Sunday, June 19, 2011
Fukushima Daiichi Update
Decontamination efforts at the Fukushima No. 1 plant were halted Saturday after a filter expected to remove the radioactive element cesium for several weeks exceeded capacity in just five hours. Oil and sludge in the water contained much more radiation than expected, said Junichi Matsumoto, a spokesman for the utility.TEPCO claims this is only a temporary setback, but we will see.They had projected the filter would last a month, so they would certainly have expected at least two weeks of operational use. Perhaps they could put a primary filter in front of the intake piping to filter sediment and oil, but that would have to be cleaned or replaced all the time, and the high levels of radioactivity would make it dangerous.
Work on a self-contained cooling system has been suspended while the company seeks a solution, Matsumoto said at a media briefing in Tokyo Sunday.
There are two interlocking problems. TEPCO wants to create a significantly closed system for the water used as coolant, and this radioactive water is going to start overflowing, further contaminating the site and the ocean, where it will end up.
Also TEPCO installed an air filtering system on reactor 2 using the same technique used at reactor 1. They ran it more than a week to cut airborne radioactivity in the reactor building of 2, and TEPCO has now opened the doors. The reason they are opening the doors is try to cut humidity levels in the building. Originally they thought the humidity was caused by the spent fuel pool, but after cooling the pool down, the humidity inside the building remained high, so now they think it is coming from the suppression vessel (torus), which is believed to have been ruptured by an explosion in the first week. It only took three days to filter the air on 1, so the span of time involved for reactor 2 was higher than expected.
So in the next couple of days TEPCO will find out if it can get into the reactor 2 building and work.
According to the original estimates, TEPCO only has a bit over a week to begin filtering the coolant water and recirculating it through the reactor, or the water is likely to overflow.
This is the current roadmap to achieve "cold shutdown" at this nuclear site. They are running into difficulties. The water purification system was supposed to have the capacity to partially decontaminate 1,200 tons of water a day. Obviously they did not make that goal.
They are also finding further difficulties with the plans to cool down the spent fuel pool on reactor 4.
PS: Some interesting detail is emerging on the March 12th situation. Also see this post at Atomic Power Review.
So, let's see. Choice 1: Use industrial dehumidifiers and collect the condensate and treat it as the hazardous material that it is, all while not letting even more contamination escape. Or choice 2: Just dump it all into the atmosphere.
From the link:
"Tepco said that it opened the doors of reactor 2 at 8:50 p.m. to lower the humidity inside so people can work there."
Yes, because if I were a TEPCO worker I wouldn't be concerned about radiation -- but I'd damn sure want to stay the hell away from humidity! (?)
"The utility plans to open the doors slowly and gradually in an operation that will last until around 4 a.m. Monday to avoid stirring up dust containing toxic materials."
Better hope there's no wind!
Boy, I can feel my confidence in TEPCO increasing by the sievert, um, second.
They really cannot work in there with the heat and humidity as it now is. In places they couldn't even see. A robot sent in couldn't even photograph the gauges due to fogged up lenses.
Also they did run the air filtering system for more than a week to drop rad levels, which is why they are now able to open the doors.
Now the issue is what the workers can accomplish inside, but at least being able to set up more reliable monitoring is necessary. They have a plan to sort of dig up the flooring around the torus (suppression vessel) and patch the rupture with a type of grout compounds. In the short term, TEPCO has had to undertake some minimal additional environmental contamination risks to avoid much greater environmental contamination.
If the basement/trench water overflows, it is a very serious issue.
TEPCO estimates, making me feel all warm and fuzzy. Just like when they said this was a "3 mile island"-like event.
"Also they did run the air filtering system for more than a week"
Then they had more than a week during which they could have been running dehumidifiers.
"TEPCO has had to undertake some minimal additional environmental contamination risks"
No, by not running dehumidifiers concurrently with the filtering system, they *CHOSE* "additional environmental contamination".
They've done it. They aren't seeing much of an impact on radiation levels at the plant boundaries.
Foo - Hahahaha. There is no way they could effectively establish a dehumidification system without first filtering the air! Steam is constantly billowing out, and trying to dehumidify the air through one airlock would be quite futile, and in any case couldn't be started until they filtered the air to drop rad levels, because you'd need very big coils and you would generate a lot of contaminated water dripping off those coils.
The benefit of filtering the air is that it was a closed system. They established an airlock at the doors, sucked the air out into the filtration system, and then returned the air to the plant. This minimized ambient radiation.
To dehumidify the air, they would have had to set up multiple air intakes inside the plant, run piping throughout the plant, establish a controlled AC system outside the plant, seal it, and have a mechanism to inject the contaminated water generated into one of the special containers.
Now, if they could have spent the time inside the plant to set all that up, they wouldn't need to open the doors at all!
Tokyo Electric Power Company opened the entrance early Monday morning after it had filtered radioactive substances from the air inside the building.
The utility says the humidity levels near the entrance and at other points has been lowered to around 60%.
But it says the reading near a cargo entrance, that utility plans to open on Monday afternoon, was still nearly 90%.
It hopes workers will be able to enter the building to begin calibrating a water level gauge for the reactor and other tasks.
The utility says radiation teadings were between 5 and 27 millisieverts per hour inside, but no significant change in radiation levels has been observed outside the plant.
The No.2 reactor is believed to have released more radioactive substances than the other reactors at the plant after an explosion apparently damaged its suppression chamber.
So no, they would not have been able to dehumidify the air through the one portal.
At this point they don't even have accurate water level readings on the reactor. They have got to get in there ASAP.
The firm calculated that the level of background radiation around the plant after opening the doors would be 0.0014 microsieverts per hour. The annualized figure would be far below the permissible limit of one millisievert a year.
A TEPCO official told reporters that the door-opening has almost no impact on the nearby environment so far.
If you want to freak out about .00014 MICROsieverts an hour for a few days, go ahead. I refuse to join you, because otherwise I'd have to update my will every time the dentist wanted X-rays.
The whole situation is dire. This is not relevant.
We are approaching a drastic boundary at which the EXTREMELY contaminated water in the basements is not going to be contained. I suggest you both sweat that, because it needs to be sweated.
I write a post containing the info that a water filter that was supposed to last a month was too contaminated for operation after 5 hours, and you guys freak over .0014 MICROsieverts an hour?
The filter was at 4.7 milliSieverts an hour. A milliSievert is 1000 microSieverts. Don't you realize what that level of contamination implies?
"The benefit of filtering the air is that it was a closed system."
Until they opened the door...
And in less than 5 minutes of thought I came up with a closed system dehumidification process:
"To dehumidify the air, they would have had to set up multiple air intakes inside the plant, run piping throughout the plant"
Not so. They could have turned the entire structure into a dehumidifier. You just use the existing filter port to fill the place with near-freezing cold air. During that process relative humidity would remain at 100% but absolute humidity would have dropped. Then when they want to go in, just reverse the process -- start cranking up the heat (staying within what's bearable for human workers) and relative humidity will drop. The cooling process could be bolstered if desired/required using external cooling applied directly to large areas of the structure's exterior. (You could do the same with heating, but you would want to ensure you were mainly heating air and not the pooled water.)
Of course, if I were actually in charge of a nuclear reactor I would spend more than 5 minutes on it and run it by a few experienced engineers.
"The utility says radiation teadings were between 5 and 27 millisieverts per hour inside, but no significant change in radiation levels has been observed outside the plant."
Yes, because the warm wet air they are releasing is going pretty much straight up. I would be very surprised if they are even measuring the radioactivity in that air column at all. (You don't measure something when you don't want to know how bad it is.)
"We are approaching a drastic boundary at which the EXTREMELY contaminated water in the basements is not going to be contained. I suggest you both sweat that, because it needs to be sweated."
So, would it be fair to say you are freaking out about this water?
"If you want to freak out about .00014 MICROsieverts an hour for a few days, go ahead."
First, nice mischaracterization. Second, nice deceptive number as "background radiation around the plant" has nothing to do with the level of radiation in the air being released (as I explained above the air will travel upwards and TEPCO won't be measuring that air).
I don't think you do -- I think there's some physics and math you are ignoring.
from here: http://search.japantimes.co.jp/cgi-bin/nn20110528x2.html
"So far, the basements of the turbine buildings of all six reactors have been flooded by about 100,000 tons of radioactive water. That's enough to fill roughly 40 Olympic-size swimming pools."
so 40 pools / 6 reactors = 6 2/3 pools/reactor. (I have no idea how evenly the water is distributed. If you want to use more accurate numbers feel free.)
from here: http://en.wikipedia.org/wiki/Olympic-size_swimming_pool
One such pool is at least 50*25*2 = 2500 cubic meters.
2500 * 6 2/3 = 16,667 cubic meters of water per reactor.
How big is the active area of the filter?
If the filter active area is 1 meter by 1 meter by 5 cm thick, then it is 0.05 cubic meters. (Again, I don't have real numbers for this, but this seemed like a reasonable guesstimation.)
That would mean that when comparing pre-filtered radiation density in the original water with post-filtered radiation density in the filter, you have a multiplication factor of 16,667/0.05 = 333,333x.
So what a 4.7 millisieverts filter reading is really saying is that they managed to reduce the radioactivity of the water by about 0.014 MICRO sieverts. So that tells you that *before* filtering the water would have measured at least 0.014 microsieverts. It doesn't really tell you much of anything about what the water would measure *after* the filter had been spent.
What the "filter fiasco" does imply is that I was right when I said TEPCO's estimates are not to be trusted. They thought the filter would last for a month and it lasted 5 hours -- so their estimate was off by a factor of 144x. But that's cool -- just keep letting them play with nuclear reactors -- what could go wrong? :-)
Eventually I think they will have to build a whole system. Once they have the shroud in place, they'll have an easier time of it because the air flow to the outside will be largely curtailed. They are building the first shroud destined for reactor 1 now in the area.
They are submitting all these plans to the regulators, so it is not just a matter of trusting TEPCO. No one has ever done this; you are going to run into implementation problems.
I'll be honest - I didn't ever think this was going to work, but that was because I thought there were practical limitations as to how much you can possibly drop contamination levels of water this radioactive. If you then reinject highly radioactive water into the reactors, you are going to eventually end up with water even MORE radioactive, surely?
But just blaming TEPCO is useless. From the moment they started putting seawater into the reactors, which everyone agrees they had to do, we have been outside of experience and into the realm of theory and experiment.
There are multiple filters involved, so I don't think that calculation is simple.
The measurement of air concentrations at the plant on the 21st is here. You can compare it with the readings on the 18th.
They have not done recent testing of the radioactivity levels in the basement water, but at the end of May the levels were very high indeed. Note the measurements are per cubic centimeter:
Tokyo Electric Power Company says a water sample taken from the reactor building's basement on Friday contained 2.5 million becquerels of radioactive cesium-134 per cubic centimeter. It also detected 2.9 million becquerels of cesium-137 and 30,000 becquerels of iodine-131.
The levels are almost the same as those already measured in contaminated water in the basement of the Number 2 reactor's turbine building.
They are testing plant air, dust, and seawater at intake points, but the basement water is so highly contaminated that surface levels are at the extreme zone, with multiple reports of 1,000 milliS/hr and up.
At reactor 2, these levels were first reported inside the building near the end of March in a puddle. Nothing seems to have improved since then. Link.
My plan did not call for direct changes to the air pressure. (I suspect you misread "fill the place with near-freezing cold air" as "add air" when it meant "cool air".) I am assuming that right now at their one airlock they have an air path with an inlet, an outlet, a filter, and a air mover (e.g., fan) of some sort. To that path (preferably on a lower portion of it because it's going to be dumping water into the structure) you insert a large heatsink with lots of surface area. Most of the heatsink is sealed in with the rest (the filter, fan, structure interior) but the back of the heatsink will outside that seal and be attached to a heat pipe of some sort (e.g., solid copper blocks, forced anti-freeze convection system, whatever) which is then attached to a (temperature controlled of course) heat pump of some sort which resides entirely outside of the structure and outside of the sealed area. Technically changing the air temp will change its pressure, but we're talking a very small range of temps (like 40F to 80F or less) so the pressure change would be very small. (Note that the sun rising and falling is going to cause temp/pressure changes within the structure too, though those will be even smaller.)
"Once they have the shroud in place"
If I were running the show I probably would have plastered that building with a spray that expands and solidifies (and can be removed by solvent if access to any point is needed later). You could still do the shroud thing later for extra safety, but the spray on stuff could make the place air-tight in a matter of hours.
"They are submitting all these plans to the regulators, so it is not just a matter of trusting TEPCO."
Fine. I distrust the whole lot. (How is this any different than the BP incident? Regulators were completely ineffective there as well.)
"No one has ever done this; you are going to run into implementation problems."
That just seems like a cop out argument. In both my jobs and my hobbies I have lost count of how many things I have (successfully) done that no one has ever done before. You just need a sound understanding of the problem domain and a solid realistic engineering approach (and a willingness to do what needs to be done). My experience has been that dealing with manager types who don't know jack but insist on running the show (and who may favor a known approach that will fail over a novel approach that will work), and dealing with inter-team competition driven not by finding the best solution but instead by job security concerns, are both much more difficult to deal with and prone to causing failure than the actual job of solving whatever real-world problem is at hand.
But if you want to rephrase that as "TEPCO will run into implementation problems" then I would not object to that statement. But that has more to do with TEPCO than the problem.
Every single word you and I write is "useless" in the sense that neither is likely to accomplish anything, so I'm not really seeing your point here. If your point is that TEPCO is blameless, then I strongly disagree.
"into the realm of theory and experiment."
More cop out talk. Engineering does not get tossed out the window just because you are doing something you haven't done before. If you want to make a new type of bridge and you WANT it to collapse, go ahead can call in academics and scientists to do theory and experiment. On the other hand if you want it to stand, call in an engineer. (But it has to be an engineer who is familiar with the limits of the simplifications they use. There are sadly lots of engineers who will use a formula in a completely inappropriate situation because they don't realize it doesn't apply in the given case.)
"There are multiple filters involved, so I don't think that calculation is simple."
Multiple filters does not really increase the complexity. The superposition principle (http://en.wikipedia.org/wiki/Superposition_principle) holds in this case, so you can do the calculations independently for each filter to see how much each removed, and add up all of the results to determine the total removed.
"At reactor 2, these levels were first reported inside the building near the end of March in a puddle. Nothing seems to have improved since then. [... ] At 2, the surface levels last shown are 1 sievert/hr."
Just for kicks: If the water is at 1 sievert and each filter used removes 0.014 microsieverts, then it will only take 71,428,571 filters to remove the radiation from the water (at least to the filter's ability to do so). At 5 hours a pop, that's 40,741 years. It gets even more absurd when you add into the calculation that TEPCO expected the filter to last a month (i.e., to remove 0.014 microsieverts every month instead of every 5 hours). At that rate it would take 5,866,823 years.
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