Several decades ago, an American with an
active imagination and a twisted sense of
geography coined the term "China syndrome" to
denote the worst-case scenario for an accident in
a nuclear power plant.
The phrase,
popularized by a 1979 movie with the same name,
refers to the possibility that nuclear fuel turned
into red-hot lava could melt its way through the
reactor bottom and the Earth's crust, "all the way
down to China". Presumably, and much to the
consternation of any geographer past the
middle-school level, China would find itself on
the opposite side of the Earth from the United
States in this science-fiction setup.
Even
though any area "on the opposite side of the
Earth" from Japan is quite safe from the danger of
molten uranium, plutonium and fission products
from the Fukushima Daiichi plant erupting in
a volcano, the nuclear
installation seems to be going through a limited
version of the China syndrome since it was damaged
in an the aftermath of the massive earthquake and
tsunami of March 11. Some molten fuel may well
have escaped the reactor vessels through holes
created by the heat, the hydrogen explosions which
happened days into the crisis, or both. More
details are expected in the coming days and months
as an intricate tale unfolds of unforeseen
disaster, human error, suspicious cover-ups and
gross exploitation of underpaid workers at the
plant.
Last week, the plant's operator
TEPCO announced that attempts to recycle highly
radioactive water pumped as a coolant into unit 1
had failed because the water levels were too low.
[1] The water simply kept disappearing - and
having in mind that tens of thousands of tones of
such water accumulated in the reactor basements,
it is not difficult to guess where.
More
recently, TEPCO admitted that most of the nuclear
fuel rods had melted into a pile at the bottom of
reactor 1, and that reactors 2 and 3 faced similar
problems. [2] Engineers and government officials
started for the first time to talk openly about
holes in the reactor vessels.
In the most
scary realistic scenario, the molten fuel could
restart the nuclear chain reaction - in physics
jargon, become "critical" - and start pumping out
heat and radioactive isotopes with renewed force.
The chain reaction was halted with the help of
control rods and various other "moderators"
immediately after the 9.0 earthquake that
triggered the crisis, and all that remained was
heat generated by decay (mostly beta decay, as a
Duke University nuclear physicist explained to
Asia Times Online last month [3]). This was
sufficient to facilitate the meltdown and the
hydrogen explosions that happened subsequently.
Once the fuel melts fully, however, the
control rods can no longer prevent the chain
reaction efficiently, and there is a danger that
the latter might resume. Evidence of such an
occurrence is inconclusive and consists mostly of
the alleged presence of isotopes with very short
half-lives weeks after the shutdown of the
reactors. [4] Informed speculation suggests that
this didn't happen, or only happened briefly and
in a limited way. As Geoff Brumfiel writes in
Nature,
There's some reason to think that
this "China syndrome", as it is informally
known, didn't happen. Nuclear engineers I've
spoken to say that reactors like unit 1 are
finicky beasts. Their fuel needs to be carefully
configured to work, and they won't restart if
the stuff is just a gloop on the bottom of the
vessel. In addition, workers injected boric acid
into the reactor just before the restart. Boron
is a neutron absorber and would spoil any
nuclear reactions. Moreover, temperature sensors
at the bottom of the reactor vessel are
continuing to function, suggesting it wasn't
completely destroyed. [5]
The slight
confusion in terms - Brumfiel uses "China
syndrome" more narrowly to denote the fuel's
becoming critical again, while others use it more
broadly for situations where the fuel melts
through the steel container - reflects the
informal nature of the phrase.
His
argument is supported by data showing that the
temperature inside the reactors is around 100
degrees Celsius, close to the desired "cold
shutdown" levels when active cooling would no
longer be necessary (still, it may be months
before a cold shutdown is reliably attained). Both
Brumfiel and other experts, however, admit that
temporary flashes of renewed criticality may have
occurred and may still be liable to occur.
There are numerous other interesting
technicalities and speculations involved in the
China syndrome scenario, and Richard Muller's
overview, published on the website of the Lawrence
Berkley National Laboratory, is quite instructive.
The most significant and least controversial
bottom line is that escaped fuel would complicate
enormously clean-up efforts, expose workers to
unpredictable flashes of intense radioactivity,
and threaten to contaminate the air, water and
soil around the plant further with massive amounts
of dangerous isotopes.
It is hard to
overstate the significance of the latter - the
danger is so real that newer-generation nuclear
plants are designed with expensive special
radiation traps to capture molten nuclear fuel. In
an unfavorable sequence of events (for example, a
powerful aftershock followed by a new tsunami), an
area of tens of thousands of square kilometers
could turn into a nuclear wasteland.
The
damage to the ocean ecosystem, which has already
absorbed large radioactive emissions, would be
enormous. This new danger comes on top of the
risks associated with the presence of hundreds of
tons of spent nuclear fuel and highly contaminated
water at the plant. As a side note illustrating
the precarious conditions of storage, TEPCO just
announced that it had purchased a "mega float"
where it intends to put some of the water. [6]
Despite the setbacks, the operator has
continued to insist that it would stick to its
time-table of six to nine months to stabilize the
plant. [7] How exactly it intends to do that is
uncertain, and both it and the Japanese government
are coming under increasing criticism for a lack
of transparency and a coherent strategy in
handling the situation.
Late last month,
one of the top nuclear advisers to the government,
Professor Toshiso Kosako, resigned in protest of
what he termed "impromptu policy decisions, like
playing a whack-a-mole game, ignoring proper
procedures".
A newly-released set of
documents and logs from the early hours and days
of the crisis took the government "off-guard" [8]
by suggesting that a "worker error may have led to
meltdown". A TEPCO spokesman told the Japan Times
on Tuesday that a worker may have shut down a
critical safety mechanism soon after the
earthquake in an erroneous interpretation of the
safety procedures. [9] According to these
documents, the meltdown at unit 1 happened within
16 hours of the earthquake, and the hydrogen
explosion at the unit the next day hampered
additionally the efforts to restore the power
supply to the entire plant.
The documents,
some analysts point out, could serve to exonerate
the American company General Electric, which
manufactured the reactors, from its share of the
blame. It looks, therefore, as if the blame-game
is intensifying. If the reports of human error are
confirmed, this would bring to the fore
discussions about the state of preparedness of the
plant operators for a crisis.
Both TEPCO
and the government have promised compensation to
those most gravely affected by the crisis, but to
many this is too little, too late.
As Asia
Times Online reported this month, the authorities
are also taking heat for employing underpaid
contract workers for the cleanup effort, without
providing them with protective gear and adequate
information about the risks. [10] According to a
recent report in Japan Today, a man in his sixties
was lured to work in the plant with a spurious job
ad. [11]
The alleged cover-ups mean that
as workers slowly and cautiously make their way
into the reactors - this is how the complete
meltdown at unit 1 was confirmed - more grave
reports about the true situation at the plant can
be expected.
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