TEPCO just released data on radioactivity in sea water that shows that the amount of radioactivity entering sea water is way up from levels reported 2 weeks ago. Moreover, short lived I-131 levels continue to stay high at levels that are very hard to explain if it is not being produced by continued criticality of some part of the apparently melted down core. TEPCO continues to pour water over the reactor vessel and it continues to leak away. It's clear that some of that water continues to flow into the ocean.
After temporary declines, I-131 levels in entering the ocean near Fukushima unit 2 returned to levels seen one month ago. Moreover, the ratio of I to Cs has gone up, not down. Since I-131 has a half life of 8 days, levels should have dropped by almost 4 half lives, over a factor of ten by radioactive decay alone. Continued high levels of I-131 are an indicator of possible continued criticality of part of the damaged core. Elevated levels of I-135 with a half life of 8 hours would be proof positive of criticality but it has not ever been reported by TEPCO. (diarist's figure notation)
Radioactive materials in the ocean near the Fukushima Daiichi nuclear power plant rose to 3,300 times the legal limit on Sunday.Tokyo Electric Power Company says it measured 200 becquerels of cesium-134 per cubic centimeter on Sunday morning near the water intake of the No. 3 reactor. The level was higher than on the previous day, when it was 2,300 times the legal limit.
220 becquerels of cesium-137 per cubic centimeter was also detected. At 2,400 times the legal limit, the level exceeded the one found the day before
Tokyo Electric Power Company, or TEPCO, estimates that there is about 22,000 tons of highly radioactive water in thereactor's turbine building and in a connecting tunnel.The utility says the water in the basement of the turbine building was about 1.4 meters high as of Monday morning, a rise of more than 20 centimeters over the past 2 weeks. Part of the water leaked into the sea last week.
TEPCO now admits that units 1, 2 and 3 may be all leaking after have all melt downs. They admit that the some of the water is entering the ocean. They plan to change their approach to cooling the damaged reactors but they have not yet figured out how to do it.
It says it is now considering pumping water out of the containment vessels and circulating it back into the reactors after chilling it with heat exchangers.
Another method under study is pumping water from the basement and sending it back to the reactors after radioactive substances have been removed.
Never the less, TEPCO claims they will achieve a cold shut down in 6 to 9 months. TEPCO has not explained how it will possible to shut down a melted down core. Because the reactor units are so close to sea level in a humid environment, if the melted "corium" has penetrated the reactor vessel, the corium would be involved with groundwater continuously flowing to the ocean. Even a concrete sarcophagus may not be able to stop the release of radioactivity to the ocean. Moreover, stopping intermittent local criticality events may be very difficult in this environment.