China Syndrome in Japan?

Not to be overly pedantic, but if it happens in Japan it won't be a "China Syndrome". It wold be more of a "Brazil Syndrome", or if we want to stay with the northern hemisphere, perhaps a "U.S. Syndrome".

Tom

 

great.

 

Here is good article about the nuclear plants. http://www.nei.org/newsandevents/information-on-the-japanese-earthquake-and-reactors-in-that-region/

 

It's new to me.
Would you please show us the news source?

Thanks in advance,
Ken@Japan

 

The real tragedy is what is happening to the Japanese people trying to survive in a fractured society (and in winter no less). My thoughts are with them.

That having been said, I can try to shed a little light on what's happening at the power plants.

In the fuel rods, U235 (the 235 atomic mass version, isotope) decays into..lets call it "other stuff". A low energy neutron can trigger the split, or it can happen spontaneously all by itself. Lots of heat is given off.

In a boiling water reactor (very old obsolete design), the heat boils water at high pressure, and this steam spins a turbine which makes power.

If you insert control rods or safety rods, they absorb slow neutrons and cut off the reactions at the first step. Unfortunately, they do not shut it off completely, and that "other stuff" also continues to decay without the help of slow neutrons. That's why you have to cool it even after the rods are in.

With no cool water coming in, the water that is in there heats up and increases the reactor pressure. You either let the steam out or cool it (by recirculating cool water). If you don't cool it, the pressure will build until an old-fashioned safety valve lets it out for you. That PSV discharges below the reactor into a area where there's a pool of water.

The fuel rods contain U235, but at a low purity, and they're surrounded by a zirconium-containing alloy called zircaloy. You have to coat it with something to keep the uranium from corroding. Whatever you coat the fuel with has to withstand boiling hot water, transfer heat well, and not absorb the neutrons. Zircaloy does all these things.

It has a problem though. If it gets too hot (way hotter than in normal operation), the zirconium will be oxidized by water and therefore give off hydrogen gas. Many metals do this, the most famous being sodium. Sodium does it at room temperature, zirconium does it (only) at high temperature.

So if you lose temperature control, and the fuel gets too hot, hydrogen gas is formed, adding to the pressure problem. When the PSV blows, the hydrogen ends up in the building that surrounds the reactor, and eventually ignites with the oxygen in air. In the case of the Japanese power plants, this blows off the flimsy metal walls of the building.

It also means that they have lost control of the reactor temperature somewhere in the core. The reactor is still there holding the fuel in, so they can't say for sure if it has melted or not, or how much has melted.

When they say a "little radiation has escaped", they're talking mostly about the steam.

The guys (engineers and operators) that are still in there trying to keep some kind of control are probably giving up their lives by staying and trying to keep it from getting worse. They are heroes.

 

Government regulators knew of a heightened risk of explosion in the type of nuclear reactors used at the Fukushima plant in Japan from the moment they went into operation.

Safety inspectors at America's Atomic Energy Commission (AEC) warned as early as 1972 that the General Electric reactors, which did away with the traditional large containment domes, were more vulnerable to explosion and more vulnerable to the release of radiation if a meltdown occurred.

Michael Mariotte, director of the Nuclear Information and Resource Service, said:

"The concern has been there all along that this containment building was not strong enough and the pressure containment system was not robust enough to prevent an explosion."

Japan's nuclear crisis: regulators warned of reactor risks | Environment | The Guardian

 

When I read that the tsunami wiped out the backup diesel generators, it was clear that the power needed to pump water into the core was gone completely. From there it is just a sequence of heating, melting, hydrogen generation, and H2 explosions/fire. The only remaining actions are to dump water from any source (seawater) via portable pumps or from jury rigged sources of electricity on top of the core. The real hope is that the bottom of the reactors do not breach with these triage efforts in progress.

"Containment" is a very deceptive term here. Note that the fuel pools for the spent fuel assemblies have also been destroyed, drained, and/or without cooling. These are far more worrysome since they are completely outside of the reactor to begin with. The unknown here is when the last fuel units were removed. If that was months ago, that is vastly, vastly better than weeks ago.

The contamination at Three Mile Island was slowly cleaned up with robots. I expect that same will happen here. Fortunately, Japan has the best robot technologies, so they will do well over time to work the sites with robotic technologies.

 

Japan: New radiation leaks harmful to health - Yahoo! News

 

Fire at Reactor 4 now. Even though it was shut down for maintenance (as were the other 2 undamaged reactors) it seems that the cooling of the spent fuel rods was malfunctioning. Even spent fuel creates a lot of heat.

 

Radiation level soars after Japan nuke plant fire - Yahoo! News

 

FYI,
Following is a portal site, provided by JP government (MEXT:Ministry of Education, Culture, Sports, Science and Technology), showing the latest radiation levels of each administrative divisions of Japan.
Disaster Information

edit:
English portal site
Disaster Information

There is only one report in Japanese (data until 09:00 JST = 00:00 UTC) is placed as of now.
There is no report shown from the disaster area, such as Fukushima, Miyagi and Ibaraki), but the data in other area, including Tokyo metropolis are shown.

The radiation levels are very low and stable, and it dos not affect our health at all now.

Ken@Japan

 

Hi all,
Please be aware that the nuclear fission energy and the [ame="http://en.wikipedia.org/wiki/Decay_heat"]decay heat[/ame] are very different.

The Three Mile Island accident was occurred at 97% of full power, nuclear fission period.
The Fukushima plant was safely shut down, then the cooling of decay heat problem occurred a few hours later from the shutdown.

The decay heat is big just after the shutdown, but it becomes down as time elapsed.
Please refer to attached chart.

Ken@Japan