JAPANESE NUCLEAR REACTORS
A second explosion rocked the Japanese nuclear plant damaged by an earthquake, where the authorities are working desperately to prevent a meltdown of the reactors.
The largest earthquake in Japan logs cleared the cooling of support from several affected reactors at a nuclear plant in Fukushima prefecture north of Tokyo, causing a buildup of heat and pressure.
All this raises a question: What happens now in the nuclear reactor core?
The reactor core consists of a series of tubes or zirconium metal rods containing uranium fuel pellets stored in which engineers call fuel equipment.
Water is pumped from the rods to keep them fresh and to create steam that drives a turbine generating electricity.
The cooling of support had problems several times during the past three days in reactors 1, 2 and 3 at the Fukushima plant.
In the normal operation of a reactor, high energy neutrons of uranium fuel and break hit atoms in a chain reaction that generates heat, new radioactive elements such as strontium and cesium, and new neutrons which continue the process.
The chain reaction stopped a few seconds of the earthquake in all nuclear reactors in Japan, including those most affected, and that turn off automatically, control rods made of boron were inserted into the fuel, which absorbed neutrons.
However, the natural breakdown of radioactive materials in the reactor core continues to produce heat, so-called waste heat, falling to a quarter of its original level during the first hour and then slowly disappears.
Normally this heat is removed by cooling pumps at the plant in Fukushima lost emergency power supply because of the earthquake, tsunami, or both.
Emergency workers try to cool the interior core of the reactor and residual heat removal by pumping sea water inside them. Boric acid added to seawater to try to stop further nuclear reactions, as an additional precaution.
The cooling of the reactors is important because although they have stopped the chain reaction, there is still enough heat to melt the metal rods that surround the uranium fuel. If these get hot enough, they react chemically with the surrounding water, producing explosive hydrogen gas.
It was that hydrogen gas which caused the two explosions at the plant in Fukushima, in Unit 1 on Saturday and in the reactor 3 on Monday, according to experts and officials.
Engineers attempted to vent the hydrogen into the atmosphere, which also contributed to some degree of local radiation because the gas contained small amounts of radioactive particles.
The reactor core is inside a thick steel container surrounded by a concrete containment structure. Around the whole building is more open to a fairly thin coverage that is not given an important structural function.
The hydrogen explosion only damaged the outer building that collapsed, not internal structures, officials said.
If you break a steel dome inside a reactor, radiation levels would rise. But at this point because there is not enough heat to destroy them, say experts.
There remains the risk that underlying the nucleus, which is what happened at Three Mile Island in Pennsylvania in 1979. In that case, the site would be sealed permanently.
Chernobyl in 1986 was a different situation where the control rods failed to control the fission chain reaction, and this led to an explosion that destroyed the reactor, which shed radiation that poisoned to Ukraine and Europe in the worst civilian disaster in history world.
A nuclear reactor is a device which produces a controlled nuclear reaction. It can be used to obtain energy in the so-called nuclear power plants, the production of fissile materials, such as plutonium, for use in nuclear weapons, naval propulsion or artificial satellites, or research. A nuclear plant can have several reactors. Currently only commercially produce energy nuclear fission reactors, although there are experimental nuclear fusion reactors.
Also arguably a physical facility where it is produced, maintained and controlled nuclear chain reaction. Therefore, in a nuclear reactor using a suitable fuel standard that ensures the production of energy generated by successive fissions. Some reactors can dissipate heat from the fission, others still use heat to produce electricity.
The power of a fission reactor can vary from a few kW to about 4500 MW thermal thermal (1500 MW "electric"). Must be installed in areas near water, like any power plant to cool the circuit, and must be placed in seismically stable areas to prevent accidents. They have heavy security. They do not emit gases that harm the atmosphere, but produce radioactive waste that lasts thousands of years, and must be stored for later use in advanced reactors and reduce its life span a few hundred years.
