It can be hard to sort out exactly what's happening in Japan right now, or what the status of the nuclear situation is. Euan Mearns has done everyone a great service in pulling together a summary of known and unknown and credible, intelligent speculation, while clearly indicating which is which. It is well worth a read. Consider this useful analysis by Joules Burn, quoted in the piece:
Since residual weld stresses and tensile stress in piping, valves, control tubing, etc are always present, Standard Operating Reactor water quality standards require keeping chlorides at parts per billion…