Live Thread- Fukushima Reactors

[hc87]

Live Thread for March 16, 2011. Please post Fukushima reactors stories here.

[CarryaBigStick]

Thank you for the additional info. I was going from (poor) memory.

[GonzoGOP]

Here is the graph from yesterday's post. It looks like it starts off around 7% but then drops off rapidly to less than 1%. We are five days out so we are probably around half a percent of total heat. Also from the earlier post that puts us at around 2-2.5 MW of heat being produced by each reactor.

So can they get enough water in there to boil off 2 MW of heat. If so this will just be a monstrously expensive cleanup. If not then thing will be a bit more problematic. Not world ending disaster, but the cost goes up dramatically with the radius of the contaminated area.

[RedhairRedhair]

Unit 1 - 460 MW
Unit 2 - 760 MW
Unit 3 - 760 MW - MOX Fuel
Unit 4 - 760 MW
Unit 5 - 760 MW
Unit 6 - 1067 MW

[Nobel_1]

Reactor status with Q&A and risk scenarios: http://www.zerohedge.com/article/reactor-status-update-and-fukushima-risk-qa

Status chart:

[Dubya-M-DeesWent2SyriaStupid!]

Pictures

http://www.dailymail.co.uk/news/article-1366670/Japan-earthquake-tsunami-Radiation-soars-Fukushima-nuclear-plant.html

[SargeK]

I think you’ll find those are the MWe output ratings for the units.

[NonValueAdded]

I think the issue here is "shut down" is no longer the operative term. Shut down means that the reactor vessel is completely intact and the control rods fully inserted with the core completely covered. I believe also implicit in the definition is that sufficient cooling is taking place. Let's refer to that as complete reactor integrity. And that has nothing to do with the spent fuel storage issue but more on that in a moment.

Once complete reactor integrity is breached, the cool-down-over-time factor is no longer operative. Eventually the heat will compromise the integrity of the rods, the precise geometric relationship between the fuel and control rods is lost, and you are on your way to a melt down. There are remedies including the boron injection, which is an attempt to make the water surrounding the failing rods into a control rod equivalent.

We are told that in the event of a meltdown, the mass will pool at the bottom of the 3rd stage containment building, spread out and naturally cool over time. Radiation will be emitted but particles will not. And that's the good news!

Someone posted a cutout diagram of the BWR when the discussion was about losing the first sacrificial roof of the outer containment structure (3rd level containment). At the time, I and a few others saw the spent fuel pools situated well up in the structure and asked the question "what about Bob?" Well, that is turning out to be the billion dollar question.

The spent fuel pools are uncontained and subject to all the problems occurring outside the pressure vessel that is doing its level best to keep the unspent fuel rods in their shut down status. Fire in the 3rd containment - did I say that meant the 4 walled structure around the reactor, the ones that lost their roof - might not hurt the first two containment structures but the unprotected spent fuel pool? Oh mama, there's the problem and we've heard precious little about that kettle of neutrons.

I am not a nuc nor did I sleep at a Holiday Inn last night. I am remaining clam but am more than a little concerned that not enough people see the elephant in the outer containment zone. I pray that the folks on the ground see it but are too busy to talk about it.

[mrsmith]

http://www.jaea.go.jp/english/misc/online-info.shtml

Radiation monitoring online.

The O-Arai location is, as best I can tell, halfway between the plants and Tokyo.

Units are Zgy/hr- don’t know what the “z” means.
“Last measurement collected 2011 March 16 20:00” as of this posting.

[GonzoGOP]

With a loss of core structural integrity, loss of the geometry, loss of moderator control, I’m not sure we can calculate with any degree of confidence how much heat the plant will produce in its current state, at least not without a lot of data that even the plant operators themselves are struggling to determine.

Look at it as best case analysis. They have to dissipate at least .5% of the heat the reactor was rated at. On a 760 MW reactor that would be 3.8 MW that needs to be dissipated. That is not an insubstantial amount of heat, but is it enough to melt through a containment vessel. Those things are fairly tough and built to take a lot of heat.

[palmer]

Here's a link regarding potential harm to humans: http://www.merckmanuals.com/professional/sec21/ch317/ch317a.html#sec21-ch317-ch317a-605 It doesn't answer your specific question, but at the peak reading from yesterday (400mSv/hour) there is 20% increased risk of cancer from 2.5 hours of exposure plus up to five percent chance of death from radiation sickness from anything longer than that.

[VanShuyten]

Apparently, the helecopters just dump lots of water at once, just like when they are used to fight forest fires. The concern was that such a sudden dump would produce a blast of radioactive steam that would affect the flyers. In addition, they were worried about additional damage done by dumping lots of water on top of the pools.

They want to pump water in using firetrucks so they can control the rate better and avoid any of that.

[mrsmith]

Ah!

“This environmental radiation which ORDC measures is the airborne radiation in units of nGy/h (nanograys per hour). The airborne radiation level around ORDC is generally measured to be 30 - 40 nGy/h. “

Latest readings are in the 600 to 700 nGy/h range.
Wind is from the dirction of damged plants.

http://www.jaea.go.jp/04/o-arai/Oantai_e/html/tbl_msr1h0.html

[paulycy]

Is there a map showing the areas of Japan that are effected by radiation? As in how far it has spread? This would be useful for travelers.

[mn-bush-man]

It’s always hard to interpret numbers. A 20% increased risk of cancer... so if, prior to exposure, I had a 5% risk of cancer, would I have a 6% risk of cancer post-exposure? That would represent a 20% increase. Not to minimize significance... but that doesn’t seem abundantly significant.

[jpsb]

That is a nice graph, my problem is, I do not know what to believe. The fuel rods melt at 2,000C and they are melting. Even the spend rods are melting so I am thinking that the wiki, which says, this type of reactor requires years of active cooling (see pros, cons) might in fact be correct and those saying it will cool in a few days or even a few weeks are incorrect. But I really do not know so I was hoping someone, an expert, could provide us with a few basic facts on cooling.

Thanks for the reply, it would be nice if all this would go away on a few days, but somehow I don't think that is very likely.

nuclear reactions of the fission products continue to generate decay heat at initially roughly 7% of full power level, which requires 1 to 3 years of water pumped cooling. If cooling fails during this post-shutdown period, the reactor can still overheat to above 2200 degrees centigrade where separation of water in to its constituent elements Hydrogen and Oxygen occurs.

http://en.wikipedia.org/wiki/Pressurized_water_reactor

[Justa]

“I saw a thread last night about the reactors being in cold shutdown.”

There are two sets of power stations. That was about power station #2 and its reactor plants. The problems are at power station #1’s reactors.

[NonValueAdded]

Yeah ... the fuel integrity in the spent fuel pool line in the spreadsheet goes back to your post 65 on your Forensic Analysis Of Events At Fukushima Nuclear Plant thread. Sucks to be right, doesn't it?

[CarryaBigStick]

I see the point you were trying to make. I forgot the energy losses associated with converting the steam energy mechanically to electrical power with the turbines. The chart in post #24 shows the direct thermal output of the individual reactors (in megawatts) before electrical generation.

[a real Sheila]

“The used fuel pools at the Fukushima Daiichi reactors are located at the top of the reactor buildings for ease of handling during refueling operations.”

am I understanding correctly that spent fuel rods were stored in the tops of these containment buildings? Are these the same buildings whose roofs have been blown off by explosions? Have the containment rods blown out along with the roofs?

If so, what a cluster!

[P-Marlowe]

Radioactive fallout downwind is scary stuff.

we are half a planet away from any of that fallout. I would be much more concerned if I were downstream from a hydro electric plant.

There really is no effective way to generate energy that does not involve a danger to the public. It is an acceptable risk inasmuch as the alternatives are going to more deadly in the long run.