It's the lowest operating rate ever, since the system went into full operation with highly contaminated water about a month ago.
The news was released one day after the announcement of the successful completion of the "step 1" in TEPCO/Japanese government's "roadmap" to somewhere (over the rainbow, way up high... it is not reality-based any more, if ever).
From Yomiuri Shinbun (7/20/2011):
Highly radioactive sludge that no one can touch. Or it could be rotten fish bits.
TEPCO announced on July 20 that the operating rate of the contaminated water treatment system at Fukushima I Nuclear Power Plant for the week ended on July 19 was 53%, the lowest ever since the system started the full operation.
TEPCO's target operating rate for July was 80%.
The company calculates the operating rate every week. The reasons for the low operating rate are: low flow rate of 37 cubic meters (tonnes) per hour, instead of 50 cubic meters per hour as the system is designed, and stoppage due to various problems. At the current flow rate, even if there was no problem and the system could be run continuously, the operating rate would only be 74%. TEPCO says it is possible that the target for water treatment may be revised.
The low flow rate may be caused by the sludge in the pipes, but at this point TEPCO hasn't been able to identify the cause. The company will try to improve the system somehow, and hopes to raise the operating rate to 70% during the week starting July 20, and to 90% in August.
TEPCO must be counting on Toshiba's SARRY, which is supposed to come online in early August. TEPCO had better hope SARRY will deliver.