An overview of nuclear meltdown shows reason for caution in the nuclear power industry, and explains the reasons for public fear. A nuclear meltdown can happen when the cooling systems in a nuclear reactor fail. It may also be caused by a fire within the reactor, or by operation of the reactor at levels above its design capacity.
For whatever reason, a reactor core can become so hot that elements that make up the shaped fuel inside the reactor melt. Once the components of the core melt out of shape, it becomes a difficult matter to control the reactor enough to slow or stop the reaction.
Nuclear meltdown is a layman’s term, used to describe the kind of incident that happened at the Fukushima power plant near Tokyo, Japan. At that plant, a huge earthquake and subsequent tsunami disabled the cooling system, by destroying the emergency generators designed to power mechanisms that would cool the reactor if the normal power supply failed.
Reactor Number 1 was probably the first reactor at the site to suffer a meltdown. Reactors 2 and 3 suffered meltdowns as well. Reactors number 4, 5, and 6 had already been shut down for routine maintenance when the earthquake hit, and were already cooling.
In the event, there were probably hydrogen explosions at all three of the operating reactors. The containment vessel intended to confine radioactive material was probably breached in reactor number 2, and the pools where spent fuel was stored were probably uncovered near several reactors.
There is no doubt that radiation was released. It has been measured repeatedly. Radiation was deliberately released into the air, as steam, to lower the pressure in the reactors, and radioactive water was deliberately released into the ocean. More radioactive water leaked into the sea.
The released radiation was mostly radioactive iodine and radioactive cesium. Lesser amounts of plutonium and other radioactive elements were also released. Plutonium is a deadly and persistent poison. However, it is probably not the main problem in Japan.
Radioactive iodine is dangerous because it can contaminate crops, milk, and groundwater. Once ingested by people, it can accumulate in the thyroid gland. In sum, it can cause cancer.
So can cesium isotopes. Iodine 131 quickly decays, and fades away. Cesium persists longer. No data are available about Fukushima yet, but data from Japanese atomic bomb survivors show elevated long term risks of cancers including leukemias and solid tumors.
Plutonium effects are dangerous because it accumulates in the liver and other organs, and in the bones. It is excreted only slowly, and does damage while it remains in the body. Again, the damage is likely to be long term, and likely to take the form of cancer. However, plutonium is relatively uncommon is the radiation that escaped from the Fukushima plant.
The area surrounding Chernobyl has shown an increase in cancers since the accident there, but not a substantial increase. The area around Three Mile Island, where America’s largest nuclear accident took place, has shown no increase in cancer rates, excluding the already existent cancers discovered when local residents were checked after the incident.
The exception is thyroid cancer. Children exposed to radioactive iodine do have a vastly increased risk of thyroid cancer. This risk can be mitigated with does of stable iodine, especially in iodine-deficient populations.
Chances are though, that most people who stay out of the zone the government has established around the Fukushima plant will not be at risk. Japan is a modern state. It is likely to monitor radiation levels essentially forever. Food supplies will probably be more carefully monitored than they are in the U.S.
As in America, most people in Japan die from heart disease, stroke, cancer, lung disease, and similar causes. Many of these illnesses, though certainly not all, are diseases that happen to people who eat to much, exercise too little, or are unlucky in their genetic heritage. As anywhere in the developed world, it is not catastrophe that kills most people.
Earthquakes, tsunamis, and nuclear meltdowns appall everyone who hears of them. Nevertheless, when such events are sensationalized it does no good to the survivors or to those who watch in horror. Events in Japan were horrifying, while the bravery of the Japanese people was and is heartening. Still, it is personal day-to-day actions that determine the quality of most people’s lives, whether in America or Japan.