Earthquake off Japan

[The Duchess of Zeon]

There was a release which said that there is a partial loss of containment at reactor 2. Or is it revised?

There was a loss of coolant – that's what allowed the core to be exposed to air and partially melt. They have now added more water. Everything is still inside the containment building.

So this one was a false alarm?

http://www.bbc.co.uk/news/science-environment-12745186

No, it's a moron. The torus may be breached but the torus is still inside the sealed lower levels of the containment building. Do you seriously think that reactor facilities are built without internal subdivision? Just because the top of the building is gone doesn't mean that the bottom isn't intact, and there's a huge concrete plate below it additionally. Further the containment dome structure around the reactor vessel is further integrated into the sealed base of the reactor building. There is a possibility of limited local ground contamination from seepage, but that's happened at many places like Hanford before and while unpleasant and contaminating of an area, is not seriously threatening to human life even in the long term.

[phongn]

News from a nuclear engineer over on ArsTechnica:

Apparently the Fukushima plants were never retrofitted after TMI with filtered containement venting capability. The only thing that they have is a pressure relief line with a manual valve dating back to the construction period that empties into or past (not sure) the spent fuel pool.

Additionally, a partial answer to the question on why the turbine didn't work:
The turbine needs electric power to open its solenoid controlled valves. And battery power for this only lasts approx. 8h. As a first action within mere months after TMI, all plants in Europe were retrofitted for these valves to be manually operable. Additionally, battery capacity was increased to 96h (don't know if this is due to the lower load, though).

Once you lose the turbine, all steam from the core is dumped into the now uncooled spression chamber. The 2100m^3 of water = 2.1*10^6kg. Heating it all up to saturation point needs roughly 4.2MJ. At t=9 hours after shutdown Fukushima 1 produces 11MW of decay heat, Fukushima 2+3 produce 20MW of decay heat. Within 10h for Fukushima 1, and 6h for Fukushima 2+3 the suppression pool will then reach saturation temperature and the water within has become un-pumpable. Additionally, a back-pressure within the suppression chambers will build up, preventing the turbine from operating!

So if for whatever reason the RCIC turbo pump fails, one has exactly 6 or 10 hours before everything goes totally pear shaped in these plants.

As far as I am informed, though, the RCIC pump failed in units 2+3 because the turbo-pump performance was too low to pump enough water through the isolation condenser. The water temperature within the suppression chamber reached more than 100°C, which meant that the firewater being pumped through the isolation heat exchanger started boiling within the isolation heat exchanger, producing a strong back-pressure that made pumping firewater through it impossible.

[Broomstick]

Because pictures speak louder than words, I am going to post what a melted nuclear core looks like, well, one of them at least. This is the "elephant foot" at Chernobyl. This is the gunk that melted from the intense heat in the reactor and went through the floor of the reactor into the basement. My apologizes for the picture quality, but radiation does fuck up film and video when it's as intense as it is in that environment.



Now keep in mind, Chernobyl was FAR worse than Fukushima. Regardless, it solidified in place and hasn't gone anywhere since then. You wouldn't want to stand next to it, but it's not crawling out of its hole and going anywhere, either.

This is as bad as a meltdown gets. Fukushima will not be as bad as this, ever. Unfortunately, I could not find an image of the TMI core meltdown results, but they probably weren't as bad, either.

[Enigma]

I would not be surprised, once everything is more or less settled down, that TEPCO will be facing a class action lawsuit plus some high level investigations from the government leading to massive fines and arrests? I would also not be surprised if one or two TEPCO executives commit suicide over this fiasco.

[Justforfun000]

There have been calls to stop the building of new nuclear power facilities in Ontario because of this disaster in Japan. As usual, people jump on the bandwagon and assume what applies in one situation is equally applicable somewhere else.

Ontario is not subject to serious earthquakes and tsunamis, and even if we were, the CANDU reactor system is vastly different from the other nations - safe, reliable and not capable of meltdowns like their reactors. They fission natural uranium, not "enriched" uranium, and the newer CANDU 6 and ACR-1000 designs are much more efficient, safe and cutting-edge.

I don't know how similar Germany or any other countries are to Japan...

[Nephtys]

I didn't see this mentioned anywhere yet in the thread, but the fuel pool fire at reactor 4 was extinguished about 14 hours ago.

Units 1 and 2 are permanently done, but number 3 is not. Basically, crisis over.

[Broomstick]

Well, not quite - reports are the work crews at the plant have been reduced to a skeleton crew of volunteers. Basically, they're people risking lethal doses of radiation to finish bringing this under control and cleaning up so the next crew will be safer. They might even be people who have already received lethal doses volunteering to finish the job. Naturally, everything that can be done for them medically will be, but they are risking their lives for others, and that makes them heroes.

But, bottom line, despite breathless reports to the contrary in the media, yes, this particular part of the crisis is winding down.

[Tribun]

Please correct me if I'm wrong.

So right now it looks like this:

-The reactors are a total loss and can only be scrapped.
-Right at the moment the situation is bad but not catastrophic. (however, I dare no predictions. This nuclear plant is now pretty much an unknown and can react unpredictably.)
-The area directly around the plants is "hot" (meaning lots of radiation).
-The storage bassin of reactor for has become a huge headache because water supply is difficult and the temperature is rising.

Is this basically it at the moment?

[Sephirius]

Unfortunately, I could not find an image of the TMI core meltdown results, but they probably weren't as bad, either.

[Illuminatus Primus]

http://upload.wikimedia.org/wikipedia/c ... ration.jpg

The TMI-2 fuel-containing mass was, unlike Chernobyl, confined to the primary containment.

[Terralthra]

Chernobyl didn't have primary containment.

[Zixinus]

-The reactors are a total loss and can only be scrapped.

From what I get: Only reactor 1 and 2 has to be scrapped. I am unsure about reactor 3.
The rest are OK.

-Right at the moment the situation is bad but not catastrophic. (however, I dare no predictions. This nuclear plant is now pretty much an unknown and can react unpredictibably.)

It is not an unknown: they have cooled down reactor 1 and 2. However, they are still struggling to cool down reactor 3.
Once that is done, Fukushima will be under control.

-The area directly around the plants is "hot" (meaning lots of radiation).

Plant. Singular.

Yes, there is mild radiation in the plant's area. The reactor itself is not breached however, only some coolant water got out that may have also brought radioactive materials with it.
These materials, if I understand correctly, will decay within a few days or weeks and then will be inert (ie, not radioactive).

-The storage bassin of reactor for has become a huge headache because water supply is difficult and the temperature is rising.

No, that is not the case.

What is happening is that even though the reactor has been shut down, it is still producing heat. This is what reactors are supposed to do and it is not as easy as it sounds to cool down a reactor.
Due to damage from the earthquake, the plant crew are having trouble cooling the reactor down. The last few days' worth of trouble has been due to this.

Temperature is NOT rising because the reactors have been shut down. Water is not an issue. Electricity to get the pumps to cool the reactors is the problem.

[Magis]

The torus may be breached but the torus is still inside the sealed lower levels of the containment building.

While I am not extremely familiar with the particulars of the Fukushima design, the suppression pools in GE BWRs are typically located below the core and outside containment, and in fact play a roll in the containment over-pressure safety system.

And for clarification, when I say "containment", I mean primary containment.

[starslayer]

It is not an unknown: they have cooled down reactor 1 and 2. However, they are still struggling to cool down reactor 3.

All three are in cold shutdown according to the IAEA. As Nephtys mentioned, the spent fuel pond fire is out, and lasted only two hours. Barring any future incidents like the fire, the Fukushima incident is basically over.

[Magis]

Now according to the Japan Atomic Industrial Forum, there is a suspected loss of integrity of primary containment of unit 2.

[Tribun]

Now according to the Japan Atomic Industrial Forum, there is a suspected loss of integrity of primary containment of unit 2.

Enlighten me how bad this is. Ther terminology and some translation troubles sometimes mean I don't understand what this exactly means.

[Broomstick]

If I'm understanding correctly that's not news, it's how the coolant leaked out (i.e. escaping steam). The Bad Stuff(TM) is still confined, as intended, and not getting out into the environment.

[Exonerate]

It is not an unknown: they have cooled down reactor 1 and 2. However, they are still struggling to cool down reactor 3.

All three are in cold shutdown according to the IAEA. As Nephtys mentioned, the spent fuel pond fire is out, and lasted only two hours. Barring any future incidents like the fire, the Fukushima incident is basically over.

Not quite. IAEA says Fukushima Daini is in cold shutdown, not Fukushima Daiichi.
The situation according to the latest update from Japan Industrial Atomic Forum is:
Fuel integrity of Unit 1 and 3 are confirmed to be damaged, Unit 2 unknown.
Containment integrity of Unit 1 and 3 are fine, but Unit 2 unknown. Possibly related to the explosion earlier.
Fuel inside Unit 1 and 3 are 50% submerged, while Unit 2 has already dried up completely twice. They're currently trying to get it re-submerged.
Sea water injection to core is continuing for all three units. My educated guess is that there's still residual heat being generated by all three units, or else they wouldn't need to keep actively cooling it down.

Right now the reactor with the biggest problems is definitely #2. Unless I'm mistaken, the combination of damaged fuel cladding and containment breach means a possible release of radioactive material directly into the environment. There's also been reports of difficulties venting, which not only prevents the removal of heat from the reactor, but also keeps the pressure inside high, which complicates the seawater injection.

[Broomstick]

Sea water injection to core is continuing for all three units. My educated guess is that there's still residual heat being generated by all three units, or else they wouldn't need to keep actively cooling it down.

It would be downright peculiar if there wasn't residual heat - cores typical take several days to a week to cool down to ambient temperatures even under the best conditions.

Right now the reactor with the biggest problems is definitely #2. Unless I'm mistaken, the combination of damaged fuel cladding and containment breach means a possible release of radioactive material directly into the environment.

There are multiple levels of containment - while the breach of any one of those units is a serious matter it would have to go through more than one to reach the external environment. A lot depends on how many have been breached, but my impression is that it's only been one so far.

There's also been reports of difficulties venting, which not only prevents the removal of heat from the reactor, but also keeps the pressure inside high, which complicates the seawater injection.

This is also what I'm hearing.

[The Duchess of Zeon]

Now according to the Japan Atomic Industrial Forum, there is a suspected loss of integrity of primary containment of unit 2.

Correct.




Observe the design of the reactor, however. Damage to the torus is still fully contained within the concrete sealed basement of the facility. In short the radioactive material is confined within secondary containment, because even despite the upper part of the building being destroyed the surface-level concrete floor seals in the concrete lined basement containing the torus.

[Exonerate]

Sea water injection to core is continuing for all three units. My educated guess is that there's still residual heat being generated by all three units, or else they wouldn't need to keep actively cooling it down.

It would be downright peculiar if there wasn't residual heat - cores typical take several days to a week to cool down to ambient temperatures even under the best conditions.

Residual heat is not the same as residual heat generation. As the isotopes decay, heat is also released, and if the cooling doesn't remove heat at least as quickly as it is being generated, the overall temperature rises. If there was no heat generation, (I'm guessing) they could just seal everything and let everything cool down on its own and call it a day. The fact that they're still actively venting the steam and trying to pump more seawater in likely means there's still significant heat being generated. To stretch the boiling pot analogy you used a few pages back, we're using an electric stove - while the power has been cut, the coils heating the pot are still hot, so the pot's overall temperature is still rising.

There are multiple levels of containment - while the breach of any one of those units is a serious matter it would have to go through more than one to reach the external environment. A lot depends on how many have been breached, but my impression is that it's only been one so far.

Right. The fuel pellets are encased in zirconium alloy (cladding), which is placed inside the reactor, which makes up the first layer of protection. Then there's the reactor itself and two layers of containment surrounding it. Finally, there's the building. The cladding is confirmed to be melted in reactors #1 and #3, and its status in #2 is unknown. The building is also damaged from the explosion. That leaves the reactor itself and two layers of containment. There is where the JAIF gets ambiguous and lists "Damage suspected" for containment integrity. Which of the two layers of containment are they talking about? Does this include the reactor vessel itself? I don't know, but if all five layers become damaged, then direct release becomes a possibility.

[somnick]

I have a question that some of you might be able to answer.

What would have happend if nobody would have done anything?

I mean: reactor shuts down, cooling fails immediately after and for some reason no staff is around to handle things (lets say its the Stephen King Flu).

From what I understand any remaining water turns to steam and meltdown starts. Would at that point, whithout venting, the pressure rise high enough do crack the containment (primary or all of them)? If so would this happen explosively or more like valves popping off and the reactor "venting itself"? Then eventually the puddle of molten fuel would melt through the bottom of the pressure vessel.
Would the residual heat, whithout any cooling, be enough to get through the floor? The decay heat generated is finite so it should be possible to determine a floor structure thats thick and wide enough to catch the molten fuel for sure, right?
Have the done that?

I mean, that way the reactor would be essentially fail safe, even when everyone turned off the lights and left, if you only install some ordinary passive over pressure valve.

Or is the energy from the decay whithout cooling so insanely great that it's impossible to put enough concrete under the floor?

I assume it's not that simple, so what did i miss?

[Tribun]

Reactor 4 is again on fire. Word is of huge flames and thick smoke.

[Zixinus]

Question: I understand that a reactor has two water-cycles: one that is purely internal and what actually meets with the reactor itself. This water only leaves the power plant in a controlled manner (ie, as nuclear waste)
The second only indirectly meets with the first and it is what is actually used to generate power. This water leaves the plant regularly.

Do I understand correctly that essentially the first water-cycle is the one that has been blown up with reactors 1 to 3?

[The Duchess of Zeon]

Reactor 4 is again on fire. Word is of huge flames and thick smoke.

Yes, and TEPCO has lost the ability to pump water into the fuel pool. The uranium fuel rods defueled from Reactor No.4 are now directly on fire and spreading radioactive particulate matter into the atmosphere. The building has also been damaged and is at risk of collapse, and it's said that two workers are missing, though that might have been from the earthquake. It's exactly like Windscale, the air-cooled reactor fire in the UK in the early 50's, except without any filters on the stacks, which were the thing that saved Windscale from being a major catastrophe. If the building collapses there will be no way whatsoever to stop this as burning uranium is spread through the building. All they can do now is order men into open a hole in the reactor building, and bring fire-trucks directly up to spray seawater onto the pile, or else send many teams of men rolling hoses (may be necessary since the building is already weakened) to spray water directly onto the fuel.

The good news is that in full NBC gear this should be theoretically survivable because the danger is--unless there has been a criticality accident--radioactive particulate matter, which is only dangerous when inhaled, and not ionizing radiation, which can only be lead-shielded against. If there has been a criticality accident, they are kamikaze.