Nuclear Reactors Hit By Earthquake In Japan

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Skipjack
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Nuclear Reactors Hit By Earthquake In Japan

Postby Skipjack » Sat Mar 12, 2011 12:47 pm

So far the information is sparse, but it seems like there was a big explosion at the Fukushima plant.
http://edition.cnn.com/2011/WORLD/asiap ... tml?hpt=T1

I dont think that anything to desastrous has happened, or will happen, but my biggest fear is that it will be emmediately used by the anti nuclear crowd...
Of course the plant is 40 years old and so far nothing really bad has happened despite the biggest earthquake in Japans history...
But still, the anti nuclear people will use it to their own advantage so they can keep selling their inferior energy solutions to the gullible public and stupid governments.

KitemanSA
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Postby KitemanSA » Sat Mar 12, 2011 2:36 pm

Maybe we should be using it to push better solutions like MSRs (a.k.a. LFTRs) designed for a Mw of 10. To do that, the unit would effectively have to be suspended so only the suspension system would need to be site designed and certified.

This is a major opportunity.

Skipjack
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Postby Skipjack » Sat Mar 12, 2011 4:27 pm

I think that the issues are going to make it harder for all nuclear reactors. People are already paranoid when it comes to nuclear energy. This will only make things worse for those of us that are trying to advocate nuclear energy in all its forms...

Giorgio
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Postby Giorgio » Sat Mar 12, 2011 4:39 pm

I fully agree.

I wrote in the other thread that until now there has been no reports of higher than normal radiation levels, so the explosion might not be related to a melt down event.
Let's hope it is like that.

Skipjack
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Postby Skipjack » Sat Mar 12, 2011 4:45 pm

Current information says that the explosion was caused by the pumping system, not by the reactor itself. The containment and the reactor vessel are save.
The general public here of course is already fed false information. I heard people say "They are having a meltdown" (not true). "The reactor exploded" (not true). "They say it is worse than Tshernobyl" (could not be further from the truth).
Just amazing how easy it is to instigate fear in people.

Nik
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Hydrogen explosion.

Postby Nik » Sat Mar 12, 2011 5:08 pm

Latest news is that part of the core has overheated and reacted with cooling water to produce enough hydrogen to blow off the containment building's roof...

I guessed at that from the speed of the shock-wave rather than the refinery's 'roiling' flame, but nice to have it confirmed.

The report confirmed that the reactor had 'scrammed', removing 'China Syndrome' threat, but there was local overheating due to lack of coolant because of power failure to emergency pumps etc. They'd have to add sea-water, which will contaminate the elements and plumbing beyond hope of re-start.

Considering the site was hit by a much bigger quake than design limits, and this was the oldest reactor, they've done better than expected...

Uh, I'd rather they just said, 'Aw, shucks, we had a quench...', but that tech is still a fair way off...

Skipjack
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Postby Skipjack » Sat Mar 12, 2011 5:15 pm

Nik, my information says that the CONTAINMENT VESSEL is in tact. Only the reactor building got damaged. Where is your information coming from that says, the containment vessel got damaged?

dweigert
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Postby dweigert » Sat Mar 12, 2011 5:50 pm

Unfortunately, this will kill non-military fission power, at least for the next fifty years.. We won't be able to educate the general public on safety of the reactor vessels and emergency cooling when Japan is evacuating the area around the plants for ten Km (or more by now). Even worse, it isn't one plant any more, it is three by the latest media count. Not sure what else can be done, but there will be no licenses forthcoming any time soon, as it would be political suicide.

Dan

ladajo
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Postby ladajo » Sat Mar 12, 2011 7:16 pm

The plant <was> and Boiling Water design, about 700Mw if I recall correctly. When they had the emergency shut down, the fast insertion of rods shut off the core. however, the core still contained decay products. These daughters are the heat producers they are trying to coool. Depending on the plants operating history before it dumped, determines the types and amounts of daughters producing Decay Heat.

Typically, the amount of decay heat that will be present in the reactor immediately following shutdown will be roughly 7% of the power level that the reactor operated at prior shutdown. A reactor operating at 3600 MW will produce 252 MW of decay heat immediately after shutdown; this demonstrates the importance of decay heat if no cooling is present. The amount of decay heat produced in the reactor will exponentially decrease as more and more of the radioactive material decays to some stable forms. Decay heat may decrease to about 2% of the pre-shutdown power level within the first hour after shutdown and to 1% within the first day. Decay heat will continue to decrease, but it will decrease at a much slower rate. Decay heat will be significant weeks and even months after the reactor is shut down. Failing to cool the reactor after shutdown results in core heatup and possibly core meltdown (i.e. Three Mile Island 2).


The decay heat power comes mainly from five sources:

Unstable fission products, which decay via α, β-, β+ and γ ray emission to stable isotopes.
Unstable actinides that are formed by successive neutron capture reactions in the uranium and plutonium isotopes present in the fuel.
Fissions induced by delayed neutrons.
Reactions induced by spontaneous fission neutrons.
Structural and cladding materials in the reactor that may have become radioactive.


Check out this link if you want more detail:

http://decay-heat.tripod.com/

The issue the Japanese operators faced was the onset of fuel assy failures. This is evident in several indicators. The plant was hot. It was losing water, and they could not get any more in to makeup or cool. They were forced to vent (more than once) Primary Safety Relief Valves. In this venting, they detected Cesium. That can only be if there was fuel assy failure. The Zircalloy cladding used to make the "Pop Tarts" of the fuel assy matrix had failed somewhere. Probably it melted, or even burned. (http://www.chemicalelements.com/elements/zr.html)
The Zirc and fuel interaction with the cooling water would produce Hydrogen gas. This in turn would be vented into the Containment Building each time they vented. (Bad). The build up of the H2 in the structure is what popped (litterally). It went off as a H2 fuel air blast. Very potent expansion. You can see it the photos that the Containment Building has only its steel re-enforcement internal structure left. All the concrete blocks are blown away. This core has burned and slagged. The melt has already occured. It will come out later.
Another thing that amuses me is the press keeps referring to the "Partial Meltdown" at TMI-2. Sorry guys, but that core was a complete burn. The entire assy ended up as a puddle in the bottom of the Reactor Vessel.

Skipjack
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Postby Skipjack » Sun Mar 13, 2011 1:47 am

Well it seems like everything is under control. The radiation that was released was minimal, nobody died, nobody will die, there was no meltdown.

Maui
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Postby Maui » Sun Mar 13, 2011 2:12 am

Skipjack wrote:Well it seems like everything is under control. The radiation that was released was minimal, nobody died, nobody will die, there was no meltdown.

Hmmm... Kyodo news from Japan is reporting that radiation at the plant is up to 882 micro sievert in a 1 hour period. It may be a little premature to declare things under control, especially since we don't really know what they are and aren't telling us.

EDIT: I was thinking milli-sievert in my head when I read + copy/pasted that. Micro is a little less starting. Still, not sure how you can really write this off as "under control"... especially since they claimed it was under control before the reactor building blew up as well.
Last edited by Maui on Sun Mar 13, 2011 2:24 am, edited 1 time in total.

ladajo
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Postby ladajo » Sun Mar 13, 2011 2:23 am

They lost unit 1 as discussed above.
Looks like they are now risking unit 3 (?). They lost shutdown cooling.
The thing going for it is that they were further along the drop in Decay Heat than Unit 1. But, depending on residual heat, they may still cook up enough to damage cladding as happened in unit 1.
As I called it above, unit 1 cooked off. The two big clues were Cesium and Hydrogen in the venting gasses. Of course, as we know there was enough H2 to subsequenlty ignite and blow away the Containment Building. The two things could only come together with Fuel Assy failure. Ie. the Zircalloy cladding got too hot. Once that happened, it was a lost cause. There is slag in the core for sure.
This second unit that is now in trouble may yet survive. As I understand they are venting. Hopefully they got along enough in the Decay Heat cycle that it will not get hot enough to cook off any of the cladding. The big tell will be H2 and or products like Cesium again.
Latest news has them evacuating for about 15 miles around the plant. 180,000 people on the move.
TMI-2 had a similar failure process as Unit 1. The main difference being that TMI-2 was a PWR and the Japanese plant is a BWR. Really, it is just a difference in where the water boils for steam. And, to be fair a BWR is a little more durable in the core construct. A PWR does not shed heat as well, and the onset of nucleate boiling in the fuel assy flow passages is not a good thing. Mind your Pressurizer son...
Unit 1 is a lost cause. And clean up/entombment is not going to be cheap or pretty. Let us just hope that the Reactor Vessel holds. With the fuel assys losing integrety, it now changes the core geometry. However, as I understand they are now hitting it with a Boron kill via Boric Acid injection. That should do well to contain any further slagging, and limit it to decay product heating, vice fuel burn off with the compromised geometry.

AcesHigh
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"We see the possibility of a meltdown," official s

Postby AcesHigh » Sun Mar 13, 2011 4:41 am

"We see the possibility of a meltdown," official says

http://edition.cnn.com/2011/WORLD/asiap ... ar/?hpt=T1

Tokyo (CNN) -- A meltdown may have occurred at at least one nuclear power reactor in Japan, the country's chief cabinet secretary, Yukio Edano, said Sunday, adding that authorities are concerned about the possibility of another meltdown at a second reactor.
"We do believe that there is a possibility that meltdown has occurred. It is inside the reactor. We can't see. However, we are assuming that a meltdown has occurred," he said about the No. 1 reactor at the Fukushima Daiichi nuclear facility.
"And with reactor No. 3, we are also assuming that the possibility of a meltdown as we carry out measures," Edano said.
Edano's comments confirm an earlier report from an official with Japan's Nuclear and Industrial Safety Agency, who said, "we see the possibility of a meltdown."
"There is a possibility, we see the possibility of a meltdown," said Toshihiro Bannai, director of the apan's Nuclear and Industrial Safety Agency international affairs office, in a telephone interview from the agency's headquarters in Tokyo. "At this point, we have still not confirmed that there is an actual meltdown, but there is a possibility."
A meltdown is a catastrophic failure of the reactor core, with a potential for widespread radiation release.
Though Bannai said engineers have been unable to get close enough to the core to know what's going on, he based his conclusion on the fact that they measured radioactive isotopes in the air Saturday night.
"What we have seen is only the slight indication from a monitoring post of cesium and iodine," he said. Since then, he said, plant officials have injected sea water and boron into the plant in an effort to cool its nuclear fuel and stop any reactions.
"We have some confidence, to some extent, to make the situation to be stable status," he said. "We actually have very good confidence that we will resolve this."

A state of emergency has been declared for the plant and two other reactors at the same complex, which holds a total of six reactors, he said. Three are in a safe, shut-down state, he said. "The other two still have some cooling systems, but not enough capacity."
But Ichiro Fujisaki, Japan's ambassador to the United States, told CNN's Wolf Blitzer in Washington that he did not know of any evidence of a meltdown.
"We are working on it," he said. "We are getting information every hour on this issue."
And Japan's chief cabinet secretary, Yukio Edano, raised another possible issue. "Some of the readings in the measurement equipment were not accurate," he said without elaboration.
He noted that since the inside of the pressure vessel has been filled with sea water, radiation levels in the area have not risen, implying that the problem was not worsening.
The detection of a cesium isotope indicates that the nuclear fuel cladding has failed, said Ken Bergeron, a physicist and former scientist at Sandia National Laboratories.
"Now we have to hope that the containment building will succeed in preventing major amounts of radioactivity" from escaping, he said.
As of Sunday morning, winds in northeast Japan were blowing out to sea at 5-15 mph, said CNN Meteorologist Taylor Ward. But they were expected to reverse direction by Monday night, he said. The Daiichi plant is located about 160 miles (260 kilometers) north of Tokyo.
"We're in uncharted territory," Bergeron said. "We're in the land where probability says we shouldn't be and we're hoping that all the barriers to release radioactivity will not fail."
"The bottom line is that we just don't know what's going to happen in the next couple of days and, frankly, neither do the people who run the system," said Dr. Ira Helfand, a member of the board of Physicians for Social Responsibility.
What we do know, he added, is that Japan's nuclear facilities are "way out of whack."
Cesium 137 can remain dangerous for 600 years and is associated with a number of cancers, he said.

The use of sea water and boron was described as a "Hail Mary pass" by Robert Alvarez, senior scholar at the Institute for Policy Studies focused on energy policies and a former senior policy adviser to the U.S. secretary of energy.
"My understanding is that the situation has become desperate enough that they apparently don't have the capability to deliver fresh water or plain water to cool the reactor and stabilize it and now, in an act of desperation, are having to resort to diverting and using sea water," he said.
Boron, a chemical element, was being added to the water "to sort of stymie other potential nuclear reactions," he said.
Boron has the ability to absorb neutrons, the sub-atomic particles that occur in the nucleus of all atoms. In a nuclear reactor, it is essential that just the right number of neutrons are present. Too many neutrons can cause a fission reaction to get out of control. Too few neutrons and a fission reaction stops.
But, he acknowledged Sunday to reporters in a conference call, "There's a lot that we don't know about what's happening with these reactors. It's trying to piece together a picture where you're dealing with just a few pieces of the puzzle."
Another expert said enough was known to conclude that the nuclear events in Japan rank high on the list of similar incidents. "If this accident stops right now, it will already be one of the three worst accidents we have ever had at a nuclear power plant in the history of nuclear power," said Joseph Cirincione, an expert on nuclear materials and president of the U.S.-based Ploughshares Fund, a firm involved in security and peace funding.
He said only the 1979 partial meltdown of a reactor core at the Three Mile Island nuclear plant in Pennsylvania and the 1986 Chernobyl disaster in the Soviet Union were worse.
If the effort to cool the nuclear fuel inside the reactor fails completely -- a scenario experts who have spoken to CNN say is unlikely -- the resulting release of radiation could cause enormous damage to the plant or release radiation into the atmosphere or water. That could lead to widespread cancer and other health problems, experts say.
The problems reported at two other reactors in the complex stemmed from a similar cause: an insufficient amount of water being pumped into the cores in an attempt to keep them cool.
To ease the pressure inside reactor No. 3, air containing "some minimal radioactive material" was being vented from its containment vessel, Edano said, expressing confidence in the outcome. "We believe that we can stabilize the situation of the reactor," he said.
An evacuation order affected more than 200,000 people living within 20 kilometers of the plants, officials said.
Some experts said the flow of information from the agency has not been fast enough.
But IAEA Director General Yukiya Amano defended the Japanese response. "I know the Japanese authorities are working their hardest to gather the necessary details and ensure safety under difficult and constantly evolving circumstances," he said in a statement.
Japanese authorities have classified the event at Fukushima Daiichi Unit 1 as a level 4 "accident with local consequences" on the International Nuclear and Radiological Event Scale intended to communicate to the public the significance of radiation-linked events. The scale runs from 0 to 7, with the latter being classified as a major accident.
On Saturday night, three patients at a hospital tested positive for radiation exposure, according to the Japanese public broadcasting station NHK, citing a statement from Fukushima Prefecture.
The three had been randomly selected from a group of 90 hospital workers and patients who were outside the hospital -- about three kilometers from the Daiichi plant -- awaiting evacuation at the time of the explosion. The patients had already been hospitalized at the medical facility prior to Friday's quake.
While the three showed signed of exposure, "no abnormal health conditions have been observed," NHK quoted the prefecture as saying.
Meanwhile, two experts from the U.S. Nuclear Regulatory Commission with expertise in boiling-water nuclear reactors like those affected by the disaster have been sent to Japan as part of a U.S. Agency for International Development (USAID) team.
The NRC's Maryland-based headquarters operations center has been operating round the clock since the beginning of the emergency.
The Japanese government was preparing to distribute iodine tablets to residents, the IAEA said. Iodine is commonly recommended to block the uptake by the thyroid gland of radioactive iodine.
The problems at the Daiichi plant began Friday when the 8.9-magnitude quake struck off the eastern shore of Miyagi Prefecture. The quake forced the automatic shutdown of the plant's nuclear reactors and knocked out the main cooling system, according to the country's nuclear agency.
A tsunami resulting from the quake then washed over the site, knocking out backup generators that pumped water into the reactor containment unit to keep the nuclear fuel cool, according to the agency.
As pressure and temperatures rose inside the reactors at the Daiichi and Daini plants, authorities ordered the release of valves at the plants -- a move that experts said was likely done to release growing pressure inside as high temperatures caused water to boil and produce excess steam.
As crews were working to pump additional water into the reactor containment unit to lower the temperature, the pumping system failed, Edano said, causing the explosion that injured four workers and bringing down the walls of the building containing the reactor.
The International Atomic Energy Agency, citing Japanese authorities, said the explosion occurred outside the plant's primary containment vessel and that the vessel remained intact. The explosion injured four workers, it said.
Nine residents near the site of the explosion got radioactive material on their clothing and were being decontaminated, Bergeron said. "Now, we're trying to make sure they have not been internally exposed to radioactive material."
He described their exposure as "not hazardous to health."
The team then reverted to the plan to flood the reactor with sea water, which Edano said would lower the temperature to acceptable levels. That work began Saturday night and was expected to take two days, Edano said.
Japan is heavily dependent on nuclear power, with 54 plants and another eight slated for construction, said Aileen Mioko Smith of Green Action, an environmental group. All are located in "very seismic" areas, she said.

ladajo
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Postby ladajo » Sun Mar 13, 2011 7:06 am

In this case, I hate being right.

Skipjack
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Postby Skipjack » Sun Mar 13, 2011 10:31 am

Ok, so please correct me if I am wrong, but a meltdown would not mean another Tschernobyl.
If the reactor melted down, it would form a puddle on the bottom of the reactor vessel. If it still kept getting hotter, it would melt through the reactor vessel into the containment vessel, which is built to deal with a situation like that.
So a meltdown would be an economic catastrophy, but not harming the environment or human life. That is what I understand. Please anyone correct me if I am wrong.


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