japan tsunami

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Re: japan tsunami

Postby fuzzygeek » Sat Mar 12, 2011 6:10 pm

I'm glad to hear that. We still haven't heard from some of my father-in-law's branch of the family, but suspect they're just stranded with all the train services down; they're in the Tokyo region.
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Re: japan tsunami

Postby mew » Sun Mar 13, 2011 1:20 am

It's great to hear that all your family is okay!

fuzzygeek wrote:I'm glad to hear that. We still haven't heard from some of my father-in-law's branch of the family, but suspect they're just stranded with all the train services down; they're in the Tokyo region.

Hopefully they are fine. All the in-Japan people I know are from around Tokyo and it seems like they didn't get it nearly as bad/dangerous as other parts.
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Re: japan tsunami

Postby Lightbeard » Sun Mar 13, 2011 8:22 pm

A list of people in the Japanese game/manga/anime industry that have confirmed they are still alive and fine

http://www.animenewsnetwork.com/news/20 ... fter-quake

I don't think the guy that does Naruto is on the list but he's probably fine.

I haven't heard reports of any deaths of Japanese entertainers such as musicians and every wrestler I know of touring in Japan has been confirmed as fine.
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Re: japan tsunami

Postby Aubade » Sun Mar 13, 2011 10:39 pm

Lightbeard wrote:A list of people in the Japanese game/manga/anime industry that have confirmed they are still alive and fine

http://www.animenewsnetwork.com/news/20 ... fter-quake

I don't think the guy that does Naruto is on the list but he's probably fine.

I haven't heard reports of any deaths of Japanese entertainers such as musicians and every wrestler I know of touring in Japan has been confirmed as fine.



I don't mean to be that guy, but if the guy who does naruto doesn't check in, I will be more than happy.
I hope all of the rest of them are okay.


Disclaimer: I don't wish something like this disaster on ANYONE. I truly hope he's okay, I just dislike naruto.
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Re: japan tsunami

Postby Sabindeus » Mon Mar 14, 2011 12:02 pm

Aubade wrote:
Lightbeard wrote:A list of people in the Japanese game/manga/anime industry that have confirmed they are still alive and fine

http://www.animenewsnetwork.com/news/20 ... fter-quake

I don't think the guy that does Naruto is on the list but he's probably fine.

I haven't heard reports of any deaths of Japanese entertainers such as musicians and every wrestler I know of touring in Japan has been confirmed as fine.



I don't mean to be that guy, but if the guy who does naruto doesn't check in, I will be more than happy.
I hope all of the rest of them are okay.


Disclaimer: I don't wish something like this disaster on ANYONE. I truly hope he's okay, I just dislike naruto.


clearly you are not allowed to dislike Naruto if there is an earthquake in japan.

Everyone is now morally required to go buy manga to support our eastern brethren in this time of crisis.
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Re: japan tsunami

Postby Hrobertgar » Mon Mar 14, 2011 12:40 pm

Someone asked about how a nuclear power plant can be low or even without power:

As far as how a (nuclea) power plant can be without power to run things like pumps, it is the nature of a nuclear power system.

Nuclear reactors run by controlling the neutron flux in the core, as it is neutrons that stimulate Fission reactions to heat up the working fluid. The control rods work by selectively 'eating' neutrons. Boron is typically used as it is widely availabe, non-radioactive, and is 'fairly' efficient at 'eating' neutrons. As the control rods are lowered into the core, more Boron is available to 'eat' the neutrons and thus fewer neutrons are available for fission. In the event of an emergency shutdown, or scram (scram is a technical term, I cannot recall what it stands for exactly), the control rods are usually released, and dropped all the way into the core. This rapidly decreases the neutrons available for Fission, until Fission reactins basically stop.

However, Fission produces many isotopes, that are radioactive (generating a lot of heat), and decay with various half lives. One of the products of these decay chains is an isotope of Xenon (Xe), which is on the order of a thousand or so times as good at 'eating' neutrons as Boron is. This Xenon isotope has a half life of something like 12 hours. This Xenon isotope IS produced during normal operation of a reactor, and it does eat some neutrons, however the control rods can be raised to account for this, and keep the reactor going. Once a reactor is shutdown however, this isotope can build up to the point that the reactor CANNOT generate a sufficient neutron flux to restart until such time as the Xenon decays. Apparently the tsunami wiped out all the auxiliary power generation that would normally run the pumps and cooling system to keep the core cool during this period.

So, having the emergency shutdown, basically meant that unless restarted right away, the reactor is offline for several days. Meanwhile, the core is still quite hot, and still going thru radioactive decay and heating up the fluid (water in this case and for most non-soviet reactors). Left by itself, the water can boil, and vapor is much less effective at cooling than water is. Furthermore, this vapor can drastically increase pressure inside the containment vessel, which is why they need to vent it. If they cannot get enough water in to cool the core, then some of the metal parts of the core can melt, which is generally very bad.

The Soviet reactor in Chernobyl used graphite as a moderator (if I recall correctly) and did not have a containment vessel like most non-soviet designs do. Thus the Chernobyl reactor was at greater risk of quickly going bad, which did happen. The risk of such a situation in the Japanese reactor is much less. But still, having the core melt is bad.
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Re: japan tsunami

Postby bldavis » Mon Mar 14, 2011 12:55 pm

Chernobyl did use graphite, which is flammable and just added to the fire, esp after oxygen was introduced into the core (after the meltdown happened, they dumped water into the core, which split into hydrogen and oxygen)

without the pumps and everything to keep the reactor core cool, the core could conintue to heat up
iirc the operators dumnped seawater into teh core to cool it off, but the cores were hot enough to boil off the water into steam.

another of the by-products of the water on the core is the same thing that happened in Chernobyl
Hydrogen is HIGHLY flamable, think the Hindenburg, but requires oxygen and a heat source in order to burn
what is water made of? Hydrogen and Oxygen
without the containment shell, we could have very well seen another Chernobyl, but the reactors had containment shells, and were shut down, or in the process of shutting down, so the core temp was already falling.

Chernobyl was caused by a runaway reaction in which several failsafes were bypassed/turned off by the controllers, which should have never happened.
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Re: japan tsunami

Postby Arnock » Mon Mar 14, 2011 1:04 pm

Forgive my ignorance in these matters, but, from my understanding, nuclear power plants operate by using the heat of the reaction to heat water and run a steam turbine.


If the reactor is overheating, can't they use that heat to generate the power to run the cooling systems?
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Re: japan tsunami

Postby Aurelie » Mon Mar 14, 2011 1:17 pm

I read this explanation this morning, it's pretty clear and put the media's sensationalism into perspective...


What is going on here?

In the aftermath of the recent earthquake and tsunami in Japan, two nuclear power stations on the east coast of Japan have been experiencing problems. They are the Fukushima Daiichi ("daiichi" means "number one") and Fukushima Daini ("number two") sites, operated by the Tokyo Electric Power Company (or TEPCO). Site one has six reactors, and site two has four. The problematic reactors are #1, #2, and #3 at site one, which are the oldest of the ten and were due to be decommissioned this year.

In short, the earthquake combined with the tsunami have impaired the cooling systems at these reactors, which has made it difficult for TEPCO to shut them down completely. Reactor #1 is now considered safe after crew flooded the reactor with sea water. Reactor #3 was starting this process as this was originally written (6:00PM CST/11:00PM GST on March 13th). Site crew began preparing to add sea water to reactor #2 around 7:30AM GMT on March 14th, if a cooling procedure does not work.

The four reactors at site two did not have their systems impaired and have shut down normally.

Can this cause a nuclear explosion?

No. It is physically impossible for a nuclear power station to explode like a nuclear weapon.

Nuclear bombs work by causing a supercritical fission reaction in a very small space in an unbelievably small amount of time. They do this by using precisely-designed explosive charges to combine two subcritical masses of nuclear material so quickly that they bypass the critical stage and go directly to supercritical, and with enough force that the resulting supercritical mass cannot melt or blow itself apart before all of the material is fissioned.

Current nuclear power plants are designed around subcritical masses of radioactive material, which are manipulated into achieving sustained fission through the use of neutron moderators. The heat from this fission is used to convert water to steam, which drives electric generator turbines. (This is a drastic simplification.) They are not capable of achieving supercritical levels; the nuclear fuel would melt before this could occur, and a supercritical reaction is required for an explosion to occur.

Making a nuclear bomb is very difficult, and it is completely impossible for a nuclear reactor to accidentally become a bomb. Secondary systems, like cooling or turbines, can explode due to pressure and stress problems, but these are not nuclear explosions.

Is this a meltdown?

Technically, yes, but not in the way that most people think.

The term "meltdown" is not used within the nuclear industry, because it is insufficiently specific. The popular image of a meltdown is when a nuclear reactor's fuel core goes out of control and melts its way out of the containment facility. This has not happened and is unlikely to happen.

What has happened in reactor #1 and #3 is a "partial fuel melt". This means that the fuel core has suffered damage from heat but is still largely intact. No fuel has escaped containment. Core #2 may have experienced heat damage as well, but the details are not known yet. It is confirmed that reactor #2's containment has not been breached.

How did this happen? Aren't there safety systems?

When the earthquakes in Japan occurred on March 11th, all ten reactor cores "scrammed", which means that their control rods were inserted automatically. This shut down the active fission process, and the cores have remained shut down since then.

The problem is that even a scrammed reactor core generates "decay heat", which requires cooling. When the tsunami arrived shortly after the earthquake, it damaged the external power generators that the sites used to power their cooling systems. This meant that while the cores were shut down, they were still boiling off the water used as coolant.

This caused two further problems. First, the steam caused pressure to build up within the containment vessel. Second, once the water level subsided, parts of the fuel rods were exposed to air, causing the heat to build up more quickly, leading to core damage from the heat.

What are they doing about it?

From the very beginning, TEPCO has had the option to flood the reactor chambers with sea water, which would end the problems immediately. Unfortunately, this also destroys the reactors permanently. Doing so would not only cost TEPCO (and Japanese taxpayers) billions of dollars, but it would make that reactor unavailable for generating electricity during a nationwide disaster. The sea water method is a "last resort" in this sense, but it has always been an option.

To avoid this, TEPCO first took steps to bring the cooling systems back online and to reduce the pressure on the inside of the containment vessel. This involved bringing in external portable generators, repairing damaged systems, and venting steam and gases from inside the containment vessel. These methods worked for reactor #2 at site one, prior to complications; reactors four through six were shut down before for inspection before the earthquake hit.

In the end, TEPCO decided to avoid further risk and flooded reactor #1 with sea water. It is now considered safely under control. Reactor #3 is currently undergoing this process, and reactor #2 may undergo it if a venting procedure fails.

The four reactors at site two did not have their external power damaged by the tsunami, and are therefore operating normally, albeit in a post-scram shutdown state. They have not required any venting, and reactor #3 is already in full cold shutdown.

Is a "China Syndrome" meltdown possible?

No, any fuel melt situation at Fukushima will be limited, because the fuel is physically incapable of having a runaway fission reaction. This is due to their light water reactor design.

In a light water reactor, water is used as both a coolant for the fuel core and as a "neutron moderator". What a neutron moderator does is very technical (you can watch a lecture which includes this information here), but in short, when the neutron moderator is removed, the fission reaction will stop.

An LWR design limits the damage caused by a meltdown, because if all of the coolant is boiled away, the fission reaction will not keep going, because the coolant is also the moderator. The core will then only generate decay heat, which while dangerous and strong enough to melt the core, is not nearly as dangerous as an active fission reaction.

The containment vessel at Fukushima should be strong enough to resist breaching even during a decay heat meltdown. The amount of energy that could be produced by decay heat is easily calculated, and it is possible to design a container that will resist it. If it is not, and the core melts its way through the bottom of the vessel, it will end up in a large concrete barrier below the reactor. It is nearly impossible that a fuel melt caused by decay heat would penetrate this barrier. A containment vessel failure like this would result in a massive cleanup job but no leakage of nuclear material into the outside environment.

This is all moot, however, as flooding the reactor with sea water will prevent a fuel melt from progressing. TEPCO has already done this to reactor #1, and is in the process of doing it to #3. If any of the other reactors begin misbehaving, the sea water option will be available for those as well.

What was this about an explosion?

One of the byproducts of reactors like the ones at Fukushima is hydrogen. Normally this gas is vented and burned slowly. Due to the nature of the accident, the vented hydrogen gas was not properly burned as it was released. This led to a build up of hydrogen gas inside the reactor #1 building, but outside the containment vessel.

This gas ignited, causing the top of the largely cosmetic external shell to be blown off. This shell was made of sheet metal on a steel frame and did not require a great deal of force to be destroyed. The reactor itself was not damaged in this explosion, and there were only four minor injuries. This was a conventional chemical reaction and not a nuclear explosion.

You see what happened in the photo of the reactor housing. Note that other than losing the sheet metal covering on the top, the reactor building is intact. No containment breach has occurred.

At about 2:30AM GMT on March 14th, a similar explosion occurred at the reactor #3 building. This explosion was not unexpected, as TEPCO had warned that one might occur. The damage is still being assessed but it has been announced that the containment vessel was not breached and that the sea water process is continuing.

Around 7:30AM GMT on March 14th, it was announced that the explosion at reactor #2 has damaged the already limping cooling systems of reactor #2. It may also receive the sea water treatment if they are unable to use a venting procedure to restart the cooling systems.

Is there radiation leakage?

The radiation levels outside the plant are higher than usual due to the release of radioactive steam. These levels will go down and return to their normal levels, as no fuel has escaped containment.

For perspective, note that charts detailing detrimental radiation exposure start at 1 Gy, equivalent to 1 Sv; the radiation outside the problematic Fukushima reactors is being measured in micro-Svs per hour. The highest reported levels outside the Fukushima reactors has been around 1000 to 1500 micro-Svs per hour. This means that one would have to stay in this area for four to six weeks, 24 hours a day, without protection in order to experience the lowest level of radiation poisoning, which while unpleasant is not normally fatal. And this level will not stay where it is.

Also note the chart of normal radiation exposure levels from things like medical x-rays and airline flights.

There have also been very minor releases of radioactive reactor byproducts like iodine and cesium along with the steam. This material is less radioactive than the typical output of coal power plants. It is significant mainly as an indicator of the state of the reactor core.

I read that there's a plume of radioactive material heading across the Pacific.

In its current state, the steam blowing east from Japan across the pacific is less dangerous than living in Denver for a year. If it makes it across the ocean, it will be almost undetectable by the time it arrives, and completely harmless as the dangerous elements in the steam will have decayed by then.

What's this about fuel rods being exposed to the air?

When the coolant levels inside the reactor get low enough, the tops of the fuel rods will be exposed to the air inside the containment vessel. They have not been exposed to the external atmosphere and the containment vessels are all intact.

Can this end up like Chernobyl?

No, it cannot. for several reasons.

* Chernobyl used graphite as a neutron moderator and water as a coolant. For complicated reasons, this meant that as the coolant heated up and converted to steam, the fission reaction intensified, converting even more water to steam, leading to a feedback effect. The Fukushima reactors use water as both the coolant and the neutron moderator, which means that as the water heats up and converts to steam, the reaction slows down instead. (The effect of the conversion of water coolant to steam on the performance of a nuclear reactor is known as the "void coefficient", and can be either positive or negative.)
* Chernobyl was designed so that as the nuclear fuel heated up, the fission reaction intensified, heating the core even further, causing another feedback effect. In the Fukushima reactors, the fission reaction slows down as the fuel heats up. (The effect of heating of the nuclear fuel on the performance of a nuclear reactor is known as the "temperature coefficient", and can also be positive or negative.)
* Chernobyl's graphite moderator was flammable, and when the reactor exploded, the radioactive graphite burned and ended up in the atmosphere. The Fukushima reactors use water as a neutron moderator, which is obviously not flammable.

Note that while Chernobyl used light water as a coolant (as distinct from heavy water), it was not a "light water reactor". The term LWR refers strictly to reactors that use light water for both cooling and neutron moderation.

The news said this was the worst nuclear power accident since Chernobyl, though.

It's the only nuclear power plant accident of its type since Chernobyl. It's easy to be the worst in a sample size of one.

Is this like Three Mile Island?

There are similarities. The final effect on the world is likely to be similar: no deaths, minimal external contamination, and a tremendous PR disaster for the nuclear industry due to bad reporting by the media.

How can I keep up with developments?

The western media has been very bad about reporting this event, due to a combination of sensationalist reporting, ignorance, and the use of inexact or unexplained terminology.

One of the safe sources of information is the TEPCO site, which has been posting press releases on a regular basis. Unfortunately, this site is often unresponsive due to the immense traffic it is receiving.

The important thing to remember is that most of the "experts" appearing on the news are engaging in speculation. Very few of them are restricting themselves to what they can be sure about, and those that are have often been misrepresented.

Reading:

* Timeline and data sheets for the incident by the Nuclear Energy Institute : (nei.org)
* The International Atomic Energy Agency is providing regular announcements
* Wikipedia on light water reactors and nuclear weapon design
* The United States Nuclear Regulatory Commission's Boiling Water Reactor (BWR) Systems manual - the Fukushima reactors are BWRs, a subset of LWRs (nrc.gov)
* Tokyo Electric Power Company site with press releases - currently hard to reach due to traffic (tepco.co.jp/en)

Video:

* "Physics for Future Presidents" lecture ten, on nuclear weapons and nuclear reactors (Youtube search)
* Footage of the hydrogen explosion at reactor #1

Last edited by Aurelie on Mon Mar 14, 2011 1:23 pm, edited 1 time in total.
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Re: japan tsunami

Postby razul » Mon Mar 14, 2011 1:22 pm

I'm guessing that the pumps that move the stream through the heat exchangers is disabled. If I'm not mistaken that is actually the cause of the overheating in the first place. The power generating steam also acts as the coolant.
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Re: japan tsunami

Postby bldavis » Mon Mar 14, 2011 1:51 pm

Arnock wrote:Forgive my ignorance in these matters, but, from my understanding, nuclear power plants operate by using the heat of the reaction to heat water and run a steam turbine.


If the reactor is overheating, can't they use that heat to generate the power to run the cooling systems?


this is just from research i did 2 yrs ago, but iirc, the reactors have 2 seperate systems
one for the water coolant (becomes radioactive through runnig through the core itself) and then the turbine loop

the coolant goes through a heat exchanger, but the radioactive water never touches the turbine and is in a closed loop of reactor->heat exchanger -> reactor

so no it cannot use its coolant to generate power.
plus without the power, the pumps dont work that get the coolant to flow
no coolant flow = no cooling of the core = melt down possible, if not definate
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Re: japan tsunami

Postby Masumi » Tue Mar 15, 2011 2:34 pm

with the problems they are having over in japan father convinced some of our relatives to send our cousins to stay with us he payed for the tickets, three of my cousins will be staying with us. we will be picking them up from LAX tonight, I haven't seen them since I was little
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Re: japan tsunami

Postby Lightbeard » Tue Mar 15, 2011 6:28 pm

Masumi wrote:with the problems they are having over in japan father convinced some of our relatives to send our cousins to stay with us he payed for the tickets, three of my cousins will be staying with us. we will be picking them up from LAX tonight, I haven't seen them since I was little


I thought all flights were canceled for a while?
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Re: japan tsunami

Postby Masumi » Tue Mar 15, 2011 8:10 pm

Lightbeard wrote:
Masumi wrote:with the problems they are having over in japan father convinced some of our relatives to send our cousins to stay with us he payed for the tickets, three of my cousins will be staying with us. we will be picking them up from LAX tonight, I haven't seen them since I was little


I thought all flights were canceled for a while?


Edit: yes actually you seem to be right, we been waiting on LAX for a while now, haven't heard from our cousins

Edit of edit: no they are just delayed, American Airline still transporting, they are just delaying them.

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went back to were we bought the tickets, you can't get the 15 anymore for obvious reasons but 16 are still open.
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Re: japan tsunami

Postby Rachmaninoff » Wed Mar 16, 2011 6:26 am

Aurelie wrote:I read that there's a plume of radioactive material heading across the Pacific.

In its current state, the steam blowing east from Japan across the pacific is less dangerous than living in Denver for a year.

wat?

otherwise good info, excellent explanation
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