Thursday 29 May 2014

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 Syndromehence 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
 This incident was a partial nuclear meltdown that occurred on March 28, 1979 in one of the two Three Mile Island nuclear reactors in Dauphin County, Pennsylvania, United States. It was the worst accident in U.S. commercial nuclear power plant history.  

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. 
 I won’t go through the litany of more human errors with respect to other meltdowns but it is very obvious that greater care must be undertaken to train the operators of these facilities and special attention should be addressed towards the building of these facilities. Regulators should have enough common sense to foresee problems in the design of nuclear facilities so that stupid design flaws don’t trigger further nuclear disasters. 

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