The entire ALPS multi-nuclide removal system is down again, as Line C has just been stopped as the water sample from Line C is found with high calcium content.
Line A was stopped three days ago, and Line B has been idle since March this year, when the water treated in Line B was found with high beta (in the order of 10 million Bq/L) and brand-new storage tanks got contaminated.
Stopping ALPS won't affect the cooling of reactors, as the treatment for the cooling water is done by SARRY (removal of radioactive cesium) and by the reverse osmosis apparatus (desalination).
From TEPCO's email alert for the press, 5/20/2014:
Line C of the multi-nuclide removal system ALPS has been in operation. However, we noted in today (May 20, 2014)'s scheduled sampling that the water [coming out of] Line C was clouded, and that it had high calcium content.
Therefore, we stopped Line C at 9:00AM today, and switched it to the circulation stand-by operation. [I don't know exactly what TEPCO means; I'm guessing they are circulating the water within Line C instead of sending treated water into a storage tank.]
As the result, all three lines of ALPS have stopped treatment operation.
We will investigate the cause.
The cause, if it is the same as Line A which stopped three days ago after the water sample was found with high calcium content, is likely to be the defective cross flow filter, like this one on Line B (from TEPCO's Roadmap update page 24, 4/24/2014) (English labels are by me):
Whether the defective gasket is due to material defect, design defect or irradiation is unknown at this point.