Japan Earthquake: Nuclear Plants at Fukushima Daiichi

Click For Summary

Discussion Overview

The discussion revolves around the technical aspects and current status of the nuclear plants at Fukushima Daiichi following the earthquake and tsunami in Japan. Participants are seeking reliable information regarding the operational conditions, safety measures, and potential risks associated with the nuclear reactors in the aftermath of the disaster.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants express skepticism about the reliability of media reports and emphasize the need for technical information from official sources like TEPCO and METI.
  • There are concerns regarding the reactor pressure levels, with reports suggesting that pressure may have exceeded safe limits, which some participants describe as a significant issue.
  • Questions are raised about the likelihood of a meltdown, with differing opinions on whether this is a realistic concern or media exaggeration.
  • One participant explains the role of coolant in a nuclear power plant, noting that it is essential for cooling the reactor and managing decay heat after shutdown.
  • There is discussion about the reactor's ability to be scrammed (shut down) and the implications of losing coolant, with some participants clarifying that decay heat continues to be produced even after shutdown.
  • Concerns are raised about the explosion of the containment building and its implications for safety, with speculation about the potential release of radioactive materials.
  • Participants discuss the wind direction at the time of the explosion and its potential impact on the dispersion of any radioactive materials released.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the likelihood of a meltdown or the implications of the current situation at Fukushima Daiichi. There are multiple competing views regarding the severity of the situation and the reliability of information being reported.

Contextual Notes

Participants note the limitations of available information, including the reliance on second-hand reports and the challenges in verifying the status of the reactors and containment structures. There are also unresolved questions regarding the operational status of safety systems and the exact nature of the explosion.

  • #6,391
jim hardy said:
Well in order to melt either the Boral metal or the Boraflex plastic, the fuel would have to be not under water. Then it could melt, if the water were gone. But without water it can't go critical.

By the time fuel became partly uncovered and the rods heated up to >700C, the space between the fuel rods would be filled with superheated steam. Also the space above the fuel, up to the top of the SFP, would be filled mostly with hot steam (except for some air flowing down by convection). Would that be enough water to allow for criticality?

The density would be much less than liquid water, but the volume would be much larger than inside a reactor's core. I presume that fast neutrons that escaped upwards or sideways would not be readily absorbed, and so would eventually be slowed down and scattered back to the fuel. Here I am thinking by analogy with light that falls onto a deep cloud deck: since it is scattered but not absorbed by the water droplets, it will all eventually scatter back out, exiting on the same side it entered --- no matter how rarefied the cloud dech is. (That is why large clouds look white on the sunlit side, and black on the other side). In the above scenario, H2 nuclei and neutrons would substitute for water droplets and photons.
 
Engineering news on Phys.org
  • #6,392
Jorge Stolfi said:
At the southwest corner of unit #3.
this is correct the frame is still there but the thin concrete seems gone? or may bi it is the white structure at the bottom of the picture (unlikely though)


New video on Tepco press downloads - this time it's about SFP#3!
=> at last .. we don't see much beside lots of roof structure fallen into the pool
 
  • #6,393
Jorge Stolfi said:
Also, lubricating oil should not create an explosive mixture with air, unless it is heated to its boiling point, which presumably is >>100 C.

As fas as I have understood the current view of TEPCO is that at the unit 4 there was first an explosion and only afterwards fire. At least this is the impression I have got when reading TEPCO's/government's press releases.

I think one could achieve the best results by taking somehow seriously this new information coming from the press and trying to combine it with the theories presented here and try to see does it lead somewhere.

The general fire point of lubricating oil is probably somewhere betweeen 200 - 300 degrees celsius.

We could also think that this oil is in responsible for the fire but not for the explosion.

Is it possible that the explosion could have immediately heated a small part of the oil over fire point and also ignited it? The result of this would be a couple of fires here and there that would be extinguished by itself?

The explosion itself could be explained by AntonL's theory (radiolysis) or something else.
 
  • #6,394
Jorge Stolfi said:
* The artwork on #1's exterior walls is symetric about the NW corner.
I'm fairly certain the artwork is symmetric on all the RBs with respect to the NW and SE corners.

Rive said:
Oooops! http://www.tepco.co.jp/en/news/110311/images/110510_1.zip"
Oh my.
 
Last edited by a moderator:
  • #6,395
oil fire ? but where is ignition source ? reactor was without power source so only hot thing could be fuel...
 
  • #6,396
I know I was moaning a lot the other day about people posting images from the live feed and getting hopelessly carried away with ideas about what they are seeing, but now I am going to do the same!

The attached picture was captured from the live feed by me about 10 minutes ago. Whats up with unit 2 building and the large dark rectangle on the west wall?
 

Attachments

  • Unit2May10th.jpg
    Unit2May10th.jpg
    12 KB · Views: 568
  • #6,397
SteveElbows said:
I know I was moaning a lot the other day about people posting images from the live feed and getting hopelessly carried away with ideas about what they are seeing, but now I am going to do the same!

The attached picture was captured from the live feed by me about 10 minutes ago. Whats up with unit 2 building and the large dark rectangle on the west wall?

This is big crane under damaged roof, but it is unit 1 not 2
 
  • #6,398
razzz said:
Anyone use .docstoc? Can you open this link for this document... http://www.docstoc.com/docs/7254461/Reactor-Pressure-Vessel-Issues-Printable-Version

Here's the link to the PDF at the NRC's site: http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/prv.pdf"

First post here. I've been reading this thread since around the #350th post and I'd like to thank all the contributors. I've learned an incredible amount about nuclear physics and the engineering of nuclear reactors.

Keep up the good work. Back to lurking...
 
Last edited by a moderator:
  • #6,399
SteveElbows said:
I know I was moaning a lot the other day about people posting images from the live feed and getting hopelessly carried away with ideas about what they are seeing, but now I am going to do the same!

The attached picture was captured from the live feed by me about 10 minutes ago. Whats up with unit 2 building and the large dark rectangle on the west wall?

I think the dark rectangle is the south wall of unit 1. Have a look at this new picture from the set recently posted:
http://www.flickr.com/photos/xtcbz/5705865264/in/set-72157626687253144/

Unit 2 looks fine.
 
  • #6,400
elektrownik said:
This is big crane under damaged roof, but it is unit 1 not 2

Aha yes, thanks, I made a very simple and stupid mistake. Sorry about that!
 
  • #6,401
About unit 3 from tepco news:
- From 4:18 pm on May 8th to 5:41am on May 10th, we drained the water from
the condenser of the turbine building in Unit 3 as a preparation for the
water injection to the reactor through Feeding Water System.
 
  • #6,402
Jorge Stolfi said:
* There are still lots of spaghetti-like grey rods among that mess at the NW corner of #3. (Rebar? Shouldn't it have rusted by now?)

Steel wire?
 
Last edited:
  • #6,403
elektrownik said:
This is big crane under damaged roof, but it is unit 1 not 2
crane? That in my opinion is the high voltage overhead line tower.
[PLAIN]http://k.min.us/inkOf6.JPG
 
Last edited by a moderator:
  • #6,404
jim hardy said:
Well in order to melt either the Boral metal or the Boraflex plastic, the fuel would have to be not under water. Then it could melt, if the water were gone. But without water it can't go critical.

Would this qualify as a crude nuclear reactor (with steam as neutron reflector/moderator):

sfp-criticality-5.png


EDIT+: Imagine that the water is boiling vigorously, so the steam is heating up as it flows along the hot fuel tubes; but leaves the racks when it is still well below 800 C, so the assembly heads (where no heat is being generated) remain relatively cool and undamaged.
 
Last edited:
  • #6,405
Rive said:
Oooops! http://www.tepco.co.jp/en/news/110311/images/110510_1.zip"

I had feared it would look bad judging by the drone pictures, but this is just terrible.

It's a bit confusing and I yet have figure directions out, but where's the fuel? How sturdy are spent fuel racks normally?
 
Last edited by a moderator:
  • #6,406
Has this series of videos shot inside a Japanese nuclear plant been posted before?

http://www.youtube.com/user/Anjiin#p/u/0/Hv9Ev02fZxg

Its not Fukushima, but I found them fascinating. When they are working on the reactor we can see several items of equipment that are familiar from our Fukushima discussions. And I found the videos numbered 003-005 to be quite fascinating, they are dealing with something radioactive, and we can see how they measure dose, remove lead-lined blankets, hide behind other shielding, and lower this item down to another level. I'm especially fond of the bit near the end where they appear to be randomly hitting it with planks of wood!
 
  • #6,407
ascot317 said:
I had feared it would look bad judging by the drone pictures, but this is just terrible.

It's a bit confusing and I yet have figure directions out, but where's the fuel? How sturdy are spent fuel racks normally?

IMHO it doesn't say anything about the fuel - it can be a complete mess, but it deosn't have to. All we see is that it is covered with rubble. Not a good sign, but IMHO too early to draw far fetched conclusions.

At this stage - especially when planning further actions - it would be better to assume it is a mess, but we won't know before removing the rubble. I guess analysis (chemical/radiological) of water would give much better information about the fuel than this video does.
 
  • #6,408
Point of detail ... in there is a red paper probe with some Japanese writing on it
50 / 60 /70
After the probe is submersed it measure 50..
***
"But where's the fuel? " take your pick
A) below
B) gone (gone where ?)
 
  • #6,409
SteveElbows said:
Has this series of videos shot inside a Japanese nuclear plant been posted before?

http://www.youtube.com/user/Anjiin#p/u/0/Hv9Ev02fZxg

Its not Fukushima, but I found them fascinating. When they are working on the reactor we can see several items of equipment that are familiar from our Fukushima discussions. And I found the videos numbered 003-005 to be quite fascinating, they are dealing with something radioactive, and we can see how they measure dose, remove lead-lined blankets, hide behind other shielding, and lower this item down to another level. I'm especially fond of the bit near the end where they appear to be randomly hitting it with planks of wood!

Looks like they are beating lead shielding sheets into form-fitting shape.
 
  • #6,410
at the center of the picture, could the 2 squares be melted rod ?
[PLAIN]http://i.min.us/ing7TC.jpg
 
Last edited by a moderator:
  • #6,411
When I watched video it looked to me more like top of the fuel assembly, similar to those we have seen in the other SFP. Hard to say how destroyed, if melted and so on.
 
  • #6,412
I think that's Tsuruga 2, a PWR.
 
  • #6,413
|Fred said:
Point of detail ... in there is a red paper probe with some Japanese writing on it
50 / 60 /70
After the probe is submersed it measure 50..

It says "Thermo Label." The dot at 50 means the maximum temperature the label has experienced is 50 degrees or more. No dot at 60 or 70 means the maximum temperature was less than 60. (Once an indicator dot discolors, it is permanent.)
 
  • #6,414
Borek said:
IMHO it doesn't say anything about the fuel - it can be a complete mess, but it deosn't have to. All we see is that it is covered with rubble. Not a good sign, but IMHO too early to draw far fetched conclusions.

At this stage - especially when planning further actions - it would be better to assume it is a mess, but we won't know before removing the rubble. I guess analysis (chemical/radiological) of water would give much better information about the fuel than this video does.

Yeah, I was merely stating that I was unable to identify anything that's "supposed" to be there (except for water xD). I see rubble and I wonder how much the racks can bear.
 
  • #6,415
razzz said:
Anyone use .docstoc? Can you open this link for this document... http://www.docstoc.com/docs/7254461/Reactor-Pressure-Vessel-Issues-Printable-Version

It opened flawless for me...

Adresses various cracks and degradations on RPV and especially PWR's RPV covers...

On this matter, and even if this is a lit bit OFF TOPIC because it's about a PWR MODEL, I wanted to mention this study with impressive cracks and holes (football sized! see the pictures and diagrams) discovered in Davis Besse PWR reactor cover head (Ohio).

http://www.nrc.gov/reading-rm/doc-collections/nuregs/brochures/br0353/br0353r1.pdf

Even if it may be PWR specific, it's interesting to note that it was caused by boric acid leakage (borated water) that has eaten the steel of the head to a point where only the stainless steel cladding inside the cover head was left for structural resistance (3/8 inch!). Any breakage of this (small) remaining thickness would have resulted in a Loss of Coolant (LOCA) accident...

Ok, now back to BWRs:

1) borated water is not normally use inside BWR, but it is used now since the beginning of the accident at Daichi. So a logical question question relates to the effect of this borated water injected in addition to seawater inside BWR reactors (this is "beyond design basis" operation!) for a time that could be long: what could be the impacts on non stainless steel materials for example (corrosion, etc.)?

2) this study shows clearly that as already mentionned before, the place of penetration of various holes, control rods and equipments inside the reactor, with welded parts, is always a weak point and a leakage source. In a BWR, most of these penetrations holes are at the bottom (control rods,etc.).

Something of general interest, because this is NOT PWR or BWR dependent, is also highlightened in this study concerning the reasons why this major damage wasn't discovered before during regular inspection:

Firstly, a lot of the regular inspection planned where... deferred -ending up discovering this much too late!

The staff made several changes to the process to enhance the NRC’s ability to detect declining plant performance, including the specific issues identified at the DBNPS. For example, the review of the event indicated the deteriorating condition had been underway for several years and that the planned inspection, maintenance, and modification activities that could have prevented, or enabled earlier discovery of the condition were frequently deferred.

Secondly the lack of culture of safety at this Davis Besse plant!

Safety culture weaknesses at Davis-Besse were determined to be one of the root causes of the reactor vessel head degradation event.

As we have in France mainly PWR's reactors, I'm wondering what is the situation on this subject of reactors vessels damages with time. I'm going to document on this after reading this NRC document!
 
Last edited by a moderator:
  • #6,416
thank you BoreK to correct my poorly chosen word "top of the fuel assembly" was the word I was looking for. melted is my assumption

Thank you rowmag, as usual.
 
  • #6,417
  • #6,418


Borek said:
See link below. The energy was there.

You don't need a tube, glass is enough to see what may happen. http://www.youtube.com/watch?v=1_OXM4mr_i0&feature=fvsr Or google for Old Faithful eruption.

See cphoenix posts, he tried to estimate amount of energy in the heated water and they were really impressive https://www.physicsforums.com/showpost.php?p=3250188&postcount=3914 - and even if there were enough to vaporize "only" 2% that still means very large volume of steam. That would be on top of initial destruction done by the hydrogen detonation. So the hydrogen blows the walls/roof, then steam erupts, adds to the destruction and sends a mighty puff into the sky.

Yep, vertical component would be mainly water geyser after hydrogen kaboom.

see earlier posts about exactly this occurring:

https://www.physicsforums.com/showpost.php?p=3230983&postcount=2949

https://www.physicsforums.com/showpost.php?p=3231247&postcount=2973

https://www.physicsforums.com/showpost.php?p=3232329&postcount=3054
 
  • #6,419
rowmag said:
Looks like they are beating lead shielding sheets into form-fitting shape.

Yes, videos 3 to 5 are indeed very impressive of real life nuclear waste management from the view points of workers! Not very high tech looking and far from glossy paper nuclear marketing show!

http://www.youtube.com/user/Anjiin#p/u/17/rLIQlJGr-8E
http://www.youtube.com/user/Anjiin#p/u/16/jkI85Mzj7s4
http://www.youtube.com/user/Anjiin#p/u/15/1Dcg2_YGtZ0

Need some base ball skills to flatten lead shielding it seems...

Also video N°16 with the Hair dryer procedure to collect water (probably with some contamination) from this small equipement!

http://www.youtube.com/user/Anjiin#p/u/6/00-8C7T4iO4
 
Last edited:
  • #6,420


Borek said:
<..>
See cphoenix posts, he tried to estimate amount of energy in the heated water and they were really impressive https://www.physicsforums.com/showpost.php?p=3250188&postcount=3914
- and even if there were enough to vaporize "only" 2% that still means very large volume of steam.

cphoenix is calculating with a sfp holding 1E4 tons of water, for a Fukushima sfp, 1E3 is closer to fact. So using his method, we'd end up with as much as 20 tons of water evaporated, 30000 m3 of steam 1 bar, or a 30 meter cube.

That would be on top of initial destruction done by the hydrogen detonation. So the hydrogen blows the walls/roof, then steam erupts, adds to the destruction and sends a mighty puff into the sky.

However there are physical limits to the mightiness of 20 tons of water vapour. It's lifting power would be at most 20 tons, equal to its own weight. I think the mighty puff we saw lifted substantially more than that.
 

Similar threads

Fukushima Fukushima Daiichi nuclear disaster discussions
  • · Replies 12 ·
Replies
12
Views
49K
Ukraine nuclear power plant Zaporizhzhia on fire
  • · Replies 41 ·
2
Replies
41
Views
5K
Fukushima Japan Earthquake: nuclear plants Fukushima part 2
  • · Replies 2K ·
60
Replies
2K
Views
458K
Fukushima Are US Nuclear Power Plants Prepared for Earthquakes?
  • · Replies 5 ·
Replies
5
Views
6K
Fukushima Critiques of Fukushima Thyroid-Cancer Study
  • · Replies 2 ·
Replies
2
Views
2K
What if a nuclear power plant loses outside electricity?
  • · Replies 6 ·
Replies
6
Views
20K
Japan Earthquake: Political Aspects
  • · Replies 763 ·
26
Replies
763
Views
278K
Fukushima How will they end the Fukushima disaster?
  • · Replies 38 ·
2
Replies
38
Views
16K
Thoughts on nuclear power and disasters [long, rant/tangenty]
  • · Replies 6 ·
Replies
6
Views
4K
Fukushima The geological issues of the Fukushima Daiichi
  • · Replies 4 ·
Replies
4
Views
12K