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Fukushima Update 04/06/2011
PermaLinkFirst off, my apologies for being off-line for several days. Sometimes you just hit writer’s block.
Stunningly Good Photos
Back on March 30th, TEPCO hired an sUAV (small Unmanned Aerial Vehicle) company to fly a small radio-controlled and camera equipped model plane over the site. The photos that they have released are stunning. They can be seen here. Note that full res versions of these photos can be downloaded from here.
The quality is amazing. To someone like me who knows that type of plant well, they reveal many very interesting facts.
Probably the foremost thing is just how violent the hydrogen explosions were. I had written earlier that I anticipated total core destruction of Units 1 and 2 and severe damage in the Unit 4 spent fuel pit. These photos confirm that. To make that much hydrogen would require essentially the whole fuel load’s Zircalloy cladding to have “burned” in the water-Zirc reaction. There is now no doubt that this happened. Fortunately the engineered safeguards and defense-in-depth design philosophies worked as intended and contained the vast majority of radioactive materials within the respective containment buildings.
I’ll be studying these photos in detail in the days to come and comment on specific items.
Leaking Water
The big news over the past few days has been the “hot” water that has been leaking from (presumably) #2’s reactor building and into the sea. The latest information that I have is that the water is coming from the #2 reactor building sump, is flowing along a damaged pipeline, through some gravel fill and into a cable chase that is in turn cracked, allowing the water to flow into the storm drains. The water is quite hot, around 1R/hr at the surface in the cable chase, but dilution with sea water has reduced the public risk to nothing.
As of earlier today, the utility has stopped the leak by pumping a large amount of water glass (sodium silicate) into the gravels. The water glass reacts with CO2 in the air to form a glass-like solid that in this case, cements the gravel together, forming an impenetrable barrier. Let’s hope that the barrier is strong enough to hold up until they can drain the reactor building sump. It should be.
The Great Water Shuffle
The other item in the news is the shuffling of water around the plant to make room to store the very hot water in the turbine building basements and hopefully later, the water in the reactor building sumps. To make room for the very hot water, TEPCO is discharging about 3 million gallons (11,500 metric tons) of slightly contaminated water into the sea. This water is coming from the Rad Waste Treatment system hold-up tank and is only mildly contaminated. I haven’t been able to find specific numbers yet for dissolved activity but based on my experience at other plants, this water is just barely contaminated. Again, the sea should rapidly dilute and disperse the water.
Once these tanks are empty, they will be used to contain the hotter water now stored in the turbine condensers. Once empty, the condensers will be used to receive the even hotter water from the turbine building sumps.
The idea is to get the hottest water into the safety containment. The condenser is designed to handle radioactive water during normal operation so it’s a logical choice. These are all temporary measures designed to get the hottest water contained so that people can work in the basement of the turbine building. That’s where many of the cooling pumps and related apparatus are located.
Reactor Statuses
Based on data released in their daily reports from here and here, what I suspected and predicted earlier is the case. Reactors 1 and 2’s cores are likely still dry despite the water being pumped in at a modest rate. The water is probably being displaced by a gas bubble above the core. TMI had that problem but was able to sweep away the bubble when the Residual Heat Removal (RHR) system pumps were engaged. In this instance, those pumps are probably flooded with seawater and so won’t get any use anytime soon.
Unit 3’s core is probably at least partially covered with water. The data is ambiguous.
Since almost a month has gone by since the earthquake, the cores have cooled significantly. Fission product radioactive decay takes care of that. I-131 has been through about 3 half-lives since the quake so it is rapidly fading as a source term. Getting water back over the core would allow the Cs-137 and the remaining iodine to combine, stopping the atmospheric releases.
The newer fuel in the Unit 4 spent fuel pit is probably also completely destroyed and is probably dry. The concrete pumper truck is a good try but from its positioning in the above referenced photos, I doubt that it’s doing a whole lot of good. I would expect to see a lot more steam emission if water were getting to fuel.
Getting water over that spent fuel is probably the most important task they face right now because it is outside of any sort of containment and thus is the source of most of the atmospheric release of radioactive material.
I figure that they’ll bring in a robot to take a look around so that they can assess the actual conditions in the pit. Then they’ll work on some sort of barrier to go between the fuel and the atmosphere. No idea what that barrier might be. I’d be taking a serious look at entombing the stuff in concrete and then building a new roof over the pit to keep out rainwater.
Media Caterwauling
As predictable as sunrise, I suppose. Since I cut myself off from mass media several years ago (no TV, newspapers, etc), I’m only getting slight nibbles of the mass media’s behavior based on links friends send me but that’s more than enough to make me puke. Take this article, for example. This is typical of Pravda, er, the NY Times but it still makes me sick to read articles like this.
Of course, they don’t post the actual document so that we can see and judge for ourselves. They “interpret”. And of course, they go to that highly impartial and unbiased source for nuclear information, the Union of Concerned Scientists. Never met a nuke they didn’t hate.
So let’s see what they’re actually saying. First off, the document is from the NRC, an agency which has never seen a licensee action it couldn’t criticize. So expect the document to be the most pessimistic, worst case possible.
Keeping that in mind, the first issue that they bring up is the filling of the containment structure with water. A flooded containment is a design basis event that the containment is designed to handle. The only mild concern is that regarding the unknown state of the concrete support structures. They’re probably OK but in any event, getting the core covered again is the priority so the utility logically weighs the risks and chooses to pump water. Good decision.
The next “issue” is the possibility of a hydrogen explosion in the containment. About the only place in the containment that has enough free volume to matter is the torus and if they’re filling the containment, the air in the torus is either displaced or trapped. So the risk of another massive blast like those before is non-existent. Still, there’s a possibility of some hydrogen build-up from the radiation-induced breakdown (radioloysis) of water into hydrogen and oxygen so the utility is doing the logical thing. They’re re-inerting the containments with nitrogen.
Nitrogen inertment of the containment is the standard operating condition for all reactors in the post-TMI era. So they’re just putting things back to normal. The Nu Yawk Ministry of Propaganda seems to think this is a big deal. It’s not.
Finally, they make a big deal out of the fact that some small amount of spent fuel was blown out of the spent fuel pits by the hydrogen explosions. Duh. I would have been shocked had that not happened. The only thing of note here is that the quantity was so small that it could be covered with a little earth (bulldozed) to shield it from the workers.
The rest of the article and undoubtedly the document they base it on is just nattering from uninvolved third parties (the NRC people) as they look over the shoulders of the people gettin’ er done. Disgusting.
More later.
John
Posted by neonjohn on April 6th, 2011 under Energy, Nuclear
April 8th, 2011 at 1:07 am
Nice update. Appreciate the insight.
The turbine buildings are those long, shorter structures just oceanside from the reactors? I also wonder where they had the plant’s emergency power (that was knocked out) installed?
April 8th, 2011 at 9:36 am
Russell,
Correct on the turbine building. It’s the long, lower structure with the large hole in the roof opposite Unit 2.
I’m not yet sure where the diesels are on that site. That’s one thing that varies from plant to plant in the GE design.
One thing that I did find yesterday in the process of completing my document collection is that the diesel fuel tanks were swept away by the tsunami. That info is here in the sequence-of-events document for the early events:
http://www.jaif.or.jp/english/aij/member/2011/2011-03-18c.pdf
Notice that the Sequence of Events doesn’t list diesel generator flooding as an event. I now kinda doubt that they were flooded. Diesel generators are generally located in waterproof vaults. Even if they did momentarily flood, losing the fuel tanks means that they could not be restarted.
John
April 10th, 2011 at 8:30 am
I see. Thank you. I was wondering why the emergency diesels apparently were knocked out. I had read some of your Usenet postings so had thought that the generators would be pretty heavily protected. Having no fuel sounds more likely though I would have thought they’d be pretty well protected, but on second thought I guess the design presumed that there might be flooding but not a huge tsunami washing through the plant. There probably was something more else I’d have thought they’d try to reinstall fuel tanks in some fashion to get the generators going if they and the circuitry were still serviceable.