More than two years into the triple-meltdown crisis at the Fukushima No. 1 power plant, workers continue to wage a desperate battle to keep the stricken reactors cool while trying to contain the 400 tons of radioactive water produced by the process each day.
Tokyo Electric Power Co. must decommission the three reactors, but the water is thwarting the effort. The decommissioning, if it ever starts, will take decades.
Here are some questions and answers on the encroaching problem and its implications for public health and the environment:
Why is radioactive water accumulating and how much is there?
As of May 7, Tepco had routed 290,000 tons of radioactive water into some 940 huge tanks at the complex, but 94,500 tons remain inside the basement floors of the reactor buildings and other facilities.
Tepco must perpetually pour water over the melted cores of reactors 1, 2, and 3 via makeshift systems to prevent the fuel from melting and burning again.
But the cores’ containment vessels were damaged by the meltdowns, allowing the highly radioactive coolant water to leak and flow into the basements. The dangerous radiation levels have prevented workers from getting close enough to fully assess the damage, let alone start the decommissioning process.
Compounding the problem is some 400 tons of groundwater that is also entering the basements of the tsunami- and explosion-damaged buildings, mixing with the leaking coolant water.
Tepco has been operating a water-recycling system to drain the basements that is supposed to extract cesium before recirculating the water back to the reactors. But the added inflow of the groundwater is exacerbating the threat.
In response, all Tepco has been able to do is build more storage tanks.
What problems will the water eventually pose?
Tepco says there is a limit to how many tanks the complex can accommodate before the site runs out of storage space.
Tepco said it can boost storage capacity from 430,000 tons from this year to 700,000 tons by mid-2015 by clearing a forest and other space in the compound. The move is expected to buy them about three years’ time.
Tepco is proposing some of the water be dumped into the sea after processing it to remove most, but not all, radioactive isotopes. Local fishermen strongly oppose the plan as it will taint the image of their produce.
Previous discharges into the Pacific have effectively contaminated the sea. Failure to store it means it will probably flood the whole compound and end up in the ocean anyway.
Neither Tepco nor government experts have come up with any other viable solutions.
Will the processed water pose health or environmental risks?
According to Tepco, the processed water could theoretically be safe, but fishermen and consumers disagree.
Tepco has been using an advanced liquid processing system made by Toshiba Corp. to decontaminate the coolant water.
ALPS can bring the density of 62 main radioactive substances below detectable levels, including strontium and plutonium.
Tritium is the exception, however. Tepco says the tritium level in the contaminated water is between 1 million and 5 million becquerels per liter. The legal limit is 60,000.
Tepco thus wants to dilute the water to bring the tritium density below the legal limit by dumping it into the sea. It has promised not to dump any without gaining the nod of local fishermen first.
Tritium, a common hazard at nuclear plants, can increase the risk of cancer if ingested and has a half life of 12.3 years. It is about 1,000th as radioactive as cesium-134 and -137.
Are there other concerns over water-related facilities?
Tepco revealed on April 5 that radioactive water stored in makeshift cisterns with coamings and surface covers were leaking into the soil.
This forced the utility to stop using the reservoirs, which were basically lined trenches with lids, and pump some 24,000 tons of tainted water out of them and into aboveground tanks.
The transfer is expected to be finished later this month.
Experts also are worried about the integrity of the 940 aboveground tanks built as of April 1, since 280 of them are considered “temporary” because they can only be used for up to five years. These are made of steel plates bolted together with waterproof packing to seal the seams, unlike welded steel tanks that offer a longer-term solution.
Tepco will need to start repairing or replacing the temporary tanks in spring 2016.
Tepco has dug 12 wells to intercept groundwater before it seeps into the reactor building basements. Will this work?
Yes, but only to a certain extent.
The wells were dug on the mountainside above the damaged buildings. Tepco plans to pump up as much groundwater as possible to keep it from entering the basements as it heads to the sea.
But Tepco estimates the wells can only pump up 100 of the 400 tons leaking into the buildings every day.
Tepco was going to release the well water into the sea because its radioactivity is much lower than the safety standards for drinking water set by the World Health Organization.
It suspended the plan on May 13 after the local fisheries association vetoed the idea, fearing any further discharge would only worsen the already marred image of local seafood.
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