Japan Earthquake: nuclear plants

Just found this today.

"(Reuters) - The core at Japan's Fukushima nuclear reactor has melted through the reactor pressure vessel, Democratic Congressman Edward Markey told a hearing on the nuclear disaster on Wednesday.

"I have been informed by the Nuclear Regulatory Commission that the core of Unit Two has gotten so hot that part of it has probably melted through the reactor pressure vessel," said Markey, a prominent nuclear critic in the House of Representatives.

Originally Posted by Astronuc
FK-I Units 1-5 are MK I containment, but FK-I Unit 6 is Mk II.
Unit 1 is a BWR/3, Units 2-5 are BWR/4 and Unit 6 is a BWR/5.

Unit 4 containment is the advanced type (this is not necessarily the case of the other BWR/4 unit in the plant, and likely not the case)

Inside Fukushima Evacuation Zone

http://energheia.bambooz.info/index....mid=85&lang=it

Tetsuo Jimbo, founder of Video News Network, a TV broadcasting website, and a colleague ventured into the area on Sunday. Before setting out, Mr. Jimbo consulted a radiation expert, who advised he spend a maximum of two hours in the zone. The 49-year-old journalist stayed for two and a half. A face mask -- the kind worn to fend off hay fever -- was his only protective gear. He admits he and his colleague got "kind of scared" when a host of large dump trucks drove by and the drivers were covered in what looked like "full radiation-proof suits" and gas masks.

What this mean: radiation in drywell go from 30Sv (from previous nisa report) to 100Sv in newest report ?
source: http://www.meti.go.jp/press/2011/04/...10408004-3.pdf

If you are referring to the 1980's US mandatory Upgrade to Mark 1 design, I was stated on numerous occasion that Hitachi did implement those update on the Fukushima plant.

It look that N2 wasnt good idea... 100Sv wow, in Chernobyl, after explosion in reactor core was 50Sv...

If you are referring to the 1980's US mandatory Upgrade to Mark 1 design, I was stated on numerous occasion that Hitachi did implement those update on the Fukushima plant.

Nitrogen or earthquake ?

Temperature & Activity trend inversion looks simultaneous to N2 injection, which started 24 hours before the quake. (April 07 01h31 JST from Tepco)

100 Sv is what they had in Units #2 & #3 drywells on 15/18 March, now 3 weeks ago.

Thank you for the updated estimates. ZAMG:s upper boundary is still less than the total Chernobyl emissions of the same isotopes (from the great source of Wikipedia).

Yes, I know, I haven't seen any total estimations of emission of any nuclide directly to the sea. That is one of the reasons I myself dared the task.

Sorry, I may not be able to update my plots of Fukushima Daiichi vars until next tuesday.
(However the scripts and files are availabe at the site, if anyone cares...)
http://www.ic.unicamp.br/~stolfi/EXP...ima/plots/cur/

Concerning the discussion as to possible explosion paths or visible damage to unit 4.... Astronuc and Fred appear to have differences of opinion as to the containment types.

You are a new poster here and i understand you havent gone over the thousands of posts. All the things you mention were discussed here a while ago and debunked basically.
Reactor 3: The big blast is not directly related to the destruction of the top parts of the reactor, there were images posted here that show it's still there, with a crane collapsed over it, and steam escaping from the connection chute between that and the SFP. Also notice that the truss structure over the containment is intact unlike over the SFP. The thermal imagery, somehow surprisingly paints a rather rosy picture, with nothing substantially warm. A lot of seemingly hot spots arise from changes in the range of the IR measurements, with debris lying around at essentially ambient temperature. There are hot spots (70degC) over the SFP and the leaking parts from the PCV but that's about it, the rest are more or less cooler than a human being (less than 36degC), if a person was there it would be glowing red.

Broken pieces of fuel rods have been found outside of Reactor No. 2, and are now being covered with bulldozers, he said. The pieces may be from rods in the spent-fuel pools that were flung out by hydrogen explosions. Looks like we where right about fuel rods blown out of spent fuel pools .

What exactly has been implemented? Do you have links?

One of the things I am watching is how we are getting information and how reliable sources are. Can you tell me what posts and sources contained that info?

All of the modifications were made in accordance with regulatory requirements. In the United States, for example, the NRC issued a generic industry requirement in 1980 for the Mark I containment that the industry used to make modifications.

We understand that all of the BWR Mark I containment units at Fukushima Daiichi also addressed these issues and implemented modifications in accordance with Japanese regulatory requirements.

The modifications made to Mark I containments include:
“Quenchers” were installed to distribute the steam bubbles in order to produce rapid condensation and to reduce loads on the unit. In a reactor, exhaust steam is piped into a suppression chamber, which is known as the torus and is a large, rounded suppression pool that sits next to the reactor core. It is used to remove heat when large quantities of steam are released from the reactor. In the torus, the steam bubbles go under water. With the modification to the Mark I, the quenchers, which are also underwater, make steam bubbles smaller by breaking up the larger bubbles. This in turn reduces pressure.

Another modification is the installation of deflectors inside the torus. When that steam goes in, the water level rises. The deflectors that were added break up the pressure wave that is produced and help relieve pressure on the torus.

A further modification was made to the “saddles” on which the torus sits — basically the series of leg-like structures that support it. The con