Avoiding nuclear meltdown

[pezmancometh]

STOPPING A NUCLEAR DISASTER
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The Japanese disaster clearly shows that the atom must be carefully controlled. Does anyone know the extent of the damage that is possible when a power station can not be controlled? All three of the power complexes (3 Mile Island, USA; Chernobyl, Russia; and Japan) that lost control were caused by the same problem. They lost the ability to cool the reactor. Why do we continue using the same systems that cause such catastrophic damage?

When everything is working properly pumps supply the coolant. What happens when the pumps do not work? That is the crux of the problem…Keep in mind that the pumps must have power for the entire time of the problem. Some form of cooling, in proper quantities, must be available at all times. In a disaster, outside power may not be possible.

Helicopters spray water onto the situation but that is akin to using a water pistol on a big bonfire. In other words, great quantities of water must be in constant readiness and used EARLY before the pile breeds more radiation. Obviously the amount of coolant rate has to be controlled.

There is a power that can be used to supply the water at any time and that is gravity. Imagine if the Japanese reactors were built under sea level. The water could have been introduced immediately stopping the continuing heating of the core. None of the world’s reactors are under sea level. The water must be higher than the reactor and the spent control rods.

This will require dams to form lakes, conduit to the reactor, and a fool-proof valve system that can be activated by one person. Forget a fancy design. Possibly a dam would need to be formed to hold incoming water around the reactor until everything has been stabilized.

Undoubtedly this requires huge investments but the public must have faith that another melt-down will not occur. There is no other continuing power source known to man. Keep in mind that in over 10 years of nuclear power in the United States there has never been one death. Compare this to coal mining where there have been hundreds. The one accident on our own soil was caused by the operators doing experiments that were unnecessary.

We Need Power! Something Must be Done!

Pat Barrett – BSME March 28, 2011

 

[C1]

I understood from a radio program announcement that a certain number of USA reactors employ gravity powered backup cooling. There also are at least five new designs in progress. Not sure though that this is fool proof. The Japan earthquake lasted for like nine minutes. A sufficiently violent earthquake/internal explosion could (it would seem) disrupt any feeder cooling supply. (What if there is a meteor strike?)

USN ships avoid the problem by jettisoning the reactor to the sea bottom (gulp!).

 

[pw38]

Well then we just have to deal with Godzilla.

 

[bwanaaa]

Where people are involved, here is always the chance of failure. Even when the the rules are simple, people do not follow them. Why don't we ask Watson what to do about the energy problem. Has anyone tried asking a computer like that something useful, instead of just making it play jeopardy?

 

[Mark R]

I understood from a radio program announcement that a certain number of USA reactors employ gravity powered backup cooling. There also are at least five new designs in progress. Not sure though that this is fool proof. The Japan earthquake lasted for like nine minutes. A sufficiently violent earthquake/internal explosion could (it would seem) disrupt any feeder cooling supply. (What if there is a meteor strike?)

USN ships avoid the problem by jettisoning the reactor to the sea bottom (gulp!).

No commercial reactors currently utilise gravity cooling. Although 2 gravity cooled designs have been licensed and several plants are under construction in the US.

The problem with these gravity cooled designs, is that gravity only serves to remove heat from the core, into the containment building. You still have to remove the heat from the containment building. The current designs only offer 72 hours of cooling for the building itself before additional cooling needs to be provided (both designs are similar in that they have a roof tank of water which is allowed to spray onto the building skin to cool it - but this is limited due to weight) - but cooling the building is a lot easier than cooling the reactor (you can just top up the spray tank, or if you can't get up there, then spray the building with fire trucks or water cannons).

There is a limit to the strength of earthquakes, and equally, it is possible to design pipework and pumps to very high levels of strength (expensive, but it can be done). The Japan earthquake had a peak acceleration of about 0.5 g, and the total energy was very close to the absolute maximum earthquake energy possible on earth. As it is, nuclear plants already have numerous redundant top-up systems designed to cope with pipe-breaks of various sizes. The difficulty has been making them passive, and most designs have only relatively limited passive top-up capability - hence, there are valves on every pipe, which can be closed if needed, and multiple redundant pathways.

Really, the solution is to take far more care if building dangerous plants in earthquake prone areas, to ensure that you have designed for the 'maximum possible' event, not just the maximum in living memory.