It doesn't even mention the 4th, There are six, and units 4,5,6 were already in a cold state before the tsunami (for maintenance); they're not involved. You

It doesn't even mention the 4th, There are six, and units 4,5,6 were already in a cold state before the tsunami (for maintenance); they're not involved. You could be thinking of Fukushima Daini, which has four reactors.