Fukushima No. 1 loss of coolant due to earthquake 7

[trottiey]

I'm sure we're all anxiously waiting for some technically accurate news, so if you hear anything credible, please post it here.

Latest report that I have says that the reactor is shutdown, but coolant pumps are not running because of the power outage and failure of their auxillary generator. 2800 people evacuated - is that just the plant workers, or is that civillians? The government says there is no leak, but residents within 3 km of the reactor were told to stay inside.

The quake also caused a conventional fire and leak at the Onagawa plant. I bet you most of us on this list don't care so much about that, so please leave those reports off this thread.

Does anybody know how well these plants can thermosiphon?

 

[Hotown]

Here's the best breakdown of events I've seen yet:

http://www.world-nuclear-news.org/RS_Massive_earthquake_hits_Japan_1103111.html?je

And here's my personal favorite...

http://www.reuters.com/article/2011/03/11/us-japan-quake-nuclear-clinton-idUSTRE72A4LR20110311

I bet they're running out of internet as well, we better ship some of that over too!

 

[unclesyd]

Just crossing the news wire:
The pressure in the reactor is up 1.5 times the normal pressure.
The radiation is ?100? times the normal level.
The exclusion zone has bee increased from 6 to 10 kilometers.
None of the cooling towers are operating.

 

[rmw]

I tend to believe nothing that I read about anything technical for about the first 24 hours.

The evening news journalists are now discussing it as if they knew something about it. HA!

rmw

 

[vanmorrison]

http://www.iaea.org/press/

Regards,
Van

 

[trottiey]

Here's a summary of what I can figure out from sifting through conflicting news reports tonight:

The most affected unit is Fukushima Dai-ichi unit #1. It is a 460 MW BWR reactor built in the 1960's. Some news reports also refer to unit #2, but the reports are very conflicting about that.

There is lots of confusion among reporters between the containment structure and the pressure vessel. One of those is over twice its normal operating pressure and very hot. They are venting gas or steam, but it is unclear whether it is being vented from the coolant loop into the atmosphere, from containment into the atmosphere, or from the coolant loop into containment.

Radiation levels in the control room are 1000 times normal, but the reporters don't say if this is irradiation or airborne contamination, or what "normal" is. But the plant is now doing rapid shift changes, so that gives you some idea. One report said 250-500 mrem/hr.

The evacuation zone has grown to a 3km radius, and the stay-in zone has grown to a 10km radius. There are multiple reports talking about dozens of ships and hundreds of planes being sent to help the nuclear accident, but I'm guessing that's really just part of the general earthquake relief effort.

I've tried to trim out the speculative stuff, but it's still hard at this stage.

 

[OperaHouse]

I worked at one of those plants (Tokai 90 miles north of Toyko) during startup. It is probably not damaged but still in shutdown. These plants had their own ocean dock facilities for unloading heavy equipment. Plant is right on the ocean. Think of that with a giant wave. I remember a story that shipboard generators were used to start gas turbines during the big NYC blackout. One or more ships could be used to provide additional power to the nuclear plant.

Have been looking at those areal views showing the off gas towers. I climbed one to the top. I remember it being a white knuckle experience. Looks even taller now. That kind of prank would get me kicked out of the country today.

 

[unclesyd]

Here are bulletins from NISA that are updated ever few hours.
It gives status of each nuclear plant.

http://www.nisa.meti.go.jp/english/index.html

 

[Power2go]

There is much confusion in the press due to the information that "the plant is in battery controlled cooling mode" Running large cooling pumps on batteries is virtually impossible.

What really happens is that the emergency cooling system pumps are driven by the remaining steam from the plant. The motor operated valves in the system, and only those !, and the control systems are supplied from the batteries.(UPS systems)

When steam power runs out you will be in big trouble. That is why the emergency diesel generator sets must be back on line as soon as possible and the engineers at the plant are working hard on this.

 

[trottiey]

Unit 1 exploded. It was captured on video from a few different angles. Aerial photography confirms that the containment building is destroyed. Evacuation radius is increasing, and officials staying behind are in yellow tyveks. One Japanese report says there is radioactive iodine and cesium in the atmosphere.

There is still a stream of "experts" telling the news cameras that an explosion is impossible, that even the melting of fuel is impossible, and the media dutifully reports on it since every story must have two sides. But it sounds to me like the worst has happened.

 

[vanmorrison]

Does anyone know if it was the quake or the tsunami that took out the diesel generators?

 

[trottiey]

I think I can put some pieces together:
The earthquake hit at 14:46, local time.
World Nuclear News reports that the backup diesel generators started as planned, but failed an hour later.
A 10 m tall tsunami hit Sendai airport at 15:55 local time.
The Fukushami reactors are right on the coast according to Google maps, maybe 2-3 m above sea level.

So I would put money on the tsunami taking out the diesels.

 

[Zogzog]

Reports of the explosion is a H2 explosion, battery room I am guessing? Sort of fits in with the "cooling systems running on battery power" report.

USS Ronald Regan is headed over there and has the capability of providing power to on shore facilities. Wonder is that is the plan.

 

[trottiey]

The cooling pumps on a nuclear reactor typically take megawatts of power, well beyond the capacity of battery systems. I agree with Power2go's assessment above; they would have been running the valves on batteries, not the pumps.

Radiolysis in a nuclear reactor normally produces hydrogen and oxygen, which is continuously burned by electric recombiners. A number of possible failures could cause the recombiners to fail or be insufficient, resulting in accumulation of hydrogen. Hydrogen explosions are a common feature of nuclear meltdown scenarios.

They flew in more than enough generators a long time ago, but the problem is that you need a lot of copper and some fast electricians to run lines that can carry megawatts of power to the pumps. They did not succeed.

They say the reactor core vessel is intact, but it's a BWR, and I'm guessing some of the coolant piping is damaged. They say core pressure is decreasing, which would be consistent with a coolant pipe leak. The core vessel is in a containment well below ground level. A possible contingency in this scenario would be to flood the well with ocean water and boric acid. Some people speculate that the boric acid would be the "coolant" that Hillary Clinton mentioned.

 

[owg]

Thanks Trottiey for that helpful information. Does the hydrogen and oxygen produced contain any radioactive material? If so is it processed to clean it up before recombination? What normally happens to the water/steam that results from the recombination? Thanks.

HAZOP at

http://www.curryhydrocarbons.ca

 

[alehman]

Last report is they are flooding it with seawater and boric acid, as trottiey described.

Alan
“The engineer's first problem in any design situation is to discover what the problem really is.” Unk.

 

[trottiey]

Well, we're talking about coolant water here, water that flows over the fuel. So it will contain low concentrations of everything radioactive: particulates from the occasional broken fuel bundle, noble gases, activated corrosion products, activated anti-corrosion products, etc. It is typically poisonous for both biochemical and radiological reasons.

The hydrogen and oxygen itself gradually transmutes into radioactive isotopes by neutron capture while the reactor is running. The oxygen isotopes are all either stable or have very low half-life so they are not normally a health concern. The hydrogen isotope tritium has a half-life of 12 years, which is right in that sweet-spot that does the most damage if inhaled. But the tritium concentrations usually only reach hazardous levels in heavy water reactors, which the Fukushima reactor is not.

Tritium is lighter than air and floats away into space quickly, so fugitive emissions are normally not a concern. But if it recombines with oxygen or carbon, either through the explosion, fire, or just natural atmospheric recombination, the resulting water or hydrocarbon molecules are radioactive and easily absorbed into the body. There are regulations that limit how much that happens.

 

[davefitz]

trottiey:

"there are regulations that limit how much that happens"- I think we may be past the effect of regulations by now, at this particular plant.

If the end result is a large plume of cesium contaminating downwind countries , or some other drastic result, it could have a huge impact on food supplies, cost of food, and reconsideration of continued operation of other similar reactors ( and that is a lot of installed capacity !).

If nothing else good comes out of this experience, other plants will need to learn from this event, and be modified accordingly, if feasible.

 

[racookpe1978]

I am speculating here: Understand I would be wrong to claim that I "know" what happened. But I suspect that news reports that the containment building blew up are just plain dead wrong.

Wrote this on a separate, more political website for those (non-engineers) to read. Please extend your throughts.

Large amounts of Hydrogen - non-radioactive, regular but highly purified medium-pressure hydrogen gas at 35 to 50 psig - is used inside all of the medium to large generators worldwide to cool the inside of the generators from their electrical resistance to the 48,000 volt high-flow currents in the copper and iron. This hydrogen cooling system is supplied from large numbers of very high-pressure hydrogen bottle banks at 3000 - 3600 psig. (200+ bar, for you metric types.)

These hydrogen tanks are OUTSIDE the containment buildings - because they are non-radioactive and are a turbine building service system that does NOT connect to any reactor systems. The turbine, however, is lightly contaminated internally from residual particles deposited from the primary coolant because these power plants are boiling water reactors, and the turbines (not the primary coolant containment systems) ARE outside the containment concrete presssure-tight (blockhouse) domes.

If the high-pressure hydrogen tanks blew they would blow up like this (outside, with great dust blast and a sound wave) but the blast would NOT damage the reactor or the piping INSIDE the containment building. However, radioactive contamination to nearby injured workers is very likely. Any blast this size blows h*ll out of the turbine complex -> Ain't no power coming from this plant for a while.......

The small amount of hydrogen inside the containment dome that people were worried about at Three Mile Island WAS from decay and release of the melted fuel and decomposition of fuel element cladding. But the net pressure buildup from fission decay product gasses and this hydrogen inside the TMI dome was exaggerated at the time, and venting to relieve that pressure at TMI was the wrong decision by the government.

 

[electricpete]

I agree we don't know the source of the explosion.
I haven't actually seen reports of hydrogen.

Regarding potential sources of hydrogen in the core, normal hydrolisis is not a big concern, but there is a zirconium-water reaction at high temperatures which can produce hydrogen.

See page 2 of 3 here

http://canteach.candu.org/library/20044507.pdf

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(2B)+(2B)' ?