Chain Reactions Reignited At Fukushima 234
mdsolar writes "Radioactive byproducts indicate that nuclear chain reactions must have been burning at the damaged nuclear reactors long after the disaster unfolded. Tetsuo Matsui at the University of Tokyo, says the limited data from Fukushima indicates that nuclear chain reactions must have reignited at Fuksuhima up to 12 days after the accident. Matsui says the evidence comes from measurements of the ratio of cesium-137 and iodine-131 at several points around the facility and in the seawater nearby."
Another good reason to switch to Thorium (Score:2, Informative)
http://www.energyfromthorium.com
We have no one to blame but ourselves for any accident that happens when a safer, cleaner, more efficient, and cheaper nuclear fuel is readily available and already has most of the hard problems with its implementation worked out through several running prototypes.
Re:Without a moderator? (Score:5, Informative)
In the first-12-day timeframe, the water wasn't boronated, it was just seawater.
Re:Whack-a-mole (Score:5, Informative)
There are reactor designs that currently exist that are more resilient to meltdowns. Most notably, thorium molten salt reactors, but there are only a handful of experimental reactors in existence. There is also the CANDU reactor primarily used and designed in Canada which is a uranium heavy water reactor.
I will agree with you that the ancient nuclear technology most reactors use today is not that safe, but more modern reactors have solved that issue. The only problem has been rolling out thorium and CANDU reactors.
And WRT your comment on terrorism, there's a video on Youtube I've seen that debunks the whole "flying a plane into a reactor" myth. Nuclear plants have concrete walls that are like 10 feet thick and the plane collapses on it self and does nothing to the wall.
Re:Whack-a-mole (Score:2, Informative)
The thousands of people coal plants kill every year due to air pollution and mining accidents? Must admit I'm struggling to find an absolute number, but this'll have to do:
http://nextbigfuture.com/2011/03/deaths-per-twh-by-energy-source.html
Re:Sensational! (Score:4, Informative)
Sensationalistic, atleast.
Did they restart? Techreview says "yes", Nature says "No":
http://blogs.nature.com/news/2011/05/analysis_suggests_fukushima_re_1.html [nature.com]
Re:Without a moderator? (Score:4, Informative)
Perhaps it has something to do with more fuel clumped more closely, like in a pile at the bottom of containment.
I believe it was unit 1 that had temperatures shoot up after a magnitude 7 aftershock. Given that the cooling situation hadn't changed, is there anything else but fuel shifting that would account for that?
Fuel that's piled up on the bottom may also get less of the inhibiting effects from either the boron control rods, or boron in solution.
Some believe that has has been some level of criticality in the unit 4 fuel pond based on the nature of the radiation coming off of that. Between some fuel damage from previous loss of coolant, possible use of coolant without boric acid for a time, and the world-wide industry practice of re-racking, it isn't surprising to have an issue with that. Re-racking is the practice of placing fuel assemblies at a closer spacing than original safety standards called for in or to be able to store more spent fuel.
Unit 3 has mixed oxide (MOX) fuel which includes plutonium. Since it gives off more neutrons when hit by them, it is harder to control. Reactors may need additional control rods and more boric acid in the coolant during normal operation to stay in control, and more yet when shut down. Unit 3 is potentially more troublesome to control if too much damaged fuel piles up on the the bottom. The environmental damage is also more apt to be longer term. As plutonium breaks down, the material produced actually gives off more radiation..
This blog has a fairly in depth look at MOX fuel
http://abundanthope.net/pages/Environment_Science_69/MOX-Fuel---Insanity-Part-1.shtml [abundanthope.net]
Re:Without a moderator? (Score:4, Informative)
I'm not arguing anything. I asked a question. If (and that still hasn't been conclusively proven, but there is evidence to indicate a good possibility) that re-criticality occured, then the natural next question becomes *how* did this happen? How is my model flawed? There's absolutely nothing wrong with that.
I never, ever said in my post that the data is wrong, nor even implied that. I simply asked how this happened without a moderator. So, please climb down off that horse and join the rest of us.
Re:Alarmist? (Score:5, Informative)
It started to carry a negative connotation when some people started using junk science to raise false alarms. Look at Helen Caldicott telling everyone that Chernobyl resulted in millions of deaths, and that Fukushima will result in millions of cancers.
She repeatedly appeals to a single source - a Greenpeace "Report" which they somehow managed to get the NYAS to publish without any peer review, which specifically states that it does not use standard scientific analysis methods because those methods don't give the results the report author wants to find.
She ignores all the other science which has been done to determine the results of Chernobyl, decrying it all as a massive "cover up" and "fraud". There's only one report in the world, apparently, which tells "the truth". These people cherry pick their sources to get the alarming results they want to find.
See: Confirmation Bias [wikipedia.org]
That is the sense that most people use when they pejoratively use the term 'alarmist' - someone who spreads FUD which is not based on sound science.
Re:Without a moderator? (Score:4, Informative)
update:
more radiation than they hoped in unit 1, 700 ms/hr on the first floor. It won't be easy to work in there unless they can bring that down somehow.
http://www3.nhk.or.jp/daily/english/08_18.html [nhk.or.jp]
the unit 4 fuel pond is less damaged than expected, so some good news.
http://www3.nhk.or.jp/daily/english/08_18.html [nhk.or.jp]
Diablo Canyon Unit 2 is shut down for refueling and maintenance. Since it was shut down about a month ago and they didn't decide to start refueling then, I suspect there is more to this. They're likely giving it some extra attention. They recently had a motor with the rotor slipping on the shaft. I wondered if they could have had a control system issue (PLC?) instead of mis-calibrated micro-switches and shaft tolerance issues as given for the reason the backup cooling was down for 18 months. Any modifications or even rebooting of a critical control system are potentially dangerous, so those things are best not done with a plant running. It's probably not totally risk free even when shut down since cooling is still essential, but no-doubt they have extra people that know exactly what to watch for and have prepared. It's important that all plants be completely on top of any software vulnerabilities as well as normal issues. There may be a few hot-headed people in some other places about now.
Some huge military helicopters were seen headed the general direction of Diablo Canyon late last week.. The same type were seen when boric acid was picked up for use in Japan. Foreign news sources had also mentioned Japan dealing with France and South Korea as sources of boric acid.
They must be going through quite a bit of it and will until they can recycle coolant. Hopefully the 20 mule-team people or whoever are keeping adequate supplies available...
Hmmm... I bet radioactive coolant with boric acid in it would work great for getting rid of termites... or would they mutate? Someone should make more 50's style movies. Mutants from the sea raising sunken fishing boats...