Fukushima No. 1 loss of coolant due to earthquake 7

[cloa]

No risk of nuclear explosion as the carbon control rods are all inserted to mop up neutrons- any way its leaking some radiation to the containment area so the radiation is not concentrated in the reactor to increase the nuclear explosion risk.

 

[unclesyd]

Everyone is waiting for the official word but you may only get older waiting for the truth.
First part is what is know as the TEPCO scandals in Japan.

Time line on the Fukushima Nuclear Plant.

http://www.nirs.org/reactorwatch/accidents/nit92.pdf

http://www.nirs.org/reactorwatch/accidents/Fukushimafactsheet.pdf

I understand that these reactors are Light Water Reactors which are not the same as the BWR reactors in the US.

 

[trottiey]

There is no risk of anything remotely resembling an atomic bomb. If the core does melt, it will spread out to a flat puddle over the "core catcher" in the primary containment. Geometry matters to criticality, and a "critical mass" is just the minimum amount of material you would need if it was shaped like a perfect sphere. Anything other than a sphere loses a greater percentage of neutrons before they have a chance to participate in a chain reaction.

I will not give you an outright "no" to a fission explosion because there is room to get tripped up in definitions. Spontaneous fission is still occurring, and that is what is producing all that heat and pressure and hydrogen. So fission is indirectly responsible for those hydrogen explosions, and might also cause a pressure explosion. But there is no risk of a meltdown causing criticality and restarting a chain reaction, which is what a true nuclear explosion would be.

As to Cloa's comment, the control rods at Fukushima Dai-ichi unit #1 are boron carbide and hafnium. I believe they would float on top of the uranium in the event of a meltdown, so they would not be effective. Past accidents, such as at Chernobyl, have taught us that pure carbon is an undesirable material in a reactor.

 

[electricpete]

Update from the good site

http://www.world-nuclear-news.org/RS_Possible_damage_at_Fukushima_Daiichi_2_1503111.html

The good news: It seems the fire was at unit 4, and is out, not a concern.

The bad news: There remains big concern for the failure of the unit 2 torus:

The pressure in the pool was seen to decrease from three atmospheres to one atmosphere after the noise [unit 2], suggesting possible damage. Radiation levels on the edge of the plant compound briefly spiked at 8217 microsieverts per hour but later fell to about a third that.

=====================================
(2B)+(2B)' ?

 

[electricpete]

By the way, that conversion again, 8217 microsieverts/hr is 822 millirem/hr

=====================================
(2B)+(2B)' ?

 

[guizmy]

Someone could tell us please the amount of radiations emissions to environment in Fukushima in comparison to Tchernobyl Reactor with regard to the total quantity of Nuclear Fuel available in Fukushima's failing Reactors and their capacity versus Tchernobyl?

Would it be something like 3 times Tchernobyl in the case of the worst scenario possible?

 

[cloa]

Radiation is not easy to compare nor is nuclear fuel- why do you need a comparision- its not the same. Tchernobyl or chernobyl was a nuclear chain reaction explosion.

 

[ScottI2R]

Ok, further removal of doubt. First, Pete, I get 821.7 mRem. Trottiey, bar definitions, that was the explosion I was inquiring about. I realize they could still explode as a gigantic "dirty bomb" scenario, but like I said, I was referring to an actual A-bomb type detonation. I had no idea of how critical geometry was from a criticality standpoint. Let me say, I was aware of it, but I thought it was just for efficiency purposes, ie. the most bang for your buck. Thank you for edumacating me.

Now, my question is about the radiation levels at the plant. These 50 or so workers are being exposed to what I believe is a lethal dosage of radiation. Is the PPE they have sufficient to protect them from harm or are they already walking(working)dead? If so, what would be the maximum levels that they could safely work in with the proper PPE? A personal example is my arc flash protection I wear, it is rated for an 8 calorie blast, so I stay out of panels where there is potential for greater than that. Believe me, I have no desire to be in an 8 Cal blast either, but that is where my protection stops. We are not issued the 40 calorie "space suits" at my plant.
One more question if I may. What kind of radiation is this? Alpha, beta, gamma and how fast does it travel a given distance (when not propelled by an explosion)? I believe that if it were xray or gamma, it would travel at speed of light. Please correct me on all of this as you see fit.

Once again, thanks to all of you for your responses.

Scott

I really am a good egg, I'm just a little scrambled!

 

[guizmy]

quoted wiki on Tchernobyl:

"Four hundred times more radioactive material was released than had been by the atomic bombing of Hiroshima. However, compared to the total amount released by nuclear weapons testing during the 1950s and 1960s, the Chernobyl disaster released 100 to 1000 times less radioactivity. The fallout was detected over all of Europe except for the Iberian Peninsula.

The initial evidence that a major release of radioactive material was affecting other countries came not from Soviet sources, but from Sweden, where on the morning of 28 April workers at the Forsmark Nuclear Power Plant (approximately 1,100 km (680 mi) from the Chernobyl site) were found to have radioactive particles on their clothes"
unquoted

So yes definitely I want to roughly compare to figure out the environmental and Health potential consequence of Fukushima.

By Nuclear Fuel I mean combustible or Nuclear Materials. Sorry for my english I am not native english speaker.

 

[unclesyd]

The biggest problem with Chernobyl was it had an open core and bits of the core were all over the place. The last word that i got is that all who initially worked on the roof and helicopter pilots are all dead. The helicopter pilots were the first to go as they had to fly over the exposed core o drop Boron pellets. Hundreds of solders used to tunnel under the reactor suffered varying degrees of radiation poisoning.

As I understand, it is now possible to treat some exposures that were at one time considered lethal.

 

[Power2go]

First, thank you all for the information you have shared so far. It has helped in understanding what is going on at the Fukushima NPP.

Here are links to digital globe that has excellent images from after the latest explosion at reactor 3. The damage to this building seems more extensive then to the building of reactor 1 after the explosion there.

http://www.digitalglobe.com/index.php/27/Sample+Imagery+Gallery

http://www.digitalglobe.com/downloa...uaketsu_fukushima_daiichi_march14_2011_dg.jpg

The 50 or so operators/engineers/staff (from the 800 normal) that remain in the plant have an impossible task. With the levels of radiation present they should be out of the place within 30min but 2 hours max. When they don't they will get radiation sickness and die. They can hardly cope with all the new incidents like the fire in the building of reactor 4. (which was already shut down over a longer period). When the operators are forced to leave the plant will be on its own and.......

Think of this: when you go for nuclear energy you should be able to maintain a high level of security, technical know how and safe storage of spent nuclear fuel for at least the next 10.000 year. Now take the 10.000 year and flip that back to the past and imagine where you are. (You will end up way before the Egyptian dynasties)

 

[unclesyd]

FYI:
These reactor are General Electric Mark I reactors. There are 23 of these in the US.

 

[trottiey]

For ScottI2R regarding radiation protection:

Please don't be shy; it wasn't a stupid question. You can look further up through this thread to see a stupid answer on my part, and that's much worse.

Radiation is probably the most complex hazard that humans work with, so it's very hard to give simple answers. To start with, there are two broad types of radiation exposure: internal, for example breathing in radioactive dust, or external, like getting a sunburn from solar irradiation. The suits they wear provide protection against internal contamination but do little against external irradiation. The suits themselves are useful against almost any level of contamination, but their effectiveness depends primarily on the work practices of the user. For example, forgetting to shave can make your respirator ineffective. Carelessness while changing out of them can send surface contaminants airborne where you can breathe them. Your level of radiation protection training is the number one thing that determines what level of radiation you can work with safely, not the quality of the suit.

It's hard to tell how much dose the workers have received. There have been a variety of numbers and statements published by the press that are completely inconsistent and can only be explained as journalistic errors. As best as I could gather as of March 14th, somewhere between zero and four workers may have received a lethal dose. One of those was physically trapped and may have died from conventional causes long before the radiation got him. The other three, if the reports are accurate, are being treated. I have not seen nearly enough information for further medical prognosis, either positive or negative.

I suspect that most of the workers on site are receiving doses well in excess of occupational limits but far below lethal levels. Any amount of radiation will increase your lifetime risk of cancer proportional to the does you take. The highest dose number I have seen so far was 106,000 microsieverts, which carries with it a 0.6% chance of cancer and other health effects. But there may be other numbers I haven't seen, and the situation is still deteriorating. Please check the FAQ section later, and I will try to address this.

Alpha, beta and gamma radiation are all present in this accident. All of them travel at the speed of light, but they get weaker with distance. (Alpha and beta are actually slightly slower, but not by much.) The particles, droplets and gases that emit this radiation travel at whatever speed the wind or water currents will take them. You can probably see that this is a really complicated problem.

 

[trottiey]

Regarding the quantity of radioactive material that might be released:

With the recent escalation of events, do we need to consider the risk to the spent fuel bays? According to the diagram, spent fuel is stored within the reactor building secondary containment; is this correct? This is the part of the building that blew up on units 1 and 3, leaving those bays exposed to the atmosphere. Spent nuclear fuel needs to be kept underwater and cooled for a few years after removing from the reactor. If those pools drain or evaporate off their water, the zirconium cladding on the spent fuel can catch fire. Is this what happened in unit 4? How much fuel would be in those bays?

 

[Power2go]

As far as I understand from various news sources the spent fuel is kept in the secondary buildings, under water in large basins. At present there is a storage of 20 years (!) of spent fuel rods in the Fukushima NPP. The spent fuel basin in the number 4 building dried up and the fire started.

So much for safe storage of spent fuel rods.

 

[itsmoked]

What is the torus for? I can't puzzle that item out.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[unclesyd]

Here is short description of the Torus.

http://www.nirs.org/factsheets/bwrfact.htm

 

[jmw]

I seem to be missing something here.
According to the media, the earthquake alarm tripped these reactors into shutdown mode, or some of them and one was down for maintenance.
The problem, we are told, is that the Tsunami damaged the diesel generators and the batteries were unable to cope.
Is there something more? It seems to me that even if the generators were wiped out, portable generators could be brought in within the time frame here and since this is a coastal station which receives much of its supplies and equipment by sea, the suggestion has been that ships docking there could provide power though it might take some doing to jury rig a connection.
So I have to think that the generator failure is not the primary problem.
So OK, the control rooms are damaged, but the first objective is tor restore water circulation... so it is a matter of powering some pumps and valves.
At the moment they are said to be flooding the reactors with sea water... they've power for that but are they flooding the reactors or simply pouring water over the containment? (which suggests the cooling water installation has suffered something else?)
Need to replace pumps? Airlift in.
So something in the media doesn't gell. It may well be my understanding.
So what am I missing?

JMW

http://www.ViscoAnalyser.com

 

[davefitz]

jmw:

We will likely need to wait for the "root cause analysis report" that would be issued maybe a year from now to have something more reliable than guesses. And the publically available version will likely be edited in some manner, but that is the price we pay everyday, for "consensus'.

Some reports claim the diesels were taken out by water contamination of the fuel- which would also likely damage the fuel injectors. Other possiblities include water entering the snorkel air intake.

The pumps and motors may use seal water, normally assumed to be filtered clean fresh water, and that assumption may have been violated and now whaterver the seal water or cooling water had contaced is likely fouled/ damaged by salt water / debris contamination.seized bearing etc follows quickly.

But one thing we can be certain- everyone involved is working at max dedication to solve this ASAP, and it is best to give them whatever support they need to succeed.

 

[unclesyd]

Here is a synopsis of the Fukushima problems. It has a lot of good links.

http://www.ieer.org/comments/Daiichi-Fukushima-reactors_IEERstatement.pdf