As the levels of radionuclides in groundwater under the Fukushima Daiichi nuclear plants continue to increase dramatically, the United Nations nuclear agency proposes that the massive quantities of contaminated water stored at the facility be dumped into the sea.
The March, 2011 earthquake, tidal wave, and subsequent triple meltdown of Fukushima reactors 1, 2, and 3 have presented Tokyo Electric Power Company (TEPCO) with a seemingly insoluble dilemma. The cores of the reactors must be kept cool, requiring large quantities of water. But the containment vessels have been breached - in fact, no one is even sure where, exactly, the cores are. Massive quantities of water are pumped into the facilities to keep them cool, but the water just pours right back out again, highly contaminated.
Some of this contaminated water is recaptured, and about a third that wasn't reused to cool the reactors (after removing the cesium) is stored in an ever-growing tank farm. In addition to the 400,000 cubic meters of water stored in nearly a thousand tanks, by late last year over 100,000 cubic meters of contaminated water was estimated to have accumulated inside the facilities, according to the U.N.'s International Atomic Energy Agency (IAEA). And a substantial quantity was simply seeping into the ground, with monitoring wells showing ever increasing amounts of radioactivity in the groundwater under the plants.
According to Russia Today, on February 13, TEPCO reported a record level of cesium - 37,000 becquerels of cesium-134 and 93,000 becquerels of cesium-137 per liter - in a groundwater monitoring well near plant 2, about fifty meters from the coast. This combined reading of 120,000 becquerels is in sharp contrast to a reading made in the same well the previous day, with a combined reading of 76,000 becquerels per liter.
This report follows on the heels of another report from Russia Today, that in mid-January a record high level of beta rays released from radioactive strontium-90 was detected, apparently in the same well, of 2.7 million becquerels per liter. And on February 8, TEPCO revised its reading made in a well near plant 1 in July to 5 million becquerels of strontium per liter – both a record, and over five times higher than the original reading of 900,000 becquerels per liter. Apparently every measurement made by TEPCO was off by a similar magnitude.
So, what to do about the intractable problem of ever increasing volumes of highly contaminated water? Clearly the current regime of building ever more tanks is unsustainable. In an IAEA report the agency reviews the current regime for dealing with the water, including the Advanced Liquid Processing System (ALPS) which, according to TEPCO, is able to remove 58 radionuclides to below detectable levels out of the 62 "target" radionuclides. Four radionuclides, however, (Co-60, Ru-106, Sb-125, and I-129), while reduced, are not eliminated. In addition there is the issue of tritium, present at levels of "several thousand becquerel per CC", or several million becquerels per liter. There is no feasible way to remove the tritium from the water.
So, what to do? "In the opinion of the IAEA team, a path forward for further management of the treated tritium-bearing water is necessary in order to reach a sustainable solution to the contaminated water problem. This would require careful consideration of all options, including dilution and controlled discharge to the ocean..."
The report goes on to provide "Advisory point 5:
The IAEA team believes it is necessary to find a sustainable solution to the problem of
managing contaminated water at TEPCO’s Fukushima Daiichi NPS. This would require
considering all options, including the possible resumption of controlled discharges to the sea.
TEPCO is advised to perform an assessment of the potential radiological impact to the
population and the environment arising from the release of water containing tritium and any other residual radionuclides to the sea..."
In other words, dump it. No other option was suggested. Dilution is the solution to radioactive pollution.