There was another explosion:

http://www.guardian.co.uk/world/2011/mar/14/japan-nuclear-explosion-second-reactor-fukushima

3/14/2011 12:24:34 AM

Japan is covering up the severity of the crisis to avoid discouraging aid workers. American military in the region have already been exposed to excessive radiation levels.

Nuclear Power is Dead.

3/14/2011 12:31:28 AM

What's GE's culpability? Didn't Obama recently appoint a former GE exec to head up business policies?

And why shouldn't this be a push to use safer designs and upgrade existing plants, rather than just not build plants?

Something has to create energy for all these new electric vehicles about to hit the market.

I would think in this day and age, it shouldn't be so hard to have a bunch of industrial generators air-lifted in to get the pumps back online...? I guess we'll have to wait a bit to know the full story.

3/14/2011 12:42:17 AM

Quote :

"Japan is covering up the severity of the crisis to avoid discouraging aid workers. American military in the region have already been exposed to excessive radiation levels. Nuclear Power is Dead."

"Excessive radiation levels" as you describe them are, more specifically, "one month's worth of exposure in an hour" as officially described is not as much as you seem to think it is. Assuming the high end possibility (one year's worth being maximum allowable for military personnel) of this meaning this ends up being 4 mSv. This is 1/5th what you can get from a CT scan. Note also I'm using the highest of several categories of exposure limits when I say this. If they are using the more commonly used limit for US military personel (those who are not specifically classified as radiation workers) then the meaning of one month's worth of exposure ends up being about 1/15th of the radiation exposure from a CT scan.

Now the situation at those power plants is not a good one, don't get me wrong. The medium term economic damage is likely to be significant. If they lose integrity of one of the pressure vessels then the risk to the health of the plant workers will be significant and the habibility of the immediate area around the plants would be in question - this would also have serious long term negative effects on the regional economy particularly with agriculture.

It is still important to be honest in this debate and not obfuscate the actual risks posed. Due to the extensive evacuations it is unlikely anyone will experience long or short term health risks due to this accident. If their attempts to control the stricken reactors goes poorly, then the only people likely to be at statistically significant risk are those working now at the plant working to keep the worst from happening. There are good arguments that can be made against nuclear power - but one does not need to resort to scare tactics that prey on the general lack of understanding people have about radiation risks.

To give you a sense of scale with which to compare these numbers, the average anual background dose across the world is roughly 2.4 mSv. Looking only at that number, then this exposure might still seem non-trivial. The actual natural background radiation that populations may be exposed in various population centers ranges quite a bit higher than the average though. Case studies have been performed across the world to determine the risks posed by "very high background radiation" and it was discovered, surprisingly, that there is no correlation between very high background radiation and cancer incidence. This is particularly surprising because many of the areas studied had yearly background doses of 100 mSv. One city even had a yearly background dose of 230 mSv - again with no correlation to negative health effects. This "excessive radiation" as you call it is on the same scale of intensity as the background radiation in some of those cities - and the military personel in question were only exposed relatively briefly.

Here's one of the dozen or so studies done on the most notable of those locations, Ramsar
http://www.probeinternational.org/Ramsar.pdf

NOTE: Yes, multiple CT scans in a year would cause someone to receive more radiation in a few total hours at the hospital than is normally allowed even for those classified as radiation workers. If the CT scan is not properly reset after testing and callibration (as a recent study showed happens far too often) then the numbers you could get from a CT scan could be far higher.

[Edited on March 14, 2011 at 12:57 AM. Reason : jubblies]

3/14/2011 12:46:55 AM

Cancer will be widespread for years to come.

Ironic that Japan of all countries would suffer a meltdown.

3/14/2011 1:05:44 AM

Quote :

"Cancer will be widespread for years to come. Ironic that Japan of all countries would suffer a meltdown."

If the measurements being reported are accurate - then making that assumption at this point is either a consequence of ignorance or willful dishonesty. The radiation levels that a small number of people have so far been exposed to are far less than one gets from a CT scan. The current radiation levels at the plant itself are near or below those found in many population centers around the world. While they are several times the global average natural background radiation, local background levels in many towns and cities can be close to and sometimes higher than this.

Case studies have been done in these locations, such as the one done in Ramsar that I linked to, that show that this level of radiation does not generally correlate to any increase in cancer incidence. The idea that "any amount of radiation exposure no matter how small is harmful" might be helpful for the purposes of designing safety policy, but it is not backed up by studies of low dose radiation exposure. The truism itself is based on the linear no-threshold model of cancer risk as a function of radiation exposure - which has been consistently demonstrated to be inappropriate for exposure rates of the magnitude we are talking about.

Sadly, the popular perception of radiation exposure and judgment of the risks involved is based on this now discredited risk model. Unlike LNT, hormesis is backed up by the results of these case studies. Even the most counterintuitive part of radiation hormesis model of risk, that the safest level of radiation exposure is in-fact not 0 but higher than average background, is supported by many of the case study results. Yes as strange as it sounds, the safest level of radiation to be exposed to is most likely more than you are currently being exposed to. At the what is general described as "very high background radiation" there is no change from the average in terms of cancer incidence - there is however a statistically signifcant increase in cancer survival rates.

Limited and long term exposure to high intensity radiation sources is, of course harmful. This is not disputed by either the LNT model nor by hormesis. Habitual inhalation and ingestion of radioactive materials is also generally not advised - as the effective dose from these materials is much higher than if they are outside your body. This is why the evacuations are quite sensible and also why the economic damage this incident will have will be so severe - agriculture in the area will not return immediately even if the incident were to be resolved quickly and safely. It is probably prudent that they first investigate and demonstrate that any food produced or harvested in the area will be safe before they resume those activities. That may take longer to happen than it will take for the area near the plant to become safe again for residents.

Water table contamination will also have to be considered. At present, this accident has not likely introduced significant contamination to the water supply in the immediate area. Still, due to the risks of radioactive iodine, it should be presumed unsafe until tested. If the situation at the plants deteriorates and we do see major releases - water table contamination will be the largest barrier to the habitability and economic viability of the area. Still - those are concerns related to returning to the area. They are not immediate risks as nearly all the residents in the surrounding communities have already been evacuated.

3/14/2011 1:57:13 AM

http://bravenewclimate.com/2011/03/13/fukushima-simple-explanation/

3/14/2011 2:24:26 AM

Quote :

" Professor Barry Brook, an environmental scientist at the University of Adelaide, said the effect on the Australian debate depended on whether it would be ”argued on a rational basis or an irrational basis”. A rational debate would acknowledge that Japan’s largest recorded earthquake produced an incident at a 40-year-old reactor that was ranked at a level less than the Three Mile Island emergency, he said. ”I think the nuclear reactors have come through remarkably well.”"

From the author of the above article. Spot on.

3/14/2011 2:50:46 AM

outside of the plant isn't the concern just alpha and beta radiation which can be somewhat mitigated through the use of PPE?

3/14/2011 8:45:22 AM

^ I think the concern outside the plant is the ingestion or inhalation of alpha and beta source material - realease of which have not been very significant yet, however those working at the plant are still wearing breathing equipment so they do not breath i particles. The effective dose from ingested and inhaled radioactive particles can be orders of magnitude greater than the external dose one would receive otherwise.

That's also part of the reason for the evacuation. They do expect to prevent large releases, but they would rather not have anyone breath in particulates from these relatively small releases.

3/14/2011 9:11:49 AM

Third reactor now melting down.

3/14/2011 10:59:37 AM

^^ The concern is the entering of radioactive particles into your system. Iodine is notorious for being easily absorbed, but can be significantly mitigated by consuming Iodine tablets, which they've distributed.

^ Wow, you seem to not have a problem stating something as fact that is completely unsubstantiated.

3/14/2011 11:04:54 AM

He's just trolling. When someone makes a comment like this:

Quote :

"Cancer will be widespread for years to come."

based on the 'current' information, they either are trolling or dont know much about radiation.

Now, I'm not going to say something couldnt happen out of this situation to send very large amounts of radiation into the air that could cause lots of nasty stuff, but thats not the situation now.

3/14/2011 11:20:20 AM

wouldn't any melting or degrading of the zirconium be considered a meltdown? which would mean it is a meltdown?

3/14/2011 11:24:00 AM

the term meltdown doesn't necessarily mean uncontrollable or catastrophic

3/14/2011 11:36:19 AM

Quote :

"wouldn't any melting or degrading of the zirconium be considered a meltdown? which would mean it is a meltdown?"

No, it wouldn't. If I used your definition, I could easily get to claiming that operating reactors are melting down all the time.

The safety analysis is concerned with "fuel failure". Fuel fails all the time, although only a small fraction that isn't really concerning. Rupture of the Zr clad releases 5-10% of the fission products at most, and these are the ONLY thing that are relevant to public safety. The "defense in depth" exists in the fuel itself in the form of the fuel pellets and the cladding. Fuel is burned and the products of that burning is contained in the ceramic pellets. The physics and suitability of the ceramic pellets have been studied in great depth, and some reactor designs don't even have cladding, just pellets wrapped together.

I hope this helps you understand why the cladding failing doesn't make it a nuclear disaster. A normal core has some 10s of thousands of rods, and in the life of that core, some 100s of them will likely fail, although the industry is trying to become "zero failure", the initiative doesn't make any sense because they're improving the fuel while at the same time pushing it further. A better designed car that is driven further still breaks down, duh.

In the nuclear analysis, it's not just meltdown that is being prevented, we also would like to prevent failure of any part of the core. If the top portions are uncovered, then some fraction of the rods are likely to fail, and certain regions are typically the problem areas. The Fukushima II-1 has had the top uncovered to 170 cm according to some Japanese press sources. This makes 40% of the core uncovered, in Three Mile Island, 75% of the core was uncovered and most of it melted down. Before you draw conclusions you need to know the differences. Fukushima uses BWRs which have a lower power density, and the uncovering occurred a day or more after the plant was shut down, TMI melted down 2.5 hours after it was shut down, and that makes all the difference in the world. The heat production in the core decreases as time after shutdown increases, and ranges from 7% to 1% and less. The core is already designed to handle steam and be cooled by steam (as opposed to water).

However, the experts don't agree what the presence of Hydrogen (which is irrefutable) implies for the state of the core. Some seem to think that rod burst will have happened in large number before the Hydrogen was produced. Perhaps. The number of broken rods basically is what's of concern and is the driving number behind the radioactivity source term - I mean the amount of radioactivity released from the core.

The word "meltdown" should apply to the pellets and not the rods. There is no reason to believe that pellets have been melting, and they probably have not. Again, we go from 5-10% to 100% of the gases released if the pellets melt. Additionally, the time from shutdown makes a big difference. These are the reasons that Fukushima will probably not be as bad as TMI, and of course Chernobyl. That said, each of those was only 1 reactor while Fukushima is dealing with cooling issues for multiple reactors due to a common cause (a giant tidal wave). There are still engineered barriers standing in between 99.99% of the bad gases contained in the core and the public.

Seriously people, pray that 99.99% is manageable and stop your sensationalism about the amount that's already leaked. We know the dose levels spiked, but there's a big difference between spiking 100x and 100,000,000x

[Edited on March 14, 2011 at 11:41 AM. Reason : d]

3/14/2011 11:40:27 AM

I remember reactor 3 was MOX fuel, but how about reactor 2? I'm asking because I'm also curious if anyone has an idea of how serious the fast neutron fission cross-section of the plutonium would be to the prospect of a meltdown being harder to control. While I know there is still a negative void coefficient as long as proper core geometry is maintained - how significant is the pressence of plutonium in terms the potential for relocation causing recriticallity?

Quote :

"e concern is the entering of radioactive particles into your system. Iodine is notorious for being easily absorbed, but can be significantly mitigated by consuming Iodine tablets, which they've distributed."

They've also taken a far more effective precaution against that too - evacuation. Sorry I just felt like reitterating how proactive the evacuation has been. I think the total people they have said were even exposed (besides the navy personel) was 160 or so. Personally I would take "being somewhere else" as my method of mitigation, but failing that iodine is better than nothing.

Something that I should say for clarification though. I'm more familiar with PWRs and LFTR designs than BWRs - so I may have been a little imprecise in my use of terminology. I should emphasise that the containment structure we have seen damaged in both cases is the secondary containment structure. This building is not intended to be a high-strength pressure containment system like the containment dome on a PWR is. It primarily serves as a means of capturing gasses vented from the pressure vessel - which are first blown throw into pools of water. Thiese water pools (wetwell) serve partially to cool gasses vented from the reactor (otherwise venting would immediately put the containment building at risk) as well as to help capture and filter the vented gasses. The air inside the building is normally kept below atmospheric pressure - so that even if it leaks it leaks in. To maintain negative pressure without also compromising the containment effect it offers, the same systems that normally maintain the lower pressure have sophisticated filters which help to scrub and purify the air.

The loss of the roof means the loss of all but one means of even partly fitering vented steam - the wetwell. If the wetwell remains filled, it will help to mitigate the release of radioactive materials to a point. This would explain why there is an elevated concentration of caesium and iodine around the site - but a relatively small one. Of course this "filtering" effect is minimal compared to what now powerless equipment in the secondary containment building would normally do.

The drywell however is a very thick concrete structure that could survive quite a bit of abuse. Even if there is a meltdown, in the absence of some source of violent sudden pressure it should still serve to contain the majority of the core materials - though I'm not sure what kind of concrete is used so I can't say how it behaves under teperature. I do know that some reactor designs (far newer ones) opt for basalt due to its high melting point and ability to contain a molten core - which might suggest the concrete in these older plants is not as suited to that.

[Edited on March 14, 2011 at 12:00 PM. Reason : ]

3/14/2011 11:42:55 AM

how long can the fuel go dry before melting? at least one of the reactors was dry for a period of time.

3/14/2011 11:50:28 AM

Quote :

"I should emphasise that the containment structure we have seen damaged in both cases is the secondary containment structure"

Your terminology is particularly unhelpful, but we should be able to agree on the function of the building, even though we won't agree what to call it. I call it the reactor building.

It's a weather building.

Quote :

"The loss of the roof means the loss of all but one means of even partly fitering vented steam - the wetwell"

I believe this is incorrect to some extent. The reactor building was not pressurized, but I'm speaking outside my knowledge to say whether or not it has ventilation and filtration systems. The containment is contained well within the reactor building and surrounded by pools of water. Typically, the containment (in this case, the drywell) is the only thing that's relevant to nuclear safety, although with this design they had to open up containment in order to do refueling, leaving the reactor building as the only barrier left in that case, which makes me want to believe your statements about the significance of the reactor building. That said, I do not believe the reactor building had any capability to hold pressure, although it may be accurately called air tight, which is necessary in order to take credit for an air filtration system preventing release of radioactive gases.

I may be speaking out of my knowledge again, but I think that pressure is equalized between the wetwell and drywell, and yes, the wetwell provides some natural filtration by running the vented gases from the drywell through the water there. But I think that's an unimportant point. In order to release gases from the collective volume of the wetwell and drywell (basically the containment), they have to send it through the nuclear-rated filtration system. In every case for Fukushima this has still been working - and is the stark difference to Three Mile Island.

Quote :

"how long can the fuel go dry before melting? at least one of the reactors was dry for a period of time."

Not dry. Steam.

But correct, Fukushima II-1 had apparently boiled off a significant part of the water and stayed there for some time. It was still being cooled by steam, but this is semantics, in order to talk further we would need to actually apply a real physical knowledge of the system. The fuel produces heat, and the steam is not much hotter than the water, but it removes the heat more poorly than water. The flow rate of the steam and the heat production rate are the critical measures to determine if clad failure temperature is reached or not. The time it was uncovered is also important because if this is temporary, the thermal mass of the fuel itself can protect it, but given an hour or more it's likely to hit steady state anyway, then you may want to consider the failure probability and oxidation rate of the cladding in the environment through that time period.

Any questions?

[Edited on March 14, 2011 at 1:34 PM. Reason : ]

3/14/2011 1:32:29 PM

Quote :

"that show that this level of radiation does not generally correlate to any increase in cancer incidence"

Does this take into consideration at all that cancer is not the lone risk from radiation exposure. Only 9 out of like 200 types of cancer are caused by radiation.

3/14/2011 1:56:42 PM

I just want to thank the nuclear engineers that have spoken in this thread. Gives me somewhat of a handle on the situation without having to filter through the sensationist articles thrown out by the MSM.

3/14/2011 1:56:43 PM

Quote :

" I believe this is incorrect to some extent. The reactor building was not pressurized, but I'm speaking outside my knowledge to say whether or not it has ventilation and filtration systems. The containment is contained well within the reactor building and surrounded by pools of water. Typically, the containment (in this case, the drywell) is the only thing that's relevant to nuclear safety, although with this design they had to open up containment in order to do refueling, leaving the reactor building as the only barrier left in that case, which makes me want to believe your statements about the significance of the reactor building. That said, I do not believe the reactor building had any capability to hold pressure, although it may be accurately called air tight, which is necessary in order to take credit for an air filtration system preventing release of radioactive gases."

The secondary containment is kept at slightly atmospheric pressure - at least according to my old NE text books. It may not be something they take credit for during accident condiitions and only have to claim during refueling - but it seems that it is generally kept that way as an added safeguard anyways. I do admit I had been thinking of a PWR when I was thinking of suppression pools rather than the taurus. So yes primary containment is the dry-well and venting is done into the the dry well and from that piped into the taurus. While it seems that there should not be any venting to secondary containment that does not pass through sophisticated filtration systems, the fact that hydrogen produced in the reactor built up in the reactor building causing it to blow and that this was followed by the detection of elevated levels of isotopes of iodine and cesium suggests that this is not the case. I think that is part of the reason that secondary containment is kept at at sub-atmospheric pressure - because this is expected to some extent.

NHK had reported that the filtration systems were not working - at least for some time - due to complete loss of power. That might explain in part the discrete releases of caesium and iodine detected after the blasts. If they are or were back online that would also help to explain why levels had been stable for a significant span of time - despite venting from the pressure vessel multiple times.

Quote :

"Does this take into consideration at all that cancer is not the lone risk from radiation exposure. Only 9 out of like 200 types of cancer are caused by radiation."

The studies I've actually read focused on cancers that have been shown to have increased incidence with radiation exposure - such as leukemia and lung cancer (controlled for other factors such as smoking and air quality). Though these cancers have been shown to have increased incidence among populations that have had discrete high dose exposures to radiation, there had not been extensive data collected on their potential relationship to chronic low dose exposure. That is what these studies seeked to establish - and what they found was that they could not find a correlation between chronic low dose exposure many times the average background exposure. The rates were unaffected.

[Edited on March 14, 2011 at 3:11 PM. Reason : ''l]

3/14/2011 3:04:31 PM

Quote :

"The secondary containment is kept at slightly atmospheric pressure - at least according to my old NE text books"

I'm assuming you meant it is kept at a slightly negative pressure compared to atmospheric pressure?

also:

Quote :

"This is Chernobyl all over again, save for the reason it occurred."

what? This really isn't very much like Chernobyl at all and probably won't end up anything like it. Scope/size, reasons it occurred, emergency handling of the problem etc. are all very different.

[Edited on March 14, 2011 at 3:46 PM. Reason : .]

3/14/2011 3:28:46 PM

PS

Quote :

"It has to be frustrating for nuclear energy safety experts that one of the principle effects of anti-nuclear power pressure has been to increase the length of time that aging plants remain in operation. Popular pressure and economic pressure makes it too difficult for some utilities to construct newer, more efficient, higher capacity plants so they can not do without the base-load capacity provided by even some of their oldest existing plants. Allowing companies or helping companies to build new plants will also allow for the decommissioning of old ones. Fighting the construction of new plants forces them to keep the old plants open longer and longer and actually increases the long term risk of nuclear accidents. "

Amen!! Yet the people fighting these don't understand that. Everyone fighting the energy battle seems to be uninformed and doesn't really understand the scope and complexity of power generation for an entire country or the fact that in most cases they are ironically hurting their own cause in the way you just described. The same goes for coal-fired plants etc. People are fighting the creation of new ones due to pollution etc. but the new ones are WORLDS more efficient and less polluting than the current ones that we could decommission if they let us build new ones! The uninformed masses don't understand why the engineering industry can't figure out how to create affordable power out of thin air with absolutely 0 impact on the environment and have it on the grid in 24 hours...

They can't understand the concept that we need a mixture of power; no one option is the best or only answer to our energy problem in the near future. Yes we would love to phase out inefficient and polluting forms of power, but it takes a long time to develop the right technology and make it affordable (both for investors and consumers). In the meantime it is imperative that we update some of these aging plants.

[Edited on March 14, 2011 at 4:01 PM. Reason : .]

3/14/2011 3:59:08 PM

Quote :

"The secondary containment is kept at slightly atmospheric pressure - at least according to my old NE text books."

You're pushing me to the edge of going to read about this now. Negative pressure is maintained for different reasons depending on specifics.

PWRs often keep very significant negative pressure as a safety measure, because if a LOCA occurred then containment can absorb more coolant before hitting the pressure limit. It makes a big difference when you have a containment rated for 50 psia and atmosphere is 14 psia, you can get a few more psia by operating with a negative pressure.

I'm almost sure this would not be the case with the Mark I design. For the reactor building we're talking about, it's reasonable that they keep a negative pressure for the same reason the campus Pulstar does, so that air will only blow in except for what is vented, which is filtered and monitored. The recent Hydrogen explosion(s) blew the daylights out of the top of the reactor building, and I most certainly hope that wasn't a significant pressure-bearing structure.

Quote :

"NHK had reported that the filtration systems were not working - at least for some time - due to complete loss of power. That might explain in part the discrete releases of caesium and iodine detected after the blasts."

It would. And venting was done with full knowledge of the corresponding radiation release. If they were blacked out this would make total sense. What we really don't want to happen is to have a full meltdown, while at the same time having no choice but to vent steam, while at the same time no power to run the filtration system. This is why I continue to say the situation is no where near as bad as the worse-case.

Quote :

"This really isn't very much like Chernobyl at all and probably won't end up anything like it. Scope/size, reasons it occurred, emergency handling of the problem etc. are all very different."

And the time frame. Chernobyl was a full-on criticality/steam explosion, TMI was decay heat after 2.5 hours, and this is decay heat after 4 days.

This accident has seen no life threatening exposures, no release large enough to substantiate cancer risk to a population with the LNT model (of TMI scale), AND we're almost 4 days into it. Cooldown of 2.5 hours versus 4 days is a WORLD of difference. The physical ability to create the corium oatmeal is substantially different in the present Fukushima reactors. The worse-case at this point would only see bulky matter spread around the internals and bottom of the pressure vessel with ceramic melting here and there. There is almost no way to melt a bulk amount of the pellets unless they've already been melted, OR a reactor was completely and totally deprived of water.

I expect to hear a great deal more about those physics, it's unprecedented up to this point. We don't have many examples of partially failed nuclear cores. We could have a few of them after these events.

3/14/2011 4:23:30 PM

^The problem is that a lot of people out there will perpetuate the "This is Chernobyl all over again" mentality further dampening the growth of nuclear

3/14/2011 4:34:05 PM

The similarity with Chernobyl is only the invisible radioactive cloud. And I grant the opposition that point, yes, a massive effluent emission is something that makes sense to be concerned about.

These accusations about the resistance of TEPCO to the facts, however, simply doesn't add up. The company has been constantly publishing the plant radiation readings and they are at points kind of bad, but for Chernobyl accident they might as well just have read "oh s*#!"

During Chernobyl we were literally detecting the radiation on the other side of the world. That's actually a fairly pesky thing about radiation, for as much as it can't be seen, it can be detected really fregin easily, particularly by semiconductor detectors that can discriminate the peaks. These are the things used to do the most accurate science in history.

For now, at least, our institutions are working in regard to the nuclear plant accident. As such, people perceive more danger, but are exposed to significantly less danger. It's a bizarre seesaw. I see the point that if we DIDN'T have media so ready to pounce on nuclear and if we DIDN'T have governmental agencies so draconian about anything nuclear, then would we really be safe? It's a valid question, and the fact of the matter is that a nuclear fission pile is not an inherently safe thing, although we can build a plant that is inherently safe within the design range.

What do other people think?

3/14/2011 5:00:07 PM

This is Chernobyl all over again.

3/14/2011 5:18:48 PM

Because if you keep saying it over and over again then maybe people will start to believe it, regardless of the facts.

3/14/2011 5:54:21 PM

http://imgur.com/r81co

3/14/2011 6:51:50 PM

3/14/2011 6:53:45 PM

http://www.nei.org/newsandevents/information-on-the-japanese-earthquake-and-reactors-in-that-region/
http://www.nisa.meti.go.jp/english/
http://www.tepco.co.jp/en/press/corp-com/release/index-e.html

WANO has a running summary for those of you with access. I would caution that WANO information is not publicly distributable.

3/14/2011 7:19:45 PM

Another explosion.

Nuclear power is unsafe and never will be.

3/14/2011 8:02:53 PM

It is unsafe when you build one in an area known as "The Ring of Fire."

3/14/2011 8:34:13 PM

Organic power is unsafe and never will be

3/14/2011 8:35:59 PM

Quote :

"Another explosion. Nuclear power is unsafe and never will be."

lol wut. No doubt this is a serious event, however with the events and situation and all the facts put in perspective you are a making a huge jump to a conclusion imo.

[Edited on March 14, 2011 at 9:07 PM. Reason : ]

3/14/2011 9:00:12 PM

Nuclear apologists.

3/14/2011 9:30:06 PM

Just a realist. We're talking about dated, 40 year old reactors using outdated seismic design and unsatisfactory/outdated redundancy in their emergency cooling systems who got hit by the largest earthquake to be recorded in Japan and among the top five largest earthquake in the WORLD since they started recording seismological data as well as got hit by a Tsunami and you are using that to say that this means all nuclear plants no matter the location are unsafe ticking time bombs and nuclear power can never be safe.

If me disagreeing with that makes me an apologist by your definition then so be it.

[Edited on March 14, 2011 at 9:50 PM. Reason : ]

3/14/2011 9:47:34 PM

it is almost sad how smc is trying to troll this thread.

[Edited on March 14, 2011 at 10:04 PM. Reason : even more sad it is working ]

3/14/2011 10:03:24 PM

smc:

Quote :

"If you want to "go green" you can't have your cake and eat it too."

[Edited on March 14, 2011 at 11:03 PM. Reason : /message_topic.aspx?topic=609672&page=5]

3/14/2011 11:02:52 PM

Coal is cleaner than nuclear power. Coal won't destroy humanity.

3/14/2011 11:06:30 PM

actually, burning coal releases more radiation than a nuclear plant

3/15/2011 12:07:15 AM

^ technically, it's only correct to say that the area around a coal plant has more accumulated radioactivity than the area around a nuclear plant. The key difference is that radioactive stuff from a coal plant lasts basically forever, unlike a nuclear plant.

3/15/2011 12:40:00 AM

its amazing to me the level of discussion (minus smc) happening in this thread. probably one of the only message boards with this level of technical discussion.

side note: what kind of base load megawatts has been lost at this site?

[Edited on March 15, 2011 at 1:26 AM. Reason : .]

3/15/2011 1:23:50 AM

my favorite is when people bring up 3 mile island...an protective feature that worked, and a operator who didnt trust his indications...great combo!

i would also like to thank Charybdisjim for the hard-on he has given me with his awesome reactor physics and thermodynamics discussion in this topic.

i would also like to add that we (US Navy) have sent Radcon Techs and Radiation Health Officers to assist the Reagan who went through the "cloud".

Quote :

" The Pentagon was expected to announce that the aircraft carrier Ronald Reagan, which is sailing in the Pacific, passed through a radioactive cloud from stricken nuclear reactors in Japan, causing crew members on deck to receive a month’s worth of radiation in about an hour, government officials said Sunday."

OH NO, NOT A MONTHS WORTH OF RADIATION!!!!!!11

[Edited on March 15, 2011 at 1:54 AM. Reason : sdfs]

3/15/2011 1:29:57 AM

Quote :

"for the same country that doesnt allow US nuclear subs in it's harbors"

i think you're thinking of New Zealand.

http://www.nytimes.com/2010/03/10/world/asia/10japan.html more info

3/15/2011 1:57:03 AM

Quote :

"side note: what kind of base load megawatts has been lost at this site?"

Fukushima Daiishi Unit 1 is rated at 460 MW, while 2 & 3 are rated at 784 MW output. If all three have to be scrapped you are looking at 2MW of baseload gone.

3/15/2011 8:07:51 AM

http://mitnse.com/2011/03/13/why-i-am-not-worried-about-japans-nuclear-reactors/

Quote :

"Construction of the Fukushima nuclear power plants The plants at Fukushima are Boiling Water Reactors (BWR for short). A BWR produces electricity by boiling water, and spinning a a turbine with that steam. The nuclear fuel heats water, the water boils and creates steam, the steam then drives turbines that create the electricity, and the steam is then cooled and condensed back to water, and the water returns to be heated by the nuclear fuel. The reactor operates at about 285 °C. The nuclear fuel is uranium oxide. Uranium oxide is a ceramic with a very high melting point of about 2800 °C. The fuel is manufactured in pellets (cylinders that are about 1 cm tall and 1 com in diameter). These pellets are then put into a long tube made of Zircaloy (an alloy of zirconium) with a failure temperature of 1200 °C (caused by the auto-catalytic oxidation of water), and sealed tight. This tube is called a fuel rod. These fuel rods are then put together to form assemblies, of which several hundred make up the reactor core. The solid fuel pellet (a ceramic oxide matrix) is the first barrier that retains many of the radioactive fission products produced by the fission process. The Zircaloy casing is the second barrier to release that separates the radioactive fuel from the rest of the reactor. The core is then placed in the pressure vessel. The pressure vessel is a thick steel vessel that operates at a pressure of about 7 MPa (~1000 psi), and is designed to withstand the high pressures that may occur during an accident. The pressure vessel is the third barrier to radioactive material release. The entire primary loop of the nuclear reactor – the pressure vessel, pipes, and pumps that contain the coolant (water) – are housed in the containment structure. This structure is the fourth barrier to radioactive material release. The containment structure is a hermetically (air tight) sealed, very thick structure made of steel and concrete. This structure is designed, built and tested for one single purpose: To contain, indefinitely, a complete core meltdown. To aid in this purpose, a large, thick concrete structure is poured around the containment structure and is referred to as the secondary containment. Both the main containment structure and the secondary containment structure are housed in the reactor building. The reactor building is an outer shell that is supposed to keep the weather out, but nothing in. (this is the part that was damaged in the explosions, but more to that later). Fundamentals of nuclear reactions The uranium fuel generates heat by neutron-induced nuclear fission. Uranium atoms are split into lighter atoms (aka fission products). This process generates heat and more neutrons (one of the particles that forms an atom). When one of these neutrons hits another uranium atom, that atom can split, generating more neutrons and so on. That is called the nuclear chain reaction. During normal, full-power operation, the neutron population in a core is stable (remains the same) and the reactor is in a critical state. It is worth mentioning at this point that the nuclear fuel in a reactor can never cause a nuclear explosion like a nuclear bomb. At Chernobyl, the explosion was caused by excessive pressure buildup, hydrogen explosion and rupture of all structures, propelling molten core material into the environment. Note that Chernobyl did not have a containment structure as a barrier to the environment. Why that did not and will not happen in Japan, is discussed further below. In order to control the nuclear chain reaction, the reactor operators use control rods. The control rods are made of boron which absorbs neutrons. During normal operation in a BWR, the control rods are used to maintain the chain reaction at a critical state. The control rods are also used to shut the reactor down from 100% power to about 7% power (residual or decay heat). The residual heat is caused from the radioactive decay of fission products. Radioactive decay is the process by which the fission products stabilize themselves by emitting energy in the form of small particles (alpha, beta, gamma, neutron, etc.). There is a multitude of fission products that are produced in a reactor, including cesium and iodine. This residual heat decreases over time after the reactor is shutdown, and must be removed by cooling systems to prevent the fuel rod from overheating and failing as a barrier to radioactive release. Maintaining enough cooling to remove the decay heat in the reactor is the main challenge in the affected reactors in Japan right now. It is important to note that many of these fission products decay (produce heat) extremely quickly, and become harmless by the time you spell “R-A-D-I-O-N-U-C-L-I-D-E.” Others decay more slowly, like some cesium, iodine, strontium, and argon. "

[Edited on March 15, 2011 at 9:33 AM. Reason : .]

3/15/2011 9:31:56 AM

[Edited on March 15, 2011 at 9:38 AM. Reason : .]

3/15/2011 9:34:03 AM

continued from above

Quote :

"What happened at Fukushima (as of March 12, 2011) The following is a summary of the main facts. The earthquake that hit Japan was several times more powerful than the worst earthquake the nuclear power plant was built for (the Richter scale works logarithmically; for example the difference between an 8.2 and the 8.9 that happened is 5 times, not 0.7). When the earthquake hit, the nuclear reactors all automatically shutdown. Within seconds after the earthquake started, the control rods had been inserted into the core and the nuclear chain reaction stopped. At this point, the cooling system has to carry away the residual heat, about 7% of the full power heat load under normal operating conditions. The earthquake destroyed the external power supply of the nuclear reactor. This is a challenging accident for a nuclear power plant, and is referred to as a “loss of offsite power.” The reactor and its backup systems are designed to handle this type of accident by including backup power systems to keep the coolant pumps working. Furthermore, since the power plant had been shut down, it cannot produce any electricity by itself. For the first hour, the first set of multiple emergency diesel power generators started and provided the electricity that was needed. However, when the tsunami arrived (a very rare and larger than anticipated tsunami) it flooded the diesel generators, causing them to fail. One of the fundamental tenets of nuclear power plant design is “Defense in Depth.” This approach leads engineers to design a plant that can withstand severe catastrophes, even when several systems fail. A large tsunami that disables all the diesel generators at once is such a scenario, but the tsunami of March 11th was beyond all expectations. To mitigate such an event, engineers designed an extra line of defense by putting everything into the containment structure (see above), that is designed to contain everything inside the structure. When the diesel generators failed after the tsunami, the reactor operators switched to emergency battery power. The batteries were designed as one of the backup systems to provide power for cooling the core for 8 hours. And they did. After 8 hours, the batteries ran out, and the residual heat could not be carried away any more. At this point the plant operators begin to follow emergency procedures that are in place for a “loss of cooling event.” These are procedural steps following the “Depth in Defense” approach. All of this, however shocking it seems to us, is part of the day-to-day training you go through as an operator. At this time people started talking about the possibility of core meltdown, because if cooling cannot be restored, the core will eventually melt (after several days), and will likely be contained in the containment. Note that the term “meltdown” has a vague definition. “Fuel failure” is a better term to describe the failure of the fuel rod barrier (Zircaloy). This will occur before the fuel melts, and results from mechanical, chemical, or thermal failures (too much pressure, too much oxidation, or too hot). However, melting was a long ways from happening and at this time, the primary goal was to manage the core while it was heating up, while ensuring that the fuel cladding remain intact and operational for as long as possible. Because cooling the core is a priority, the reactor has a number of independent and diverse cooling systems (the reactor water cleanup system, the decay heat removal, the reactor core isolating cooling, the standby liquid cooling system, and others that make up the emergency core cooling system). Which one(s) failed when or did not fail is not clear at this point in time. Since the operators lost most of their cooling capabilities due to the loss of power, they had to use whatever cooling system capacity they had to get rid of as much heat as possible. But as long as the heat production exceeds the heat removal capacity, the pressure starts increasing as more water boils into steam. The priority now is to maintain the integrity of the fuel rods by keeping the temperature below 1200°C, as well as keeping the pressure at a manageable level. In order to maintain the pressure of the system at a manageable level, steam (and other gases present in the reactor) have to be released from time to time. This process is important during an accident so the pressure does not exceed what the components can handle, so the reactor pressure vessel and the containment structure are designed with several pressure relief valves. So to protect the integrity of the vessel and containment, the operators started venting steam from time to time to control the pressure. As mentioned previously, steam and other gases are vented. Some of these gases are radioactive fission products, but they exist in small quantities. Therefore, when the operators started venting the system, some radioactive gases were released to the environment in a controlled manner (ie in small quantities through filters and scrubbers). While some of these gases are radioactive, they did not pose a significant risk to public safety to even the workers on site. This procedure is justified as its consequences are very low, especially when compared to the potential consequences of not venting and risking the containment structures’ integrity. During this time, mobile generators were transported to the site and some power was restored. However, more water was boiling off and being vented than was being added to the reactor, thus decreasing the cooling ability of the remaining cooling systems. At some stage during this venting process, the water level may have dropped below the top of the fuel rods. Regardless, the temperature of some of the fuel rod cladding exceeded 1200 °C, initiating a reaction between the Zircaloy and water. This oxidizing reaction produces hydrogen gas, which mixes with the gas-steam mixture being vented. This is a known and anticipated process, but the amount of hydrogen gas produced was unknown because the operators didn’t know the exact temperature of the fuel rods or the water level. Since hydrogen gas is extremely combustible, when enough hydrogen gas is mixed with air, it reacts with oxygen. If there is enough hydrogen gas, it will react rapidly, producing an explosion. At some point during the venting process enough hydrogen gas built up inside the containment (there is no air in the containment), so when it was vented to the air an explosion occurred. The explosion took place outside of the containment, but inside and around the reactor building (which has no safety function). Note that a subsequent and similar explosion occurred at the Unit 3 reactor. This explosion destroyed the top and some of the sides of the reactor building, but did not damage the containment structure or the pressure vessel. While this was not an anticipated event, it happened outside the containment and did not pose a risk to the plant’s safety structures. Since some of the fuel rod cladding exceeded 1200 °C, some fuel damage occurred. The nuclear material itself was still intact, but the surrounding Zircaloy shell had started failing. At this time, some of the radioactive fission products (cesium, iodine, etc.) started to mix with the water and steam. It was reported that a small amount of cesium and iodine was measured in the steam that was released into the atmosphere. Since the reactor’s cooling capability was limited, and the water inventory in the reactor was decreasing, engineers decided to inject sea water (mixed with boric acid – a neutron absorber) to ensure the rods remain covered with water. Although the reactor had been shut down, boric acid is added as a conservative measure to ensure the reactor stays shut down. Boric acid is also capable of trapping some of the remaining iodine in the water so that it cannot escape, however this trapping is not the primary function of the boric acid. The water used in the cooling system is purified, demineralized water. The reason to use pure water is to limit the corrosion potential of the coolant water during normal operation. Injecting seawater will require more cleanup after the event, but provided cooling at the time. This process decreased the temperature of the fuel rods to a non-damaging level. Because the reactor had been shut down a long time ago, the decay heat had decreased to a significantly lower level, so the pressure in the plant stabilized, and venting was no longer required. ***UPDATE – 3/14 8:15 pm EST*** Units 1 and 3 are currently in a stable condition according to TEPCO press releases, but the extent of the fuel damage is unknown. That said, radiation levels at the Fukushima plant have fallen to 231 micro sieverts (23.1 millirem) as of 2:30 pm March 14th (local time). ***UPDATE – 3/14 10:55 pm EST*** The details about what happened at the Unit 2 reactor are still being determined. The post on what is happening at the Unit 2 reactor contains more up-to-date information. Radiation levels have increased, but to what level remains unknown. "

3/15/2011 9:34:34 AM