Anatomy of Japan’s Nuclear Plant Meltdown

In the 1979 movie “The China Syndrome” a nuclear reactor experiences a meltdown of it’s core.

In this hypothetical scenario, nuclear material located within a containment building reaches a temperature beyond a manageable capacity. As the temperatures increase, the reactor melts and burns through the foundation of the power plant and into the crust of the earth.

The idea behind the term “China Syndrome” is that once the nuclear material generates heat beyond 4,000 degrees Fahrenheit, it could continue to burn itself all the way through the earth, to the other side of the planet, stopping at China.

The Fukushima Daiichi Nuclear Power Plant in Japan has 6 “Boiling Water” reactors that were completed in the late 70's. In fact, the plant that has reached a critical place of possible meltdown was designed by the United States.

The basic structure of the facility in which the nuclear material is housed, is encased in a core of six-inch thick solid stainless steel containment structure that is pill-shaped. Inside this structure are several hundred fuel rods assemblies. Each Assembly has about one hundred fuel rods constructed of Zirconium Alloy.  These fuel rods have within them, pellets of Uranium that have been enriched from three to five percent of the energy producing U-235 Isotope.

The following description and illustrations depict what happened so far at Fukushima, and what we may expect to happen in the future:

The Fukushima Nuclear power plant in Japan uses a facility called a “Boiling Water Reactor”. (1) Two thirds of the reactor is filled with water. (2) Below the water is a section of Nuclear fuel rods made from Uranium. (3) As the Uranium fuel rods generate heat, water begins to boil and produces steam that is piped into a turbine that is spun. (4) Electricity is generated.

In the case of the Fukushima plant, when the earthquake occurred, ironically electrical power to the plant was disrupted. Even the generator backups failed to operate. (1)  Water flow to the reactor is cutoff. As more water is heated and turned into steam, there is less water in the reactor. When this happens: (2) The water level begins to drop until the nuclear fuel rods are exposed.

As the water level continues to drop, the temperature within the reactor goes from a normal temperature of about 2,000 degrees to 4,000 degrees. At this temperature the fuel rod’s protective coating is destroyed and the rods react with the uranium or plutonium fuel. Nuclear meltdown is imminent.

The first possible scenario (1) is that the massive heat inside the core of the reactor will burn through the bottom of the reactor and sink into the crust of the earth. As the core comes in contact with the water reservoirs beneath the plant, it will release radioactive material. The second scenario (2) is that the reactor vessel will reach such a great pressure that it will explode through the 6-inch solid stainless steel containment casing, causing massive amounts of Radioactive material to escape into the atmosphere.

As you can see, the crisis began because of a decrease in the water supplied to the plant. This was due to the electricity being cut off by the massive 8.9 magnitude earthquake. Even the Generator backup system failed. Ironically, the power plant that produces electricity, cannot itself survive unless electricity is supplied to it.

As soon as the earthquake occurred, the Fukushima reactors went into automatic shutdown. When shutdown begins, specially constructed neutron absorbing fuel rods called “Control Rods” are inserted in between the uranium fuel rod assemblies, stopping the nuclear reaction that causes heat.

The problem with the Fukushima plant is that although the nuclear reaction was halted, the nuclear fuel that was already burning, creates completely new products that themselves generate a tremendous amount of heat by radioactive decay. There is no way to stop this heat from being generated except by the introduction of cool sea water.

When the sea water cannot reach the nuclear containment structure, the ensuing scenario of Fukushima takes place.

Seeking to release some of the pressure within the containment structure, the plant operators released into the atmosphere, the Hydrogen gas that had been built up inside. The cause of this buildup of pressure is the Zirconium alloy in the fuel rod assemblies. The Zirconium that lines the fuel rod assemblies, has most likely melted due to the massive increase in temperature inside the plant. When Zirconium reaches about 4,000 degrees and comes in contact with water, it created Hydrogen gas that is highly combustible.

The explosion and complete destruction of the concrete retainment building at Fukushima was due to the buildup of this highly volatile Hydrogen gas being ignited.

At this point we know that the Zirconium lined fuel cells have melted. The Uranium and Plutonium pellets inside the fuel cells have fallen out into the floor of the pressure vessel. The next stage is a complete meltdown of the core

If enough of these Uranium and Plutonium pellets are released inside the reactor, the plant will reach “Critical Mass” and begin producing uncontrolled heat that would lead to Nuclear Meltdown.

At this moment, the plant operators are filling the structure with Boronic Acid that has the effect of neutralizing the neutrons produced by the Uranium and Plutonium pellets. This could slow the nuclear reaction of the facility and reduce the temperature. Many experts do not believe that this is possible now, considering the advanced stage of the nuclear process.

One of the techniques that is being deployed in the two reactors at the Fukushima Nuclear station is to pump cool sea water into the reactor core. The normal coolant used to maintain the proper temperature inside the reactor is not salt water. The implementation of sea water means that the owners of the plant have basically decided that the plant is beyond commercial redemption. Once sea water is pumped into the reactor, it virtually renders the nuclear core useless to ever again produce power. The good news is that the immediate use of cool sea water seems to have saved the nuclear core from completing the meltdown process.

If the pumping of sea water into the reactor does not succeed, there is no way to turn off the process that has already begun at the plant. If the heat continues to build up, it will be impossible to stop the tragic effects. Unless the material from inside the plant can be removed, there is no hope of stopping the current process and prevent an unimaginable Nuclear accident.

Rob Robinson

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