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View Full Version : What is nuclear meltdown-what to focus on



Luke
14th March 2011, 11:52
I see a lot of rumour spreading, based on assumption we know what words mean.
What is nuclear meltdown?
(Watches images of chernobyl fire fly by)

Actually, while it happened there, it was not what caused the fallout!

Meltdown simply means that fuel rods melted and turned reactor inoperative. As in "large piece of costly radioactive junk"

That do expel some heat. Every radioactive rock expel heat. That is part of what being radioactive is about.

No problem, as long as this **** is contained. In a concrete dome lined with lead.

REactors are build in a way that prevents them from going critical. They cannot become nukes.

They can become dirty nukes though, if the melt-down fuel will get blown up outside containment dome OR the used fuel will get blown outside their containment.

Problem is, when we strip the fancy terminology, the nuclear plant is basically one big steam boiler, with steam turbine attached. Stuff straight from XIX century.

Even molten reactor produces heat, and as long as you provide water there would be steam.

Problem: you cannot just dump all the water from the reactor. This **** is radioactive for one. Also, the less coolant volume, the easier it's temperature goes up.

Steam boilers do blow up, especially if you mess with their safety valves.
This is what happened in Chernobyl. Also, in Chernobyl there was no containment dome/vault, so when boiler blow up, it taken everything near it. Including the reactor.

This is danger in Japan too, still before their stuff start flying around the containments dome need to be cracked.


*****

Core of the problem is molten reactor producing heat, which turns coolant into highly-pressurized hydrogen-oxygen mix. So far they try to cool the thing down by introducing coolant mixed with nuclear-reaction slowing medium in order to put the boiler out of fire.

What they need to do is take the water/steam/hydrogen out of the equation.

Remember though, it is irradiated too. They cannot just vent it out to atmosphere. But they will do it before there would be a danger of blowing up the whole thing. Still we are talking a fraction of what happened in Ukraine.

The place where (I think) our intentions should go -is lowering the pressure. lowering the temperature. Taking the kettle out from the fire. No more irradiated steam

Do not let focus yourself on disaster if you do not want one to happen.

Operator
14th March 2011, 13:23
Hi Kosh,

Good post ... you said take water/vapor out of the equation. But isn't this in contradiction to the need to cool the rods ?
Currently they are cooling the rods with seawater. So water is already in the equation. And it should not get back into the
sea ... I wonder if they have that all still under control.

Luke
14th March 2011, 15:38
Again, I am speaking from my limited amount of knowledge:

The seawater is last ditch attempt to prevent meltdown- that is have the reactor salvagable.

The above "water is a problem" statement is for situation when you decide that all you want is to contain the event after salvaging the fuel is impossible.

Seawater they pump is laced with radiation moderator, in attempt to bring the amount of radiation produced down. This make sense only if fuel rods are intact.
Even with control rods lowered, you cannot halt the process- you can only bring it down to about 10% of nominal output (again- to my knowledge). That is enough heat to melt the core if uncooled. The cooling procedure is needed till there will be fuel in the core. The "killing" process takes years.
When fuel rods will melt you do not have a reactor anymore- you have radioactive slag deposit.

After the thing will melt, the only thing you can do is prevent any explosive build-up and bury the thing for 10k years or whereabouts. That means abandoning the plant and equipment. And is , IMO a sensible solution.

Problem is, taking into account the corporate and national mentality - the decision to abandon salvaging op and just kill the thing will be prolonged to last possible moment.

See Macondo well for reference- again it taken months to reach "just kill it" decision point.