It's been about 14 months since the hastily rigged system of transporting and treating the contaminated water and circulating the treated water back into the Reactor Pressure Vessels (1, 2 and 3) to cool the melted fuel somehow. The pipes used were Kanaflex pipes, which TEPCO just started to replace with rigid pipes.
But the company didn't replace the Kanaflex pipe that goes from the Reactor 3 turbine building basement through the Reactor 4 turbine building first floor in front of the room with electrical power panels on the way to the building that stores the highly contaminated water before the water gets treated by SARRY. That's what leaked, and the water got inside the electrical power panel room.
The water, coming out of the basement of Reactor 3's turbine building, has 85,000 becquerels/cubic centimeter of radioactive cesium, as of August 9, 2012 at 3:20PM, according to the company's handout for the press on August 13, 2012. One order of magnitude more cesium than in the water in the Reactor 4 turbine building basement.
There is no information of air radiation levels inside the electrical power panel room. How are they going to clean this up, I have no idea. It is not like the past leaks where at least "treated" water leaked.
If they cannot clean up the room, and if anything happens to the power panel, they may have some serious problem.
From Jiji Tsushin (8/14/2012):
Fukushima I Nuke Plant: contaminated water leak in the turbine building of Reactor 4, water inside the electrical power panel room - damage to the water transfer pipe suspected
At 11:15AM on August 14, a TEPCO employee patrolling the site found a puddle of water on the floor of the electrical power panel room on the 1st floor of Reactor 4 turbine building at FUkushima I Nuclear Power Plant. The pipe that transfers the highly contaminated water from the basement of Reactor 3 turbine building runs along the corridor in front ot the room. TEPCO suspects the leak may be from the pipe, and is investigating.
The electric power panel is in the room to provide power to various equipment, but there was no effect on the panel from the leak.
According to TEPCO, the water was seeping in to the room from the corridor. When the company stopped the transfer of the contaminated water at 12:20PM, the seepage stopped at about 1PM. The room is about 350 square meters, and the water is about 1 centimeter deep. TEPCO says there is no leak from the room. The density of radioactive cesium in the water is estimated to be several tens of thousands of becquerels per cubic centimeter.
As the damage to the pipes used to transfer the contaminated water [Kanaflex] has been occurring frequently, TEPCO is replacing these pipes with polyethylene pipes which are more reliable. However, the pipe in front of the electrical power panel room hasn't been replaced yet. The company is trying to identify the location of the damage, and figure out how the water got inside the room.
It is "obon" in Japan, and TEPCO (Headquarters at least) is taking August 14 and 15 off. No press conference is scheduled, as far as I checked, until August 16.