Categories
Hot News Nuclear

Fukushima nuclear accident: Saturday 19 March summary

Last Saturday the the crisis level at the Fukushima Daiichi nuclear power station was rapidly on the rise. Hydrogen explosions, cracks in the wetwell torus and fires in a shutdown unit’s building — it seemed the sequence of new problems would never end. A week later, the situation remains troubling, but, over the last few days, it has not got any worse. Indeed, one could make a reasonable argument that it’s actually got better.

Yes, the IAEA has now formally listed the overall accident at an INES level 5 (see here for a description of the scales), up from the original estimate of 4. This is right and proper — but it doesn’t mean the situation has escalated further, as some have inferred. Here is a summary of the main site activities for today, followed by the latest JAIF and FEPC reports. You also might be interested in the following site map:

Another large cohort of 100 Tokyo fire fighters joined the spraying operation to cool down the reactors and keep the water in the spent fuel ponds. The ‘Hyper Rescue’ team have set up a special vehicle for firing a water cannon from 22 m high (in combination with a super pump truck), and today have been targeting the SNF pond in unit 3. About 60 tons of sea water successfully penetrated the building in the vicinity of the pool, at a flow rate of 3,000 litres per minute. Spraying with standard unmanned vehicles was also undertaken for 7 hours into other parts of the the unit 3 building (delivering more than 1,200 tons), to keep the general containment area cool. The temperature around the fuel rods is now reported by TEPCO (via NHK news) to be below 100C.

Conditions in unit 3 are stabilising but will need attention for many days to come. Promisingly, TEPCO has now connected AC cables to the unit 1 and 2 reactor buildings, with hopes that powered systems can be restored to these building by as early as tomorrow (including, it is hoped, the AC core cooling systems), once various safety and equipment condition checks are made.

Holes were made in the secondary containment buildings of Units 5 and 6 as a precautionary measure, to vent any hydrogen that might accumulate and so prevent explosions in these otherwise undamaged structures.  The residual heat removal system for these units has now been brought back on line and these pools maintain a tolerable steady temperature of 60C. More here. These buildings were operating on a single emergency diesel generator, but now have a second electricity supply via the external AC power cable.

Why are they concentrating on these activities? Let’s revisit a bit of the history of last week. The spent fuel pool still has decay heat (probably of the order of few MW in each pool) that requires active cooling. When power went out on Friday, the cooling stopped and the pool temperature has been rising slowly over the weekend, and probably started boiling off (and a large volume may have also been lost due to ‘sloshing’ during the seismic event). The pool is located on the 4th floor above the reactor vessel level. It remains unclear why they could not arrange fire trucks to deliver the sea water before the fuel rods got damaged and started releasing radioactivity. Now the effort is hampered by the high radiation level (primarily penetrating gamma rays). This is the inventory of those spent fuel ponds that have been causing so many headaches:


In order to remove the decay heat after the reactor shutdown, the cooling system should be operating. Following the loss of offsite power, the on-site diesel generators came on but the tsunami arrived an hour or so later and wiped out the diesel generators. Then the battery provided the power for 8 hours or so, during which time they brought in portable generators. However, the connectors were incompatible. As the steam pressure built up inside the pressure vessel, the relief valve was open and dumped the steam to the pressure suppression chamber, which in turn was filtered out to the confinement building and the hydrogen explosion took out the slabs.

The sea water was then pumped in by fire trucks and the reactor pressure vessels are now cooled down to near atmospheric pressure but the fuel assemblies are uncovered at the top quarter or third (the FEPC updates give the actual pressure and water levels). It appears that the pressure vessels and the reactor containment structures are intact, except the Unit 2, where the hydrogen explosion took place inside the containment and hence damaging the lower wetwell torus structure (but almost certainly not the reactor vessel, although the exact status is unclear). It appears that the radioactivity releases are mostly coming from the spent fuel storages than the reactor cores.

World Nuclear News has a really excellent extended article here entitled “Insight to Fukushima engineering challenges“. Read it! Further, you must watch this 8 minute reconstruction of the timeline of the accident done by NHK — brilliant, and really highlights the enormous stresses this poor station faced against a record-breaking force of nature. As I’d noted earlier, just about everything that could have went wrong, did. But valuable lessons must also be learned.

The IAEA and Japanese government has reported the potential contamination of food products from the local Fukushima area via radioactive iodine (mostly vented as part of the pressure relief operations of units 1 to 3). This is a short-term risk due to the 8-day half-life of radioactive iodine (and a small risk, given the trace amounts recorded), but precautions are warranted, as discussed here. What does this mean?

In the case of the milk samples, even if consumed for one year, the radiation dose would be equivalent to that a person would receive in a single CT scan. The levels found in the spinach were much lower, equivalent to one-fifth of a single CT scan.

… and to further put this in context:

The UK government’s chief independent scientific advisor has told the British Embassy in Tokyo that radiation fears from the stricken Fukushima nuclear power plant are a “sideshow” compared with the general devastation caused by the massive earthquake and tsunami that struck on 11 March. Speaking from London in a teleconference on 15 March to the embassy, chief scientific officer John Beddington said that the only people likely to receive doses of radiation that could damage their health are the on-site workers at the Fukushima Daiichi plant. He said that the general population outside of the 20 kilometre evacuation zone should not be concerned about contamination.

As to the possibility of a zirconium fire in the SNF ponds, this seems unlikely. Zr has a very high combustion point, as illustrated in video produced by UC Berkeley nuclear engineers. They applied a blowtorch to a zirconium rod and it did not catch on fire. The demonstration is shown about 50 seconds into this video. The temperature was said to reach 2000C [incidentally, I visited that lab last year!].

The the Japan Atomic Industrial Forum has provided their 12th reactor-by-reactor status update (16:00 March 19).

Here is the latest FEPC status report:

———————-

  • Radiation Levels
    • At 7:30PM on March 18, radiation level outside main office building (approximately 1,640 feet from Unit 2 reactor building) of Fukushima Daiichi Nuclear Power Station: 3,699 micro Sv/h.
    • Measurement results of ambient dose rate around Fukushima Nuclear Power Station at 4:00PM and 7:00PM on March 18 are shown in the attached two PDF files respectively.
    • At 1:00PM on March 18, MEXT decided to carry out thorough radiation monitoring nationwide.
    • For comparison, a human receives 2,400 micro Sv per year from natural radiation in the form of sunlight, radon, and other sources. One chest CT scan generates 6,900 micro Sv per scan.
  • Fukushima Daiichi Unit 1 reactor
    • Since 10:30AM on March 14, the pressure within the primary containment vessel cannot be measured.
    • At 4:00PM on March 18, pressure inside the reactor core: 0.191MPa.
    • At 4:00PM on March 18, water level inside the reactor core: 1.7 meters below the top of the fuel rods.
    • As of 3:00PM on March 18, the injection of seawater continues into the reactor core.
    • Activities for connecting the commercial electricity grid are underway.
  • Fukushima Daiichi Unit 2 reactor
    • At 4:00PM on March 18, pressure inside the primary containment vessel: 0.139MPaabs.
    • At 4:00PM on March 18, pressure inside the reactor core: -0.002MPa.
    • At 4:00PM on March 18, water level inside the reactor core: 1.4 meters below the top of the fuel rods.
    • As of 3:00PM on March 18, the injection of seawater continues into the reactor core.
    • Activities for connecting the commercial electricity grid are underway.
  • Fukushima Daiichi Unit 3 reactor
    • At 2:00PM on March 18, six Self Defense emergency fire vehicles began to shoot water aimed at the spent fuel pool, until 2:38PM (39 tones of water in total).
    • At 2:42PM on March 18, TEPCO began to shoot water aimed at the spent fuel pool, until 2:45PM, by one US Army high pressure water cannon.
    • At 3:55PM on March 18, pressure inside the primary containment vessel: 0.160MPaabs.
    • At 3:55PM on March 18, pressure inside the reactor core: -0.016MPa.
    • At 3:55PM on March 18, water level inside the reactor core: 2.0 meters below the top of the fuel rods.
    • As of 3:00PM on March 18, the injection of seawater continues into the reactor core.
  • Fukushima Daiichi Unit 4 reactor
    • No official updates to the information in our March 18 update have been provided.
  • Fukushima Daiichi Unit 5 reactor
    • At 4:00PM on March 18, the temperature of the spent fuel pool was measured at 152.4 degrees Fahrenheit.
  • Fukushima Daiichi Unit 6 reactor
    • At 4:00PM on March 18, the temperature of the spent fuel pool was measured at 148.1 degrees Fahrenheit.
  • Fukushima Daiichi Common Spent Fuel Pool
    • At 10:00AM on March 18, it was confirmed that water level in the pool was secured.
  • Fukushima Daiichi Dry Cask Storage Building
    • At 10:00AM on March 18, it was confirmed that there was no damage by visual checking of external appearance.

At 5:50PM on March 18, Japanese Safety Authority (NISA: Nuclear and Industrial Safety Agency) announced provisional INES (International Nuclear and Radiological Event Scale) rating to the incidents due to the earthquake.

Fukushima Daiichi Unit 1, 2 and 3 Unit = 5 (Accident with wider consequences)

Fukushima Daiichi Unit 4 = 3 (Serious incident)

Fukushima Daini Unit 1, 2 and 4 Unit = 3 (Serious incident)

(No official provisional rating for Fukushima Daini Unit 3 has been provided.)

———————-

By Barry Brook

Barry Brook is an ARC Laureate Fellow and Chair of Environmental Sustainability at the University of Tasmania. He researches global change, ecology and energy.

344 replies on “Fukushima nuclear accident: Saturday 19 March summary”

Selfigniting, thats the difference,.. that and havin’ a thing with words.. I picked up this story about the hydrogen: Hydrogen/steam mix does not selfignite, but as the mix reached the cold roof, the steam condensed, the mix changed and went boom. Never tried that. Does it work that way?

Like

From Wikepidia, not enough time to do the monkey explaination of the corona effect…. The wife is already eying me about how long I have been on here….

http://en.wikipedia.org/wiki/Alternating_current#Effects_at_high_frequencies

A direct current flows constantly and uniformly throughout the cross-section of a uniform wire. An alternating current of any frequency is forced away from the wire’s center, toward its outer surface. This is because the acceleration of an electric charge in an alternating current produces waves of electromagnetic radiation that cancel the propagation of electricity toward the center of materials with high conductivity. This phenomenon is called skin effect.

(CORONA EFFECT as I called it)

At very high frequencies the current no longer flows in the wire, but effectively flows on the surface of the wire, within a thickness of a few skin depths. The skin depth is the thickness at which the current density is reduced by 63%. Even at relatively low frequencies used for high power transmission (50–60 Hz), non-uniform distribution of current still occurs in sufficiently thick conductors. For example, the skin depth of a copper conductor is approximately 8.57 mm at 60 Hz, so high current conductors are usually hollow to reduce their mass and cost.

Since the current tends to flow in the periphery of conductors, the effective cross-section of the conductor is reduced. This increases the effective AC resistance of the conductor, since resistance is inversely proportional to the cross-sectional area in which the current actually flows. The AC resistance often is many times higher than the DC resistance, causing a much higher energy loss due to ohmic heating (also called I2R loss).

Like

Parrot, it likely took a spark to ignite the hydrogen collected in the upper reactor building…. It didn’t ignite itself in my opinion….

Like

@CyrilR 9:16 AM

Latest JAIF report Mar 19 22:00 Re R4 SFP ” Water level low; Preparing water injection; Hydrogen from pool exploded.”

Yesterday I posted:
Picture of R4 building http://i.dailymail.co.uk/i/pix/2011/03/18/article-1367524-0B3B46E800000578-690_964x641.jpg

This looks like R4 building explosion was outward, not damaged inward from adjacent R3 H2 explosion Mar 14 11:01. JAIF and IAEA both say that R4 building was damaged by R3 explosion. Latest JAIF spreadsheet info does not show any R4 building explosion. Although JAIF does not indicate it, there are Wiki reports that R4 building had explosion 06:00 on Mar 15 with fires afterwards.

Mar 14 BNC comments discussed R3 building damage but not R4 building damage. JAIF report Mar 15 10:30 shows R3 severely damaged but R4 building undamaged. Subsequent JAIF reports show progressively more damage to R4 building.

R4 had no fuel in it, so any R4 building damage could not come from venting Reactor 4 H2 to building. Diesel and lube oil (implicated in R4 building fires) do not form explosive vapors.

That leaves the R4 SFP fuel assemblies as the only source of H2 for a R4 building explosion.
Therefore the R4 SFP fuel assemblies must have become uncovered by water and heated to 850-950C on Mar 15 to generate H2 and cause explosion.

Like

Questions to ponder, answer, or ignore as you all see fit:
(and I apologize if they have already been addressed on the site)
1a. The WSJ reports that Tepco delayed using seawater to cool #1 in order to save the reactor from permanent damage.
( http://online.wsj.com/article/SB10001424052748704608504576207912642629904.html?mod=e2tw )
But I also read that #1 was about to be retired in March. Is this true that the reactor was to be retired, or was it likely to be inspected then have it’s license renewed?

1b. After the Niigata earthquake the Kashiwazaki plant was shut down for months, so is it plausible that Tepco would take any risk to protect an asset that was likely to never be used again?

It seems that if the #1 reactor really was at end of life, it goes a long way in acquitting Tepco from the charge of gross indifference for financial gain (a characteristic the press loves to attribute to corporations) and instead points toward poor understanding of the severity of the situation and an overwhelmed response team.

2. Has seawater ever been used to cool a reactor by direct injection in the past? How about spent storage pools?

3. The reactors seemed to blow up a few hours after the seawater injection started on each respective reactor. My understanding is that the explosions were all from H2, which could have accumulated while hot and exploded hours later, even though cooler temperatures meant it was being produced at a lower rate,…. but my experience with He tells me that it does not hang around for long outside a solid enclosure. Maybe they only vented hours after beginning the injection? Does this sequence make sense to those who are experienced with the technology? It bothers me that all the explosions seemed to happen hours after seawater injection started.

Like

Further, on Mar 15, there were no holes cut in R4 roof to ventilate any H2 from SFP. This was done on R5 & 6 buildings post R4 building explosion.

Like

Yes true, R4 had done a full core offload to the pool so heat generation would have been greater from the fuel pool. What I don’t understand though with that theory is why they have not attacked R4 as aggressively with water….

It is credible I guess that R4 pool emptied and due to the large hot load of fuel ended up in a zirc water reaction zone producing hydrogen… I am just not sure about that yet to buy it. But the building did explode….

Like

Are you sure? If you know you’re gonna release hydrogen into a confined space, wouldnt you keep the sparks away? I mean, sparks dont occur all that often. Static electricity release maybe? I cant imagine that place to be ‘sparky’ for any reason.

Like

Maybe there is some technical explaination of how hydrogen from unit 3 could migrate to unit 4. Not knowing all the design features could be the answer….

It is possible they shared some portion of their ventilation systems as paired units….

Like

any after quake shake of the building with damaged structural components could have resulted in a static discharge though….

Like

Can someone please confirm or deny the rumour that 5 workers have died at Fukushima? Ive seen this rumour in a couple of articles but Ive yet to find a reliable source of information.

Like

Steven Chu, Winner of the Nobel Prize for Physics and pro-nuclear Secretary of Energy, will be on many of the Sunday Morning (EDT,USA) TV talking-head news shows. Should be interesting!

–bks

Like

I can’t remember how I came across this link, but the experiments described in it are mind blowing. They actually blew up test reactors to see how far the radioactive material would go. They tried to get maxium release and most of it came down very locally, counter to all the models they had. These experiments would not be allowed anymore and I’m surprised they ever were.

Click to access RealismApp1a-attch.pdf

Like

em1ss – having been a monkey a long time ago, I thought if you were worried about the skin effect you’d want to use braided wire instead of solid single core.

Like

@bchtd1parrot
One confirmed death from a crane accident, two workers missing… That’s all the news I’ve heard in japan about deaths and missing people at daiichi and daini

http://www3.nhk.or.jp/news/html/20110320/t10014790841000.html
Jsdf are spraying water on number four now, eleven trucks in total… They sprayIng is going to finish this morning to allow time for power cables to be connected
The fire department is also preparing to spray tonight from 6 until morning

Like

Grrr, can’t find a pre accident photo. Anyone have one to link to count the vent stacks on site prior to the accident?

Like

I noticed this moderator comment away back and though it should be re-iterated after reading some of the latest comments from overnight.

MODERATOR
This comments contains multiple instances of unsubstantiated personal opinion which violate the BNC Commenting Rules. BNC is a science based blog and authoratative references are required to support opinions/appraisals.References are being checked and comments found to have edited reported information to suit the poster’s comment will be deleted and may result in permanent banning as a troll.
Please check the Commenting Rules before submitting your comment.

Like

One of their conclusions is that:

“If realistic consequence scenaros are considered, it becomes apparent that evacuation of very large areas is neither needed nor effective. The principal threat to the majority of the population is the passage of a dispersing radioactive cloud. This cloud would contain mostly the noble gases xenon an krypton. Against this threat, sheltering may be the best option in the short term (hours and days), and time then exists to determine what long-term actions (months and years) are required. There is no acute need for evacuation.”
MODERATOR
[Please supply link to the above quote]

Like

I wondered if they could possibly be using something like linseed oil and have had spontaneous combustion. Well, maybe:

http://dx.doi.org/10.1115/1.4002892
Previous Article

J. Eng. Gas Turbines Power / Volume 133 / Issue 5 / Research Papers / Nuclear Power
Investigations and Countermeasures for Deactivation of Hydrogen Recombination Catalyst at Hamaoka Units 4 and 5
J. Eng. Gas Turbines Power — May 2011 — Volume 133, Issue 5, 052918

The hydrogen concentration in the outlets of off-gas recombiners increased at Hamaoka Units 4 and 5, and their reactors could not continue the startup operations. Therefore, we investigated why the recombination reactions were deactivated …. Two types of deactivation mechanisms were found …. decrease in the active surface area of alumina as support material due to dehydrative condensation. The other cause was the catalyst being poisoned by organic silicon compounds. Organic silicon was introduced from the organosilicon sealant used at the junctions of low-pressure turbines. We also found that a boehmite rich catalyst was deactivated more easily by organic silicon … the organic silicon poisoning the catalyst surface. …the linseed oil that used to be used at the plants was applied again as sealant in the low-pressure turbine casing instead of organosilicon sealant….”

Pure speculation, that’s an oil ‘sealant’ rather than ‘lubricant’ but if someone left an oily rag or an open can when evacuating the site, that’s a possible ignition source.

Like

IF someone can find a clearer picture pre accident please do so. This image seems to show units 1 & 2 sharing a common vent stack. Units 3 & 4 also sharing a common vent stack.

To get there you would have to a ventilation interface, which could explain the hydrogen explosion on unit 4 despite an empty reactor vessel….

I am looking for confirmation or denial of shared vent stacks between unit 1& 2 along with units 3 & 4.

Like

@em1ss: “any after quake shake of the building with damaged structural components could have resulted in a static discharge though….”

yes, I was about to mention that.

My recollection from following Sky News and CNN was that the reports of most of the explosions emerged near simultaneously with reports of the most major aftershocks in the area of the power plant..

-Ferg

Like

A good question raised here about why the hydrogen explosion on unit 4 may have identified another significant design fault with these units….

A shared vent stack by paired units……

Like

Ms Perps
Have you seen the number of visitors to this post? Overnight comments will be moderated, but due to the overwhelming value of the site it is not closed for comments overnight. That would under the current circumstances be inhumane to my opinion.This is not standard operational business i assure you. Please… i mean… please.

Like

I know that some people currently resident in Japan find their way here looking for information that will help them make decisions for their personal situations. I have written a commentary on this, to which I link below. I hope this is acceptable to the moderators here, and in fact, if you find the article helpful, would welcome it if you displayed a link to it in a visible place on your website until the acute panic especially in Tokyo has subsided.

http://www.facebook.com/notes/axel-lieber/why-i-stay-in-tokyo/10150164049983623

Like

Barry – would it be possible to start an evolving new thread that specifically captures and addresses what went wrong as regards design, implementation, operation, regulation, redesign/modification, accident event and response. I think this is about to become the main focus of media reporting and you might want to get ahead on that one and see what can be pieced together. I am happy to contribute a basic doc regarding design considerations and failure analysis processes for some context. This must all move soon to how what has been happening.happened in these spaces and how they map to what is being done to today and what is being proposed in G4..

Its oerson nice to feel that my mind is now on this rather than the direct event, feeling currently that the authorities may well have gotten over the hill – which is a matter of significant relief.

Like

I hope she’s not commenting on our discussions, which I believe to be mostly technical in nature…. I try to prefice opinion with statements of opinion….

MODERATOR
Technical information has not been edited (not enough expertise/time anyway) We leave that for Barry. Links to popular media, government information etc are checked and only edited if found to have been interpreted/edited by commenter’s to suit their own opinion.

Like

Again, no time to read all posts, maybe this has been discussed already? And I know benefit of hindsight and all that, but spent fuel rod ponds on the 4th floor?, in the most earthquake prone area of the planet? Jeees!!!

Like

@William Fairholm
That sounds like an entirely different way of thinking, but it might make sense. Specially since evacuation itself isnt entirely safe. The story itself is totally cruel. Lets try make a small disaster to see what a big one looks like. The data is very valuable, assuming its correct.

Like

unclepete
A niner didnt hurt it. Besides, the further down the pond, the longer the way between pond and core. straight down is not an option. The main structure is a very solid construction. Its not the fourth floor of an ordinairy building.

Like

@em1ss
Sorry, that photo is after the quake and tsunami, but before the hydrogen explosions. I don’t know if that’s helpful for what you were looking for.

Like

wouldn’t open anyways…. The vent stacks look like radio towers if anyone is trying to find a better photo. The one I had seemed to show one centered between the paired units….

Which logically would then imply an interface between units due t the common stacks for containment venting. Ultimately hydrogen too…

Like

Good photo Hank and yes. Looks like two stacks possibly for units 1 & 2, a single stack centered between units 3 & 4 pre-accident.

Like

@bchtdf1parrot Ok , you are correct. But Barry mentioning the “sloshing” before.I must admit I did not think of that , but the japanese engineers would be familiar with that , wouln’t you think? Again, hindsight is great in a situation like this.

Like

The stack left of unit 1 may not be a vent stack which is why I say possibly two for units 1 & 2. The other two stacks are centered between the units and in my judgement vent stacks for elevated release….

Like

hmmm, that seems to conflict with the sketch barry provided though of the unit locations…. Still unclear as his site sketch shows units 1 & 2 in the middle of the site. 3 & 4 to the left.

Like

I am still struggling with reaching a zirc water reaction on decay heat in an ambient environment that quickly. But it’s possible I guess to happen and generate enough hydrogen to blow Unit 4 reactor building up.

Like

night all, wishes for good luck for all that are struggling in Japan, at the nuclear site and the others suffering from the natural disasters.

Like

em1ss, on 20 March 2011 at 11:34 AM — Good evening!

From left to right the units are 4, 3, 2, 1 and then furthest right 5 then 6. The single vent stack furthest to the right is, in my opinion, for the Centralized Radiation Waste Treatment Facility.

In any case, that 3 & 4 share a vent stack clarifies several matters for me.

Like

Would those peole who are pushing the “5 people have already been killed at Fukushima” please tell us how they have been killed.
I can find no reference to anyone dying from radiation poisoning, but several to people having been crushed or having a heart attack.
All you do is create FUD to frighten people in Japan and around the World. I have relatives in Japan and all I want to hear are the FACTS not someone’s sick, premature interpretation of what has/will happen. That is wh
I think Barry should ban these obvious trolls but that is his decision.

Like

@bchtd1parrot 11.08
Sorry – I don’t understand your point. I think the MODERATOR was saying people who post their comments should check the rules before posting and that the mods were checking links for outrageous editing of them to suit the commenter’s opinion. Good on ’em. I agree the task is mammoth – maybe they are working in shifts:-)

Like

Re casualties from radiation, ABC has this in a story today:
“Six workers at a quake-stricken nuclear power plant have been exposed to high levels of radiation but are continuing working there, an official at the Tokyo Electric Power Co (TEPCO) said.

They have been exposed to more than 100 millisieverts of radiation.

“There has been no adverse effect on their health,” TEPCO’s Takeo Iwamoto said. It was not immediately known if they had been reassigned to different tasks.”
http://www.abc.net.au/news/stories/2011/03/20/3168579.htm?section=justin

As I understand it, the injuries & missing people are to do with either the tsunami, or the blasts from the hydrogen explosions – no casualties so far from radiation.

Like

Note also that the ABC article I quote above states that water contamination, while detectable, is 200 times less than the allowable safety limit.

Like

Here’s photos of R1 – 4. The R4 shot seems to indicate that the side with most damage is towards the turbine bdlg, not R3.

The time sequence for R4 also indicates a H2 explosion in R4.

As far as R3 vent vapors going to common vent stack and then backflowing to R4 and ending up in the building top, I think that is unlikely. High stacks have chimney draft effect which sucks on both R3 and R4 if common connection.

Like

bchtd1parrot, on 20 March 2011 at 11:57 AM — The possiblity of hydrogen making its way from #3 into #4 seems to have existed; recall that everything was subjected to ground motions from a stupendous earthquake.

Like

Ms Perps
Anyone having loved ones on that plant is not going to be watching the news, this blog or any other. He or she is going to be sitting before some altar, burning insence by the ton praying to all gods the door bell wont ring. This is a time of emotions. The question: “Did anyone cry wolf?” sounds like “Someone cried wolf!” only two blocks down the street. Thats a fact of life.
We hold the fort in case someone comes with a question and when he does we answer. No matter how ignorent the question. Someone finds a feed, he dumps it here. We look at it for answers. You will not find remarks here concerning cars, women or football.

Like

I worked at Tengiz with a single 300 m tall poured concrete stack serving 4 SRU/TGU units. Inside stack were 4 separate large SS pipes, each venting a unit separately, not interconnected.

Common stack does not mean commingled. Would have caught this on Hazops review.

Like

Armchair nuclear experts sprouting…

If you are worried about the radiation levels at the plant, the raising of allowable levels for the workers etc please read this excellent article to put you mind and rest and to confront the mis-information of posters like steviesmythes on BNC earlier.
BTW Barry’s blog is given a mention.

Like

Jogged memory – 2 poured concrete stacks, 1 300m other 100m. Each stack served 2 SRU/TGU and had 2 large SS pipe not interconnected.

Like

bchtd1parrot
I think we are singing from the same songbook here but we are both on a different key:-). BTW I am a long term visitor/commentator to BNC (from the outset) and am well aware what is to be found on BNC. Please don’t patronise me there are more important issues than male chauvanism rigt now.

Like

At Tengiz, the two vertical large dia SS vent pipes were inside the common poured concrete stack. The pipes were separated by at least 2 feet. If one pipe was damaged, the gases from that hole would have gone up the inside of the concrete stack and vented at the top. If 2 SS pipesdamaged, the same thing would have occurred. Since press inside stack is atmospheric, there is no delta pressure driving force to send gases backwards into units.(or R bdlgs)

Like

No male chauvenism on this side, i am a bit like a doggy in this kind of situation. Someone points a finger, i bite. This is no time to blame whoever for whatever. Thats what i believe. Thats not meant to partonise anyone, least of all someone who is, like you say, singin’ from the same songbook. I do not mean to offend you or any other in any way. That risk i will run later. I’m sitting on a brainfart i cant let fly without an active monitor, too risky. And for what its worth, i’m glad youre here.

Like

Two bits I recall– units 3 and 4 share a common control room. And the “negative air pressure” system” when operating kept any radiation away from the operators in the control room. That (warning, logic …) must mean it pulled away anything vented from the reactor and fuel storage in the form of gas, and so would also include hydrogen).

So (warning, pure speculation) a failure of the ventilation fans/negative air pressure system would mean that any gas that should have been pulled out and through a carbon filter in the usual way would instead go — wherever the wind took it.

I know it takes very little difference in air pressure to change airflow around and through a building–a breeze will do it, and the airflow will change with the wind direction.

So assume first it accumulated at the top of Unit 3, and when that blew off, remembering it was near freezing and no heat, would they have closed doors inside the building to stay warm? Without forced ventilation, some of the lightweight hydrogen could have been carried through the common control area, wherever that is, and ended up in Unit 4 — whatever there was could accumulate in whatever dead air space there was in the upper reaches of Unit 4. The different explosion–lower down–might be from hydrogen being carried in through a common shared building or vent, but trapped inside below the roof deck space? Add one ignition source …

I recall for gas combustion appliances (heaters, hot water heaters) of the type built for “sealed combustion” (they breathe outside air and exhaust to the outside) the installation rule is that both the intake and the exhaust vent have to be on the same side of the building, perhaps even concentric — because if they’re around a corner from each other, airflow over the building can be enough to reverse the airflow through the combustion chamber.

End wild speculation. Time will tell.

Like

I’m only raising possibilities, not assigning probabilities. I fail to see any probable source of the explosion of #4, yet the damage is considable [shown in the link given a bit upstream].

Like

@David B Benson 12:42: Isn’t H2 generated from R4 SFP low water and hot fuel assemblies a potential source? Is it probable?, well we at least know that it didn’t come from R4 reactor vessel or primary containment since that had no fuel assemblies. The H2 backflow from R3 (damaged at the time) to R4 via common vent stack seems to me to be unlikely.

Like

Thanks Leo, so U4 explosion must have been from U4 SFP. What bugs me is that ( Correct me if i’m wrong) that SFP has concrete damage to some depth. That doesnt make sense to me. Its just a bit of bang gas. Large surfaces like the roof ok, but concrete? Considering its the same kind of concrete that survived a 9.0 quake and its a part that would not likely be challenged by the quake itself, that seems odd.

Like

bchtd1parrot: Earthquake is strong shaking motion laterally and is considered in design. A confined vapor explosion of H2 and O2 creates strong outward pressure blast force and could rupture walls. The only thing that confuses me is that the green platform and machinery in the R4 photo did not looke overly damaged…however it was surrounded by blast not trying to confine blast.

Like

If you look at that explosion, you can see a lot of stuff fall right back down. Perhaps concrete panels fell and struck something

Like

Leo Hansen, on 20 March 2011 at 12:54 PM — I find that source for the #4 explosion highly improbable for two reasons, one being the location of the damage to the external structure. That does not mean I disregard that possibility; it only means that it is now but one of three possibilites none of which seem very likely.

The damage assessment will eventually be done and presumably we will be able to read (at least) the conclusions of the resulting report. In the meantime I’m a bit disapointed in WNN to have so firmly stated a conclusion which is at odds with a helicopter siting of water still remaining in the #4 spent fuel pond [before the various rewaering exercies to that #4 SFP].

Like

http://www.world-nuclear-news.org/RS_Fuel_pond_work_at_Fukushima_1903111.html

“Holes have been bored through the roofs of reactor buildings 5 and 6 in an 11-hour operation to ensure that hydrogen can disspate naturally. Each unit has three holes measuring seven centimetres. Tokyo Electric Power Company did not say that hydrogen was being produced, but that the move to bore holes was a precaution.”

Does anybody know how they managed to cut/drill/bore holes through the roof of reactors 5 and 6? From outside? From the inside?

Also I would have thought that there would be “blast panels” or doors as part of the original design to prevent the kind of damage that was caused by the explosions/over pressuring that we have seen in #4.

Like

So we have several variables here. There’s the draft through the control room, the afterdraft from the blast at U3, the tendency of hydrogen to go up, the tendency of cold outside air entering through U3 to go down and turbulence of those last two. It must have been a hydrogen explosion, or at least gas. The crane is almost spotless. My explanation for that is that it suffered pressure from all sides meaning it was ‘inside’ of the explosion.

Like

I have worked in many control rooms and never was the HVAC connected in any way to process systems piping or vents. The reason is that process/safety sytems can have high pressure gasses that would backflow into HVAC and not be safe.

Like

Another image

this one shows, just above-right of center, a white linear feature connecting the base of the tall tower and branching to both reactor buildings 3 and 4. I’d _speculate_ that is a ventilation duct meant to carry air drawn from both buildings and send it up and out the tower high above the site. (Those tall towers are ventilation exhausts? Anyone confirm? There are four towers — one between each pair of reactors, and one for the building off to the side that I think is the common storage pool.

Anyone know? There’s something that might have been the same design between buildings 1 and 2, but incomplete — either broken or covered by darker material.

Like

Japan’s wind industry hails earthquake-resilient turbines

Japan’s wind turbines survived last week’s earthquake and as a result utilities have now asked wind farm operators to boost power output to make up for energy shortages in the country, the leader of the Japanese wind energy association has revealed.

(emphasis mine)

Imagine the response from the wind farm operators… “Sure, not a problem. We’ll get right on to that. Just waiting for the wind to pick up…“

Like

Latest news on NHK says that power is restored to units #5 and #6, and water temps in those SFPs are dropping significantly. Water cannons were directed at #4 this morning and now they are taking a break to get some electrical work done around there. Water operations to resume this afternoon. Equipment is being evaluated at units #1 and #2 prior to powering anything on there. 良し, that’s all from me for now.

Like

Did you watch the clip somewhere around the top of the post? Its only a simulation, but they indicated the halfway submerged rods as red hot from just over the surface. The way i see it, those rods start generating H2 the moment they stick their heads over the pool surface. They may generate heat like wild, but not or hardly conduct it.

Like

bchtd1parrot
Thanks for that. I think all our nerves are a little on edge right now and not many of us have had a lot of sleep. Oh to be young again and be able to switch off and fall asleep as soon as your head hits the hits the pillow :-)

Like

JAIF damage reports after R3 Mar 14 blast on did not indicate damage to R4. That was reported only later. I believe that R3 blast effects did not cause R4 damage.

Like

@Tom Keen, on 20 March 2011 at 1:15 PM,

Wow what kind of BS is coming from the Japanese wind energy association? I suppose they are going to claim they’re powering all of Japan now as if nothing else is running.

We need a report of how the other nuclear plants are doing all around Japan at this time.

Like

Leave a Reply (Markdown is enabled)