APR: your source for nuclear news and analysis since April 16, 2010

Tuesday, April 5, 2011

Early Tuesday Fukushima Daiichi update

Contamination (by iodine 131) at seven and a half million times the allowed limit has been detected off the Fukushima Daiichi plant. Apparently the reading at the present time is down to two thirds what it was at the point mentioned above, the peak level of the accident so far.

As mentioned here, TEPCO is thinking now that there are other sources than the now-well-known cable pit admitting contaminated water to sea, and it plans to inject sodium silicate into the sand and gravel zone beneath the pipe and cable tunnels that run from the No. 2 plant turbine building to sea. This is intended to absorb water, expand and seal off the area. Of course, this will simply mean more water to deal with somewhere else and it's becoming vital that TEPCO get recirculating cooling established at these plants, again as said a number of times here before.

There is an estimate floating around which originated with NISA that there might be 60,000 tons of additional contaminated water on site to be dealt with. Much effort is being put into acquisition of the 'mega float,' and a number of new auxiliary water tanks to supplement the water facility and two US Navy barges already present. And of course, the company intends to use the ROSATOM barge to clean a large amount of the less contaminated water.

At No. 1 plant, temperatures continue to slowly decrease.

We're getting better information that our earlier suspicion of wide derangement of physical structure outside the plant (labyrinthine concrete cracking) might be right since TEPCO now says that the pumping of radioactive water to the No. 4 plant is filling up the No. 3 plant pipe tunnel. This filling of No. 4 plant was stopped, and the level in No. 3 plant's tunnel stopped increasing.

Part of TEPCO's most recent press statement indicates that groundwater leakage INTO the multiple reactor plants on site is now enough that it's becoming worried that equipment for proper cooling of the reactor plants might become submerged. This would mean pumps, primarily, and their power panels that are mounted low down in the turbine buildings -- condensate pumps and any temporary pumps and arrangements TEPCO has put in.

To be clear, it appears that the very high level radioactive iodine found in the water at 7.5 million times the limit is not thought to have anything to do with the discharge of the 10,000 tons of water from the central radwaste facility on the site that's ongoing, or the 1500 tons from plants but rather from groundwater and tunnel leakage due to No. 2 plant's condition. Details we have right now don't show that the water at either the radwaste facility or No. 5 and No. 6 plant drain pits is "hot" enough to cause this spike. This distinction should be kept in mind as the panicked big media reports on this new peak contamination today.

5:20 AM Eastern Tuesday 4/5

UPDATE: The reading of 7.5 million times the limit for I-131 was taken very close to the plant.. possibly inside the breakwater. The readings drop dramatically with distance from the plant and are acceptable even if slightly above the limit at 15 KM range according to the most recent report here at about 6:05 AM Eastern 4/5. Note that this is only halfway through the exclusion radius of 30 KM which extends out to sea as well as inland.

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