Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[shogun338]

They were mixing an aqueous solution of highly enriched (~18.8% U-235). The BWR fuel at Fukushima is ~4%.

In the case of Tokaimura, it would be a combination of neutrons and gamma radiation, and those exposed were inches from the vessel. One guy apparently collapsed onto the vessel.
http://en.wikipedia.org/wiki/Tokaimura_nuclear_accident

In the Tokaimura accident neutron beams traveled a distance of 500 meters and exposed civilians to 1mSv per hour during the 20 hours of the criticality .They also saw a blue flash in the room when they mixed in the last bucket . This seems like a lot from such a small accident . In the case of Fukushima there's way more fuel laying around . Does the fuel being 4% make that big of a difference ? What about the MOX fuel ?

 

[Astronuc]

In the Tokaimura accident neutron beams traveled a distance of 500 meters and exposed civilians to 1mSv per hour during the 20 hours of the criticality .They also saw a blue flash in the room when they mixed in the last bucket . This seems like a lot from such a small accident . In the case of Fukushima there's way more fuel laying around . Does the fuel being 4% make that big of a difference ? What about the MOX fuel ?

The enrichment is very significant with respect to criticality, and the fact that fuel is normally heterogenous, i.e., separate from the coolant. However, if a large amount of fuel is exposed to coolant, and becomes soluble, that's an entirely different matter. However, the enrichment is still critical.

What about the MOX fuel? It's in the core. Even if the core achieved criticality, from essentially a zero power configuration, it's in the core. The neutron flux is not going to be as intense as it was under full power operation, so there is no way that it would create a 'neutron beam'.

If the fuel were dispersed outside of the core, e.g., in the torus, then it is much less likely to achieve a critical configuration becuase of the less favorable geometry.

 

[NUCENG]

OK, that analysis fits pretty darned well compared to my earlier guesstimate:

https://www.physicsforums.com/attachment.php?attachmentid=33874&d=1301669768

https://www.physicsforums.com/attachment.php?attachmentid=33875&d=1301672183

Even the shadow on the south side of Bldg 4 lines up.


Here are a couple of additional questions for critical analysis by someone who knows and can critically analyze photos for that sort of thing, Anton:

Do the size, number and distribution of the rod like objects in this photo fit the description of the number of 4 meter x 3 cm (roughly?) individual fuel rods that might be in a single fuel rod assembly?

http://i306.photobucket.com/albums/nn270/tcups/64f1c409.jpg

Does it make sense that a flying fuel handling machine would drag an attached single fuel rod assembly behind like the tail of a kite and that the fuel rod assembly would smash open on top of the bulk of the FHM as the FHM impacts the building?

Do the girders about the proposed NE corner impact site look to be bent downwards vs the upward and outward bending at the blast site on the SE corner?

A 10x10 fuel assembly has individual fuel rods with a top plate and handle assembly, a bottom plate and nozzle, and three spacer plates. All rods are inserted through the spacer plates.

Fuel assemblies are not robust structrures. I have seen results of dropping new fuel assemblies prior to channeling which resulted in significant tamage to rods. They do not tolerate even small twisting or side loads. That is part of the reason each fuel assembly is also wrapped with a fuel channel, a square tube running the full length of the assembly. They remain channeled after the assembly is discharged to the spent fuel pool.

I know it is tempting to look for fuel rods, but I wouldn't be looking for 12 ft long intact rods. You are expecting these rods to find a way to get loose of its spacer plates and shroud after an explosion that was strong enough to blow the FHM sky high? I have a hard time accepting that.

 

[shogun338]

Astronuc will the radiation meters the workers have detect if they walk near neutron beams? What is your opinion of the neutron beams that was reported earlier at the plant ?

 

[Astronuc]

Astronuc will the radiation meters the workers have detect if they walk near neutron beams? What is your opinion of the neutron beams that was reported earlier at the plant ?

The radiation detectors could detect some radiation, and certainly gammas. I don't understand the context of 'neutron beams'. I don't know what detectors are involved.

If they were having re-criticality, then that is a serious problem. It would be a significant violation of safety protocols.

 

[TCups]

A 10x10 fuel assembly has individual fuel rods with a top plate and handle assembly, a bottom plate and nozzle, and three spacer plates. All rods are inserted through the spacer plates.

Fuel assemblies are not robust structrures. I have seen results of dropping new fuel assemblies prior to channeling which resulted in significant tamage to rods. They do not tolerate even small twisting or side loads. That is part of the reason each fuel assembly is also wrapped with a fuel channel, a square tube running the full length of the assembly. They remain channeled after the assembly is discharged to the spent fuel pool.

I know it is tempting to look for fuel rods, but I wouldn't be looking for 12 ft long intact rods. You are expecting these rods to find a way to get loose of its spacer plates and shroud after an explosion that was strong enough to blow the FHM sky high? I have a hard time accepting that.

Me too, but there it is. Most of the force of the blast was going upward, pushing on the fuel handling machine. The fuel rods just got carried along for the ride, not blasted skyward. The spacer plates burst when the fuel rods hit the building.

Here's a question. I bet the new fuel rods are more brittle than the spent fuel rods. From what little metallurgy I know, the heating in a nuclear reactor, then cooling in a SFP, and then maybe heating them again in the explosion might make them less brittle. There do appear to be a few fragmented ones, but few if any appear bent.

The odd thing is that we, the lay public, will most likely never know the exact details, unless Astronuc gets busy, goes over there, and gives us the first hand scoop.

Someone tell me about superheated steam as an explosive propellant, please.

Would steam be more likely to cary a heavy piece of equipment skyward than, say, the heat from a hydrogen blast? I know live steam is a special kind of hot gas with a lot of energy density. The only way I can seem to get enough oomph directly under the FHM to launch it like that, mostly in one piece (if my PhotoShop'ed picture is correct) is, perhaps, for the initial hydrogen blast to take out the roof and then, have the superheated steam from the SFP to to launch the FHM skyward immediately following the hydrogen blast. If freeze frames from a shaky video from way far away are sufficiently informative, that may have been what happened.

 

[Cire]

Differential pressure is something to consider for those trying to figure out where things might or might not have moved inside the building during the explosion.

The internal component would experience with some exceptions equivalent pressures across all their surfaces. (flame propagation from one side to the other of the building will have an effect and cause some pressure transients for a few microseconds). However, its the large differential pressures that move things around.

From an engineering prospective the roof's of the damaged building need to be cut out and removed as soon as possible. The solution is to setup a crane system that cables across units 1-4. With a cable drop and a shear/grapple the upper structures can quickly be cut down and transported away. This can be done remotely. This makes the SFP's serviceable and the upper containment structures clear for inspection. It also allows a bucket system to transfer water into the pools. I suspect a large portion of the radiation leaking is from crushed fuel elements in the spent pools leaking out as the pools are overfilled or leak. Unpressurized fire suppression systems that are clearly broken also provide a fluid path into other structures if they're connected to common mains.

For clearing the random iron/steel components a large electromagnet can suck up most of the building infrastructure that isn't stainless steel. Large chunks of concrete can be picked up with a smaller grapple.

You run a video system on an adjacent cable system similar to those seen at profession stadiums. This let's you do the work safely from a distance. Concrete bases and foundations need to be poured or blocked in for the cranes asap. Debris is transported and put into a storage pit if contaminated until it can be properly disposed of.

A large temporary on site storage pool needs to be constructed asap and a system to move the fuel into that pool setup.

 

[NUCENG]

The video of the blast is taken from the southwest. We see two walls of each reactor building, the south wall in the sun to the right, and the west wall in the shade, to the left. The middle antenna separates one from the other the other in the picture. That is, we see it aligned with the south-west edge of the building. Is that of any help?

I think I've finally figured out what everyone has been calling "antennas" The very tall structures are roughly 200 meters tall. They are the Offgas Stacks. During normal opearion steam and noncondensibles including raqdioactive isotopes are dran of the condensers through steam jet air ejectors and the offgas system then holds the effluent or filters it prior to release theough the offgas stack. During emergencied the Standby Gas Treatment System SBGTS of SGTS maintains a negative pressure in the secondary containment to route all potential leakage through filters and then to the stack for elevated release which increases dispersion of the leakage. If the plant has a hardened vent capability, when the containment is vented it also goes through the filters and stack. Don't need the first function (Offgas) once the turbine is tripped. Of course with the roof blown off the second function is gone. If indeed the containment is breached then the third function is also gone.


Once again, you can design systems to be foolproof. It is unfortunately not possible to make them damnfoolproof.

There is a third elevated stack on the site which has four pipes opened at the top. I believe this is a common release point for the turbine buildings and common fuel pool exhausts. These are additional potential release paths to the environment in other design basis accidents. Elevation aids dispersion and ensures these paths can be monitored to measure any release.

 

[TCups]

Differential pressure is something to consider for those trying to figure out where things might or might not have moved inside the building during the explosion.

The internal component would experience with some exceptions equivalent pressures across all their surfaces. (flame propagation from one side to the other of the building will have an effect and cause some pressure transients for a few microseconds). However, its the large differential pressures that move things around.

So, you seem to be saying that, yes a hydrogen explosion in the upper portion of the building would blow the walls and roof away, but, essentially just drop heavy structures within the inner volume of exploding hydrogen, like the overhead crane, right where they were when the hydrogen exploded (the crane's sidewall supports were blown out), and, also like in the explosion of Building 4, where the FHM is still pretty much just over the SFP and hasn't moved much from the hydrogen blast.

In my proposed scenario, then, a large differential pressure would have to develop from the underside of the FHM, that is, from the SFP. If it were only hydrogen gas in the SFP, then there wouldn't be much pressure differential on the underside of the FHM, but if there were residual hot or boiling water that vaporized from the heat of the blast, explosively expanding from liquid to gas phase, then the FHM would have a pretty big pop gun under it and there would be a very big, vertical blast that would lift it upward into the sky.

Addendum:

Which leads to another line of questioning -- if the water in the SFP of Bldg 3 vaporized and a steam explosion occurred, then why didn't the same thing happen in Bldg 4?

Answer: The hydrogen blast from Bldg 3 came primarily from the drywell containment, not from the hydrogen generated in the SFP. The hydrogen blast from Bldg 4 came from hydrogen generated in the SFP, and this only occurred after most of the water had boiled off and there was little or no water left to convert to steam in the SFP of Bldg 4.

And yet another thought:
The differential pressure from the steam explosion would not tend to blow the fuel rods out, especially if they were in racks bolted to the floor of SFP3. The only reasonably intact fuel rod assembly that came out of the SFP had to be dragged out by the FHM.

 

[Bez999]

@Tcups: In addition, the fuel assembly that would in that scenario be attached to the FHM, would be protected from the blast as it was under water. The FHM would be send skyward with the assemply dragging behind it. Once the machine reaches the zenith of its parabolic track, the attached assembly, hanging off the boom, would swing in its path, centrigugal forces resulting from the FHM "tipping" holding everything in place. When the whole thing lands on top of the building again, the FHM lands first, slightly under an angle. The boom and assembly, still describing an arch, hit the building on their side, i.e. on one side of the channel. Compare taking a packet of spaghetti and swinging it on a piece of string, hitting your kitchen bench. The kinetic energy in the system spills the rods straight out, instead of smashing them. This also explains they are still close together.

 

[AntonL]

Would we have a different picture today if 1000 engineers where mobilized on day one instead of offering this help three weeks later

GE CEO to meet with Japan industry minister to offer support
TOKYO, April 1, Kyodo

The head of General Electric Co., the U.S. manufacturer of reactors at the crisis-hit Fukushima Daiichi nuclear plant, will hold talks on Monday with Japanese industry minister Banri Kaieda to offer support to Tokyo in tackling the ongoing emergency, Japanese officials said Friday.

Jeffrey Immelt, chairman and chief executive officer of the U.S. conglomerate, will meet with the minister together with Hitachi Ltd. President Hiroaki Nakanishi. The Japanese firm is a supplier of reactors to Tokyo Electric Power Co., which operates the atomic power station crippled by the March 11 killer quake and tsunami.

Immelt is also expected to visit the office of the operator known as TEPCO, the officials said.

GE has said it will offer technical assistance to the Japanese government and TEPCO by mobilizing more than 1,000 engineers of Hitachi-GE Nuclear Energy Ltd., a joint venture of the two companies.

The U.S. maker has also offered to provide 10 gas turbine generators to help Japan tackle an energy supply shortage following a request from TEPCO.

==Kyodo

 

[jferello]

I would like to thank everyone for all the information they have posted here, it has been so exciting to learn so much about Nuclear power generation.

1) Astronuc - You are so freakin smart!

2) TCups - Nice forensic work, it was almost like reading a book. I must say though I was getting stressed out seeing all the work you have put into your posts, I could never do all that :)

3) From the information we have currently, is it safe to assume that everything could have been prevented if the plant never ran out of power?

4) If this happened in the states I would hope that we would be able to mobilize tractor-trailer sized generators & have them patched in within 8 hours?

5) Why would it take several days to run electrical connections from the grid back to the plant? Could you not just block off roads, fields etc. and just unspool a giant cable within a few hours?

6) Why do Nuclear plants have emergency hookups? Why not have 'ports' outside the reactor buildings for fire hoses to connect to that would shower the SFP with water? I understand that they need to have a closed system to prevent accidents, but if an accident does occur then they have no recourse it seems.

7) Again I saw some posts about not having the right generator types, 50 vs 60hz or not being able to splice into the system. Why would they not have an emergency hookup area for extra generators, batteries or external power lines? They could have all the transformers, cables, converters etc. to make connecting so much faster.

8) Could someone design a system where when power is lost that the reactor vessel is continually filled with liquid nitrogen? Please don't berate me for this question, I know nothing about interactions between chemicals, I just know that the reactor is very hot and liquid nitrogen is very cold.

9) Do Nuclear plants not have water towers or large storage areas for emergency fresh water, so they can run for a couple days without having to resort to sea water?

10) Finally I keep reading that x amount of radiation is lethal, but I have yet to read anywhere what happens if you get a lethal dose. Like what would happen if someone walked into a room with lethal amounts of radiation and just stood there until they 'died' what would kill them?

 

[AntonL]

a different view looking back towards the view point of the video of explosion 3

 

[biggerten]

I hope this comes through OK, I've been lurking and this is my first post. Thanks to all who have been my unknowing teachers these last few days.

From http://www.tepco.co.jp/en/press/corp-com/release/11040103-e.html

This is the record of the earthquake intensity observed at the lowest
basement of the reactor buildings of Fukushima Daiichi Nuclear Power
Station and Fukushima Daini Nuclear Power Station when the
Tohoku-Taiheiyou-Oki Earthquake occurred approximately at 2:46pm on March
11th, 2011.

This report also contains Maximum Response Acceleration based on
"Regulatory Guide for Reviewing Seismic Design of Nuclear Power Reactor
Facilities (Revised in 2006)".
We will endeavor to keep collecting as much data as possible and examine
it in more detail.

The comparison between Basic Earthquake Ground Motion and the record of
the earthquake intensity observed at the lowest basement of the reactor
buildings of Fukushima Daiichi Nuclear Power Station and Fukushima Daini
Nuclear Power Station when the Tohoku-Taiheiyou-Oki Earthquake occurred.

【Reference】
Threshold for reactor scram at each unit(The reactor automatically stops
if the intensity of the quake exceeds the threshold.)

Glossary
· Observed Record of Earthquake Intensity
Record that indicates the intensity of an earthquake (Unit: gal)

· Regulatory Guide for Reviewing Seismic Design of Nuclear Power Reactor
Facilities
Revised in September 2006 based on the newly accumulated knowledge on
seismology and earthquake engineering and advanced technologies of
seismic design, this is a regulatory guide in reviewing the validity
of the seismic design of nuclear power reactor facilities.

· Basic Earthquake Ground Motion Ss
A basic earthquake ground motion in seismic design of facility,
stipulated in Regulatory Guide for Reviewing Seismic Design of Nuclear
Power Reactor Facilities

· Maximum Response Acceleration against Basic Earthquake Ground Motion Ss
Assuming Basic Earthquake Ground Motion Ss in the evaluation of the
earthquake-proof safety, this is the Maximum value of the quake of a
building, which is expressed in acceleration

 

[NUCENG]

Regarding the blue flashing light, http://en.wikipedia.org/wiki/Cherenkov_radiation" perhaps ? Is it possible to be created intermittently as claimed in the News Report ?

Rhody...

If the source, as speculated, local criticality it can easily be periodic. Assume the core melt has a small puddle of corium close to critical mass. Adding water to cool the reactor also saupplies a moderator to slow neutrons. As it cools and solidifies it can reach a critical geometry creating which is quickly interruped by boiling off the the water and remelting the corium until it becomes subcritical. Even approaching criticality may be sufficient to create high energy particles capable of visible radiation.

There is an are in Africa which has a very unusual distribution of Uranium isotopes, It is deficient in the portion of U235 found in ores in the rest of the world. It has been suggested that at some time in the distant pass the Earth created a natural reactor due to fluctiations in the water table it depleted the U235. The area is several hundred square miles.

The idea is to mix boron into the corium so it can't approach criticality. It is still necessary to cool it. Once cooled and solidified it may be possible to entomb it dry removing the moderator. That could take a long time.

 

[NUCENG]

Re: http://atomicinsights.com/2011/04/fukushima-nuclear-accident-exceptional-summary-by-murray-e-miles.html about the SFP at Unit 4:

The only shallow section between the spent fuel pool and the reactor is the cattle chute which has the gates people have been discussing. Fuel assemblies are only in the chute while the refueling machine is moving the to the pool or back to the reactor. If the chute fails there is still sufficient water level to keep fuel in the pool and the reactor covered.

 

[NUCENG]

REGARDING A BALLISTIC FUEL HANDLING MACHINE



If there were fuel handling operations in progress and the quake hit, then power failed and the reactor scrammed. It seems plausible that the operators would put the fuel assembly they were handling back in a safe position (if the fuel handling machine could draw power from the backup diesel generators, otherwise not), then get the heck out of there to see what was going on. Think about it -- working up there above the SPF and a big quake hits.

Also, I have absolutely no first hand experience, but from the pictures, the part of the fuel handling machine that handles the fuel assemblies is not a cable or anything like it. It looks like a rigid vertical arm, probably hydraulic, and I would be willing to bet it was built to be very precise, hold the fuel rod assemblies very securely, and put them in exactly the right spot.

If the blast resulted in the same initial trajectory and velocity of the FHM and attached fuel rod assembly, then, the point of impact would be about the same, I should think.

How about it Astronuc? What are the actual mechanics of a FHM and how does it attach to and secure a fuel rod assembly for movement?

Offsite power wasn't lost until the tsunami about an hour after the earthquake. The plant upset (SCRAM) would have halted any fuel moves in progress. It only takes a few minutes to put a fuel bundle back into the spent fuel pool.

The fuel handling machine has a mast with a gripping "grapple" at the lower end. The mast is telescoping for vertical movement. The FHM is mounted on a trasverse for east west and noth south movement between the spent fuel pool and the reactor cavity. It can be positioned directly over any pool or reactor fuel site.

Basically operator lower the mast, grapllet the rod, raise it up to be clear of the other fuel assemblis, moves it to its destination and the lowers it into place. Release the grapple and move to the next step.

Oh yeah, do it very carefully.

 

[NUCENG]

Me too, but there it is. Most of the force of the blast was going upward, pushing on the fuel handling machine. The fuel rods just got carried along for the ride, not blasted skyward. The spacer plates burst when the fuel rods hit the building.

Here's a question. I bet the new fuel rods are more brittle than the spent fuel rods. From what little metallurgy I know, the heating in a nuclear reactor, then cooling in a SFP, and then maybe heating them again in the explosion might make them less brittle. There do appear to be a few fragmented ones, but few if any appear bent.

The odd thing is that we, the lay public, will most likely never know the exact details, unless Astronuc gets busy, goes over there, and gives us the first hand scoop.

Someone tell me about superheated steam as an explosive propellant, please.

Would steam be more likely to cary a heavy piece of equipment skyward than, say, the heat from a hydrogen blast? I know live steam is a special kind of hot gas with a lot of energy density. The only way I can seem to get enough oomph directly under the FHM to launch it like that, mostly in one piece (if my PhotoShop'ed picture is correct) is, perhaps, for the initial hydrogen blast to take out the roof and then, have the superheated steam from the SFP to to launch the FHM skyward immediately following the hydrogen blast. If freeze frames from a shaky video from way far away are sufficiently informative, that may have been what happened.

Spent fuel is more brittle. That is why it remains channelled in the spent fuel pool. NRC has done a lot of studies of fuel rod embrittlement due to radiation and neutron flux.

The definition of explosion is a pressure wave expanding at sonic velocity. The first few frames of the explosion at unit one show a visible expanding semishpere shock wave.

A rapid release of steam creates a similar shock wave/Pressure pulse. Pressure is force. Newton takes over from there.

I don't want to be argumentative, but very good information is readily available about Chernobyl and TMI-2. Japan will need plenty of foreign support and I am pretty confident the information will come out. Heck, the US senate finished all their other mundane tasks and has started to hold hearings. (Sarcasm intended)

One final thought, if the fuel was directly above the blast so it lifted vertically, wouldn't it show heat damage due to the blast itself.

 

[NUCENG]

@Tcups: In addition, the fuel assembly that would in that scenario be attached to the FHM, would be protected from the blast as it was under water. The FHM would be send skyward with the assemply dragging behind it. Once the machine reaches the zenith of its parabolic track, the attached assembly, hanging off the boom, would swing in its path, centrigugal forces resulting from the FHM "tipping" holding everything in place. When the whole thing lands on top of the building again, the FHM lands first, slightly under an angle. The boom and assembly, still describing an arch, hit the building on their side, i.e. on one side of the channel. Compare taking a packet of spaghetti and swinging it on a piece of string, hitting your kitchen bench. The kinetic energy in the system spills the rods straight out, instead of smashing them. This also explains they are still close together.

If it was under water, then the fuel was covered. Where did the hydrogen come from?

 

[razzz]

A cabling system makes the most sense to aid in cleaning (cough) this site up, everything can be done remotely from overhead. Cranes and booms seem to susceptible to Earth's movements.

I read the stack to carry off and partially divert and/or scrub hydrogen and other gases with this design, in the event of an emergency, needs a power source to function properly when called upon.

Can't expect a company's complex to respond with much speed when a great tragedy strikes if they only have one satellite phone on site. Amazing if true esp. in a high tech country such as Japan.

Glad to see committees being assembled and assigned projects: examples might be; units 1, 2, 3, 4 plus pools because that is what it will take, some bright people to figure a way out of this one. Military think tanks come up with decent ideas but it's private industry that carries the load.

Even this board is making more sense on Unit 3 series of events, not that it matters right now.

You might want to take a break and read the responses to a post found elsewhere...
http://www.freerepublic.com/focus/f-news/2698156/posts"

 

[TCups]

Offsite power wasn't lost until the tsunami about an hour after the earthquake. The plant upset (SCRAM) would have halted any fuel moves in progress. It only takes a few minutes to put a fuel bundle back into the spent fuel pool.

The fuel handling machine has a mast with a gripping "grapple" at the lower end. The mast is telescoping for vertical movement. The FHM is mounted on a trasverse for east west and noth south movement between the spent fuel pool and the reactor cavity. It can be positioned directly over any pool or reactor fuel site.

Basically operator lower the mast, grapllet the rod, raise it up to be clear of the other fuel assemblis, moves it to its destination and the lowers it into place. Release the grapple and move to the next step.

Oh yeah, do it very carefully.

REGARDING THE SEQUENCE OF POWER LOSS

This is not consistent with what I have read and heard the last few weeks, which is:
1) Offsite power was lost at the time of the earthquake.
2) Emergency diesel generators worked properly for almost an hour, then these were disabled by the tsunami.
3) Battery back up power failed in a few hours time, and in less time that it was possible, under disaster conditions, before it was possible to truck in new generators and bring power back on line with them, although desperate attempts were made to do so.

Which scenario is correct? Would emergency diesel power have powered all the functions of the facility, including the fuel transfer machinery? Might the 9.0 quake have in some way disrupted the effort to return the fuel to the proper slot? Might the operators return the fuel rod to its proper slot then get the heck off the fuel handling machine as quick as possible, rush back to the control room, or to wherever their "disaster" station was, and in so doing, have left the mast grappled to the spent fuel rod assembly? This is not known.

REGARDING THE HANDLING OF FUEL, SPENT FUEL POOLS, AND TRANSFER CHUTES

There were two special flat bed trucks parked to the west of unit 3, one empty. I had heard but not confirmed that the implication was that older fuel rods from the SFP were to be loaded into casks for transfer to dry cask storage (or perhaps storage at the 7th SFP facility in wet storage?). I am not familiar with the technical aspect of those sorts of transfer.

As for the "cattle" transfer chute, I believe I understand its size, location and function. In fact, there appear to be two of these -- one at the interface of the reactors upper primary containment, above the level of the drywell cap, and a second between the main SFP and a smaller pool, which, I believe, is used for the cask transfer functions above (not certain of that). There were two potential problems related to the "cattle" chute, neither having anything to do with fuel being in the process of moving through the chute.

1) the seals on the gate(s) between the drywell containment, chute, and SFP are pneumatic and the pressure in the seals is maintained by electric pumps. If the seals are not properly pressurized, it is possible for water to leak from the SFP into the primary (drywell) containment above the level of the drywell cap, but below the "plug" that covers the reactor access, and
2) there are reports that the seals on the drywell cap itself may fail under as little as 2 ATM pressure from the primary drywell containment surrounding the reactor pressure vessel.

The other chute connects a second, smaller pool to the SFP. I have no information about a gate and seal on that chute, but doubt there would be as both these pools are open to air above and share a common water level. The connecting chute is only a few meters deep, however.

I am not an engineer and have no first-hand knowledge, but these issues and potential problems have been discussed here in the past weeks in some detail.

One implication, however, is that there is the potential, under a complete loss of power to have failure of the chute seals, and, possibly, abnormally high pressures within the drywell containment, thus creating a potential pathway for leakage of hydrogen or the explosive release of hot gasses from the primary drywell containment, through the drywell cap seals and through the chute gate seals, at least in theory.

Any solid information or additional relevant comments are appreciated. We are all just trying to understand what happened and why.

PS:
Rod Stewart had it right: "Every picture tells a story"
Let's hope it doesn't turn into a John Lee Hooker blues tune: "Boom, Boom, Boom, Boom"
good night.

 

[shogun338]

Japanese Radiation levels - measured on March 28th - actual footage from Greenpeace.

 

[Bodge]

Given the isotopes already found and their ratios, should we expect to be finding Sr-90 in the contaminated water/soil/air?

 

[shogun338]

Japan soldiers in shadow of Fukushima plant. Fresh water delivered to plant to cool reactors .

 

[NUCENG]

I would like to thank everyone for all the information they have posted here, it has been so exciting to learn so much about Nuclear power generation.

1) Astronuc - You are so freakin smart!

2) TCups - Nice forensic work, it was almost like reading a book. I must say though I was getting stressed out seeing all the work you have put into your posts, I could never do all that :)

3) From the information we have currently, is it safe to assume that everything could have been prevented if the plant never ran out of power?

4) If this happened in the states I would hope that we would be able to mobilize tractor-trailer sized generators & have them patched in within 8 hours?

5) Why would it take several days to run electrical connections from the grid back to the plant? Could you not just block off roads, fields etc. and just unspool a giant cable within a few hours?

6) Why do Nuclear plants have emergency hookups? Why not have 'ports' outside the reactor buildings for fire hoses to connect to that would shower the SFP with water? I understand that they need to have a closed system to prevent accidents, but if an accident does occur then they have no recourse it seems.

7) Again I saw some posts about not having the right generator types, 50 vs 60hz or not being able to splice into the system. Why would they not have an emergency hookup area for extra generators, batteries or external power lines? They could have all the transformers, cables, converters etc. to make connecting so much faster.

8) Could someone design a system where when power is lost that the reactor vessel is continually filled with liquid nitrogen? Please don't berate me for this question, I know nothing about interactions between chemicals, I just know that the reactor is very hot and liquid nitrogen is very cold.

9) Do Nuclear plants not have water towers or large storage areas for emergency fresh water, so they can run for a couple days without having to resort to sea water?

10) Finally I keep reading that x amount of radiation is lethal, but I have yet to read anywhere what happens if you get a lethal dose. Like what would happen if someone walked into a room with lethal amounts of radiation and just stood there until they 'died' what would kill them?

1) Astronuc - You are so freakin smart!

I agree. Great moderator.

2) TCups - Nice forensic work, it was almost like reading a book. I must say though I was getting stressed out seeing all the work you have put into your posts, I could never do all that :)

I may not agree with all his theoroes but he is doing his part to keep this thread interestinng and focused on finding truth.

3) From the information we have currently, is it safe to assume that everything could have been prevented if the plant never ran out of power?

If there hadn't been a loss of power, if there hadn't have been a tsunami, if there hadn't been an earthquake, the event could have been prevented. It will take a long time to figure out where or when the last barrier to this accident failed.

4) If this happened in the states I would hope that we would be able to mobilize tractor-trailer sized generators & have them patched in within 8 hours?

There are two things going for the US plants. First is the response to the Station Blackout Rule which provided a short (4 or 8 hours in most cases) coping period for a total loss of offsite and onsite AC sources. Second in response to the 9/11 incident plants have added systems for remote cooling of the spent fuel pool and the reactor vessel. Plants have prepositioned pumps and ssupport equipment to perform this task without outside power.

5), Why would it take several days to run electrical connections from the grid back to the plant? Could you not just block off roads, fields etc. and just unspool a giant cable within a few hours?

The reason high tension lines have insulators on the towers is to prevent a short to earth. Remember Japan had an earthquake and a tsunami that disrupted roads, airports, etc.

6) Why do Nuclear plants have emergency hookups? Why not have 'ports' outside the reactor buildings for fire hoses to connect to that would shower the SFP with water? I understand that they need to have a closed system to prevent accidents, but if an accident does occur then they have no recourse it seems.

They do have such systems.

7) Again I saw some posts about not having the right generator types, 50 vs 60hz or not being able to splice into the system. Why would they not have an emergency hookup area for extra generators, batteries or external power lines? They could have all the transformers, cables, converters etc. to make connecting so much faster.

Allegedly this comes from assistance to electrify Japan after WWII. US helper in the northeast and used 60 hz. The south and western part of the island used 50 hz.

You can't just connect 50 hz to 60 hz with a transformer. It would require all the 60 Hz generators to be offline deepening the energy crisis already there. And then the motors and equipment that got the power would not be designed for that frequency.

8) Could someone design a system where when power is lost that the reactor vessel is continually filled with liquid nitrogen? Please don't berate me for this question, I know nothing about interactions between chemicals, I just know that the reactor is very hot and liquid nitrogen is very cold.

New designs for PWRs and BWRs incorporate systems for makeup and cooling that can operate without electrical power for days instead of hours. They use gravity fed makeup systems and natural convection flows.

9) Do Nuclear plants not have water towers or large storage areas for emergency fresh water, so they can run for a couple days without having to resort to sea water?

Yes. Plants have condensate storage tanks sufficient to manage the early response in an design basis emergency. If that is empty US plants would use fire protection systems, wells, lake or river water to continue cooling much as the Japanese used seawater.

10) Finally I keep reading that x amount of radiation is lethal, but I have yet to read anywhere what happens if you get a lethal dose. Like what would happen if someone walked into a room with lethal amounts of radiation and just stood there until they 'died' what would kill them?

High radiation causes radiation burns . Inhaled radioactivity tend to cook you from the inside out. Even with a smarter decision to leave the area and seek drastic medical treatment won't help if the "body burden" is sufficient to kill internal organs. Radiation kills the blood producing marrow in bones. Resistance to infection is destroyed by blood changes from radiation. Latent cancers from doses well short of lethal doses and may take years to kill you. The nuclear industry preaches ALARA (as low as reasonably acheveable) for exposures to workers and the public. The problem is that there may be no minimum threshold for adverse impacts on health. NO AMOUNT OF RADIATION IS SAFE.

Scary huh? Just remember that many things have much higher risks, driving an automobile, smoking, flying. Life is a balance of risks and consequences.

 

[shogun338]

Given the isotopes already found and their ratios, should we expect to be finding Sr-90 in the contaminated water/soil/air?

Aside from sharing the dubious distinction of both nations having been at the receiving end of America 's nuclear weapons, Japan and the Marshall Islands now share a second dubious distinction. The unleashed isotopes of concern from the damaged Japanese reactors - Iodine-131, Cesium-137 , Strontium-90 and Plutonium-239 - are well known to the Marshall Islanders living downwind of the testing sites at Bikini and Enewetak atolls in the central Pacific, following sixty-seven A- and H-bombs exploded between 1946-58. In fact, it is precisely these isotopes that continue to haunt the 80,000 Marshallese fifty-three years after the last thermonuclear test in the megaton range shook their pristine coral atolls and contaminated their fragile marine ecosystems. • Strontium-90 has a half life of twenty-eight years, is a chemical analog of calcium and is known as a "bone seeker"; Rongelap and the other downwind atolls have residual Sr-90 in their soils, groundwater and marine ecosystems. http://www.countercurrents.org/alcalay270311.htm

 

[NUCENG]

REGARDING THE SEQUENCE OF POWER LOSS

This is not consistent with what I have read and heard the last few weeks, which is:
1) Offsite power was lost at the time of the earthquake.
2) Emergency diesel generators worked properly for almost an hour, then these were disabled by the tsunami.
3) Battery back up power failed in a few hours time, and in less time that it was possible, under disaster conditions, before it was possible to truck in new generators and bring power back on line with them, although desperate attempts were made to do so.

Which scenario is correct? Would emergency diesel power have powered all the functions of the facility, including the fuel transfer machinery? Might the 9.0 quake have in some way disrupted the effort to return the fuel to the proper slot? Might the operators return the fuel rod to its proper slot then get the heck off the fuel handling machine as quick as possible, rush back to the control room, or to wherever their "disaster" station was, and in so doing, have left the mast grappled to the spent fuel rod assembly? This is not known.

REGARDING THE HANDLING OF FUEL, SPENT FUEL POOLS, AND TRANSFER CHUTES

There were two special flat bed trucks parked to the west of unit 3, one empty. I had heard but not confirmed that the implication was that older fuel rods from the SFP were to be loaded into casks for transfer to dry cask storage (or perhaps storage at the 7th SFP facility in wet storage?). I am not familiar with the technical aspect of those sorts of transfer.

As for the "cattle" transfer chute, I believe I understand its size, location and function. In fact, there appear to be two of these -- one at the interface of the reactors upper primary containment, above the level of the drywell cap, and a second between the main SFP and a smaller pool, which, I believe, is used for the cask transfer functions above (not certain of that). There were two potential problems related to the "cattle" chute, neither having anything to do with fuel being in the process of moving through the chute.

1) the seals on the gate(s) between the drywell containment, chute, and SFP are pneumatic and the pressure in the seals is maintained by electric pumps. If the seals are not properly pressurized, it is possible for water to leak from the SFP into the primary (drywell) containment above the level of the drywell cap, but below the "plug" that covers the reactor access, and
2) there are reports that the seals on the drywell cap itself may fail under as little as 2 ATM pressure from the primary drywell containment surrounding the reactor pressure vessel.

The other chute connects a second, smaller pool to the SFP. I have no information about a gate and seal on that chute, but doubt there would be as both these pools are open to air above and share a common water level. The connecting chute is only a few meters deep, however.

I am not an engineer and have no first-hand knowledge, but these issues and potential problems have been discussed here in the past weeks in some detail.

One implication, however, is that there is the potential, under a complete loss of power to have failure of the chute seals, and, possibly, abnormally high pressures within the drywell containment, thus creating a potential pathway for leakage of hydrogen or the explosive release of hot gasses from the primary drywell containment, through the drywell cap seals and through the chute gate seals, at least in theory.

Any solid information or additional relevant comments are appreciated. We are all just trying to understand what happened and why.

PS:
Rod Stewart had it right: "Every picture tells a story"
Let's hope it doesn't turn into a John Lee Hooker blues tune: "Boom, Boom, Boom, Boom"
good night.

Your sequence is correct. My bad. I honestly don't remember if the FHM is powered by essential (Emergency Diesel ) power. If we have any experienced BWR operators on the forum, they would know. If it was, my discussion of the plant response is correct and they would have placed the bundle into the pool before evacuating the refuel floor.

If it wasn't powered from the diesels, the FHM is designed to fail as-is. It won't unlatch and drop the rod. The operators have manual backups for lowering or hoisting the load (ropes and pulleys), but it is possible they would leave it as-is in hopes of restoring power. In that case the FHM could have only been over the Spent Fuel Pool of the Cask pool, If it were over the cask pool wjth a cask installed there could have been a few relatively old (several years since discharge) bundles in the cask with low heatup rates. (In dry storage the air is sufficient to cool the fuel.) If water level was lost throughout the fuel and cask pools these bundles would still have whatever water was in the cask. Their heatup and initiation of Zirc water reaction would have been longer than freshly discharged fuel. This explosion would have been delayed and relatively smaller than a larger number of fuel rods in the fuel pool or reactor containing fresh fuel. Rule of thumb for heatup of a uncovered rod freh from the reactor is one degree per second.

One other item to consider, the refueling mast is designed to hoist a single fuel bundle. In cases where a control rod blade is stuck or a bundle needs to be unstuck from the support plate, they have to add additional lifting to get them free, It is not designed to accelerate that load to a velocity sufficient to reach several hunded meters in altitude. I've seen it up close. It just doesn't look possible.

There is a gate beteen the spent fuel pool and the cask pool. This allows the cask pool to be drained so the cask can be dryed and seal welded. There is always at least 6 feet of water or more over the top of a fuel bundle while it is being moved. That includes through the chute and in the cask. With the fuel pool at normal levels the bundles in the reactor, spent fuel pool, or cask are much deeper than that.

 

[jlduh]

Nuceng said:

Once again, you can design systems to be foolproof. It is unfortunately not possible to make them damnfoolproof

Yes, but damnfool can design foolproof systems. Which is sometimes even worse.

That's all the tragedy of this Fukushima plant, when we look at EDG layout, probably global platform height regarding to historical tsunami runups, and many other aspects.

Designing things is as difficult as operating them. And I've seen in my career as many mistakes in both sides. So I'm always kind of sceptic when "titanic like" assertions are done before hand saying "It's not possible", or "the probability is so low that there is no real risk". I think this should be an other lesson to reassess that kind of thinking.

Human brain is not that good to anticipate complex combinations of multiple factors (design factors and operational factors). It's good enough make it believe so, but not that good in fact. It is better meanwhile when there is a close loop between risk and consequence for him. In WW2, the accident rate for not properly opened parachutes was very high until somebody decided that the ones who is preparing the parachute will be the one who will jump from the plane. That's always the case now everywhere. This relates well with my point below.

Life is a balance of risks and consequences

Not untrue, but... that is what bankers were saying too. The problem is that very often, in both cases, the ones who take the risks are not the ones who get the main consequences. The balance is very often shifted this way (even if the average is "balanced").

Leaving for 2 weeks without any connection available, this will be my last "political" thought here for some time, I'll read you again in two weeks from now, and I'll be maybe 100 pages behind!

Let's hope this damn situation will not worsen.

 

[shogun338]

The operator of Japan's stricken nuclear plant said on Saturday it had found radioactive water leaking into the sea from a cracked concrete pit at its No.2 reactor in Fukushima.

Japan's nuclear watchdog said TEPCO is preparing to pour concrete into the pit to stop the leak.

 

[shogun338]

http://www.iaea.org/newscenter/news/tsunamiupdate01.html:

1.Current Situation

Overall at the Fukushima Daiichi plant, the situation remains very serious.

The Unit 1 condenser is full. In preparation for transferring water in the basement of the turbine building to the condenser, water in the condenser storage tank is being transferred to the suppression pool surge tank since 31 March, 03:00 UTC. Water in the trench was transferred to a water tank at the central environmental facility process main building. In order to prepare for removal of the water from the turbine building basement in Unit 2, pumping of water from the condenser to the suppression pool water surge tank started at 07:45 UTC 29 March. For Unit 3 pumping of water from the condenser to suppression pool water surge tank was started at 08:40 UTC March 28 and was completed at 23:37 UTC on 30 March.

For Unit 1 fresh water has been continuously injected into the Reactor Pressure Vessel (RPV) through the feed-water line at an indicated flow rate of 8 m3/h using a temporary electric pump with diesel backup. In Unit 2 fresh water is injected continuously through the fire extinguisher line at an indicated rate of 8 m3/h using a temporary electric pump with diesel backup. In Unit 3 fresh water is being injected continuously at about 7 m3/h into the reactor core through the fire extinguisher line using a temporary electric pump with diesel backup.

The indicated temperatures at the feed water nozzle of the RPV and bottom of RPV on Unit 1 are stable at 256 °C and 128 °C respectively. There is a slight decrease in RPV and Drywell pressures. The indicated temperature at the feed water nozzle of the RPV of Unit 2 is stable at 165 °C. The temperature at the bottom of the RPV was not reported. Indicated Drywell pressure remains at atmospheric pressure. The indicated temperature at the feed water nozzle of the RPV in Unit 3 is stable at 101 °C and at the bottom of RPV is also stable at 112 °C. Indicated Drywell pressure remains slightly above atmospheric pressure. The validity of the RPV temperature measurement at the feed water nozzle is still under investigation.

The pumping of water into the Unit 1 Spent Fuel Pool by concrete pumping truck was started at 04:03 UTC on 31 March. Fresh water was sprayed to the spent fuel pool at the Unit 3 by the concrete pump on 31 March and to the spent fuel pool on Unit 4 on the 1st April.

Units 5 and 6 remain in cold shutdown

2. Radiation Monitoring

On 31 March, deposition of iodine-131 was detected by the Japanese authorities in 8 prefectures, and deposition of cesium-137 in 10 prefectures. In these prefectures where deposition of iodine-131 was reported, on 31 March, the range was from 29 to 1350 becquerel per square metre. For caesium-137, the range was from 3.6 to 505 becquerel per square metre. In the Shinjyuku district of Tokyo, the daily deposition for iodine-131 was 50 becquerel per square metre and for cesium-137 it was 68 becquerel per square metre. No significant changes were reported in the 45 prefectures in gamma dose rates compared to yesterday. As of 28 March, recommendations for restrictions on drinking water are in place at two locations in the Fukushima prefecture and restrictions continue to apply for infants only. The IAEA monitoring team made additional measurements at 9 locations West of Fukushima-Daiichi NPP. The measurement locations were at distances of 30 to 58 km from the Fukushima nuclear power plant. The dose rates ranged from 0.4 to 2.3 microsievert per hour. At the same locations, results of beta-gamma contamination measurements ranged from 0.01 to 0.49 Megabecquerel per square metre. The other team who had made monitoring measurements in Tokyo during the last week, has finished its activities.

Since our written briefing of yesterday, significant data related to food contamination was reported on 31 March by the Japanese Ministry of Health, Labour and Welfare. Reported analytical results covered 2 samples taken on 15 March and 109 samples from 27-31 March. Analytical results for 98 of the 111 samples for various vegetables, spinach and other leafy vegetables, fruit (strawberry), seafood, various meats (beef, chicken and pork) and unprocessed raw milk in eight prefectures (Chiba, Fukushima, Gunma, Ibaraki, Kanagawa, Niigata, Tochigi, and Tokyo), indicated that iodine-131, caesium-134 and caesium-137 were either not detected or were below the regulation values set by the Japanese authorities. However, it was reported that analytical results in Chiba, Fukushima, Ibaraki and Tochigi prefectures for the remaining 13 of the total 111 samples for spinach and other leafy vegetables, parsley and beef indicated that iodine-131 and/or caesium-134 and caesium-137 exceeded the regulation values set by the Japanese authorities.

The following restrictions are in place (Ministry of Health, Labour and Welfare Press Releases 21 and 23 March 2011):

Fukushima: Distribution and consumption of leafy vegetables (including broccoli, cabbage, cauliflower, kakina, komatsuna and spinach), turnip and unprocessed raw milk. Ibaraki: Distribution of spinach, kakina, parsley and unprocessed raw milk.
Gunma: Distribution of spinach and kakina.
Tochigi: Distribution of spinach and kakina.

The Joint FAO/IAEA Food Safety Assessment Team has completed its mission and presented its report to the Japanese Cabinet Office, Ministry of Foreign Affairs, Ministry of Health, Labour and Welfare and the Ministry of Agriculture, Fisheries and Forestry on 31 March. The IAEA members of the Team are returning to Vienna today.

The Agency, in agreement with the Japanese government, will dispatch two reactor experts to Japan. They will hold meetings with the Nuclear Safety Commission, NISA, TEPCO and other Japanese counterparts from Monday 4 April onwards. The objective of this visit is to exchange views with Japanese technical experts and to get first-hand information about the current status of reactors at Fukushima Daiichi, measures being taken and future plans to mitigate the accident.