Fukushima Reactor Sustained “Only” Partial Meltdown
The Fukushima nuclear power plant from Japan suffered a partial meltdown, and even if the situation is bad, the researchers said that it could have been worse, much worse.
They said that in the case of a full meltdown, the situation would have been much more critical than it is now. The damage and the radiation caused by a full meltdown are much higher than the ones caused by a partial meltdown. The experts said that the partial meltdown does not necessarily mean that the uranium fuel from the core has melted. They said that it is very likely that some of the fuel rods might be damaged, which means that they might have cracked, and thus, they release a certain amount of radiation. The full meltdown occurs when the rods remained uncovered by water for a certain amount of time. When that happens, the temperature rises extremely fast and high, as it can reach thousands of degrees Fahrenheit. In that case, the uranium fuel and the core melt, thus the level of radiation released is extremely high. The researchers said that it is very unlikely that such a thing will happen at the two reactors which were damaged by the natural catastrophe on Friday.
People working at the reactors tried to remediate the problem very fast, pumping lots of seawater on the cores in order to keep them wet. It would have been possible for the event to cause a chain reaction, if the temperature would have been extremely high, as that would have made the other reactors be affected by the temperature as well. The efforts done by the workers from the power plant have been beneficial; however, they will have to make sure that water is being pumped on the core of the reactors for a very long period of time, until the normal cooling systems will be restored. Arnold Gundersen, a former nuclear engineer , who worked on reactors similar to the ones which sustained damage in Japan, said that they will most likely have to pump water in the reactors for as much as an year. The amount of required water will be huge as well, thousands of gallons of it, on a daily basis.
The reactors which were affected by the earthquake were created by General Electric in the 1970s. They have thousands of very thin 12-foot-long-fuel rods which are stacked inside of a pressure vessel. The rods are made out of a zirconium alloy, and they have ceramic pellets of uranium oxide which are as small as a fingertip. Despite of the extremely low size, the uranium pellets can cause massive amounts of radiation. The fuel cores of these reactors, just like the cores from all the other nuclear power plants, are kept in water, which leads to the creation of steam, which is then used in order to generate electricity. It might seem surprising that the cores still require water, and you might be tempted to say that they should have shut the power plant down, which they actually did. However, the reactors operated at 550 degrees Fahrenheit, and there still is lots of residual heat in there. On top of that, the radioactive materials used at the power plant continue to generate energy even after they are no longer used. Imagine the power which these materials have, if they need to be cooled for at least one year, after they are no longer used.
Luckily, the technicians who work at the power plant observed the fact that the core of one of the reactors was exposed for a certain period of time, and they reacted very quickly. They reduced the temperature of the core by dropping seawater filled with boric acid on top of it. If the core is exposed for a prolonged period of time, then the zirconium from which the rods are made out of starts to crack. If that happens, dangerous gases are being released, which might cause an explosion. This is the reason why the explosion took place at one of the reactors. Margaret Harding, a consultant who worked on reactor designs for General Electric, said that even in these cases there is no certainty that the core will start to melt. There were other nuclear reactor incidents in the world, the biggest of them all being the Chernobyl incident, where a power surge caused a fire which then caused the core to explode. There was a core melt in the case of the Three Mile Island incident as well, but luckily, no one got hurt there. Mr. Gunderson said that the only way in which the situation could get worse would be if the technicians would not be able to keep the core wet for whatever reasons. If that would happen, the core would melt, and the entire facility would be destroyed, thus increasing the radiation in the area.
