First they were going to vent Fukushima #3 due to pressure, now they're not. Why?

[ReturnoftheDjedi]

Do they fear a leak of Plutonium in the vented gas?

First there was this:

Gases to be vented from No.3 reactor

Workers at the Fukushima Daiichi nuclear power plant are preparing to release gases from the overheating Number 3 reactor to lower pressure inside its container vessel.

The Nuclear and Industrial Safety Agency said on Sunday that pressure inside the vessel is rising despite efforts to cool the reactor.

The agency said the workers will first try to vent gases through a suppression pool to reduce the amount of radioactive substances released into the environment.

If the pressure doesn't decline, the officials will release gases directly from the vessel. If that happens, the level of radioactive iodine in the air will increase by 100-fold.

Reducing pressure is necessary to protect the container vessel, which keeps radioactive materials inside the reactor in case of an accident.
http://www3.nhk.or.jp/daily/english/20_19.html

They were worried about pressure inside the #3 Containment Vessel.

Then came this:

No gases to be released from No. 3 reactor
The Tokyo Electric Power Company has decided against releasing gases from the overheating No. 3 reactor in an attempt to reduce pressure inside the containment vessel.

TEPCO officials in Fukushima said on Sunday afternoon that pressure within the reactor containment vessel has begun to stabilize, and gases don't need to be released for the time being.

They say they will closely monitor the situation.

The Nuclear and Industrial Safety Agency announced earlier on Sunday that pressure inside the vessel is rising despite efforts to cool the reactor by spraying seawater inside it.

The agency said the pressure must be reduced to protect the containment vessel, which holds radioactive materials inside in the event of an accident.
http://www3.nhk.or.jp/daily/english/20_23.html

They say that pressure "stabilized" without giving any details.

It is possible that they concluded the risk of venting plutonium-laced radiation outweighs the risk of pressure in the containment vessel.

[Warren DeMontague]

1. If you take them at their word, it was going up, it's still high, but it's stabilized.

I think the plutonium in that particular reactor is giving everyone pause.

[Indydem]

2. Pressure = Steam

If they can cool it and turn the steam back to water, it no longer needs vented.

[NutmegYankee]

3. If you cool steam, it condenses into water and reduces the pressure.

If they got the pumps back online, they can knock the steam down.

[backscatter712]

4. Hopefully, that means that with power restored to the Fukushima site...

the big pumps could get enough water in the reactor to cool it down and take the steam pressure down.

[bluecoat_fan]

5. I suspect wind direction, blowing inwards today.

This one has plutonium, so needs to go out to sea.

[truedelphi]

8. Good thinking.

And welcome (Belatedly) to DU.

[ReturnoftheDjedi]

13. makes more sense then what they said.

[kestrel91316]

6. They are waiting for the plutonium to decay before they release the pressure.

:sarcasm:

[leveymg]

9. How many millisiervets is that rain inside your comment?

:nuke:

[stockholmer]

11. according to TEPCO, there is no rain

:banghead:

[stockholmer]

7. maybe an answer-" Firefighters resume hosing No.3 reactor"(posted 3 hours later than your last link)

http://www3.nhk.or.jp/daily/english/20_27.html

Firefighters resume hosing No.3 reactor

The Tokyo Fire Department resumed high-pressure hosing of the Number 3 reactor at the Fukushima Daiichi nuclear plant at 9:30 PM on Sunday.

The operation is expected to continue for about 6 hours.

Water was discharged into the facility's spent fuel-rod pool for 13-and-a-half hours until 3:40 AM on Sunday.

Sunday, March 20, 2011 20:48 +0900 (JST)

----------------------------------------------------------------------------------------------------------------------
can't release plutonium steam kettle with water-spraying workers around

[ClarkUSA]

10. The New York Times cites power company officials as saying "the pressure had stabilized"

"The Tokyo Electric Power Company, which runs the plant, had appeared to suffer a serious setback as officials said that pressure buildup at the ravaged No. 3 reactor would require the venting of more radioactive gases.

But at a news conference a few hours later, officials from the power company said that the pressure had stabilized and that they had decided they did not need to immediately release the gases..."

http://www.nytimes.com/2011/03/21/world/asia/21japan.html?hp

[Hannah Bell]

12. all that happened about 12 hours ago.

http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=439x695918#696026

"It is possible that they concluded the risk of venting plutonium-laced radiation outweighs the risk of pressure in the containment vessel."

or it's possible that indeed, as they said, the pressure has been stabilized. if it had not been stabilized it would have continued to build & blown up. 12 hours later, it has not.

[ReturnoftheDjedi]

14. "nothing to see here. move along."

what do you make of the latest report of a chain reaction in the #4 Pool?

[Hannah Bell]

15. what i make is that you are nearly a day behind breaking events.

and i have no idea what you mean by a "chain reaction" in #4 pool.

the purpose of venting is to release pressure that might lead to an explosion. the consequence of an explosion would be worse than any venting.

[stockholmer]

16. update on Kyodo Japan news (Midnight there, so 6 hours ago)possible renewed chain reaction in Unit 4

http://english.kyodonews.jp/news/2011/03/79849.html

"-- Reactor No. 4 (Under maintenance when quake struck)

Renewed nuclear chain reaction feared at spent-fuel storage pool, fire at building housing containment of reactor Tuesday and Wednesday, only frame remains of reactor building roof, temperature in the pool reached 84 C on March 14, water sprayed at pool on Sunday."



---------------------------------------------------------------------------------------------------------------
That spent fuel pool has over 100,000 rods, and no containment barrier (other than water) between it and direct contact with the outside air, due to the explosion earlier this week ripping through the containment building.

[Hannah Bell]

17. That is a timeline of significant events at each reactor, not a current event.

The "fear" occurred on the 15th/16th.

http://www.google.com/#sclient=psy&hl=en&site=&source=hp&q=number+4+fear+chain+reaction&aq=f&aqi=&aql=&oq=&psj=1&bav=on.2,or.r_gc.r_pw.&fp=c47ba9fccbc37ce6

[stockholmer]

18. google link doesnt work for me here in Sweden, earliest I found was the 18th, US time, 19th, Japan)

all the US posts on Friday (filed on the 18th) use this (which was posted on the 19th in Japan, due to Japan being 13 hours ahead of NYC)

http://english.kyodonews.jp/news/2011/03/79482.html


nothing from the 15th or 16th (a link would be great).

Have they stopped the re-reaction in Unit 4 spent fuel pool?

Media black hole on this info, it is frustrating.

cheers

[Hannah Bell]

19. as i said to the other poster, that is a timeline of events for each reactor.

if you read carefully, you see that it notes each significant event for each reactor that has occurred so far.

the "fear" of "chain reaction" occurred on the 15th/16th.

http://content.usatoday.com/communities/ondeadline/post/2011/03/new-fire-reported-at-fukushima-reactor-no-4/1

http://www.google.com/#hl=en&q=number%204%20fear%20chain%20reaction&psj=1&wrapid=tlif130065626407810&um=1&ie=UTF-8&tbo=u&tbs=nws:1&source=og&sa=N&tab=wn&psj=1&bav=on.2,or.r_gc.r_pw.&fp=c47ba9fccbc37ce6

[stockholmer]

21. thanks for link,(I've understood about the cumulative nature of updates,btw)lets hope no re-reaction

occurs.


:hi:

[Warren DeMontague]

20. They concluded a major water spraying operation at #4. Hopefully that has helped the situation in

the spent fuel pool at that reactor.

[stockholmer]

22. yes, positive thoughts to all brave souls inside that cauldron

[james0tucson]

27. "chain reaction"

The idea of a chain reaction is that the fuel rods could, through an incredibly unlucky series of events, arrange themselves in a configuration that causes some of the mass to become a critical mass. The likelihood of this happening is really small. There would have to be a fire or an explosion, and the rods would have to just happen to land in a stack that causes neutrons to slow down and/or reflect, which would mean there was a nuclear reaction going on instead of just decay heat.

This is NOT going to happen... enemies of Japan are not that lucky.

If you really want to speculate in this direction, though, imagine if the fuel rods all caught fire, and then melted, and then just happened to cool into a perfect sphere. The resulting critical mass would be an efficient dirty bomb, and in theory could explode. Not going to happen, it is safe to say.

If these weren't spent fuel rods, then there would actually be a relatively high chance of several of the rods coming together to form a critical mass -- that's the whole point of their size and shape. But depleted fuel rods are a very different matter.

[Hannah Bell]

28. i'm not the one speculating in this direction.

[flamingdem]

23. Another reason might be that the winds are going to Tokyo right now

so any thoughts of venting were put aside for the moment.

The suspicious part is how quickly they change the message.

Within a very short time all of all sudden it went from ... it's melting down possibly, we can't really know, pressure is up we have to vent to... it's all fine, pressure down, no venting, reactor stabilized!

[Hannah Bell]

24. the decision not to vent occurred more than 12 hours ago. the possibility of

need to vent occurred hours before that.

it's only the late reporting in the west that makes it seem like these events occurred in quick succession.

[flamingdem]

25. I was wondering about that

so it does make more sense, good.

[Cetacea]

26. +1

Agreed.

[Codeine]

32. You keep explaining this, but they never get it.

People think if they just stumbled across a bit of info it must have just happened two seconds ago.

[reorg]

29. seems likely, even without venting, radiation levels in Ibaraki have been rising lately

Ibaraki - Hoiguchi Hitachinaka City

3/21 05:50 (JST) 2040 nGy/h
3/21 04:20 (JST) 1635 nGy/h

3/20 17:40 (JST) 639 nGy/h
3/20 08:40 (JST) 631 nGy/h
3/20 06:50 (JST) 637 nGy/h

3/19 01:00 (JST) 749 nGy/h
3/18 20:50 (JST) 760 nGy/h
3/18 18:00 (JST) 763 nGy/h
3/18 03:00 (JST) 847 nGy/h
3/18 01:00 (JST) 856 nGy/h

3/17 21:40 (JST) 872 nGy/h
3/17 19:20 (JST) 876 nGy/h
3/17 16:40 (JST) 881 nGy/h
3/17 03:00 (JST) 993 nGy/h

3/16 23:50 (JST) 1011 nGy/h
3/16 19:50 (JST) 1029 nGy/h
3/16 17:40 (JST) 1044 nGy/h
3/16 06:00 (JST) 2114 nGy/h

http://www.targetmap.com/viewer.aspx?reportId=4870

normal level seems to be around 30 nGy/h

[Sirveri]

31. If they need to vent, they will vent rather than blow containment.

It really is that simple. Their decision to vent or not vent is solely contingent on the pressure inside the containment, if it gets too high they must vent, or containment WILL fail. Which way the wind blows is quite simply irrelevant. Send 100 Curies out, or hold it in and then send 10000. The choice is clear.

[quiller4]

30. The readings they got are low enough that they could delay venting

after pressure stabilized it began dropping substantially according to an IAEA report earlier this afternoon.