Neomom notes that this is a good site for nuke news.
...there is a fire at Fukushima Daiichi 4 that is accompanied by high levels of radiation between Units 3 and 4 at the site. The fire began burning at Unit 4 at around 6 a.m. Japan time on March 14 and is still burning. Fire fighters are responding to the fire. The reactor does not have fuel in the reactor, but there is spent fuel in the reactor (pool) and Edano said that he assumes radioactive substances are being released.
It appears that this reactor was down for refueling or something. The spent-fuel pool is releasing radiation at about 40 rem/hour, which is on the high side. (Background, or 'normal' is around 130 millirem).
I'm still having an awfully hard time understanding whether the containment vessel is breached. Some stories mention possible damage to the containment system, but other suggest that what they mean is some kind of damage to the associated toroidal cooling pipe, and I can't make out whether that portends a leakage of the melted fuel in the core or not. I'm guessing not, since the radiation levels aren't high enough; this is no Chernobyl. Can someone here help?
ReplyDeleteFrom what I've been reading this week, Chernobyl was horrible because there was literally no containment. TMI had a containment, and only 5/8 of an inch of a six-inch-thick steel wall melted during a halfway-meltdown. So it seems that no containment vessel has ever melted down. On the other hand, it seems that the biggest meltdown so far was a halfway melt. Is that right? Is there any reason to suppose that there's some kind of linear connection, so that a full meltdown would chew through only twice as much thickness of a containment vessel wall as a half-melt?
I'm still having an awfully hard time understanding whether the containment vessel is breached
ReplyDeleteInfo I've read states that the POOL 'containment' was breached. Thus, the water drained from the pool (which housed the spent fuel) and the rods began a melt.
That accounts for the higher-level radiation release AND the 'drop in pressure' in the pool-containment building. If there's a hole in the pool, then pressure will be released.
Further:
ReplyDeleteThe plant was designed so that IF there is a "last-ditch" problem with the actual reactor-vessel, the radioactive material will still be contained in the primary facility. It'll be laying on the concrete floor which is a buncha thick (scientific, eh?)
Still no "Catastrophic Release" of radiation. Ugly, messy, won't be fixed for years, but ....
That sounds right, and I just wish the reporters and the people they're talking to could be a little more clear about what's breached and where, especially since sometimes they seem only to be guessing about what and where the damage may be, until they can get in there and check.
ReplyDeleteThat burning pool sounds like seriously bad news. Who would ever have thought that could happen? If someone had said they ought to have a contingency plan for that, I'd have said they were nuts.
There are two problems:
ReplyDelete1) Japanese speak in Japanese, not English.
2) Techno-babble in ANY language is hard to decipher unless one's "in the industry." E.G., while I kinda know how email travels, I have no friggin' idea of "octets" and where they belong in the chain.
Zero Hedge had a link to a site I'm finding helpful:
ReplyDeletehttp://www.physicsforums.com/showthread.php?t=480200&page=11
Someone's carefully moderating the site and promptly answering questions. The host says that Cesium and Iodine can easily get into the coolant if the fuel rod cladding is degrading, such as by excessive heat. So that would indicate that the containment might be completely OK, but there is still going to be a problem with contaminated steam until the cool-down is complete. Not a Chernobyl-sized problem by many orders of magnitude, but no picnic, either.
Several people have asked for confirmation that melted down fuel can't go critical again, and the answer is, no, it cannot. The geometry and moderating elements are all wrong for it. Certainly at TMI there was a partial meltdown without any tendency at all to go critical again, so that's good to hear.
The bigger problem right now seems to be from the suppressor pools containing spent fuel at the cold unit. I was impressed that one contributing commenter had predicted that problem a day or two before it hit the news.
Couple of things... the spent fuel pool was not the fire at Unit 4 - it was from leaking oil from a pump. We have a guy on site there that confirmed.
ReplyDeleteUnits 1 and 3 are now as stable as they can be and are being cooled with sea water. Every hour that gets better since the fuel rods don't start reacting and reheating without a kick start from a substance like Californium.
Unit 2 seems to be the problem child. If you look at the cutaway graphic on the NEI site... the "donut" at the bottom is the Torus - the pipes coming from the reactor in the middle are the toroidal steam pipes. If the torus or steam pipe was damaged, it is still inside the concrete/steel containment structure. If water levels are rising in the reactor and radiation levels are falling per the most recent NEI update, that indicates that the concrete/steel containment wasn't breached.
Units 1, 2, and 3 are dead. The sea water finalized that. But look at the graphic of where these plants were from the epicenter. These 40 year old reactors did not fail from a 9.0 quake. They SCRAM'd as planned and stopped reacting immediately. They performed exactly as designed - even better considering the magnitude. The issues are due to the backup diesels and a tsunami that breached. If those diesels hadn't been swamped, we wouldn't even be having this discussion.