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| Inheritance of global nuclear hazards 1957-2011 | | | Dr. Rajkumar Singh | 2/10/2021 9:24:51 PM |
| Apart from devastation caused by nuclear detonations and use of nuclear arms, like any large scale industrial activity, there have been numerous accidents and mistakes at nuclear power plants and reprocessing facilities. Till date several major/minor accidents have occurred in operating nuclear plants across the world and have exposed its workers and residents to dangerous levels of ionising radiations. In the history of nuclear world, first such incident took place in 1957 due to a fault in the cooling system in Kyshtym nuclear complex in Russia which led to a chemical explosion and the release of 70-80 tonnes of radioactive material into the air, exposing thousands of people and leading to the evacuation of thousands more. Besides, major accidents, which have killed, maimed and exposed large populations of workers and local residents, have been reported from various other nuclear facilities-Windscale nuclear reactor, UK (1957); Idaho National Engineering Laboratory, US (1961); Three Mile Island Power Plant, US (1979); Chernobyl Power Plant, Russia (1986); Seversk, Russia, (1993); the Tokai-Mura nuclear fuel processing facility, Japan (1989); Mihama power plant, Japan (2004); Fukushima Daiichi power plant Japan (2011) and the Marcoule nuclear site, France (2011). All these accidents and many more unreported ones including from India have obviously raised questions about the desirability of nuclear energy and any real possibility of it being "safe". It is also a fact that in each of these places people have not been able to return to their homes, that their lives have never been normal again and that they constantly live under the shadow of diseases and death makes nuclear energy patently dangerous.
Accounting of major accidents
Among all the nuclear plant accidents took place so far there have been four major incidents of plant failure-the Kyshtym accident in fuel reprocessing in 1957, the relatively smaller Three Mile Island meltdown (Unite d States), the much bigger Chernobyl accident (USSR 1986) and the recent Japanese incident at Fukushima. The first accident was purely due to underdeveloped technology, and much of the blame for the next two disasters is attributed to human error. Of these only one- Chernobyl qualifies as "horrific". In Idaho (1961) and Mihama (2004) there were fatalities but no radiation leakage. In Windscale (1957) and Three Mile Island (1979) there was significant radiation leakage but no immediate fatalities, and the epidemiology of radiation-induced cancers is not very clear. In Seversk (1993) there were no fatalities and only a mild leakage of radiation. In Tokaimura (1989) there were two fatalities and radiation leakage but no known after effects. In both Seversk and Tokaimura, the level of exposure for nearby people was a few tens of millisieverts at most; about three-four times more than what one would receive in a CAT scan. And Marcoule (2011) was not a nuclear accident at all. Even in Fukushima nobody died from radiation exposure. But the Chernobyl disaster is perhaps one of the worst in human history. It resulted from a lack of "safety culture" at the plant, design flaws in the RBMK reactor and a violation of procedure. Under it, serious radioactive contamination spread over 150,000 square kilometers in Byelorussia, Ukraine and Russia. Radioactive clouds deposited radiation thousands of kilometers away. Hundreds of thousands people had to be evacuated, and millions more were left to live in areas that were dangerous to their health and lives. Moreover, scientific studies have shown that the full consequences of the Chernobyl disaster could top a quarter of a million cancer cases and nearly, 100,000 fatal cancers. After the events on 11th September 2001, many people were reasonably concerned about the safety of nuclear power plants from terrorist activities.
Latest event of Fukushima
In the history of nuclear plant accidents, an unparallel incident took place at 3. pm on 11th March 2011 in the Fukushima Daiichi nuclear power plant of Japan. In this mishappening there were extraordinary natural forces in action and no one imagined that the unlikely combination of natural and man-made disasters would occur together-a massive earthquake, a towering tsunami and the failure of the so-called fool-proof safety and containment strategies. It was a 13-metre wave triggered by the 9.0 magnitude earthquake had toppled the six-metre protective sea wall, flooding the plant's six reactors and disabling all 13 of the site's back-up diesel generators, which had been switched on when the earthquake first struck. Without power, water could not be pumped into the reactors to cool them and soon they began to overheat and over pressurise.Twenty- four hours later, an explosion caused by a build up of hydrogen at reactor one ripped off the walls and roof. It was estimated after the incident that Fukushima released about a tenth of the radiation expelled into the atmosphere at Chernobyl. Before the disaster Japan was the world's third biggest user of nuclear power and had been planning to increase nuclear's share of the energy mixed to 50 per cent by 2030. The incident had severely weakened Japan's attachment to nuclear power after the Fukushima accident which sent radioactive materials into the ocean and atmosphere, contaminated the food and water supply, and forced the evacuation of 160,000 residents.
Lessons learnt
In fact, in this type of reactors water is used to cool the reactor core and produce steam to turn the turbines that make electricity. The water contains two of the least dangerous radioactive materials - radioactive nitrogen and tritium. Normal plant operations produce both of them in the cooling water and they are even released routinely in small amounts into the environment, usually through tall chimneys. Nitrogen is the most common gas in the earth's atmosphere, and at a nuclear plant the main radioactive form is known as nitrogen-16. It is made when speeding neutrons from the reactor's core hit oxygen in the surrounding cooling water. This radioactive form of nitrogen does not occur in nature. The danger of nitrogen-16 is an issue only for plant workers and operators because its half- life is only seven seconds. A half life is the time it takes half the atoms of a radioactive substance to disintegrate. The other form of radioactive materials often in the cooling water of a nuclear reactor is tritium. It is a naturally occurring radioactive form of hydrogen, sometimes known as heavy hydrogen. It is found in a trace amount in ground water throughout the world. Tritium emits a weak form of radiation that does not travel very far in the air and cannot penetrate the skin. After Fukushima, the big worries were on the reported release of radioactive materials - radioactive iodine and cesium, iodine-131 and potassium iodine. The central problem in assessing the degree of danger is that the amounts of various radioactive releases into the environment are now unknown, but the properties of the materials and their typical interaction with the human body give some indication of the threat. |
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