From Time Magazine’s Ecocentric Blog – May 16, 2011

by Eben Harrell

The China Syndrome refers to a scenario in which a molten nuclear
reactor core could could fission its way through its containment vessel,
melt through the basement of the power plant and down into the earth.
While a molten reactor core wouldn’t burn “all the way through to China”
it could enter the soil and water table and cause huge contamination in
the crops and drinking water around the power plant. It’s a nightmare
scenario,the stuff of movies. And it might just have happened at Fukushima.

Last week, plant operator Tepco sent engineers in to recalibrate
water level gauges in reactor number 1. They made an alarming discovery:
virtually all the fuel in the core had melted down. That means that the
zirconium alloy tubes that hold the uranium fuel and the fuel itself
lies in a clump—either at the bottom of the pressure vessel, or in the
basement below or possibly even outside the containment building.
Engineers don’t know for sure, though current temperature readings
suggest that fission inside the reactor core has definitely ceased for
good (i.e. there will be no further melting).

Anecdotal evidence doesn’t bode well for how far the fuel melted:
Tepco has been pumping thousands of tons of water onto reactor 1 to try
to cool it—yet the water level in the containment vessel is too low to
run an emergency cooling system. That means the water is escaping
somewhere on a course cut by molten fuel–probably into the basement of
the reactor building, though it’s also possible it melted through
everything into the earth.

Many experts say a full-blown China syndrome is unlikely in large
part because the fuel from the type of reactors at Fukushima is designed
in such a way that it probably won’t sustain “recriticality” once
meltdown occurs. What’s more,  boron, which slows nuclear reactions, was
pumped into the cooling water of the reactor after the initial accident
to prevent the core from going “critical” again.

But assuming a worst case scenario hasn’t occurred, having so much
highly radioactive water sloshing around the basement is going to make
cleanup even more difficult. Tepco says it will come up with a new plan
to stabilize the reactor by Tuesday—and their main task will be to find a
way to suck up the water and store it while simultaneously ensuring the
reactor core remains cool. It’s unclear how this will be achieved, but
according to press reports, a giant water-storage barge – a Megafloat –
has been dispatched to Fukushima as a possible storage site for
contaminated water, and will arrive at the end of the month.

Tepco also said that it has started preparatory work for the
construction of a cover for unit 1’s reactor building, which had its
roof blown off by a hydrogen explosion on March 12.  The cover is to be
built as a temporary measure to prevent the release of radioactive
substances until further measures can be put in place, Nature News reported.

Meanwhile, around 5,000 residents in two towns, Kawamata and Iitate,
some 30 km from the power plant—well beyond the the 20 km exclusion
zone–were evacuated on Monday. More evacuations are expected in the
coming days as Tepco continues to struggle with the crisis. Around 
3,400 cows, 31,500 pigs and 630,000 chickens will soon be slaughtered
inside the Fukushima exclusion zone as feeding them has proven to be
impossible.

It’s difficult to say for sure just how bad things are at the plant
itself—high radioactive levels mean that engineers can’t get close to
the reactor cores themselves and can only make inferences, deductions
and guesses about the extent of the damage. As Alexis Madrigal of the Atlantic has
pointed out, we’ve faced this uncertainty—and troubling surprises—
before. Eight months after the Three Mile Island accident, “an Oak Ridge
National Laboratory scientist declared, ‘Little, if any, fuel melting
occurred, even though the reactor core was uncovered. The safety systems
functioned reliably.’ A few years later, robotic sorties into the area
revealed that half the core — not ‘little, if any’ — had melted down.”

I and TIME’s Kiev-based stringer recently published a piece for TIME from
Chernobyl in Ukraine, where clean-up efforts continue a full 25 years
after the accident. Whatever the end game at Fukushima, get your head
around this, folks: it is going to be a huge mess for a long time yet.