Wednesday, August 31, 2016

Fukushima's "Hail Mary"

credit: NYT
It has been some time since US Person wrote about the Fukushima Daiichi disaster, {17.05.11} but that certainly does not mean the crisis is fully under control.  After the triple meltdown caused by a large earthquake and subsequent tsunami five years ago, Japan's government still struggles to contain the threat of huge amounts of radioactive wastewater reaching the ocean or permeating into the earth.  The reactor site is now covered with a thousand 95 foot tall tanks containing 800 tons of radioactive waste water. [photo]  The chosen solution to the problem is a high-tech one that is costing the government $320 million.  A network of underground pipes will freeze the earth around the reactors to prevent leaks and form a dam to stop groundwater from reaching the radioactive hulks.
The alleged solution seems appropriate for a country that has completely embraced technological wizardry as a cultural modus operandi.  But the so-called "ice wall" has been criticized as an overly complex project that might not even work.  Those concerns were justified when plant owner TEPCo switched on a portion of the barrier four months ago and the earth around the pipes has yet to freeze solid.  Since the wall is electrically powered it is potentially as vulnerable as the reactors proved to a forty-five foot tsunami that caused a complete loss of station power.  Super-cooled brine circulates in the pipes that are intended to freeze the earth solid for a foot and half around each pipe. The wall consists of over 1500 pipes that are cooled by thirteen giant refrigerators that consume enough electric energy to light 13,000 Japanese homes every year.

Groundwater infiltration is a difficult problem at Fukushima because of local geology and how the company cut into bedrock in order to site the plant close to the sea, its source of cooling water.  The bedrock is permeable and collects snow and rain runoff from the nearby Abukuma Mountians.  Reactor explosions have apparently cracked the containment building foundations, allowing forty thousand gallons of water a day to infiltrate and become contaminated.  The flooding prevents engineers from locating massive lumps of melted fuel rods and their assemblies believed to have penetrated steel reactor floors when it was super hot from uncontrolled fission.  Five robots have been lost searching the highly radioactive ruins.

Critics of the construction call it a "flashy" solution to a problem that TEPCo underestimated from the beginning of the disaster.  The technique of freezing the earth has been used before in mines and tunnels, but never on this scale.  Buried obstacles make the ice wall more of sieve than a barrier say critics, so this massive technical virtuosity may be more of a "hail Mary play" than a real fix.