The operator of Japan’s damaged Fukushima Daiichi nuclear-power plant, Tokyo Electric Power Co. (TEPCO), has issued a clarification regarding an earlier news release concerning efforts to freeze highly radioactive water at the site.
The original June 16 bulletin detailed “difficulties that were encountered with an effort to freeze standing water” as part of TEPCO’s Fukushima Daiichi decommissioning project, which is expected to take decades.
Those problems amounted to a failure to freeze approximately 11,000 tonnes of contaminated standing water in trenches under two reactor buildings, a project that TEPCO started on April 28 this year.
Solution cooled to -30 Celsius
The freezing process, essentially the same as that being employed in a much more ambitious and recently started “ice wall” project, involves piping in a solution of calcium chloride cooled to -30 ° C.
On June 18, however—after international media outlets confused this news with the later and ongoing year-long effort to build the 1.4-kilometre-long underground ice wall around four damaged reactors (to prevent incoming groundwater from mixing with the already contaminated cooling water underneath the facilities)—TEPCO offered a clarification.
“This has nothing to do with the “ice wall (landside impermeable wall with frozen soil)” which is constructed by freezing the soil surrounding pipes that carry circulating refrigerant,” the June 18 release stated.
Operator blames moving water
TEPCO blamed running water under the No. 2 reactor building and uneven water levels for preventing the radioactive water from freezing.
“We are behind schedule but have already taken additional measures, including putting in more pipes, so that we can remove contaminated water from the trench starting next month,” Agence France-Presse quoted a TEPCO spokesperson as saying on June 17.
Both projects are being undertaken by the same contractor, Kajima Corp.
Contaminated standing water results from TEPCO pumping enormous amounts of cooling water over the reactors damaged in the March 2011 earthquake and tsunami in northeastern Japan.
New water constantly coming in to site
Compounding that problem—which requires pumping out, treating, and storing the highly radioactive water on-site—is the incoming groundwater that constantly moves through the site on its way to the Pacific Ocean from surrounding higher ground.
TEPCO has said that it hopes to remove the standing water underneath the reactor buildings by the end of fiscal year 2014. The ice wall to deflect additional groundwater is expected to take about a year to complete.
At present there are more than 1,000 storage tanks on the contaminated site holding both treated and untreated water. TEPCO also recently undertook a water "bypass" program to pump uncontaminated water into the Pacific before it mixed with standing radioactive coolant water.
Many previous dumps of contaminated water in ocean
The company has also dumped "treated" water into the ocean and has admitted to several tank leaks, pump or equipment breakdowns, and breaches of containment walls in the past two years that have resulted in the release of hundreds of tonnes of radioactive water into the nearby saltwater.
In a separate June 18 report on the “situation of storage and treatment of accumulated water including highly concentrated radioactive materials at Fukushima Daiichi nuclear power station”, TEPCO stated that its forecasts are “subject to change” depending on the continuing operation of its radioactive-material treatment instruments and future rainfall.