Is there any good news about these reactors?

[The Backlash Cometh]

Anything. I'll accept any good news.

[ReturnoftheDjedi]

1. Reactor 5 and 6 were never a problem and are not now.

That's as good as it gets.

[OKIsItJustMe]

3. Reactor #4 is not a problem

Its spent fuel pool is a problem, but not the reactor itself.

And, they’re injecting fresh water (rather than sea water) into reactors 1, 2 & 3 now.

http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=115&topic_id=284140&mesg_id=284140

[aquart]

4. Uh....

How do you define "problem"?

"-At Units 5 and 6, in order to prevent hydrogen gas from accumulating
within the buildings, we have made three holes on the roof of the reactor
building for each unit."

So we're pretty sure there won't be hydrogen explosions there now. But I'd say the holes suggest awareness of a "problem."

[OKIsItJustMe]

5. That was a precaution.

Given the explosions at reactor buildings 1-4, you can hardly blame them, however (as far as we know) there was no damage to either reactors 5 & 6 or their spent fuel pools.

[OKIsItJustMe]

8. Can you imagine being the one to use the saw?

Seriously, you’ve got to be thinking about the sparks that are about to fly… and what happened to buildings 1-4…

[Nihil]

24. Why does that make me think of ...

... the Gary Larson cartoon where one man is working on a missile
and his colleague is standing behind him with an inflated paper bag ...?
:evilgrin:

[CabalPowered]

6. Good question

I've been wondering the same..

"The firm also said it found both iodine-131 and cesium-137 in a sample taken from near the drain outlets of the plant's No. 5 and No. 6 reactors that stabilized Sunday in so-called ''cold shutdown.''"

http://english.kyodonews.jp/news/2011/03/80810.html

[ReturnoftheDjedi]

7. arggh, thanks for decimating my one bit of good news.

:)

[aquart]

10. ALL those reactors were without power for how long?

Even without earthquake damage, I have to guess that's a "problem."

[OKIsItJustMe]

12. They don’t think so

http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=115&topic_id=284137&mesg_id=284137

…

Unit 5 (outage due to regular inspection)
-Sufficient level of reactor coolant to ensure safety is maintained.
-At 5 am, March 19th, we started the Residual Heat Removal System Pump (C) 
 in order to cool the spent fuel pool.
-At 2:30 pm, March 20th, the reactor achieved reactor cold shutdown. At 
 around 5:24 pm on March 23rd, when we switched the temporary Residual 
 Heat Removal System Seawater Pump, it has stopped automatically. At 
 around 4:14 pm, March 24th we replaced the pump, and restarted cooling of 
 reactor at around 4:35 pm.
-At this moment, we do not consider any reactor coolant leakage inside the 
 reactor happened.

Unit 6 (outage due to regular inspection)
-Sufficient level of reactor coolant to ensure safety is maintained.
-We completed the repair work on the emergency diesel generator (A).
-At 10:14 pm, March 19th, we started the Residual Heat Removal System Pump 
 (B) of Unit 6 in order to cool the spent fuel pool.
-At 7:27 pm, March 20th, the reactor achieved reactor cold shutdown.
-In relation to the two seawater side pumps of the Residual Heat Removal 
 System, we switched the power source from temporary to permanent at 3:38 
 PM and 3:42PM, Mar 25 respectively.
-At this moment, we do not consider any reactor coolant leakage inside the 
 reactor happened.

…

[damntexdem]

20. "They" being TEPCO?

If so, then better than saying "they don't think so," just say "they don't think."

[CabalPowered]

2. Yes

Radiation levels detected to the South are continuing to decline since the explosions..

http://gebweb.net/japan-radiation-map/

That's all I've got.

[The Backlash Cometh]

11. I'll take it.

[Journeyman]

9. Yes. It has caused people to reassess their attitudes towards burning garbage for electricity. . .

Not enough people so far, but we're only two weeks into a catastrophuck of indeterminate duration and impact.

[OKIsItJustMe]

13. electrical power has been restored at Units 1, 2 and 3 and fresh water is now available on the site

http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=115&topic_id=284210&mesg_id=284210

[FBaggins]

14. Loads of good news.

The reactor cores themselves are pretty close to cooled down. It's virtually impossible at this point for a meltdown to resume and a full-blown core disaster to occur. Plenty of radioactive material can/will leak out, but the possibility of a worst-case disaster there is pretty much gone.

The fuel pools were the next big concern. We don't know how close to "worst case" those got (were the pools ever "dry"?), but the race in the early days to keep them covered in water has been replaces with a comparatively easy method that by all reports is working fine. Again, some radioactive material could be leaking out, but there's no longer a great risk of a pool drying up and a fire spreading those elements far and wide.

The news is not all good by any means. They can't leave the fuel in those pools nor in a leaking reactor, and getting it OUT will be quite a challenge. There are lots of things that can still go wrong and lots of ways that people there at the plant could get dangerous exposure levels.

In short, it's far from "over", but the risks of the most disastrous possibilities have declined markedly.

[OKIsItJustMe]

15. Re: (were the pools ever "dry"?)

Well, we know that the pool in building #4 was "dry" enough to produce a whole bunch of hydrogen. So, it was dry enough that the rods had begun to burn.

http://allthingsnuclear.org/post/4133270698/where-did-the-water-in-the-spent-fuel-pools-go">Where Did the Water in the Spent Fuel Pools Go?

[FBaggins]

16. That just tells us that the pools were low.

They obviously couldn't be completely dry at the time or there wouldn't be any water to produce the hydrogen.

And the rods don't have to "burn" in order to produce hydrogen, in fact (for the same reason above), the two are independent. the portion "burning" (if any) would have to be above water and the portion producing hydrogen would have to be below it.

We know that the fuel got quite hot, but that's possible with several feet of water still in the pool. And "quite hot" is enough for some of the fuel assemblies to break up (and increase the amount of material that is released in steam and/or overflow)... but if there was any burning, there wasn't much of it (it would have been much more obvious that the smoke we've seen (and wouldn't have put itself out).

[OKIsItJustMe]

21. How low?

http://allthingsnuclear.org/post/4133270698/where-did-the-water-in-the-spent-fuel-pools-go

…

Each of the six reactor units at Fukushima has its own spent fuel pool. These pools are about 12 meters deep. The spent fuel occupies roughly the bottom 4 meters of the pool and the surface of the water is typically about 7 meters above the top of the rods. In normal operation, electric pumps continually circulate the water in the pool, pulling out heated water, which is then cooled and sent back into the pool.

…

As long as the water, even though boiling, continues to cover the fuel rods it protects them from damage. But once it drops far enough to expose a meter or so of the rods, the exposed sections can become hot enough to damage the cladding on the rods and release radioactive gases. If the fuel continues to heat up, the cladding can begin to burn, which produces hydrogen. If enough hydrogen collects above the pool, it can explode.

The earthquake took place on the afternoon of Friday, March 11. Four days later, on Tuesday, March 15, press reports of a fire in the Unit 4 spent fuel pool and hydrogen released from the spent fuel rods suggested that water had dropped well below the top of the fuel rods in the Unit 4 pool.

…

[FBaggins]

22. My guess?

Low enough that there was some damage done to fuel (in pool #4 and probably #3), and obviously low enough in the case of #4 to produce hydrogen, but not low enough to catch fire and send out massive amounts of smoke carrying radioactive particles.

But the water that is essentially flowing through those pools (poured in and either draining or overflowing) would carry some elements with it that would otherwise be protected by the zirconium.

[Turbineguy]

18. Check this out.

https://www.oecd-nea.org/nsd/reports/2009/nea6846_LOCA.pdf

This report deals with Loss of Cooling Accidents. Some interesting stuff on hydrogen embrittlement of zirconium cladding.

The calculation for H2 generation rates starts on page 211

Hydrogen (when properly mixed with O2) has a BTU content of 60,000 BTU per pound. For comparison, gasoline has a heat content of 23,000 btu per pound. As a practical matter since gasoline is a liquid it is much harder to get good combustion. This is why a Hydrogen explosion is much more severe. Hydrogen is more efficient at blowing up.

From my reading it seems that while hydrogen is produced all the time in very small quantities during normal reactor operation, when the rods are uncovered, this rate increases by exposure to steam. Under normal operating conditions the hydrogen travels with the steam through the turbines, does not get condensed and is eliminated along with other non-condensible gasses through the air ejectors (or vacuum pumps) which maintain vacuum on the condenser.

[kristopher]

23. In building #3 earthquake caused the crane to drop into the storage pond.

It is probable that the rods were damaged at that time; which would explain why timelines about how long it should have taken for the water to boil away have not tracked events there.

That was a honking big hunk of metal that was hanging suspended over the pool. This was on NHK news yesterday morning US time.

[Yo_Mama]

17. I think the good news is that it has gotten as bad as gets

Granted, there's a whole lot more to do before things get into a state that's more controlled, but I think now they've hit the bottom and may start struggling back up.

[damntexdem]

19. There were only 6 at Fukushima.

There, that's all the good news. ;-)