8.9 Magnitude quake hits offshore Japan

[kdogg]

Footage from inside the plant:
http://www.youtube.com/watch?v=dEUh7...mbedded#at=416

[photon]

Originally Posted by kirant

I'm not expert in the area, but what's the tolerance between a meltdown and a runaway reaction?

A meltdown isn't really well defined, but usually refers to the fuel rods melting.

This can be bad because you get reduced surface area for cooling (big blob rather than thin rods), and you also can't control things (i.e. having control rods in place) so the potential for areas of criticality to occur exists.

It looks like that happened, but obviously not seriously enough to cause any significant harm (since radioactivity levels are generally low all around the area).

That article is confusing because they keep seeming to confuse a pressure vessel with a containment vessel, using them interchangeably when they're different things.

[kirant]

Originally Posted by photon

A meltdown isn't really well defined, but usually refers to the fuel rods melting.

This can be bad because you get reduced surface area for cooling (big blob rather than thin rods), and you also can't control things (i.e. having control rods in place) so the potential for areas of criticality to occur exists.

Yeah, but one of the biggest issues is that temperatures of meltdowns tend to coincide with formation of potentially explosive materials (IE Hydrogen in a metal catalyst environment). I'm wondering how close these two were related (especially since hydrogen explosions were blamed for the destruction of the building and much of the non-reactor part of the complex).

[photon]

Originally Posted by kirant

Yeah, but one of the biggest issues is that temperatures of meltdowns tend to coincide with formation of potentially explosive materials (IE Hydrogen in a metal catalyst environment). I'm wondering how close these two were related (especially since hydrogen explosions were blamed for the destruction of the building and much of the non-reactor part of the complex).

I don't doubt the hydrogen explosions were a result of the zirconium cladding reacting with steam creating hydrogen, especially since lots of heat is required to start that and cooling was nonexistent after the batter backups ran out of power.

And it's still a threat too, that's why they're injecting nitrogen gas into the containment vessel on reactor 1, to reduce the chance of a hydrogen explosion.

[kirant]

Originally Posted by photon

I don't doubt the hydrogen explosions were a result of the zirconium cladding reacting with steam creating hydrogen, especially since lots of heat is required to start that and cooling was nonexistent after the batter backups ran out of power.

And it's still a threat too, that's why they're injecting nitrogen gas into the containment vessel on reactor 1, to reduce the chance of a hydrogen explosion.

Sorry. Maybe I'm just a bit ambiguous: I was wondering what the chances of a full runaway reaction occuring were given the fact that a partial meltdown had begun (if they are known at all. I suspect this may be something a nuclear physicist would be required for).

[photon]

Originally Posted by kirant

Sorry. Maybe I'm just a bit ambiguous: I was wondering what the chances of a full runaway reaction occuring were given the fact that a partial meltdown had begun (if they are known at all. I suspect this may be something a nuclear physicist would be required for).

Yeah, and even then you're talking about a lot of different variables and the chances are going to vary greatly depending on what exactly happens.

There's some discussion about failure modes and mitigation here:

http://www.osti.gov/energycitations/...sti_id=5642843

In scenarios of small-break LOCAs, there is generally a pool of water in the lower plenum of the vessel at the time of core relocation. Release of molten core materials into water always generates large amounts of steam. If the molten stream of core materials breaks up rapidly in water, there is also a possibility of a steam explosion. During relocation, any unoxidized zirconium in the molten material may also be oxidized by steam, and in the process hydrogen is produced. Recriticality also may be a concern if the control materials are left behind in the core and the relocated material breaks up in unborated water in the lower plenum.

That's recriticality though and not really a full runaway reaction (though really the difference is just in degree I guess). Because the melted material (corium they call it lol) contains not just the nuclear material but the control rod material and all the other stuff that got melted along with it, it's probably really hard to say exactly what the chances are.

The wiki for corium is pretty interesting: http://en.wikipedia.org/wiki/Corium_(nuclear_reactor)

[Jedi Ninja]

Another day of bad news, in no particular order: The basement of reactor one was unexpectedly discovered to be flooded today, pointing towards a full breach of containment, the evacuation zone has been extended from 20KM to 30KM, and another worker died today.

[freedogger]

Quarantine in place seems to be the default choice. Too many people to move. So sad!

Nebraska's Fort Caldoon plant is facing its own slow-motion tsunami. Hopefully it fares better. Pretty good update here: http://www.zerohedge.com/article/global-nuclear-update


The Petkau effect:
http://www.laka.org/docu/boeken/pdf/6-01-4-80-46.pdf
"Low doses protracted over periods of days, months or years are far more dangerous, per unit of absorbed radiation, than high doses from external sources. Mathematically, this turns out to be of the form of a concave downward or logarithmic relation between dose and the biological response for individuals exposed to different amounts of radiation during a given time period, as in the case of releases into the environment that enter the diet and concentrate in critical organs such as the bone marrow, the thyroid and the pituitary gland."


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http://www.sciencemag.org/content/332/6036/1368.full

Parents in Tokyo’s Koto Ward enlisted the help of Tomoya Yamauchi, a radiation physicist at Kobe University, to measure radiation in their neighborhood. Local government officials later joined the act, ordering radiation checks of schoolyards and other public places and posting the results on their Web sites. An anonymous volunteer recently plotted the available 6300 data points on a map. And Yukio Hayakawa, a volcanologist at Gunma University, turned that plot into a radiation contour map.

It shows one wide belt of radiation reaching 225 kilometers south from the stricken reactors to Tokyo and another extending to the southwest. Within those belts are localized hot spots, including an oval that encloses northeast Tokyo and Kashiwa and neighboring cities in Chiba Prefecture.

Radiation in this zone is 0.4 microsieverts per hour, or about 3.5 millisieverts per year. That is a fraction of the radiation found throughout much of Fukushima Prefecture, which surrounds the nuclear power plant. But it is still 10 times background levels and even above the 1-millisievert-per-year limit for ordinary citizens set by Japanese law.

[Thor]

Anyone have an earthquake app on their phones? Its unreal how many quakes around 5ish occur just off the coast of Honshu every week, I'm stunned at how frequent Japan has quakes.

[fanman]

There was a 5.9 off the coast of Fukushima that I felt pretty good here last night. If you're interested in checking it out I use this website sometimes after feeling a tremor.

http://www.jma.go.jp/en/quake/

It's from the Japanese Meteorological Agency - in English. They have their own separate scale here that goes upto 7, which is what this site uses.

The newer cell phones are wired into the early warning system here. It's not an app that you would have to buy separately. There's a crazy siren sound that goes off if a bigger earthquake happens close to your area. I can't remember exactly how big it has to be to trigger the alarm.

I bought a new cell here after the big quake, and the first time that alarm went off it scared the crap out of me. Wasn't sure what was happening, or where the alarm was coming from.