Possible reactor meltdown in Japan

[MolaKule]

Quote:
Are you sure you are not referring to PWR's which have 2 to 4 steam generators?


"In most Boiling Water Reactors (BWR) there are total of three vessels surrounding the actual core."

I was using vessel in an engineering context; Maybe I should have used the phrasing, "In most Boiling Water Reactors (BWR) there are total of three or more structures surrounding the actual core."


I was referring to the ABB- and GE-type designs.

From the out side in toward the core like an onion you have:

1. the shield building (thick concrete),

2. the main containment structure (thick steel),

3. the dry well (concrete and composite),

4. the reactor shield wall (composite structure),

the reactor vessel itself (specialized steel alloys).

 

[Cause4Alarm]

if they have to keep suspending sea water pump because of aftershocks theres going to be real problems.........on top of that almost no new info is coming out. seems like no news is bad news seeing as how they tried to be optimistic up to the point the containment building exploded.......my guess is they don't know how bad it really is and that the explosion had to take out some equipment they were using

 

[Al]

Originally Posted By: MolaKule

1. the shield building (thick concrete),

2. the main containment structure (thick steel),

3. the dry well (concrete and composite),

4. the reactor shield wall (composite structure),

the reactor vessel itself (specialized steel alloys).




The Thick concrete shield and steel are one structure. I am not certain they exist on this BWR

 

[MolaKule]

As with the Seacoast villages, they won't really know the full extent of the damage until the aftershocks settle down.

And until things cool down around the reactor, they won't know the full extent of core damage.

But notice in the nightime pictures that lights around the nuclear facilities are still functioning.

The Japanese have been building nuclear reactors and power infrastrctures for many years.

While land and infrastructure may be damaged, the human spirit is very resilient.

 

[MolaKule]

Quote:
The Thick concrete shield and steel are one structure. I am not certain they exist on this BWR


Much depends on the design.

In some cases you have a thick steel lining contacting or in contact with the concrete shell.

 

[Cause4Alarm]

msnbc now reports partial core melt is confirmed

 

[greenaccord02]

LOL just searched for this on google and the image that shows up alongside the news story is the picture of Homer Simpson holding that fuel rod in tongs from the beginning of the Simpsons episodes. Maybe just a little bit in poor taste.

 

[Al]

Originally Posted By: MolaKule

In some cases you have a thick steel lining contacting or in contact with the concrete shell.

Of this type I have only seeen one type. Steel inner shell with poured concrete with #18 Rebar and 3 directional Tendons so the "Containment" can hold around 60 psi internal press in the whole containment.

Hope they have a containment building. But why would they have a tin Butler building around a containment structure. Answer: There is no Containment building? (Except for the Drywell and Wetwell)

 

[JHZR2]

This is all interesting. I especially appreciate the knowledge of different plant designs that Mola has and the practical experience that Al has.

Great stuff, helps make heads and tails of the news coming out.

One question that may not be all that OT. Let's say there is a big release. Sure, dispersion will make it fairly low levels of contamination that could be detected on the west coast, let alone the east coast (I assume). That said, there WILL be something in the air, and in the rainfall, even for us east coasters. So:

1) how would a full meltdown release of one of these Japanese reactors compare to the above-ground release that occurred back in the 1950/60s for weapons testing in AZ/NV/NM?

2) How would the releases from this sort of a disaster compare to the fission and fission/fusion bombs in terms of chemicals/radioactive compounds?

3) This is very complex, so very roughly, how would the time-related dispersion compare to, say the 50 MT hydrogen bomb that was air-tested in the Soviet Union in the 1950s? Do these compounds decay faster or slower?

4) What would we expect the final decay products of this release to be? What would the half life of the release items be?

5) What nutritonal or other precautions should be taken given this release? How about extra filtration of rainwater? Iodine?

Thanks!

 

[Al]

Originally Posted By: JHZR2

1) how would a full meltdown release of one of these Japanese reactors compare to the above-ground release that occurred back in the 1950/60s for weapons testing in AZ/NV/NM?

I think in the very worst case you will have a lot of local contamination but very little airborne. You are not going to have an explosion.

The Russians had such a disaster because there was an explosion. And then the core burned because it was graphite. The core can't not go critical because you have what is called a negative core temperature coefficient. That is; the hotter it gets the more the neutrons are "poisoned". I think I am correct here.

I assume there will be some detectable radiation in the U.S if the winds are favorable but it would be so low so as not to even consider it. Absolutely no comparison with an exploded Nuke. Don't lose any sleep bc of it.

Most of the fission products are just gonna stay in the trashed reactor core. Only the gases will disperse and they stop dispersing for the most part when fission stops.

The biggest problem is how to keep the core cool going forward..without contamination of the water used to cool it. It needs to have a self contained cooling system to operate for 1 to two years at least.

Originally Posted By: JHZR2

Which core? One in Japan or TMI? Isn't TMI still functioning, with only a very small amount of steam or another fluid that released? Isn't TMI supposed to be making millions of BTU?

The Japanese core is still making those milions of Btu's. Decay heat is like 2% of full power. And full power is say 1800 MW thermal.

 

[Shannow]

Oz news is just reporting that the reactor pressure vessels haven't been breached (but HAVE been vented), and that the explosion initiated in the turbine house.

High Voltage Generators are usually filled with and cooled by Gaseous hydrogen at around 60psi...hydrogen is held in by a seal oil system, which is generally duty/standby AC pumps, and a DC battery back-up.

Islanding of the station (removal from the grid AC supplies) means battery operation briefly, then reliance on station diesel gens...lose seal oil, and the H2 gets out.

Although any reasonable generator would have an emergency degass (to CO2) in an event such as this.

 

[Rick in PA]

Can you give a quick explanation on why H2 is used in high voltage generators? The first things I think of is; it's flammable and if the system is not perfectly sealed, I'd expect to be a very leaky gas. There must be some compelling reason to use it. P.S. what is "seal oil", how does this work?

 

[SteveSRT8]

Originally Posted By: Cause4Alarm
the explosion had to take out some equipment they were using


There will be bad news now.

 

[Al]

Originally Posted By: Rick in PA
Can you give a quick explanation on why H2 is used in high voltage generators?

BC its the only gas that has the ability to remove enough heat from the generating core (rotor). There is also less friction with the rotor bc the gas is so light.

 

[Rick in PA]

OK, I suspected heat transfer, didn't think about the "slippery" part.

 

[Shannow]

Yeah, our (3000RPM) machines would overheat the rotors just on windage at 2,000RPM. As Al says, H2 has huge heat absorption capabilities.

BTW, the stator (22,000 Volts) is cooled by circulating water through the conductor bars.

 

[Mystic]

After I saw that explosion at that reactor, I became more convinced that there will be a serious nuclear incident. And then I heard that other reactors are also having serious problems. Maybe they can still get that reactor core cooled using seawater. If nothing big happens in a couple of days they may have succeeded. But if one or more of those reactors experience core meltdowns, the radiation will affect not just Japan, but even the USA and at least the entire northern hemisphere.

 

[MolaKule]

Quote:
3) This is very complex, so very roughly, how would the time-related dispersion compare to, say the 50 MT hydrogen bomb that was air-tested in the Soviet Union in the 1950s? Do these compounds decay faster or slower?


In most Cold-War thermonuclear weapons, such as hydrogen bombs, you have a small fission trigger system or small fission bomb setting off the hydrogen section of the bomb. Different decay products are produced and these products are complex. Even though the energy yield in hydrogen weapons is larger, the areal dispersal of hydrogen bomb by-products is greater since the burst core goes higher into the atmosphere, so fallout density should actually be less.

Quote:
4) What would we expect the final decay products of this release to be? What would the half life of the release items be?


Some of the dischrages are gases and some are solids: Most of the discharge are isotopes of Tellurium (X istopes), Kripton (4 isotopes), Xe or Zenon (4 isotopes), Cesium (2 isotopes), and Iodine (5 isotopes).

Tellurium – 135 has a HL of 11 sec, Iodine-135 has HL of 6.7 hours, Zenon (Xe-135) has a HL of 9.2 hours, and Cesium – 135 has a HL of 2.3 x 10^6 years. However, most of the Cesium gets trapped in the water.

Radiation exposure or dosage is determined by time of exposure and amount of effluent in the environment.

A typical gamma-ray "whole-body" dose from Iodine-135 2 hours following a reactor accident, for a person at 2km distance downwind with a downwind velocity of 1 m/s, would be 1.1 X 1^-2 rems, which is neglible.

However, the dose "commitment" to the thyroid is 38.8 rems, which is rather high.

This is why the evacuation radius was increased.

Considering the distance we are from Japan, I seriously doubt we would see any health effects from Iodine or Cesium.

 

[dakota99]

More on the specific dangers of Fukushima 1 plant's reactor 3: The BBC's Chris Hogg in Tokyo says the reactor is fueled with uranium and plutonium, meaning the consequences of a meltdown are much more severe than at the other reactors. -Reuters

wow.

 

[Cause4Alarm]

Greeeeaaaat......they believe that reactor is also in a meltdown as well