power supply (uninterruptible power supply)
We proposed to enhance power supply to the media converter (MC)*1 by newly connecting the emergency power supply (uninterruptible power supply). We did not disconnect an existing connection from the emergency power supply.
Also, the AC power supply had a backup power. The building where the media converter (MC) was located was supposed to receive power from Okuma line 1 or TEPCO nuclear line.
Why there was no connection with the emergency power supply (uninterruptible power supply)
In installing the media converter (MC), the location for L3 switch*2 instructed by the Nuclear Safety Inspector was incorrect. Because of this, the length of the power cable was too short to connect. As such, we explained the situation to the Nuclear Safety Inspector, connected to the existing AC power supply and began operation of the Emergency Response Support System (ERSS).
Broadcasts regarding the impact on the radioactivity dispersing forecast
According to our analysis, the time when the reactor core of Unit 1, Fukushima Daiichi NPS was exposed (the water level went down to the top of active fuel) was around 5:46 pm, March 11. Before 4:43 pm, we believe that there was no release of radioactive substances when we could not transmit data due to malfunction of the national disaster prevention network.
Broadcast in relation to instruction / request for connection to the emergency power supply from the government and Japan Nuclear Energy Safety Organization
There was no instruction / request from the government or Japan Nuclear Energy Safety Organization.
(Reference: outline of the connection work with UPS)
We implemented to connect TEPCO's network with the national disaster prevention network in order to transmit power station plant data to the Emergency Response Support System (ERSS). We planned to newly install the media converter (MC), connect with the L3 switch, a national property and at the same time, connect with the national emergency power supply (uninterruptible power supply).
*1 media converter (MC): an equipment to connect and convert signals between different devices such as optical fibers and cables.
*2 L3 switch (layer 3 switch): this controls routing by IP address and relays packets to the output port that corresponds to the IP address.
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