[blackdog]

Some smart minds need to explain this to me. I'm a boiler maintenance mechanic. The number one rule of boiler safety is to never-ever add water to a hot boiler gone low or dry. The reason for this is that water expands 1,600 times by volume when converted to steam. One pound of water added to a dry boiler is like five sticks of dynamite.

So........How do you introduce cooling water back into a superheated nuclear mass without an expolosion? I would think you would have to first boil the water into superheated steam (400 to 600 degrees) and then gradually throttle back the steam temperature once the heat absorption from the nuclear material settles the steam climb at an upper limit line to begin cooling from.

Any smart folks out there who can idjucate me would be appreciated.

[steve86]

Not schmart folk here but the cooling pools aren’t enclosed like the boiler. Yes, the water would initially flash off but most or all of the rods in the pools are partially covered anyway. P.S. Interesting statistics you gave about the amount of volume expansion and explosive potential in an enclosed system.

[ltc8k6]

You add it under pressure?

[dayglored]

> So........How do you introduce cooling water back into a superheated nuclear mass without an expolosion? I would think you would have to first boil the water into superheated steam (400 to 600 degrees) and then gradually throttle back the steam temperature once the heat absorption from the nuclear material settles the steam climb at an upper limit line to begin cooling from. Any smart folks out there who can idjucate me would be appreciated.

I wonder the same thing. I assume they're introducing it to the superheated areas slowly enough that the expansion can take place slowly enough to be safely contained.

Hell, I don't add cold water or oil to an overheated car engine, much less to an overheated reactor core.

I also assume that the amount of water they are able to "sprinkle" down from firehoses and whatnot is not contained, since the buildings are open, so while they'll get vapor expansion, it's happening in free air, essentially.

But I'm not there, and I'm not an expert... just a guy with a 35-year old physics degree... who wonders the same thing.

[meatloaf]

They are dealing with several situations that confused the public.

1. The primary containment, the reinforced concrete building that houses the reactor was never breached. Pressure from that is vented into the sheet metal and structural steel building on top of the reactor. That is where the hyfrogen ignited after it was vented.

2. The reactor vents into a torus, larged water filled structure, which reduces pressure.

3. The spent fuel pools, stainless steel lined concrete, which are outside the primary containment and which are probably now exposed have been the target of the helicopter water drops and the water from the fire engine deck guns.

4. In this country both the reactor, RPV, and the steel lined reinforced containment buildings are ASME pressure vessels.

[silverleaf]

Given the situation, seems like water (maybe mixed with boron or other chemicals to stop or slow down the reaction) is their only and best way to cool things down, and venting (radioactivity-filled steam) is their controlled way or reducing the resulting pressure instead of having the roofs blown off more reactor buildings by hydrogen explosions and damaging other components in the process

They have just been dumping seawater into the buildings and refilling the fuel storage pool. Steam and pressure must be better choices than not cooling as fast as possible

These heroes at this facility just seem to be dealing with choosing a bad choice or chancing a worse choice

[silverleaf]

I dont usually rely much on Wiki but if you do some reading about light water reactors in general and Fukushima in particular it may help, give your mechanical background

http://en.wikipedia.org/wiki/Fukushima_I_nuclear_accidents#Cooling_requirements

then come back here and explain it to us!

[Revel]

The reason they can do that is because they are continuously venting.

I also believe they are doing more than venting. Remember the report yesterday about how they increased the amount of sea water by 9 times in reactor core 1(I believe) in order to cool it down.

Now it does not take much understanding to figure out that the coolant outlet is therefore wide open with the water running onto the land and into the sea. I believe that there no longer is a coolant loop. They are simply blasting water in and letting it run out into the environment. A continuing last effort attempt to prevent total meltdown. This prevents steam pressure buildup.

[FreedomPoster]

I think a BWR is a little more like a tea kettle than a coal / oil / natural gas steam boiler. Which over-simplifies things hugely, I’m sure.

[Clay Moore]

A very good question indeed.

As a guy who has burned a lot of welding rod in the last 30+ years, I have seen some amazing things happen after throwing red hot steel into water. Cracking and huge changes in hardness are not uncommon.

By the same token, what are the alternatives?

[delacoert]

How do you introduce cooling water back into a superheated nuclear mass without an explosion?

You start by designing the pressure vessel and safety systems for a worst case senario, i.e., not to blow up during a core re-wet after a LOCA.

If all else fails you bend over and kiss your ass goodbye.

[screaminsunshine]

Yes. Learned in Maritime firefighting school.