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Reactor meltdown possible in Japan.


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In all seriousness, I hope you are correct about all of this.

Me too. I'm certainly no expert on the matter. I'm just going by what I think I understand about each situation, and how they differ.

Either way, this is a scary situation that's clearly still far from under control.

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If indeed the fuel pool is a major issue I'd assume it sustained damage from the blast at #3. Still this report would make it appear the fuel pool shouldn't be a significant problem in such a short period of time.

http://resources.nei.org/documents/japan/Used_Fuel_Pools_Key_Facts.pdf

What Could Happen During an Accident?

* The systems that cool and maintain water levels in the pools are designed to withstand severe events. If these systems are unable to function, the heat generated by the used fuel would result in a slow increase in the temperature of the spent fuel pool water. The operating temperature of the pools is

typically around 40 degrees C or 100 degrees F (the boiling point for water is 100 C or 212 F). This slow increase in temperature would result in an increased evaporation rate. Rapid evaporation of the water will not occur.

* Exact evaporation rates would depend on the amount of used fuel in the pool and how long it has cooled. The rate at which the pool water level would decrease (due to evaporation or mild boiling) in the absence of cooling system function would not be expected to lower water levels by more than a

few percent per day. Given that there is approximately 16 feet or more of water above the used fuel assemblies, operators would have ample time (days to weeks) to find another way to add water to the pools before the fuel would become exposed. For example, water could easily be added using a fire hose.

* If the water level decreases below the top of the fuel assembly, oxidation of the zirconium cladding could occur. This oxidation could result in some hydrogen generation. However, only the fuel assemblies with the least cooling time (on the order of weeks after discharge from the reactor) would be susceptible to this oxidation. The temperature of the fuel assemblies decreases exponentially with cooling time. The rate of hydrogen generation depends on the temperature of the fuel assembly, with hotter temperatures leading to higher gas generation rates. However, the temperature of the cladding must rise to approximately 1,000 C before significant hydrogen generation rate occurs. This is extremely unlikely to occur after as little as 120 days (16 weeks) of cooling. As a reference, the melting point of zirconium is approximately 1,800 degrees C.

 Even if the water level in the pools was to decrease sufficiently so that the fuel were exposed to air, the same level of overheating that can occur in a reactor accident would not occur in the used fuel pool because the used fuel assemblies in the pool are cooler than in the reactor. It is highly unlikely

that used fuel temperatures could reach the point where melting could occur, although some damage to the cladding cannot be ruled out. The likelihood of cladding damage, as with hydrogen generation, decreases substantially with temperature and cooling time.

* There has been some speculation that, if the used fuel pool were completely drained, the zirconium cladding might ignite and a “zirconium fire” might occur. Studies performed by the Department of Energy indicate that is virtually impossible to ignite zirconium tubing.

* At the surface of the used fuel pool, the gamma dose rate from radiation emanating off the used fuel assemblies is typically less than 2 millirem per hour. If the water level decreases, gamma radiation levels would increase substantially. This increase would be noticed at the radiation monitors near the reactor buildings.

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Breaking news: Fuel rods damage at Fukushima's 2 reactors estimated at 70% and 33%

WHICH 2 reactors?

Kyodo news

Edit: Fukushima II (Daini) maybe? Not Dai-Ichi.

No, it's probably reactors 1 and 3 at Dai-Ichi... the ones that have been suspected to have had a partial meltdown.

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Breaking news: Fuel rods damage at Fukushima's 2 reactors estimated at 70% and 33%

WHICH 2 reactors?

Kyodo news

Edit: Fukushima II (Daini) maybe? Not Dai-Ichi.

I would think Reactor's 1 and 3. They probably haven't been able to estimate reactor 2 yet. But that's just speculation.

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TOKYO, March 16, Kyodo

An estimated 70 percent of the nuclear fuel rods have been damaged at the troubled No. 1 reactor of the Fukushima No.1 nuclear power plant and 33 percent at the No. 2 reactor, Tokyo Electric Power Co. said Wednesday.

The reactors' cores are believed to have partially melted with their cooling functions lost after Friday's magnitude 9.0 earthquake rocked Fukushima Prefecture and other areas in northeastern and eastern Japan.

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TOKYO, March 16, Kyodo

An estimated 70 percent of the nuclear fuel rods have been damaged at the troubled No. 1 reactor of the Fukushima No.1 nuclear power plant and 33 percent at the No. 2 reactor, Tokyo Electric Power Co. said Wednesday.

The reactors' cores are believed to have partially melted with their cooling functions lost after Friday's magnitude 9.0 earthquake rocked Fukushima Prefecture and other areas in northeastern and eastern Japan.

So 1 and 2, then. Was 3 the one they suspected might have fully melted?

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If indeed the fuel pool is a major issue I'd assume it sustained damage from the blast at #3. Still this report would make it appear the fuel pool shouldn't be a significant problem in such a short period of time.

http://resources.nei...s_Key_Facts.pdf

What Could Happen During an Accident?

* The systems that cool and maintain water levels in the pools are designed to withstand severe events. If these systems are unable to function, the heat generated by the used fuel would result in a slow increase in the temperature of the spent fuel pool water. The operating temperature of the pools is

typically around 40 degrees C or 100 degrees F (the boiling point for water is 100 C or 212 F). This slow increase in temperature would result in an increased evaporation rate. Rapid evaporation of the water will not occur.

* Exact evaporation rates would depend on the amount of used fuel in the pool and how long it has cooled. The rate at which the pool water level would decrease (due to evaporation or mild boiling) in the absence of cooling system function would not be expected to lower water levels by more than a

few percent per day. Given that there is approximately 16 feet or more of water above the used fuel assemblies, operators would have ample time (days to weeks) to find another way to add water to the pools before the fuel would become exposed. For example, water could easily be added using a fire hose.

* If the water level decreases below the top of the fuel assembly, oxidation of the zirconium cladding could occur. This oxidation could result in some hydrogen generation. However, only the fuel assemblies with the least cooling time (on the order of weeks after discharge from the reactor) would be susceptible to this oxidation. The temperature of the fuel assemblies decreases exponentially with cooling time. The rate of hydrogen generation depends on the temperature of the fuel assembly, with hotter temperatures leading to higher gas generation rates. However, the temperature of the cladding must rise to approximately 1,000 C before significant hydrogen generation rate occurs. This is extremely unlikely to occur after as little as 120 days (16 weeks) of cooling. As a reference, the melting point of zirconium is approximately 1,800 degrees C.

 Even if the water level in the pools was to decrease sufficiently so that the fuel were exposed to air, the same level of overheating that can occur in a reactor accident would not occur in the used fuel pool because the used fuel assemblies in the pool are cooler than in the reactor. It is highly unlikely

that used fuel temperatures could reach the point where melting could occur, although some damage to the cladding cannot be ruled out. The likelihood of cladding damage, as with hydrogen generation, decreases substantially with temperature and cooling time.

* There has been some speculation that, if the used fuel pool were completely drained, the zirconium cladding might ignite and a “zirconium fire” might occur. Studies performed by the Department of Energy indicate that is virtually impossible to ignite zirconium tubing.

* At the surface of the used fuel pool, the gamma dose rate from radiation emanating off the used fuel assemblies is typically less than 2 millirem per hour. If the water level decreases, gamma radiation levels would increase substantially. This increase would be noticed at the radiation monitors near the reactor buildings.

The temp was 84C before the reactor exploded this morning. They haven't dropped any water into it since then. It's not sitting that 40C. They even thought it was boiling earlier. All this doesn't add up to slow evaporation.

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So 1 and 2, then. Was 3 the one they suspected might have fully melted?

I don't think so. They generally have just said that some damage has been suspected at all three. May have missed a report though.

I'm surprised that they came up with numbers and would have thought that the #2 reactor would have been worse off. That's quite a bit of damage for the #1 reactor.

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I lived in a town in RI for 17 years where a nuclear accident occurred in 1964 and a man was killed. 20 years later a proposal was put forth to build a Nuke plant on the Ocean front. The entire town rallied and killed the proposal, one of the most popular reasons for voting no was the accident. The chain of events in Japan will hurt the nuclear industry for decades, I have no opinion either way.

Database of radiological incidents and related events--Johnston's Archive

Wood River criticality accident, 1964

compiled by Wm. Robert Johnston

last modified 14 September 2005

Date: 24 July 1964

Location: Wood River, Rhode Island, USA

Type of event: criticality accident with uranium solution

Description:

The accident occurred at a facility which reprocessed for recovery highly enriched uranium in scrap material from fuel element production. A tank containing uranium (93% U-235) in sodium carbonate solution was being agitated by a stirrer. A worker, intending to add a bottle of trichloroethane to remove organics, erroneously added a bottle of uranium solution to the tank, producing a criticality excursion accompanied by a flash of light and the splashing of about 20% of the tank's contents (about 10 liters out of 40-50 liters, including the bottle contents) out of the tank. The worker fled to the site's emergency building. Two plant administrators returned to the building; one turned off the agitator, producing a lesser criticality excursion that was not recognized until their dosimeters were examined. The administrators incurred doses of 100 rads and 60 rads. The worker absorbed about 10,000 rads and died 49 hours after the accident.

Consequences: 1 fatality (10,000 rem), 1 injury.

References:

McLaughlin, Thomas P., Shean P. Monahan, Norman L. Pruvost, Vladimir V. Frolov, Boris G. Ryazanov, and Victor I. Sviridov, May 2000, A Review of Criticality Accidents, 2000 Revision, Los Alamos National Laboratory (Los Alamos, NM), on line at CSRIC [http://www.csirc.net/docs/reports/la-13638.pdf].

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Kyoto repairing the use of boron to prevent recriticality in reactor 4.

For those of you saying there's nothing to see here...reminds me of Leslie nielsen in the naked gun when the fireworks factory is blowing up

There are many chemical reactions going on and chemically Zr does burn

Zirconium metal is coated with an oxide layer that usually renders it inactive. However zirconium does burn in air if provoked to form thedioxide zirconium(IV) oxide, ZrO2.

Zr(s) + O2(g) → ZrO2(s)

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Kyoto repairing the use of boron to prevent recriticality in reactor 4.

For those of you saying there's nothing to see here...reminds me of Leslie nielsen in the naked gun when the fireworks factory is blowing up

Wow... that "recriticality" is even a possibility is scary.

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There are many chemical reactions going on and chemically Zr does burn

Zirconium metal is coated with an oxide layer that usually renders it inactive. However zirconium does burn in air if provoked to form thedioxide zirconium(IV) oxide, ZrO2.

Zr(s) + O2(g) → ZrO2(s)

Yep. Being near a type 1 reactor and knowing employees working at these types of reactors....heroes....every one of these guys staying on station despite a spiraling situation. A few dozen men/women preventing a disaster that could displace or sicken hundreds of thousands.

As one said they train in simulators every 1 to 2 months....they could never train for this. Mind boggling that they've been able to play whack a mole so far at great risk to themselves. They may not be getting info out like we would all like but I doubt most of us would want to be in their shoes.

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Wow... that "recriticality" is even a possibility is scary.

I thought I heard yesterday from some expert that they were hesitant to dump water in from helicopters because they were concerned about dislodging the rods from their racks, having them touch each other, and thus starting to react. People on here said that was impossible so I just assumed I misheard, but maybe I didn't?

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Wow... that "recriticality" is even a possibility is scary.

One of the big gripes with the anti nuke crowd here in Plymouth is the storage of spent rods on site. When the Nevada site never opened they all stored locally. We can bet storage at all these sites will go through careful scrutiny.

I was asking a buddy in the biz why there isn't more from "experts"...reason is we have these reactors in many locations. GE knew about issues (today's times) and there is no upside from going public. It's a bad situation barely in control. As one expert said on CNN they are hanging on by their fingernails.

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I thought I heard yesterday from some expert that they were hesitant to dump water in from helicopters because they were concerned about dislodging the rods from their racks, having them touch each other, and thus starting to react. People on here said that was impossible so I just assumed I misheard, but maybe I didn't?

No, I heard that too. But that would be an induced situation where you displaced rods that are set up apart from each other in steel shelving, from what I've gathered, and somehow got them all together. I didn't think there was a possibility for criticality to happen spontaneously.

Maybe the boron is just a precaution in the extremely unlikely (and extremely bad) event that that would happen.

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But even if the worst case release does occur, it might be wise for our panicky types to first read up on Chernobyl and understand the limits of potential impacts. We know that Chernobyl's damaging effects were pretty much limited to about 1000 miles out at its longest extent (to the north.) The US west coast is at least 4500 miles from these reactors, Hawaii 3500 miles away, mainland Alaska 2700 miles away. Americans in the states are not in danger.

Yeah, believe it or not, I actually checked the distance between Tokyo and L.A. today-- I was curious, let's just say. (It's ~5,400 mi.)

The sheer distance is the best protection at the end of the day. That is a sh*tload of miles to travel-- even for potent radiation.

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