How will things turn out w/reactor No.3? Chose how far it goes

[flamingdem]

What is your choice for how far this plays out? Is this scenario realistic?


An analysis:
Apparently all the control rods were activated shortly after the earthquake thus stopping around 97 to 99 percent of the fission reactions and thus most reactor heat output. (The good news!)

It's the residual heat (low fission) emitting from the fuel rods and the inability to cool them that is causing the current problems.

The water levels inside the pressure vessels are falling which causes the exposed fuel rods to heat further creating higher pressures, temps and thus corrosive steam

As the temps increase the zircaloy casing on the fuel rods starts to deteriorate both through oxidation (at temps above 600 celcius) and complete zirconium hydrogenation to the brittle hydride at around 800 degrees celcius.

http://www.scientific.net/MSF.561-565.1765

The deterioration and embrittlement of the zircaloy clading at elevated temperature will eventually release the sintered ceramic uranium pellets held within which will then collect at the bottom of the reactor vessel.

And since the fallen uranium/MOx pellets will have not have the benefit of the boron impregnated control rods to stop the fission reactions...

Fission reactions will start again creating enormous amounts of heat that will eventually melt the bottom out of the pressure vessel and deposit the contents onto the floor beneath the reactor as full or partial meltdown ensues.

What happens after that depends largely on how the 150 tons per reactor (hopefully less) of fissile fuel rod contents ends up on the floor with the molten steel.

If dispersed the reaction may slow or cease. If not? Down down she goes!

And let's not even talk about the spent fuel ponds since the immediate area around the complex will have to be evacuated almost certainly resulting in two more meltdowns.

And then there is the wind.

[buddysmellgood]

1. I understand the bottom of the reactor vessel to be about 5 inches thick.

At three mile island, the fuel melted a small portion of the vessel. Hopefully this one will hold.

[flamingdem]

2. I wonder if they have doubts about it holding and why nt

[TheMadMonk]

10. 7/8" of a total of 8" IIRC. (Your 5 might be the correct figure.)

Stangely enough, under some circumstances at least, it may well safer (if a shitload more expensive) to let a reactor core collapse than try to maintain its integrity in circumstances where adequate cooling can not be guaranteed.

Now, beacause (I think in part) operators were unwilling to take either of the safe (but dirty) options of allowing a swift collapse, or frequent steam venting, we're stuck with the worst of both worlds. On one hand, a core that's now too cold to collapse swiftly, but still hot enough to slowly take itself to pieces. On the other hand, a core that has susstained sufficient damage that neccessary venting operations are now carrying away contamination that would almost certainly have been solidly held in fully intact fuel rod assemblies.

Fucking sad isn't it when public sentiment drives the operators to direct every effort towards absolute prevention, even when the truly safest option may well be to deliberately allow a smaller early failure, rather than take on the very serious risk of being unable to prevent a major failure later on if total containment does fail?

[Yo_Mama]

14. I wondered

Because my understanding is that if the fuel had melted down through the reactor, the resulting puddle in this design is supposed to spread out in a thin layer at the bottom of the containment vessel? And once it is in a thin layer, the fission part at least should be self-correcting, right? Because any fission in a meltdown of active fuel rods would be taking place inside a lump of the fuel rod materials, not on the surface? And obviously it is easier to cool a thin layer rather than a puddle or lump.

Thanks for your comment.

I was also wondering if a very thick brine and crusted salt from using the seawater could prevent the spreading process? I know they had absolutely no choice but to use what was available, but since no one's ever done this before, the accumulated salt and concentrated brine might be throwing a few twists in there.

[SpoonFed]

20. yeah, it's the public's fault

where do you come up with this, dude?

the shoe has dropped. the engineers have to get off their high horses and accept that people have a right to be afraid about the awesome potential of these things to go very wrong.

[TheMadMonk]

23. In part yes. Public sentiment, or fear of that public sentiment...

...led the operators to attempt the dangerous task of containing the radioactive steam released from the reactors. An attempt which led to the hydrogen explosions that added to the plant's woes.

If that steam had been released directly into the atmosphere as should have been done, radiation levels would have gone up for the duration of any releases, but long term contamination levels would have been a fraction of what we're seeing now. There is also a very good chance that with more venting earlier on, that the reactor cores could have been kept considerably cooler.

No one wanted to risk the public's ire by DELIBERATELY releasing radioactive anything (not even steam with a half life measured in minutes) into the environment. It took a direct prime ministerial order to get even the contained releases happening several hours after they were put forward as the obvious response to rising pressure levels. An uncontained deliberate release was not going to happen. Instead the considerably riskier approach which offered at least a chance at acheiving a zero emission outcome was tried and it failed very spectacularly. Twice.

[Yo_Mama]

3. It's not so much reactor 3 or even 1

Reactor 2 is breached somehow, and is leaking very short-lived fission products.

So it's in active fission, and it has a big leak.

They need to continue with the others, but getting 2 in control has got to be more of a priority.

See the news briefs at Kyodo News:
http://english.kyodonews.jp/

On NHK they are not obfuscating. They are talking active fission and major leak.

[flamingdem]

4. Wow, that's a huge change in approach, I applaud them

but I have to admit what they're saying is unnerving.

So it's No. 2 again..

[Yo_Mama]

7. It's all three

But tonight's info about 2 is so bad that it is stunning.

It's not just that they have a pretty big containment breach on 2. It's that because of the high levels of a very short-lived fission byproduct in the water, they know that this is coming from the core. They also know that fission is occurring in the core.

But the radiation levels in the water in the basement of the No 2 turbine building are 10 million times that of water that is normally used as coolant in the core of a reactor.

So it is a major meltdown with an uncontrolled fission reaction with a containment breach.

1 & 3 seem to be in fission with some leakage, but the water testing there showed radiation levels that were much less than on 2, so you could say that perhaps swapping over to fresh water injection would cool the broken rod material more efficiently.

Here my knowledge stops. I don't know what options they have in this situation. I am pretty sure that you can't entomb a reactor with active fission - successfully. IAEA is sending over two more teams. The navy has barges and other assets out there to try to provide enough freshwater to keep that going. I am sure the phone lines are burning up with consultations over ideas to deal with this development.

Perhaps they could try liquid nitrogen, but that just might cause an explosion. Probably boron won't work, because it sounds like they have a melted clot of fuel rod material with fission in the middle so the boron won't do much.

I guess we just watch the news and pray. They certainly can't send people in - they tested the radiation level of the reactor 2 water at over 1 sievert/hr. 1 sievert is where acute radiation sickness starts. If that measurement is right, you couldn't send people in for even 15 minutes under the disaster maximum of 250 milliSieverts set by the Health Ministry.

Up the nuclear creek without a paddle.

[jpak]

12. But we have been told right here on DU there was no fission occurring in the scrammed reactors

and that borate was not needed.

These "experts" wouldn't lie to us - would they?

[FBaggins]

19. What do you think the FIRST clue would be of active fission?

Imagine that somehow a sustained fission reaction was going on in one of the cores. What would the FIRST thing be that they noticed?

Would it really be that a leak in the basement would reflect a fission product?

[buddysmellgood]

5. wow.

[buddysmellgood]

6. http://www3.nhk.or.jp/daily/english/27_12.html

[crickets]

8. Jawdrop.

It's confirmed then.

The company says the latest reading is 10-million times the usual radioactivity of water circulating within a normally operating reactor.
TEPCO says the radioactive materials include 2.9-billion becquerels of iodine-134, 13-million becquerels of iodine-131, and 2.3-million becquerels each for cesium 134 and 137.

This needs its own topic. 10-million times the usual radioactivity. 2.9-billion becquerels. Million. Billion. Speechless.

[flamingdem]

9. I want to tell

friends to leave Tokyo right now. But it will look like (another) overreaction.

They will get the news, I hope it gets through their heads.

[PamW]

11. No active fission

Reactor 2 is breached somehow, and is leaking very short-lived fission products.

So it's in active fission, and it has a big leak.
===================================================

You can't conclude that there is an active fission chain reaction going on
in the reactor just because you see fission products.

The fission products you see were created when the reactor was operating
before the quake.

A fission chain reaction requires precise material and geometric conditions,
which the reactor isn't going to randomly assemble.

As Professor Thomas Downar of the University of Michigan Nuclear Engineering
Dept stated in:

http://www.physorg.com/news/2011-03-japan-worst-case-scenario-catastrophic-expert.html

Spent fuel, which is fuel that has already been used but still retains a level of radioactivity, is a new concern, says Thomas Downar, a professor in the Department of Nuclear Engineering and Radiological Sciences.

"The worst thing that could happen now is the fuel rods could be exposed to the air and that could be, then, down to our last barrier," Downar said. "We could not have a recriticality, or a nuclear explosion. It's physically impossible in this kind of system."


PamW

[Yo_Mama]

13. Not with those short-lived isotopes in those quantities

Iodine 134 has a half-life of under an hour.

There must be some sort of recent fission going on, unless they made a measurement mistake, which might be possible. See this for explanation (very, very unhysterical and knowledgeable commentary here):
http://atomicpowerreview.blogspot.com/2011/03/few-bothersome-facts.html

The fuel rods inside 2 were active, not spent fuel, and your quote above refers to spent fuel.

According to this, I-134 decays into Xenon 134:
http://www.wolframalpha.com/entities/isotopes/iodine_134/9w/jd/65/

On the other hand, I doubt very much that any study of fission byproducts in these conditions (a very concentrated brine) has ever been done. So maybe there's a change in decay chains somehow upstream of the Iodine 134 stage.

[FBaggins]

18. True, but there would be other signs of active fission.

Like amounts of heat that they couldn't possibly control with the amount of water they can currently pump. Yet the temperature and pressure indicate that no such reaction is happening (and at this point would be next to impossible anyway).


It IS possible to have very short half-life elements in abundance two weeks after shut down IF they are decay-chain daughter elements of something else with a much longer half-life higher up the chain. I just don't have a reference handy for which are direct fission products and which are daughters of those products.

My guess is the the most likely answer to the conundrum is that the reported levels of I134 are incorrect. The activity level is accurate (much harder to get wrong), but the isotope/nuclide determination was faulty.

[Yo_Mama]

16. Maybe it's a distillation effect

The water they are finding on these reactors is in the basements of the turbine rooms.

If the water was steaming off the cores, maybe it puddled in the steam lines in a very concentrated (radioactive) brine and so the high levels of radioisotopes don't really say too much about what is happening in the core.

Maybe.

Still, whatever is happening is happening in all three reactors. Nor can they account for it at any reactor. So it is probably somewhat related to the seawater, which was always a wild card. I dropped in on various physicists talking about this, and they all seemed to think differently from what I just wrote. And I'm not a physicist, so they would be much more qualified to speculate than I would.

Man, I feel so sorry for the workers trying to deal with this.

[SpoonFed]

21. no no no no no no no

active fission wasn't possible, the thing is shut down
were you not reading the posts from a week to two weeks ago!?!?!!?!!?!

i swear i read that. it was coming out of the fingers of all the smart educated engineer scientist types around these parts.

[FBaggins]

22. So I guess this is the magical undercover active fission?

The kind that does nothing except produce Iodine 134?

Really?

That doesn't strike you as just the least bit odd?

[Fledermaus]

15. Where's the floor of the refueling bay?

You can see the line of the floor on the right side, but as you move left it is gone.

It exploded real good!

Unit 3


Unit 1 you can see the floor of the refueling bay.

[Yo_Mama]

17. TEPCO Repents and Retracts - Great News

Previously TEPCO had said they found very large amounts of I-134 in the water at 2. Now they say it was another isotope with a longer half-life.
http://www3.nhk.or.jp/daily/english/27_24.html

The original testing on reactors 1-4 was just released and is here (but the I-134 figure is wrong):
http://www.nisa.meti.go.jp/english/files/en20110327-1-5.pdf

They do say however that the total radiation reading was correct. It's interesting to look at the differences in the test results for all four reactors.

The water in the reactor basements for 2 and 3 might end up looking quite similar after they retest. The net surface radiation on 3 is .75 sievert, and more than 1 sievert on 2.

The NISA release page is here:
http://www.nisa.meti.go.jp/english/files/en20110327-1.html