What do meltdown or super meltdown mean?

Atomic disaster and the possible consequences for health

14/03/2011

It is still unclear how big the nuclear disaster in Japan is. Almost every minute, people reach new horror news from the Japanese disaster area. If the cooling of the affected reactors of the nuclear power plants in Fukushima can not be restored, nuclear meltdowns are at risk. The radioactive contamination would have revered health consequences for the people of Japan. In the media coverage fall again and again technical terms that are hardly understood by non-experts. That's why we've put together a glossary to explain the most important terms.

What does meltdown mean?
If the cooling and all emergency cooling systems of a nuclear reactor fail over a certain period of time, a meltdown can be set in motion. Physicists speak in this context of an irreversible process. The fuel rods, which contain radioactive fuel, heat up so much that they lose their original shape and melt. In such a very critical process, highly radioactive material can enter the environment uncontrollably from the nuclear reactor and endanger the health of humans and animals in a high degree. Because the melting mass can eat itself through the steel walls of the reactor vessel formally. There is a great danger, for example, because the radioactive mass can reach groundwater because the mass burns into the ground. If the containers and the building are damaged, radioactive substances also enter the respiratory air and thus contaminate the oxygen. Something similar had happened during the nuclear disaster in Chernobyl. At that time, the building was damaged by an explosion. In Japan, it is now trying with the help of seawater to achieve cooling from the outside. In addition one tries to lower the pressure in the reactor strongly. In principle, any reactor type can be affected by such a process.

What is radioactivity?
Radioactivity refers to the property of some substances that spontaneously transform with the release of energy in the other atomic nucleus. In the public debate, the terms radioactivity and radiation are often confused. The term is meant primarily in media reports not the material but the radiation. The radioactive energy is released in alpha, beta or gamma rays. At low concentrations, radioactivity also occurs in the natural environment. However, radioactivity also arises during nuclear transformations in nuclear plants. A radioactive load can not be detected by the sensory organs of humans. Radioactive substances can cause serious damage to the genome in humans and lead to malformations of newborns. In addition, the emergence of cancer is greatly favored.

radiation sickness
Radiation disease is a direct result of radioactive contamination. The rays mainly destroy human body cells. The effects of radiation sickness always depend on the duration and the dose of radiation exposed. The higher and longer the dose on humans, the worse the effects on the health. Typical symptoms of acute radiation sickness include burn-like conditions of the skin, hair loss, severe redness, fever, nausea, internal bleeding and anemia. An obvious feature of a serious radiation sickness is also the obvious dissolution of the skin all over the body of the patient. The higher and longer the radiation exposure, the lower the chances of survival. If the dosage was relatively low, long-term consequences can occur that are initially not visible after the contamination. Especially thyroid cancer and leukemia are typical sequelae of radioactive contamination.

What is cesium?
Cesium occurs in lower quantities in nature. The radioactive isotope cesium 137 is a product of nuclear fission. If the element enters the environment through the exhaust air or groundwater, it is absorbed by plants and animals. For this reason, cans in milk, meat, mushrooms and fish are detectable. If a person is exposed to a high dose of cesium 137, the muscle tissue and kidneys can be permanently damaged.

International rating scale „Ines“
Ines (International Nuclear Event Scale) is an internationally valid rating scale that uniformly categorizes incidents or nuclear accidents. The scale ranges from 0 to 7. The lowest level is a safety-related error that initially has no relevance to humans. The highest level is the so-called atomic one „meltdown“, where severe health effects on animals and humans in the broader environment are no longer preventable. Rating scale 7 was last proclaimed in the momentous reactor accident in Chernobyl. Seven means the heaviest release, effects on health and the environment in a wide environment, late health damage over large areas, possibly in more than one country. In Japan, although a nuclear emergency was proclaimed, but not the supergrain. According to currently available information, the nuclear accident is quantified with four of the Ines scale.

Fuel plutonium
The extremely toxic and highly radioactive heavy metal plutonium is used as fuel in nuclear power plants. Plutonium is also produced in each reactor as a by-product from a cleavage of uranium atoms. Environmentalists criticize in this context again and again that a major shortcoming of atomic energy is plutonium. Because the half-life of the substance is a whopping 24,000 years. After this time, only half of the radioactivity is reduced. If a person is contaminated with the toxic substance, then serious illnesses that can also lead to death. Plutonium is highly toxic and in particular damages the kidneys. In addition, it binds proteins in the blood plasma and also deposits in the bone tissue and liver. The deadly dose for a human is very likely in the double-digit milligram range. In dogs, it has been proven that a lethal dose of 0.32 mg / kg body weight is sufficient.

What is a super mountain??
From a Supergau one speaks, if the „Super biggest accident to be assumed“ a nuclear reactor takes place. The absolute supergrome occurs when man can no longer control the nuclear incident. As a result, politicians and the media speak of a supergau. The last super-Gau again took place in 1986 in Chernobyl, Ukraine. According to the INES directive, the accident was classified with the category seven. In Japan, the incidents are currently rated Four. That means: „Low release of radiation from the population at about the level of natural radiation exposure.“ From a supergauce in Japan can therefore according to the available information currently not be assumed. (Sb)

Also read:
Doctors demand shutdown of all nuclear power plants
Mass protests against nuclear power expected
Radioactive Radiation: Health Effects

Image: Gerd Altmann, Pixelio.de