What Is A Nuclear Meltdown?

[shineon2010]

This is very good basic right up of a meltdown, understand it better thanks Tom

 

[jamoise]

[citation][nom]Belardo[/nom]Except there really aren't many "modern" reactors. Most of these are 40+ year old designs. Of course, you are right that these are nothing like the Chernobyl fluster cuck.[/citation]

True, but as you said, nothing like Chernobyl, and also, I'm almost positive their would have been upgrades and maintenance on these systems in the past 40 years to bring them up to a globally recognized safety standard.

 

[Griffolion]

Scary stuff, i hope that one day we can operate wholly on renewable sources.

 

[Guest]

Most control rods are cadmium these days. The Chernobyl control rods were tipped with graphite.

Meltdown is when the fuel cladding and fuel are uncovered, and hot enough to melt. This happened at TMI. Just because a reactor melts down, doesn't mean the whole superstructure will have a massive steam explosion and send radiation all over the neighborhood.

Japanese/US reactors are incased in concrete/steel with enough thickness to withstand an impact with a jetliner. Chernobyl's reactor was housed in an almost factory type setup, with very little in the way of containment (metal sheets, metal roof).

 

[outlw6669]

[citation][nom]beayn[/nom]So I'm a little confused. I keep hearing that 4 reactors can possibly melt down and two reactors are critical. The confusing part is, are all 6 reactors at the same nuclear power plant or are there 6 separate plants that have reactors with issues? There's so much information on this out there I don't have time to sift through it all.[/citation]
Well, seeing as 3 of the 6 reactors where already fully shut down for an inspection when the disaster hit, I would say that your 'news' outlet is feeding you a load of sensationalist BS.

All 6 of the reactors are at a single complex, the Fukushima I Nuclear Power Plant.
Only 3 of the are having serious cooling issues while a fourth's low level waste yard caught fire for a short while.
All reactors are fully shutdown but must still be actively cooled for a period as decay heat (heat produced by quickly decaying byproduct isotopes) is still produced.
This decay heat will quickly reduce over a period of several days as the byproduct isotopes stabilize.

While it is a serious nuclear accident, there is little to no threat of radioactive contamination even in the event of a full core meltdown.
Due to the design of these and all other operational reactors, a Chernobyl style disaster is not possible.
At the worst, there will be a limited amount of radioactive material released in the immediate area around the damaged reactors.
Widespread contamination will not occur.

If you have a few spare minutes, I would highly recommend reading through This Article.
It will give you an excellent overview of the fundamentals of this type of reactor design and the safety net that is in place.
It is quite easy to understand and should prove very informative.

 

[beayn]

[citation][nom]outlw6669[/nom]Well, seeing as 3 of the 6 reactors where already fully shut down for an inspection when the disaster hit, I would say that your 'news' outlet is feeding you a load of sensationalist BS.All 6 of the reactors are at a single complex, the Fukushima I Nuclear Power Plant.[/citation]

Oh of course I expect "sensational" news from any news outlet. Thanks for the info, although I really was just curious if it was all at the same plant or multiple plants. When you hear people saying that all these nuclear reactors are having issues, one imagines multiple nuclear power plants along the coast of japan. It doesn't seem as bad talking about multiple reactors at a single plant. I just haven't had the time to watch enough news to see that.

 

[Wolvan]

www.nei.org (Nuclear Energy Institute)

They have updates there that are real and actually explain what is really going on. Unlike most of the reports that are sensationalized for tv and the web.

They have 4 reactors (units) at the one station that is having the main issue's. Several other stations (each with multiple units) also shutdown but are in safe conditions.

The chance of a major "meltdown" of a core at Fukushima Daiichi 1 are miniscule. Their are multiple redundant containments. Similiar to 3 mile island where everything was contained inside the core. Cherynoble was from poor Russian reactor designs with no containments and people in properly running dangerous engineering tests. Graphite is often use as a moderater for nuclear fission (most plants use water) and will burn when to hot. Most commecial nuclear power plants use boron rods and boron poison in the water to control reactivity. US Naval reactors actually uses Hafnium control rods which are even better then boron, but are to expensive for commercial work.

And yes I work in nuclear power. 11 years in the Navy in nuclear power (Submarine MM-nuke) and now work at a commercial nuclear plant in the mid-west for 6 years. I have my degree in Nuclear Engineering Technologies.

 

[Wolvan]

Edit to above. In alot of the older Russian designs, they used graphite as a moderator. Wasn't clear. The rest of the world uses water, which is self limiting moderator.

 

[noblerabbit]

Perhaps someone already asked, but I don't see the question, so here is my Question:

Why are there not any "Tidal" wave Generators, powered by the natural ocean, to produce electricity , for potentially the whole world 100 times over? Engineers, get to work! Every coast line I know of has nothing but broken clam shells!

 

[carsontl]

http/tinyurl.com/4ohr4ez

I shooped da whoop on this guide haha

 

[f-14]

[citation][nom]jamoise[/nom]sorry, but, ill start believing more of what I read, when its not from a news source who are out to sensationalize to bring readers to their website/buy newspapers. At the moment, I trust news websites about as much as I trust Barny the dinosaur, to deliver the latest on love compatibility between himself and yourself.[/citation]
i hear you on the trusting news papers and that type of media, but i think you can trust it this time
http/news.yahoo.com/s/nm/20110315/ts_nm/us_japan_quake

They said they may use helicopters to pour water on the most critical reactor, No. 4, within two or three days, but did not say why they would have to wait to do this.

"The possibility of further radioactive leakage is heightening," a grim-faced Kan said in an address to the nation earlier in the day.

"We are making every effort to prevent the leak from spreading. I know that people are very worried but I would like to ask you to act calmly."

Levels of 400 millisieverts per hour had been recorded near the No. 4 reactor, the government said. Exposure to over 100 millisieverts a year is a level which can lead to cancer, according to the World Nuclear Association.

The plant operator pulled out 750 workers, leaving just 50, and a 30-km (19 mile) no-fly zone was imposed around the reactors. There have been no detailed updates on what levels the radiation reached inside the exclusion zone where people live.

"Radioactive material will reach Tokyo but it is not harmful to human bodies because it will be dissipated by the time it gets to Tokyo," said Koji Yamazaki, professor at Hokkaido University graduate school of environmental science. "If the wind gets stronger, it means the material flies faster but it will be even more dispersed in the air."

with talk like this i don't think they are lying one bit. something was up if they were still having problems cooling and then a fire in the building breaks out outside of the building. i lived and fished right next to one of these for 6 years i had 2 neighbors that worked there one was the cheif operator the other guy changed out the fuel rods and we took class trips to this plant, inside and out. these things are made of conrete and steel and other non flamables coated with flame retardant and lots of lead paint. if there is a fire, it's a very very bad sign as there is very little to burn inside and out except for electronics and wearing sheating.
http/www.japannuclear.com/nuclearpower/program/location.html
for those that don't know there are 2 seperate plants (sendai & fukushima) with cooling problems from the quake alone, with 2 reactors at each facility originally in different cities, it is now 6 reactors the fukushima plant with all 4 reactors- 2 (now 3) have cooling problems and a 4th is severly damaged , on fire and leaking lethal radiation in the vicinity.
there were 3 explosions over the last 3 days, but they do not say which reactor or if all 3 explosions were at the same reactor.

the operators of the facility said one of two blasts had blown a hole in the building housing a reactor, which meant spent nuclear fuel was exposed to the atmosphere.

at the level of rads comming out and the remark of spent fuel it leads me to believe they have stored spent fuel rods some where inside the building that had not yet made it to dry cask storage that are the root cause of the radiation and fire problem.

i do not know if they have on facility dry cask storage, but earth quakes is one of the inherent problems i have been concerned with since after sept 11th attacks. a great many nuclear plants in the usa lay on fault lines and water supplies for millions (tens of millions actually) people. my chemistry is not great, but my physics are pretty decent.
my history is decent also and these major quakes on the pacific plate and it's lateral fault lines always answer back. so much so there is usually a crescendo of answering quakes n the following few years with the largest quakes forming a triangle linking japan, alaska and hawaii.
considering the new vent opening in hawaii 2 days before this and the china earth quake on the same day as well as an indonesian volcanoe popping off pretty good on the same day releiving pressure there i expect for a major quake like this to hit some where in alaska this time next year mid to late december or first week of janurary or mid to late may as late as the 1st week of july. that's just the pattern these quakes follow in the history books. sorry for the tangent, but look at how many nuclear plants are alonge the west coast and on hawaii. the japanese have spent millions on preperation for the last 20 years. nobody else has and have the same circumstances

 

[loomis86]

The amount of radiation that could leak out of these reactors is not as serious as the lack of electricity japan is going to be faced with for the next couple years.

 

[nitrium]

[citation][nom]nexus9113[/nom]The biggest danger of a melt down is not the explosion of the containment chamber, but the possibility of the fuel becoming so hot that it burns through everything it comes into contact with, which will result in what is known as "China Syndrome", a slang term coined by US nuclear engineers meaning that the "rock" can get so hot when unchecked it could melt straight through the planet to China if it didn't hit any cooling material.[/citation]
That is just about the dumbest thing I've read all day, and I've read a lot of BS today. So this nuclear material, once it gets to the centre of the earth (which comprises of molten iron), will somehow not only not dissolve but also defy gravity and burrow UP to China? THINK before you type.

 

[mavroxur]

[citation][nom]nexus9113[/nom]The issue with that situation is that it is highly likely the "rock" would hit an underground source of water before it got to the other side, instantly vaporizing all the liquid into extremely high temperature steam, increasing the pressure in that pocket exponentially, and creating an explosion of contaminated steam that would jet into the air like an explosion, destroying the area around the meltdown, contaminating the atmosphere, and distributing fallout for an incredible distance (Chernobyl was literally felt around the world to some degree).[/citation]

Use drugs much? The molten fuel would indeed melt into the ground, but would never make it that far. Small pieces of it would line the hole until there was not enough to keep melting down any further. Maybe a couple hundred feet maximum. And if it did miss a cooling medium, there is absolutely no chance of it "coming out the other side of the earth". The earth's mantle & core would take care of it before it came anywhere near that.



[citation][nom]ananke[/nom]I doubt the particicles can fly too far without a career [/citation]


A career always help things get further. If you lack a career, you usually wind up in the retail or food service industry.

 

[maestintaolius]

[citation][nom]Griffolion[/nom]Scary stuff, i hope that one day we can operate wholly on renewable sources.[/citation]
The reality of power generation is none of it is completely "safe". More people have been killed by wind turbines than nuclear. By it's very nature, power generation is an energetic process and will always have its problems, regardless of the source.

 

[eddieroolz]

Just wishing the situation won't deteriorate, though in all honesty it isn't as bad as the Western media says. I watch TBS.

 

[eddieroolz]

To add to the post above, it seems like Western media is becoming more sensational than the Japanese media that I watch. NHK, TBS, FujiTV, AsahiTV and TV Japan all recognize that it's serious but isn't overblowing the entire incident.

 

[jrnyfan]

[citation][nom]outlw6669[/nom]If you have a few spare minutes, I would highly recommend reading through This Article.It will give you an excellent overview of the fundamentals of this type of reactor design and the safety net that is in place.It is quite easy to understand and should prove very informative.[/citation]


erm...don't bother with that article as it turns out. The guy that wrote it isn't a nuclear scientist at all.

http/www.salon.com/news/politics/war_room/2011/03/15/josef_oehmen_nuclear_not_worried_viral

 

[outlw6669]

[citation][nom]jrnyfan[/nom]erm...don't bother with that article as it turns out. The guy that wrote it isn't a nuclear scientist at all.http/www.salon.com/news/politics [...] ried_viral[/citation]
Yes, but the MIT Department of Nuclear Science and Engineering has since taken over the article (as is shown in big bold letters at the top).
It really is an excellent place to start if you wish to have a more in depth understanding of the damaged reactors.

 

[jrnyfan]

That's an excellent point.

Perhaps I should clarify what I meant. The original article was full of 'nothing bad will ever happen ever' and that part was redacted. The actual scientists have taken over the article as you said, good reminder.