Effects of nuclear meltdowns
Albert Einstein said that nothing can move
faster than the speed of light. I believe that there is nothing said amongst
mankind that is swifter than a rumor. Let me tell you of such a rumor that was
heard all over the world.
After the Second World War ended, the rumour
that encircled the Earth was that all the oxygen on Earth was going to burn
away and we would all suffocate to death. Somehow, the rumor appeared to us as
having some logic to it. The Americans had exploded three atomic bombs. The
first one exploded in Nevada. It was the test bomb. The second one was the bomb
that was dropped on Hiroshima, Japan and the third one was the one that was
dropped on Nagasaki, Japan a week later. Within a month, the rumours began spreading
like wild fire. I was eleven then and living in a small mining town in the
middle of British Columbia and even we were recipients of the rumor. It was
scary because we believed then that the fire from any more bombs would ignite
the oxygen and poof—every living thing would be history. Well, as we all know
now, that didn’t happen nor would it ever happen no matter how many nuclear
bombs were exploded.
Then a new rumor began to
circulate in the 1970s. The rumor was premised on a hypothetical nuclear-reactor accident that might occur in which the nuclear fuel would
melt through the
floor of the
containment structure and burrow into the earth and erupt out of the opposite side
of our planet. If the nuclear melt-down occurred in the United States, it would
erupt in China. Hence the term, the China Syndrome—hence the fear.
So far, there have been nuclear
meltdown events. They occurred in the United States, The Ukraine, Japan,
Switzerland, Canada, the United Kingdom, France and Czechoslovakia.
Several nuclear submarines also had meltdowns. Yes, my dear readers, there were
no eruptions that occurred on the other side of our planet as a direct result
of those meltdowns. That misleading rumor eventually fizzled like a wet
firecracker
.
The authorities told us all that having
nuclear reactors that would generate electricity would replace coal-fired
generating plants. “Then,” they said, “the air will no longer be polluted.”
Tell that to the people in the city of
Pripyat in the Ukraine that was closest to the Chernobyl meltdown that forced
all 50,000 inhabitants to flee the city along with the other people living
within the 2,500 square-kilometre radiation zone the day after the Chernobyl
disaster.
Let me explain to you what happens when there
is a nuclear meltdown. A Nuclear meltdown is an
informal term for a severe nuclear
reactor accident that results in core damage from overheating. The term is
a reference to the core's either complete or partial collapse. “Core melt
accident” and “partial core melt” are the analogous technical terms for a
meltdown. A core melt accident occurs when the heat generated by a nuclear
reactor exceeds the heat removed by the cooling systems to the point where at least
one nuclear fuel element exceeds its melting point.
This differs from a fuel element failure, which is not caused
by high temperatures. A meltdown may be caused by a loss of coolant, loss of coolant pressure,
or low coolant flow rate or be the result of a criticality excursion in which the reactor
is operated at a power level that exceeds its design limits. Alternately, in a
reactor plant such as the RBMK-1000, an external fire may endanger the core, leading to
a meltdown. Once the fuel elements of a reactor begin to melt, the fuel
cladding has been breached, and the nuclear fuel (such as uranium,
plutonium,
or thorium)
and fission products (such as cesium-137,
krypton-85,
or iodine-131)
within the fuel elements can leach out into the coolant. Subsequent failures
can permit these radioisotopes to breach further layers of containment. Superheated
steam and hot metal inside the core can lead to fuel-coolant interactions, hydrogen explosions, or water hammer,
any of which could destroy parts of the containment.
A meltdown is considered very serious because of
the potential for radioactive materials to breach the
containment and escape (or be released) into the environment, resulting in radioactive contamination and fallout,
and potentially leading to radiation poisoning of people and animals nearby. No. A meltdown does not result in eruptions on the other side of our planet.
An automobile is a complex machine and yet we
have accidents. All vehicular accidents can be attributed to stupidity either
by the operator or the manufacturer. Nuclear reactors are extremely complex
machines and a number of them have had meltdowns. That can be attributed
primarily to the operators and to some degree to the builders also.
Chernobyl disaster
In the Chernobyl disaster, the fuel became non-critical
when it melted and flowed away from the graphite
moderator. However, it took considerable time
to cool. The molten core of Chernobyl (that part that was not
blown outside the reactor or did not vaporize in the fire) flowed in a channel
created by the structure of its reactor building and froze in place before a
core-concrete interaction could happen. In the basement of the reactor at
Chernobyl, a large part of congealed core material was found, one example of
the freely-flowing corium. Time delay, and prevention of
direct emission to the atmosphere (i.e., containment), would have reduced the
radiological release. If the basement of the reactor building had been
penetrated, the groundwater would be severely contaminated, and its flow could carry
the contamination far afield.
The disaster was caused by a power excursion that
led to a steam explosion, meltdown and extensive offsite consequences. Operator
error and a faulty shutdown system led to a sudden, massive spike in the neutron
multiplication rate, a sudden decrease in the neutron period, and a consequent
increase in neutron population; thus, core heat flux
increased rapidly beyond the design limits of the reactor. This caused the water coolant
to flash to steam, causing a sudden overpressure within the reactor pressure vessel leading to
granulation of the upper portion of the core and the ejection of the upper plenum
of said pressure vessel along with core debris from the reactor building in a
widely dispersed pattern. The lower portion of the reactor remained somewhat
intact; the graphite neutron moderator was exposed to oxygen-containing
air; heat from the power excursion in addition to residual heat flux from the
remaining fuel rods left without coolant induced oxidation
in the moderator and in the opened fuel rods; this in turn evolved more heat and
contributed to the melting of more of the fuel rods and the outgassing
of the fission products contained therein. The liquefied remains of the melted
fuel rods, pulverized concrete and any other objects in the path flowed through
a drainage pipe into the basement of the reactor building and solidified in a
mass, though the primary threat to the public safety was the dispersed core ejecta,
vaporized and gaseous fission products and fuel, and the gasses evolved from the oxidation of the moderator. The
radiation was spread far and wide
.
The disaster initially killed twenty-eight people due to acute radiation syndrome, and
it has been suggested that later up to five thousand victims died from fatal
cancers and this was due to operator stupidity. The city of Pripyat in the Ukraine will continue to be abandoned in our lifetimes.
How did the operators of the Chernobyl reactor fail? There was a safety drill at the plant. It supposed to be done at day time
when more senior engineers would be present then. But it was postponed to night
when the electricity demand from the plant was at its lowest. But at that time
only junior engineers were present at the No 4 reactor. When the reactor
overheated, they didn’t know how to prevent the meltdown. The decision to
conduct the safety drill at night was a terrible blunder that caused the loss
of many lives and also caused many billions of dollars in property losses. The
senior man on the job that night was the man who gave the order to conduct the
drill when he wasn’t qualified to handle the meltdown. The lives of all those
people were on his shoulders. It is unlikely that he and the others in the
control room survived the radiation.
This
disaster cannot be placed on the shoulders of the operators who were on duty
that fateful day in March 2011, when three
of the power plant's six reactors suffered meltdowns in which most of the fuel
in the reactor No. 1 Nuclear Power Plant melted. The failure occurred when the plant was hit by the tsunami
triggered by the Tōhoku earthquake. Radioactive material was released from the containment
vessels for several reasons: deliberate venting to reduce gas pressure;
deliberate discharge of coolant water into the sea; and uncontrolled events.
Concerns about the possibility of a large scale release led to a 20 kilometres
(12 mi) exclusion zone around the power plant and recommendations that
people within the surrounding 20–30 km zone stay indoors. Later, the UK,
France and some other countries told their nationals to consider leaving Tokyo,
in response to fears of spreading contamination.
The
nuclear plant had begun releasing substantial amounts of radioactive materials beginning on March
12, becoming the largest nuclear
incident since the Chernobyl disaster. The waves hitting the plant
normally wouldn`t have caused any real damaged to the plant. That being the
case, then why was there a meltdown.
When
a motor vehicle’s electrical system fails, the car will no longer function. The
same goes for any nuclear power plant. The builder of the nuclear plant in Fukushima
placed the electrical generating machine at ground level. When the waves hit
it, it was destroyed—hence no power to operate the nuclear plant. Invariably,
the meltdown began since there was no way to stop it. If the fools who designed
the nuclear plant considered the possibility of waves sweeping over the
generator, they would have placed it high enough so that the waves wouldn’t
have reached it.
The Fukushima
Nuclear Accident Independent Investigation Commission found the nuclear disaster was “manmade” and that its
direct causes were all foreseeable. The report also found that the plant was
incapable of withstanding the earthquake and tsunami. Regulators of the Nuclear
and Industrial Safety Agency and the government body promoting the nuclear
power industry (METI), all failed to meet the most basic safety requirements,
such as assessing the probability of damage, preparing for containing
collateral damage from such a disaster, and developing evacuation plans. A
separate study by Stanford researchers found that Japanese plants operated by
the largest utility companies were particularly unprotected against potential
tsunamis.
The World Health Organization indicated that people
living in the area were exposed to so little radiation that radiation-induced
health impacts were likely to be below detectable levels, and that any
additional cancer risk from radiation was small—extremely small, for the most
part—and chiefly limited to those living closest to the nuclear power plant. Later trace
amounts of radiation, including iodine-131,
caesium-134
and caesium-137,
were widely observed.
Although no short term radiation exposure fatalities
were reported, some 300,000 people evacuated the area, 15,884 (as of 10
February 2014) people died due to the earthquake and tsunami, and as of August
2013 approximately 1,600 deaths were related to the evacuation conditions, such
as living in temporary housing and hospital closures so the nuclear disaster alone
cannot be placed on the shoulders of those who should have known better. It is
believed that later, people in the immediate area will end up having thyroid
problems.
Three Mile Island
accident
.
The accident began with
failures in the non-nuclear secondary system, followed by a stuck-open pilot-operated relief valve in the primary
system, which allowed large amounts of nuclear reactor coolant to escape. The
mechanical failures were compounded by the initial failure of plant operators
to recognize the situation as a loss-of-coolant accident due to inadequate
training and human factors, such as human-computer interaction design
oversights relating to ambiguous control room indicators in the power plant's user
interface. In particular, a
hidden indicator light led to an operator manually overriding the automatic
emergency cooling system of the reactor because the operator mistakenly
believed that there was too much coolant water present in the reactor and
causing the steam pressure release. Why would a builder
of a nuclear facility place an indicator light out of sight of an operator in
the control room?
The partial meltdown
resulted in the release of unknown amounts of radioactive
gases and radioactive iodine into the environment. Dire predictions were made by anti-nuclear movement activists; epidemiological studies having deduced many instances of cancer from the
accident, but they cannot be proven. Cleanup started in August 1979, and
officially ended in December 1993, with a total cleanup cost of about
$1 billion. The cause of this meltdown was failures of both operator and
builder.
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