I am currently compiling an update for the Fukishima Nuclear Accident as of March 17. The situation is developing very quickly and commenters on this thread (March 16 updates) are doing an excellent job at posting regular updates.
Meanwhile, here is a guest post from Luke Weston.
Looks like we need an update post on the situation with the Fukushima nuclear power reactors. The situation continues to change and develop, but good, sensible, detailed information is still hard to find.
In the wake of the Fukushima incident, it has really helped me to understand what happened in 1979 at Three Mile Island; with nonsense all throughout the media, and FUD, and panic spreading, with good information almost impossible to find, and with the over-abundance of bad information leading to hysteria.
But this is the first time it has happened to the Facebook and Twitter generation; I’ve yet to determine whether that’s a good thing or a bad thing. We need to keep working hard to make sure it’s a net benefit for the good information, not the dodgy information.
Design Basis Godzilla
Why wasn’t the earthquake design basis set high enough?, some people ask. What if the next earthquake is magnitude 10? Magnitude 12? Magnitude 20? But where does it stop? Where do you set the design basis? What if the reactor is attacked by Godzilla?
No matter where you set the design basis, you will always exceed it one day, eventually. And when you do, the anti-nuclearists will complain that the design basis is not set high enough.
There is always some really extreme, really catastrophic situation that you can imagine, but what is its probability in any given year?
It’s all about Probabilistic Risk Assessment.
You know what the average probability per year of a magnitude 8 earthquake in the area is, what the probability of a magnitude 9 earthquake is, what the probability of a large tsunami is, etc. I’m not sure what the probability of Godzilla attack is. Need to ask an expert. Somebody get Matthew Broderick in here; he’s the guy to ask.
And you decide what the acceptable probability of a severe core damage (“meltdown”) incident (which won’t hurt anybody but will probably write off the reactor, like TMI) for the nuclear reactor is in any given year – let’s suppose it is decided that one such failure per 50,000 reactor-years of operation is acceptable. Then, with that in mind, you design the degree of seismic hardening and safety engineering for the nuclear power plant so that you hit that target.
It is the safest way to do it which is actually realistic. You can’t say that it’s absolutely 100% resistant to any hypothetical scenario of destruction that you can imagine, because there is always something that you can imagine that is more destructive.
Seawater injection into the primary containment of Unit 1 – not into the reactor vessel itself
On 12 March, TEPCO announced that they planned to cool the Unit 1 reactor with seawater, adding boric acid to the water as a nuclear poison, to prevent any possibility of unintended criticality. The injection of fresh water and seawater into the primary containment vessel through a fire-extinguishing system line commenced on the 13th of March.
This is not an injection of seawater into any part of the nuclear reactor or the Nuclear Steam Supply System itself. It is an injection of seawater into the containment structure surrounding the reactor pressure vessel.
These reports confirm my earlier prediction that they were not talking about actually putting seawater into the nuclear steam supply system, despite the lack of any previous clear, sensible announcements in the press to this effect.
Given that the reactor pressure vessel is completely intact and the control rods were fully inserted, normally, by the Reactor Protection System at the first sign of the earthquake, and the reactor is in a completely subcritical configuration, adding additional nuclear poisons (i.e. boron) to the system is seriously overkill; there is no pressing reason why it’s really necessary, other than to be extra conservative.
ASIDE: “Going critical” isn’t some kind of catastrophe, it’s what a fission reactor is designed to do, which it normally does under normal operating conditions.
Status of Unit 2
Over March 14 and March 15, Unit 2 has been in a similar low-coolant condition to Unit 1, with coolant water being boiled off through the torus, and with the Emergency Core Cooling Systems, such as the Low Pressure Coolant Injection system, operating.
Some kind of explosion was detected in the Unit 2 reactor building on the 15th of March, in a different area to the hydrogen ignition in Unit 1 and Unit 3. This hydrogen explosion was possibly within or close to the torus (the toroidal overpressure-supression tank), which is below grade, near the bottom of the reactor building.
Although this explosion may have damaged the torus, it has not damaged any of the real containment structures, such as the primary containment structure, the drywell, the reactor pressure vessel, or the outer reactor building.
There are valves that can be closed to isolate the vents that connect the torus to the drywell. Therefore, even if the torus was damaged or breached, it can be isolated from the drywell, meaning that there’s no real pathway between the drywell (the primary containment vessel) and the reactor building, through the damaged torus.
That means that your key layers of containment are all still intact.
Status of Unit 3, and its MOX fuel
There has also apparently been a loss of some of the normal reactor coolant systems in Unit 3, and the precautionary injection of borated water into the primary containment vessel, as at Unit 1, also began on March 13 and continued through to March 14.
As with Unit 1, seawater has been being injected, in addition to fresh water, but it is into the drywell – not into the reactor vessel. There has also been a hydrogen explosion in the rooftop refueling crane space above the reactor building at Unit 3 – very similar to the explosion in the same area at Unit 1.
Fukushima I Unit 3 is currently fueled with MOX fuel, containing recycled plutonium dioxide in its initial fuel load, in addition to low-enriched uranium dioxide.
You might see some slightly different characteristics in this MOX fuel with regards to things like the void reactivity coefficient compared to ordinary LEU fuel, because the fission cross section, plotted as a function of the incident neutron energy, will look slightly different for 239Pu compared to 235U. So, if the cross-section doesn’t drop away as rapidly as you increase the incident neutron energy, for 239Pu as compared to 235U, then you might see a negative void reactivity coefficient that isn’t quite as strong. Stuff like that.
But in practice there’s no evidence that we’re seeing any neutronic behavior or thermal behavior in the fuel that is any different, in practice, as far as the emergency situation is concerned, at Unit 3 as compared to Unit 1.
There is no significant difference in the composition of the radioactive fission products, or in their potential to be released to the environment, in the MOX fuel compared to the LEU fuel in the other reactors.
What we will see, however, is a lot of “plutonium phobia” in the media with regards to this MOX fuel, which is completely independent of any rational, fact-based discussion of the science and engineering. There’s this idea in the popular consciousness that plutonium is some mysterious, almost mythical, horrifying and terrible thing, and you’re going to turn inside out and die if you ever even look at it the wrong way.
But plutonium isn’t something that’s been spawned out of the arse of a demon or something, it’s actually just another element. It’s radioactive, but less radioactive than most of the fission products formed in a nuclear reactor.
The potentially harmful radioactive materials that might be released into the environment from a LOCA scenario such as the Fukushima I-1 situation, or the Three Mile Island accident, are the radionuclides of the high-volatility fission products, such as radioisotopes of xenon, krypton, and to a lesser extent, radioisotopes of iodine. Tritium is also on the list of key radionuclides that are present within the coolant water and are volatile enougn to potentially be relased, but its relatively low specific activity compared to the hort-lived fission products and its very low beta decay energy means that tritium is not significant in terms of its potential for harm.
Uranium and plutonium, for example, are heavy metals, they’re not soluble in the coolant water, and they are nowhere near as volatile as these gaseous and volatile fission products. This means that there’s no way that these elements can escape out into the primary coolant and eventually find their way out into the reactor building atmosphere, as these more volatile elements can. This means that there’s no way that they will be released out into the atmosphere in the same way that very small quantities of tritium and gaseous fission products may be be released. Even if they could be, uranium has a negligible specific activity, and it is a negligible source of radiation dose – and plutonium is not extremely radioactive either; being less radioactive than the majority of the fission products.
The Used Nuclear Fuel
There is a small fuel transfer pool in the reactor building at each of these GE BWRs, near the top of the reactor pressure vessel, that is used for the temporary transfer of used nuclear fuel during refueling. However, the longer-term storage of the used nuclear fuel is done in a pool elsewhere on the site. Those storage pools, outside the reactor buildings, are seismically hardened and defended-in-depth, just like the reactors themselves, and there are no indications of any problems with them. Since there was no refueling going on at the damaged reactors at the time of the earthquake, there is little or no fuel in the fuel transfer pools.
That’s my understanding of the situation, anyway.
Is there actually some used nuclear fuel stored in the Unit 4 fuel transfer pool at the time of the earthquake? I don’t believe there is much, if any.
Some media reports suggest there might be; but I’m extremely distrusting of the incomplete, garbled information being filtered out through the mainstream media on this whole issue – which is why I’m trying to patiently take information in from a diverse range of sources, and to patiently, carefully and skeptically piece it together into a self-consistent picture of what we actually know about the situation, based on my knowledge of the physics and my limited but partial knowledge of nuclear engineering.
If there is some fuel stored in the transfer pool, we need to know a few things about it.
How much is stored there? How long has it been there for? When was the reactor that it was taken from powered down, prior to fuel unloading? The decay heat of used nuclear fuel drops off exponentially following reactor shutdown, as the short-lived fission products that account for most of the radioactivity rapidly and exponentially decay. After a short period of cooling, the used fuel would not be significantly heating the pool water, nor would it require active cooling.
Immediately after fission is shut down in an operating nuclear power reactor, the power output from nuclear fission ceases. However, the nuclear fuel is still extremely radioactive, at least initially, due to the presence of very short lived fission products with very high specific activities. But that decay heat output falls off exponentially over the coming hours, as the very short lived fission products decay.
Thanks to Kirk over at Energy From Thorium for preparing this excellent chart, which I’ve borrowed from the EFT blog – all credit to him. Go and check out Energy From Thorium – it’s an excellent site.
Initially, the decay heat power level – the heat emitted by the radioactive decay of the radionuclides present in the used nuclear fuel, in a subcritical configuration – is approximately 5% of the fission reactor’s normal thermal power output.
The Fukushima I Unit 1 reactor has a nameplate capacity of 460 MWe. At a thermodynamic efficiency of approximately 35%, the reactor has a thermal power output of approximately 1.31 gigawatts.
Therefore, immediately following reactor shutdown, the decay heat power output from the reactor’s nuclear fuel will be about 5% of that, or about 66 megawatts.
Over the last 5 days since the shutdown of the reactor, however, that power output has been dropping off exponentially, and it is now somewhere down around 6 megawatts of thermal power.
So, how much fuel is presently stored in the Unit 4 fuel transfer pool, if any? I might take an educated guess and say that it’s about one third of one full core loading, since about one third of the core fuel is replaced during one refueling. Let’s take a conservative guess, and say that it has been out of the Unit 4 reactor (which was already offline for maintenance prior to the earthquake) for about a week, at the least. It’s probably longer than that.
If those assumptions are valid, then the radiothermal power output from the used fuel in the fuel transfer pool will be only about one or two megawatts at the present time, and still decaying of course.
We know what the thermal power input from the fuel is, what the volume of water in the pool is, what the dimensions of the pool are, what the nominal temperature of the pool is, and what the specific heat capacity of water and the latent heat of evaporation of water are.
Therefore, we know exactly what the temperature of the water of the pool is going to do, and exactly what the volume of water in the pool is going to do. There is no need for guessing or speculation.
The nuclear fuel is made up of pellets of uranium oxide clad in tubes of Zircaloy. (Zircaloy is the trade name of the alloy in question, which is almost pure zirconium.) UO2 is a refractory metal oxide with a very high melting point – it is not flammable or combustible in any way at all. It does not burn. In theory, the zirconium metal cladding could burn, if it was removed from all cooling water, exposed to an oxygen-containing atmosphere, and heated to an extremely high temperature. However, it is almost impossible to burn a piece of zirconium in this fashion in practice.
The rate at which the water in the fuel transfer pool would evaporate, in the absence of active cooling system functionality and in the presence of the fuel’s remaining thermal power output, is not more than a few percent of the water volume per day.
Given that there is approximately 16 feet or more of water above the surface of the fuel assemblies in the pool under normal conditions, it will take many days to weeks for this water to evaporate to the point where the fuel is potentially exposed above the surface, assuming that no additional water was added by any other mechanism.
The outermost layer of the multiple layers of containment surrounding the reactors – the cuboid-shaped reactor buildings – have walls and a roof made of solid concrete. On top of the concrete reactor buildings, however, there is an additional part of the structure – it is not made of concrete, but it is made of steel, with steel sheets over a steel frame. This steel building on top of the reactor building houses the fuel transfer crane, and it is built on top of the concrete roof of the reactor building.
That is, the part of the structure above the concrete shield plug and the refueling platform at the top of the concrete reactor building, as shown on the diagrams below.
It is this relatively weak steel structure on top of the reactor building, which is not really part of the reactor building proper, which has been blown out by a hydrogen explosion at Fukushima I Unit 1, as I described in my previous post, and apparently at one of the other Fukushima I reactor buildings as well.
The concrete roof of the reactor building proper – which is not where the hydrogen explosion occurred – is built over the top of the temporary fuel transfer pool; the pool is protected within the concrete reactor building.
Unit 4 Explosion and Fire
On 14 March, an explosion of hydrogen gas in the steel-framed structure atop the Unit 4 reactor building occurred, similar to the earlier explosion at Unit 1. As was the case at Unit 1, there was no real damage to the reactor building proper or any of the other layers of containment within.
On March 14, a fire was reported in the Unit 4 reactor building. The fire was caused by a leak of lubricating oil in the mechanical drivetrain that drives the reactor’s recirculation water pumps. Contrary to inaccurate information which was spread widely in the media and the social-media grapevine, this small fire had absolutely nothing to do with the used-fuel transfer pool or any fuel which may have been in it. The fire was extinguished shortly after.
Detection of radioactivity off the coast
It has been reported that the crew of the Nimitz-class carrier USS Ronald Reagan, off the Japanese coast, has detected the presence of radioactivity emitted from the Fukushima nuclear power plant. Since she’s nuclear powered, the vessel is obviously carrying sensitive instruments and sensors for detecting the presence of radioactivity around the ship, and obviously they’ve detected the trace levels of radioactivity that have escaped into the atmosphere.
It’s possible to measure the presence of small traces of radioactivity fairly easily with extremely high sensitivity. Just because we’re able to accurately measure it and quantify it at very low levels doesn’t mean we’re dealing with levels of radioactivity that are anywhere close to harmful levels.
Has anyone actually reported the actual quantitative presence of radioactivity that was detected aboard the ship?
The status of the Fukushima II plant
At the time of the March 11 earthquake, all four operating units at the Fukushima II station were automatically SCRAMmed by the Reactor Protection Systems.
Although there were some reports of disruptions to the Emergency Core Cooling Systems at Fukushima II, all the Emergency Core Cooling Systems at all the reactors were restored to operational status.
Between March 12 and March 14, every one of these reactors has been bought to a safe state of cold shutdown, where the decay heat from the nuclear fuel is being completely dissipated and the fuel is being kept cool, with no rise in fuel temperature.
195 replies on “Fukushima redux – design basis Godzilla?”
What may be the source of the high levels of radioactivity? That doesn’t square with your assumptions about the amount of spent fuel in the tank, IMO. The reactor was taken offline on Nov 30, per IAEA by the way.
It might be extremely cynical, but there is a magnitude of earthquake that will cause all buildings to collapse, killing all inhabitants and obviously it doesn’t matter then that the reactor doesn’t survive – as long as the effects remain local. Perhaps successful SCRAM wold suffice for that.
I predict that one day Finrod will eventually die (of natural causes) much like the rest of us. My statement is about as interesting and useful as his is.
Good clear post Luke. I have one question. Is your
fission power display graph dependent on some level of cooling?
I need to repeat a question from yesterday …
Below is part of a post by “Michael R James” over on Crikey.com who seems to be claiming that
heat can be generated inside the reactor vessel if the cooling is absent:
“The other thing Barry Brook probably regrets claiming, is that these containment vessels will contain the fuel no matter what. That is simply nonsense. I think it comes from the misunderstanding about any original claim or design specification–which assumes some level of cooling. Once you have inadequate cooling, forget it. With full meltdown the fuel forms a pool which heats even more than the pellets–because it is no longer moderated. It can never approach criticality–ie. like a nuclear bomb, but low level fission continues so it just keeps heating up. At a couple thousand degrees (if not before, remember there will be intense steam pressure by then, it is like a massive pressurized can) the steel will melt or soften enough for welds to give etc. By memory (dangerous but you can Wiki this) it can reach up to 5000 degrees so absolutely nothing can contain it.”
Thanks Barry & Luke.
Well done. I do have very minor issue with the term ‘no way’ regarding leakage, preferring ‘appears extremely unlikely’.
My questions are regarding the apparent gaping hole in the side of the #4 containment building? and the impact of possible loss of most or all water in the fuel storage pool? (recognizing that the pool doe snot abut the exterior wall of the building.
I predict that one day Finrod will eventually die (of natural causes) much like the rest of us. My statement is about as interesting and useful as his is.
The point being that there is always a finite level of physical disruption which will be accounted for in the design of any physical system, and above that there will be a higher level of physical disruption which is possible… and indeed inevitable, if you wait long enough.
There will be many useful lessons drawn from this accident. Or at least, they’ll be useful so long as our civilisation doesn’t surrender to the counsel being offered by the anti-nukes.
“The rate at which the water in the fuel transfer pool would evaporate, in the absence of active cooling system functionality and in the presence of the fuel’s remaining thermal power output, is not more than a few percent of the water volume per day.”
Except the fact that the pool on 3 and 4 have COMPLETLY evaporated, and are emitting enough radiation to kill or incapacitate anyone near the pool.
Question: What is happening to the water that is being poured onto/into the reactors? Is it likely to become contaminated or have high levels of radiation etc? I’m wondering where it is being drained to. Is it collected or returned to the sea?
He should be so lucky ..
Unit 4 was in a refueling outage and had offloaded the complete core for a vessel inspection. They have a complete core plus fuel still cooling off from the previous outage. It has the most fuel in the pool compared to any others. That is why the NRC has made statements that they have about the most of the water being boiled off. They now the number of sticks in the pond and the decay heat curves plus the info of the SFP temp last reported (84C I believe). Its not to hard to calculate the results.
Luke thanks for the clarity about the storage pool and the transfer pools, not that there is much clarity in reports about what exactly they are having problems with:)
Sorry that is “reports as in “media reports”, not some sort of accusation!
I agree it is not possible to build anything that is 100% reliable under all circumstances, but in the Risk Assessment one needs to look at not just the probability of the event occurring, but also the impact of the event. Only then can you decide if the project is worth considering and what other options are available.
There will be many useful lessons drawn from this accident. Or at least, they’ll be useful so long as our civilisation doesn’t surrender to the cowardly counsel being offered by the anti-nukes.
Um…. maybe put the generators or backup generators somewhere dry in case there is a 7m wave instead of 6.5m wave? Or is that just being cowardly?
Luke could you provide some more context for the comments below from your blog…
And of those 53 power reactors, only one is behaving in a somewhat abnormal way in its shutdown state – Unit 1 at the Fukushima I Nuclear Power Station. (Fukushima Dai-Ichi, as opposed to Fukushima Dai-Ni, which is the Fukushima II plant.) The other 52 are completely normal, either operating or behaving as predicted in a shutdown state. To see that 52 out of 53 are behaving completely normally, and many are still operating normally, generating electricity on the grid, in the wake of one of the strongest earthquakes the world has ever seen in an industrialized area, shows you just how resilient nuclear power infrastructure is in response to natural forces like this.
UPDATE: At the time I wrote this, what I above was accurate and there were no concerns about the state of any of the power reactors other than just this one. It is now the case that there are issues at a couple of the power reactors, and the above is not strictly accurate. However, the phenomena and the systems I have described below in the context of Fukushima I Unit 1 are still relevant to understanding what is happening at the other reactors.
You state that only a small proportion of used fuel from a given reactor is stored in the pool adjacent to it. This is at variance with most (all?) mainstream media reports, which claim that essentially all of the used fuel rods are there. (“There” = “fuel storage pool” in Figure 20, Mark I schematic, in the body of your post.)
In Congress today, (US) NRC Chairman Gregory Jazco’s Congressional stated that he thought the spent fuel storage pool of Unit 4 is dry, and that he has gotten reports that Unit 3’s pool may be cracked and losing water. link.
Can you or Barry comment on these two questions? I also posed the first question to the MIT Nuclear Science & Engineering students running the new MITNSE blog, which appears to be developing into a reliable source of information.
ATOMS, on 17 March 2011 at 12:47 PM — You cannot possibly know that. Stick to the facts.
If there’s so little spent fuel stored in the pools, why don’t the plant officials just say so? And why are the pools heating up, when you claim they shouldn’t do so? And why the need to go to all these desperate efforts to add water to those pools? And what is the source of the large plume of steam from unit #3, or the spike of radiation associated with the fire atunit #4?
On another matter, it was my impression that the fear of “accidental criticality” was the reason for adding boric acid to the seawater. If, as you claim, seawater is only being added to the drywell, not the reactor vessel, why would that fear exist? And since we know that the fuel rods have been partially (and in the case of unit #2 possibly fully) exposed, are you saying they are maintaining two separate water pumping systems, fresh water for the reactor vessel, seawater for the drywell?
Forgive me, but reading this is giving me flashbacks to Baghdad Bob.
If you add the shared storage (60%), the pools at units 1, 2 and 3 (17%) and the dry storage (6%), there’s 83% of the spent fuel storage capacity with status currently unknown.
Barry and others (Luke on this post),
Good job on getting concise no-nonsense information out. But I think Luke needs to re-think some of the information about these pools. For example unit 4 has more fuel in it than you are assuming. Plus, the refuel floors of these units have been through an earthquake, hydrogen explosions and fire. I wouldn’t assume that the pools of unit 3 and 4 have all their water available to them. The USNRC has stated that they believe the unit 3 pool has a crack and the unit 4 pool doesn’t have much if any water in it.
And of those 53 power reactors, only one is behaving in a somewhat abnormal way in its shutdown state – Unit 1…..UPDATE: At the time I wrote this, what I above was accurate and there were no concerns about the state of any of the power reactors other than just this one.
So there’s no power or cooling after a 9.0 earthquake & tsunami and you have “NO CONCERNS” about units 2,3,&4??? WTF.
Blind optimism is useful in many walks of life but nuclear power isn’t one of them.
Um…. maybe put the generators or backup generators somewhere dry in case there is a 7m wave instead of 6.5m wave? Or is that just being cowardly?
What in the world are you on about?
I was referring to calls to shut down the nuclear power industry worlfwide and abandon it forever.
To whoever censored my introductory comment: How did I violate the rules with that one?
@Dan: Drive-by accusations of this sort only underline the complete intellectual bankruptcy of the overwhelming majority of the antinuclear posters here. When you can’t make a real argument, the traditional fall-back position is that anyone that disagrees with you must be an industry shill. It is getting tired.
Today’s iaea report:
gives temperatures in SNF pools at 4,5 and 6. It’s
hard to see how they could do this if the pools were
dry. Does the absence of data for 1,2 and 3 indicate
no fuel being stored or no water?
Well, several sources including tepco said that the water level is low, and they can’t get people in, that’s why they are using helicopters, and said they can’t even hover them on the site because ot the radiation…
I went to your link, and I see “16 March, 05:00 UTC: no data” for the pool in unit #4, which is the one that is allegedly dry.
Glad that PRA is finally being discussed! Watching the hearing on the Hill today was frustrating. Sen. Boxer was harping on the fact that the plant in Japan was “only” designed for a magnitude 7.5 (or whatever the correct magnitude is, I’m not sure), but not for a magnitude 9.0.
Just saw tepco say on NHK that they still found water in the 4th reactor pool and none of the fuel rods are above water. Therefore, they’re focusing on cooling down the 3rd reactor. They just sprayed water via helicopter, and they’re readying to spray water from the ground as well.
There is also talk of possible restoration of power to the 1st and second reactor from an external source. I haven’t really found why only the 1st two reactors are considered for restoring power, nor I don’t know where they’re bringing the power from.
“There are valves that can be closed to isolate the vents that connect the torus to the drywell. Therefore, even if the torus was damaged or breached, it can be isolated from the drywell, meaning that there’s no real pathway between the drywell (the primary containment vessel) and the reactor building, through the damaged torus.
That means that your key layers of containment are all still intact.”
You leap from the statement that valves cam be closed, to the assumption that they were closed without offfering any evidence that this is actually true.
Can you offer your reeasoming for assuming that the valves were closed?
Luke Weston wrote:
Why wasn’t the earthquake design basis set high enough?, some people ask. What if the next earthquake is magnitude 10? Magnitude 12? Magnitude 20? But where does it stop? Where do you set the design basis? What if the reactor is attacked by Godzilla?
You are using mockery to make it sound as though it is stupid and absurd to ask why these plants were not built to withstand a magnitude 9.0 quake and attendant tsunami. But that is not an absurd question at all, in the way that it would be absurd to ask about a magnitude 20 quake (100 billion times as energetic as this quake), or about Godzilla.
Firstly, quakes of this magnitude are known to happen. Second, the Japanese Govt and the nuclear authorities there have been warned in the last ten years that the safety standards to which these reactors have been designed are insufficient for the known risks of geological instability in the area where they have been built. But they declined to act.
Lastly, you suggest that once we have set an acceptable risk threshhold, that we should just have done and design to that threshold. That would be fine if estimating risk were an exact science. But of course it isn’t. We might think that a magnitude 10 quake is a once in a 10,000 year event. But really, that is just an educated guess based on our current, imperfect knowledge of geology and tectonics. It has a pretty wide error term around it which we ought to plainly acknowledge So if we wish to avoid hubris, we should substantially over-engineer, even to our chosen acceptable risk threshhold.
My understanding is that these reactors were designed to withstand an 8.2 quake. To me, that looks to have been an incredibly stupid design decision and a legitimate target of criticism. The warnings to this effect in recent years show that this is not merely the wisdom of hindsight, but that we are dealing here with genuine folly.
“What if the reactor is attacked by Godzilla?”
Which is why it is preferable to use technology where the worst case isn’t so catastrophic if something does happen that in fact you were unable to plan for.
Steve Gardner, on 17 March 2011 at 2:05 PM — It is not clear that there is a rock which could support enough strain to occasion an earthquake with a magnitude in excess of those already measured.
Granted that when the earlier units (and perhaps the later ones) were designed and built, plate tectonics was not fully understood. However, it is now known and has been for two to three decades that subduction zones are generally capable of creating magnitude-9 earthquakes with quite large tsunamis. These attributes of subduction zones are a *feature*, not a weird, unlikely, unforeseeable bug. You don’t have to be an earth scientist to know this. I am very surprised and disappointed that this is not being acknowledged here.
In contrast, magnitude 10 to 12 earthquakes have never been documented from terrestrial causes and are only expected from the impact of very large extraterrestrial objects. Citing them in relation to the rational assessment of seismic hazards is a straw man, nothing more.
Even back in the late 60s, we’d already seen the 1964 magnitude-9.2 Alaska earthquake and tsunami, and the 1960 magnitude-9.5 Chile earthquake and tsunami with waves up to 25 meters in height, both occurring in areas that are very active geologically. Japan is one of the most geologically-active places in the world. Even back in the late 1960s, prudence would dictate especially high engineering standards for nuclear facilities in such a location, with extra attention being paid to backup systems.
Once subduction zones were well understood, the plant owners had two to three decades to reevaluate their facilities and retrofit main and backup systems (for instance, relocate emergency generators) to account for advances in the earth sciences and the sure knoweledge that they are in close proximity to (actually, overlying) a subduction zone that very reasonably could be expected to produce an earthquake and tsunami of the nature just experienced.
They failed to do so. In a U.S. court this would be ruled criminal negligence.
I can’t believe that this atrocious breach of responsibility is being defended by those who so strongly assert that they are fact- and rationality-based. This Godzilla post is simply not credible and harms your case.
Bruce Schneier discussed what you are referencing in this post, Luke. He called it “Worst-Case thinking.”
Here’s a link to his article:
If seawater is not being pumped into the core, what isthe use of adding boric acid to it. Outside the pressure vessel, this boron will have little if any neutron absorption effect.
Oops- that should be “knowledge” in the fourth paragraph. My careless error.
The reactors rode out the quake. The tsunami did in the EDGs. If you look at the site using Google Earth, you can see that they (TEPCO?) excavated the existing 100 ft plus bluffs down to near sea level for the plant site. Why? Probably to reduce the head that the seawater cooling pumps would have to work against if the plant had been placed on top of the bluff. Possibly also to reduce the opportunity for an earthquake to cause the bluff to crumble and the plant to crash into the sea, but the plant could have been placed far enough back from the bluff edge to eliminate that possibility. Lastly, by excavating the plant site down, they placed the plant below the line of sight for anyone inland looking out to sea. Was it for PR purposes (“out-of-sight, out-of-mind”), or was someone thinking that if there was a massive radiation (not contamination) stream, the existing bluff would act as a natural shield? I don’t know.
What I can say is if the EDGs had been placed on top of the bluff and just cables run down to the reactors, then this accident would have been a non-event. This would also have separated the EDG fuel from the reactors.
What this accident reminds me of is the events that lead to the SUBSAFE program. We didn’t stop building subs, but we took a long hard look at design and construction.
FYI, I am a retired USN LCDR, Qualified Engineer, EOOW and PPWO on Nimitz-class A4W plant.
I don’t know if it’s already been mentioned but a big irony of this is that AFAIK, three generators with a more than adequate supply of steam to run them are completely shut down and unused and were unused right from the beginning of this event. Is there any reason why they couldn’t have kept running the generators using the residual decay heat they are trying to get rid of? The generators could keep producing power for as long as the heat lasts and of course, once the heat is no longer significant, the power is no longer needed.
Somewhere on the Richter scale there is an Extinction Level Event [ELE]. An ELE = 100 million megatons equivalent explosive power. I guess that might be around 13 on the Richter scale. There is clearly no need to design for more than that. A better thing to do is to replace Gen 1 and Gen 2 reactors with Gen 4 unmeltable reactors.
The real thing that needs to be done is education. So far there have been ZERO casualties at Fukishima. Yet people in the US are buying iodine pills. Coal company propaganda is very effective. Where is the vaccination against this nonsense?
People have to be in panic to do things as foolish as take iodine pills when they are thousands of miles away. They don’t know basic things like that there has always been natural background radiation. They don’t know how big a millisievert is. They don’t know how big a lethal dose is. And they don’t know that TV journalists don’t know anything about it.
@Bill DeJager – The problem with criticisms of this type, is that very few make them about other technologies. Somehow, nuclear plants are held to much higher standards than other installations that might fail. Keeping in mind that it was the tsunami precipitated the failures at these reactors, and not the earthquake, are you going to make the same criticisms of everything else, man made, that got washed away in this event?
In other words, if what you are suggesting, that it was incompetent not to design and build these plants to survive this scale of event, are you making that accusation for every other structure that was damaged. Because if you are, I note that these other failures led to very large death-toll, far greater than what the reactors have been responsible for. If you are not, them I submit you are being hypocritical.
If you live in Chernobyl the total radiation dose you get each year is 390 millirem. That’s natural plus residual from the accident and fire. In Denver, Colorado, the natural dose is over 1000 millirem/year. Denver gets more than 2.56 times as much radiation as Chernobyl! But Denver has a low cancer rate.
Calculate your annual radiation dose:
Average American gets 361 millirems/year. Smokers add 280 millirems/year from lead210. Radon accounts for 200 mrem/year.
Although radiation may cause cancers at high doses and high dose rates, currently there are no data to unequivocally establish the occurrence of cancer following exposure to low doses and dose rates — below about 10,000 mrem (100 mSv). Those people living in areas having high levels of background radiation — above 1,000 mrem (10 mSv) per year– such as Denver, Colorado have shown no adverse biological effects.
Calculations based on data from NCRP reports show that the average level of natural background radiation (NBR) in Rocky Mountain states is 3.2 times that in Gulf Coast states. However, data from the American Cancer Society show that age-adjusted overall cancer death in Gulf Coast states is actually 1.26 times higher than in Rocky Mountain states. The difference from proportionality is a factor of 4.0. This is a clear negative correlation of NBR with overall cancer death. It is also shown that, comparing 3 Rocky Mountain states and 3 Gulf Coast states, there is a strong negative correlation of estimated lung cancer mortality with natural radon levels (factors of 5.7 to 7.5).
So media reports are talking about the risk of the fuel rods in spent fuel pool #4 melting down. But the pool was probably around 25 C when the quake happened on the 11th, and on the 15th it was at 84 C. That’s not a very scary rise in temperature, considering the fuel rods melt at 2000 C. It seems there’s not very much decay heat. With the water moderator gone, the reaction (if any) will slow down if anything. I must be missing something here.. Why is this a concern at all??
The common single point of failure in this accident was power outage. You need power to cool the reactors (and SFR pools). You need to actively cool the reactors. Period.
By all reports the generators were not knocked out by the earthquake they were knocked out by 1m of water coming over the wall. Not one or two generators were knocked out… ALL the generators and backups.
You don’t a 10 billion dollars to put your generators 3 meters higher or maybe backups on the other side of the building. It doesn’t cost much to put your generator’s fuel tanks underground or somewhere where they can’t be easily knocked around. You don’t need “Probabilistic Risk Assessment” to see there’s a big damn ocean at your doorstep and know the ocean can be big and angry.
I agree that you can’t plan for everything but don’t hide behind “Probabilistic Risk Assessment” when reality doesn’t fit the plan. It isn’t necessary to label people anti-nukes for questioning assumptions.
I have been reading updates and comments for 4 days now from this site.
I have no experience or education with regard nuclear technology and reactors.
I observe that there is an enormous effort on this site to deliver informed data and opinion (based on education and experience in the respective field) combined with an effort to dispel flawed data and misinformation offered by the media.
That being said, I find an enormous disconnect between the apparent conclusions (and assumptions) posted on this site and the documented activities and radiation levels posted on apparently reliable media sources linked from this site.
I also find an enormous disconnect between the levels of risk presented by the (apparently) educated posters on this site, compared with the type and level of response from workers at the site of the incident and the indicated levels of radiation detected at the site.
Despite my levels of ignorance with nuclear technology, I am intelligent and aware enough to recognize a significant disconnect with what is being reported by the media and what is being reported on this site.
I would appreciate a response that seeks to resolve the clear disconnect I have suggested.
Net/Net, if there is little to no threat of a primary containment breach and there is little to no stored fuel in the storage ponds, and this is really not a big deal, why does the level and complexity of response escalate day by day. Why do the peak levels of recorded radiation continue to increase day by day? Why are apparently informed and educated organizations, escalating their response and reaction to the event day by day?
I would appreciate an informed and detailed response.
fp: every report I’ve seen indicates that there being no water would be a serious problem.
Secondly, umm maybe the concern is that while the fuel melts at 2000C the water boils at 100C…
Look I’m no nuclear expert by any stretch, but as a general rule when I have an “idea” about something I don’t know much about, that seems obvious – so obvious that it is staggering the experts can’t see it, and that would solve all of their problems… well I generally assume I’m wrong:)
The last english NISA release ( http://www.nisa.meti.go.jp/english/files/en20110317-1.pdf) stated that the operators were injecting sea water into the Reactor Pressure Vessel (RPV) of Unit 2 and into the Primary Containment Vessel (PCV) of units 1 & 3. Can you interpret their teminology for me?
Luke – It makes no sense to me to inject seawater (SW) into the annular volume between the Rx vessel and the primary containment. This would attempt to cool the water/steam mixture inside the RX vessel and therefore reduce the pressure by conducting the heat away through the Rx vessel? If the purpose is to keep the core covered, and demineralized water is not available, then any type of water in the core is better than no water. Sure, the SW would boil, increasing the salt concentration, but who cares. At that point, you’re going to decommission the core and pressure vessel & piping anyway.
I think your flowpath only makes sense if the operators do not have working high-pressure pumps and/or electricity to power them, so they can’t get water into the Rx vessel against the pressure. That creates a catch-22 situation: if they vent enough steam to lower the pressure to a point where they can pump water in, then they risk flashing the existing water in the core and possibly uncovering the fuel elements. They would have to be ready to start water flowing into the core as soon as the pressure became low enough (piping with check valve and pumps already running at shutoff head), because if they tried to vent steam to lower the pressure, then shut the vent valves and then start the pumps/open the pump outlet valves, the Rx pressure would have already risen and there would be no flow into the core.
“fp: every report I’ve seen indicates that there being no water would be a serious problem.”
Yes. Why? The water acts as a coolant, but it seems the rods don’t need much cooling if it takes them 4 days to heat the water ~60 degrees.
fp: Because that’s a large volume of water that’s being heated. Heat transfer to air is far less efficient, so absent the water, most of the heat stays in the much smaller volume of the fuel rods themselves, hence heating them up much, much faster.
Water boils at 100C. Boiling water evaps quicker. Once the water gets to a certain level above the rods, it doesn’t take much time for the temp of the rods to start to increase rapidly. The temp of the rods will get high enough for an accelerated zircaloy water reaction. Hydrogen is created (exposion/fire on refuel floor of unit 4). Clad oxides rapidly to failure releasing fission gases and associated radionuclides. High dose rates and a hot spot on the ground between the two reactors (300 mSv/hr) is probably debris expelled from the SFP. We didn’t see the pool steaming away on unit 4 because the secondary containment covered it. I think we’ve been seeing the pool on unit 3 steaming away over the past two days.
All of the pools should be the real concern now, plus the cores of units 5 and 6 (either partially loaded or completely loaded).
There must have been some damage from the quakes to the pools of 3 and 4 for them to get so low.
This statement of yours seems (alas) to be incorrect.
“There is a small fuel transfer pool in the reactor building at each of these GE BWRs, near the top of the reactor pressure vessel, that is used for the temporary transfer of used nuclear fuel during refueling. However, the longer-term storage of the used nuclear fuel is done in a pool elsewhere on the site… Since there was no refueling going on at the damaged reactors at the time of the earthquake, there is little or no fuel in the fuel transfer pools.”
A reader at the MITNSE blog provided this link to a TEPCO slide presentation of 16 November 2010 PDF). Slide 9 shows the status of the spent fuel pools and the separate on-site longer-term storage facility.
As of March 2010, there were 3,450 fuel assemblies in the four pools at the reactors, an average of ~900 per pool. A reactor core contains about 600 assemblies (I’m not sure about that number).
Yes, that seems to be the case amac78. As Tony Irwin pointed out, according to the IAEA, unit 4 was shutdown for routine maintenance and refuelling on 30 Nov 2010 and all the fuel core (548 fuel assemblies) transfered to the SF pond. Units 5 and 6, although shutdown, have the fuel back in the core, so there will only be about third of the core spent fuel from refuelling in their SF ponds. Similarly for units 1-3, I would expect there to be SF from the last refuelling in the reactor SF pond as most of the previous SF will have been transfered to the shared SF pond. This may explain why unit 4 reactor SF pond is more sensitive to loss of normal cooling.
Clearly, nuclear plants need to hire Mothra.
I want to point some facts about current situation that appear to be false in the article and also in some comments.
1. The Fukushima Daiichi plant was designed to withstand 8.2 point seizmic activity very likely occuring directly below the plant and not som 100km away. So the actual seizmic acitivity at the plant was LOWER than 8.2 it was designed for. And as such it withstanded it probably without any serious harm.
2. The 1st. reported damage came with the tsunami size of 7m exceeding the level the plant was designed for. This is the main source of the catastrophic events that unfolded here. It was predictable that such big tsunami eventually hits here, so this is presumably the mistake made by planners of the plant.
3. The sea water IS pumped directly to the reactor core and also to the primary containment as reported by almost all status tables reported at this site.
Last one I saw is from 9h JST today: http://www.jaif.or.jp/english/news_images/pdf/ENGNEWS01_1300322727P.pdf
4. Also in the document mentioned before, there is a reported low level in both 3 and 4 reactors SFPs and also Damage to fuel rods in poll 4 suspected.
5. There has been report of LOSS OF LIFE of at least one worker: http://www.world-nuclear-news.org/RS_Battle_to_stabilise_earthquake_reactors_1203111.html
Numbers 1. to 4. are at stright contrast to this post statements. Number 5. disproves one comment under this post, but could not locate now.
Help a layman out here. You are saying they are spraying water OUTSIDE the reactor? Wouldn’t that be like cooling the inside of my oven by spraying water on the outside of the oven door (Or submerging it if the containment structure is intact). And don’t they eventually need to replenish the water in the reactor after venting?
The number 5. was responding to this comment:
Asteroid Miner, on 17 March 2011 at 2:35 PM
Also I see, there has been a mixup between Celsius and Fahrenheit here. To my understanding the zirkonium casing melts at 1200 C (= 2200 F) and not 2200 C.
AFAIK reactor 4 was shut down in november. Then it was de-fueled in preparation of an inspection to the chamber. There is at least a full load in the pool and it’s not extremely old. I would not be surprised to learn it still gives a thermal megawatt or three.
Can it heat up to the equivalent of a partial meltdown? I’m no expert and do not know. But at minimum I’d expect those rods, especially if exposed, to be very happy to oblige the no-nukes and provide abundant cesium and iodine injections straight into the environment.
Containment vessels work as intended. But only for the rods you put inside them, not for those you put beside them.
Two things, IMO, are dangerous in Fukishima Daiichi: a core meltdown (no, I do not think it would be contained. In case of a full meltdown there will be an explosion and we’ll have all sort of fission products flying up a few hundred meters) and these “spent fuel” rods with no containment at all.
Neither is directly dangerous for humans further away than a bunch of kilometers. Both are extremely dangerous in terms of indirect effects (food chain) if very meticulous checks are not implemented. This is no Chernobyl, unless we make it so. The lesson from Chernobyl is not about graphite, it’s about vegetables and milk.
In the interest of keeping this site useful for those looking for reasoned discussion of the fluid situation in Japan, it would be helpful if we could dispense with the off-topic comments and opportunistic anti-nuclear dribble. It is tiresome and unproductive.
@steve it’s more like cooling a pressure cooker that sits in the kitchen sink by filling the sink with cold(er) water.
Anyway pretty all reports I’ve seen say that they are actually pumping seawater into the reactor vessel itself, not just the containment vessel.
Your statements about seawater are not in accord with the JAIF reports which explicitly state that seawater is being injecteted into the core *and* the containment vessel for units 1,2 & 3.
NHK/TV (English) reports that the wind, which has been blowing west, will shift to the north, on Friday.
Jan. True. But it was stable at 84 on the two previous days … seems more likely that “no data” on that day means “no data” … but tracing back to the Japanese Nuclear and Industrial Safety report:
Click to access en20110317-1.pdf
provides no statement that any pool is dry in any of the timelines. I would think this would warrant
a mention if it were true so I’m not sure where the NRC Chairman is getting information from.
[ad hom deleted]
opinion is being mixed with updates in the articles… the result is debates on multiple topics like Unit 4, background radiation, Design Basis and Godzilla. I agree that it exhausting and lacks a cohesive thread.
Can I suggest posting the splitting updates into more discrete topics? I think it would help keep the commentary more focused.
The tsunami deaths were not the result of structural failures of buildings. Even had the buildings stood, everyone unable to get above the level of the wave would have been swept away and drowned. In one of the towns in Miyagi, the tsunami drill involved sheltering on the 3rd floor above of the local hospital. Unfortunately, the wave reached the 3rd floor and everyone sheltering there was swept away and drowned. But the building was not destroyed; those sheltering on the 4th floor and the roof survived.
> there is little or no fuel in the fuel transfer pools.
Please skim back through the earlier threads for references already provided — just search for “pdf” and “ppt” file references, if nothing else.
On that one, for example, I cited the PDF giving the June 2010 fuel inventories for the cooling pools in the first thread, four days ago, and have repeated it at least once since.
I’ve also pointed in earlier topics to the references about pumping seawater into the cores as well as the containment — doing so against steam pressure to try to keep the core covered; how that was stopped by a stuck valve; pressure readings, and so on.
If you can refute a factual claim please cite a source, we all need to be checked and facts corrected here, very few of us are working with anything first hand.
@fp As already pointed out, a lot of water takes time to heat up. I’m no expert but water in those pools is supposedly circulated or at least replenished. This is what is not happening now. If it evaporates or boils out it will stop working as a moderator, but also as a refrigerant. The main concern however is not that those rods can go back critical, but that they are not “contained”. AFAIK water circulation (and low temperatures) is what is supposed to filter volatile fission products for the rods in those pools.
@Tomas Zirconium melts at 1855°C (3371°F). The rods are made with a Zircaloy (an alloy with around 98% zirconium) so the exact melting point may be a little less than that, but I doubt they can go all the way to 2200° (either C or F).
Just realized it: 1855°C is 2128.2 K, so that 2200 figure is probably just that.
“Why wasn’t the earthquake design basis set high enough?, some people ask. What if the next earthquake is magnitude 10? Magnitude 12? Magnitude 20? But where does it stop? Where do you set the design basis? What if the reactor is attacked by Godzilla?”
Just this sentence makes it clear enough that you have no idea about the probability of a mega thrust event hitting Japan. Just by this introduction I was turned of to read the rest of the article, I am sure it doesnt worth my time anyway.
If you want to know what the earthquake hazard is for Japan, here is a good start:
If you decide you want to research a bit more on historical earthquakes and tsunamis that have hit the area, I will be happy to provide references of published studies.
Till then, I say you have no idea about what you are talking about.
look under the knowledge link in that site, thats what you luck.
In case its to hard to navigate through the links here you go.
Click to access eval_sdz_eq.pdf
@Steve Gardner – So you are saying the only structures adversely effected by the tsunami were the reactors? I’m afraid the record fails to support that contention. Trains were washed off their tracks, and levies were breached all over the country that had been built to defend against tsunamis.
The fact is that there are failures of structures and installations in Japan that have cost lives, items that were claimed to have been designed to protect people from this type of event. You cannot single out the nuclear power stations in this regard, particularly as their failures have not had the impact others have.
It is simply hypocritical to hold a nuclear power plant to a higher standard than any other installation the failure of which could potently cost lives.
The fuel rods stored in the spent fuel pool (SFP) at unit #3 are the main concern right now. The water level is *not* gone, but it is getting very low. There was a helicopter survey yesterday which determined that there was still some water in the SFP at unit #4. So, SDF helicopters dropped some water on #3 instead this afternoon, and water cannon trucks are going to spray water up into the #3 SFP soon. This operation is critical to prevent a major release of radioactivity.
The pools at #5 and #6 have less spent fuel in them than #4. Unlike #5 and #6, all of the #4 fuel rods were removed from the core and put into the SFP there. However, the temperatures of the SFP’s in #5 and #6 are increasing and will become a concern if power is not restored to run water pumps for the facility.
@DV82XL — I do not single out nuclear power stations for this kind of scrutiny. If levies could have been built to withstand an tsunami of this magnitude, then it was indeed a very serious failure of planning not to have built them. (And you may recall there was intense criticism of the levees around New Orleans after Hurricane Katrina.)
Nevertheless, there may be a good reason to hold nuclear power plants to a higher standard than other kinds of installations, and that is the long term consequences of failure. Miyagi and Iwate prefectures have been devastated, but the clean up and rebuilding can commence almost immediately (just as New Orleans is being rebuilt.) I won’t pretend to expertise I don’t have, so I’ll phrase this as a genuine question: what is the long term prognosis for the plant and the 20-30km exclusion area around it, if there is a serious breach in containment? Will people still be able to live there?
The meat of the situation is the safe design issue. Of course nothing is 100% safe,but I have to wonder whether this site was realistically safe. Given most years the globe sees a mag. 8-8.9 earthquake somewhere,and plenty of evidence for large tsunami in the past on many of the world’s shorelines,the plant seems to have under-engineered on tsunami defense. Did cost-benefit analysis really find that this was acceptable?
I also have to ask,while recognising that there are limits to what can be spent on safety, is the layout really the best they could arrive at? I know space is at a real premium in Japan,but everything is too close together,the cooling pools are too close to the reactors,and the need to quickly re-route power and water access to each reactor has been badly compromised by the layout.
They are water-bombing now. Surely this was not seen as a fall-back option in the design and approval of this site.
Are they waiting for all the water trucks to arrive or do they plan on using the police water cannon by its self.
It’s almost 4pm in Japan.
A number of individuals have expressed the sentiment that the design engineers and the industry should have foreseen the 9.0 magnitude earthquake and attendant tsunami. To not have done so equates with sheer stupidity.
If that were the case, wouldn’t the dumbest mistake have been to allow over a million people to live within 10 kilometres of the sea coast. If the planners had seen to limit any human habitation along the coast they would have saved the lives of 10,000-plus people last Friday, perhaps even 25,000.
As it is, we are dealing with an industrial emergency emergency, and that is really what it is, that will be probably be limited to less than 10.
For a comparator, let’s not forget the oil-well blowout in the Gulf last summer cost 11 lives, decimated the local fishing economy, and appeared to threaten the viability of a key global ecosystem.
May I remind the commenters that the question what risks are acceptable to society is not a scientific one, and especially that not all risks of a given probability times impact value are the same?
Nuclear power has an extremely thin but extremely long tail on the impact scale, and the question it boils down to is ‘would you bet the inhabitability of your country on a few diesel generators’. Especially, again, when maintenance of said generators are in the hand of some company that does not care for unlikely events, and of politicians that allow reactors to continue to be operated that aren’t even designed to be safe to earthquakes already observed at the site?
I am not, and this is not a matter of scientific (aka ‘ideal world’) risk analysis.
The spent (aka used) fuel pools are not generating hydrogen. They are not boiling away. They are not empty. UO2 CANNOT burn, it is already fully oxidized. (That is what the O2 part of the compound equation is.) Between 90-95% of the material in a used fuel pool is UO2.
The water level in the pool at unit 4 is significantly lower than normal, which leads to higher radiation levels above the pools than normal. Here are the most recently measured levels – 410 millirem/hr at 300 feet, 8.7 REM/hr at 1000 feet. (Either the elevations or the radiation levels or a combination are off by a bit since they do not fit the usual equations exactly for dose rate attenuation with distance.)
Those levels can be easily explained as simply a matter of a reduced amount of shielding above the still radioactive used fuel. Pools normally contain about 7M of water, the tenth thickness of water is .7 meters. You lose 70 cm of water, the dose rate above the water increases by a factor of 10.
As swimmers know, it is never surprising to see clouds of steam rising from hot water on a cold day. However, even with an increased rate of evaporation, pools take a long time to empty out.
The temperatures in the pool at unit 4 rose from about 24 C to 84 C during the first 4 days after the quake/tsunami. That should give you numerically inclined people the confidence to assert that boiling off of 7 meters of water could not have occurred during the 5th day. (Don’t forget about the latent heat of vaporization.)
All that said, adding even centimeters of water back to a pool is not something that a few helicopter loads can handle. They cannot carry all that much water; the stuff weighs a kilogram per liter.
It takes a 2,000 liters to raise the level of a pool that is 10 meters wide by 20 meters long by a centimeter. A CH-46 medium lift helicopter has a capacity of about 3,180 kg. It would require 63 trips to raise the water level one meter if my guess on fuel pool dimensions is reasonable.
See why they want to bring in fire cannons to top off the pool? This is not desperation, it is simple math and logistics.
[Edited to correct final figures as per above]
@T-Squared: The difference is that the people there choose to live there. If you don’t you can just move up the hill a bit. It was not the decision of the people to live in reach of Daiichi, instead the NPP was built in front of their noses, and it turns out to be quite hard to find any civilized place that is not downwind from some old NPP.
Also, tsunamis and earthquakes are over fast, while we are almost a week into the domino at Daiichi, and there is still no telling how this is going to end. It’s the psychological equivalent of a tsunami wave that is just standing in the sea and no one knows whether it will just recede or instead wash over Tokio.
I don’t see why you wouldn’t go back to life as normal in the 0-20 km and 20-30 km region. There has been no large scale contamination by radioactivity. I haven’t heard the Japanese government recommend anyone in these areas take their KI pills.
They rebuilt Hiroshima and Nagasaki and there must have been measurable traces of radiation after those two blasts above background levels.
Along those lines, why are the Yanks so paranoid about the possibility of a radioactive plume reaching their coastline. There was quite a bit of atmospheric testing of nuclear weapons in the 50’s and 60’s much of theirs. Altogether the radioactive fallout from atmospheric testing was considerable more than from the Chernobyl event and no one was running to the local pharmacy for iodine pills. I also like to think that us kids from the 50’s and 60’s turned out okay; none the worse for wear, so to speak.
@Rod Adams: You’re off by a factor of 100. 200 cubic meters would raise the water by a meter, not a centimeter.
I don’t know where you live, but where I live you don’t allow people to build and live in the flood plain. It is called zoning laws. Why didn’t the municipal planners anticipate a 9.0 magnitude earthquake and attendant 30-foot tsunami and create a no build zone. Hell, I would rather be standing at the end of the day dealing with a psychological equivalent of a tsunami than be dead. Wouldn’t you?
Nick, the problem was caused by the electricity going out, and the diesel generators that run the pumps in that situation getting swamped by the tsunami. These type of reactors need water pumps running at all times to keep them cool.
The site of the plants is not the issue. The problem is that these reactors need active cooling at all times. No electricity, and you have problems.
There are reactor designs where if the coolant pumps are disabled, it’s not a serious problem. We need to start building those kinds of plants.
Passively safe reactors rely
on nature to keep them cool
Rod: do you mean 63 trips to raise by 1m? not 1cm?
If there is no cooling to pool, the water boils potentially exposing the spent fuel. If more water is never added, then you’ll have completely exposed rods to the air. Releasing lots of radiation.
Xirconium coating and steam/water reaact hydrogen is released which can then ignite.
If spent fuel rod starts to burn, it will releasing radioactive gases directly into the environment.
Where did you get this reading and how old is it?
410 millirem/hr at 300 feet, 8.7 REM/hr at 1000 feet
Nikkei – I provided the link to the readings in my comment, but here it is again:
Thanks for asking. I need to revise my math quickly.
10 meters is 1000 cm, not 10,000.
1000cm x 2000cm x 1 cm = 2000 liters, not 200,000 liters.
Still following the situation, but not actively on BNC anymore. Happened across this one, thought it might be of interest. Not that I’d want to interrupt the rampant speculation with actual data, but I’m going to anyway.
Pre-water-drop and post-water-drop dose rates were steady at 3.7 mSv/hour (3,700 uSv/hour) as measured from the main administrative office building (reported as “100 and several tens of meters” from unit 3, which means probably somewhere between about 130-180 m away).
As usual, I wonder about the dose the workers are receiving. At 3.7 mSv/hour, it doesn’t take that many hours to accumulate a substantial dose.
Mike – so why would a worker just sit around in a high dose area. Time, distance, shielding.
We train for this stuff. It is not rocket science.
those measurements are from Reactor 3 not 4.
They’re getting ready to spray with the water cannons
I know, I do the same training. But when that’s the dose rate in the area you’re working in, that’s the dose rate you receive, right?
The answer to the question, “why would a worker just sit around in a high dose area” seems to be, “Because that’s where they have to be to get their job done.”
…Well, that’s the dose rate you receive, minus the effects of PPE such as a breathing apparatus and a hazmat suit. I’m not really sure how much their PPE reduces the dose.
What job do you think they need to get done that prevents them from cycling away from higher dose areas to lower dose areas?
For example, I would suspect that they will set up the water cannons using some kind of stand, turn on the hose and then back away.
I suspect that the people who set up the sea water filling arrangements did their valve line ups or their equipment set ups turned on the flow and then backed out. They most likely went back and checked their handiwork every now and then.
If you want to see what kinds of radiation dose rates it is possible to work around without hurting anyone, I highly recommend reviewing the SL-1 film. You can also listen to The Atomic Show Podcast where I interviewed Ray Haroldsen, a technician who was responsible for picking up the pieces after the team he was a part of performed the BORAX experiments that purposely blew up a small BWR in the Idaho desert in the mid 1950s. We spoke a few years ago, Ray was in perfect health.
Seamus,I’m aware the power supply failed and the back-up generation was flooded. The site of the plant is part of the issue:it needed to be better defended. We have billions of dollars in plant here,a dedicated site,an enormous investment in the need to maintain good will,and a market for power going forward.. Where was the best design,and the back-up to the back-up? And where was the site design calculated for getting quick access through damaged structures and debris? Not at Fukushima… we now have a dead power station,with many years before the site will produce again. Has anyone ever de-commissioned a damaged light water reactor before?
@Rod Adams, my old uncle Joe smoked a pack a day until he was 80, outlived many non-smokers. I don’t think that’s an argument to take up smoking. The fact that you met someone that may have been exposed to high doses of damaging radiation and got through it is not some kind of vindication…..unless you have the ethical and pr skills of a tobacco company.
Are people (some of them) on this site suggesting now that the evacuations ordered by the Japanese governments are simply an emotional/hysterical response to the nuclear accident?
I must have missed where it was suggested that the evacuations were an amotional/hysterical response?
I suppose it depends on the type of work they’re doing, where they’re doing it (e.g., how close to a source), how long it takes, and where they are able to wait. All of those things seem rather difficult to say conclusively, or even speculate on, while sitting in front of my computer half a world away from the event. Indeed, this is the source of my musing on what kind of dose the workers are receiving. I’m not really into this whole “armchair general” thing, I just ask questions (and try to answer them when I can).
@Jim Andrews – Yes, I am saying that the evacuations are an hysterical, dangerous response to a nuclear incident, especially given the extremely hazardous shelter, food and water situation following the earthquake and tsunami.
“The spent (aka used) fuel pools are not generating hydrogen..”
Hydrogen is produced, when the outer shell of the fuel rod (zirconium) reacts with steam/water. It can be produced either in the SF pool or the reactor. There has been massive amounts of hydrogen produced and one of the main issues past couple of days, has been the proper venting the Hydrogen.
After dealing with the multiple hydrogen explosions that occurred in the reactors, how on earth could you miss that?
This link you provided me did not give me the most current reading for reactor 4, it was clearly reactor 3.
Also, why did you change the values from miliverts to milirems?
Reactor 3 was 4.13 miliverts, which you listed as 410 millirems. But then you said the measurement was for Reactor 4.
I remember the last reading Reactor 4 took was roughly 410 milliverts, that would actually be 41,000 millrems. That’s a tremendous amount of radiation put out by exposed spent fuel rods.
410 milliverts and 410 milirems sort of look the same if you’re not paying attention.
Ron, I find this troubling. At worst you’re being dishonest, at best sloppy with your facts.
Either way, it appears you have an agenda .
I’ve recommended this site to a lot of people as reasonable and fact based because the previous few days have been, so thanks for writing it.
However, THIS “guest post” with its speculation that the spent fuel ponds on 1-3 are empty comes out of nowhere and smacks of denialism and it hurts the credibility of the previous posts as well.
As the link Tomas provided above (http://www.jaif.or.jp/english/news_images/pdf/ENGNEWS01_1300322727P.pdf) JAIF is clearly concerned about the water level in the #3 cooling pond. Also, the helicopter drops and currently planned (possibly now underway) water trucks are targeting #3 for this very reason according to the coverage on NHK hours ago.
Also the same pdf along w/ the concern about cesium etc in the steam, strongly suggest that the seawater is being pumped directly to the core.
Can you edit the entry and just remove those ports and/or or put an in-line clarifications ? i REALLY appreciate these entries the past few days, but this one is just highly implausible and hard to defend.