ScribbleLive

@Nancy - yes and it is now being picked up again.

Fukushima reactor water leak risks delaying crisis plan www.reuters.com ""There must be a large leak," Junichi Matsumoto, a general manager at the utility also known as TEPCO, told a news conference.

"The fuel pellets likely melted and fell, and in the process may have damaged ... the pressure vessel itself and created a hole," he added.

Since the surface temperature of the pressure vessel has been holding steady between 100 and 120 degrees Celsius, Matsumoto said the effort to cool the melted uranium fuel by pumping in water was working and would continue.

Based on the amount of water that is remaining around the partially melted and collapsed fuel, Matsumoto estimated that the pressure vessel had developed a hole of several centimeters in diameter.

I wonder what the definition of "partially melted" is. Does anyone actually believe that there's anything that hasn't dropped to the floor of the RPV?

This is a clip from that Telegraph article: "Greenpeace said significant amounts of radioactive material had been released into the sea and that samples of seaweed taken from as far as 40 miles of the Fukushima plant had been found to contain radiation well above legal limits. Of the 22 samples tested, ten were contaminated with five times the legal limit of iodine 131 and 20 times of caesium 137.
Seaweed is a huge part of the Japanese diet and the average household almost 7lbs a year. Greenpeace's warning came as fishermen prepared to start the harvest of this season's seaweed on May 20."

Of course, they've been pouring in a really, really, large amount of water, for some time now, and they acknowledge a hole, and they haven't found the water anywhere, and...

"Matsumoto estimated that the pressure vessel had developed a hole of several centimeters in diameter." - er that would be 3cm no maybe 30cm er ...

Good morning Scribblers, very happy to see you all here. I recorded the "black fog" through the night, and will review it later today, don't expect to see anything. I have to go meet up with Tenzing this morning for coffee. The news posted below comes as no surprise, it is heartbreaking and scary all mixed together.

Environmental activist group Greenpeace said Thursday it had detected radiation far above legal limits in seaweed samples taken from the ocean off Japan's stricken Fukushima nuclear plant.

Greenpeace, which sent its Rainbow Warrior flagship to take samples of marine life and water, called on Japan's government to undertake comprehensive radiation testing of seaweed along the Fukushima coast. www.asiaone.com

@Nancy thanks. @Debra Beckham good morning

At least the one #1 RPV pressure gauge reports about 14 atmospheres, call it 200 PSI, while the other gauge is reporting maybe 80 psi equivalent, so any holes should be pushing water at a healthy rate.

Guess it actually is self-venting. I wonder if there's a combination play, both an actual melt through plus failed penetration seals.

What size stuff gets out depends on if there are clean holes vs. narrow cracks.

In the latest #1 pressure figures, ayone any idea what 'D.S' means in the first measurements column (Water level in reactor @ fuel level A according to @bo's translation)

@bo - please could you ask your colleague to have a look at the notes on the right hand side of page 3 of this doc www.tepco.co.jp opposite the first 'D.S' entry?

@bo - thanks. Probably means 'core disappeared at this point'

Pretty sure that the comment is that the sensor is under calibration. Google Translate says "Water level meter (A), and D / W Pressure 力計(PR-1602-16)の校 Power meter (PR-1602-16) in school ", consistent with the NISA reports saying "under calibration".

@Markfm - since 1100 on May 10th when the water level reading disappeared? How about D.S in place of blank entries?

Fine Time to Die Alos, Disaster Monitoring anyone -"ALOS, launched by JAXA in January 2006, carried visible, infrared, and radar instruments to provide imagery and other data for mapping and disaster monitoring." www.spacetoday.net

I still don't get the 55% destroyed on #1. Given the water level is 1 meter below the bottom of the rods, wouldn't they melt all the way? These were "hot" rods, from an active plant. Ahh, well, hopefully Dean will provide his insight when he pops in.

@RBeaner "The Advanced Land Observing Satellite (ALOS), also known as Daichi, went to a safe mode on April 22 when the spacecraft's solar panel stopped generating power. Efforts to restore power failed, and on Thursday controllers sent commands to the spacecraft to shut down its transmitter and drain its batteries, effectively ending the mission."

And my broken jukebox of a mind kicked in with "You picked a fine time to leave me, Lucille..."

Scientific American spoke with Scott Burnell, public affairs officer at the U.S. Nuclear Regulatory Commission (NRC), the government agency charged with monitoring the safety of the 104 nuclear reactors in the U.S., about what it takes to cool down a reactor.

[An edited transcript of the interview follows.]

How do you typically cool a reactor?
The approach to cooling is very simple: push water past the nuclear core and carry the heat somewhere else. The chain reaction that actually runs the reactor can be shut off in a matter of seconds. What's left over in the core, the radioactive material, will continue to give off heat for a long time. Unless you have a mechanism to remove that, the heat can build up and can eventually damage the radioactive fuel or the reactor.

Pushing water past the core means pumps that are generally run by electricity. What happens when a reactor gets disconnected from the grid?
There are emergency diesel generators. You also have a battery system to keep instruments running, but that can also provide power to safety systems [which prevent a meltdown by cooling the reactor core]. It's all meant to provide defense in depth. First you rely on the grid. If the grid is no longer available, you use diesel generators. If there is an issue with the diesels, you have a battery backup. And the batteries usually last long enough for you to get the diesels going.

How much time is there before a meltdown?
It depends on the plant. It depends on whether it's a boiling-water reactor or a pressurized-water reactor. Basically, [in both] you have the benefit of natural forces such as convection. There is a coolant loop no matter what, so you end up to some degree cooling the core because the heated water rises and colder water gets pulled in. But that's not as effective as a pump bringing in cool water. Just to speak very broadly, you have many hours to restore power to the system to get normal cooling going. It's really not possible to get more specific than "many hours."

But generally, less than 24 hours.
That's fair to say.

What's the worst-case scenario?
The event we are looking to avoid is damaging the core. Once you start damaging the core, you are then releasing radioactive material into the coolant and thereby increasing the chances that something travels outside the reactor
www.scientificamerican.com Article was written March 11, 2011 and the interview followed the article.

@radioguy - I guess that is the answer to the question of why there was no good satallite pictures of the disaster and the drones had to be brought in...