What Does “Nuclear Meltdown” Mean?

There has been a lot of confusion over the term “Nuclear Meltdown” as it has been applied to the two reactors that are in apparent meltdown in Japan.

It is important to understand that the Nuclear Reactors in Japan are different from the Chernobyl Nuclear Plant in Russia that did not have a solid stainless steel vessel covering the reactor. At Chernobyl, only a concrete containment building covered the entire structure of the reactor. When the Hydrogen gas built up and exploded, it destroyed the only containment structure that Chernobyl had to keep nuclear material from being dispersed into the atmosphere and surrounding area.

At all of the Nuclear Facilities in Japan, there is within the concrete containment building, a secondary protective device that is over the reactor core. This vessel is made from solid stainless steel, over 6 inches thick. It is within this vessel that the current meltdown of the fuel rods containing Uranium and Plutonium beads, are occurring.

What we have seen in the two explosions of the containment buildings at the Fukushima Power Station in Japan are only the outer structure, not the inner vessel.

Even though there are active Nuclear Meltdowns happening in two of the reactors, they are still being contained within the secondary inner vessel of solid stainless steel. As long as cool sea water is being pumped into these inner vessels, experts may be able to keep the nuclear meltdown contained within the inner structure.

Should the levels within the inner vessel reach a much higher temperature, an all-out meltdown would occur that would destroy the inner vessel and explode all the nuclear materials within the inner vessel, out into the atmosphere and surrounding area.

The reason that the two reactors are classified currently as only being in a “Partial Meltdown” is that only the outer concrete containment building has been destroyed. These outer structures were destroyed when the alloy that lines the fuel rods containing Uranium and Plutonium reached a critical temperature of about 4,000 degrees and began to melt. This is where the term “Melt Down” comes from. In the process of the Zirconium lined fuel cells melting, as they come in contact with the cool sea water that has been pumped into the reactor, the steam that is produced is made up of Hydrogen gas. Of course, Hydrogen gas is extremely combustible and there are many ignition sources within the reactor.

As this Hydrogen gas built up in the outer concrete containment structure, it was ignited and blew apart the outer concrete building, not the inner solid steel vessel.

A meltdown of the nuclear fuel rods within the inner vessel has already taken place and this cannot be reversed. The only remedy to stop a full scale meltdown that will destroy the inner vessel, it to continue to cool the reactor with sea water.

Rob Robinson

This entry was posted on Monday, March 14th, 2011 at 10:56 am and is filed under Nuclear Meltdown, Rob Robinson. You can follow any responses to this entry through the RSS 2.0 feed. Responses are currently closed, but you can trackback from your own site.

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