Meltdown Likely Under Way At Japan Nuclear Reactor

[jfchandler]

That was yesterday....

But seriously, it also may have been the journalist exercising a bit of license...

The Daiichi reactors have containment vessels/structures. I guess Chernobyl did not.

TEPCO probably, correctly, said they could face the prospect of a meltdown... And then the writer went on to describe their idea of what a meltdown would mean.

TEPCO said the problem could develop into a critical ''meltdown'' situation, in which fuel rods melt and are destroyed, emitting massive amounts of radioactive materials into the air.

What happened to "there is no chance of another Chernobyl"?

Edited March 15, 2011 by jfchandler

[Moonrakers]

What is 'spent' nuclear fuel?

If it is 'spent', how is it still so dangerous?

[SurfRider]

.

I know this isn't the "what if" suggestion forum, but from what I've read, the back-up cooling systems, including the back-up generators, kicked in after the quake and were keeping the core cooling situation stable. It was only after the Tsunami arrived sometime later that the back-up generators were wiped out and the current doomsday scenario began.

Since the main reactor containment buildings survived both the quake and Tsunami, it seems that *IF* the back-up generators powering the emergency cooling system had been located on the roof of the containment structures - where the Tsunami could presumably not get to them, the whole disaster would have been avoided.

A simple design flaw? If so, could the hundreds of similar nuke-plants around the world be retrofitted to avoid the next big disaster?

Maybe including Indian Point, only 35 miles from New York City?

http://www.nbcnewyor...-117983419.html

.

[katana]

“Why I am not worried about Japan’s nuclear reactors.”

...

The above post on the blog of Nuclear Science and Engineering at MIT explains in great detail and in terms understandable by non-scientists what has been happening a Fukushima and what measures have been taken and why. Worth reading, even though it is quite long.

Thanks Maestro: Although I havent read this one I have been reading other experts playing down the severity of the situation on line with comparisons to radiation levels with x rays, two hours flights and so on. Let's just say I would feel a whole lot better if these experts would go stand on the front lines of the the disaster area while reporting why they are not worried.

The comparisons of the released radioactivity to x-rays or flights is a bit disingenuous since the radioactive particles released from the power plant that are ingested into the body and come into intimate contact with cells are far more dangerous than if you receive alpha/beta/gamma radiation from an outside source.

[jfchandler]

Sen Lieberman the other day said the U.S. has 23 or so reactors now based on the Japanese design.. What he meant by that, exactly, I'm not sure... I'm guessing he meant Boiling Water Reactors, which is the Japanese type, I gather...

What that means about backup generator placement, I don't know... But of course, not all of them...though certainly some...are going to be located along sea coasts vs. inland.

Maybe they can build the future ones the same way Thais build their old style houses... up on stilts...

Since the main reactor containment buildings survived both the quake and Tsunami, it seems that *IF* the back-up generators powering the emergency cooling system had been located on the roof of the containment structures - where the Tsunami could presumably not get to them, the whole disaster would have been avoided.

[jfchandler]

What is 'spent' nuclear fuel?

If it is 'spent', how is it still so dangerous?

My two cents on this would be... spent is the term used in the industry to mean when particular fuel rods can no longer be used to produce energy in a reactor...for whatever reason...

But even once they're removed from a reactor, they have a pretty long radiation life thereafter.... Hence the big problem with how to store and dispose of these highly radioactive materials after they're not longer used in a reactor.

It's not like driving a car where when you run out of gas, the engine just quits... More like the Energizer bunny... they keep going and going and going...

[jfchandler]

IAEA on what's normal radiation:

Background on Radiation

A person´s radiation exposure due to all natural sources amounts on average to about 2.4 millisievert (mSv) per year.

A sievert (Sv) is a unit of effective dose of radiation. Depending on geographical location, this figure can vary by several hundred percent.

Since one sievert is a large quantity, radiation doses are typically expressed in millisievert (mSv) or microsievert (µSv), which is one-thousandth or one millionth of a sievert.

For example, one chest X-ray will give about 0.2 mSv of radiation dose.

JFC note - the peak reading at the Daiichi plant Tuesday morning was 400 milli-sieverts per hour.

http://www.iaea.org/...sh/radlife.html

Edited March 15, 2011 by jfchandler

[Moonrakers]

What is 'spent' nuclear fuel?

If it is 'spent', how is it still so dangerous?

My two cents on this would be... spent is the term used in the industry to mean when particular fuel rods can no longer be used to produce energy in a reactor...for whatever reason...

But even once they're removed from a reactor, they have a pretty long radiation life thereafter.... Hence the big problem with how to store and dispose of these highly radioactive materials after they're not longer used in a reactor.

It's not like driving a car where when you run out of gas, the engine just quits... More like the Energizer bunny... they keep going and going and going...

OK

Sounds wasteful to me if there is still so much energy remaining in the rods. But they are smarter men than I running these things (I hope).

[jfchandler]

Chernobyl clean-up expert slams Japan, IAEA

(Reuters) - Greed in the nuclear industry and corporate influence over the U.N. watchdog for atomic energy may doom Japan to a spreading nuclear disaster, one of the men brought in to clean up Chernobyl said on Tuesday.

Slamming the Japanese response at Fukushima, Russian nuclear accident specialist Iouli Andreev accused corporations and the United Nations' International Atomic Energy Agency (IAEA) of willfully ignoring lessons from the world's worst nuclear accident 25 years ago to protect the industry's expansion.

"After Chernobyl all the force of the nuclear industry was directed to hide this event, for not creating damage to their reputation. The Chernobyl experience was not studied properly because who has money for studying? Only industry.

"But industry doesn't like it," he said in an interview in Vienna where the former director of the Soviet Spetsatom clean-up agency now teaches and advises on nuclear safety. Austria's environment ministry has used him as an adviser.

MORE: http://www.reuters.c...E72E5MV20110315

Edited March 15, 2011 by jfchandler

[rizla]

What is 'spent' nuclear fuel?

If it is 'spent', how is it still so dangerous?

My two cents on this would be... spent is the term used in the industry to mean when particular fuel rods can no longer be used to produce energy in a reactor...for whatever reason...

But even once they're removed from a reactor, they have a pretty long radiation life thereafter.... Hence the big problem with how to store and dispose of these highly radioactive materials after they're not longer used in a reactor.

It's not like driving a car where when you run out of gas, the engine just quits... More like the Energizer bunny... they keep going and going and going...

AND the spent (used fuel cans) contain a mixture of uranium and plutonium, the latter used in war heads......................but the rods need to be de-canned first in a processing plant...(plutonium DEADLY STUFF)

[jfchandler]

I misspoke on this a bit, even though my basic answer was correct in that the Japanese have not changed their level rating.

The Japanese original rating and now for Fukushima was Level 4, not Level 5. Level 4 meaning accident with local consequences...

Here's what I found re the latest on this from ABC News in Australia, posted tonight.

Japan's nuclear safety agency is maintaining its level four rating of the accident at the country's Fukushima nuclear plant, despite France's watchdog upgrading the situation to a level six - placing it second to Chernobyl as the world's worst nuclear disaster.

----

"There is no discussion here about upgrading the international nuclear accident rating for the Fukushima plant," an official at Japan's Nuclear and Industrial Safety Agency said.

----

Level 3 indicates a "serious incident" according to the International Atomic Energy Agency (IAEA) scale, while level four means there has been an "accident with local consequences". Level 6 is a "serious accident". The 1986 explosion at the Soviet nuclear power plant in Chernobyl - rated a maximum 7 - was the world's worst nuclear disaster, with death toll estimates ranging from 4,000 to tens or even hundreds of thousands.

I just got back home..

You're talking about the international scale for nuclear incident based on their severity...

I believe, the Japanese nuclear agency originally rated the Daichi incident as a 5, TMI was a 6 and Chernobyl was a 7, the highest level...

The French yesterday said the rating of the Japan incident ought to be raised based on developments. As of when I walked out from home a couple hours ago, I hadn't seen any change in status by the Japanese.

Dont know if reported already but the incident is now a 6 on a7 grade scale. Tjernobyl was 7.

[jfchandler]

From IAIE

Japan Earthquake Update (15 March 2011, 15:30 UTC)

An earthquake of 6.1 magnitude was reported today at 13:31 UTC in Eastern Honshu, Japan. The Hamaoka nuclear power plant is sited an estimated 100 kilometres from the epicentre.

IEC confirmed with Japan that the plant continues to operate safely.

Units 1 and 2 are decommissioned, Unit 3 is under inspection and not operational, and Units 4 and 5 remain in safe operational status after the earthquake.

Edited March 15, 2011 by jfchandler

[Tywais]

What is 'spent' nuclear fuel?

If it is 'spent', how is it still so dangerous?

"Spent nuclear fuel, occasionally called used nuclear fuel, is nuclear fuel that has been irradiated in a nuclear reactor (usually at a nuclear power plant) it is no longer useful in sustaining a nuclear reaction." Used nuclear fuel The link also gives a breakdown of the various isotopes that are still active.

"Spent fuel discharged from reactors contains appreciable quantities of fissile (U-235 and Pu-239), fertile (U-238), and other radioactive materials, including reaction poisons, which is why the fuel had to be removed."

More on the nuclear fuel cycle

Regarding onsite storage of nuclear waste <Thinkquest>

"When the spent fuel rods are removed from the reactor core, they are extremely hot and must be cooled down. Most nuclear power plants have a temporary storage pool next to the reactor. The spent rods are placed in the pool, where they can cool down. The pool is not filled with ordinary water but with boric acid, which helps to absorb some of the radiation given off by the radioactive nuclei inside the spent rods. The spent fuel rods are supposed to stay in the pool for only about 6 months, but, because there is no permanent storage site, they often stay there for years. Many power plants have had to enlarge their pools to make room for more rods. As pools fill, there are major problems. If the rods are placed too close together, the remaining nuclear fuel could go critical, starting a nuclear chain reaction. Thus, the rods must be monitored and it is very important that the pools do not become too crowded. Also, as an additional safety measure, neutron-absorbing materials similar to those used in control rods are placed amongst the fuel rods. Permanent disposal of the spent fuel is becoming more important as the pools become more and more crowded. "

[JulianLS]

TEPCO said the problem could develop into a critical ''meltdown'' situation, in which fuel rods melt and are destroyed, emitting massive amounts of radioactive materials into the air.

What happened to "there is no chance of another Chernobyl"?

Chernobyl didn't melt down, it exploded. There are lots of differences at Chernobyl.... a much bigger reactor, design flaws including a positive void coefficient, virtually all control rods removed from the core at the time (the opposite of a shutdown), and poorly designed control rods made with graphite (a moderator which increases the reaction) tips that got stuck only a little bit into the core, thus having the opposite effect to that desired. Which resulted in an ongoing critical nuclear reaction that rapidly (seconds not minutes) lead to an explosion of the core. Three mile island melted down, whereas Chernobyl blew up.

The guys at Fukushima are struggling to deal with the residual thermal output, which is probably at around 7% or less of normal running power, because they cant get enough water through the core. Whereas Chernobyl was operating at only 1% of normal power about an hour before it exploded, and went from 7% to 1000% of normal power output in around 40 seconds because it was still in a critical state, and an unstable one at that.

I am not saying that one of the reactors at Fukushima could not explode, it is a possibility even though the current thermal buildup is due to radioactive decay of fuel rods rather than a moderated neutron chain reaction (ie critical reaction). But perhaps a melt down (like TMI) is much more likely than a core explosion (like Chernobyl).

At the end of the day, it's the impact that is important. Chernobyl (a core explosion) had more impact than TMI (a melt down), so you could look at it that way. But then, there are a set of circumstances where a melt down in Fukushima might have more impact on people than the Chernobyl incident. Whilst Chernobyl was a major disaster, the population density in the close environment was low and experts tend to agree that the actual health impact was actually quite limited given the severity of the event. Yes, it spread radioactive material on a wide area.... but that's exactly what you want with radioactive waste: it spread very finely over a very wide area! It's when its all in one place that its a bigger problem! Bear in mind that it was widely dispersed before it was mined, concentrated, and stuck in a nuclear fuel rod in the first place.... But coming back to the point, a less major event in Japan could in theory have a much greater impact on people. Let's hope that set of circumstances doesn't happen.

[jfchandler]

I just found what appears to be an English language announcements web site for Japan's Nuclear and Industry Safety Agency (NISA)...

They have pretty detailed scientific type reports for the Fukushima incidents, including details on radiation readings, personnel injury and more...

As of tonight, however, the most recent report posted is through the end of Monday... Dunno when Tuesday's recap will surface.

http://www.nisa.meti.go.jp/english/index.html

[jfchandler]

I believe I read today that the used rods pool on the upper level of Reactor 4 has something like 780+ rods stored there... No wonder they're cooking...

Whatever report I was reading...indicated that reactor had a much larger volume of used rods in its pool compared to the number stored at the other Daiichi reactors.

Ahh...found it...

From NHK, re Reactor 4 that had the fire this morning:

No.4 reactor chronology

The No.4 reactor at the Fukushima No.1 nuclear power plant had been shut down for regular inspection since November last year.

There was no nuclear fuel in the reactor, and its 783 fuel rods had been removed to a pool for spent nuclear waste.

The pool's temperature more than doubled to 84 degrees Celsius as of 4:18 AM on Monday after its cooling system broke down.

The spent fuel rods are supposed to stay in the pool for only about 6 months, but, because there is no permanent storage site, they often stay there for years. Many power plants have had to enlarge their pools to make room for more rods. As pools fill, there are major problems. If the rods are placed too close together, the remaining nuclear fuel could go critical, starting a nuclear chain reaction. Thus, the rods must be monitored and it is very important that the pools do not become too crowded. Also, as an additional safety measure, neutron-absorbing materials similar to those used in control rods are placed amongst the fuel rods. Permanent disposal of the spent fuel is becoming more important as the pools become more and more crowded. "

Edited March 15, 2011 by jfchandler

[jfchandler]

I'm not a scientist or even a science type.. I'll leave that to Tywais...

But from what I've read, there's some potential for an explosion to occur spontaneously in a TMI type meltdown situation if the fuel pellets come out of their enclosure, fall and melt/molt together, and then, potentially... BOOM... Then the issue would be, is the blast and ensuing emissions contained within the reactor's containment structure.

I am not saying that one of the reactors at Fukushima could not explode, it is a possibility even though the current thermal buildup is due to radioactive decay of fuel rods rather than a moderated neutron chain reaction (ie critical reaction). But perhaps a melt down (like TMI) is much more likely than a core explosion (like Chernobyl).

[WarpSpeed]

Role of U.S. relief efforts, via Reuters:

The U.S. Navy said some arriving warships would deploy on the west coast of Japan's main Honshu island instead of heading to the east coast as planned because of "radiological and navigation hazards".

The risks of the U.S. relief mission have been illustrated by the growing number of U.S. personnel exposed to low-levels of radiation. Still, a Navy spokesman said exposure levels of returning crew were well within safety limits and that operations to assist close ally Japan would continue.

Hmmmmmm I seem to recall making a mention of this risk previously, good to see they took it into account as it was properly a genuine concern as with the 30K no fly zone implemented when someone else expressed concern for flying through the area and I mentioned the plane would still be "hot" when it landed and could contaminate both passengers and ground crew upon disembarking (depending on the type of radiation of course), I guess I was 2 for 2 ..

Edited March 15, 2011 by WarpSpeed

[JulianLS]

I'm not a scientist or even a science type.. I'll leave that to Tywais...

But from what I've read, there's some potential for an explosion to occur spontaneously in a TMI type meltdown situation if the fuel pellets come out of their enclosure, fall and melt/molt together, and then, potentially... BOOM... Then the issue would be, is the blast and ensuing emissions contained within the reactor's containment structure.

I am not saying that one of the reactors at Fukushima could not explode, it is a possibility even though the current thermal buildup is due to radioactive decay of fuel rods rather than a moderated neutron chain reaction (ie critical reaction). But perhaps a melt down (like TMI) is much more likely than a core explosion (like Chernobyl).

Yes, you are right, there is that possibility. But that is not what happened at Chernobyl. Well, the boom happened, but not the meltdown. It went boom before it had a chance to melt down. That said, the boom at Chernobyl was a thermal boom not a nuclear one... so in that sense, another Chernobyl is possible.....

[Lopburi99]

Breaking News! Another fire at reactor #4!

[Lopburi99]

Supposedly it is in the same spot as the first fire. In the spent fuel pond. Helicopters coming in with water supposedly.

Edited March 15, 2011 by Lopburi99

[Lopburi99]

CNN:

[6:42 p.m. ET Tuesday, 5:42 a.m. Wednesday in Tokyo] U.S. government experts trying to construct a model of radiation plumes emanating from Japan's Fukushima Daiichi power plant are being hampered by a "paucity of good data," a senior administration official said.

[Jdietz]

Good morning everyone!

If I read it correctly, the problem with the holding pool in Daiichi #4 plant is that it doesn't hold spent fuel, but the active fuel which was removed from the reactor for maintenance.

Basically it means they have a full active reactor core sitting OUTSIDE its containment vessel, with no control rods, only water and boron. So when that pool dries up it may reach criticality. Also just dumping untreated water on it won't stop it reacting.

The severity of the reaction is dependent on how close these fuel rods are stacked together, it won't be as close as in the reactor core for sure. But this is clearly the largest problem at the moment, as all the other fuel is where it belongs, inside the reactor vessel.

[BuckarooBanzai]

Fukushima: Mark 1 Nuclear Reactor Design Caused GE Scientist To Quit In ProtestThirty-five years ago, Dale G. Bridenbaugh and two of his colleagues at General Electric resigned from their jobs after becoming increasingly convinced that the nuclear reactor design they were reviewing -- the Mark 1 -- was so flawed it could lead to a devastating accident.

ABC News asked GE for more detail about how the company responded to critiques of its Mark 1 design. GE spokesman Michael Tetuan said in an email that, over the past 40 years, the company has made several modifications to its Mark 1 reactors in the U.S., including installing "quenchers" and fortifying the steel structures "to accommodate the loads that were generated." He said that GE's responses to modifications ordered by the Nuclear Regulatory Commission were also shared with the Japanese nuclear industry.

http://abcnews.go.com/Blotter/fukushima-mark-nuclear-reactor-design-caused-ge-scientist/story?id=13141287

Interesting article.

[brahmburgers]

One use for spent uranium: can be used to tip warheads, because they're the densest metal - able to pierce tank armor or for 'bunker busters'.

Since the main reactor containment buildings survived both the quake and Tsunami, it seems that *IF* the back-up generators powering the emergency cooling system had been located on the roof of the containment structures - where the Tsunami could presumably not get to them, the whole disaster would have been avoided.

Not necessarily. The quake, by itself, may have cracked the containment vessel and/or floor, thereby enabling coolant to leak out. Additionally, the quake itself could easily have broken/bolloxed up any of the myriad pipes fixed at the plants - some of those pipes used for water.

A simple design flaw? If so, could the hundreds of similar nuke-plants around the world be retrofitted to avoid the next big disaster? Maybe including Indian Point, only 35 miles from New York City?

http://www.nbcnewyor...-117983419.html

.

[/size]

There are N plants along America's west coast, one south of San Francisco. Not only are they v. close to the San Andreas fault, they're also upwind from large populations. Sacramento (California's capital) had a N power plant called Rancho Seco. Though it was new and functioning, it was closed down by a vote of the residents. Can you imagine a Thai N plant, up and running safely, being closed down by a vote of nearby residents? Impossible.

Here's a hint of why: Just yesterday, Mr. Kurujit, a member of the Thai Nuclear Power Project Development Office said (in response to a demonstration by villagers against an N plant there) "The government will be the one making the decision to build or not to build a nuclear power plant."

In other words, Mr. VIP Kurujit says it's the government, not the little people who live in the adjoining villages, who will make the decisions about where and whether to build N power plants in Thailand.

Edited March 16, 2011 by brahmburgers

[webfact]

Fire at Japan's nuclear reactor

Another fire broke out on Wednesday at an earthquake-damaged Japanese nuclear plant, emitting low level radiation heading towards Tokyo.

Japanese TV pictures showed smoke rising from the facility at mid-Wednesday morning.

Japan's Nuclear and Industrial Safety Agency said two workers were missing after blasts at the facility a day earlier blew a hole in the building housing the No. 4 reactor.

-- The Nation 2011-03-16

[webfact]

FLASH: Fuel pool may have heated, producing steam at reactor No.3 at Fukushima Daiichi nuclear plant: Tepco /via@Reuters

[powderpuff]

Interesting article.

Related story. This design of reactor was recommended to be scrapped in 1972.

NYT

[webfact]

Information on radiation levels in Japan, and latest on Canada's response to the earthquake http://ow.ly/4flfw /via@DFAIT_MAECI

[jfchandler]

From NHK:

Another fire at No.4 reactor

Tokyo Electric Power Company said early on Wednesday that a fire had broken out at one of the reactor buildings at the Fukushima Daiichi nuclear power plant. The same building was the scene of a fire the day before.

The utility says a worker spotted flames at around 5:45 AM near the northwestern corner of the building that houses the No. 4 reactor.

It says, however, that the flames could not be confirmed half an hour later from several dozen meters away.

The fire broke out at around the same spot in the building as Tuesday's fire, where an instrument that adjusts the speed of a pump sending water to the reactor is located.

The company says workers cannot get any closer to the spot because the radiation level is higher there.

It says Tuesday's fire went out on its own, and that its cause is unclear.

The No. 4 Reactor was undergoing checks at the time of the quake, and was not operating. But the utility company has been having trouble cooling down a storage pool for spent nuclear fuel rods inside the building.

Wednesday, March 16, 2011 10:12 +0900 (JST)