(UPDATE: Saw over at Don Surber’s place–thanks for linking!–the phrase “nothing like this was ever considered”. Let me be clear–Brown’s Ferry, and all nuke plants, absolutely had plans and protocols in place up to and including total loss of pool coolant. The FSAR (Final Safety Analysis Report) examined earthquake danger to the fuel pools and everything else. There was no tsunami impact study, but Google Earth “Athens AL” and see if they were negligent. I’m willing to cut them some slack.
What I meant to convey was there was no worry about it, compared to meltdowns. We had no fear of truly huge earthquakes, and lots of redundancy systems. Sometimes we worked not 30′ away from materials that would strike us dead if not for the water between us. And I remember no worry. END UPDATE)
Everything about the fuel pool situation bothers me. Not to trivialize it; quite the opposite. If a pool is dry then it is certain death for anyone to approach.
The timeline and events of the pool losses are what I most want to see. What was it, two days in before the problem erupted? What the heck happened over that period? My interest in Chernobyl was nothing compared to this. You had no containment building and you set your graphite reactor on fire? Right. Got it. But this?
And what will always bug me most is my insufficient paranoia. Well, it wouldn’t have been paranoia, would it? Brown’s Ferry FSAR slightly annoyed me because it didn’t mention meteorites, if only to say, “we estimate the probably of containment breach from space to be 3,000,000,000,000 to 1 over a 100-year period.” Yet the pools blindsided me.
I had extensive emergency training in meltdowns and remember almost everything about it, decades later. But nothing about the protocols of a pool crisis. We never came close to having one, nor were there jitters about them that I recall.
I did plenty of fuel transfers. When assemblies came from the reactor building to the fuel building, they had to be lifted up in the water. I remember my teletector…
… reading two to three rem per hour as they passed along the canal. We were well aware that only 25′ of water separated us from Death by a Million Curies.
But I don’t remember any worries, just the occasional morbid joke acknowledging what lurked beneath.
As a fresh-faced junior, I was told an apocryphal story while working on the fuel floor. Regular and minute inspections of spent fuel integrity have to be performed. Back then it was a highly difficult and tedious task, owing to the water’s depth and the fuel’s inaccessibility.
The story went that a Japanese engineer set out to improve this process. So he built a long tube with optical lenses for a much less bothersome inspection. Then he tested it, dipping the tube into the water and up to an assembly. The legend goes that he began excitedly saying “Oh yes, I can see very w-” as he fell over, dead.
You didn’t have to believe the story to find its ending plausible. Put your eye to a tube that’s replaced a column of water with a column of air, all the way down…and I’ve no trouble believing that you just committed suicide.
We never forgot the monstrous power of those things. And I’m sure Fukushima didn’t either. So what happened?
Could it just be they assumed they would’t lose power for that long?
Oooh, I don’t think that is something you’re permitted to assume.
If someone did that, they will catch hell and fury.
The pools need active cooling, right, so either you assume you can get power, or….or what? It sounds like they had backups for the on site backup generators, but that too was foiled somehow.
I could imagine having big tanks of backup water that you could pour into a boiling pool, suppose that would buy you time, but if they did I assume those would have been taken out by the explosions that took out the outer contentment.
FWIW, it sounds reactor 4 had been completely unloaded, and thus its pool is under extra stress.
Obviously the quake/tsunami combo knocked things right out. But Japan has experienced both. I’d have expected them to have at least as many backups and contingency plans as we do. Maybe they did. But any plausible scenario, for nukes, has to be planned as the worst-case scenario. A 30′ wave is huge, but by no means worst case for a tsunami.
What surprises me most is that there are no robots with attached firehoses that just… you know… hose the area with water. This is Japan after all. Their robots can dance and speak like humans, walk on two feet and stuff.
GSDF is flying with their CH47s and I really need at least 3 hours of sleep before going to work. I’ll see you guys when I see you.
Several of us are wondering. Just put up a video of one system, but I know I’ve seen a better one…
What is the heat generated in typical 3 month old spent fuel rod? W/cm^3? That number would be important in determining the maximum temperature that these materials can self-heat themselves to.
Ultimately, it will be limited by radiated heat, and air convection. If that limit temperature is low enough, why not just leave the pool alone?
If it’s less than, say, 500C, then the materials will just sit there and be hot (in both senses of the word), right? No need for heroics in that case.
—-
The Japanese appear concerned about this, so that’s probably a pretty good indication that it is important, but still it would be nice to have a model for what these things will and won’t do.
Okay, some back of the envelope calculations
Assuming radiation is your only balancing mechanism:
Assuming 0.5 emissivity constant, of a 50cm cubic block of stuff:
Assuming 5% of 50W/cm^3 left over: Equilibrium temp: 1646 K
Assuming 0.25% of 50W/cm^3 left over: Equilibrium temp: 778 K
Okay, Kelvin, Kelvin…right. Still pretty hot. Just guessing, but I’d lean more toward the higher than the lower, even without natural conservatism.
There’s just so many other contributors beside temperature. Hopefully I’ll remember to come back to this tomorrow morning, with a semi-functioning brain.
I would assume 5% would be more representative of a fuel rod that had just shut down.
I don’t know the half life of residual heat, so I can’t estimate anything reasonable about spent fuel power density.
Okay, LaMarsh seems to give a power ratio of P/P0 = 0.2154^(-0.333/sec*t)
Whoops – wrong model:
y = 1.0023E-02e-2.3049E-07x
x in sec, y is power ratio
So, assuming 40 day old fuel, 0.225 W/cm^3 would be a ballpark estimate.
For 120 day old fuel, 0.0459 W/cm^3 would be ballpark
For a 50cm^3 cube of spent fuel, 0.5 emissivity, the equilibrium temperatures would be 900K, 600K respectively
I’m not usually bad with numbers, but yesterday’s epic run and three hours’ sleep are crippling me. I want to look at these calculations tomorrow and try to get a feel for their possibilities
You wouldn’t want them to just sit there. There’d be corrosions and the heat is enough to drive particles into the air. If the heat load did stabilize, you might could fill it with concrete. Don’t know about the possibility of explosions, though. In theory you could “bag” the floor and constantly filter stuff out of the air into shielded filters.
NHK – defense minister
4.13 mSv/h 1000m alt
87.7 mSv/h 300m alt
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So, I am wondering – radiation *should* limit the temperature of the fuel blocks, even if nothing else does. (I doubt they have it stored as a solid 50cm cubic block anyway – it should be diluted in rods and casing too). The equilibrium temps seem to be somewhere below the melting temp of the fuel cladding. If so, why not let them sit there and not risk anyone’s neck to fill the pools?
Urk. Close to ten rem/hr. at the lower one. I tend to agree with you. But I’m not pretending to know every factor…
>I had extensive emergency training in meltdowns and remember almost everything about it, decades later. But nothing about the protocols of a pool crisis. We never came close to having one, nor were there jitters about them that I recall.
This crisis definitely exposed a weak point, in training and potentially in the design. I bet there was little mention of fuel pools in the massive emergency procedures the employees were following. We’ll certainly learn a lot from the aftermath.
Well, I don’t want to say the Brown’s Ferry training was a weak point. We were far from the New Madrid fault, and anyway the FSAR thoroughly covered earthquakes.
Nor was there wasn’t anything about tsunamis, but I’ll give that one to them. I did always wondered if it was theoretically possible for a tornado to get at the pools. It wasn’t regarded as a likely threat.
Live footage of helicopters dropping water on NHK Japanese news, right now: http://www.ustream.tv/channel/nhk-world-tv
Doesn’t look very effective.
Fuel, water, personnel exposure. We’ll probably use up the last one first, but there’s a lot of chopper pilots. They might decide a tiny fraction of a lot is better than nothing of nothing.
The GSDF operate 54 CH47s. That’s not so many trained crews. The majority of their wings is smaller helos (Bell 205 and MD500, aka Little Birds), most of them can’t carry such a load. The 29 UH-60JAs could become useful, but they’re not Chinooks. There’s a reason the CH47 is still in use in so many countries, despite being that old.
3752 uSv/hr after airdrop, no significant change – NHK reporting.
I assume that is for the plant border.
Also, those altitudes were in ft, not m – misheard.
4.13 mSv/h 1000ft alt
87.7 mSv/h 300ft alt
#3 fuel pool water is almost depleted – needs to be re-filled today. Each helicopter carries a few m^3 of water. I think the trucks would be more effective, but they’d better swap out personnel rapidly.
Those first numbers did seem awfully high, but I’m trying to keep an open mind.
And thinking of the pool as a point source at that altitude, the difference between the two is about an order of magnitude…not at all unusual for seat-of-the-pants calculations.
Geez, use the helicopters to drop some hoses over the side and connect it to a pump somewhere – get people out of there!
That is another thing that has puzzled me–what is stopping them from at least mounting a hose on a crane and sending a gusher through the damaged roof?
Guys, all these ideas about hoses and cranes are good ones; however, let me provide some context. After a earthquake and tsunami of epic proportions, everything in the area is fubar beyond belief. Look at the pictures, there are ocean going ships in the middle of the damn roads? How do you get a crane in there?
Disaster areas are like war zones, where (paraphrasing Clausewitz) even the simplest of things are very difficult.
I did some disaster relief work in New Orleans after Katrina. When the infrastructure (social & physical) is torn asunder getting anything done becomes very difficult. It’s really hard to explain so many years later, but we struggled & struggled just to complete our relief mission. there’s no potable water, fuel, reliable communication, food, and no freakin’ roads! Land marks are all blow away. I had lived there and visited often, but I was useless as a guide because nothing looked anything remotely like it was supposed to. Especially when there was a &#%$ing tuna boat sitting in what was once my duplex’s front yard!
I read reports that they need to bulldoze a path to unit 3, but the problem is getting the dozer to the site.
Those guy are living through hell, and we’re comfortable at home. It’s one thing to analyze what’s happening, but it’s another to second guess without knowing all the facts.
Just my two cents of opinion, and my heartfelt empathy for my technological brethren.
I second Sparkey. I did emergency reponses, but never a really “complex” one. But also some wildly complex multi-agency exercises. For those you’re mentally prepared, knew it was coming, all spoke the same language, and unlike with Sparkey in Katrina everything was still in place.
So of course there were vast complications and mess-ups and screw-ups and missed communications.
The Fukushima disaster is both tremendous and slowly developing. That combination guarantees sideline quarterbacking. You guys have been very good, but we’re still all on the sidelines.
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What is the possibility the earthquake shook the spent fuel rod assemblies to the point where they are close enough to sustain a fission reaction? If that’s what happened, would it help to explain why the water in the cooling pools is being boiled off?
I ask, as it’s my understanding the so-called “spent fuel rods” really aren’t spent. Rather, they’ve fallen below the point where they are able to sustain a fission reaction in a nuclear reactor.
I’d say “extremely unlikely, but theoretically possible”. And excellent thinking.
See, my problem with a sole “boil off” loss of coolant is that it means Fukushima forgot they had spent fuel. As water boiled off the rate would increase, so say that two days is enough for that to happen.
But in the early hours you can have easily made up the water. “But what about the dose rate?”, someone might ask. With the pools still virtually full you wouldn’t have even bhad a Radiation Area (5 mrem/hr., 50 uSv/hr.) in occupied areas. A bucket brigade could have done what choppers and cannons struggle to do now.
I wonder if the fuel pools are the major source of radiation at the plant? Judging by distances, it seems you have 1/r^2-ish falloff – which you would expect with gammas. Radiation levels were in the 10s to 100s of uSv/hr before the fuel pool problems began.
Those were outside dose rates? My first guess would be elevated readings from noble gases
PS – I thought great care was taken to insure that the fuel couldn’t be stacked in ways that could result in criticality? Don’t they have neutron absorbers in there?
That’s a good point. I’ll hazard an opinion. During refueling, the reactor cavity is flooded and linked by canal to the fuel pool. That’s how we bring old fuel out and new fuel in. Putting neutron poisons in the fuel pool risks getting them on the reactor side. You’re rolling the dice over a billion-dollar asset.
So many times when accidents happen, there is what I call a “cascade failure” throughout the system. Usually it entails human error along with equipment malfunction.
(if I remember correctly, didn’t TMI have this combination of problems)
My scenario is highly unlikely (just like a 30′ tsunami wiping out access to a nuclear plant that has just suffered a 9.0 earthquake) but possible.
With everything else going on, why would people at the plant even notice the cooling pool associated with a shutdown nuclear reactor?
I honestly could see the people at this nuclear facility being so overwhelmed with all the system failures they encountered that the cooling pond wasn’t even on their list of problems to deal with.
Btw, I hope I don’t come across as antagonistic. If I do, I apologize in advance.
You don’t come across as hostile.
Yes, TMI operators did the exact wrong thing for awhile, for what seemed to be perfectly good reasons.
If by cooling pond you mean the fuel pools, I can’t accept that checking their water level isn’t on multiple emergency checklists. I can’t understand it.
And let me explain that “complacency” in the main post. We weren’t complacent because we didn’t believe things could go wrong. The complacency was because the water level never changed. You can’t miss the pool when you walk in. If we stepped in and the water was several feet low, we would have noticed. Just as you couldn’t step into a kitchen and not see a grease fire covering the stove.
I understand what you’re saying and thanks again for the response.
The after action report should be depressing and interesting reading.
Thanks for the diplomatic answer.
I have a little more than average knowledge of nuclear power. I stress the “little more” which is I try to be a little cautious when posting to threads such as this.
I was a licensed senior reactor operator a few decades ago and a BWR startup engineer for a decade or two. What came to mind imediately was gate seal failure. If the hyrdogen explosions destroyed the instrument air system, it was only a matter of time before the seals deflated/failed.
Also I have not heard anyone talk about the steam piping to the turbine that penetrates the reactor and the secondary containment. The hydrogen explosions told me that the steams lines to the turbine were not isolated. Now that means the
vessel(s) are open to the turbine building(s)/reactor building(s) and the outside world since the buildings are not designed to withstand a major nuclear incident and from the pictures on the media, the roof of at least one is destroyed.
We have too little information to actually determine what happened, but that is my best educated guess.
You’re absolutely right, we haven’t addressed here and it’s important. There’s so much going on and, as you say, too little info. So we have to imagine all likely scenarios for whatever has our attention at the moment. Meanwhile, other important things pass by.
BWR startup engineer, eh? Man, would that be a bad career move today.
In the interest of spreading more analysis from 8,000 miles away, this is what I suspect happened with the SFP (spent fuel pool) at Unit 4. Although I wrote this for Unit 4, a similar scenario of cascading events can be made for the SFP failure of Unit 3.
My first conjecture is that the quake badly cracked the SFP of unit 4 causing a relatively slow leak. My second conjecture is that the tsunami hampered or disabled much of the monitoring and alarm capability for the less hardened SFP. Over time, while the operators are distracted by bigger alligators at Units 1, 2, & 3 and misled by faulty indicators, the SFP drains, the fuel cladding heats up, and H2 is generated. The first indication of a problem (that captures the operator’s attention) is when the radiation spikes just before the H2 explodes in a supposedly stable reactor in cold shutdown.
Note that I fully accept that verifying the SFP water level is on multiple emergency checklists. However, these guys are not rote monkeys. There is a huge emergency in the other units that is sucking manpower and other resources. Given that Unit 4 is shutdown and cold, it is deemed having weathered the disaster. Thus, a rational decision (aka gamble) is made to shift resources from Unit 4 to work on the others. This decision is made with full knowledge that all steps on the checklists cannot now be performed. Hence, this is how a rational, good faith, decision that relied on common sense (good engineering practice) can work out so badly.
And that, my friends, is the very definition of a very bad day.
Yes, and there was a quote from that interim event summary:
Deviating from normal procedures will (rarely) make you the maverick hero, usually have little total effect…and sometimes make you the goat.
Taking Sparkey’s thought a bit further, what happens to the exposed fuel bundles when the H2 explosion occurs? I assume the rods are spaced precisely in the spent fuel pool in order to avoid a fission reaction. I can’t imagine a big hydrogen explosion above exposed fuel rods helped matters.
We’re all in new ground here, and everything’s speculation. In air, hydrogen will quickly rise, accumulating near a ceiling if it can’t escape further. It’s not going to hang around the rods for long. So for a massive explosion, I’d expect some distance from the rods at the bottom of the pool. Falling debris might disturb things more than the shock wave.
They’re definitely arrayed to minimize criticality as much as is practible. You’re absolutely right that it can’t help. It either doesn’t really change things or it makes them worse.
But I’m pretty sure criticality is a triviality compared to the decay heat. With millions of Curies there, steadily adding a handful more makes no practical difference.
In fact, if they fallen into an unfavorable (but dry) configuration, adding water makes the criticality much worse. The water moderates (slows) the neutrons, which increases fission. And it doesn’t matter. Add water. A million Curies contained is better than a single one let loose.
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