Engineers at a tsunami-damaged nuclear plant in Japan have
resorted to pumping contaminated water into the sea in a bid to free space to
store dangerously radioactive water that is delaying vital repairs to one of
the reactors.
On Monday, Japanese authorities told news organizations that
Tokyo Electric Power Co. has begun a five-day effort to pump out 10,000 tons of
water that the March 11 tsunami deposited in a building used for waste
disposal. The Japanese government also approved plans to pump a further 1,500
tons of groundwater from the vicinity of units 5 and 6 in an effort to prevent damage
to critical electrical systems at those reactors.
While TEPCO said
daily consumption of fish exposed to the discharged water would result in 0.6 millisieverts of radiation over a year (roughly 1/4 of an average person's exposure from background radiation yearly), radiation levels of water at unit 2
have been measured at 1,000 millisieverts per hour. Water in tunnels near the
unit also contains 10,000 times the legal limit of radioactive iodine.
Isolating that water in the newly available storage areas before it leaks into
the sea has become TEPCO’s top priority at the plant. Over the weekend, a
crack was found in a pit containing the water, heightening fears that it might
leak into the ocean, although it was unclear Monday if efforts to fix the leak
have been successful. Water in the basement of unit 2 also presents dose levels
that make further work to restore normal core cooling functions at the reactor
impractical until the water is removed.
Earlier, engineers had considered water storage methods that
included the use of barges or a floating pier, but it was decided that those
solutions would take too long to implement. Nikkei reported that the
intentionally released water contains iodine-131 at levels 100 times the legal
limit and cesium isotopes at levels 50 to 70 times the legal limit.
So far, radioactive elements and elevated radiation readings
in the sea and in soil samples in towns near the plant have caused no noticeable
health effects. On Monday, NISA reported that 946 children underwent thyroid
exams in a town near the plant, and none showed any health effects from the
accident.