Just as reactors number 1 and number 3 of
the devastated Fukushima nuclear power plant in
Japan - both of which had earlier experienced
blasts that severely damaged their outer
protective shells - appeared to be more or less
out of the woods by late Monday, fresh disasters
struck.
A third, even more severe
explosion occurred at reactor number 2 a little
after 6 am on Tuesday, breaching the crucial inner
steel container that houses the reactor, forcing
the evacuation of emergency workers from the plant
and prompting fears of a nuclear "catastrophe".
Meanwhile, a fire broke out in reactor number 4 as
well, reportedly releasing large amounts of
radioactive materials into the environment.
Within about two hours of these
developments, radiation levels
around the plant shot up to
the unprecedented 8,217 micro sieverts per hour.
This is more than eight times the maximum legal
dose a person can be exposed to in an entire year.
People living 20 to 30 kilometers away were
ordered to stay indoors; those within a
20-kilometer radius of the plant had already been
evacuated following the previous blasts. According
to the Kyodo news agency, "minute levels'' of
radiation were detected even in the capital Tokyo,
260 kilometers from the disaster.
Japanese
authorities attempted to allay fears even as they
appeared increasingly helpless to control the
situation brought on by the magnitude 9 earthquake
that struck Japan on March 11. "A worrisome
situation remains but I hope to take the lead in
overcoming this crisis," Japanese Prime Minister
Naoto Kan said on Tuesday. Inside sources,
however, indicate that the characteristically calm
reaction of the government conceals a state of
utter distress and chaos. Western "industry
executives", quoted by The New York Times on
Tuesday, said that their Japanese colleagues were
"basically in a full-scale panic".
Experts
disagree about the severity of the disaster. Many
have attempted to compare it to the two most
famous nuclear meltdowns in history, those at
Chernobyl in Ukraine in 1986 and in Three Mile
Island in the United States in 1979. At this
point, however, such comparisons appear highly
speculative. On the International Nuclear and
Radiological Events Scale, Chernobyl, which sent
radioactive dust over much of Europe, is rated at
7, the most severe ("major accident''), while
Three Mile Island, which also featured a meltdown
but did not release significant amounts of
radiation into the environment, is rated 5
("accident with wider consequences'').
On
Saturday, the Japanese Nuclear Safety Agency rated
the accident at Fukushima at 4 on the same scale,
but now this assessment appears due for major
revision. According to a Monday assessment by the
head of France’s Nuclear Safety Authority,
Andre-Claude Lacoste, the Fukushima crisis is
"worse than Three Mile Island but not as great as
Chernobyl".
Even the favorable comparison
with Chernobyl is disputed. On the one hand, many
have pointed out that the Japanese reactors shut
down successfully immediately prior to the
earthquake on Friday, something that precludes a
disaster on the scale of Chernobyl. "There’s no
comparison with Chernobyl,'' Israeli professor
Arye Dubi, of the Department of Nuclear
Engineering at Ben-Gurion University, said on
Monday.
"Chernobyl was a 3,200-megawatt
reactor which exploded while working at peak
capacity. The three reactors in Japan are around
500 megawatts each and they were immediately and
successfully turned off with the first tremors of
the earthquake. Once it turns off, its output is
reduced to about 5% or 25 megawatts.''
His
assessment is backed by that of James Stubbins, a
nuclear energy expert at the University of
Illinois, who claimed, "The likelihood there will
be a huge fire like at Chernobyl or a major
environmental release like at Chernobyl, I think
that's basically impossible."
This may be
true from the point of view of nuclear physics,
which concerns itself primarily with the amount of
energy released, but it is not necessarily true
from the perspective of radiological epidemiology,
which takes into account a wider array of factors
such as wind patterns, relative toxicity of the
leaked elements, and population densities in the
surrounding areas. On Saturday, even before the
latest developments, Hebrew University of
Jerusalem Professor Menachem Luria, an expert on
air quality and poisoning, issued a stern
prediction.
"This is very worrying,'' he
said in an interview with the Israeli Channel 2.
"There is no doubt that we have not seen anything
like this in years, perhaps ever since nuclear
experiments were conducted in the atmosphere in
the 1950s. From what we can gather, this disaster
is even more dangerous than Chernobyl, both from
the standpoint of the population's exposure to
radioactive material and the spread of radioactive
contamination in the area."
Fukushima
poses unique challenges, not least of which is
that never before have so many nuclear reactors
experienced failures at the same time. To add to
the complexity of the situation, one of the
afflicted reactors - number 3 - is loaded with a
controversial mix of plutonium and uranium known
as pluthermal MOX (mixed oxide fuel). It is
considered highly toxic, since inhaling even small
amounts of plutonium can be lethal.
In
order to clear out some of the confusion, it is
important to understand, in broad terms, what
happens during a nuclear meltdown - for there is
no doubt we are dealing with at least partial
nuclear meltdown at the three reactors. Even after
the process of nuclear fission has largely
stopped, radioactive decay in the fuel continues
to produce significant amounts of heat which, in
the absence of continued cooling, can melt through
several levels of protection inherent in reactors
such as those in Fukushima.
This is
currently happening at the plant, where cooling
systems failed in the wake of the devastating
earthquake and tsunami on Friday. The most
striking example of this dynamic is the fire in
reactor number 4, which ignited and released
substantial amounts of radiation despite having
been turned off months ago. According to reports,
there was only spent fuel there, but once the
water that was in it drained for unknown reasons,
the spent fuel caught on fire.
All four
afflicted units at Fukushima are second-generation
boiling water reactors, built roughly 40 years
ago, and contemporary to the reactors at Chernobyl
and Three Mile Island. Over time, their safety
mechanisms had been upgraded, but even so reactor
number 1 had been scheduled for decommissioning
later this year. Despite the improvements, they
experienced multiple mechanical failures during
the crisis.
In very simple terms, boiling
water reactors can be compared to a
nuclear-powered steam engine with multiple levels
of protection. The fuel consists of ceramic
uranium pellets covered in metal and immersed in
light water. The heat generated by nuclear fission
turns the water into steam, which then powers the
electricity-generating turbines before being
cooled down by a separate second cycle of cold sea
water and returned to the reactor.
The
cooling process keeps the temperature inside the
reactor at around 550 degrees Fahrenheit (290
degrees Celsius). Additionally, the reactor itself
is encased in a special steel container with
numerous pressure valves. In the case of all
modern reactors, the design features an additional
external shell of reinforced concrete that is
meant to block the release of radioactive
substances in a worst-case scenario.
Should the circulation system fail - as
happened in Fukushima - the water inside the
reactor evaporates rapidly, and the temperature of
the fuel rises uncontrollably. This brings the
twin dangers of a meltdown and of a steam
explosion. In the case of Three Mile Island, much
of the fuel melted, but the steel container and
the outer shell remained intact; in the case of
Chernobyl, the steel container had started to melt
when it was destroyed by a powerful steam
explosion. There was no outer shell to contain the
explosion.
In the three affected reactors
at Fukushima, the water evaporated due to a power
outage in the cooling system, the fuel started to
melt, and the outer reinforced concrete shells of
the reactors were blown off by what is presumed to
be hydrogen explosions. The latter are very
different from steam explosions inside the
reactor, and were caused by gas that the engineers
vented out in desperate attempts to prevent steam
explosions. In the case or reactor number 2,
however, the explosion also reportedly damaged the
reactor container; if this information is correct,
it means that practically all major mechanisms of
protection were incapacitated.
There is a
lot of uncertainty as to the precise situation of
the reactors, and it is difficult to estimate the
precise degree of the damage. Two of the most
dangerous by-products of uranium fission are
radioactive iodine, which causes thyroid cancer,
and caesium. The Japanese government is already
planning to distribute iodine tablets to the
population, which would lessen the effects of the
radioactive iodine. As of Tuesday, news agencies
are reporting panic in Tokyo, at least among
foreigners there, with many embassies evacuating
staff members.
If the situation can be
contained for another few days, there is a chance
that the fuel will gradually cool down, and a
major disaster will be averted. Reuters reported
on Monday that desperate attempts to cool the
reactors down by pumping sea water directly into
them had produced results, and reactors number 1
and 3 had started to stabilize. However, even on
Monday there were signs of major environmental
pollution, and an American aircraft carrier 160
kilometers off-shore was forced to divert its
course after passing through a radioactive cloud.
In light of the developments on Tuesday at reactor
number 2, the optimistic scenario seems
improbable.
Meanwhile, Japan is struggling
in the aftermath of the earthquake and tsunami
that hit the northeast part of Japan, with more
than 2,000 people confirmed dead and fears that
that number could rise to 10,000 in this disaster
alone. The crisis is also exacting an enormous
economic toll, with estimates of the damage
running into the hundreds of billions of dollars.
Japanese stocks lost over 13% on Tuesday on
radiation worries, after another steep decline on
Monday, raising prospects of a new recession in a
country where debt already runs at around 200% of
gross domestic product.
Prime Minister Kan
said on Sunday that Japan was facing its worst
crisis since World War II. By all accounts, the
disaster is now of previously unimagined
proportions.
Victor Kotsev is a
journalist and political analyst based in Tel
Aviv.
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