Contaminated water accumulating at Fukushima Daiichi still poses problems for TEPCO

Water is crucial to the continued safety and stability of the Fukushima Daiichi plant.  TEPCO is still injecting hundreds of thousands of gallons into the reactors every day to keep them from overheating again. Contaminated water is currently estimated to be leaking out of the reactors at a rate of 10,000 tons a month, cleaning it up and storing the excess is a constant challenge.

After being used to cool the reactors, the water goes through a processing facility so that radioactive substances are removed to a certain extent. Some of the water is then recycled as a coolant and the remaining portion is placed in tanks at the site.  But the storage capacity could eventually run short, raising the possibility that TEPCO may resort to dumping low—-level radioactive water in the Pacific Ocean, a plan the utility said it was considering in December but gave up due to opposition from the fishing industry.

Since mid-June it is estimated that the cesium activity has increased by about 15 percent due to fuel decay products.

One facility for removing cesium was created by the California-based Kurion Inc, whose equipment us so big it could only be transported by a special Russian aircraft. The Kurion equipment has had issues with pumps, and leaks, which have caused the entire water treatment system to shutdown.  Another was made by France’s AREVA, which came up with an intricate system of pipes and valves that took 50 welders more than a month to put together, TEPCO said. The AREVA system isn’t being used now.

TEPCO shut down the Kurion and AREVA systems in September, after water that had been processed by the Kurion system, was found more radioactive after being run through the AREVA system. It is possible that highly radioactive sludge in AREVA’s system leaked. TEPCO has placed most of it’s hope in Toshiba Corp.’s SARRY system, Toshiba and support companies deploy 140 workers to operate and monitor the water-processing system, and another 20 to oversee pumping and circulation, through a 2.5-mile line of pressure-resistant hoses.

Tepco has the capacity to store 165,000 tons of contaminated water, said Katsuhiko Iwaki, deputy manager of the Fukushima Daiichi stabilization center. About 125,000 tons of water already is being stored. The company plans to expand capacity to about 205,000 tons, he said.

Kurion, the US  nuclear cleanup technology corporation, reported progress of its cleanup efforts at the Fukushima Daiichi disaster. The firm said that since it began processing the highly contaminated water at the plant, it has processed more than 137,340 Metric Tons (MT)(36 million gallons) of waste water and was responsible for removal of approximately 3.5 x 10(17) Becquerel (9.4 million curies) of cesium. The system started operation June 17, and Kurion said that the figure is approximately 70 percent of the radioactivity removed from the doomed nuclear plant.

Ex-SKF, a Japanese blog has been tracking the progress of different decontamination and desalination equipment at Fukushima Daiichi.  His coverage in the past year has added a lot of little-known details about the decontamination systems,  adding;

According to TEPCO, as of December 20, the total number of used cesium towers (Kurion and Toshiba) was 316, with the storage capacity of 393 , and the number of used cesium towers increased by 4 from the previous week. Even at this slow rate, the storage would have been full in 19 weeks or about 5 months.

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. 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.

Snippets that I pick up from Twitter and some Japanese magazine articles interviewing anonymous high-level managers at Fukushima I Nuke Plant indicate that the workers have almost given up on having Kurion and AREVA units run without frequent problems, and are pinning their hope on Toshiba’s SARRY.

 

The water problem isn’t one that will go away soon: TEPCO has to keep constantly smothering the nuclear reactors with water for cooling, until the melted nuclear fuel is removed. TEPCO will not be able to fix all of the leaks, until the fuel is removed, which means that for now, no alternative methods will stem the contaminated water from continuing to pile up.  Officials estimate it will take six years to plug the leaks and 25 to remove the fuel.

The timeline for removing the fuel is generally based on the half-life of the remaining elements. Cesium-134 has a half life of 2 years. For all intents and purposes it will be much less radioactive, in about 10 half lives. Nuclear decommissioning doesn’t have to always take 30 years, if you wait 30 years to start it is an easier job.  Aside from laws banning the deliberate dumping of radioactive substances into the oceans, Japan is a fish eating nation. Dumping the radioactive water at sea will only result in ingestion of radioactive fish by the greater population.

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