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TEPCO: Nearly All Nuclear Fuel Melted At Fukushima No. 3 Reactor
mdsolar (1045926) writes "Almost all of the nuclear fuel in the No. 3 reactor of the Fukushima No. 1 nuclear power plant melted within days of the March 11, 2011, disaster, according to a new estimate by Tokyo Electric Power Co. TEPCO originally estimated that about 60 percent of the nuclear fuel melted at the reactor. But the latest estimate released on Aug. 6 revealed that the fuel started to melt about six hours earlier than previously thought. TEPCO said most of the melted fuel likely dropped to the bottom of the containment unit from the pressure vessel after the disaster set off by the Great East Japan Earthquake and tsunami."
This article really doesn't explain why this finding matters. TEPCO themselves said they do not know how this will effect the decommissioning process for the reactor, if at all. The only thing that seems to be different is that they now believe some of the fuel is still inside the pressure vessel, and it's not clear that they didn't already know that to begin with. It doesn't seem like anything will really change until TEPCO actually sends people in to get a look at it.
considering that the recently passed 'state secrets' law in japan effectively gags anyone from talking about fukushima in an honest way, the fact that this is being released at all probably means it's just to warm up the public for the real shoe to drop..
oh, and in case you don't know the law... here it is.
In case of a nuclear accident, the industry will always downplay and deny everything that is not perfectly obvious. Has always been, and probably will always be. This is the main reason I do not trust nuclear power that is run for profit.
Cooling down a molten core to the point where it solidfies reduces emissions quite enormously, especially when the containment (such as a Mark I BWR containment), wasn't designed to stay fully sealed after a meltdown. Otherwise, when the hot molten core just sits there, more aerosols (maiinly Caesium) are created and eventually scattered in the environment.
When this containment was designed, back in 1958-1962, it was sufficient to ensure that there would be no catastrophic numbers of casualties after any potential reactor accident. (Something they did remarkably well, given their limited experience.) It was not designed to prevent contamination of the environment during accidents involving a core meltdown, unlike more modern designs or pressure water reactor containments, that just so happened to be large enough to stay sealed with a molten core inside, even though this wasn't a specifically set design goal back when the earliest of those were designed.
All of this could have been prevented, if there had been filtered containment vents that could have kept the containment otherwise sealed.
It could have been worse except for one determined engineer, Yanosuke Hirai, who insisted on a higher seawall for the Onagawa plant. A good article can be found at http://www.oregonlive.com/opin.... I have a quote on my wall from Tatsuji Oshima, one of his proteges. "Corporate ethics and compliance may be similar, but their cores are different. From the perspective of corporate social responsibility, we cannot say that there is no need to question a company's actions just because they are not a crime under the law."
The containment buildings were supposed to contain everything, but they were damaged by hydrogen explosions. The hydrogen gas was supposed to have been vented, but the battery powered venting system stopped working after the disaster. Some consideration was given to venting into the atmosphere, but it was decided not to. A bad choice in hindsight, but they thought that their emergency cooling measures would work.
I don't know much about Japan... but in the US most plant upgrades have been denied permits by the feds because of work done by organizations like Greenpeace. If I didn't know better, I'd think they were intentionally trying to cause accidents to further their anti-nuclear agenda.
Seriously, the mistake that everybody is making is stopping new ultra-safe reactors from replacing these old second gen reactors. Companies like Transatomic can make it so that the reactor can not fail.
I prefer the "u" in honour as it seems to be missing these days.
Isn't that what they said about these reactors?
A large amount of radioactive material was released into the ocean where it will remain in the food chain for decades. Approximately 100,000 people are unable to return to their homes and a large area of land in a country where land is scarce and precious is uninhabitable. But...that's just the short term. Long term: Japan will have to deal with electric power shortages for years until their power generation can be rebuilt with new technology. Hundreds of billions of dollars will have to be spent over the next 20 years to decommission the mess at Fukushima and attempt to decontaminate the surrounding downwind land. All of this was avoidable...but happened because the resident village idiots were able to prevent realistic plans from being implemented for electric power generation at Fukushima. The Onagawa power station was closer to the earthquake epicenter and yet it survived undamaged thanks to a losing battle by the resident village idiots to ensure that it was built according to their idiot plans. They lost at Onagawa but 'won' at Fukushima. Idiots who said...why spend a lot of money on a bigger seawall at Fukushima? Idiot engineers at GE who said 'there's no need for a failsafe design for something that will never happen,' and idiots who say 'what's the big deal about a meltdown?'
I was about 100 km from Fukushima when it happened, the reason they didn't flood the reactors with seawater right away was that the president of TEPCO, who before the earthquake was famous for being a cost cutter, wanted to save the reactor because if they flooded it it would never produce power again. He only reluctantly agreed to have it flooded after it was clear not doing so would result in an even bigger catastrophe. The dude should be hung for what he did.
Monstar L
That is incorrect. ... the surrounding power pillions failed, shutting off the plant from external power.
The mag 9.5 quake was 450 miles away.
Ar the place of the reactor the quake was not even mag 6
The plant itself was damaged by far enough to be unable to produce its own power and cool itself.
And then the Tsunami hi tits emergency power.
So, claiming the 'plant survived' a '.... how was your words? Ah: "This reactor survived one of the worst natural disasters ever recorded." '
No, it certainly did not. It is smoldering in its ashes.
Not only was it NOT EVEN HIT, by the 'worst natural disaster', but it got destroyed by its wake (1 thousand times weaker than the a actual disaster/quake)!! Or actually as wake implies by the water of the tsunami.
Even if there had not been a tsunami, the plant was destroyed. What is so fucking difficult in accepting that? Sure, the emergency diesel power likely had prevented a 'disaster'.
But the plant never would have gone online again.
Claiming 'it survived the biggest catastrophe in mankind' is bullshit, and is a disrespect to the dead of Nagasaki and Hiroshima, or the simple earth quakes of the last 100 years.
Google/Wikipedia for it. The official death toll is never even close to the 'unofficial' one. And all those quakes certainly qualify your brain dead definition of 'biggest disasters naturally recorded' ... Fukushima was no such thing yet. It will be in 30 or 50 years when the radiation death will start piling up.
Cost free eBook I read (by iBook/Kobo/Amazon/ObookO/Gutenberg etc.): "The Green Odyssey" by Philip Jose Farmer.
Nuclear power plants in the United States with operating licenses undergo a continuous process of upgrade and modification, will continue to do so throughout their operating life, and in some cases continue to receive upgrades after retirement if in safestore mode. Over the last 20 years enormous effort has gone into simplifying and rationalizing the designs of the post-TMI era, standardizing operations, and improving backup systems. A current challenge is replacing the 1960s/70s era control and instrumentation systems which, while rugged and highly reliable, cannot be maintained as there are no longer sources of spare parts, with modern C&I systems. All while avoiding the fragility and instability of COTS electronics.
It is true that the finance world on Wall Street has made it difficult to begin new from-scratch nuclear plants in the US (although a few are currently underway) due to serious doubts about ROI during the financed lifetime, but that's another issue entirely.
sPh
There were poor decisions and communication between various designers and operators. Take for example, the situation at reactor 1. After the generators started, the emergency reactor cooling condensers should have switched on to provide cooling. However, operators had found that they were very effective and being unfamiliar with their use were concerned that they would cause thermal shock to the reactor. Not familiar with the operation of this system, the operators decided to manually switch off the condenser system to arrest the temperature drop. They would then switch them on again manually as reactor temp rose again. This worked fine, until the generators failed, removing control and monitoring from this system.
Operators at emergency control, in a separate quake-proof building asked for confirmation of operation, but the control room could not give it. So,workers went out to inspect the reactor building for steam rising from the condenser stacks. They reported some steam rising, and it was assumed that the system was operational. However, the condenser system had never been used or tested since the plants were constructed 40 years ago. No one knew how they worked and how quickly they could cool the reactor, no one knew how much steam was produced during operation. It turns out that the workers sent out for reconnaissance saw only faint steam trickling from the stacks, consistent with the system having been switched off for many minutes, but still containing some residual heat. Had the system been switched on, the clouds of steam would have been so profuse and so dense that the it would have been impossible even to see the reactor building, let alone identify the condenser stacks.
On the assumption that the system was operational, other attempts to provide emergency cooling were suspended or delayed. A steam/battery powered pump system was available to deliver fresh water to the reactor, but without a heatsink (condenser) available, the reactor temperature rapidly rose and so did reactor pressure, eventually overcoming the maximum discharge pressure of the coolant injection system. After a few hours, the UPS controlling this system discharged and it also failed.
After 24 hours, reactor pressure unexpectedly dropped. Operators realised that this might permit external coolant injection and fire engines were called in. There was a huge delay, as the fire engines were unable to reach the site due to debris and some had been destroyed by the tsunami. Subsequent investigation showed that despite massive coolant injection, coolant did not rise in the reactor. The cause was thought to be due to damage to the reactor vessel or a pipe. In retrospect, it probably indicated damage to the reactor following meltdown of the fuel.
There were also design oversights in the emergency systems for the plants. One of the final backup schemes for reactor cooling was the ability to connect fire engines to the reactor to inject coolant. It subsequently became apparent that in units 2 and 3, this water didn't reach the reactor, and collected in a condenser unit instead. This was always going to happen, due to the way in which the water pipes were connected. There was a pump connected between the storage tank and the injection flow pipe. Under normal injection conditions, the pump would have been running, and any additional water from the fire engine would likely have gone towards the reactor, and this presumably was the assumption under which the water injection protocol was developed. However, under power failure conditions, the pump was unpowered. Due to the design of the pump - a rotodynamic (impeller) pump. this pump would have offered little or no resistance to reverse flow when unpowered.
So you think all of the radioactive crap that got dumped into the ocean is going to be magically dispersed evenly throughout the globes oceans?
Or more likely it's going to bugger up seafood local to japan for decades to come.
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