Re: Nonsense ! LHL, The Genius Is Going To Build One Here
Singapore is too tiny to withstand any incident that can happen. No matter how well it is designed and hpw good the operators are, there is some slight chance of an accident. I think the following will give the reader a better insight.
The Myth of a Reactor Explosion:
It is impossible for any PWR or LWR nuclear reactor to explode like an atomic bomb. This is because in order for an uncontrolled chain reaction to occur that is similar to an atom bomb, the uranium fuel must be extremely enriched, much more than the 4% 235U that is present in regular, commercial nuclear reactor fuel. So, if it can't explode, what does happen in a nuclear reactor? The answer is what is called a meltdown.
When a meltdown occurs in a reactor, the reactor "melts". That is, the temperature rises in the core so much that the fuel rods actually turn to liquid, like ice turns into water when heated. If the core continued to heat, the reactor would get so hot that the steel walls of the core would also melt. In a complete reactor meltdown, the extremely hot (about 2700� Celsius) molten uranium fuel rods would melt through the bottom of the reactor and actually sink about 50 feet into the earth beneath the power plant. The molten uranium would react with groundwater, producing large explosions of radioactive steam and debris that would affect nearby towns and population centers.
In general a nuclear meltdown would occurr if the reactor loses its coolant. This is what occured in the two disasters that we will discuss. Without coolant, the core's temperature would rise, resulting in the meltdown scenario we explained above.
You may be wondering, "Why can't they just drop the control rods in the reactor if it starts to get out of control?". The answer is that they can. The problem is that, even if the control rods are completely dropped in and the nuclear chain reaction stops, the reactor is still extremely hot and will not cool down unless coolant is put back in. The residual heat and the heat produced from the decay of the fission products are enough to drive the core's temperature up even if the nuclear chain reaction stops.
Three Mile Island Incident
No one was directly injured as a result of the accident. However, some radioactive gas and water were vented to the environment around the reactor. At one point, radioactive water was released into the Susquehanna river, which is a source of drinking water for nearby communities. No one is really sure what effects these radioactive releases might have had on people living near the power plant.
Chernobyl
During the days following the accident, hundreds of people worked to quell the reactor fire and the escape of radioactive materials. Liquid nitrogen was pumped into the reactor core to cool it down. Helicopters dumped neutron-absorbing materials into the exposed core to prevent it from going critical. Sand and other fire-fighting materials were also dropped into the core to help stop the graphite fire. All in all, over 5000(metric) tons of material were dropped into the core.
After the fires were brought under control, construction of what is called "the sarcophagus" began. The word "sarcophagus" is usually used to describe the elaborate coffins the ancient Egyptians used to entomb their dead. In this case, the sarcophagus is a structure erected from about 300,000 metric tons of concrete that surrounds the reactor. It was designed to contain the radioactive waste inside. It has served its purpose well, but, now, ten years after the accident, several flaws have been found in it. Holes have begun to appear in the roof, allowing rainwater to accumulate inside. This water can corrode the structure, further weakening it. Also, birds and other animals have been seen making homes in the sarcophagus. If they should ingest radioactive material, they could spread it around the countryside. Additionally, with time the sarcophagus has become worn down. It is conceivable that an intense event like an earthquake, tornado, or plane crash directly on the sarcophagus could lead to its collapse. This would be catastrophic, as radioactive dust would once again rain down on the surrounding areas. Scientists and engineers are working on ways to repair or replace the structure.
One of the great tragedies of the accident was that the Soviet government tried to cover it up. Clouds of fallout were traveling towards major population centers such as Minsk, and no one was warned. No one outside the Soviet Union knew about the accident until two days later, when scientists in Sweden detected massive amount of radiation being blown from the east.
The effects of the disaster at Chernobyl were very widespread. The World Health Organization (WHO) found that the radiation release from the Chernobyl accident was 200 times that of the Hiroshima and Nagasaki nuclear bombs combined. The fallout was also far-reaching. For a time, radiation levels in a Scotland were 10,000 times the norm. 30 lives were directly lost during the accident or within a few months after it. Many of these lives were those of the workers trying to put out the graphite fire and were lost from radiation poisoning.
The radiation released has also had long-term effects on the cancer incidence rate of the surrounding population. According to the Ukrainian Radiological Institute over 2500 deaths resulted from the Chernobyl incident. The WHO has found a significant increase in cancer in the surrounding area. For example, in 1986 (the year of the accident), 2 cases of childhood thyroid cancer occurred in the Gomel administrative district of the Ukraine (this is the region around the plant). In 1993 there were 42 cases, which is 21 times the rate in 1986. The rate of thyroid cancer is particularly high after the Chernobyl accident because much of the radiation was emitted in the form iodine-131, which collects in the thyroid gland, especially in young children. Other cancer incidence rates didn't seem to be affected. For example, leukemia was no more prevalent after the accident than before.
What caused the accident? This is a very hard question to answer. The obvious one is operator error. The operator was not very familiar with the reactor and hadn't been trained enough. Additionally, when the accident occurred, normal safety rules were not being followed because they were running a test. For example, regulations required that at least 15 control rods always remain in the reactor. When the explosion occurred, less than 10 were present. This happened because many of the rods were removed to raise power output. This was one of the direct causes of the accident. Also, the reactor itself was not designed well and was prone to abrupt and massive power surges.
