Here is an article with the most detail I have found in Japanese. I used Chrome's kindly offer to translate it so I could post it here:

"Pressure vessel is damaged," the voice of
Irrigation pipes for damage and, you suspect that some of the heating fuel burn-up, some predict that an out. It also continues to raise the temperature of water injection can increase the amount of fear of water leaking from the pipeline is likely. In the pressure vessel itself is damaged, is heard the sound of this.
TEPCO in the afternoon on May 8, began draining of contaminated water trapped in the condenser, it began to release to the turbine building basement. By switching to reroute the irrigation pipes, overflowing because there is a risk of water trapped in the condenser. This measure is also, however, may leak contaminated water into a trench in the basement if you keep increasing. As of late April, is No. 3 in the trench to a serious rise in water level was only concerned about contamination of soil or even just water, contaminated water will be urgently transferred more and more.
State of mind is more pressure vessels. If the temperature rise can not seem to stop changing the injection route, but it must be discussed in earnest by the damage of pressure vessel leaks. If the failure of a mechanism to cool the nuclear fuel emergency occurs, and continues to overheat and melt the core of nuclear fuel, which could lead to disaster.
We are what we repeatedly do - Aristotle