#Fukushima I Nuke Plant: Contaminated Water Treatment System at 76% Operating Rate

TEPCO's target was at least 80%, and they were hoping to ramp it up to 90% quickly. Now the company says it will focus on achieving the steady 80% for now.

At least part of the reason for the less than desired operating rate looks to be Kurion's system.

Kurion's system has a decontamination factor (DF) of about 17, instead of 1,000 that was hoped for when the system started. In other words, instead of reducing 2 million becquerels/cubic centimeter of radioactive cesium in the water to 2,000 becquerels/cubic meters (DF of 1,000), Kurion's system reduces 2 million becquerels/cubic centimeter of cesium to 120,000 becquerels/cubic centimeter (DF of about 17).

TEPCO has found out that the Kurion's vessels that contain different types of zeolite for removing different nuclides need to be exchanged far more frequently than planned (which was one a day). In addition, the system needs "flushing" (cleaning out the system with water) every time a vessel is changed, and that results in several hours of downtime for the entire system.

From TEPCO's handout for the press on July 6, "flushing" operations since June 23 (link goes to the Japanese handout, as English handout is missing some info):

June 23: 1:00PM to 2:44PM
June 24: 10:00AM to 12:50PM
June 25: 10:00AM to 3:00PM
June 26: 10:00AM to 18:10PM
June 28: 10:06AM to 12:24PM
June 29: 10:45AM to 2:13PM
June 30: 10:46AM to 1:35PM
July 2: 10:30AM to 1:45PM
July 3: 10:39AM to 12:50PM
July 5: 10:30AM to 12:55PM

According to the tweets from a Fukushima I Nuke Plant worker, the system seems to stop at other times for other undisclosed reasons.

TEPCO changes a vessel when the surface radiation of the vessel reaches 4 millisieverts/hour. Since June 17 when the entire system started to operate, TEPCO has changed 43 vessels as of July 5. In 7 more days TEPCO estimates there will be additional 20 used vessels. TEPCO has the storage capacity of this highly radioactive vessels up to 192. At 20 vessels per week, the storage will reach capacity in less than 8 weeks.

For more on the contaminated water treatment system operation, TEPCO has a detailed report it submitted to the NISA on July 6.

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